Finite element analysis of multilayer DEAP stack-actuators

NASA Astrophysics Data System (ADS)

Kuhring, Stefan; Uhlenbusch, Dominik; Hoffstadt, Thorben; Maas, Jürgen

2015-04-01

Dielectric elastomers (DE) are thin polymer films belonging to the class of electroactive polymers (EAP). They are coated with compliant and conductive electrodes on each side, which make them performing a relative high amount of deformation with considerable force generation under the influence of an electric field. Because the realization of high electric fields with a limited voltage level requests single layer polymer films to be very thin, novel multilayer actuators are utilized to increase the absolute displacement and force. In case of a multilayer stack-actuator, many actuator films are mechanically stacked in series and electrically connected in parallel. Because there are different ways to design such a stack-actuator, this contribution considers an optimization of some design parameters using the finite element analysis (FEA), whereby the behavior and the actuation of a multilayer dielectric electroactive polymer (DEAP) stack-actuator can be improved. To describe the material behavior, first different material models are compared and necessary material parameters are identified by experiments. Furthermore, a FEA model of a DEAP film is presented, which is expanded to a multilayer DEAP stack-actuator model. Finally, the results of the FEA are discussed and conclusions for design rules of optimized stack-actuators are outlined.

Colossal dielectric and electromechanical responses in self-assembled polymeric nanocomposites

NASA Astrophysics Data System (ADS)

Huang, Cheng; Zhang, Q. M.; Li, Jiang Yu; Rabeony, Manese

2005-10-01

An electroactive polymer nanocomposite, in which high dielectric constant copper phthalocyanine oligomer (o-CuPc) nanoparticles are incorporated into the block polyurethane (PU) matrix by the combination of "top down" and "bottom up" approaches, was realized. Such an approach enables the nanocomposite to exhibit colossal dielectric and electromechanical responses with very low volume fraction of the high dielectric constant o-CuPc nanofillers (˜3.5%) in the composite. In contrast, a simple blend of o-CuPc and PU composite with much higher o-CuPc content (˜16% of o-CuPc) shows much lower dielectric and electromechanical responses.

Electroactive polymers for gaining sea power

NASA Astrophysics Data System (ADS)

Scherber, Benedikt; Grauer, Matthias; Köllnberger, Andreas

2013-04-01

Target of this article will be the energy harvesting with dielectric elastomers for wave energy conversion. The main goal of this article is to introduce a new developed material profile enabling a specific amount of energy, making the harvesting process competitive against other existing offshore generation technologies. Electroactive polymers offer the chance to start with small wave energy converters to gain experiences and carry out a similar development as wind energy. Meanwhile there is a consortium being formed in Germany to develop such materials and processes for future products in this new business area. In order to demonstrate the applicability of the technological advancements, a scale demonstrator of a wave energy generator will be developed as well.

Cluster synthesis of monodisperse rutile-TiO2 nanoparticles and dielectric TiO2-vinylidene fluoride oligomer nanocomposites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balasubramanian, B; Kraemer, KL; Valloppilly, SR

2011-09-13

The embedding of oxide nanoparticles in polymer matrices produces a greatly enhanced dielectric response by combining the high dielectric strength and low loss of suitable host polymers with the high electric polarizability of nanoparticles. The fabrication of oxide-polymer nanocomposites with well-controlled distributions of nanoparticles is, however, challenging due to the thermodynamic and kinetic barriers between the polymer matrix and nanoparticle fillers. In the present study, monodisperse TiO2 nanoparticles having an average particle size of 14.4 nm and predominant rutile phase were produced using a cluster-deposition technique without high-temperature thermal annealing and subsequently coated with uniform vinylidene fluoride oligomer (VDFO) moleculesmore » using a thermal evaporation source, prior to deposition as TiO2-VDFO nanocomposite films on suitable substrates. The molecular coatings on TiO2 nanoparticles serve two purposes, namely to prevent the TiO2 nanoparticles from contacting each other and to couple the nanoparticle polarization to the matrix. Parallel-plate capacitors made of TiO2-VDFO nanocomposite film as the dielectric exhibit minimum dielectric dispersion and low dielectric loss. Dielectric measurements also show an enhanced effective dielectric constant in TiO2-VDFO nanocomposites as compared to that of pure VDFO. This study demonstrates for the first time a unique electroactive particle coating in the form of a ferroelectric VDFO that has high-temperature stability as compared to conventionally used polymers for fabricating dielectric oxide-polymer nanocomposites.« less

An all-organic composite actuator material with a high dielectric constant.

PubMed

Zhang, Q M; Li, Hengfeng; Poh, Martin; Xia, Feng; Cheng, Z-Y; Xu, Haisheng; Huang, Cheng

2002-09-19

Electroactive polymers (EAPs) can behave as actuators, changing their shape in response to electrical stimulation. EAPs that are controlled by external electric fields--referred to here as field-type EAPs--include ferroelectric polymers, electrostrictive polymers, dielectric elastomers and liquid crystal polymers. Field-type EAPs can exhibit fast response speeds, low hysteresis and strain levels far above those of traditional piezoelectric materials, with elastic energy densities even higher than those of piezoceramics. However, these polymers also require a high field (>70 V micro m(-1)) to generate such high elastic energy densities (>0.1 J cm(-3); refs 4, 5, 9, 10). Here we report a new class of all-organic field-type EAP composites, which can exhibit high elastic energy densities induced by an electric field of only 13 V micro m(-1). The composites are fabricated from an organic filler material possessing very high dielectric constant dispersed in an electrostrictive polymer matrix. The composites can exhibit high net dielectric constants while retaining the flexibility of the matrix. These all-organic actuators could find applications as artificial muscles, 'smart skins' for drag reduction, and in microfluidic systems for drug delivery.

Polymer-based actuators for virtual reality devices

NASA Astrophysics Data System (ADS)

Bolzmacher, Christian; Hafez, Moustapha; Benali Khoudja, Mohamed; Bernardoni, Paul; Dubowsky, Steven

2004-07-01

Virtual Reality (VR) is gaining more importance in our society. For many years, VR has been limited to the entertainment applications. Today, practical applications such as training and prototyping find a promising future in VR. Therefore there is an increasing demand for low-cost, lightweight haptic devices in virtual reality (VR) environment. Electroactive polymers seem to be a potential actuation technology that could satisfy these requirements. Dielectric polymers developed the past few years have shown large displacements (more than 300%). This feature makes them quite interesting for integration in haptic devices due to their muscle-like behaviour. Polymer actuators are flexible and lightweight as compared to traditional actuators. Using stacks with several layers of elatomeric film increase the force without limiting the output displacement. The paper discusses some design methods for a linear dielectric polymer actuator for VR devices. Experimental results of the actuator performance is presented.

Designing components using smartMOVE electroactive polymer technology

NASA Astrophysics Data System (ADS)

Rosenthal, Marcus; Weaber, Chris; Polyakov, Ilya; Zarrabi, Al; Gise, Peter

2008-03-01

Designing components using SmartMOVE TM electroactive polymer technology requires an understanding of the basic operation principles and the necessary design tools for integration into actuator, sensor and energy generation applications. Artificial Muscle, Inc. is collaborating with OEMs to develop customized solutions for their applications using smartMOVE. SmartMOVE is an advanced and elegant way to obtain almost any kind of movement using dielectric elastomer electroactive polymers. Integration of this technology offers the unique capability to create highly precise and customized motion for devices and systems that require actuation. Applications of SmartMOVE include linear actuators for medical, consumer and industrial applications, such as pumps, valves, optical or haptic devices. This paper will present design guidelines for selecting a smartMOVE actuator design to match the stroke, force, power, size, speed, environmental and reliability requirements for a range of applications. Power supply and controller design and selection will also be introduced. An overview of some of the most versatile configuration options will be presented with performance comparisons. A case example will include the selection, optimization, and performance overview of a smartMOVE actuator for the cell phone camera auto-focus and proportional valve applications.

Optimized energy harvesting materials and generator design

NASA Astrophysics Data System (ADS)

Graf, Christian; Hitzbleck, Julia; Feller, Torsten; Clauberg, Karin; Wagner, Joachim; Krause, Jens; Maas, Jürgen

2013-04-01

Electroactive polymers are soft capacitors made of thin elastic and electrically insulating films coated with compliant electrodes offering a large amount of deformation. They can either be used as actuators by applying an electric charge or they can be used as energy converters based on the electrostatic principle. These unique properties enable the industrial development of highly efficient and environmentally sustainable energy converters, which opens up the possibility to further exploit large renewable and inexhaustible energy sources like wind and water that are widely unused otherwise. Compared to other electroactive polymer materials, polyurethanes, whose formulations have been systematically modified and optimized for energy harvesting applications, have certain advantages over silicones and acrylates. The inherently higher dipole content results in a significantly increased permittivity and the dielectric breakdown strength is higher, too, whereby the overall specific energy, a measure for the energy gain, is better by at least factor ten, i.e. more than ten times the energy can be gained out of the same amount of material. In order to reduce conduction losses on the electrode during charging and discharging, a highly conductive bidirectional stretchable electrode has been developed. Other important material parameters like stiffness and bulk resistivity have been optimized to fit the requirements. To realize high power energy harvesting systems, substantial amounts of electroactive polymer material are necessary as well as a smart mechanical and electrical design of the generator. In here we report on different measures to evaluate and improve electroactive polymer materials for energy harvesting by e.g. reducing the defect occurrence and improving the electrode behavior.

Composite-Based High Performance Electroactive Polymers For Remotely Controlled Mechanical Manipulations in NASA Applications

NASA Technical Reports Server (NTRS)

Zhang, Q. M.

2003-01-01

This program supported investigation of an all-polymer percolative composite which exhibits very high dielectric constant (less than 7,000). The experimental results show that the dielectric behavior of this new class of percolative composites follows the prediction of the percolation theory and the analysis of the conductive percolation phenomena. The very high dielectric constant of the all-polymer composites which are also very flexible and possess elastic modulus not very much different from that of the insulation polymer matrix makes it possible to induce a high electromechanical response under a much reduced electric field (a strain of 2.65% with an elastic energy density of 0.18 J/cu cm can be achieved under a field of 16 MV/m). Data analysis also suggests that in these composites, the non-uniform local field distribution as well as interface effects can significantly enhance the strain responses. Furthermore, the experimental data as well as the data analysis indicate that the conduction loss in these composites will not affect the strain hysteresis.

Development of Polythiophene/Acrylonitrile-Butadiene Rubbers for Artificial Muscle

NASA Astrophysics Data System (ADS)

Thipdech, Pacharavalee; Sirivat, Anuvat

2007-03-01

Electroactive polymers (EAPs) can respond to the applied electrical field by an extension or a retraction. In this work, we are interested in using an elastomeric blend for electroactive applications, acrylonitirle-butadiene rubber (NBR) containing a conductive polymer (Poly(3-thiopheneacetic acid, PTAA); the latter can be synthesized via oxidative polymerization. FT-IR, Thermogravimetric analysis (TGA), ^1H-NMR, UV-visible spectroscopy, and SEM are used to characterize the conductive polymer. Electrorheological properties are measured and investigated in terms of acrylonitrile content, blending ratio, doping level, and temperature. Experiments are carried out under oscillatory shear mode and with applied electric field strength varying from 0 to 2 kV/mm. Dielectric properties, conductivities are measured and correlated with the storage modulus responses. The storage modulus sensitivity, δG'G'0of the pure rubbers increases with increasing electric field strength. They attain the maximum values of about 30% and become constant at electric strength at and above 1000 V/mm.

Molecular mobility, morphology, and ion conduction in ionomers for electroactive devices

NASA Astrophysics Data System (ADS)

Tudryn, Gregory J.

A sequential study of ion-containing polymers capable of ion solvation with varied ion content, dielectric constant, and counterions is presented in this dissertation in order to compare ion transport properties in ionomers with various ionic interactions. Structure-property relationships in these ion containing polymers are defined using x-ray scattering, rheology and dielectric spectroscopy, enabling the quantification of ion transport dynamics. Poly(ethylene oxide), (PEO) based ionomers are investigated in order to probe the relation between ion conduction and segmental relaxation, and copolymers of PEO and Poly(tetramethylene oxide), (PTMO) further develop an understanding of the trade-off between ion solvation and segmental dynamics. Ionomers with ionic liquid counterions probe diffuse charge interactions and steric effects on ion transport, and incorporation of ionic liquids into ionomer membranes such as Nafion provides desirable thermal and ion conducting properties which extend the use of such membranes for electroactive devices. PEO ionomers exhibit a strong relation between ionic conductivity and segmental dynamics, providing insight that the glass transition temperature, Tg, dominates the ion conduction mechanism. Increasing temperature induces aggregation of ionic groups as evidenced by the static dielectric constant and X-ray scattering as a function of temperature, revealing the contribution of ionic dipoles in the measured dielectric constant. The trade-off between ion solvation and fast polymer segmental dynamics are quantified in copolymer ionomers of PEO and lower Tg PTMO. While conducting ion content remains nearly unchanged, conductivity is lowered upon incorporation of PTMO, because the vast majority of the PTMO microphase separates from the PEO-rich microdomain that remains continuous and contributes most of the ion conduction. Dielectric constants and X-ray scattering show consistent changes with temperature that suggest a cascading aggregation process in Na ionomers as ionic dipoles thermally randomize and lower the measured dielectric constant of the medium, leading to further aggregation. We observe amplified microphase-separation through ionic groups preferentially solvated by PEO chains, as seen in block copolymers with added salt. Even at 25%PEO / 75%PTMO the ionomers have VFT temperature dependence of conducting ion mobility, meaning that the 25% PEO/ion microphase is still continuous A model is developed to describe the frequency dependent storage and loss modulus and the delay in Rouse motion due to ion association lifetime, as functions of ion content and molecular weight for our low molecular weight ionomers. The ion rearrangement relaxation in dielectric spectroscopy is clearly the ion association lifetime that controls terminal dynamics in linear viscoelasticity, allowing a simple sticky Rouse model, using the most-probable distribution based on NMR Mn, to fully describe master curves of the frequency dependent storage and loss modulus. Using insight from ionic interaction strength, ionic liquids are used as counterions, effectively plasticizing the ionomers without added solvent. Ionic interactions were weakened with increasing counterion size, and with modification of cations using ether-oxygen, promoting self-solvation, which increases conducting ion density by an order of magnitude. Room temperature ionic liquids were subsequently used in combination with NafionRTM membranes as electroactive substrates to correlate ion transport to morphology as a function of volume fraction of ionic liquid. This study illuminated the critical volume uptake of ionic liquid in Nafion, identifying percolation of ionic pathways and a significant increase in dielectric constant at low frequencies, indicating an increase in the number density of ions capable of polarizing at the electrode surface. Consequently, the fundamental information obtained about the structure-property relations of ionomers can be used to predict and design advanced ion-containing polymers to be used in battery membranes and a variety of electroactive devices, including actuators and electromechanical sensors.

Polymeric blends for sensor and actuation dual functionality

NASA Technical Reports Server (NTRS)

St. Clair, Terry L. (Inventor); Harrison, Joycelyn S. (Inventor); Su, Ji (Inventor); Ounaies, Zoubeida (Inventor)

2004-01-01

The invention described herein supplies a new class of electroactive polymeric blend materials which offer both sensing and actuation dual functionality. The blend comprises two components, one component having a sensing capability and the other component having an actuating capability. These components should be co-processable and coexisting in a phase separated blend system. Specifically, the materials are blends of a sensing component selected from the group consisting of ferroelectric, piezoelectric, pyroelectric and photoelectric polymers and an actuating component that responds to an electric field in terms of dimensional change. Said actuating component includes, but is not limited to, electrostrictive graft elastomers, dielectric electroactive elastomers, liquid crystal electroactive elastomers and field responsive polymeric gels. The sensor functionality and actuation functionality are designed by tailoring the relative fraction of the two components. The temperature dependence of the piezoelectric response and the mechanical toughness of the dual functional blends are also tailored by the composition adjustment.

Bio-kinetic energy harvesting using electroactive polymers

NASA Astrophysics Data System (ADS)

Slade, Jeremiah R.; Bowman, Jeremy; Kornbluh, Roy

2012-06-01

In hybrid vehicles, electric motors are used on each wheel to not only propel the car but also to decelerate the car by acting as generators. In the case of the human body, muscles spend about half of their time acting as a brake, absorbing energy, or doing what is known as negative work. Using dielectric elastomers it is possible to use the "braking" phases of walking to generate power without restricting or fatiguing the Warfighter. Infoscitex and SRI have developed and demonstrated methods for using electroactive polymers (EAPs) to tap into the negative work generated at the knee during the deceleration phase of the human gait cycle and convert it into electrical power that can be used to support wearable information systems, including display and communication technologies. The specific class of EAP that has been selected for these applications is termed dielectric elastomers. Because dielectric elastomers dissipate very little mechanical energy into heat, greater amounts of energy can be converted into electricity than by any other method. The long term vision of this concept is to have EAP energy harvesting cells located in components of the Warfighter ensemble, such as the boot uppers, knee pads and eventually even the clothing itself. By properly locating EAPs at these sites it will be possible to not only harvest power from the negative work phase but to actually reduce the amount of work done by the Warfighter's muscles during this phase, thereby reducing fatigue and minimizing the forces transmitted to the joints.

State-of-the-art developments in the field of electroactive polymers

NASA Technical Reports Server (NTRS)

Vinogradov, Aleksandra; Su, Ji; Jenkins, Christopher; Bar-Cohen, Yoseph

2005-01-01

The paper presents a brief review in the field of electroactive polymers. it outlines the main classes of electroactive polymers, their properties and applications. Current efforts to synthesize electroactive polymers with novel or improved characteristics along with the challenges, opportunities and future research directions in the subject area are discussed.

Experimental assessment of spanwise-oscillating dielectric electroactive surfaces for turbulent drag reduction in an air channel flow

NASA Astrophysics Data System (ADS)

Gatti, Davide; Güttler, Andreas; Frohnapfel, Bettina; Tropea, Cameron

2015-05-01

In the present work, wall oscillations for turbulent skin friction drag reduction are realized in an air turbulent duct flow by means of spanwise-oscillating active surfaces based on dielectric electroactive polymers. The actuator system produces spanwise wall velocity oscillations of 820 mm/s semi-amplitude at its resonance frequency of 65 Hz while consuming an active power of a few 100 mW. The actuators achieved a maximum integral drag reduction of 2.4 %. The maximum net power saving, budget of the power benefit and cost of the control, was measured for the first time with wall oscillations. Though negative, the net power saving is order of magnitudes higher than what has been estimated in previous studies. Two new direct numerical simulations of turbulent channel flow show that the finite size of the actuator only partially explains the lower values of integral drag reduction typically achieved in laboratory experiments compared to numerical simulations.

Hysteresis modeling and identification of a dielectric electro-active polymer actuator using an APSO-based nonlinear Preisach NARX fuzzy model

NASA Astrophysics Data System (ADS)

Truong, Bui Ngoc Minh; Nam, Doan Ngoc Chi; Ahn, Kyoung Kwan

2013-09-01

Dielectric electro-active polymer (DEAP) materials are attractive since they are low cost, lightweight and have a large deformation capability. They have no operating noise, very low electric power consumption and higher performance and efficiency than competing technologies. However, DEAP materials generally have strong hysteresis as well as uncertain and nonlinear characteristics. These disadvantages can limit the efficiency in the use of DEAP materials. To address these limitations, this research will present the combination of the Preisach model and the dynamic nonlinear autoregressive exogenous (NARX) fuzzy model-based adaptive particle swarm optimization (APSO) identification algorithm for modeling and identification of the nonlinear behavior of one typical type of DEAP actuator. Firstly, open loop input signals are applied to obtain nonlinear features and to investigate the responses of the DEAP actuator system. Then, a Preisach model can be combined with a dynamic NARX fuzzy structure to estimate the tip displacement of a DEAP actuator. To optimize all unknown parameters of the designed combination, an identification scheme based on a least squares method and an APSO algorithm is carried out. Finally, experimental validation research is carefully completed, and the effectiveness of the proposed model is evaluated by employing various input signals.

All-Organic Actuator Fabricated with Single Wall Carbon Nanotube Electrodes

NASA Technical Reports Server (NTRS)

Lowther, Sharon E.; Harrison, Joycelyn S.; Kang, Jinho; Park, Cheol; Park, Chan Eon

2008-01-01

Compliant electrodes to replace conventional metal electrodes have been required for many actuators to relieve the constraint on the electroactive layer. Many conducting polymers have been proposed for the alternative electrodes, but they still have a problem of poor thermal stability. This article reports a novel all-organic actuator with single wall carbon nanotube (SWCNT) films as the alternative electrode. The SWCNT film was obtained by filtering a SWCNT solution through an anodized alumina membrane. The conductivity of the SWCNT film was about 280 S/cm. The performance of the SWCNT film electrode was characterized by measuring the dielectric properties of NASA Langley Research Center - Electroactive Polymer (LaRC-EAP) sandwiched by the SWCNT electrodes over a broad range of temperature (from 25 C to 280 C) and frequency (from 1 KHz to 1 MHz). The all-organic actuator with the SWCNT electrodes showed a larger electric field-induced strain than that with metal electrodes, under identical measurement conditions.

Electroactive poly(vinylidene fluoride)-based structures for advanced applications.

PubMed

Ribeiro, Clarisse; Costa, Carlos M; Correia, Daniela M; Nunes-Pereira, João; Oliveira, Juliana; Martins, Pedro; Gonçalves, Renato; Cardoso, Vanessa F; Lanceros-Méndez, Senentxu

2018-04-01

Poly(vinylidene fluoride) (PVDF) and its copolymers are the polymers with the highest dielectric constants and electroactive responses, including piezoelectric, pyroelectric and ferroelectric effects. This semicrystalline polymer can crystallize in five different forms, each related to a different chain conformation. Of these different phases, the β phase is the one with the highest dipolar moment and the highest piezoelectric response; therefore, it is the most interesting for a diverse range of applications. Thus, a variety of processing methods have been developed to induce the formation of the polymer β phase. In addition, PVDF has the advantage of being easily processable, flexible and low-cost. In this protocol, we present a number of reproducible and effective methods to produce β-PVDF-based morphologies/structures in the form of dense films, porous films, 3D scaffolds, patterned structures, fibers and spheres. These structures can be fabricated by different processing techniques, including doctor blade, spin coating, printing technologies, non-solvent-induced phase separation (NIPS), temperature-induced phase separation (TIPS), solvent-casting particulate leaching, solvent-casting using a 3D nylon template, freeze extraction with a 3D poly(vinyl alcohol) (PVA) template, replica molding, and electrospinning or electrospray, with the fabrication method depending on the desired characteristics of the structure. The developed electroactive structures have shown potential to be used in a wide range of applications, including the formation of sensors and actuators, in biomedicine, for energy generation and storage, and as filtration membranes.

High-Force Dielectric Electroactive Polymer (DEAP) membrane actuator

NASA Astrophysics Data System (ADS)

Hau, Steffen; York, Alexander; Seelecke, Stefan

2016-04-01

Energy efficiency, lightweight and scalability are key features for actuators in applications such as valves, pumps or any portable system. Dielectric electroactive Polymer (DEAP) technology is able to fulfill these requirements1 better than commonly used technology e.g. solenoids, but has limitations concerning force and stroke. However, the circular DEAP membrane actuator shows a potential increase in stroke in the mm range, when combined with an appropriate biasing mechanism2. Although, thus far, their force range is limited to the single-digit Newton range, or less3,4. This work describes how this force limit of DEAP membrane actuators can be pushed to the high double-digit Newton range and beyond. The concept for such an actuator consists of a stack of double-layered DEAPs membrane actuator combined with a biasing mechanism. These two components are combined in a novel way, which allows a compact design by integrating the biasing mechanism into the DEAP membrane actuator stack. Subsequently, the single components are manufactured, tested, and their force-displacement characteristic is documented. Utilizing this data allows assembling them into actuator systems for different applications. Two different actuators are assembled and tested (dimensions: 85x85x30mm3 (LxWxH)). The first one is able to lift 7.5kg. The second one can generate a force of 66N while acting against a spring load.

Micro- and nanostructured electro-active polymer actuators as smart muscles for incontinence treatment

NASA Astrophysics Data System (ADS)

Osmani, Bekim; Töpper, Tino; Deschenaux, Christian; Nohava, Jiri; Weiss, Florian M.; Leung, Vanessa; Müller, Bert

2015-02-01

Treatments of severe incontinence are currently based on purely mechanical systems that generally result in revision after three to five years. Our goal is to develop a prototype acting in a natural-analogue manner as artificial muscle, which is based on electro-active polymers. Dielectric actuators have outstanding performances including millisecond response times, mechanical strains of more than 10 % and power to mass densities similar to natural muscles. They basically consist of polymer films sandwiched between two compliant electrodes. The incompressible but elastic polymer film transduces the electrical energy into mechanical work according to the Maxwell pressure. Available polymer films are micrometers thick and voltages as large as kV are necessary to obtain 10 % strain. For medical implants, polymer films should be nanometer thin to realize actuation below 48 V. The metallic electrodes have to be stretchable to follow the strain of 10 % and remain conductive. Recent results on the stress/strain behavior of anisotropic EAP-cantilevers have shown dependencies on metal electrode preparation. We have investigated tunable anisotropic micro- and nanostructures for metallic electrodes. They show a preferred actuation direction with improved stress-strain behavior. The bending of the cantilever has been characterized by the laser beam deflection method. The impact of the electrode on the effective Young's Modulus is measured using an Ultra Nanoindentation Tester with an integrated reference system for soft polymer surfaces. Once ten thousand layers of nanometer-thin EAP actuators are available, devices beyond the envisioned application will flood the market.

Optimized Electroactive Polymer Supercapacitors

DTIC Science & Technology

2014-09-08

Final 03/01/2012-05/15/2014 4. TITLE AND SUBTITLE Sa. CONTRACT NUMBER OPTIMIZED ELECTROACTIVE POLYMER SUPERCAPACITORS NA Sb. GRANT NUMBER N00014-12-1...highly electroactive, conjugated polymers as the active redox materials in electrochemical supercapacitors . Such materials include electrochemically...ethylenedioxythiophene) (PEDOT) for Type I or Type II supercapacitors , along with donor-acceptor-donor (D-A-D) polymers which provide reductive states for Type

Structural health monitoring system/method using electroactive polymer fibers

NASA Technical Reports Server (NTRS)

Scott-Carnell, Lisa A. (Inventor); Siochi, Emilie J. (Inventor)

2013-01-01

A method for monitoring the structural health of a structure of interest by coupling one or more electroactive polymer fibers to the structure and monitoring the electroactive responses of the polymer fiber(s). Load changes that are experienced by the structure cause changes in the baseline responses of the polymer fiber(s). A system for monitoring the structural health of the structure is also provided.

Online identification algorithms for integrated dielectric electroactive polymer sensors and self-sensing concepts

NASA Astrophysics Data System (ADS)

Hoffstadt, Thorben; Griese, Martin; Maas, Jürgen

2014-10-01

Transducers based on dielectric electroactive polymers (DEAP) use electrostatic pressure to convert electric energy into strain energy or vice versa. Besides this, they are also designed for sensor applications in monitoring the actual stretch state on the basis of the deformation dependent capacitive-resistive behavior of the DEAP. In order to enable an efficient and proper closed loop control operation of these transducers, e.g. in positioning or energy harvesting applications, on the one hand, sensors based on DEAP material can be integrated into the transducers and evaluated externally, and on the other hand, the transducer itself can be used as a sensor, also in terms of self-sensing. For this purpose the characteristic electrical behavior of the transducer has to be evaluated in order to determine the mechanical state. Also, adequate online identification algorithms with sufficient accuracy and dynamics are required, independent from the sensor concept utilized, in order to determine the electrical DEAP parameters in real time. Therefore, in this contribution, algorithms are developed in the frequency domain for identifications of the capacitance as well as the electrode and polymer resistance of a DEAP, which are validated by measurements. These algorithms are designed for self-sensing applications, especially if the power electronics utilized is operated at a constant switching frequency, and parasitic harmonic oscillations are induced besides the desired DC value. These oscillations can be used for the online identification, so an additional superimposed excitation is no longer necessary. For this purpose a dual active bridge (DAB) is introduced to drive the DEAP transducer. The capabilities of the real-time identification algorithm in combination with the DAB are presented in detail and discussed, finally.

Micro- and nanostructured electro-active polymer actuators as smart muscles for incontinence treatment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Osmani, Bekim, E-mail: bekim.osmani@unibas.ch, E-mail: tino.toepper@unibas.ch; Töpper, Tino, E-mail: bekim.osmani@unibas.ch, E-mail: tino.toepper@unibas.ch; Weiss, Florian M., E-mail: vanessa.leung@unibas.ch, E-mail: bert.mueller@unibas.ch

2015-02-17

Treatments of severe incontinence are currently based on purely mechanical systems that generally result in revision after three to five years. Our goal is to develop a prototype acting in a natural-analogue manner as artificial muscle, which is based on electro-active polymers. Dielectric actuators have outstanding performances including millisecond response times, mechanical strains of more than 10 % and power to mass densities similar to natural muscles. They basically consist of polymer films sandwiched between two compliant electrodes. The incompressible but elastic polymer film transduces the electrical energy into mechanical work according to the Maxwell pressure. Available polymer films aremore » micrometers thick and voltages as large as kV are necessary to obtain 10 % strain. For medical implants, polymer films should be nanometer thin to realize actuation below 48 V. The metallic electrodes have to be stretchable to follow the strain of 10 % and remain conductive. Recent results on the stress/strain behavior of anisotropic EAP-cantilevers have shown dependencies on metal electrode preparation. We have investigated tunable anisotropic micro- and nanostructures for metallic electrodes. They show a preferred actuation direction with improved stress-strain behavior. The bending of the cantilever has been characterized by the laser beam deflection method. The impact of the electrode on the effective Young's Modulus is measured using an Ultra Nanoindentation Tester with an integrated reference system for soft polymer surfaces. Once ten thousand layers of nanometer-thin EAP actuators are available, devices beyond the envisioned application will flood the market.« less

Effect of carbon nanofillers on the microstructure and electromechanical properties of electroactive polymers

NASA Astrophysics Data System (ADS)

Sigamani, Nirmal Shankar

Both ionic and electronic electroactive polymers (EAPs) have displayed great potential as actuators. Current ionic EAPs have limited practical application due to their slow response time and their low blocked force; furthermore, their ion transport-based mechanism necessitates the presence of an electrolyte, which complicates issues of packaging and device lifetime. On the other hand, despite the advantages of electronic EAPs such as their efficient electromechanical coupling and relatively rapid response time, there are major obstacles blocking their transition to application as well; most notably, they require high actuation voltages (threshold voltage needed to generate electroactive strain) and they have low blocked stress (the stress at which the actuator stops moving). Hence, the main objective of this study was to develop a new kind of polymer nanocomposite for actuator applications that would exhibit simultaneous improvement in both electromechanical response and strain energy density. As a first step, we investigated the impact of the 2-dimensional GO and reduced GO on the electromechanical response of PVDF, a polar polymer. The 1 wt % reduced-GO-PVDF nanocomposites showed a tremendous improvement in dielectric permittivity and electrical conductivity. The dielectric permittivity at 1 KHz increased almost eight fold, while the electrical conductivity showed an increase of four orders of magnitude in comparison to the corresponding values for the unmodified PVDF. The reduced GO-PVDF polymer films showed a bending actuation response with a DC electric field, thus demonstrating its potential as EAP. The mechanism responsible for this bending actuation response is determined to be electrostriction, because the strain (S11) exhibited a quadratic response with the applied electric field while Joule heating and Maxwell stress effects were shown to be negligible. Although coefficient of electrostriction of reduced GO-PVDF is higher than most of the existing electroactive polymers, the relatively high electrical conductivity and low breakdown limits their use for practical applications. So next step was to exploit the advantages of a conductive carbon nanostructure while controlling its network to better impact its electrical properties which could also lead to higher breakdown strength. Based on the promising impact of hybrid nanofillers on the ferroelectric polymer PVDF, a similar polymer with a relaxor ferroelectric character is considered owing to its higher inherent electroactive response and higher breakdown strength. Given that it is not broadly studied, there was a need to understand structure-property relationship of the PVDF TrFE CTFE terpolymer. Hence, the effect of processing conditions (such as annealing times and isothermal crystallization temperatures) on the microstructure and the subsequent electromechanical properties were analyzed. This structure-property analysis helped to understand the relation between the different types of crystalline phases and the degrees of crystallinity as well as to observe crystal sizes as they relate to the electric field induced strain. As a final step, the effect of the hybrid SWNT/GO on both microstructure and electromechanical properties of the terpolymer were studied. The hybrid nanofillers were chemically modified to form a covalent bond between them to improve their interaction. The morphology of the hybrid nanofillers after the chemical modification was studied for two different chemical modification routes: one using thionyl chloride, other using NHS and EDAC as catalysts. Of the two methods, the NHS and EDAC catalyst method showed a strong uniform interaction, confirmed by SEM images and FTIR results, with a shift in the peak to 1630 cm-1. Finally, the effect of hybrid SWNT and GO on the electromechanical properties were studied and, interestingly, the hybrid terpolymer nanocomposite film showed a lower electroactive strain compared to pure terpolymer at the same applied electric field. WAXS and DSC results suggest that this reduction is partly due to the change in the crystallinity and to the SWNT hindrance effect on the crystalline phase transformation which is responsible for the electroactive strain. In this dissertation, it was successfully shown that using hybrid SWNT-GO both high coefficient of electrostriction (increase by 60 %) and high breakdown strength (140 MV/m) can be achieved by exploiting the actuation capabilities of SWNT in PVDF while GO acted as insulative filler. Also, the type of the fillers in the nanocomposites route had a strong influence on the actuation mechanism of relaxor ferroelectric polymers. The microstructure-property study highlights the importance of choosing the right type of nanofillers for further advancement in the field of EAPs. (Abstract shortened by UMI.).

Polymer-Ceramic Composite Materials for Pyroelectric Infrared Detectors: An Overview

NASA Technical Reports Server (NTRS)

Aggarwal, M. D; Currie, J. R.; Penn, B. G.; Batra, A. K.; Lal, R. B.

2007-01-01

Ferroelectrics:Polymer composites can be considered an established substitute for conventional electroceramics and ferroelectric polymers. The composites have a unique blend of polymeric properties such as mechanical flexibility, high strength, formability, and low cost, with the high electro-active properties of ceramic materials. They have attracted considerable interest because of their potential use in pyroelectric infrared detecting devices and piezoelectric transducers. These flexible sensors and transducers may eventually be useful for their health monitoring applications for NASA crew launch vehicles and crew exploration vehicles being developed. In the light of many technologically important applications in this field, it is worthwhile to present an overview of the pyroelectric infrared detector theory, models to predict dielectric behavior and pyroelectric coefficient, and the concept of connectivity and fabrication techniques of biphasic composites. An elaborate review of Pyroelectric-Polymer composite materials investigated to date for their potential use in pyroelectric infrared detectors is presented.

Electroactive Polymer (EAP) Actuation of Mechanisms and Robotic Devices

NASA Technical Reports Server (NTRS)

Bar-Cohen, Y.; Leary, S.; Harrison, J.; Smith, J.

1999-01-01

Actuators are responsible to the operative capability of manipulation systems and robots. In recent years, electroactive polymers (EAP) have emerged as potential alternative to conventional actuators.

Method of Making an Electroactive Sensing/Actuating Material for Carbon Nanotube Polymer Composite

NASA Technical Reports Server (NTRS)

Ounaies, Zoubeida (Inventor); Park, Cheol (Inventor); Harrison, Joycelyn S. (Inventor); Holloway, Nancy M. (Inventor); Draughon, Gregory K. (Inventor)

2009-01-01

An electroactive sensing or actuating material comprises a composite made from a polymer with polarizable moieties and an effective amount of carbon nanotubes incorporated in the polymer for a predetermined electromechanical operation of the composite when such composite is affected by an external stimulus. In another embodiment, the composite comprises a, third component of micro -sized to nano-sized particles of an electroactive ceramic that is also incorporated in the polymer matrix. The method for making the three-phase composite comprises either incorporating the carbon nanotubes in the polymer matrix before incorporation of the particles of ceramic or mixing the carbon nanotubes and particles of ceramic together in a solution before incorporation in the polymer matrix.

Inflated dielectric elastomer actuator for eyeball's movements: fabrication, analysis and experiments

NASA Astrophysics Data System (ADS)

Liu, Yanju; Shi, Liang; Liu, Liwu; Zhang, Zhen; Leng, Jinsong

2008-03-01

Bio-mimetic actuators are inspired to the human or animal organ and they are aimed at replicating actions exerted by the main organic muscles. We present here an inflated dielectric Electroactive Polymer actuator based on acrylic elastomer aiming at mimicing the ocular muscular of the human eye. Two sheets of polyacrylic elastomer coated with conductive carbon grease are sticked to a rotatable backbone, which function like an agonist-antagonist configuration. When stimulating the two elastomer sheets separately, the rotatable mid-arc of the actuator is capable of rotating from -50° to 50°. Experiments shows that the inflated actuator, compared with uninflated one, performs much bigger rotating angle and more strengthened. Connected with the actuator via an elastic tensive line, the eyeball rotates around the symmetrical axes. The realization of more accurate movements and emotional expressions of our native eye system is the next step of our research and still under studied. This inflated dielectric elastomer actuator shows as well great potential application in robofish and adaptive stucture.

96X Screen-Printed Gold Electrode Platform to Evaluate Electroactive Polymers as Marine Antifouling Coatings.

PubMed

Brisset, Hugues; Briand, Jean-François; Barry-Martinet, Raphaëlle; Duong, The Hy; Frère, Pierre; Gohier, Frédéric; Leriche, Philippe; Bressy, Christine

2018-04-17

Several alternatives are currently investigated to prevent and control the natural process of colonization of any seawater submerged surfaces by marine organisms. Since few years we develop an approach based on addressable electroactive coatings containing conducting polymers or polymers with lateral redox groups. In this article we describe the use of a screen-printed plate formed by 96 three-electrode electrochemical cells to assess the potential of these electroactive coatings to prevent the adhesion of marine bacteria. This novel platform is intended to control and record the redox properties of the electroactive coating in each well during the bioassay (15 h) and to allow screening its antiadhesion activity with enough replicates to support significant conclusions. Validation of this platform was carried out with poly(ethylenedioxythiophene) (PEDOT) as electroactive coating obtained by electropolymerization of EDOT monomer in artificial seawater electrolyte on the working electrode of each electrochemical cell of the 96-well microplate.

High-dielectric-constant polymers as high-energy-density (HED) field effect actuator and capacitor materials

NASA Astrophysics Data System (ADS)

Huang, Cheng; Zhang, Qiming

2004-07-01

The development of high dielectric constant polymers as active materials in high-performance devices is one of the challenges in polymeric electronics and opto-electronics such as flexible thin-film capacitors, memory devices and microactuators for deformable micromirror technology. A group of poly(vinylidene fluoridetrifluoroethylene) P(VDF-TrFE) based high-dielectric-constant fluoroterpolymers have been developed, which have high room-temperature dielectric constant (K>60) and very high strain level and high energy density. The longitudinal and transverse strain of these materials can reach about -7% and 4.5%, respectively, and the elastic energy density is around 1.1 J/cm^3 under a high electric field of 150 MV/m. The influence on the electromechanical properties of copolymerizing poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) with a third monomer, chlorofluoroethylene (CFE), was investigated. It was found that increasing the CFE content from 0 to 8.5% slowly converts the ferroelectric structure of the copolymer to a relaxor ferroelectric system. This allows for a greatly decreased polarization and dielectric hysteresis and a much higher strain. Above 8.5%, increased CFE content substantially degrades the bulk crystallinity and the Young's modulus. These terpolymers have the potential to achieve above 10 J/cm^3 whole capacity energy density, which makes them good candidates for applications in pulse power capacitors. An all-polymer percolative composite by the combination of conductive polyaniline particles (K>10^5) within a fluoroterpolymer matrix, is introduced which exhibits very high dielectric constant (>7,000). The experimental results show that the dielectric behavior of this new class of percolative composites follows the prediction of the percolation theory and the analysis of the conductive percolation phenomena. The very high dielectric constant of the all-polymer composites which are also very flexible and possess elastic modulus not very much different from that of the insulation polymer matrix makes it possible to induce a high electromechanical response under a much reduced electric field (a strain of 2.65% with an elastic energy density of 0.18 J/cm^3 can be achieved under a low field of 16 MV/m). Data analysis also suggests that in these composites, the non-uniform local field distribution as well as interface effects can significantly enhance the strain responses. Furthermore, the experimental data as well as the data analysis indicate that the conduction loss in these composites will not affect the strain hysteresis. Flexible high dielectric constant electroactive polymers provide potential applications in high-energy-density (HED) energy storage and conversion systems such as lightweight field effect actuators and capacitors.

Fabrication of multilayered conductive polymer structures via selective visible light photopolymerization

NASA Astrophysics Data System (ADS)

Cullen, Andrew T.; Price, Aaron D.

2017-04-01

Electropolymerization of pyrrole is commonly employed to fabricate intrinsically conductive polymer films that exhibit desirable electromechanical properties. Due to their monolithic nature, electroactive polypyrrole films produced via this process are typically limited to simple linear or bending actuation modes, which has hindered their application in complex actuation tasks. This initiative aims to develop the specialized fabrication methods and polymer formulations required to realize three-dimensional conductive polymer structures capable of more elaborate actuation modes. Our group has previously reported the application of the digital light processing additive manufacturing process for the fabrication of three-dimensional conductive polymer structures using ultraviolet radiation. In this investigation, we further expand upon this initial work and present an improved polymer formulation designed for digital light processing additive manufacturing using visible light. This technology enables the design of novel electroactive polymer sensors and actuators with enhanced capabilities and brings us one step closer to realizing more advanced electroactive polymer enabled devices.

Development of Processible Electroactive Oligomers and Polymers

DTIC Science & Technology

1991-10-01

of structure and electroactive properties. Electroactive molecules including fused ring (ladder oligomers) dyes , squarylium -heterocyclic moieties...Electroactive molecules including fused ring (ladder oligomers) dyes , squarylium -heterocyclic moieties, phenylpolyenes, thienylpolyenes, carbocyanine dyes ...phenylpolyenes, thienylpolyenes, carbocyanine dyes , and tetraazaannulenes have also been synthetically incorporated into a variety of traditional

Highly Efficient Flexible Hybrid Photovoltaic Cells Based on Low-Band-Gap Conjugated Polymers Sensitized by Nanoparticle-Grafted Carbon

DTIC Science & Technology

2010-09-01

modeling, synthesis , and characterization of several series functional and processable electro-active conjugated polymers with evolving frontier...tasks as a basic obligation of this award: Task #1. Low Band Gap Polymers The awardee (Professor Sun’s group at NSU) shall design, synthesis , and...design, modeling, synthesis , and characterizations of several series functional and processable electro-active conjugated polymers with evolving

A viscoelastic model for dielectric elastomers based on a continuum mechanical formulation and its finite element implementation

NASA Astrophysics Data System (ADS)

Bueschel, A.; Klinkel, S.; Wagner, W.

2011-04-01

Smart materials are active and multifunctional materials, which play an important part for sensor and actuator applications. These materials have the potential to transform passive structures into adaptive systems. However, a prerequisite for the design and the optimization of these materials is, that reliable models exist, which incorporate the interaction between the different combinations of thermal, electrical, magnetic, optical and mechanical effects. Polymeric electroelastic materials, so-called electroactive polymer (EAP), own the characteristic to deform if an electric field is applied. EAP's possesses the benefit that they share the characteristic of polymers, these are lightweight, inexpensive, fracture tolerant, elastic, and the chemical and physical structure is well understood. However, the description "electroactive polymer" is a generic term for many kinds of different microscopic mechanisms and polymeric materials. Based on the laws of electromagnetism and elasticity, a visco-electroelastic model is developed and implemented into the finite element method (FEM). The presented three-dimensional solid element has eight nodes and trilinear interpolation functions for the displacement and the electric potential. The continuum mechanics model contains finite deformations, the time dependency and the nearly incompressible behavior of the material. To describe the possible, large time dependent deformations, a finite viscoelastic model with a split of the deformation gradient is used. Thereby the time dependent characteristic of polymeric materials is incorporated through the free energy function. The electromechanical interactions are considered by the electrostatic forces and inside the energy function.

Electromechanical response of silk fibroin hydrogel and conductive polycarbazole/silk fibroin hydrogel composites as actuator material.

PubMed

Srisawasdi, Thanida; Petcharoen, Karat; Sirivat, Anuvat; Jamieson, Alexander M

2015-11-01

Pure silk fibroin (SF) hydrogel and polycarbazole/silk fibroin (SF/PCZ) hydrogels were fabricated by solvent casting technique to evaluate electromechanical responses, dielectric properties, and cantilever deflection properties as functions of electric field strength, SF concentration, glutaraldehyde concentration, and PCZ concentration in the blends. Electromechanical properties were characterized in oscillatory shear mode at electric field strengths ranging from 0 to 600V/mm and at a temperature of 27°C. For both the pristine SF and SF/PCZ hydrogels, the storage modulus response (ΔG') and the storage modulus sensitivity (ΔG'/G'0) increased dramatically with increasing electric field strength. The pristine hydrogel possessed the highest storage modulus sensitivity value of 5.87, a relatively high value when compared with other previously studied electroactive polymers. With the addition of conductive PCZ in SF hydrogel, the storage modulus sensitivity and the relative dielectric constant decreased; the conductive polymer thus provided the softening effect under electric field. In the deflection response, the dielectrophoresis force and deflection distance increased monotonically with electric field strength, where the pure SF hydrogel showed the highest deflection distance and dielectrophoresis force. Copyright © 2015 Elsevier B.V. All rights reserved.

Dielectric Actuation of Polymers

NASA Astrophysics Data System (ADS)

Niu, Xiaofan

Dielectric polymers are widely used in a plurality of applications, such as electrical insulation, dielectric capacitors, and electromechanical actuators. Dielectric polymers with large strain deformations under an electric field are named dielectric elastomers (DE), because of their relative low modulus, high elongation at break, and outstanding resilience. Dielectric elastomer actuators (DEA) are superior to traditional transducers as a muscle-like technology: large strains, high energy densities, high coupling efficiency, quiet operation, and light weight. One focus of this dissertation is on the design of DE materials with high performance and easy processing. UV radiation curing of reactive species is studied as a generic synthesis methodology to provide a platform for material scientists to customize their own DE materials. Oligomers/monomers, crosslinkers, and other additives are mixed and cured at appropriate ratios to control the stress-strain response, suppress electromechanical instability of the resulting polymers, and provide stable actuation strains larger than 100% and energy densities higher than 1 J/g. The processing is largely simplified in the new material system by removal of the prestretching step. Multilayer stack actuators with 11% linear strain are demonstrated in a procedure fully compatible with industrial production. A multifunctional DE derivative material, bistable electroactive polymer (BSEP), is invented enabling repeatable rigid-to-rigid deformation without bulky external structures. Bistable actuation allows the polymer actuator to have two distinct states that can support external load without device failure. Plasticizers are used to lower the glass transition temperature to 45 °C. Interpenetrating polymer network structure is established inside the BSEP to suppress electromechanical instability, providing a breakdown field of 194 MV/m and a stable bistable strain as large as 228% with a 97% strain fixity. The application of BSEP in tactile display is investigated by the prototyping of a large scale refreshable Braille display device. Braille is a critical way for the vision impaired community to learn literacy and improve life quality. Current piezoelectrics-based refreshable Braille display technologies are limited to up to 1 line of Braille text, due to the bulky size of bimorph actuators. Based on the unique actuation feature of BSEP, refreshable Braille display devices up to smartphone-size have been demonstrated by polymer sheet laminates. Dots in the devices can be individually controlled via incorporated field-driven BSEP actuators and Joule heater units. A composite material consisting of silver nanowires (AgNW) embedded in a polymer substrate is brought up as a compliant electrode candidate for BSEP application. The AgNW composite is highly conductive (Rs: 10 Ω/sq) and remains conductive at strains as high as 140% (Rs: <10 3 Ω/sq). The baseline conductivity has only small changes up to 90% strain, which makes it low enough for both field driving and stretchable Joule heating. An out-of-plane bistable area strain up to 68% under Joule heating is achieved.

Postgraduate education on electro-active polymers at Southern Denmark University

NASA Astrophysics Data System (ADS)

Jones, Richard W.

2009-03-01

A recently introduced elective to the Master's of Science in Mechatronics program at Southern Denmark University, entitled 'Mechatronics: Design and Build' concentrates on some of the interdisciplinary aspects of Mechatronics Engineering. The 'Motion Control of Mechatronic Devices' is the main theme of this elective. Within this 'theme' the modelling, identification and compensation of nonlinear effects such as friction, stiction and hysteresis are considered. One of the most important components of the elective considers 'Smart Materials' and their use for actuation purposes. The theory, modelling and properties of piezoceramics. magneto- and electro- rheological fluids and dielectric electro active polymers (DEAP) are introduced in the 'Smart Materials' component. This paper initially reviews the laboratory experiments that have been developed for the dielectric electro active polymer section of the 'Mechatronics: Design and Build' elective. In lectures the students are introduced to the basic theory and fabrication of tubular actuators, that use DEAP material based on smart compliant electrode technology. In the laboratory the students to (a) carry out a series of experiments to characterise the tubular actuators, and (b) design a closed-loop position controller and test the performance of the controlled actuator for both step changes in desired position and periodic input reference signals. The last part of this contribution reviews some of the DEAP-based demonstration devices that been developed by Danfoss PolyPower A/S using their PolyPowerTM material which utilizes smart compliant electrode technology.

Stretchable degradable and electroactive shape memory copolymers with tunable recovery temperature enhance myogenic differentiation.

PubMed

Deng, Zexing; Guo, Yi; Zhao, Xin; Li, Longchao; Dong, Ruonan; Guo, Baolin; Ma, Peter X

2016-12-01

Development of flexible degradable electroactive shape memory polymers (ESMPs) with tunable switching temperature (around body temperature) for tissue engineering is still a challenge. Here we designed and synthesized a series of shape memory copolymers with electroactivity, super stretchability and tunable recovery temperature based on poly(ε-caprolactone) (PCL) with different molecular weight and conductive amino capped aniline trimer, and demonstrated their potential to enhance myogenic differentiation from C2C12 myoblast cells. We characterized the copolymers by Fourier transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance ( 1 H NMR), cyclic voltammetry (CV), ultraviolet-visible spectroscopy (UV-vis), differential scanning calorimetry (DSC), shape memory test, tensile test and in vitro enzymatic degradation study. The electroactive biodegradable shape memory copolymers showed great elasticity, tunable recovery temperature around 37°C, and good shape memory properties. Furthermore, proliferation and differentiation of C2C12 myoblasts were investigated on electroactive copolymers films, and they greatly enhanced the proliferation, myotube formation and related myogenic differentiation genes expression of C2C12 myoblasts compared to the pure PCL with molecular weight of 80,000. Our study suggests that these electroactive, highly stretchable, biodegradable shape memory polymers with tunable recovery temperature near the body temperature have great potential in skeletal muscle tissue engineering application. Conducting polymers can regulate cell behavior such cell adhesion, proliferation, and differentiation with or without electrical stimulation. Therefore, they have great potential for electrical signal sensitive tissue regeneration. Although conducting biomaterials with degradability have been developed, highly stretchable and electroactive degradable copolymers for soft tissue engineering have been rarely reported. On the other hand, shape memory polymers (SMPs) have been widely used in biomedical fields. However, SMPs based on polyesters usually are biologically inert. This work reported the design of super stretchable electroactive degradable SMPs based on polycaprolactone and aniline trimer with tunable recovery temperature around body temperature. These flexible electroactive SMPs facilitated the proliferation and differentiation of C2C12 myoblast cells compared with polycaprolactone, indicating that they are excellent scaffolding biomaterials in tissue engineering to repair skeletal muscle and possibly other tissues. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Creep-Fatigue Relationsihps in Electroactive Polymer Systems and Predicted Effects in an Actuator Design

NASA Technical Reports Server (NTRS)

Vinogradov, Aleksandra M.; Ihlefeld, Curtis M.; Henslee, Issac

2009-01-01

The paper concerns the time-dependent behavior of electroactive polymers (EAP) and their use in advanced intelligent structures for space exploration. Innovative actuator design for low weight and low power valves required in small plants planned for use on the moon for chemical analysis is discussed. It is shown that in-depth understanding of cyclic loading effects observed through accelerated creep rates due to creep-fatigue interaction in polymers is critical in terms of proper functioning of EAP based actuator devices. In the paper, an overview of experimental results concerning the creep properties and cyclic creep response of a thin film piezoelectric polymer polyvinylidene fluoride (PVDF) is presented. The development of a constitutive creep-fatigue interaction model to predict the durability and service life of electroactive polymers is discussed. A novel method is proposed to predict damage accumulation and fatigue life of polymers under oyclic loading conditions in the presence of creep. The study provides a basis for ongoing research initiatives at the NASA Kennedy Space Center in the pursuit of new technologies using EAP as active elements for lunar exploration systems.

Elastomer modulus and dielectric strength scaling with sample thickness

NASA Astrophysics Data System (ADS)

Larson, Kent

2015-04-01

Material characteristics such as adhesion and dielectric strength have well recognized dependencies on material thickness. There is disagreement, however, on the scale: the long held dictum that dielectric strength is inversely proportional to the square root of sample thickness has been shown to not always hold true for all materials, nor for all possible thickness regions. In D-EAP applications some studies have postulated a "critical thickness" below which properties show significantly less thickness dependency. While a great deal of data is available for dielectric strength, other properties are not nearly as well documented as samples get thinner. In particular, elastic modulus has been found to increase and elongation to decrease as sample thickness is lowered. This trend can be observed experimentally, but has been rarely reported and certainly does not appear in typical suppliers' product data sheets. Both published and newly generated data were used to study properties such as elastic modulus and dielectric strength vs sample thickness in silicone elastomers. Several theories are examined to explain such behavior, such as the impact of defect size and of common (but not well reported) concentration gradients that occur during elastomer curing that create micron-sized layers at the upper and lower interfaces with divergent properties to the bulk material. As Dielectric Electro-Active Polymer applications strive to lower and lower material thickness, changing mechanical properties must be recognized and taken into consideration for accurate electro-mechanical predictions of performance.

(Electro)Mechanical Properties of Olefinic Block Copolymers

NASA Astrophysics Data System (ADS)

Spontak, Richard

2014-03-01

Conventional styrenic triblock copolymers (SBCs) swollen with a midblock-selective oil have been previously shown to exhibit excellent electromechanical properties as dielectric elastomers. In this class of electroactive polymers, compliant electrodes applied as active areas to opposing surfaces of an elastomer attract each other, and thus compress the elastomer due to the onset of a Maxwell stress, upon application of an external electric field. This isochoric process is accompanied by an increase in lateral area, which yields the electroactuation strain (measuring beyond 300% in SBC systems). Performance parameters such as the Maxwell stress, transverse strain, dielectric breakdown, energy density and electromechanical efficiency are determined directly from the applied electric field and resulting electroactuation strain. In this study, the same principle used to evaluate SBC systems is extended to olefinic block copolymers (OBCs), which can be described as randomly-coupled multiblock copolymers that consist of crystallizable polyethylene hard segments and rubbery poly(ethylene-co-octene) soft segments. Considerations governing the development of a methodology to fabricate electroresponsive OBC systems are first discussed for several OBCs differing in composition and bulk properties. Evidence of electroactuation in selectively-solvated OBC systems is presented and performance metrics measured therefrom are quantitatively compared with dielectric elastomers derived from SBC and related materials.

Scalable sensing electronics towards a motion capture suit

NASA Astrophysics Data System (ADS)

Xu, Daniel; Gisby, Todd A.; Xie, Shane; Anderson, Iain A.

2013-04-01

Being able to accurately record body motion allows complex movements to be characterised and studied. This is especially important in the film or sport coaching industry. Unfortunately, the human body has over 600 skeletal muscles, giving rise to multiple degrees of freedom. In order to accurately capture motion such as hand gestures, elbow or knee flexion and extension, vast numbers of sensors are required. Dielectric elastomer (DE) sensors are an emerging class of electroactive polymer (EAP) that is soft, lightweight and compliant. These characteristics are ideal for a motion capture suit. One challenge is to design sensing electronics that can simultaneously measure multiple sensors. This paper describes a scalable capacitive sensing device that can measure up to 8 different sensors with an update rate of 20Hz.

Electrically and chemically tunable soft-solid block copolymer structural color (Conference Presentation)

NASA Astrophysics Data System (ADS)

Park, Cheolmin

2016-09-01

1D photonic crystals based on the periodic stacking of two different dielectric layers have been widely studied due to their potential use in low-power reflective mode displays, e-books and sensors, but the fabrication of mechanically flexible polymer structural color (SC) films, with electro-active color switching, remains challenging. Here, we demonstrate free-standing electric field tunable ionic liquid swollen block copolymer films. Placement of a polymer/ionic liquid (IL) film-reservoir adjacent to a self-assembled poly(styrene-block-quaternized 2vinyl pyridine) (PS-b-QP2VP) copolymer SC film allowed the development of R, G and B full-color SC block copolymer films by swelling of the QP2VP domains by the ionic liquid associated with water molecules. The IL-polymer/BCP SC film is mechanically flexible with excellent color stability over several days at ambient conditions. The selective swelling of the QP2VP domains could be controlled by both the ratio of the IL to a polymer in the gel-like IL reservoir layer and by an applied voltage in the range of -3V to +6V using a metal/IL reservoir/SC film/IL reservoir/metal capacitor type device.

Low Mass Muscle Actuators (LoMMAs) Using Electroactive Polymers

NASA Technical Reports Server (NTRS)

Bar-Cohen, Y.; Xue, T.; Joffe, B.; Lih, S. S.; Willis, P.; Simpson, J.; Smith, J.; Clair, T.; Shahinpoor, M.

1997-01-01

NASA is using actuation devices for many space applications and there is an increasing need to cut their cost as well as reduce their size, mass, and power consumption. Existing transducing actuators, such as piezoceramics, are inducing limited displacement levels. Potentially, electroactive polymers (so called EAP) can be formed as inexpensive, low-mass, low-power, miniature muscle actuators that are superior to the widely used actuators.

Enabling novel planetary and terrestrial mechanisms using electroactive materials at the JPL's NDEAA Lab

NASA Technical Reports Server (NTRS)

Bar-Cohen, Yoseph; Sherrit, Stewart; Bao, Xiaoqi; Chang, Zensheu; Lih, Shyh-Shiuh

2004-01-01

Increasingly, electroactive materials are used to produce acutators, sensors, displays and other elements of mechanisms and devices. In recognition of the potential of these materials, research at the JPL's NDEAA Lab have led to many novel space and terrestrial applications. This effort involves mostly the use of piezoelectric and electroactive polymers (EAP).

Ductile electroactive biodegradable hyperbranched polylactide copolymers enhancing myoblast differentiation.

PubMed

Xie, Meihua; Wang, Ling; Guo, Baolin; Wang, Zhong; Chen, Y Eugene; Ma, Peter X

2015-12-01

Myotube formation is crucial to restoring muscular functions, and biomaterials that enhance the myoblast differentiation into myotubes are highly desirable for muscular repair. Here, we report the synthesis of electroactive, ductile, and degradable copolymers and their application in enhancing the differentiation of myoblasts to myotubes. A hyperbranched ductile polylactide (HPLA) was synthesized and then copolymerized with aniline tetramer (AT) to produce a series of electroactive, ductile and degradable copolymers (HPLAAT). The HPLA and HPLAAT showed excellent ductility with strain to failure from 158.9% to 42.7% and modulus from 265.2 to 758.2 MPa. The high electroactivity of the HPLAAT was confirmed by UV spectrometer and cyclic voltammogram measurements. These HPLAAT polymers also showed improved thermal stability and controlled biodegradation rate compared to HPLA. Importantly, when applying these polymers for myotube formation, the HPLAAT significantly improved the proliferation of C2C12 myoblasts in vitro compared to HPLA. Furthermore, these polymers greatly promoted myogenic differentiation of C2C12 cells as measured by quantitative analysis of myotube number, length, diameter, maturation index, and gene expression of MyoD and TNNT. Together, our study shows that these electroactive, ductile and degradable HPLAAT copolymers represent significantly improved biomaterials for muscle tissue engineering compared to HPLA. Copyright © 2015 Elsevier Ltd. All rights reserved.

Ductile electroactive biodegradable hyperbranched polylactide copolymers enhancing myoblast differentiation

PubMed Central

Xie, Meihua; Wang, Ling; Guo, Baolin; Wang, Zhong; Chen, Y. Eugene; Ma, Peter X.

2015-01-01

Myotube formation is crucial to restoring muscular functions, and biomaterials that enhance the myoblast differentiation into myotubes are highly desirable for muscular repair. Here, we report the synthesis of electroactive, ductile, and degradable copolymers and their application in enhancing the differentiation of myoblasts to myotubes. A hyperbranched ductile polylactide (HPLA) was synthesized and then copolymerized with aniline tetramer (AT) to produce a series of electroactive, ductile and degradable copolymers (HPLAAT). The HPLA and HPLAAT showed excellent ductility with strain to failure from 158.9% to 42.7% and modulus from 265.2 to 758.2 MPa. The high electroactivity of the HPLAAT was confirmed by UV spectrometer and cyclic voltammogram measurements. These HPLAAT polymers also showed improved thermal stability and controlled biodegradation rate compared to HPLA. Importantly, when applying these polymers for myotube formation, the HPLAAT significantly improved the proliferation of C2C12 myoblasts in vitro compared to HPLA. Furthermore, these polymers greatly promoted myogenic differentiation of C2C12 cells as measured by quantitative analysis of myotube number, length, diameter, maturation index, and gene expression of MyoD and TNNT. Together, our study shows that these electroactive, ductile and degradable HPLAAT copolymers represent significantly improved biomaterials for muscle tissue engineering compared to HPLA. PMID:26335860

Design and fabrication of conductive polyaniline transducers via computer controlled direct ink writing

NASA Astrophysics Data System (ADS)

Holness, F. Benjamin; Price, Aaron D.

2017-04-01

The intractable nature of the conjugated polymer (CP) polyaniline (PANI) has largely limited PANI-based transducers to monolithic geometries derived from thin-film deposition techniques. To address this limitation, we have previously reported additive manufacturing processes for the direct ink writing of three-dimensional electroactive PANI structures. This technology incorporates a modified delta robot having an integrated polymer paste extrusion system in conjunction with a counter-ion induced thermal doping process to achieve these 3D structures. In this study, we employ an improved embodiment of this methodology for the fabrication of functional PANI devices with increasingly complex geometries and enhanced electroactive functionality. Advances in manufacturing capabilities achieved through the integration of a precision pneumatic fluid dispenser and redesigned high-pressure end-effector enable extrusion of viscous polymer formulations, improving the realizable resolutions of features and deposition layers. The integration of a multi-material dual-extrusion end-effector has further aided the fabrication of these devices, enabling the concurrent assembly of passive and active structures, which reduces the limitations on device geometry. Subsequent characterization of these devices elucidates the relationships between polymer formulation, process parameters, and device design such that electromechanical properties can be tuned according to application requirements. This methodology ultimately leads to the improved manufacturing of electroactive polymer-enabled devices with high-resolution 3D features and enhanced electroactive performance.

The Jellyfish: smart electro-active polymers for an autonomous distributed sensing node

NASA Astrophysics Data System (ADS)

Blottman, John B.; Richards, Roger T.

2006-05-01

The US Navy has recently placed emphasis on deployable, distributed sensors for Force Protection, Anti-Terrorism and Homeland Defense missions. The Naval Undersea Warfare Center has embarked on the development of a self-contained deployable node that is composed of electro-active polymers (EAP) for use in a covert persistent distributed surveillance system. Electro-Active Polymers (EAP) have matured to a level that permits their application in energy harvesting, hydrophones, electro-elastic actuation and electroluminescence. The problem to resolve is combining each of these functions into an autonomous sensing platform. The concept presented here promises an operational life several orders of magnitude beyond what is expected of a Sonobuoy due to energy conservation and harvesting, and at a reasonable cost. The embodiment envisioned is that of a deployed device resembling a jellyfish, made in most part of polymers, with the body encapsulating the necessary electronic processing and communications package and the tentacles of the jellyfish housing the sonar sensors. It will be small, neutrally buoyant, and will survey the water column much in the manner of a Cartesian Diver. By using the Electro-Active Polymers as artificial muscles, the motion of the jellyfish can be finely controlled. An increased range of detection and true node autonomy is achieved through volumetric array beamforming to focus the direction of interrogation and to null-out extraneous ambient noise.

Sensing/actuating materials made from carbon nanotube polymer composites and methods for making same

NASA Technical Reports Server (NTRS)

Ounaies, Zoubeida (Inventor); Park, Cheol (Inventor); Harrison, Joycelyn S. (Inventor); Holloway, Nancy M. (Inventor); Draughon, Gregory K. (Inventor)

2008-01-01

An electroactive sensing or actuating material comprises a composite made from a polymer with polarizable moieties and an effective amount of carbon nanotubes incorporated in the polymer for a predetermined electromechanical operation of the composite when such composite is affected by an external stimulus. In another embodiment, the composite comprises a third component of micro-sized to nano-sized particles of an electroactive ceramic that is also incorporated in the polymer matrix. The method for making the three-phase composite comprises either incorporating the carbon nanotubes in the polymer matrix before incorporation of the particles of ceramic or mixing the carbon nanotubes and particles of ceramic together in a solution before incorporation in the polymer matrix.

Electroactive polymer actuator based on a reduced graphene electrode

NASA Astrophysics Data System (ADS)

Im, Ki Hong; Choi, Hyonkwang

2014-03-01

We report an electroactive polymer (EAP) actuator using a reduced graphene electrode for a ionic polymer-metal composite actuator. Aqueous-reduced graphene is deposited to both sides of the ionic polymer membranes by using a simple inkjet printing process. The electrical and the optical properties of the reduced graphene were evaluated by using a four-point probe system, Raman spectroscopy, and Fourier-transform infrared attenuated total reflection spectroscopy. The actuator properties were evaluated from the curvatures of the ionic polymer graphene composite (IPGC) for various input voltages. From the results, we propose a new and simple isosceles trapezoidal element model for analyzing the relations among the input voltage, thickness, and curvature of IPGC.

A Review on Electroactive Polymers for Waste Heat Recovery.

PubMed

Kolasińska, Ewa; Kolasiński, Piotr

2016-06-17

This paper reviews materials for thermoelectric waste heat recovery, and discusses selected industrial and distributed waste heat sources as well as recovery methods that are currently applied. Thermoelectric properties, especially electrical conductivity, thermopower, thermal conductivity and the thermoelectric figures of merit, are considered when evaluating thermoelectric materials for waste heat recovery. Alloys and oxides are briefly discussed as materials suitable for medium- and high-grade sources. Electroactive polymers are presented as a new group of materials for low-grade sources. Polyaniline is a particularly fitting polymer for these purposes. We also discuss types of modifiers and modification methods, and their influence on the thermoelectric performance of this class of polymers.

Incorporation of fused tetrathiafulvalenes (TTFs) into polythiophene architectures: varying the electroactive dominance of the TTF species in hybrid systems.

PubMed

Berridge, Rory; Skabara, Peter J; Pozo-Gonzalo, Cristina; Kanibolotsky, Alexander; Lohr, Jan; McDouall, Joseph J W; McInnes, Eric J L; Wolowska, Joanna; Winder, Christoph; Sariciftci, N Serdar; Harrington, Ross W; Clegg, William

2006-02-23

A novel polythienylenevinylene (PTV) and two new polythiophenes (PTs), featuring fused tetrathiafulvalene (TTF) units, have been prepared and characterized by ultraviolet-visible (UV-vis) and electron paramagnetic resonance (EPR) spectroelectrochemistry. All polymers undergo two sequential, reversible oxidation processes in solution. Structures in which the TTF species is directly linked to the polymer backbone (2 and 4) display redox behavior which is dictated by the fulvalene system. Once the TTF is spatially removed from the polymer chain by a nonconjugated link (polymer 3), the electroactivity of both TTF and polythiophene moieties can be detected. Computational studies confirm the delocalization of charge over both electroactive centers (TTF and PT) and the existence of a triplet dication intermediate. PTV 4 has a low band gap (1.44 eV), is soluble in common organic solvents, and is stable under ambient conditions. Organic solar cells of polymer 4:[6,6]-phenyl-C(61) butyric acid methyl ester (PCBM) have been fabricated. Under illumination, a photovoltaic effect is observed with a power conversion efficiency of 0.13% under AM1.5 solar simulated light. The onset of photocurrent at 850 nm is consistent with the onset of the pi-pi absorption band of the polymer. Remarkably, UV-vis spectroelectrochemistry of polymer 4 reveals that the conjugated polymer chain remains unchanged during the oxidation of the polymer.

Electroactive and High Dielectric Folic Acid/PVDF Composite Film Rooted Simplistic Organic Photovoltaic Self-Charging Energy Storage Cell with Superior Energy Density and Storage Capability.

PubMed

Roy, Swagata; Thakur, Pradip; Hoque, Nur Amin; Bagchi, Biswajoy; Sepay, Nayim; Khatun, Farha; Kool, Arpan; Das, Sukhen

2017-07-19

Herein we report a simplistic prototype approach to develop an organic photovoltaic self-charging energy storage cell (OPSESC) rooted with biopolymer folic acid (FA) modified high dielectric and electroactive β crystal enriched poly(vinylidene fluoride) (PVDF) composite (PFA) thin film. Comprehensive and exhaustive characterizations of the synthesized PFA composite films validate the proper formation of β-polymorphs in PVDF. Significant improvements of both β-phase crystallization (F(β) ≈ 71.4%) and dielectric constant (ε ≈ 218 at 20 Hz for PFA of 7.5 mass %) are the twosome realizations of our current study. Enhancement of β-phase nucleation in the composites can be thought as a contribution of the strong interaction of the FA particles with the PVDF chains. Maxwell-Wagner-Sillars (MWS) interfacial polarization approves the establishment of thermally stable high dielectric values measured over a wide temperature spectrum. The optimized high dielectric and electroactive films are further employed as an active energy storage material in designing our device named as OPSESC. Self-charging under visible light irradiation without an external biasing electrical field and simultaneous remarkable self-storage of photogenerated electrical energy are the two foremost aptitudes and the spotlight of our present investigation. Our as fabricated device delivers an impressively high energy density of 7.84 mWh/g and an excellent specific capacitance of 61 F/g which is superior relative to the other photon induced two electrode organic self-charging energy storage devices reported so far. Our device also proves the realistic utility with good recycling capability by facilitating commercially available light emitting diode.

Research Trends of Soft Actuators based on Electroactive Polymers and Conducting Polymers

NASA Astrophysics Data System (ADS)

Kaneto, K.

2016-04-01

Artificial muscles (or soft actuators) based on electroactive polymers (EAPs) are attractive power sources to drive human-like robots in place of electrical motor, because they are quiet, powerful, light weight and compact. Among EAPs for soft actuators, conducting polymers are superior in strain, stress, deformation form and driving voltage compared with the other EAPs. In this paper, the research trends of EAPs and conducting polymers are reviewed by retrieval of the papers and patents. The research activity of EAP actuators showed the maximum around 2010 and somehow declining now days. The reasons for the reducing activity are found to be partly due to problems of conducting polymer actuators for the practical application. The unique characteristics of conducting polymer actuators are mentioned in terms of the basic mechanisms of actuation, creeping, training effect and shape retention under high tensile loads. The issues and limitation of conducting polymer soft actuators are discussed.

An Electrolyte-Free Conducting Polymer Actuator that Displays Electrothermal Bending and Flapping Wing Motions under a Magnetic Field.

PubMed

Uh, Kyungchan; Yoon, Bora; Lee, Chan Woo; Kim, Jong-Man

2016-01-20

Electroactive materials that change shape in response to electrical stimulation can serve as actuators. Electroactive actuators of this type have great utility in a variety of technologies, including biomimetic artificial muscles, robotics, and sensors. Electroactive actuators developed to date often suffer from problems associated with the need to use electrolytes, slow response times, high driving voltages, and short cycle lifetimes. Herein, we report an electrolyte-free, single component, polymer electroactive actuator, which has a fast response time, high durability, and requires a low driving voltage (<5 V). The process employed for production of this material involves wet-spinning of a preorganized camphorsulfonic acid (CSA)-doped polyaniline (PANI) gel, which generates long, flexible, and conductive (∼270 S/cm) microfibers. Reversible bending motions take place upon application of an alternating current (AC) to the PANI polymer. This motion, promoted by a significantly low driving voltage (<0.5 V) in the presence of an external magnetic field, has a very large swinging speed (9000 swings/min) that lies in the range of those of flies and bees (1000-15000 swings/min) and is fatigue-resistant (>1000000 cycles).

Electrorotation of novel electroactive polymer composites in uniform DC and AC electric fields

NASA Astrophysics Data System (ADS)

Zrinyi, Miklós; Nakano, Masami; Tsujita, Teppei

2012-06-01

Novel electroactive polymer composites have been developed that could spin in uniform DC and AC electric fields. The angular displacement as well as rotation of polymer disks around an axis that is perpendicular to the direction of the applied electric field was studied. It was found that the dynamics of the polymer rotor is very complex. Depending on the strength of the static DC field, three regimes have been observed: no rotation occurs below a critical threshold field intensity, oscillatory motion takes place just above this value and continuous rotation can be observed above the critical threshold field intensity. It was also found that low frequency AC fields could also induce angular deformation.

A Review on Electroactive Polymers for Waste Heat Recovery

PubMed Central

Kolasińska, Ewa; Kolasiński, Piotr

2016-01-01

This paper reviews materials for thermoelectric waste heat recovery, and discusses selected industrial and distributed waste heat sources as well as recovery methods that are currently applied. Thermoelectric properties, especially electrical conductivity, thermopower, thermal conductivity and the thermoelectric figures of merit, are considered when evaluating thermoelectric materials for waste heat recovery. Alloys and oxides are briefly discussed as materials suitable for medium- and high-grade sources. Electroactive polymers are presented as a new group of materials for low-grade sources. Polyaniline is a particularly fitting polymer for these purposes. We also discuss types of modifiers and modification methods, and their influence on the thermoelectric performance of this class of polymers. PMID:28773605

Dual-responsive soft actuators based on self-assembled polymers

NASA Astrophysics Data System (ADS)

Kim, Seung Jae; Park, Moon Jeong

Electroactive polymer actuators (EAPs) have been extensively studied for biomimetic technologies such as artificial muscles and soft robotics. While a large deformation can be achievable from EAPs under relatively low-driving voltages, the slow response time has long been a fundamental drawback of EAPs. Here, we investigate a new soft actuator capable of responding two different external stimuli. The actuator is composed of electroactive polymer and light-responsive polymer. We have employed ionic block copolymers having well-connected ion-conduction channels to raise response to electric-field. Light-responsive polymers were additionally incorporated into them to control the deformation of the actuator in an independent manner. Noteworthy observation in the present study is that the dual-responsive polymers resulted in synergetic achievement of high bending strain and fast response time, which marked a significant improvement from the conventional EAPs.

Measuring the bending of asymmetric planar EAP structures

NASA Astrophysics Data System (ADS)

Weiss, Florian M.; Zhao, Xue; Thalmann, Peter; Deyhle, Hans; Urwyler, Prabitha; Kovacs, Gabor; Müller, Bert

2013-04-01

The geometric characterization of low-voltage dielectric electro-active polymer (EAP) structures, comprised of nanometer thickness but areas of square centimeters, for applications such as artificial sphincters requires methods with nanometer precision. Direct optical detection is usually restricted to sub-micrometer resolution because of the wavelength of the light applied. Therefore, we propose to take advantage of the cantilever bending system with optical readout revealing a sub-micrometer resolution at the deflection of the free end. It is demonstrated that this approach allows us to detect bending of rather conventional planar asymmetric, dielectric EAP-structures applying voltages well below 10 V. For this purpose, we built 100 μm-thin silicone films between 50 nm-thin silver layers on a 25 μm-thin polyetheretherketone (PEEK) substrate. The increase of the applied voltage in steps of 50 V until 1 kV resulted in a cantilever bending that exhibits only in restricted ranges the expected square dependence. The mean laser beam displacement on the detector corresponded to 6 nm per volt. The apparatus will therefore become a powerful mean to analyze and thereby improve low-voltage dielectric EAP-structures to realize nanometer-thin layers for stack actuators to be incorporated into artificial sphincter systems for treating severe urinary and fecal incontinence.

Ionic electroactive polymer artificial muscles in space applications.

PubMed

Punning, Andres; Kim, Kwang J; Palmre, Viljar; Vidal, Frédéric; Plesse, Cédric; Festin, Nicolas; Maziz, Ali; Asaka, Kinji; Sugino, Takushi; Alici, Gursel; Spinks, Geoff; Wallace, Gordon; Must, Indrek; Põldsalu, Inga; Vunder, Veiko; Temmer, Rauno; Kruusamäe, Karl; Torop, Janno; Kaasik, Friedrich; Rinne, Pille; Johanson, Urmas; Peikolainen, Anna-Liisa; Tamm, Tarmo; Aabloo, Alvo

2014-11-05

A large-scale effort was carried out to test the performance of seven types of ionic electroactive polymer (IEAP) actuators in space-hazardous environmental factors in laboratory conditions. The results substantiate that the IEAP materials are tolerant to long-term freezing and vacuum environments as well as ionizing Gamma-, X-ray, and UV radiation at the levels corresponding to low Earth orbit (LEO) conditions. The main aim of this material behaviour investigation is to understand and predict device service time for prolonged exposure to space environment.

The inclusion of electroactive β-phase in Sn2+ incorporated PVDF composite film for improving dielectric properties and piezoelectric energy generation

NASA Astrophysics Data System (ADS)

Alam, Md. Mehebub; Mandal, Dipankar

2018-04-01

Low content (0.5 wt. %) of dihydrate tin chloride (Sn2+) salt leads to inclusion of 98 % electroactive phase in poly(vinylidene fluoride) (PVDF), out of this a high yield of piezoelectric β-phase (˜ 49%) is found, which is most desirable for mechanical energy harvesting application. It is also found that Sn2+ salt can significantly enhanced the dielectric property of resulting Sn2+ incorporated PVDF composite film. Thus, the enhancement of β-phase in the PVDF/Sn2+ composite film owns to be a potential material for mechanical energy harvesting application. We have also demonstrated the mechanical energy harvesting capability of the nanogenerator (NG) made with PVDF/Sn2+ composite film under repeated human finger touch.

Theoretical Evaluation of Electroactive Polymer Based Micropump Diaphragm for Air Flow Control

NASA Technical Reports Server (NTRS)

Xu, Tian-Bing; Su, Ji; Zhang, Qiming

2004-01-01

An electroactive polymer (EAP), high energy electron irradiated poly(vinylidene fluoride-trifluoroethylene) [P(VDFTrFE)] copolymer, based actuation micropump diaphragm (PAMPD) have been developed for air flow control. The displacement strokes and profiles as a function of amplifier and frequency of electric field have been characterized. The volume stroke rates (volume rate) as function of electric field, driving frequency have been theoretically evaluated, too. The PAMPD exhibits high volume rate. It is easily tuned with varying of either amplitude or frequency of the applied electric field. In addition, the performance of the diaphragms were modeled and the agreement between the modeling results and experimental data confirms that the response of the diaphragms follow the design parameters. The results demonstrated that the diaphragm can fit some future aerospace applications to replace the traditional complex mechanical systems, increase the control capability and reduce the weight of the future air dynamic control systems. KEYWORDS: Electroactive polymer (EAP), micropump, diaphragm, actuation, displacement, volume rate, pumping speed, clamping ratio.

A Hybrid Actuation System Demonstrating Significantly Enhanced Electromechanical Performance

NASA Technical Reports Server (NTRS)

Su, Ji; Xu, Tian-Bing; Zhang, Shujun; Shrout, Thomas R.; Zhang, Qiming

2004-01-01

A hybrid actuation system (HYBAS) utilizing advantages of a combination of electromechanical responses of an electroactive polymer (EAP), an electrostrictive copolymer, and an electroactive ceramic single crystal, PZN-PT single crystal, has been developed. The system employs the contribution of the actuation elements cooperatively and exhibits a significantly enhanced electromechanical performance compared to the performances of the device made of each constituting material, the electroactive polymer or the ceramic single crystal, individually. The theoretical modeling of the performances of the HYBAS is in good agreement with experimental observation. The consistence between the theoretical modeling and experimental test make the design concept an effective route for the development of high performance actuating devices for many applications. The theoretical modeling, fabrication of the HYBAS and the initial experimental results will be presented and discussed.

Fabrication of a self-sensing electroactive polymer bimorph actuator based on polyvinylidene fluoride and its electrostrictive terpolymer

NASA Astrophysics Data System (ADS)

Engel, Leeya; Van Volkinburg, Kyle R.; Ben-David, Moti; Washington, Gregory N.; Krylov, Slava; Shacham-Diamand, Yosi

2016-04-01

In this paper, we report on the fabrication of a self-sensing electroactive polymer cantilevered bimorph beam actuator and its frequency response. Tip deflections of the beam, induced by applying an AC signal across ferroelectric relaxor polyvinylidene fluoride-trifluoroethylene chlorotrifluoroethylene (P(VDF-TrFE-CTFE)), reached a magnitude of 350μm under a field of ~55MV/m and were recorded externally using a laser Doppler vibrometer (LDV). Deflections were determined simultaneously by applying a sensing model to the voltage measured across the bimorph's integrated layer of piezoelectric polymer polyvinylidene fluoride (PVDF). The sensing model treats the structure as a simple Euler- Bernoulli cantilevered beam with two distributed active elements represented through the use of generalized functions and offers a method through which real time tip deflection can be measured without the need for external visualization. When not being used as a sensing element, the PVDF layer can provide an additional means for actuation of the beam via the converse piezoelectric effect, resulting in bidirectional control of the beam's deflections. Integration of flexible sensing elements together with modeling of the electroactive polymer beam can benefit the developing field of polymer microactuators which have applications in soft robotics as "smart" prosthetics/implants, haptic displays, tools for less invasive surgery, and sensing.

Electrostrictive Graft Elastomers and Applications

NASA Technical Reports Server (NTRS)

Su, J.; Harrison, J. S.; St.Clair, T. L.; Bar-Cohen, Y.; Leary, S.

1999-01-01

Efficient actuators that are lightweight, high performance and compact are needed to support telerobotic requirements for future NASA missions. In this work, we present a new class of electromechanically active polymers that can potentially be used as actuators to meet many NASA needs. The materials are graft elastomers that offer high strain under an applied electric field. Due to its higher mechanical modulus, this elastomer also has a higher strain energy density as compared to previously reported electrostrictive polyurethane elastomers. The dielectric, mechanical and electromechanical properties of this new electrostrictive elastomer have been studied as a function of temperature and frequency. Combined with structural analysis using x-ray diffraction and differential scanning calorimetry on the new elastomer, structure-property interrelationship and mechanisms of the electric field induced strain in the graft elastomer have also been investigated. This electroactive polymer (EAP) has demonstrated high actuation strain and high mechanical energy density. The combination of these properties with its tailorable molecular composition and excellent processability makes it attractive for a variety of actuation tasks. The experimental results and applications will be presented.

Ionic electroactive polymer artificial muscles in space applications

PubMed Central

Punning, Andres; Kim, Kwang J.; Palmre, Viljar; Vidal, Frédéric; Plesse, Cédric; Festin, Nicolas; Maziz, Ali; Asaka, Kinji; Sugino, Takushi; Alici, Gursel; Spinks, Geoff; Wallace, Gordon; Must, Indrek; Põldsalu, Inga; Vunder, Veiko; Temmer, Rauno; Kruusamäe, Karl; Torop, Janno; Kaasik, Friedrich; Rinne, Pille; Johanson, Urmas; Peikolainen, Anna-Liisa; Tamm, Tarmo; Aabloo, Alvo

2014-01-01

A large-scale effort was carried out to test the performance of seven types of ionic electroactive polymer (IEAP) actuators in space-hazardous environmental factors in laboratory conditions. The results substantiate that the IEAP materials are tolerant to long-term freezing and vacuum environments as well as ionizing Gamma-, X-ray, and UV radiation at the levels corresponding to low Earth orbit (LEO) conditions. The main aim of this material behaviour investigation is to understand and predict device service time for prolonged exposure to space environment. PMID:25372857

Electroactive polymer gels based on epoxy resin

NASA Astrophysics Data System (ADS)

Samui, A. B.; Jayakumar, S.; Jayalakshmi, C. G.; Pandey, K.; Sivaraman, P.

2007-04-01

Five types of epoxy gels have been synthesized from common epoxy resins and hardeners. Fumed silica and nanoclay, respectively, were used as fillers and butyl methacrylate/acrylamide were used as monomer(s) for making interpenetrating polymer networks (IPNs) in three compositions. Swelling study, tensile property evaluation, dynamic mechanical thermal analysis, thermo-gravimetric analysis, scanning electron microscopy and electroactive property evaluation were done. The gels have sufficient mechanical strength and the time taken for bending to 20° was found to be 22 min for forward bias whereas it was just 12 min for reverse bias.

Recent Progress on Cellulose-Based Electro-Active Paper, Its Hybrid Nanocomposites and Applications

PubMed Central

Khan, Asif; Abas, Zafar; Kim, Heung Soo; Kim, Jaehwan

2016-01-01

We report on the recent progress and development of research into cellulose-based electro-active paper for bending actuators, bioelectronics devices, and electromechanical transducers. The cellulose electro-active paper is characterized in terms of its biodegradability, chirality, ample chemically modifying capacity, light weight, actuation capability, and ability to form hybrid nanocomposites. The mechanical, electrical, and chemical characterizations of the cellulose-based electro-active paper and its hybrid composites such as blends or coatings with synthetic polymers, biopolymers, carbon nanotubes, chitosan, and metal oxides, are explained. In addition, the integration of cellulose electro-active paper is highlighted to form various functional devices including but not limited to bending actuators, flexible speaker, strain sensors, energy harvesting transducers, biosensors, chemical sensors and transistors for electronic applications. The frontiers in cellulose paper devices are reviewed together with the strategies and perspectives of cellulose electro-active paper and cellulose nanocomposite research and applications. PMID:27472335

Recent Progress on Cellulose-Based Electro-Active Paper, Its Hybrid Nanocomposites and Applications.

PubMed

Khan, Asif; Abas, Zafar; Kim, Heung Soo; Kim, Jaehwan

2016-07-26

We report on the recent progress and development of research into cellulose-based electro-active paper for bending actuators, bioelectronics devices, and electromechanical transducers. The cellulose electro-active paper is characterized in terms of its biodegradability, chirality, ample chemically modifying capacity, light weight, actuation capability, and ability to form hybrid nanocomposites. The mechanical, electrical, and chemical characterizations of the cellulose-based electro-active paper and its hybrid composites such as blends or coatings with synthetic polymers, biopolymers, carbon nanotubes, chitosan, and metal oxides, are explained. In addition, the integration of cellulose electro-active paper is highlighted to form various functional devices including but not limited to bending actuators, flexible speaker, strain sensors, energy harvesting transducers, biosensors, chemical sensors and transistors for electronic applications. The frontiers in cellulose paper devices are reviewed together with the strategies and perspectives of cellulose electro-active paper and cellulose nanocomposite research and applications.

Micro-mechanics of ionic electroactive polymer actuators

NASA Astrophysics Data System (ADS)

Punning, Andres; Põldsalu, Inga; Kaasik, Friedrich; Vunder, Veiko; Aabloo, Alvo

2015-04-01

Commonly, modeling of the bending behavior of the ionic electroactive polymer (IEAP) actuators is based on the classical mechanics of cantilever beam. It is acknowledged, that the actuation of the ionic electroactive polymer (IEAP) actuators is symmetric about the centroid - the convex side of the actuator is expanding and the concave side is contracting for exactly the same amount, while the thickness of the actuator remains invariant. Actuating the IEAP actuators and sensors under scanning electron microscope (SEM), in situ, reveals that for some types of them this approach is incorrect. Comparison of the SEM micrographs using the Digital Image Correction (DIC) method results with the precise strain distribution of the IEAP actuators in two directions: in the axial direction, and in the direction of thickness. This information, in turn, points to the physical processes taking place within the electrodes as well as membrane of the trilayer laminate of sub-millimeter thickness. Comparison of the EAP materials, engaged as an actuator as well as a sensor, reveals considerable differences between the micro-mechanics of the two modes.

Polysiloxane binder for lithium ion battery electrodes

DOEpatents

Zhang, Zhengcheng; Dong, Jian; Amine, Khalil

2015-10-13

An electrode includes a binder and an electroactive material, wherein the binder includes a polymer including a linear polysiloxane or a cyclic polysiloxane. The polymer may be generally represented by Formula I: ##STR00001##

An investigation of a thermally steerable electroactive polymer/shape memory polymer hybrid actuator

NASA Astrophysics Data System (ADS)

Ren, Kailiang; Bortolin, Robert S.; Zhang, Q. M.

2016-02-01

This paper investigates the thermal response of a hybrid actuator composed of an electroactive polymer (EAP) and a shape memory polymer (SMP). This study introduces the concept of using the large strain from a phase transition (ferroelectric to paraelectric phase) induced by temperature change in a poly(vinylidene fluoride-trifluoroethylene) film to tune the shape of an SMP film above its glass transition temperature (Tg). Based on the material characterization data, it is revealed that the thickness ratio of the EAP/SMP films plays a critical role in the displacement of the actuator. Further, it is also demonstrated that the displacement of the hybrid actuator can be tailored by varying the temperature, and finite element method simulation results fit well with the measurement data. This specially designed hybrid actuator shows great promise for future morphing aircraft applications.

Fused filament 3D printing of ionic polymer-metal composites (IPMCs)

NASA Astrophysics Data System (ADS)

Carrico, James D.; Traeden, Nicklaus W.; Aureli, Matteo; Leang, Kam K.

2015-12-01

This paper describes a new three-dimensional (3D) fused filament additive manufacturing (AM) technique in which electroactive polymer filament material is used to build soft active 3D structures, layer by layer. Specifically, the unique actuation and sensing properties of ionic polymer-metal composites (IPMCs) are exploited in 3D printing to create electroactive polymer structures for application in soft robotics and bio-inspired systems. The process begins with extruding a precursor material (non-acid Nafion precursor resin) into a thermoplastic filament for 3D printing. The filament is then used by a custom-designed 3D printer to manufacture the desired soft polymer structures, layer by layer. Since at this stage the 3D-printed samples are not yet electroactive, a chemical functionalization process follows, consisting in hydrolyzing the precursor samples in an aqueous solution of potassium hydroxide and dimethyl sulfoxide. Upon functionalization, metal electrodes are applied on the samples through an electroless plating process, which enables the 3D-printed IPMC structures to be controlled by voltage signals for actuation (or to act as sensors). This innovative AM process is described in detail and the performance of 3D printed IPMC actuators is compared to an IPMC actuator fabricated from commercially available Nafion sheet material. The experimental results show comparable performance between the two types of actuators, demonstrating the potential and feasibility of creating functional 3D-printed IPMCs.

Electroactive Polymers as Artificial Muscles - Reality and Challenges

NASA Technical Reports Server (NTRS)

Bar-Cohen, Y.

2001-01-01

Electroactive Polymers (EAPs) are emerging as effective displacement actuators. These materials offer the closest resemblance of biological muscle potentially enabling unique capabilities changing the paradigm about robots construction. Under a NASA task, several EAP driven mechanisms were developed including dust wiper, gripper, and robotic arm EAP are inducing a low actuation force limiting the applications that can use their current capability. In recognition of this limitation a series of international forums were established including SPIE conference, Webhub, Newsletter, and Newsgroup. A challenge was posed to the EAP community to have an arm wrestling between robot that is equipped with EAP actuators and human.

Refreshable tactile displays based on bistable electroactive polymer

NASA Astrophysics Data System (ADS)

Niu, Xiaofan; Brochu, Paul; Salazar, Brandon; Pei, Qibing

2011-04-01

Refreshable tactile displays can significantly improve the education of blind children and the quality of life of people with severe vision impairment. A number of actuator technologies have been investigated. Bistable Electroactive Polymer (BSEP) appears to be well suited for this application. The BSEP exhibits a bistable electrically actuated strain as large as 335%. We present improved refreshable tactile display devices fabricated on thin plastic sheets. Stacked BSEP films were employed to meet the requirements in raised dot height and supporting force. The bistable nature of the actuation reduces the power consumption and simplifies the device operation.

Bottlebrush elastomers: a promising molecular engineering route to tunable, prestrain-free dielectric elastomers (Conference Presentation)

NASA Astrophysics Data System (ADS)

Vatankhah-Varnosfaderani, Mohammad; Daniel, William F. M.; Zhushma, Alexandr P.; Li, Qiaoxi; Morgan, Benjamin J.; Matyjaszewski, Krzysztof; Armstrong, Daniel P.; Dobrynin, Andrey V.; Sheyko, Sergei S.; Spontak, Richard J.

2017-04-01

Electroactive polymers (EAPs) refer to a broad range of relatively soft materials that change size and/or shape upon application of an electrical stimulus. Of these, dielectric elastomers (DEs) generated from either chemically- or physically-crosslinked polymer networks afford the highest levels of electroactuation strain, thereby making this class of EAPs the leading technology for artificial-muscle applications. While mechanically prestraining elastic networks remarkably enhances DEs electroactuation, external prestrain protocols severely limit both actuator performance and device implementation due to gradual DE stress relaxation and the presence of a cumbersome load frame. These drawbacks have persisted with surprisingly minimal advances in the actuation of single-component elastomers since the dawn of the "pre-strain era" introduced by Pelrine et al. (Science, 2000). In this work, we present a bottom-up, molecular-based strategy for the design of prestrain-free (freestanding) DEs derived from covalently-crosslinked bottlebrush polymers. This architecture, wherein design factors such as crosslink density, graft density and graft length can all be independently controlled, yields inherently strained polymer networks that can be readily adapted to a variety of chemistries. To validate the use of these molecularly-tunable materials as DEs, we have synthesized a series of bottlebrush silicone elastomers in as-cast shapes. Examination of these materials reveals that they undergo giant electroactuation strains (>300%) at relatively low fields (<10 V/m), thereby outperforming all commercial DEs to date and opening new opportunities in responsive soft-material technologies (e.g., robotics). The molecular design approach to controlling (electro)mechanical developed here is independent of chemistry and permits access to an unprecedented range of actuation properties from elastomeric materials with traditionally modest electroactuation performance (e.g., polydimethylsiloxane, PDMS). Experimental results obtained here compare favorably with theoretical predictions and demonstrate that the unique behavior of these materials is a direct consequence of the molecular architecture.

Biomimetic actuators using electroactive polymers (EAP) as artificial muscles

NASA Technical Reports Server (NTRS)

Bar-Cohen, Yoseph

2006-01-01

Evolution has resolved many of nature's challenges leading to lasting solutions with maximal performance and effective use of resources. Nature's inventions have always inspired human achievements leading to effective materials, structures, tools, mechanisms, processes, algorithms, methods, systems and many other benefits. The field of mimicking nature is known as Biomimetics and one of its topics includes electroactive polymers that gain the moniker artificial muscles. Integrating EAP with embedded sensors, self-repair and many other capabilities that are used in composite materials can add greatly to the capability of smart biomimetic systems. Such development would enable fascinating possibilities potentially turning science fiction ideas into engineering reality.

Polymer Composite and Nanocomposite Dielectric Materials for Pulse Power Energy Storage †

PubMed Central

Barber, Peter; Balasubramanian, Shiva; Anguchamy, Yogesh; Gong, Shushan; Wibowo, Arief; Gao, Hongsheng; Ploehn, Harry J.; zur Loye, Hans-Conrad

2009-01-01

This review summarizes the current state of polymer composites used as dielectric materials for energy storage. The particular focus is on materials: polymers serving as the matrix, inorganic fillers used to increase the effective dielectric constant, and various recent investigations of functionalization of metal oxide fillers to improve compatibility with polymers. We review the recent literature focused on the dielectric characterization of composites, specifically the measurement of dielectric permittivity and breakdown field strength. Special attention is given to the analysis of the energy density of polymer composite materials and how the functionalization of the inorganic filler affects the energy density of polymer composite dielectric materials.

Controllable Curved Mirrors Made from Single-Layer EAP Films

NASA Technical Reports Server (NTRS)

Bao, Xiaoqi; Bar-Cohen, Yoseph; Sherrit, Stewart

2004-01-01

A document proposes that lightweight, deployable, large-aperture, controllable curved mirrors made of reflectively coated thin electroactive-polymer (EAP) films be developed for use in spaceborne microwave and optical systems. In these mirrors, the EAP films would serve as both structures and actuators. EAPs that are potentially suitable for such use include piezoelectric, electrostrictive, ferroelectric, and dielectric polymers. These materials exhibit strains proportional to the squares of applied electric fields. Utilizing this phenomenon, a curved mirror according to the proposal could be made from a flat film, upon which a nonuniform electrostatic potential (decreasing from the center toward the edge) would be imposed to obtain a required curvature. The effect would be analogous to that of an old-fashioned metalworking practice in which a flat metal sheet is made into a bowl by hammering it repeatedly, the frequency of hammer blows decreasing with distance from the center. In operation, the nonuniform electrostatic potential could be imposed by use of an electron gun. Calculations have shown that by use of a single- layer film made of a currently available EAP, it would be possible to control the focal length of a 2-m-diameter mirror from infinity to 1.25 m.

BIOAFFINITY SENSORS BASED ON CONDUCTING POLYMERS: A SHORT REVIEW. (R825323)

EPA Science Inventory

The development of new electrode materials has expanded the range and classes of detectable compounds using electroanalytical methods. Conducting electroactive polymers (CEPs) have been demonstrated to have remarkable sensing applications through their ability to be reversibly ox...

EAP as artificial muscles - progress and challenges

NASA Technical Reports Server (NTRS)

Bar-Cohen, Yoseph

2004-01-01

During the last decade and a half new polymers have emerged that respond to electrical stimulation with a significant shape or size change. This capability of electroactive polymer (EAP) materials is attracting the attention of engineers and scientists from many different disciplines.

Polymer Nanocomposite Materials with High Dielectric Permittivity and Low Dielectric Loss Properties

NASA Astrophysics Data System (ADS)

Toor, Anju

Materials with high dielectric permittivity have drawn increasing interests in recent years for their important applications in capacitors, actuators, and high energy density pulsed power. Particularly, polymer-based dielectrics are excellent candidates, owing to their properties such as high breakdown strength, low dielectric loss, flexibility and easy processing. To enhance the dielectric permittivity of polymer materials, typically, high dielectric constant filler materials are added to the polymer. Previously, ferroelectric and conductive fillers have been mainly used. However, such systems suffered from various limitations. For example, composites based on ferroelectric materials like barium titanate, exhibited high dielectric loss, and poor saturation voltages. Conductive fillers are used in the form of powder aggregates, and they may show 10-100 times enhancement in dielectric constant, however these nanoparticle aggregates cause the dielectric loss to be significant. Also, agglomerates limit the volume fraction of fillers in polymer and hence, the ability to achieve superior dielectric constants. Thus, the aggregation of nanoparticles is a significant challenge to their use to improve the dielectric permittivity. We propose the use of ligand-coated metal nanoparticle fillers to enhance the dielectric properties of the host polymer while minimizing dielectric loss by preventing nanoparticle agglomeration. The focus is on obtaining uniform dispersion of nanoparticles with no agglomeration by utilizing appropriate ligands/surface functionalizations on the gold nanoparticle surface. Use of ligand coated metal nanoparticles will enhance the dielectric constant while minimizing dielectric loss, even with the particles closely packed in the polymer matrix. Novel combinations of materials, which use 5 nm diameter metal nanoparticles embedded inside high breakdown strength polymer materials are evaluated. High breakdown strength polymer materials are chosen to allow further exploration of these materials for energy storage applications. In summary, two novel nanocomposite materials are designed and synthesized, one involving polyvinylidene fluoride (PVDF) as the host polymer for potential applications in energy storage and the other with SU-8 for microelectronic applications. Scanning elec- tron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy and ultramicrotoming techniques were used for the material characterization of the nanocomposite materials. A homogeneous dispersion of gold nanoparticles with low particle agglomeration has been achieved. Fabricated nanoparticle polymer composite films showed the absence of voids and cracks. Also, no evidence of macro-phase separation of nanoparticles from the polymer phase was observed. This is important because nanoparticle agglomeration and phase separation from the polymer usually results in poor processability of films and a high defect density. Dielectric characterization of the nanocomposite materials showed enhancement in the dielectric constant over the base polymer values and low dielectric loss values were observed.

Cellulose Electro-Active Paper: From Discovery to Technology Applications

NASA Astrophysics Data System (ADS)

Abas, Zafar; Kim, Heung Soo; Kim, Jaehwan; Kim, Joo-Hyung

2014-09-01

Cellulose electro-active paper (EAPap) is an attractive material of electro-active polymers (EAPs) family due to its smart characteristics. EAPap is thin cellulose film coated with metal electrodes on both sides. Its large displacement output, low actuation voltage and low power consumption can be used for biomimetic sensors/actuators and electromechanical system. Because cellulose EAPap is ultra-lightweight, easy to manufacture, inexpensive, biocompatible, and biodegradable, it has been employed for many applications such as bending actuator, vibration sensor, artificial muscle, flexible speaker, and can be advantageous in areas such as micro-insect robots, micro-flying objects, microelectromechanical systems, biosensors, and flexible displays.

Functionalization of reduced graphene oxide by electroactive polymer for biosensing applications

NASA Astrophysics Data System (ADS)

Nguyen, Le Huy; Dzung Nguyen, Tuan; Hoang Tran, Vinh; Thu Huyen Dang, Thi; Tran, Dai Lam

2014-09-01

A novel biosensing platform was designed by the functionalizing reduced graphene oxide sheets (rGO) with electroactive copolymer juglone. The composite film showed well-defined, stable electroactivity in a biocompatible buffer medium. Square wave voltammetry is used to record the redox signal for DNA hybridization. Current increase upon hybridization (signal-on) evidenced that short DNA target as well as polymerase chain reaction (PCR), so called ‘real sample’ products, related to different lineages of Mycobacterium tuberculosis strain. The signal-on reached ∼40% with 1 nM of short DNA (25 mer) target, while PCR product (Africanum, EAI and Beijing strains) produced a current change of ∼20%.

Cerebellar-inspired algorithm for adaptive control of nonlinear dielectric elastomer-based artificial muscle

PubMed Central

Assaf, Tareq; Rossiter, Jonathan M.; Porrill, John

2016-01-01

Electroactive polymer actuators are important for soft robotics, but can be difficult to control because of compliance, creep and nonlinearities. Because biological control mechanisms have evolved to deal with such problems, we investigated whether a control scheme based on the cerebellum would be useful for controlling a nonlinear dielectric elastomer actuator, a class of artificial muscle. The cerebellum was represented by the adaptive filter model, and acted in parallel with a brainstem, an approximate inverse plant model. The recurrent connections between the two allowed for direct use of sensory error to adjust motor commands. Accurate tracking of a displacement command in the actuator's nonlinear range was achieved by either semi-linear basis functions in the cerebellar model or semi-linear functions in the brainstem corresponding to recruitment in biological muscle. In addition, allowing transfer of training between cerebellum and brainstem as has been observed in the vestibulo-ocular reflex prevented the steady increase in cerebellar output otherwise required to deal with creep. The extensibility and relative simplicity of the cerebellar-based adaptive-inverse control scheme suggests that it is a plausible candidate for controlling this type of actuator. Moreover, its performance highlights important features of biological control, particularly nonlinear basis functions, recruitment and transfer of training. PMID:27655667

Biaxial experimental and analytical characterization of a dielectric elastomer

NASA Astrophysics Data System (ADS)

Helal, Alexander; Doumit, Marc; Shaheen, Robert

2018-01-01

Electroactive polymers (EAPs) have emerged as a strong contender for use in low-cost efficient actuators in multiple applications especially related to biomimetic and mobile-assistive devices. Dielectric elastomers (DE), a subcategory of these smart materials, have been of particular interest due to their large achievable deformation and favourable mechanical and electro-mechanical properties. Previous work has been completed to understand the behaviour of these materials; however, their properties require further investigation to properly integrate them into real-world applications. In this study, a biaxial tensile experimental evaluation of 3M™ VHB 4905 and VHB 4910 is presented with the purpose of illustrating the elastomers' transversely isotropic mechanical behaviours. These tests were applied to both tapes for equibiaxial stretch rates ranging between 0.025 and 0.300 s-1. Subsequently, a dynamic planar biaxial visco-hyperelastic constitutive relationship was derived from a Kelvin-Voigt rheological model and the general Hooke's law for transversely isotropic materials. The model was then fitted to the experimental data to obtain three general material parameters for either tapes. The model's ability to predict tensile stress response and internal energy dissipation, with respect to experimental data, is evaluated with good agreement. The model's ability to predict variations in mechanical behaviour due to changes in kinematic variables is then illustrated for different conditions.

Current status and future prospects of power generators using dielectric elastomers

NASA Astrophysics Data System (ADS)

Chiba, Seiki; Waki, Mikio; Kornbluh, Roy; Pelrine, Ron

2011-12-01

Electroactive polymer artificial muscle (EPAM), known collectively as dielectric elastomers in the literature, has been shown to offer unique capabilities as an actuator and is now being developed for a wide variety of generator applications. EPAM has several characteristics that make it potentially well suited for wave, water current, wind, human motion, and other environmental energy harvesting systems including a high energy density allowing for minimal EPAM material quantities, high energy conversion efficiency independent of frequency of operation and non-toxic and low-cost materials not susceptible to corrosion. Experiments have been performed on push-button and heel-mounted generator devices powered by human motion, ocean wave power harvesters mounted on buoys and water turbines. While the power output levels of such demonstration devices is small, the performance of these devices has supported the potential benefits of EPAM. For example, an electrical energy conversion efficiency of over 70% was achieved with small wave heights. The ability of EPAM to produce hydrogen fuel for energy storage was also demonstrated. Because the energy conversion principle of EPAM is capacitive in nature, the performance is largely independent of size and it should eventually be possible to scale up EPAM generators to the megawatt level to address a variety of electrical power needs.

Scaling Laws of Microactuators and Potential Applications of Electroactive Polymers in MEMS

NASA Technical Reports Server (NTRS)

Liu, Chang; Bar-Cohen, Y.

1999-01-01

Besides the scale factor that distinguishes the various species, fundamentally biological muscles changes little between species, indicating a highly optimized system. Electroactive polymer actuators offer the closest resemblance to biological muscles, however besides the large actuation displacement these materials are falling short with regards to the actuation force. As improved materials are emerging it is becoming necessary to address key issues such as the need for effective electromechanical modeling and guiding parameters in scaling the actuators. In this paper, we will review the scaling laws for three major actuation mechanisms that are of relevance to micro electromechanical systems: electrostatic actuation, magnetic actuation, thermal bimetallic actuation, and piezoelectric actuation.

Failure modes in electroactive polymer thin films with elastic electrodes

NASA Astrophysics Data System (ADS)

De Tommasi, D.; Puglisi, G.; Zurlo, G.

2014-02-01

Based on an energy minimization approach, we analyse the elastic deformations of a thin electroactive polymer (EAP) film sandwiched by two elastic electrodes with non-negligible stiffness. We analytically show the existence of a critical value of the electrode voltage for which non-homogeneous solutions bifurcate from the homogeneous equilibrium state, leading to the pull-in phenomenon. This threshold strongly decreases the limit value proposed in the literature considering only homogeneous deformations. We explicitly discuss the influence of geometric and material parameters together with boundary conditions in the attainment of the different failure modes observed in EAP devices. In particular, we obtain the optimum values of these parameters leading to the maximum activation performances of the device.

Electroactive polymer-based devices for e-textiles in biomedicine.

PubMed

Carpi, Federico; De Rossi, Danilo

2005-09-01

This paper describes the early conception and latest developments of electroactive polymer (EAP)-based sensors, actuators, electronic components, and power sources, implemented as wearable devices for smart electronic textiles (e-textiles). Such textiles, functioning as multifunctional wearable human interfaces, are today considered relevant promoters of progress and useful tools in several biomedical fields, such as biomonitoring, rehabilitation, and telemedicine. After a brief outline on ongoing research and the first products on e-textiles under commercial development, this paper presents the most highly performing EAP-based devices developed by our lab and other research groups for sensing, actuation, electronics, and energy generation/storage, with reference to their already demonstrated or potential applicability to electronic textiles.

Novel neural interface for implant electrodes: improving electroactivity of polypyrrole through MWNT incorporation.

PubMed

Green, R A; Williams, C M; Lovell, N H; Poole-Warren, L A

2008-04-01

Multi-walled carbon nanotubes (MWNTs) can be incorporated into conductive polymers to produce superior materials for neural interfaces with high interfacial areas, conductivity and electrochemical stability. This paper explores the addition of MWNTs to polypyrrole (PPy) through two methods, layering and codeposition. Conductivity of PPy doped with polystyrene sulfonate (PSS), a commonly used dopant, was improved by 50% when MWNTs were layered with PPy/PSS. The film electrochemical stability was improved from 38% activity to 66% activity after 400 cycles of oxidation and reduction. Growth inhibition assays indicated that MWNTs are not growth inhibitory. The electroactive polymer-MWNT composites produced demonstrate properties that suggest they are promising candidates for biomedical electrode coatings.

Deformable membranes actuated by high mechanical power density composite electroactive polymers using tailored electric field

NASA Technical Reports Server (NTRS)

Bar-Cohen, Y.; Bhattacharya, K.

2003-01-01

The objective of the project was to develop a versatile electroactuator based on a specific class of EAP, conductive polymer, that is capable of developing high forces and displacements in both bending and linear contraction/expansion movements.

Synthesis of biodegradable and electroactive multiblock polylactide and aniline pentamer copolymer for tissue engineering applications.

PubMed

Huang, Lihong; Zhuang, Xiuli; Hu, Jun; Lang, Le; Zhang, Peibiao; Wang, Yu; Chen, Xuesi; Wei, Yen; Jing, Xiabin

2008-03-01

To obtain one biodegradable and electroactive polymer as the scaffold for tissue engineering, the multiblock copolymer PLAAP was designed and synthesized with the condensation polymerization of hydroxyl-capped poly( l-lactide) (PLA) and carboxyl-capped aniline pentamer (AP). The PLAAP copolymer exhibited excellent electroactivity, solubility, and biodegradability. At the same time, as one scaffold material, PLAAP copolymer possesses certain mechanical properties with the tensile strength of 3 MPa, tensile Young 's modulus of 32 MPa, and breaking elongation rate of 95%. We systematically studied the compatibility of PLAAP copolymer in vitro and proved that the electroactive PLAAP copolymer was innocuous, biocompatible, and helpful for the adhesion and proliferation of rat C6 cells. Moreover, the PLAAP copolymer stimulated by electrical signals was demonstrated as accelerating the differentiation of rat neuronal pheochromocytoma PC-12 cells. This biodegradable and electroactive PLAAP copolymer thus possessed the properties in favor of the long-time application in vivo as nerve repair scaffold materials in tissue engineering.

Electroactive Polymer Nanoparticles Exhibiting Photothermal Properties

PubMed Central

Cantu, Travis; Rodier, Bradley; Iszard, Zachary; Kilian, Alissa; Pattani, Varun; Walsh, Kyle; Weber, Katharina; Tunnell, James; Betancourt, Tania; Irvin, Jennifer

2016-01-01

A method for the synthesis of electroactive polymers is demonstrated, starting with the synthesis of extended conjugation monomers using a three-step process that finishes with Negishi coupling. Negishi coupling is a cross-coupling process in which a chemical precursor is first lithiated, followed by transmetallation with ZnCl2. The resultant organozinc compound can be coupled to a dibrominated aromatic precursor to give the conjugated monomer. Polymer films can be prepared via electropolymerization of the monomer and characterized using cyclic voltammetry and ultraviolet-visible-near infrared (UV-Vis-NIR) spectroscopy. Nanoparticles (NPs) are prepared via emulsion polymerization of the monomer using a two-surfactant system to yield an aqueous dispersion of the polymer NPs. The NPs are characterized using dynamic light scattering, electron microscopy, and UV-Vis-NIR-spectroscopy. Cytocompatibility of NPs is investigated using the cell viability assay. Finally, the NP suspensions are irradiated with a NIR laser to determine their effectiveness as potential materials for photothermal therapy (PTT). PMID:26780244

Electro-Active Polymer (EAP) Actuators for Planetary Applications

NASA Technical Reports Server (NTRS)

Bar-Cohen, Y.; Leary, S.; Shahinpoor, M.; Harrison, J. O.; Smith, J.

1999-01-01

NASA is seeking to reduce the mass, size, consumed power, and cost of the instrumentation used in its future missions. An important element of many instruments and devices is the actuation mechanism and electroactive polymers (EAP) are offering an effective alternative to current actuators. In this study, two families of EAP materials were investigated, including bending ionomers and longitudinal electrostatically driven elastomers. These materials were demonstrated to effectively actuate manipulation devices and their performance is being enhanced in this on-going study. The recent observations are reported in this paper, include the operation of the bending-EAP at conditions that exceed the harsh environment on Mars, and identify the obstacles that its properties and characteristics are posing to using them as actuators. Analysis of the electrical characteristics of the ionomer EAP showed that it is a current driven material rather than voltage driven and the conductivity distribution on the surface of the material greatly influences the bending performance. An accurate equivalent circuit modeling of the ionomer EAP performance is essential for the design of effective drive electronics. The ionomer main limitations are the fact that it needs to be moist continuously and the process of electrolysis that takes place during activation. An effective coating technique using a sprayed polymer was developed extending its operation in air from a few minutes to about four months. The coating technique effectively forms the equivalent of a skin to protect the moisture content of the ionomer. In parallel to the development of the bending EAP, the development of computer control of actuated longitudinal EAP has been pursued. An EAP driven miniature robotic arm was constructed and it is controlled by a MATLAB code to drop and lift the arm and close and open EAP fingers of a 4-finger gripper. Keywords: Miniature Robotics, Electroactive Polymers, Electroactive Actuators, EAP Materials

Novel Electroactive Polymers as Environmentally Compliant Coatings for Corrosion Control

DTIC Science & Technology

2006-02-03

Gravametric Analysis (TGA) and Differential Scanning Calorimetry (DSC), respectively. In this work the polymers were characterized by cyclic voltametry ...or less. The Temperature Step / Frequency Sweep method was employed where data were collected from –40 to 100°C and 0.1-100 Hz at a resolution of

Adaptive lenses using transparent dielectric elastomer actuators

NASA Astrophysics Data System (ADS)

Shian, Samuel; Diebold, Roger; Clarke, David

2013-03-01

Variable focal lenses, used in a vast number of applications such as endoscope, digital camera, binoculars, information storage, communication, and machine vision, are traditionally constructed as a lens system consisting of solid lenses and actuating mechanisms. However, such lens system is complex, bulky, inefficient, and costly. Each of these shortcomings can be addressed using an adaptive lens that performs as a lens system. In this presentation, we will show how we push the boundary of adaptive lens technology through the use of a transparent electroactive polymer actuator that is integral to the optics. Detail of our concepts and lens construction will be described as well as electromechanical and optical performances. Preliminary data indicate that our adaptive lens prototype is capable of varying its focus by more than 100%, which is higher than that of human eyes. Furthermore, we will show how our approach can be used to achieve certain controls over the lens characteristics such as adaptive aberration and optical axis, which are difficult or impossible to achieve in other adaptive lens configurations.

Difference between electrostriction kinetics, and mechanical response of segmented polyurethane-based EAP

NASA Astrophysics Data System (ADS)

Jomaa, M. H.; Seveyrat, L.; Perrin, V.; Lebrun, L.; Masenelli-Varlot, K.; Diguet, Gildas; Cavaille, J. Y.

2017-03-01

Among the key parameters, which must be taken into account for the choice of actuators used as electrical to mechanical energy converters, the response to a step function and/or the frequency dependence of this response is extremely important. For polymeric actuators and more generally for electroactive polymers, three mechanisms can be at the origin of energy losses, namely dielectric relaxations, viscoelastic relaxations and possible electrical conductivity. In a previous paper, we studied the electrical behavior of segmented polyurethanes with different weight fractions of hard (MDI-BDO) and soft (PTMO) segments. They were shown to exhibit three main mechanisms, namely, from the fastest to the slowest, a secondary or β-relaxation, the main or α-relaxation associated with the glass-rubber transition of the soft phase, and finally, their electrical conductivity. In the present work, we present the general viscoelastic response (as measured through mechanical spectrometry) of the same polyurethanes and their respective time dependent electrostriction responses, and compare it with the relaxation characteristic times of electrical and mechanical spectroscopy data.

A new bistable electroactive polymer for prolonged cycle lifetime of refreshable Braille displays

NASA Astrophysics Data System (ADS)

Ren, Zhi; Niu, Xiaofan; Chen, Dustin; Hu, Wei; Pei, Qibing

2014-03-01

ABSTRACT: Bistable electroactive polymers (BSEP) amalgamating electrically induced large-strain actuation and shape memory effect present a unique opportunity for refreshable Braille displays. A new BSEP material with long-chain crosslinkers to achieve prolonged cycle lifetime of refreshable Braille displays is reported here. The modulus of the BSEP material decreases by more than three orders of magnitude from a rigid, plastic state to a rubbery state when heated above the polymer's glass transition temperature. In its rubbery state, the polymer film can be electrically actuated to buckle convexly when a high voltage is applied across a circular active area. Modifying the concentration of long-chain crosslinkers in the polymer allows not only for fine-tuning of the polymer's glass transition temperature and elasticity in the rubbery state, but also enhancement of the actuation stability. For a raised height of 0.4 mm by a Braille dot with a 1.3 mm diameter, actuation can be repeated over 2000 cycles at 70°C in the rubbery state. The actuated dome shape can be fixed by cooling the polymer below the glass transition temperature. This refreshable rigid-to-rigid actuation simultaneously provides large-strain actuation and large force support. Devices capable of displaying Braille characters over a page-size area consisting of 324 Braille cells have been fabricated.

Electrohydrodynamic pressure enhanced by free space charge for electrically induced structure formation with high aspect ratio.

PubMed

Tian, Hongmiao; Wang, Chunhui; Shao, Jinyou; Ding, Yucheng; Li, Xiangming

2014-10-28

Electrically induced structure formation (EISF) is an interesting and unique approach for generating a microstructured duplicate from a rheological polymer by a spatially modulated electric field induced by a patterned template. Most of the research on EISF have so far used various dielectric polymers (with an electrical conductivity smaller than 10(-10) S/m that can be considered a perfect dielectric), on which the electric field induces a Maxwell stress only due to the dipoles (or bounded charges) in the polymer molecules, leading to a structure with a small aspect ratio. This paper presents a different approach for improving the aspect ratio allowed in EISF by doping organic salt into the perfect dielectric polymer, i.e., turning the perfect dielectric into a leaky dielectric, considering the fact that the free space charges enriched in the leaky dielectric polymer can make an additional contribution to the Maxwell stress, i.e., electrohydrodynamic pressure, which is desirable for high aspect ratio structuring. Our numerical simulations and experimental tests have shown that a leaky dielectric polymer, with a small conductivity comparable to that of deionized water, can be much more effective at being electrohydrodynamically deformed into a high aspect ratio in comparison with a perfect dielectric polymer when both of them have roughly the same dielectric constant.

Development of polypyrrole based solid-state on-chip microactuators using photolithography

NASA Astrophysics Data System (ADS)

Zhong, Yong; Lundemo, Staffan; Jager, Edwin W. H.

2018-07-01

There is a need for soft microactuators, especially for biomedical applications. We have developed a microfabrication process to create such soft, on-chip polymer based microactuators that can operate in air. The on-chip microactuators were fabricated using standard photolithographic techniques and wet etching, combined with special designed process to micropattern the electroactive polymer polypyrrole that drives the microactuators. By immobilizing a UV-patternable gel containing a liquid electrolyte on top of the electroactive polypyrrole layer, actuation in air was achieved although with reduced movement. Further optimization of the processing is currently on-going. The result shows the possibility to batch fabricate complex microsystems such as microrobotics and micromanipulators based on these solid-state on-chip microactuators using microfabrication methods including standard photolithographic processes.

Ionic electroactive polymer actuators as active microfluidic mixers

DOE PAGES

Meis, Catherine; Montazami, Reza; Hashemi, Nastaran

2015-11-06

On-chip sample processing is integral to the continued development of lab-on-a-chip devices for various applications. An active microfluidic mixer prototype is proposed using ionic electroactive polymer actuators (IEAPAs) as artificial cilia. A proof-of-concept experiment was performed in which the actuators were shown to produce localized flow pattern disruptions in the laminar flow regime. Suggestions for further engineering and optimization of a scaled-down, complete device are provided. Furthermore, the device in its current state of development necessitates further engineering, the use of IEAPAs addresses issues currently associated with the use of electromechanical actuators as active microfluidic mixers and may prove tomore » be a useful alternative to other similar materials.« less

Recent Progress on Ferroelectric Polymer-Based Nanocomposites for High Energy Density Capacitors: Synthesis, Dielectric Properties, and Future Aspects.

PubMed

Prateek; Thakur, Vijay Kumar; Gupta, Raju Kumar

2016-04-13

Dielectric polymer nanocomposites are rapidly emerging as novel materials for a number of advanced engineering applications. In this Review, we present a comprehensive review of the use of ferroelectric polymers, especially PVDF and PVDF-based copolymers/blends as potential components in dielectric nanocomposite materials for high energy density capacitor applications. Various parameters like dielectric constant, dielectric loss, breakdown strength, energy density, and flexibility of the polymer nanocomposites have been thoroughly investigated. Fillers with different shapes have been found to cause significant variation in the physical and electrical properties. Generally, one-dimensional and two-dimensional nanofillers with large aspect ratios provide enhanced flexibility versus zero-dimensional fillers. Surface modification of nanomaterials as well as polymers adds flavor to the dielectric properties of the resulting nanocomposites. Nowadays, three-phase nanocomposites with either combination of fillers or polymer matrix help in further improving the dielectric properties as compared to two-phase nanocomposites. Recent research has been focused on altering the dielectric properties of different materials while also maintaining their superior flexibility. Flexible polymer nanocomposites are the best candidates for application in various fields. However, certain challenges still present, which can be solved only by extensive research in this field.

High-Voltage Polymers for High-Power Supercapacitors. Version 1

DTIC Science & Technology

2006-05-30

affect the supercapacitor’s performance. Subsequently, our efforts focused on fabricating polymers with high oxidation potentials to increase the power...including spin activation with out significant modifications. Electroactive polymers such as polythiophene, polyacetylene, or polyaniline can be...potentials in excess of 2 V for facile polymerization. In the present case, the triaryl ammine functionality of 2 and 3 is oxidized at the low

Dielectric studies on PEG-LTMS based polymer composites

NASA Astrophysics Data System (ADS)

Patil, Ravikumar V.; Praveen, D.; Damle, R.

2018-02-01

PEG LTMS based polymer composites were prepared and studied for dielectric constant variation with frequency and temperature as a potential candidate with better dielectric properties. Solution cast technique is used for the preparation of polymer composite with five different compositions. Samples show variation in dielectric constant with frequency and temperature. Dielectric constant is large at low frequencies and higher temperatures. Samples with larger space charges have shown larger dielectric constant. The highest dielectric constant observed was about 29244 for PEG25LTMS sample at 100Hz and 312 K.

Flexible Dielectric Nanocomposites with Ultrawide Zero-Temperature Coefficient Windows for Electrical Energy Storage and Conversion under Extreme Conditions.

PubMed

Shehzad, Khurram; Xu, Yang; Gao, Chao; Li, Hanying; Dang, Zhi-Min; Hasan, Tawfique; Luo, Jack; Duan, Xiangfeng

2017-03-01

Polymer dielectrics offer key advantages over their ceramic counterparts such as flexibility, scalability, low cost, and high breakdown voltages. However, a major drawback that limits more widespread application of polymer dielectrics is their temperature-dependent dielectric properties. Achieving dielectric constants with low/zero-temperature coefficient (L/0TC) over a broad temperature range is essential for applications in diverse technologies. Here, we report a hybrid filler strategy to produce polymer composites with an ultrawide L/0TC window of dielectric constant, as well as a significantly enhanced dielectric value, maximum energy storage density, thermal conductivity, and stability. By creating a series of percolative polymer composites, we demonstrated hybrid carbon filler based composites can exhibit a zero-temperature coefficient window of 200 °C (from -50 to 150 °C), the widest 0TC window for all polymer composite dielectrics reported to date. We further show the electric and dielectric temperature coefficient of the composites is highly stable against stretching and bending, even under AC electric field with frequency up to 1 MHz. We envision that our method will push the functional limits of polymer dielectrics for flexible electronics in extreme conditions such as in hybrid vehicles, aerospace, power electronics, and oil/gas exploration.

Electroactive BaTiO3 nanoparticle-functionalized fibrous scaffolds enhance osteogenic differentiation of mesenchymal stem cells

PubMed Central

Li, Yiping; Dai, Xiaohan; Bai, Yunyang; Liu, Yun; Wang, Yuehong; Liu, Ousheng; Yan, Fei; Tang, Zhangui; Zhang, Xuehui; Deng, Xuliang

2017-01-01

It has been proven that the surface topographic cues of fiber arrangement can induce osteogenic differentiation of mesenchymal stem cells. However, this effect alone is weak and insufficient to meet the needs of regenerative medicine. In this work, electroactivity concept was introduced to enhance the osteoinductivity of fibrous scaffolds. The randomly oriented and aligned electroactive fibrous scaffolds of poly-(l-lactic acid) (PLLA) with incorporation of ferroelectric ceramic BaTiO3 (BTO) nanoparticles (NPs) were fabricated by electrospinning. Physicochemical properties, including fiber morphology, microstructure, composition, thermal stability, surface roughness, and surface wettability, of these fibrous scaffolds were studied. The dielectric properties of the scaffolds were evaluated. The results showed that the randomly oriented BTO/PLLA composite fibrous scaffolds had the highest dielectric permittivity of 1.19, which is of the same order of magnitude as the natural bone. The combined effects of fiber orientation and electrical activity on the osteogenic responses of bone marrow mesenchymal stem cells (BM-MSCs) were specifically investigated. Randomly oriented composite fibrous scaffolds significantly promoted polygonal spreading and encouraged early osteogenic differentiation in BM-MSCs, whereas aligned composite fibrous scaffolds promoted cell elongation and discouraged osteogenic differentiation. These results evidenced that randomly fiber orientation and biomimetic electric activity have combining effects on osteogenic differentiation of BM-MSCs. Our findings indicate that coupling effects of multi-physical properties should be paid more attention to mimic the microenvironment for enhancing osteogenic differentiation of BM-MSCs. PMID:28603415

Synthesis and Characterization of Electroactive Polymers Based on Pyrrole

DTIC Science & Technology

1989-10-01

169. 5. E.T. Kang, K.G. Neoh and H.C. Ti, Solid State Communications, 1986, 60, 457. 6. Osamu Niwa, Masami Kakuchi, and Toshiaki Tamamura, 7...1987, 18, 49. 8. Keiko Koga, Takao lino, Shigeyuki Ueta, and Motowo Takayanagi , Polymer. Journal, 1989, 21, 499. 9. S.E. Lindesey and G.B. Street

Constitutive equations for an electroactive polymer

NASA Astrophysics Data System (ADS)

Tixier, Mireille; Pouget, Joël

2016-07-01

Ionic electroactive polymers can be used as sensors or actuators. For this purpose, a thin film of polyelectrolyte is saturated with a solvent and sandwiched between two platinum electrodes. The solvent causes a complete dissociation of the polymer and the release of small cations. The application of an electric field across the thickness results in the bending of the strip and vice versa. The material is modeled by a two-phase continuous medium. The solid phase, constituted by the polymer backbone inlaid with anions, is depicted as a deformable porous media. The liquid phase is composed of the free cations and the solvent (usually water). We used a coarse grain model. The conservation laws of this system have been established in a previous work. The entropy balance law and the thermodynamic relations are first written for each phase and then for the complete material using a statistical average technique and the material derivative concept. One deduces the entropy production. Identifying generalized forces and fluxes provides the constitutive equations of the whole system: the stress-strain relations which satisfy a Kelvin-Voigt model, generalized Fourier's and Darcy's laws and the Nernst-Planck equation.

Electroactive Ionic Soft Actuators with Monolithically Integrated Gold Nanocomposite Electrodes.

PubMed

Yan, Yunsong; Santaniello, Tommaso; Bettini, Luca Giacomo; Minnai, Chloé; Bellacicca, Andrea; Porotti, Riccardo; Denti, Ilaria; Faraone, Gabriele; Merlini, Marco; Lenardi, Cristina; Milani, Paolo

2017-06-01

Electroactive ionic gel/metal nanocomposites are produced by implanting supersonically accelerated neutral gold nanoparticles into a novel chemically crosslinked ion conductive soft polymer. The ionic gel consists of chemically crosslinked poly(acrylic acid) and polyacrylonitrile networks, blended with halloysite nanoclays and imidazolium-based ionic liquid. The material exhibits mechanical properties similar to that of elastomers (Young's modulus ≈ 0.35 MPa) together with high ionic conductivity. The fabrication of thin (≈100 nm thick) nanostructured compliant electrodes by means of supersonic cluster beam implantation (SCBI) does not significantly alter the mechanical properties of the soft polymer and provides controlled electrical properties and large surface area for ions storage. SCBI is cost effective and suitable for the scaleup manufacturing of electroactive soft actuators. This study reports the high-strain electromechanical actuation performance of the novel ionic gel/metal nanocomposites in a low-voltage regime (from 0.1 to 5 V), with long-term stability up to 76 000 cycles with no electrode delamination or deterioration. The observed behavior is due to both the intrinsic features of the ionic gel (elasticity and ionic transport capability) and the electrical and morphological features of the electrodes, providing low specific resistance (<100 Ω cm -2 ), high electrochemical capacitance (≈mF g -1 ), and minimal mechanical stress at the polymer/metal composite interface upon deformation. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Improved dielectric constant and breakdown strength of γ-phase dominant super toughened polyvinylidene fluoride/TiO2 nanocomposite film: an excellent material for energy storage applications and piezoelectric throughput

NASA Astrophysics Data System (ADS)

Mehebub Alam, Md; Ghosh, Sujoy Kumar; Sarkar, Debabrata; Sen, Shrabanee; Mandal, Dipankar

2017-01-01

Titanium dioxide (TiO2) nanoparticles (NPs) embedded γ-phase containing polyvinylidene fluoride (PVDF) nanocomposite (PNC) film turns to an excellent material for energy storage application due to an increased dielectric constant (32 at 1 kHz), enhanced electric breakdown strength (400 MV m-1). It also exhibits a high energy density of 4 J cm-3 which is 25 times higher than that of virgin PVDF. 98% of the electroactive γ-phase has been acheived by the incorporation of TiO2 NPs and the resulting PNC behaves like a super-toughened material due to a dramatic improvement (more than 80%) in the tensile strength. Owing to their electroactive nature and extraordinary mechanical properties, PNC films have a strong ability to fabricate the piezoelectric nanogenerators (PNGs) that have recently been an area of focus regarding mechanical energy harvesting. The feasibility of piezoelectric voltage generation from PNGs is demostrated under the rotating fan that also promises further utility such as rotational speed (RPM) determination.

Electroactive polymer-peptide conjugates for adhesive biointerfaces.

PubMed

Maione, Silvana; Gil, Ana M; Fabregat, Georgina; Del Valle, Luis J; Triguero, Jordi; Laurent, Adele; Jacquemin, Denis; Estrany, Francesc; Jiménez, Ana I; Zanuy, David; Cativiela, Carlos; Alemán, Carlos

2015-10-15

Electroactive polymer-peptide conjugates have been synthesized by combining poly(3,4-ethylenedioxythiophene), a polythiophene derivative with outstanding properties, and an Arg-Gly-Asp (RGD)-based peptide in which Gly has been replaced by an exotic amino acid bearing a 3,4-ethylenedioxythiophene ring in the side chain. The incorporation of the peptide at the ends of preformed PEDOT chains has been corroborated by both FTIR and X-ray photoelectron spectroscopy. Although the morphology and topology are not influenced by the incorporation of the peptide at the ends of PEDOT chains, this process largely affects other surface properties. Thus, the wettability of the conjugates is considerably higher than that of PEDOT, independently of the synthetic strategy, whereas the surface roughness only increases when the conjugate is obtained using a competing strategy (i.e. growth of the polymer chains against termination by end capping). The electrochemical activity of the conjugates has been found to be higher than that of PEDOT, evidencing the success of the polymer-peptide links designed by chemical similarity. Density functional theory calculations have been used not only to ascertain the conformational preferences of the peptide but also to interpret the electronic transitions detected by UV-vis spectroscopy. Electroactive surfaces prepared using the conjugates displayed the higher bioactivities in terms of cell adhesion, with the relative viabilities being dependent on the roughness, wettability and electrochemical activity of the conjugate. In addition to the influence of the peptide fragment in the initial cell attachment and subsequent cell spreading and survival, the results indicate that PEDOT promotes the exchange of ions at the conjugate-cell interface.

Norbornylene-based polymer systems for dielectric applications

DOEpatents

Dirk, Shawn M [Albuquerque, NM; Wheeler, David R [Albuquerque, NM

2012-07-17

A capacitor having at least one electrode pair being separated by a dielectric component, with the dielectric component being made of a polymer such as a norbornylene-containing polymer with a dielectric constant greater than 3 and a dissipation factor less than 0.1 where the capacitor has an operating temperature greater than 100.degree. C. and less than 170.degree. C.

Synthesis and surface characterization of electroactive conducting polymers and polyurethane coatings

NASA Astrophysics Data System (ADS)

Vang, Chur Kalec

The direct electrodeposition of electroactive conducting polymers (ECPs) on active metals such as iron, steel, and aluminum is complicated by the concomitant metal oxidation that occurs at the positive potentials required for polymer formation. In the case of aluminum and its alloys, the oxide layer that forms is an insulator that blocks electron transfer and impedes polymer formation and deposition. As a result, only patchy, nonuniform polymer films are obtained. Electron transfer mediation is a well-known technique for overcoming kinetic limitations of electron transfer at metal electrodes. In this dissertation, we report the use of electron transfer mediation for the direct electrodeposition of polypyrrole onto aluminum and onto Al 2024-T3 alloy. The first few chapters focus on the electrochemistry and use of Tiron RTM (4,5-dihydroxy-1,3-benzenedisulfonic acid disodium salt) as the mediator. Electroactive conductive polymers (ECPs) were also being investigated for corrosion protection of Al alloys, with a view toward replacement of chromate-based coating systems. The use of electrochemical methods clearly indicated that the electrodeposited Ppy coatings had altered the corrosion behavior of the Al alloy. Degradation mechanisms for self-priming (unicoat), high-gloss, and fluorinated polyurethane aircraft coatings exposed to QUV/H2O radiation were carried out using linear and step-scan photoacoustic (S2-PA) FTIR spectroscopy (Chapters 7--9). FTIR spectroscopic analysis indicated that, as the depth of sampling increased from film-air to film-substrate, an increase of free carbonyl components was observed. These free carbonyl groups are indicative of polyurethane components. Exposure of the polyurethane coating to prolonged periods of extreme weathering conditions indicated a loss of both polyurethane/polyurea components at the air interface, which has lead to an increase of disordered hydrogen-bonding formations. Contact angle measurement further indicated that as exposure time increases, an increase in contact angle measurements was observed. Therefore, both FTIR spectroscopic and contact angle results concluded that although chemical degradation has taken place, the overall integrity of the coating still remains.

Soft Ionic Electroactive Polymer Actuators with Tunable Non-Linear Angular Deformation

PubMed Central

Hong, Wangyujue; Almomani, Abdallah; Chen, Yuanfen; Jamshidi, Reihaneh; Montazami, Reza

2017-01-01

The most rational approach to fabricate soft robotics is the implementation of soft actuators. Conventional soft electromechanical actuators exhibit linear or circular deformation, based on their design. This study presents the use of conjugated polymers, Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) to locally vary ion permeability of the ionic electroactive polymer actuators and manipulate ion motion through means of structural design to realize intrinsic angular deformation. Such angular deformations are closer to biomimetic systems and have potential applications in bio-robotics. Electrochemical studies reveal that the mechanism of actuation is mainly associated with the charging of electric double layer (EDL) capacitors by ion accumulation and the PEDOT:PSS layer’s expansion by ion interchange and penetration. Dependence of actuator deformation on structural design is studied experimentally and conclusions are verified by analytical and finite element method modeling. The results suggest that the ion-material interactions are considerably dominated by the design of the drop-cast PEDOT:PSS on Nafion. PMID:28773036

Soft Ionic Electroactive Polymer Actuators with Tunable Non-Linear Angular Deformation.

PubMed

Hong, Wangyujue; Almomani, Abdallah; Chen, Yuanfen; Jamshidi, Reihaneh; Montazami, Reza

2017-06-21

The most rational approach to fabricate soft robotics is the implementation of soft actuators. Conventional soft electromechanical actuators exhibit linear or circular deformation, based on their design. This study presents the use of conjugated polymers, Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) to locally vary ion permeability of the ionic electroactive polymer actuators and manipulate ion motion through means of structural design to realize intrinsic angular deformation. Such angular deformations are closer to biomimetic systems and have potential applications in bio-robotics. Electrochemical studies reveal that the mechanism of actuation is mainly associated with the charging of electric double layer (EDL) capacitors by ion accumulation and the PEDOT:PSS layer's expansion by ion interchange and penetration. Dependence of actuator deformation on structural design is studied experimentally and conclusions are verified by analytical and finite element method modeling. The results suggest that the ion-material interactions are considerably dominated by the design of the drop-cast PEDOT:PSS on Nafion.

A review study of (bio)sensor systems based on conducting polymers.

PubMed

Ates, Murat

2013-05-01

This review article concentrates on the electrochemical biosensor systems with conducting polymers. The area of electro-active polymers confined to different electrode surfaces has attracted great attention. Polymer modified carbon substrate electrodes can be designed through polymer screening to provide tremendous improvements in sensitivity, selectivity, stability and reproducibility of the electrode response to detect a variety of analytes. The electro-active films have been used to entrap different enzymes and/or proteins at the electrode surface, but without obvious loss of their bioactivity for the development of biosensors. Electropolymerization is a well-known technique used to immobilize biomaterials to the modified electrode surface. Polymers might be covalently bonding to enzymes or proteins; therefore, thickness, permeation and charge transport characteristics of the polymeric films can be easily and precisely controlled by modulating the electrochemical parameters for various electrochemical techniques, such as chronoamperometry, chronopotentiometry, cyclic voltammetry, and differential pulse voltammetry. This review article is divided into three main parts as given in the table of contents related to the immobilization process of some important conducting polymers, polypyrrole, polythiophene, poly(3,4-ethylenedioxythiophene), polycarbazole, polyaniline, polyphenol, poly(o-phenylenediamine), polyacetylene, polyfuran and their derivatives. A total of 216 references are cited in this review article. The literature reviewed covers a 7 year period beginning from 2005. Copyright © 2013 Elsevier B.V. All rights reserved.

Electrostrictive Polymers for Mechanical-to-Electrical Energy Harvesting

DTIC Science & Technology

usable electrical energy. Piezoelectric ceramic-based devices have long been used in energy harvesting for converting mechanical motion to electrical ...typically softer and more flexible, the translated electrical energy output is considerably higher under the same mechanical force. Currently...investigations in using electroactive polymers for energy harvesting, and mechanical-to- electrical energy conversion, are beginning to show potential for

Polymer Nanofiber Based Reversible Nano-Switch/Sensor Diode (Nanosssd) Device

NASA Technical Reports Server (NTRS)

Theofylaktos, Onoufrios (Inventor); Meador, Michael A. (Inventor); Miranda, Felix A. (Inventor); Pinto, Nicholas (Inventor); Mueller, Carl H. (Inventor); Santos-Perez, Javier (Inventor)

2017-01-01

A nanostructure device is provided and performs dual functions as a nano-switching/sensing device. The nanostructure device includes a doped semiconducting substrate, an insulating layer disposed on the doped semiconducting substrate, an electrode formed on the insulating layer, and at least one polymer nanofiber deposited on the electrode. The at least one polymer nanofiber provides an electrical connection between the electrode and the substrate and is the electroactive element in the device.

Ionic electroactive hybrid transducers

NASA Astrophysics Data System (ADS)

Akle, Barbar J.; Bennett, Matthew D.; Leo, Donald J.

2005-05-01

Ionic electroactive actuators have received considerable attention in the past ten years. Ionic electroactive polymers, sometimes referred to as artificial muscles, have the ability to generate large bending strain and moderate stress at low applied voltages. Typical types of ionic electroactive polymer transducers include ionic polymers, conducting polymers, and carbon nanotubes. Preliminary research combining multiple types of materials proved to enhance certain transduction properties such as speed of response, maximum strain, or quasi-static actuation. Recently it was demonstrated that ionomer-ionic liquid transducers can operate in air for long periods of time (>250,000 cycles) and showed potential to reduce or eliminate the back-relaxation issue associated with ionomeric polymers. In addition, ionic liquids have higher electrical stability window than those operated with water as the solvent thereby increasing the maximum strain that the actuator can produce. In this work, a new technique developed for plating metal particulates on the surface of ionomeric materials is applied to the development of hybrid transducers that incorporate carbon nanotubes and conducting polymers as electrode materials. The new plating technique, named the direct assembly process, consists of mixing a conducting powder with an ionomer solution. This technique has demonstrated improved response time and strain output as compared to previous methods. Furthermore, the direct assembly process is less costly to implement than traditional impregnation-reduction methods due to less dependence on reducing agents, it requires less time, and is easier to implement than other processes. Electrodes applied using this new technique of mixing RuO2 (surface area 45~65m2/g) particles and Nafion dispersion provided 5x the displacement and 10x the force compared to a transducer made with conventional methods. Furthermore, the study illustrated that the response speed of the transducer is optimized by varying the vol% of metal in the electrode. For RuO2, the optimal loading was approximately 45%. This study shows that carbon nanotubes electrodes have an optimal performance at loadings around 30 vol%, while PANI electrodes are optimized at 95 vol%. Due to low percolation threshold, carbon nanotubes actuators perform better at lower loading than other conducting powders. The addition of nanotubes to the electrode tends to increase both the strain rate and the maximum strain of the hybrid actuator. SWNT/RuO2 hybrid transducer has a strain rate of 2.5%/sec, and a maximum attainable peak-to-peak strain of 9.38% (+/- 2V). SWNT/PANI hybrid also increased both strain and strain rate but not as significant as with RuO2. PANI/RuO2 actuator had an overwhelming back relaxation.

Biologically inspired toys using artificial muscles

NASA Technical Reports Server (NTRS)

Bar-Cohen, Y.

2001-01-01

Recent developments in electroactive polymers, so-called artificial muscles, could one day be used to make bionics possible. Meanwhile, as this technology evolves novel mechanisms are expected to emerge that are biologically inspired.

Thermally switchable dielectrics

DOEpatents

Dirk, Shawn M.; Johnson, Ross S.

2013-04-30

Precursor polymers to conjugated polymers, such as poly(phenylene vinylene), poly(poly(thiophene vinylene), poly(aniline vinylene), and poly(pyrrole vinylene), can be used as thermally switchable capacitor dielectrics that fail at a specific temperature due to the non-conjugated precursor polymer irreversibly switching from an insulator to the conjugated polymer, which serves as a bleed resistor. The precursor polymer is a good dielectric until it reaches a specific temperature determined by the stability of the leaving groups. Conjugation of the polymer backbone at high temperature effectively disables the capacitor, providing a `built-in` safety mechanism for electronic devices.

Numerical modeling of electroactive polymer mirrors for space applications

NASA Technical Reports Server (NTRS)

Bao, X.; Bar-Cohen, Y.; Chang, Z.; Sherrit, S.

2003-01-01

A controllable mirror made of single-layer EAP mirror is proposed in this paper. An analytical solution of required voltage distribution for forming a parabolic mirror from a planar film is presented.

Biologically Inspired Technology Using Electroactive Polymers (EAP)

NASA Technical Reports Server (NTRS)

Bar-Cohen, Yoseph

2006-01-01

Evolution allowed nature to introduce highly effective biological mechanisms that are incredible inspiration for innovation. Humans have always made efforts to imitate nature's inventions and we are increasingly making advances that it becomes significantly easier to imitate, copy, and adapt biological methods, processes and systems. This brought us to the ability to create technology that is far beyond the simple mimicking of nature. Having better tools to understand and to implement nature's principles we are now equipped like never before to be inspired by nature and to employ our tools in far superior ways. Effectively, by bio-inspiration we can have a better view and value of nature capability while studying its models to learn what can be extracted, copied or adapted. Using electroactive polymers (EAP) as artificial muscles is adding an important element to the development of biologically inspired technologies.

Time-dependence of the electromechanical bending actuation observed in ionic-electroactive polymers

NASA Astrophysics Data System (ADS)

Bass, Patrick S.; Zhang, Lin; Cheng, Z.-Y.

The characteristics of the electromechanical response observed in an ionic-electroactive polymer (i-EAP) are represented by the time (t) dependence of its bending actuation (y). The electromechanical response of a typical i-EAP — poly(ethylene oxide) (PEO) doped with lithium perchlorate (LP) — is studied. The shortcomings of all existing models describing the electromechanical response obtained in i-EAPs are discussed. A more reasonable model: y=ymaxe-τ/t is introduced to characterize this time dependence for all i-EAPs. The advantages and correctness of this model are confirmed using results obtained in PEO-LP actuators with different LP contents and at different temperatures. The applicability and universality of this model are validated using the reported results obtained from two different i-EAPs: one is Flemion and the other is polypyrrole actuators.

Newton Output Blocking Force under Low-Voltage Stimulation for Carbon Nanotube-Electroactive Polymer Composite Artificial Muscles.

PubMed

Chen, I-Wen Peter; Yang, Ming-Chia; Yang, Chia-Hui; Zhong, Dai-Xuan; Hsu, Ming-Chun; Chen, YiWen

2017-02-15

This is a study on the development of carbon nanotube-based composite actuators using a new ionic liquid-doped electroactive ionic polymer. For scalable production purposes, a simple hot-pressing method was used. Carbon nanotube/ionic liquid-Nafion/carbon nanotube composite films were fabricated that exhibited a large output blocking force and a stable cycling life with low alternating voltage stimuli in air. Of particular interest and importance, a blocking force of 1.5 N was achieved at an applied voltage of 6 V. Operational durability was confirmed by testing in air for over 30 000 cycles (or 43 h). The superior actuation performance of the carbon nanotube/ionic liquid-Nafion/carbon nanotube composite, coupled with easy manufacturability, low driving voltage, and reliable operation, promises great potential for artificial muscle and biomimetic applications.

A Review: Origins of the Dielectric Properties of Proteins and Potential Development as Bio-Sensors

PubMed Central

Bibi, Fabien; Villain, Maud; Guillaume, Carole; Sorli, Brice; Gontard, Nathalie

2016-01-01

Polymers can be classified as synthetic polymers and natural polymers, and are often characterized by their most typical functions namely their high mechanical resistivity, electrical conductivity and dielectric properties. This bibliography report consists in: (i) Defining the origins of the dielectric properties of natural polymers by reviewing proteins. Despite their complex molecular chains, proteins present several points of interest, particularly, their charge content conferring their electrical and dielectric properties; (ii) Identifying factors influencing the dielectric properties of protein films. The effects of vapors and gases such as water vapor, oxygen, carbon dioxide, ammonia and ethanol on the dielectric properties are put forward; (iii) Finally, potential development of protein films as bio-sensors coated on electronic devices for detection of environmental changes particularly humidity or carbon dioxide content in relation with dielectric properties variations are discussed. As the study of the dielectric properties implies imposing an electric field to the material, it was necessary to evaluate the impact of frequency on the polymers and subsequently on their structure. Characterization techniques, on the one hand dielectric spectroscopy devoted for the determination of the glass transition temperature among others, and on the other hand other techniques such as infra-red spectroscopy for structure characterization as a function of moisture content for instance are also introduced. PMID:27527179

Mechanism of the dielectric enhancement in polymer-alumina nano-particle composites

NASA Astrophysics Data System (ADS)

Jacob, Rebecca; Jacob, Anne Pavitra; Mainwaring, David E.

2009-09-01

Polymer-alumina nano-composites with enhanced dielectric properties as a possibility to enable the miniaturization of devices have been reported. The enhancement of dielectric properties was found to be unique to the polymer. In the present work, the mechanism of the dielectric enhancement is established by performing ab initio molecular orbital calculations in order to study the molecular interactions in the interfacial region between the alumina-nano-particle surface and the polymer medium. The calculations predict the existence of strong electrostatic attraction between the positive charge on the aluminium of the alumina clusters and the negative charge of the oxygens of the polymer at the polymer-nano-particle interface resulting in an increase in the dipole moment and the polarization of the system leading to enhanced dielectric properties. The oxygen thus plays a dual role by involving in covalent bonding with the polymer chain and electrostatic bonding interactions with the alumina nano-particles. The unique structure of the polymer provides the highly electronegative oxygens, as carbonyl groups or ether linkages in conjugation with aromatic rings in an extended polymer chain system, facilitating this type of bonding at the interface.

Biocompatible, Biodegradable, and Electroactive Polyurethane-Urea Elastomers with Tunable Hydrophilicity for Skeletal Muscle Tissue Engineering.

PubMed

Chen, Jing; Dong, Ruonan; Ge, Juan; Guo, Baolin; Ma, Peter X

2015-12-30

It remains a challenge to develop electroactive and elastic biomaterials to mimic the elasticity of soft tissue and to regulate the cell behavior during tissue regeneration. We designed and synthesized a series of novel electroactive and biodegradable polyurethane-urea (PUU) copolymers with elastomeric property by combining the properties of polyurethanes and conducting polymers. The electroactive PUU copolymers were synthesized from amine capped aniline trimer (ACAT), dimethylol propionic acid (DMPA), polylactide, and hexamethylene diisocyanate. The electroactivity of the PUU copolymers were studied by UV-vis spectroscopy and cyclic voltammetry. Elasticity and Young's modulus were tailored by the polylactide segment length and ACAT content. Hydrophilicity of the copolymer films was tuned by changing DMPA content and doping of the copolymer. Cytotoxicity of the PUU copolymers was evaluated by mouse C2C12 myoblast cells. The myogenic differentiation of C2C12 myoblasts on copolymer films was also studied by analyzing the morphology of myotubes and relative gene expression during myogenic differentiation. The chemical structure, thermal properties, surface morphology, and processability of the PUU copolymers were characterized by NMR, FT-IR, gel permeation chromatography (GPC), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and solubility testing, respectively. Those biodegradable electroactive elastic PUU copolymers are promising materials for repair of soft tissues such as skeletal muscle, cardiac muscle, and nerve.

Polymer chain collapse induced by many-body dipole correlations.

PubMed

Budkov, Yu A; Kalikin, N N; Kolesnikov, A L

2017-04-01

We present a simple analytical theory of a flexible polymer chain dissolved in a good solvent, carrying permanent freely oriented dipoles on the monomers. We take into account the dipole correlations within the random phase approximation (RPA), as well as a dielectric heterogeneity in the internal polymer volume relative to the bulk solution. We demonstrate that the dipole correlations of monomers can be taken into account as pairwise ones only when the polymer chain is in a coil conformation. In this case the dipole correlations manifest themselves through the Keesom interactions of the permanent dipoles. On the other hand, the dielectric heterogeneity effect (dielectric mismatch effect) leads to the effective interaction between the monomers of the polymeric coil. Both of these effects can be taken into account by renormalizing the second virial coefficient of the monomer-monomer volume interactions. We establish that in the case when the solvent dielectric permittivity exceeds the dielectric permittivity of the polymeric material, the dielectric mismatch effect competes with the dipole attractive interactions, leading to polymer coil expansion. In the opposite case, both the dielectric mismatch effect and the dipole attractive interaction lead to the polymer coil collapse. We analyse the coil-globule transition caused by the dipole correlations of monomers within the many-body theory. We demonstrate that accounting for the dipole correlations higher than the pairwise ones smooths this pure electrostatics driven coil-globule transition of the polymer chain.

Machine learning strategy for accelerated design of polymer dielectrics

DOE PAGES

Mannodi-Kanakkithodi, Arun; Pilania, Ghanshyam; Huan, Tran Doan; ...

2016-02-15

The ability to efficiently design new and advanced dielectric polymers is hampered by the lack of sufficient, reliable data on wide polymer chemical spaces, and the difficulty of generating such data given time and computational/experimental constraints. Here, we address the issue of accelerating polymer dielectrics design by extracting learning models from data generated by accurate state-of-the-art first principles computations for polymers occupying an important part of the chemical subspace. The polymers are ‘fingerprinted’ as simple, easily attainable numerical representations, which are mapped to the properties of interest using a machine learning algorithm to develop an on-demand property prediction model. Further,more » a genetic algorithm is utilised to optimise polymer constituent blocks in an evolutionary manner, thus directly leading to the design of polymers with given target properties. Furthermore, while this philosophy of learning to make instant predictions and design is demonstrated here for the example of polymer dielectrics, it is equally applicable to other classes of materials as well.« less

Significantly Elevated Dielectric and Energy Storage Traits in Boron Nitride Filled Polymer Nano-composites with Topological Structure

NASA Astrophysics Data System (ADS)

Feng, Yefeng; Zhang, Jianxiong; Hu, Jianbing; Li, Shichun; Peng, Cheng

2018-03-01

Interface induced polarization has a prominent influence on dielectric properties of 0-3 type polymer based composites containing Si-based semi-conductors. The disadvantages of composites were higher dielectric loss, lower breakdown strength and energy storage density, although higher permittivity was achieved. In this work, dielectric, conductive, breakdown and energy storage properties of four nano-composites have been researched. Based on the cooperation of fluoropolymer/alpha-SiC layer and fluoropolymer/hexagonal-BN layer, it was confirmed constructing the heterogeneous layer-by-layer composite structure rather than homogeneous mono-layer structure could significantly reduce dielectric loss, promote breakdown strength and increase energy storage density. The former worked for a larger dielectric response and the latter layer acted as a robust barrier of charge carrier transfer. The best nano-composite could possess a permittivity of 43@100 Hz ( 3.3 times of polymer), loss of 0.07@100 Hz ( 37% of polymer), discharged energy density of 2.23 J/cm3@249 kV/cm ( 10 times of polymer) and discharged energy efficiency of 54%@249 kV/cm ( 5 times of polymer). This work might enlighten a facile route to achieve the promising high energy storage composite dielectrics by constructing the layer-by-layer topological structure.

Dielectric property study of poly(4-vinylphenol)-graphene oxide nanocomposite thin film

NASA Astrophysics Data System (ADS)

Roy, Dhrubojyoti

2018-05-01

Thin film capacitor device having a sandwich structure of indium tin oxide (ITO)-coated glass/polymer or polymer nanocomposite /silver has been fabricated and their dielectric and leakage current properties has been studied. The dielectric properties of the capacitors were characterized for frequencies ranging from 1 KHz to 1 MHz. 5 wt% Poly(4-vinylphenol)(PVPh)-Graphene (GO) nanocomposite exhibited an increase in dielectric constant to 5.6 and small rise in dielectric loss to around˜0.05 at 10 KHz w.r.t polymer. The DC conductivity measurements reveal rise of leakage current in nanocomposite.

Closed-loop control of a core free rolled EAP actuator

NASA Astrophysics Data System (ADS)

Sarban, Rahimullah; Oubaek, Jakob; Jones, Richard W.

2009-03-01

Tubular dielectric electro-active polymer actuators, also referred as tubular InLastors, have many possible applications. One of the most obvious is as a positioning push-type device. This work examines the feedback closed-loop control of a core-free tubular InLastor fabricated from sheets of PolyPowerTM, an EAP material developed by Danfoss PolyPower A/S, which uses a silicone elastomer in conjunction with smart compliant electrode technology. This is part of an ongoing study to develop a precision positioning feedback control system for this device. Initially proportional and integral (PI) control is considered to provide position control of the tubular InLastor. Control of the tubular Inlastors require more than conventional control, used for linear actuators, because the InLastors display highly nonlinear static voltage-strain and voltage-force characteristics as well as dynamic hysteresis and time-dependent strain behavior. In an attempt to overcome the nonlinear static voltage-strain characteristics of the Inlastors and for improving the dynamic performance of the controlled device, a gain scheduling algorithm is then integrated into the PI controlled system.

Aromatic Polythiourea Dielectrics with High Energy Density, High Breakdown Strength, and Low Dielectric Loss

NASA Astrophysics Data System (ADS)

Wu, Shan; Burlingame, Quinn; Lin, Minren; Zhang, Qiming

2013-03-01

There is an increasing demand on dielectric materials with high electric energy density and low loss for a broad range of applications in modern electronics and electrical power systems such as hybrid electric vehicles (HEV), medical defibrillators, filters, and switched-mode power supplies. One major challenge in developing dielectric polymers is how to achieve high energy density Ue while maintaining low dielectric loss, even at very high-applied electric fields. Here we show that amorphous polar-polymers with very low impurity concentration can be promising for realizing such a dielectric polymer. Polar-polymer with high dipole moment and weak dipole coupling can provide relatively high dielectric constant for high Ue, eliminate polarization and conduction losses due to weak dipolar coupling and strong polar-scattering to charge carriers. Indeed, an aromatic polythiourea thin film can maintain low loss to high fields (>1 GV/m) with a high Ue (~ 24 J/cm3) , which is very attractive for energy storage capacitors.

Proximity and touch sensing using deformable ionic conductors (Conference Presentation)

NASA Astrophysics Data System (ADS)

Madden, John D. W.; Dobashi, Yuta; Sarwar, Mirza S.; Preston, Eden C.; Wyss, Justin K. M.; Woehling, Vincent; Nguyen, Tran-Minh-Giao; Plesse, Cedric; Vidal, Frédéric; Naficy, Sina; Spinks, Geoffrey M.

2017-04-01

There is increasing interest in creating bendable and stretchable electronic interfaces that can be worn or applied to virtually any surface. The electroactive polymer community is well placed to add value by incorporating sensors and actuators. Recent work has demonstrated transparent dielectric elastomer actuation as well as pressure, stretch or touch sensing. Here we present two alternative forms of sensing. The first uses ionically conductive and stretchable gels as electrodes in capacitive sensors that detect finger proximity. In this case the finger acts as a third electrode, reducing capacitance between the two gel electrodes as it approaches, which can be detected even during bending and stretching. Very light finger touch is readily detected even during deformation of the substrate. Lateral resolution is achieved by creating a sensor array. In the second approach, electrodes placed beneath a salt containing gel are able to detect ion currents generated by the deformation of the gel. In this approach, applied pressure results in ion currents that create a potential difference around the point of contact, leading to a voltage and current in the electrodes without any need for input electrical energy. The mechanism may be related to effects seen in ionomeric polymer metal composites (IPMCs), but with the response in plane rather than through the thickness of the film. Ultimately, these ionically conductive materials that can also be transparent and actuate, have the potential to be used in wearable devices.

Fluoro-polymer functionalized graphene for flexible ferroelectric polymer-based high-k nanocomposites with suppressed dielectric loss and low percolation threshold.

PubMed

Yang, Ke; Huang, Xingyi; Fang, Lijun; He, Jinliang; Jiang, Pingkai

2014-12-21

Flexible nanodielectric materials with high dielectric constant and low dielectric loss have huge potential applications in the modern electronic and electric industry. Graphene sheets (GS) and reduced-graphene oxide (RGO) are promising fillers for preparing flexible polymer-based nanodielectric materials because of their unique two-dimensional structure and excellent electrical and mechanical properties. However, the easy aggregation of GS/RGO significantly limits the potential of graphene in enhancing the dielectric constant of polymer composites. In addition, the poor filler/matrix nanoscale interfacial adhesion also causes difficulties in suppressing the dielectric loss of the composites. In this work, using a facile and environmentally friendly approach, polydopamine coated RGO (PDA-RGO) and fluoro-polymer functionalized RGO (PF-PDA-RGO) were prepared. Compared with the RGO prepared by the conventional methods [i.e. hydrazine reduced-graphene oxide (H-RGO)] and PDA-RGO, the resulting PF-PDA-RGO nanosheets exhibit excellent dispersion in the ferroelectric polymer matrix [i.e. poly(vinylidene fluoride-co-hexafluoro propylene), P(VDF-HFP)] and strong interfacial adhesion with the matrix, leading to a low percolation threshold (fc = 1.06 vol%) and excellent flexibility for the corresponding nanocomposites. Among the three nanocomposites, the P(VDF-HFP)/PF-PDA-RGO nanocomposites exhibited the optimum performance (i.e. simultaneously having high dielectric constant and low dielectric loss). For instance, at 1000 Hz, the P(VDF-HFP) nanocomposite sample with 1.0 vol% PF-PDA-RGO has a dielectric constant of 107.9 and a dielectric loss of 0.070, showing good potential for dielectric applications. Our strategy provides a new pathway to prepare high performance flexible nanodielectric materials.

Spacecraft dielectric material properties and spacecraft charging

NASA Technical Reports Server (NTRS)

Frederickson, A. R.; Wall, J. A.; Cotts, D. B.; Bouquet, F. L.

1986-01-01

The physics of spacecraft charging is reviewed, and criteria for selecting and testing semiinsulating polymers (SIPs) to avoid charging are discussed and illustrated. Chapters are devoted to the required properties of dielectric materials, the charging process, discharge-pulse phenomena, design for minimum pulse size, design to prevent pulses, conduction in polymers, evaluation of SIPs that might prevent spacecraft charging, and the general response of dielectrics to space radiation. SIPs characterized include polyimides, fluorocarbons, thermoplastic polyesters, poly(alkanes), vinyl polymers and acrylates, polymers containing phthalocyanine, polyacene quinones, coordination polymers containing metal ions, conjugated-backbone polymers, and 'metallic' conducting polymers. Tables summarizing the results of SIP radiation tests (such as those performed for the NASA Galileo Project) are included.

Performance of dielectric nanocomposites: matrix-free, hairy nanoparticle assemblies and amorphous polymer-nanoparticle blends.

PubMed

Grabowski, Christopher A; Koerner, Hilmar; Meth, Jeffrey S; Dang, Alei; Hui, Chin Ming; Matyjaszewski, Krzysztof; Bockstaller, Michael R; Durstock, Michael F; Vaia, Richard A

2014-12-10

Demands to increase the stored energy density of electrostatic capacitors have spurred the development of materials with enhanced dielectric breakdown, improved permittivity, and reduced dielectric loss. Polymer nanocomposites (PNCs), consisting of a blend of amorphous polymer and dielectric nanofillers, have been studied intensely to satisfy these goals; however, nanoparticle aggregates, field localization due to dielectric mismatch between particle and matrix, and the poorly understood role of interface compatibilization have challenged progress. To expand the understanding of the inter-relation between these factors and, thus, enable rational optimization of low and high contrast PNC dielectrics, we compare the dielectric performance of matrix-free hairy nanoparticle assemblies (aHNPs) to blended PNCs in the regime of low dielectric contrast to establish how morphology and interface impact energy storage and breakdown across different polymer matrices (polystyrene, PS, and poly(methyl methacrylate), PMMA) and nanoparticle loadings (0-50% (v/v) silica). The findings indicate that the route (aHNP versus blending) to well-dispersed morphology has, at most, a minor impact on breakdown strength trends with nanoparticle volume fraction; the only exception being at intermediate loadings of silica in PMMA (15% (v/v)). Conversely, aHNPs show substantial improvements in reducing dielectric loss and maintaining charge/discharge efficiency. For example, low-frequency dielectric loss (1 Hz-1 kHz) of PS and PMMA aHNP films was essentially unchanged up to a silica content of 50% (v/v), whereas traditional blends showed a monotonically increasing loss with silica loading. Similar benefits are seen via high-field polarization loop measurements where energy storage for ∼15% (v/v) silica loaded PMMA and PS aHNPs were 50% and 200% greater than respective comparable PNC blends. Overall, these findings on low dielectric contrast PNCs clearly point to the performance benefits of functionalizing the nanoparticle surface with high-molecular-weight polymers for polymer nanostructured dielectrics.

Human-like robots as platforms for electroactive polymers (EAP)

NASA Astrophysics Data System (ADS)

Bar-Cohen, Yoseph

2008-03-01

Human-like robots, which have been a science fiction for many years, are increasingly becoming an engineering reality thanks to many technology advances in recent years. Humans have always sought to imitate the human appearance, functions and intelligence and as the capability progresses they may become our household appliance or even companion. Biomimetic technologies are increasingly becoming common tools to support the development of such robots. As artificial muscles, electroactive polymers (EAP) are offering important actuation capability for making such machines lifelike. The current limitations of EAP are hampering the possibilities that can be adapted in such robots but progress is continually being made. As opposed to other human made machines and devices, this technology raises various questions and concerns that need to be addressed. These include the need to prevent accidents, deliberate harm, or their use in crimes. In this paper the state-of-the-art and the challenges will be reviewed.

Electroactive polymer (EAP) actuators for future humanlike robots

NASA Astrophysics Data System (ADS)

Bar-Cohen, Yoseph

2009-03-01

Human-like robots are increasingly becoming an engineering reality thanks to recent technology advances. These robots, which are inspired greatly by science fiction, were originated from the desire to reproduce the human appearance, functions and intelligence and they may become our household appliance or even companion. The development of such robots is greatly supported by emerging biologically inspired technologies. Potentially, electroactive polymer (EAP) materials are offering actuation capabilities that allow emulating the action of our natural muscles for making such machines perform lifelike. There are many technical issues related to making such robots including the need for EAP materials that can operate as effective actuators. Beside the technology challenges these robots also raise concerns that need to be addressed prior to forming super capable robots. These include the need to prevent accidents, deliberate harm, or their use in crimes. In this paper, the potential EAP actuators and the challenges that these robots may pose will be reviewed.

Electroactive Polymer (EAP) Actuators for Future Humanlike Robots

NASA Technical Reports Server (NTRS)

Bar-Cohen, Yoseph

2009-01-01

Human-like robots are increasingly becoming an engineering reality thanks to recent technology advances. These robots, which are inspired greatly by science fiction, were originated from the desire to reproduce the human appearance, functions and intelligence and they may become our household appliance or even companion. The development of such robots is greatly supported by emerging biologically inspired technologies. Potentially, electroactive polymer (EAP) materials are offering actuation capabilities that allow emulating the action of our natural muscles for making such machines perform lifelike. There are many technical issues related to making such robots including the need for EAP materials that can operate as effective actuators. Beside the technology challenges these robots also raise concerns that need to be addressed prior to forming super capable robots. These include the need to prevent accidents, deliberate harm, or their use in crimes. In this paper, the potential EAP actuators and the challenges that these robots may pose will be reviewed.

Low and High Molecular Mass Dithienopyrrole-Naphthalene Bisimide Donor-Acceptor Compounds: Synthesis, Electrochemical and Spectroelectrochemical Behaviour.

PubMed

Rybakiewicz, Renata; Glowacki, Eric D; Skorka, Lukasz; Pluczyk, Sandra; Zassowski, Pawel; Apaydin, Dogukan Hazar; Lapkowski, Mieczyslaw; Zagorska, Malgorzata; Pron, Adam

2017-02-24

Two low molecular weight electroactive donor-acceptor-donor (DAD)-type molecules are reported, namely naphthalene bisimide (NBI) symmetrically core-functionalized with dithienopyrrole (NBI-(DTP) 2 ) and an asymmetric core-functionalized naphthalene bisimide with dithienopyrrole (DTP) substituent on one side and 2-ethylhexylamine on the other side (NBI-DTP-NHEtHex). Both compounds are characterized by low optical bandgaps (1.52 and 1.65 eV, respectively). NBI-(DTP) 2 undergoes oxidative electropolymerization giving the electroactive polymer of ambipolar character. Its two-step reversible reduction and oxidation is corroborated by complementary EPR and UV/Vis-NIR spectroelectrochemical investigations. The polymer turned out to be electrochemically active not only in aprotic solvents but also in aqueous electrolytes, showing a distinct photocathodic current attributed to proton reduction. Additionally, poly(NBI-(DTP) 2 ) was successfully tested as a photodiode material. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electro-Active Polymer Based Soft Tactile Interface for Wearable Devices.

PubMed

Mun, Seongcheol; Yun, Sungryul; Nam, Saekwang; Park, Seung Koo; Park, Suntak; Park, Bong Je; Lim, Jeong Mook; Kyung, Ki-Uk

2018-01-01

This paper reports soft actuator based tactile stimulation interfaces applicable to wearable devices. The soft actuator is prepared by multi-layered accumulation of thin electro-active polymer (EAP) films. The multi-layered actuator is designed to produce electrically-induced convex protrusive deformation, which can be dynamically programmable for wide range of tactile stimuli. The maximum vertical protrusion is and the output force is up to 255 mN. The soft actuators are embedded into the fingertip part of a glove and front part of a forearm band, respectively. We have conducted two kinds of experiments with 15 subjects. Perceived magnitudes of actuator's protrusion and vibrotactile intensity were measured with frequency of 1 Hz and 191 Hz, respectively. Analysis of the user tests shows participants perceive variation of protrusion height at the finger pad and modulation of vibration intensity through the proposed soft actuator based tactile interface.

Controlling Crystal Microstructure to Minimize Loss in Polymer Dielectrics

NASA Astrophysics Data System (ADS)

Miranda, Daniel; Iacob, Ciprian; Zhang, Shihai; Runt, James

Polymer dielectric films are of great importance for high performance capacitors. For these films it is critical to reduce dielectric loss, as it diminishes efficiency and contributes to waste heat generation during device operation. Here, a model semi-crystalline polymer, poly(ethylene naphthalate) (PEN), was used to examine how morphological factors inhibit chain relaxations responsible for loss. This was achieved by manipulating the extent of crystallization and the crystalline microstructure through a combination of annealing and uniaxial drawing, and investigating their effects on dielectric performance. Varying crystallization conditions influenced the dynamic Tg and extent of rigid amorphous fraction formation, but had a limited effect on loss magnitude. Film orientation however greatly reduced loss, through strain-induced crystallization and development of oriented amorphous mesophasic regions. Post-drawing annealing conditions were capable of further refining the crystal microstructure and, in turn, the dielectric properties. These findings demonstrate that semi-crystalline polymer morphology has a very strong influence on amorphous chain relaxations, and understanding how processing conditions affect morphology is critical to the rational design of polymer dielectrics. Office of Naval Research.

Anisotropic D-EAP Electrodes and their Application in Spring Roll Actuators

NASA Astrophysics Data System (ADS)

Fang, Xiaomeng

Electroactive polymers (EAPs) exhibit shape change when subjected to an electric field. They are lightweight, soft, and inexpensive, while they are easy to process, shape, and tune to offer a broad range of mechanical and electrical properties. Dielectric electroactive polymers (DEAP) constitute a class of EAPs with great potential. D-EAPs consist of physically or chemically cross-linked macromolecular networks and are mechanically isotopic. Therefore, in most actuator applications that require directional electromechanical response, it is necessary to use other complex means to direct the stress/strain in the preferred direction. In this work, a simple carbon nanotube (CNT) based electrode for D-EAP actuators is demonstrated that vastly improves directional strain response originating from the mechanical anisotropy of the electrode material. Using this novel approach, the mechanical anisotropy, defined as the ratio of initial modulus in fiber direction and that in cross-fiber direction, of the CNT electroded VHB actuators, ranges from 7.9 to 11.2. Hence, the CNT-VHB flat film actuators show high directed linear actuation strain in cross-fiber direction of greater than 25% meanwhile almost no strain in fiber direction at a relatively low electric field (120 V mum-1). The morphology of the CNT sheets has critical influence on their mechanical properties and resultant actuator performance. The results demonstrate the efficacy of microcombing and selective laser etching processes to improve the CNT fiber alignment to produce pure unidirectional strain of 33% at a relatively moderate electric field. Unidirectional D-EAP composite laminates using polyurethane and polyamide monofilaments are also employed in spring roll actuators to investigate their directional mechanical and electromechanical properties. While CNT electroded D-EAP spring roll actuators were found to have about the same performance as actuators with carbon grease electrodes (6.5% strain in CNT electroded spring roll actuators and 8.2% for carbon grease electroded actuators at 5kV), spring roll actuator made of fiber reinforced VHB composites with carbon grease electrodes showed marginal improvement in actuation strain (9.9%-11% strain in longitudinal direction at 5kV).

Improving dielectric properties of BaTiO3/poly(vinylidene fluoride) composites by employing core-shell structured BaTiO3@Poly(methylmethacrylate) and BaTiO3@Poly(trifluoroethyl methacrylate) nanoparticles

NASA Astrophysics Data System (ADS)

Zhang, Xianhong; Zhao, Sidi; Wang, Fang; Ma, Yuhong; Wang, Li; Chen, Dong; Zhao, Changwen; Yang, Wantai

2017-05-01

Polymer based dielectric composites were fabricated through incorporation of core-shell structured BaTiO3 (BT) nanoparticles into PVDF matrix by means of solution blending. Core-shell structured BT nanoparticles with different shell composition and shell thickness were prepared by grafting methacrylate monomer (MMA or TFEMA) onto the surface of BT nanoparticles via surface initiated atom transfer radical polymerization (SI-ATRP). The content of the grafted polymer and the micro-morphology of the core-shell structured BT nanoparticles were investigated by thermo gravimetric analyses (TGA) and transmission electron microscopy (TEM), respectively. The dielectric properties were measured by broadband dielectric spectroscopy. The results showed that high dielectric constant and low dielectric loss are successfully realized in the polymer based composites. Moreover, the type of the grafted polymer and its content had different effect on the dielectric constant. In detail, the attenuation of dielectric constant was 16.6% for BT@PMMA1/PVDF and 10.7% for BT@PMMA2/PVDF composite in the range of 10 Hz to 100 kHz, in which the grafted content of PMMA was 5.5% and 8.0%, respectively. However, the attenuation of dielectric constant was 5.5% for BT@PTFEMA1/PVDF and 4.0% for BT@PTFEMA2/PVDF composite, in which the grafted content of PTFEMA was 1.5% and 2.0%, respectively. These attractive features of BT@PTFEMA/PVDF composites suggested that dielectric ceramic fillers modified with fluorinated polymer can be used to prepare high performance composites, especially those with low dielectric loss and high dielectric constant.

Molecular architecture of electroactive and biodegradable copolymers composed of polylactide and carboxyl-capped aniline trimer.

PubMed

Guo, Baolin; Finne-Wistrand, Anna; Albertsson, Ann-Christine

2010-04-12

Two-, four-, and six-armed branched copolymers with electroactive and biodegradable properties were synthesized by coupling reactions between poly(l-lactides) (PLLAs) with different architecture and carboxyl-capped aniline trimer (CCAT). The aniline oligomer CCAT was prepared from amino-capped aniline trimer and succinic anhydride. FT-IR, NMR, and SEC analyses confirmed the structure of the branched copolymers. UV-vis spectra and cyclic voltammetry of CCAT and copolymer solution showed good electroactive properties, similar to those of polyaniline. The water contact angle of the PLLAs was the highest, followed by the undoped copolymer and the doped copolymers. The values of doped four-armed copolymers were 54-63 degrees . Thermal properties of the polymers were studied by DSC and TGA. The copolymers had better thermal stability than the pure PLLAs, and the T(g) between 48-58 degrees C and T(m) between 146-177 degrees C of the copolymers were lower than those of the pure PLLA counterparts. This kind of electroactive and biodegradable copolymer has a great potential for applications in cardiovascular or neuronal tissue engineering.

Method of forming nanodielectrics

DOEpatents

Tuncer, Enis [Knoxville, TN; Polyzos, Georgios [Oak Ridge, TN

2014-01-07

A method of making a nanoparticle filled dielectric material. The method includes mixing nanoparticle precursors with a polymer material and reacting the nanoparticle mixed with the polymer material to form nanoparticles dispersed within the polymer material to form a dielectric composite.

Dielectric breakdown in silica-amorphous polymer nanocomposite films: the role of the polymer matrix.

PubMed

Grabowski, Christopher A; Fillery, Scott P; Westing, Nicholas M; Chi, Changzai; Meth, Jeffrey S; Durstock, Michael F; Vaia, Richard A

2013-06-26

The ultimate energy storage performance of an electrostatic capacitor is determined by the dielectric characteristics of the material separating its conductive electrodes. Polymers are commonly employed due to their processability and high breakdown strength; however, demands for higher energy storage have encouraged investigations of ceramic-polymer composites. Maintaining dielectric strength, and thus minimizing flaw size and heterogeneities, has focused development toward nanocomposite (NC) films; but results lack consistency, potentially due to variations in polymer purity, nanoparticle surface treatments, nanoparticle size, and film morphology. To experimentally establish the dominant factors in broad structure-performance relationships, we compare the dielectric properties for four high-purity amorphous polymer films (polymethyl methacrylate, polystyrene, polyimide, and poly-4-vinylpyridine) incorporating uniformly dispersed silica colloids (up to 45% v/v). Factors known to contribute to premature breakdown-field exclusion and agglomeration-have been mitigated in this experiment to focus on what impact the polymer and polymer-nanoparticle interactions have on breakdown. Our findings indicate that adding colloidal silica to higher breakdown strength amorphous polymers (polymethyl methacrylate and polyimide) causes a reduction in dielectric strength as compared to the neat polymer. Alternatively, low breakdown strength amorphous polymers (poly-4-vinylpyridine and especially polystyrene) with comparable silica dispersion show similar or even improved breakdown strength for 7.5-15% v/v silica. At ∼15% v/v or greater silica content, all the polymer NC films exhibit breakdown at similar electric fields, implying that at these loadings failure becomes independent of polymer matrix and is dominated by silica.

Multicomponent Solvated Triblock Copolymer Network Systems: Fundamental Insights and Emerging Applications

NASA Astrophysics Data System (ADS)

Krishnan, Arjun Sitaraman

Block copolymers have received significant research attention in recent times due to their ability to spontaneously self-assemble into a variety of nanostructures. Thermoplastic elastomers composed of styrenic triblock copolymers are of great importance in applications such as adhesives and vibration dampening due to their shape memory, resilience and facile processing. The swelling of these polymers by adding midblock selective solvents or oligomers provides an easy route by which to modify the morphology and mechanical behavior of these systems. We first consider a ternary blend of a poly[styrene- b-(ethylene-co-butylene)-b-styrene] triblock copolymer (SEBS) and mixtures of two midblock selective co-solvents, with significantly different physical states. We use dynamic rheology to study the viscoelastic response of a wide variety of systems under oscillatory shear. Frequency spectra acquired at ambient temperature display viscoelastic behavior that shifts in the frequency domain depending on the co-solvent composition. For each copolymer concentration, all the frequency data can be shifted by time-composition superpositioning (tCS) to yield a single master-curve. tCS fails at low frequencies due to presence of endblock pullout, which is a fundamentally different relaxation process from segmental relaxation of the midblock. As an emerging technology, we examine SEBS-oil gels as dielectric elastomers. Dielectric elastomers constitute one class of electroactive polymers (EAPs), polymeric materials that respond to an electric stimulus by changing their macroscopic dimensions, thereby converting electrical energy into mechanical work. We use standard configuration of EAP devices involving stretching, or "prestraining," the elastomer film biaxially. The effect of experimental parameters such as film thickness and amount of prestrain on the (electro)mechanical properties of the material become apparent by recasting as-obtained electroactuation data into compressive electromechanical stress-strain curves. The ultimate dielectric properties of the specimen are strongly correlated with specimen composition and experimental conditions. We shed light on the effect of biaxial prestrain on copolymer morphology. We use small-angle X-ray scattering (SAXS) to probe the nanostructure of SEBS-oil gels by systematically changing the concentration of polymer and the biaxial prestrain. Azimuthally integrated intensity profiles are used to ascertain the extent of deformation of polystyrene microdomains. The structure factor data correlates with prestrain, and is fitted using the Percus-Yevick approximation for interacting spheres. While a hard sphere interaction model is sufficient for unstrained gels, the additional attractive potentials observed in stretched samples are indicative of soft coronal interactions due to interpenetration brought about by strain.

Characterization, fabrication, and analysis of soft dielectric elastomer actuators capable of complex 3D deformation

NASA Astrophysics Data System (ADS)

Lai, William

Inspired by nature, the development of soft actuators has drawn large attention to provide higher flexibility and allow adaptation to more complex environment. This thesis is focused on utilizing electroactive polymers as active materials to develop soft planar dielectric elastomer actuators capable of complex 3D deformation. The potential applications of such soft actuators are in flexible robotic arms and grippers, morphing structures and flapping wings for micro aerial vehicles. The embraces design for a freestanding actuator utilizes the constrained deformation imposed by surface stiffeners on an electroactive membrane to avert the requirement of membrane pre-stretch and the supporting frames. The proposed design increases the overall actuator flexibility and degrees-of-freedom. Actuator design, fabrication, and performance are presented for different arrangement of stiffeners. Digital images correlation technique were utilized to evaluate the in-plane finite strain components, in order to elucidate the role of the stiffeners in controlling the three dimensional deformation. It was found that a key controlling factor was the localized deformation near the stiffeners, while the rest of the membrane would follow through. A detailed finite element modeling framework was developed with a user-material subroutine, built into the ABAQUS commercial finite element package. An experimentally calibrated Neo-Hookean based material model that coupled the applied electrical field to the actuator mechanical deformation was employed. The numerical model was used to optimize different geometrical features, electrode layup and stacking sequence of actuators. It was found that by splitting the stiffeners into finer segments, the force-stroke characteristics of actuator were able to be adjusted with stiffener configuration, while keeping the overall bending stiffness. The efficacy of actuators could also be greatly improved by increasing the stiffener periodicity. The developed framework would aid in designing and optimizing the dielectric elastomer actuator configurations for 3D prescribed deformation configuration. Finally, inspired by the membrane textures of bat wings, a study of utilizing fiber reinforcement on dielectric elastomer actuators were conducted for the mechanical and the coupled electromechanical characteristics. Woven fibers were employed on the surface of actuator membrane with different pre-deformed configurations. Experimentally, actuator stiffness changes were measured for up to four orders of magnitude. The orientation of embedded fibers controlled the level and the triggered phase of stiffness changes. A trade-off between the actuator stiffness and stroke could be controlled during the fabrication stage by the fiber orientation and the prestretch level of the base elastomer membrane. A simplified model using small-strain composite laminate theory was developed and accurately predicted the composite actuator stiffness. Additionally, compliant edge stiffeners were found had to present a marked overall effect on actuator electromechanical response. The developed simplified analytical solutions using Timoshenko-bimaterial laminate solution and composite laminate theory, as well as the developed finite element framework can be utilized in addressing more complex 3D deformation patterns and their electromechanical response.

Controlled thermal expansion printed wiring boards based on liquid crystal polymer dielectrics

NASA Technical Reports Server (NTRS)

Knoll, Thomas E.; Blizard, Kent; Jayaraj, K.; Rubin, Leslie S.

1994-01-01

Dielectric materials based on innovative Liquid Crystal Polymers (LCP's) have been used to fabricate surface mount printed wiring boards (PWB's) with a coefficient of thermal expansion matched to leadless ceramic chip carriers. Proprietary and patented polymer processing technology has resulted in self reinforcing material with balanced in-plane mechanical properties. In addition, LCP's possess excellent electrical properties, including a low dielectric constant (less than 2.9) and very low moisture absorption (less than 0.02%). LCP-based multilayer boards processed with conventional drilling and plating processes show improved performance over other materials because they eliminate the surface flatness problems of glass or aramid reinforcements. Laser drilling of blind vias in the LCP dielectric provides a very high density for use in direct chip attach and area array packages. The material is ideally suited for MCM-L and PCMCIA applications fabricated with very thin dielectric layers of the liquid crystal polymer.

Pair interactions in polyelectrolyte-nanoparticle systems: Influence of dielectric inhomogeneities and the partial dissociation of polymers and nanoparticles.

PubMed

Pryamitsyn, Victor; Ganesan, Venkat

2015-10-28

We study the effective pair interactions between two charged spherical particles in polyelectrolyte solutions using polymer self-consistent field theory. In a recent study [V. Pryamitsyn and V. Ganesan, Macromolecules 47, 6095 (2015)], we considered a model in which the particles possess fixed charge density, the polymers contain a prespecified amount of dissociated charges and, the dielectric constant of the solution was assumed to be homogeneous in space and independent of the polymer concentration. In this article, we present results extending our earlier model to study situations in which either or both the particle and the polymers possess partially dissociable groups. Additionally, we also consider the case when the dielectric constant of the solution depends on the local concentration of the polymers and when the particle's dielectric constant is lower than that of the solvent. For each case, we quantify the polymer-mediated interactions between the particles as a function of the polymer concentrations and the degree of dissociation of the polymer and particles. Consistent with the results of our previous study, we observe that the polymer-mediated interparticle interactions consist of a short-range attraction and a long-range repulsion. The partial dissociablity of the polymer and particles was seen to have a strong influence on the strength of the repulsive portion of the interactions. Rendering the dielectric permittivity to be inhomogeneous has an even stronger effect on the repulsive interactions and results in changes to the qualitative nature of interactions in some parametric ranges.

Flexible high-temperature dielectric materials from polymer nanocomposites.

PubMed

Li, Qi; Chen, Lei; Gadinski, Matthew R; Zhang, Shihai; Zhang, Guangzu; Li, Haoyu; Iagodkine, Elissei; Haque, Aman; Chen, Long-Qing; Jackson, Tom; Wang, Qing

2015-07-30

Dielectric materials, which store energy electrostatically, are ubiquitous in advanced electronics and electric power systems. Compared to their ceramic counterparts, polymer dielectrics have higher breakdown strengths and greater reliability, are scalable, lightweight and can be shaped into intricate configurations, and are therefore an ideal choice for many power electronics, power conditioning, and pulsed power applications. However, polymer dielectrics are limited to relatively low working temperatures, and thus fail to meet the rising demand for electricity under the extreme conditions present in applications such as hybrid and electric vehicles, aerospace power electronics, and underground oil and gas exploration. Here we describe crosslinked polymer nanocomposites that contain boron nitride nanosheets, the dielectric properties of which are stable over a broad temperature and frequency range. The nanocomposites have outstanding high-voltage capacitive energy storage capabilities at record temperatures (a Weibull breakdown strength of 403 megavolts per metre and a discharged energy density of 1.8 joules per cubic centimetre at 250 degrees Celsius). Their electrical conduction is several orders of magnitude lower than that of existing polymers and their high operating temperatures are attributed to greatly improved thermal conductivity, owing to the presence of the boron nitride nanosheets, which improve heat dissipation compared to pristine polymers (which are inherently susceptible to thermal runaway). Moreover, the polymer nanocomposites are lightweight, photopatternable and mechanically flexible, and have been demonstrated to preserve excellent dielectric and capacitive performance after intensive bending cycles. These findings enable broader applications of organic materials in high-temperature electronics and energy storage devices.

Flexible high-temperature dielectric materials from polymer nanocomposites

NASA Astrophysics Data System (ADS)

Li, Qi; Chen, Lei; Gadinski, Matthew R.; Zhang, Shihai; Zhang, Guangzu; Li, Haoyu; Haque, Aman; Chen, Long-Qing; Jackson, Tom; Wang, Qing

2015-07-01

Dielectric materials, which store energy electrostatically, are ubiquitous in advanced electronics and electric power systems. Compared to their ceramic counterparts, polymer dielectrics have higher breakdown strengths and greater reliability, are scalable, lightweight and can be shaped into intricate configurations, and are therefore an ideal choice for many power electronics, power conditioning, and pulsed power applications. However, polymer dielectrics are limited to relatively low working temperatures, and thus fail to meet the rising demand for electricity under the extreme conditions present in applications such as hybrid and electric vehicles, aerospace power electronics, and underground oil and gas exploration. Here we describe crosslinked polymer nanocomposites that contain boron nitride nanosheets, the dielectric properties of which are stable over a broad temperature and frequency range. The nanocomposites have outstanding high-voltage capacitive energy storage capabilities at record temperatures (a Weibull breakdown strength of 403 megavolts per metre and a discharged energy density of 1.8 joules per cubic centimetre at 250 degrees Celsius). Their electrical conduction is several orders of magnitude lower than that of existing polymers and their high operating temperatures are attributed to greatly improved thermal conductivity, owing to the presence of the boron nitride nanosheets, which improve heat dissipation compared to pristine polymers (which are inherently susceptible to thermal runaway). Moreover, the polymer nanocomposites are lightweight, photopatternable and mechanically flexible, and have been demonstrated to preserve excellent dielectric and capacitive performance after intensive bending cycles. These findings enable broader applications of organic materials in high-temperature electronics and energy storage devices.

EDITORIAL: Artificial Muscles: Selected papers from the 5th World Congress on Biomimetics, Artificial Muscles and Nano-Bio (Osaka, Japan, 25-27 November 2009) Artificial Muscles: Selected papers from the 5th World Congress on Biomimetics, Artificial Muscles and Nano-Bio (Osaka, Japan, 25-27 November 2009)

NASA Astrophysics Data System (ADS)

Shahinpoor, Mohsen

2011-12-01

The 5th World Congress on Biomimetics, Artificial Muscles and Nano-Bio and the 4th International Conference on Artificial Muscles were held in Osaka, Japan, 23-27 November 2009. This special section of Smart Materials and Structures is devoted to a selected number of research papers presented at this international conference and congress. Of the 76 or so papers presented at the conference, only 10 papers were finally selected, reviewed and accepted for this special section, following the regular reviewing procedures of the journal. This special section is focused on polymeric artificial muscles, electroactive polymers, multifunctional nanocomposites and their applications. In particular, an electromechanical model for self-sensing ionic polymer-metal composite actuating devices with patterned surface electrodes is presented which discusses the concept of creating self-sensing ionic polymer-metal composite (IPMC) actuating devices with patterned surface electrodes where actuator and sensor elements are separated by a grounded shielding electrode. Eventually, an electromechanical model of the device is also proposed and validated. Following that, there is broad coverage of polytetrahydrofurane-polyethylene oxide-PEDOT conducting interpenetrating polymer networks (IPNs) for high speed actuators. The conducting polymer (poly(3,4-ethylenedioxythiophene)) is incorporated within the IPNs, which are synthesized from polyethylene oxide (PEO)/polytetrahydrofurane (PTHF) networks. PEO/PTHF IPNs are prepared using poly(ethylene glycol) methacrylate and dimethacrylate and hydroxythelechelic PTHF as starting materials. The conducting IPN actuators are prepared by oxidative polymerization of 3,4-ethylenedioxithiophene (EDOT) using FeCl3 as an oxidizing agent within the PEO/PTHF IPN host matrix. Subsequently, giant and reversible magnetorheology of carrageenan/iron oxide magnetic gels are discussed and the effect of magnetic fields on the viscoelastic properties, magnetorheological effect of carrageenan gel containing iron oxide particles are investigated using dynamic viscoelastic measurements under magnetic fields. Furthermore, the relationship between the magnetorheology and the elasticity of magnetic gel is discussed. This special section then covers the characteristics of ionic polymer-metal composite with chemically-doped TiO2 particles to improve the bending performance of ionic polymer-metal composite (IPMC) actuators. This study is mainly focused on the characterization of the physical, electrochemical, and electromechanical properties of TiO2-doped ionic polymer membranes, and IPMCs prepared by the sol-gel method, which results in a uniform distribution of the particles inside the polymer membrane. It was determined that the lifetime of IPMC is strongly dependent on the level of water uptake. This paper is then followed by a presentation on training and shape retention in conducting polymer artificial muscles. Electrochemomechanical deformation (ECMD) of the conducting polymer, polyaniline film, is studied to investigate the behavior of actuation under tensile loads. The ECMD is induced by strains due to insertion of ionic species (cyclic strain) and a creep due to applied loads during the redox cycle. The cyclic strain is enhanced by the experience of high tensile loads, indicating a training effect. The training effect is explained by the enhanced electrochemical activity of the film. The special section then presents a paper on the current status and future prospects of power generators using dielectric elastomers. Electroactive polymer artificial muscle (EPAM), known as 'dielectric elastomer', appears to offer unique capabilities as an actuator and electrical power generator. However, the power output levels of such generators are small and the efficiencies are rather high. For example, electrical energy conversion efficiency of over 70% has been achieved. The ability of EPAM to produce hydrogen fuel for energy storage was also demonstrated. Because the energy conversion principle of EPAM is capacitive in nature, the performance is largely size-independent. Formation of motile assembly of microtubules driven by kinesins is presented next. Microtubule (MT) and kinesin are rail and motor proteins that are involved in various moving events of eukaryotic cells in natural systems. In vitro, the sliding motion of microtubules (rail) can be reproduced on a kinesin (motor protein)-coated surface coupled with adenosine triphosphate (ATP) hydrolysis, which is called a 'motility assay'. Based on this technique, a method is reported for forming MT assemblies by an active self-assembly (AcSA) process, in which MTs are crosslinked during a sliding motion on a kinesin-coated surface. Streptavidin (ST) is employed as glue to crosslink biotin-labeled MTs. This discussion is then followed by a paper on the performances of fast-moving low-voltage electromechanical actuators based on single-walled carbon nanotubes and ionic liquids. Here the mechanical and electrical properties of the polymer-free single-walled carbon nanotube (SWNT) sheets containing different contents of ionic liquids (ILs) are reported. The polymer-free SWNT sheets are prepared with the knowledge that millimeter-long 'super growth' carbon nanotubes (SG-SWNTs), produced by a water-assisted modified CVD method, associate together tightly with ILs. The molecular mechanism of electroactive polymer actuators is then discussed in the next paper. Movement of ionic electroactive polymer actuators utilizes their anisotropic volume change, which is induced by the applied voltage. The mechanism of the volume change is, however, not well understood, especially at the molecular level. The current understanding of the mechanism of the volume change at the molecular level is reviewed, focusing on the actuators made with carbon materials. Then, the pressure generated in the actuators in response to the applied voltage based on the results of the Monte Carlo simulation is discussed. It is shown that the mechanism of the actuators can be analyzed at the molecular level in terms of the balance between the electrostatic and volume exclusion interactions that act among the electrode materials and the electrolyte ions. The special section then presents a master curve for analyzing the electrochemical aging and memory effects of poly(3,4-ethylenedioxythiophene). The memory effect of conducting polymers in an electrochemical environment is investigated. This memory effect is related to the electromechanical responses of the conducting polymer. Poly(3,4-ethylenedioxythiophene) is chosen because of its interesting properties—mainly its chemical and electrochemical stabilities. By means of cyclic voltammetry, the influence of the waiting time tw at a holding potential Ew in relation to the conformational relaxation process occurring in the conducting polymer is analyzed. The effect of electrochemical aging on the electrical properties is also explained from the viewpoint of the rearrangement of polymer chains. This completes a brief report on the content of the special section on artificial muscles. I would like to thank the contributing authors of this collection of papers on artificial muscles for their outstanding and unique contributions. I am also indebted to all of the reviewers, editors and editorial staff who handled the reviews of all the papers for their time and effort. I would like to express my sincere thanks and appreciation to Professor E Garcia, Editor-in-Chief, for his encouragement and support, and for providing the opportunity to publish this special section of Smart Materials and Structures. I am also grateful to the IOP Publishing team for their support. In particular, I am greatly indebted to publisher Natasha Leeper, for her help and excellent management in the preparation of this special section on artificial muscles.

Dielectric Characterization of Mylar and The Effects of Doping Processes.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Belcher, Cami Beth

2016-11-01

Mylar® polymer is a bi-axially oriented polyethylene terephthalate (PET) polymer film used widely as a dielectric, specifically in capacitors. The dielectric characteristics of Mylar have been well studied and documented over the years; however, many of the mechanisms responsible for dielectric breakdown and failure are not understood for modified versions of the material. Previous studies on Mylar confirm that factors such as temperature, humidity, and voltage ramp rates can also have a significant effect on the dielectric properties and measurement of the dielectric properties. This study seeks to determine how dielectric properties, including permittivity, dielectric loss, and breakdown strength, aremore » affected by doping of the polymer. To do this, two types of Mylar films, virgin film and film doped with a small-molecule electron-acceptor, are tested. Both types of materials are tested under a variety of environmental and experimental conditions, including testing at elevated temperatures, varying relative humidity, and varying ramp rates in dielectric breakdown testing. Analysis of permittivity, dielectric loss, and breakdown strength will be presented comparing virgin and doped Mylar to gain insight into the effects of doping with electron-acceptor molecules on dielectric properties under these varying environmental and test conditions.« less

Fabrication of photonic band gap materials

DOEpatents

Constant, Kristen; Subramania, Ganapathi S.; Biswas, Rana; Ho, Kai-Ming

2002-01-15

A method for forming a periodic dielectric structure exhibiting photonic band gap effects includes forming a slurry of a nano-crystalline ceramic dielectric or semiconductor material and monodisperse polymer microspheres, depositing a film of the slurry on a substrate, drying the film, and calcining the film to remove the polymer microspheres therefrom. The film may be cold-pressed after drying and prior to calcining. The ceramic dielectric or semiconductor material may be titania, and the polymer microspheres may be polystyrene microspheres.

High-rate overcharge-protection separators for rechargeable lithium-ion batteries and the method of making the same

DOEpatents

Chen, Guoying; Richardson, Thomas J.

2016-12-20

This invention relates to low-cost, electroactive-polymer incorporated fine-fiber composite membranes for use as overcharge and/or overdischarge protection separators in non-aqueous electrochemical cells and the methods for making such membranes.

Solid electrolytes

DOEpatents

Abraham, Kuzhikalail M.; Alamgir, Mohamed

1993-06-15

This invention pertains to Li ion (Li.sup.+) conductive solid polymer electrolytes composed of solvates of Li salts immobilized (encapsulated) in a solid organic polymer matrix. In particular, this invention relates to solid polymer electrolytes derived by immobilizing complexes (solvates) formed between a Li salt such as LiAsF.sub.6, LiCF.sub.3 SO.sub.3 or LiClO.sub.4 and a mixture of aprotic organic solvents having high dielectric constants such as ethylene carbonate (EC) (dielectric constant=89.6) and propylene carbonate (PC) (dielectric constant=64.4) in a polymer matrix such as polyacrylonitrile, poly(tetraethylene glycol diacrylate), or poly(vinyl pyrrolidinone).

Process and Microstructure to Achieve Ultra-high Dielectric Constant in Ceramic-Polymer Composites.

PubMed

Zhang, Lin; Shan, Xiaobing; Bass, Patrick; Tong, Yang; Rolin, Terry D; Hill, Curtis W; Brewer, Jeffrey C; Tucker, Dennis S; Cheng, Z-Y

2016-10-21

Influences of process conditions on microstructure and dielectric properties of ceramic-polymer composites are systematically studied using CaCu 3 Ti 4 O 12 (CCTO) as filler and P(VDF-TrFE) 55/45 mol.% copolymer as the matrix by combining solution-cast and hot-pressing processes. It is found that the dielectric constant of the composites can be significantly enhanced-up to about 10 times - by using proper processing conditions. The dielectric constant of the composites can reach more than 1,000 over a wide temperature range with a low loss (tan δ ~ 10 -1 ). It is concluded that besides the dense structure of composites, the uniform distribution of the CCTO particles in the matrix plays a key role on the dielectric enhancement. Due to the influence of the CCTO on the microstructure of the polymer matrix, the composites exhibit a weaker temperature dependence of the dielectric constant than the polymer matrix. Based on the results, it is also found that the loss of the composites at low temperatures, including room temperature, is determined by the real dielectric relaxation processes including the relaxation process induced by the mixing.

Process and Microstructure to Achieve Ultra-high Dielectric Constant in Ceramic-Polymer Composites

NASA Astrophysics Data System (ADS)

Zhang, Lin; Shan, Xiaobing; Bass, Patrick; Tong, Yang; Rolin, Terry D.; Hill, Curtis W.; Brewer, Jeffrey C.; Tucker, Dennis S.; Cheng, Z.-Y.

2016-10-01

Influences of process conditions on microstructure and dielectric properties of ceramic-polymer composites are systematically studied using CaCu3Ti4O12 (CCTO) as filler and P(VDF-TrFE) 55/45 mol.% copolymer as the matrix by combining solution-cast and hot-pressing processes. It is found that the dielectric constant of the composites can be significantly enhanced-up to about 10 times - by using proper processing conditions. The dielectric constant of the composites can reach more than 1,000 over a wide temperature range with a low loss (tan δ ~ 10-1). It is concluded that besides the dense structure of composites, the uniform distribution of the CCTO particles in the matrix plays a key role on the dielectric enhancement. Due to the influence of the CCTO on the microstructure of the polymer matrix, the composites exhibit a weaker temperature dependence of the dielectric constant than the polymer matrix. Based on the results, it is also found that the loss of the composites at low temperatures, including room temperature, is determined by the real dielectric relaxation processes including the relaxation process induced by the mixing.

Process and Microstructure to Achieve Ultra-high Dielectric Constant in Ceramic-Polymer Composites

PubMed Central

Zhang, Lin; Shan, Xiaobing; Bass, Patrick; Tong, Yang; Rolin, Terry D.; Hill, Curtis W.; Brewer, Jeffrey C.; Tucker, Dennis S.; Cheng, Z.-Y.

2016-01-01

Influences of process conditions on microstructure and dielectric properties of ceramic-polymer composites are systematically studied using CaCu3Ti4O12 (CCTO) as filler and P(VDF-TrFE) 55/45 mol.% copolymer as the matrix by combining solution-cast and hot-pressing processes. It is found that the dielectric constant of the composites can be significantly enhanced–up to about 10 times – by using proper processing conditions. The dielectric constant of the composites can reach more than 1,000 over a wide temperature range with a low loss (tan δ ~ 10−1). It is concluded that besides the dense structure of composites, the uniform distribution of the CCTO particles in the matrix plays a key role on the dielectric enhancement. Due to the influence of the CCTO on the microstructure of the polymer matrix, the composites exhibit a weaker temperature dependence of the dielectric constant than the polymer matrix. Based on the results, it is also found that the loss of the composites at low temperatures, including room temperature, is determined by the real dielectric relaxation processes including the relaxation process induced by the mixing. PMID:27767184

Heterogeneous nucleation of polymorphs on polymer surfaces: polymer-molecule interactions using a heterogeneous dielectric solvation model.

PubMed

Wahlberg, Nanna; Madsen, Anders Ø; Mikkelsen, Kurt V

2018-06-09

We have investigated the mechanism of the nucleation of acetaminophen on poly(methyl-methacrylate) and poly(vinyl-acetate) utilizing a combination of quantum mechanical computations and electrostatic models. We have used a heterogeneous dielectric solvation model to determine the stability of different orientations of acetaminophen on polymer surfaces. We find that for the nucleation of acetaminophen on the polymer surfaces in vacuum, the most stable orientation is a flat orientation. For the nucleation process in solution where acetaminophen and the polymer surface are surrounded by a solvent, we find that the heterogeneous dielectric solvation model predicts that a sideways orientation is the most stable orientation.

Electroactive polymer and shape memory alloy actuators in biomimetics and humanoids

NASA Astrophysics Data System (ADS)

Tadesse, Yonas

2013-04-01

There is a strong need to replicate natural muscles with artificial materials as the structure and function of natural muscle is optimum for articulation. Particularly, the cylindrical shape of natural muscle fiber and its interconnected structure promote the critical investigation of artificial muscles geometry and implementation in the design phase of certain platforms. Biomimetic robots and Humanoid Robot heads with Facial Expressions (HRwFE) are some of the typical platforms that can be used to study the geometrical effects of artificial muscles. It has been shown that electroactive polymer and shape memory alloy artificial muscles and their composites are some of the candidate materials that may replicate natural muscles and showed great promise for biomimetics and humanoid robots. The application of these materials to these systems reveals the challenges and associated technologies that need to be developed in parallel. This paper will focus on the computer aided design (CAD) models of conductive polymer and shape memory alloys in various biomimetic systems and Humanoid Robot with Facial Expressions (HRwFE). The design of these systems will be presented in a comparative manner primarily focusing on three critical parameters: the stress, the strain and the geometry of the artificial muscle.

Silicone Membranes to Inhibit Water Uptake into Thermoset Polyurethane Shape-Memory Polymer Conductive Composites

PubMed Central

Yu, Ya-Jen; Infanger, Stephen; Grunlan, Melissa A.; Maitland, Duncan J.

2014-01-01

Electroactive shape memory polymer (SMP) composites capable of shape actuation via resistive heating are of interest for various biomedical applications. However, water uptake into SMPs will produce a depression of the glass transition temperature (Tg) resulting in shape recovery in vivo. While water actuated shape recovery may be useful, it is foreseen to be undesirable during early periods of surgical placement into the body. Silicone membranes have been previously reported to prevent release of conductive filler from an electroactive polymer composite in vivo. In this study, a silicone membrane was used to inhibit water uptake into a thermoset SMP composite containing conductive filler. Thermoset polyurethane (PU) SMPs were loaded with either 5 wt% carbon black (CB) or 5 wt% carbon nanotubes (CNT) and subsequently coated with either an Al2O3- or silica-filled silicone membrane. It was observed that the silicone membranes, particularly the silica-filled membrane, reduced the rate of water absorption (37 °C) and subsequent Tg depression versus uncoated composites. In turn, this led to a reduction in the rate of recovery of the permanent shape when exposed to water at 37 °C. PMID:25663711

Silicone Membranes to Inhibit Water Uptake into Thermoset Polyurethane Shape-Memory Polymer Conductive Composites.

PubMed

Yu, Ya-Jen; Infanger, Stephen; Grunlan, Melissa A; Maitland, Duncan J

2015-01-05

Electroactive shape memory polymer (SMP) composites capable of shape actuation via resistive heating are of interest for various biomedical applications. However, water uptake into SMPs will produce a depression of the glass transition temperature ( T g ) resulting in shape recovery in vivo . While water actuated shape recovery may be useful, it is foreseen to be undesirable during early periods of surgical placement into the body. Silicone membranes have been previously reported to prevent release of conductive filler from an electroactive polymer composite in vivo . In this study, a silicone membrane was used to inhibit water uptake into a thermoset SMP composite containing conductive filler. Thermoset polyurethane (PU) SMPs were loaded with either 5 wt% carbon black (CB) or 5 wt% carbon nanotubes (CNT) and subsequently coated with either an Al 2 O 3 - or silica-filled silicone membrane. It was observed that the silicone membranes, particularly the silica-filled membrane, reduced the rate of water absorption (37 °C) and subsequent T g depression versus uncoated composites. In turn, this led to a reduction in the rate of recovery of the permanent shape when exposed to water at 37 °C.

Silicone membranes to inhibit water uptake into thermoset polyurethane shape-memory polymer conductive composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, Ya-Jen; Infanger, Stephen; Grunlan, Melissa A.

Electroactive shape memory polymer (SMP) composites capable of shape actuation via resistive heating are of interest for various biomedical applications. However, water uptake into SMPs will produce a depression of the glass transition temperature (T g) resulting in shape recovery in vivo. While water actuated shape recovery may be useful, it is foreseen to be undesirable during early periods of surgical placement into the body. Silicone membranes have been previously reported to prevent release of conductive filler from an electroactive polymer composite in vivo. In this paper, a silicone membrane was used to inhibit water uptake into a thermoset SMPmore » composite containing conductive filler. Thermoset polyurethane SMPs were loaded with either 5 wt % carbon black or 5 wt % carbon nanotubes, and subsequently coated with either an Al 2O 3- or silica-filled silicone membrane. It was observed that the silicone membranes, particularly the silica-filled membrane, reduced the rate of water absorption (37°C) and subsequent T g depression versus uncoated composites. Finally, in turn, this led to a reduction in the rate of recovery of the permanent shape when exposed to water at 37°C.« less

Silicone membranes to inhibit water uptake into thermoset polyurethane shape-memory polymer conductive composites

DOE PAGES

Yu, Ya-Jen; Infanger, Stephen; Grunlan, Melissa A.; ...

2014-07-24

Electroactive shape memory polymer (SMP) composites capable of shape actuation via resistive heating are of interest for various biomedical applications. However, water uptake into SMPs will produce a depression of the glass transition temperature (T g) resulting in shape recovery in vivo. While water actuated shape recovery may be useful, it is foreseen to be undesirable during early periods of surgical placement into the body. Silicone membranes have been previously reported to prevent release of conductive filler from an electroactive polymer composite in vivo. In this paper, a silicone membrane was used to inhibit water uptake into a thermoset SMPmore » composite containing conductive filler. Thermoset polyurethane SMPs were loaded with either 5 wt % carbon black or 5 wt % carbon nanotubes, and subsequently coated with either an Al 2O 3- or silica-filled silicone membrane. It was observed that the silicone membranes, particularly the silica-filled membrane, reduced the rate of water absorption (37°C) and subsequent T g depression versus uncoated composites. Finally, in turn, this led to a reduction in the rate of recovery of the permanent shape when exposed to water at 37°C.« less

High Performance Electroactive Polymer Actuators Based on Sulfonated Block Copolymers Comprising Ionic Liquids

NASA Astrophysics Data System (ADS)

Kim, Onnuri; Park, Moon Jeong

2015-03-01

Electroactive polymer (EAP) actuators that show reversible deformation under external electric stimulus have attracted great attention toward a range of biomimetic applications such as microsensors and artificial muscles. Key challenges to advance the technologies can be placed on the achievement of fast response time, low driving voltage, and durable operation in air. In present study, we are motivated to solve these issues by employing self-assembled block copolymers containing ionic liquids (ILs) as polymer layers in the actuator based on knowledge of factors affecting electromechanical properties of actuators. By controlling the block architecture and molecular weight of block copolymers, bending strain and durability were controlled in a straightforward manner. It has also been revealed that the type of IL makes impact on the EAP actuator performance by determining ion migration dynamics. Our actuators demonstrated large bending strains (up to 4%) under low voltages of 1-3V, which far exceeds the best performance of other EAP actuators reported in the literature. To underpin the molecular-level understanding of actuation mechanisms underlying the improved performance, we carried out in situ spectroscopy and in situ scattering experiments under actuation.

Preparation and unique electrical behaviors of monodispersed hybrid nanorattles of metal nanocores with hairy electroactive polymer shells.

PubMed

Cai, Tao; Zhang, Bin; Chen, Yu; Wang, Cheng; Zhu, Chun Xiang; Neoh, Koon-Gee; Kang, En-Tang

2014-03-03

A versatile template-assisted strategy for the preparation of monodispersed rattle-type hybrid nanospheres, encapsulating a movable Au nanocore in the hollow cavity of a hairy electroactive polymer shell (Au@air@PTEMA-g-P3HT hybrid nanorattles; PTEMA: poly(2-(thiophen-3-yl)ethyl methacrylate; P3HT: poly(3-hexylthiophene), was reported. The Au@silica core-shell nanoparticles, prepared by the modified Stöber sol-gel process on Au nanoparticle seeds, were used as templates for the synthesis of Au@silica@PTEMA core-double shell nanospheres. Subsequent oxidative graft polymerization of 3-hexylthiophene from the exterior surface of the Au@silica@PTEMA core-double shell nanospheres allowed the tailoring of surface functionality with electroactive P3HT brushes (Au@silica@PTEMA-g-P3HT nanospheres). The Au@air@ PTEMA-g-P3HT hybrid nanorattles were obtained after etching of the silica interlayer by HF. The as-prepared nanorattles were dispersed into an electrically insulating polystyrene matrix and for the first time used to fabricate nonvolatile memory devices. As a result, unique electrical behaviors, including insulator behavior, write-once-read-many-times and rewritable memory effects, and conductor behavior as well, were observed in the Al/Au@air@PTEMA-g-P3HT+PS/ITO (ITO: indium-tin oxide) sandwich thin-film devices. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Investigation of dielectric properties of polymer composites reinforced with carbon nanotubes in the frequency band of 0.01 Hz - 10 MHz

NASA Astrophysics Data System (ADS)

Goshev, A. A.; Eseev, M. K.; Kapustin, S. N.; Vinnik, L. N.; Volkov, A. S.

2016-08-01

The goal of this work is experimental study of dielectric properties of polymer nanocomposites reinforced with multiwalled carbon nanotubes (MWCNTs) in alternating electric field in low frequency band of 0.01 Hz - 10 MHz. We investigated the influence, functionalization degree, aspect ratio, concentration of carbon nanotubes (CNTs) on dielectric properties of polymer sample. We also studied the dependence of dielectric properties on the polymerization temperature. The dependence of CNTs agglomeration on sample polymerization temperature and temperature's influence on conductivity has been shown. We conducted model calculation of percolation threshold and figured out its dependence on CNTs aspect ratio.

Energy storage in ferroelectric polymer nanocomposites filled with core-shell structured polymer@BaTiO3 nanoparticles: understanding the role of polymer shells in the interfacial regions.

PubMed

Zhu, Ming; Huang, Xingyi; Yang, Ke; Zhai, Xing; Zhang, Jun; He, Jinliang; Jiang, Pingkai

2014-11-26

The interfacial region plays a critical role in determining the electrical properties and energy storage density of dielectric polymer nanocomposites. However, we still know a little about the effects of electrical properties of the interfacial regions on the electrical properties and energy storage of dielectric polymer nanocomposites. In this work, three types of core-shell structured polymer@BaTiO3 nanoparticles with polymer shells having different electrical properties were used as fillers to prepare ferroelectric polymer nanocomposites. All the polymer@BaTiO3 nanoparticles were prepared by surface-initiated reversible-addition-fragmentation chain transfer (RAFT) polymerization, and the polymer shells were controlled to have the same thickness. The morphology, crystal structure, frequency-dependent dielectric properties, breakdown strength, leakage currents, energy storage capability, and energy storage efficiency of the polymer nanocomposites were investigated. On the other hand, the pure polymers having the same molecular structure as the shells of polymer@BaTiO3 nanoparticles were also prepared by RAFT polymerization, and their electrical properties were provided. Our results show that, to achieve nanocomposites with high discharged energy density, the core-shell nanoparticle filler should simultaneously have high dielectric constant and low electrical conductivity. On the other hand, the breakdown strength of the polymer@BaTiO3-based nanocomposites is highly affected by the electrical properties of the polymer shells. It is believed that the electrical conductivity of the polymer shells should be as low as possible to achieve nanocomposites with high breakdown strength.

Wirelessly Controllable Inflated Electroactive Polymer (EAP) Reflectors

NASA Technical Reports Server (NTRS)

Bao, Xiaoqi; Bar-Cohen, Yoseph; Chang, Zensheu; Sherrit, Stewart; Badescu, Mircea

2005-01-01

Inflatable membrane reflectors are attractive for deployable, large aperture, lightweight optical and microwave systems in micro-gravity space environment. However, any fabrication flaw or temperature variation may results in significant aberration of the surface. Even for a perfectly fabricated inflatable membrane mirror with uniform thickness, theory shows it will form a Hencky curve surface but a desired parabolic or spherical surface. Precision control of the surfaceshape of extremely flexible membrane structures is a critical challenge for the success of this technology. Wirelessly controllable inflated reflectors made of electroactive polymers (EAP) are proposed in this paper. A finite element model was configured to predict the behavior of the inflatable EAP membranes under pre-strains, pressures and distributed electric charges on the surface. To explore the controllability of the inflatable EAP reflectors, an iteration algorism was developed to find the required electric actuation for correcting the aberration of the Hencky curve to the desired parabolic curve. The correction capability of the reflectors with available EAP materials was explored numerically and is presented in this paper.

Modelling electro-active polymers with a dispersion-type anisotropy

NASA Astrophysics Data System (ADS)

Hossain, Mokarram; Steinmann, Paul

2018-02-01

We propose a novel constitutive framework for electro-active polymers (EAPs) that can take into account anisotropy with a chain dispersion. To enhance actuation behaviour, particle-filled EAPs become promising candidates nowadays. Recent studies suggest that particle-filled EAPs, which can be cured under an electric field during the manufacturing time, do not necessarily form perfect anisotropic composites, rather they create composites with dispersed chains. Hence in this contribution, an electro-mechanically coupled constitutive model is devised that considers the chain dispersion with a probability distribution function in an integral form. To obtain relevant quantities in discrete form, numerical integration over the unit sphere is utilized. Necessary constitutive equations are derived exploiting the basic laws of thermodynamics that result in a thermodynamically consistent formulation. To demonstrate the performance of the proposed electro-mechanically coupled framework, we analytically solve a non-homogeneous boundary value problem, the extension and inflation of an axisymmetric cylindrical tube under electro-mechanically coupled load. The results capture various electro-mechanical couplings with the formulation proposed for EAP composites.

Investigations on an electroactive polymer based tunable Helmholtz resonator

NASA Astrophysics Data System (ADS)

Abbad, A.; Rabenorosoa, K.; Ouisse, M.; Atalla, N.

2017-04-01

A Helmholtz resonator is a passive acoustic resonator classically used to control a single frequency resulting from the cavity volume and the resonator neck size. The aim of the proposed study is to present a new concept and strategy allowing real-time tunability of the Helmholtz resonator in order to enhance acoustic absorption performances at low frequencies (< 500 Hz). The proposed concept consists in replacing the resonator rigid front plate by an electroactive polymer (EAP) membrane. The first proposed strategy consists on a change in the mechanical properties of the membrane resulting from the applied electric field. This induces a resonance frequency shift. A second strategy is based on a well-located spring, which could direct the membrane deformation following the axis of the resonator to obtain a cavity volume variation. Both strategies allow variation of the resonance frequency of the device. Experimental measurements are performed to determine the potential of this concept for improvement of low-frequency performances of the acoustic devices.

Enhancing electrical energy storage capability of dielectric polymer nanocomposites via the room temperature Coulomb blockade effect of ultra-small platinum nanoparticles.

PubMed

Wang, Liwei; Huang, Xingyi; Zhu, Yingke; Jiang, Pingkai

2018-02-14

Introducing a high dielectric constant (high-k) nanofiller into a dielectric polymer is the most common way to achieve flexible nanocomposites for electrostatic energy storage devices. However, the significant decrease of breakdown strength and large increase of dielectric loss has long been known as the bottleneck restricting the enhancement of practical energy storage capability of the nanocomposites. In this study, by introducing ultra-small platinum (<2 nm) nanoparticles, high-k polymer nanocomposites with high breakdown strength and low dielectric loss were prepared successfully. Core-shell structured polydopamine@BaTiO 3 (PDA@BT) and core-satellite ultra-small platinum decorated PDA@BT (Pt@PDA@BT) were used as nanofillers. Compared with PDA@BT nanocomposites, the maximum discharged energy density of the Pt@PDA@BT nanocomposites is increased by nearly 70% because of the improved energy storage efficiency. This research provides a simple, promising and unique way to enhance energy storage capability of high-k polymer nanocomposites.

Zinc oxide nanowire-poly(methyl methacrylate) dielectric layers for polymer capacitive pressure sensors.

PubMed

Chen, Yan-Sheng; Hsieh, Gen-Wen; Chen, Shih-Ping; Tseng, Pin-Yen; Wang, Cheng-Wei

2015-01-14

Polymer capacitive pressure sensors based on a dielectric composite layer of zinc oxide nanowire and poly(methyl methacrylate) show pressure sensitivity in the range of 2.63 × 10(-3) to 9.95 × 10(-3) cm(2) gf(-1). This represents an increase of capacitance change by as much as a factor of 23 over pristine polymer devices. An ultralight load of only 10 mg (corresponding to an applied pressure of ∼0.01 gf cm(-2)) can be clearly recognized, demonstrating remarkable characteristics of these nanowire-polymer capacitive pressure sensors. In addition, optical transmittance of the dielectric composite layer is approximately 90% in the visible wavelength region. Their low processing temperature, transparency, and flexible dielectric film makes them a highly promising means for flexible touching and pressure-sensing applications.

Holographic Structuring of Elastomer Actuator: First True Monolithic Tunable Elastomer Optics.

PubMed

Ryabchun, Alexander; Kollosche, Matthias; Wegener, Michael; Sakhno, Oksana

2016-12-01

Volume diffraction gratings (VDGs) are inscribed selectively by diffusive introduction of benzophenone and subsequent UV-holographic structuring into an electroactive dielectric elastomer actuator (DEA), to afford a continuous voltage-controlled grating shift of 17%. The internal stress coupling of DEA and optical domain allows for a new generation of true monolithic tunable elastomer optics with voltage controlled properties. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Scoping the polymer genome: A roadmap for rational polymer dielectrics design and beyond

DOE PAGES

Mannodi-Kanakkithodi, Arun; Chandrasekaran, Anand; Kim, Chiho; ...

2017-12-19

The Materials Genome Initiative (MGI) has heralded a sea change in the philosophy of materials design. In an increasing number of applications, the successful deployment of novel materials has benefited from the use of computational methodologies, data descriptors, and machine learning. Polymers have long suffered from a lack of data on electronic, mechanical, and dielectric properties across large chemical spaces, causing a stagnation in the set of suitable candidates for various applications. Extensive efforts over the last few years have seen the fruitful application of MGI principles toward the accelerated discovery of attractive polymer dielectrics for capacitive energy storage. Here,more » we review these efforts, highlighting the importance of computational data generation and screening, targeted synthesis and characterization, polymer fingerprinting and machine-learning prediction models, and the creation of an online knowledgebase to guide ongoing and future polymer discovery and design. We lay special emphasis on the fingerprinting of polymers in terms of their genome or constituent atomic and molecular fragments, an idea that pays homage to the pioneers of the human genome project who identified the basic building blocks of the human DNA. As a result, by scoping the polymer genome, we present an essential roadmap for the design of polymer dielectrics, and provide future perspectives and directions for expansions to other polymer subclasses and properties.« less

Scoping the polymer genome: A roadmap for rational polymer dielectrics design and beyond

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mannodi-Kanakkithodi, Arun; Chandrasekaran, Anand; Kim, Chiho

The Materials Genome Initiative (MGI) has heralded a sea change in the philosophy of materials design. In an increasing number of applications, the successful deployment of novel materials has benefited from the use of computational methodologies, data descriptors, and machine learning. Polymers have long suffered from a lack of data on electronic, mechanical, and dielectric properties across large chemical spaces, causing a stagnation in the set of suitable candidates for various applications. Extensive efforts over the last few years have seen the fruitful application of MGI principles toward the accelerated discovery of attractive polymer dielectrics for capacitive energy storage. Here,more » we review these efforts, highlighting the importance of computational data generation and screening, targeted synthesis and characterization, polymer fingerprinting and machine-learning prediction models, and the creation of an online knowledgebase to guide ongoing and future polymer discovery and design. We lay special emphasis on the fingerprinting of polymers in terms of their genome or constituent atomic and molecular fragments, an idea that pays homage to the pioneers of the human genome project who identified the basic building blocks of the human DNA. As a result, by scoping the polymer genome, we present an essential roadmap for the design of polymer dielectrics, and provide future perspectives and directions for expansions to other polymer subclasses and properties.« less

High-Energy-Density Capacitors

NASA Technical Reports Server (NTRS)

Slenes, Kirk

2003-01-01

Capacitors capable of storing energy at high densities are being developed for use in pulse-power circuits in such diverse systems as defibrillators, particle- beam accelerators, microwave sources, and weapons. Like typical previously developed energy-storage capacitors, these capacitors are made from pairs of metal/solid-dielectric laminated sheets that are wound and pressed into compact shapes to fit into cans, which are then filled with dielectric fluids. Indeed, these capacitors can be fabricated largely by conventional fabrication techniques. The main features that distinguish these capacitors from previously developed ones are improvements in (1) the selection of laminate materials, (2) the fabrication of the laminated sheets from these materials, and (3) the selection of dielectric fluids. In simplest terms, a high-performance laminated sheet of the type used in these capacitors is made by casting a dielectric polymer onto a sheet of aluminized kraft paper. The dielectric polymer is a siloxane polymer that has been modified with polar pendant groups to increase its permittivity and dielectric strength. Potentially, this polymer is capable of withstanding an energy density of 7.5 J/cm3, which is four times that of the previous state-of-the-art-capacitor dielectric film material. However, the full potential of this polymer cannot be realized at present because (1) at thicknesses needed for optimum performance (.8.0 m), the mechanical strength of a film of this polymer is insufficient for incorporation into a wound capacitor and (2) at greater thickness, the achievable energy density decreases because of a logarithmic decrease in dielectric strength with increasing thickness. The aluminized kraft paper provides the mechanical strength needed for processing of the laminate and fabrication of the capacitor, and the aluminum film serves as an electrode layer. Because part of the thickness of the dielectric is not occupied by the modified siloxane polymer, the achievable energy density must be somewhat less than the maximum value. The laminate is produced by a continuous film-casting process, using the machinery depicted schematically in the figure. The designs of the process and machinery are dictated partly by the fact that during the processing step prior to casting the polymer, the aluminized kraft paper becomes wet with water. Because the polymer resin to be cast is hydrophobic, the paper must be dried to make it possible to coat the paper uniformly, leaving no pinholes. Accordingly, an infrared heater is placed next to the paper feed roll to dry the paper prior to casting.

Artificial Muscle Devices: Innovations and Prospects for Fecal Incontinence Treatment.

PubMed

Fattorini, Elisa; Brusa, Tobia; Gingert, Christian; Hieber, Simone E; Leung, Vanessa; Osmani, Bekim; Dominietto, Marco D; Büchler, Philippe; Hetzer, Franc; Müller, Bert

2016-05-01

Fecal incontinence describes the involuntary loss of bowel content, which is responsible for stigmatization and social exclusion. It affects about 45% of retirement home residents and overall more than 12% of the adult population. Severe fecal incontinence can be treated by the implantation of an artificial sphincter. Currently available implants, however, are not part of everyday surgery due to long-term re-operation rates of 95% and definitive explantation rates of 40%. Such figures suggest that the implants fail to reproduce the capabilities of the natural sphincter. This article reviews the artificial sphincters on the market and under development, presents their physical principles of operation and critically analyzes their performance. We highlight the geometrical and mechanical parameters crucial for the design of an artificial fecal sphincter and propose more advanced mechanisms of action for a biomimetic device with sensory feedback. Dielectric electro-active polymer actuators are especially attractive because of their versatility, response time, reaction forces, and energy consumption. The availability of such technology will enable fast pressure adaption comparable to the natural feedback mechanism, so that tissue atrophy and erosion can be avoided while maintaining continence during daily activities.

Electromechanical response of reduced graphene oxide-polyvinylidene fluoride nanocomposites prepared through in-situ thermal reduction

NASA Astrophysics Data System (ADS)

Sigamani, Nirmal; Ounaies, Zoubeida; Ehlert, Greg; Sodano, Henry

2015-04-01

Carbon fillers, such as carbon nanotubes, have been used to address drawbacks of existing electroactive polymers (EAPs) with varying success. More recently, there has been interest in investigating potential of 2D graphene in improving the actuation response of EAPs, owing to its unique geometry and electrical properties. In our study, the effect of graphene oxide (GO) nanosheets on electromechanical response of polyvinylidene fluoride (PVDF)-based nanocomposites is studied. We show that incorporating GO produces considerable strain under an applied electric field when processed using a co-solvent approach involving water and N, N dimethylformamide. Starting with GO enables good dispersion and interaction with PVDF and then thermally reducing it in-situ yields EAP with some controllability over the desired properties. A key result is that the extensional strain S11 is quadratic with the electric field, which suggests electric field-induced electrostrictive response. Dielectric relaxation spectroscopy results indicate that the mechanism for the electrostrictive response is due to induced polarization resulting from the enhanced dipolar mobility from polar γ-phase PVDF and reduced GO. Finally, we show that the coefficient of electrostriction depends on the GO content and on the amount of conversion from GO to reduced GO.

Using a novel rigid-fluoride polymer to control the interfacial thickness of graphene and tailor the dielectric behavior of poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) nanocomposites.

PubMed

Han, Xianghui; Chen, Sheng; Lv, Xuguang; Luo, Hang; Zhang, Dou; Bowen, Chris R

2018-01-24

Polymer nanocomposites based on conductive fillers for high performance dielectrics have attracted increasing attention in recent years. However, a number of physical issues are unclear, such as the effect of interfacial thickness on the dielectric properties of the polymer nanocomposites, which limits the enhancement of permittivity. In this research, two core-shell structured reduced graphene oxide (rGO)@rigid-fluoro-polymer conducting fillers with different shell thicknesses are prepared using a surface-initiated reversible-addition-fragmentation chain transfer polymerization method, which are denoted as rGO@PTFMS-1 with a thin shell and rGO@PTFMS-2 with a thick shell. A rigid liquid crystalline fluoride-polymer poly{5-bis[(4-trifluoro-methoxyphenyl)oxycarbonyl]styrene} (PTFMS) is chosen for the first time to tailor the shell thicknesses of rGO via tailoring the degree of polymerization. The effect of interfacial thickness on the dielectric behavior of the P(VDF-TrFE-CTFE) nanocomposites with rGO and modified rGO is studied in detail. The results demonstrate that the percolation threshold of the nanocomposites increased from 0.68 vol% to 1.69 vol% with an increase in shell thickness. Compared to the rGO@PTFMS-1/P(VDF-TrFE-CTFE) composites, the rGO@PTFMS-2/P(VDF-TrFE-CTFE) composites exhibited a higher breakdown strength and a lower dielectric constant, which can be interpreted by interfacial polarization and the micro-capacitor model, resulting from the insulating nature of the rigid-polymer shell and the change of rGO's morphology. The findings provide an innovative approach to tailor dielectric composites, and promote a deeper understanding of the influence of interfacial region thickness on the dielectric performance.

Microfabrication and characterization of an array of dielectric elastomer actuators generating uniaxial strain to stretch individual cells

NASA Astrophysics Data System (ADS)

Akbari, S.; Shea, H. R.

2012-04-01

Cells regulate their behavior in response to mechanical strains. Cell cultures to study mechanotransuction are typically cm2 in area, far too large to monitor single cell response. We have developed an array of dielectric elastomer microactuators as a tool to study mechanotransduction of individual cells. The array consists of 72 100 µm × 200 µm electroactive polymer actuators which expand uniaxially when a voltage is applied. Single cells will be attached on each actuator to study their response to periodic mechanical strains. The device is fabricated by patterning compliant microelectrodes on both sides of a 30 µm thick polydimethylsiloxane membrane, which is bonded to a Pyrex chip with 200 µm wide trenches. Low-energy metal ion implantation is used to make stretchable electrodes and we demonstrate here the successful miniaturization of such ion-implanted electrodes. The top electrode covers the full membrane area, while the bottom electrodes are 100 µm wide parallel lines, perpendicular to the trenches. Applying a voltage between the top and bottom electrodes leads to uniaxial expansion of the membrane at the intersection of the bottom electrodes and the trenches. To characterize the in-plane strain, an array of 4 µm diameter aluminum dots is deposited on each actuator. The position of each dot is tracked, allowing displacement and strain profiles to be measured as a function of voltage. The uniaxial strain reaches 4.7% at 2.9 kV with a 0.2 s response time, sufficient to stimulate most cells with relevant biological strains and frequencies.

Photoelectrochemical electrodes

NASA Technical Reports Server (NTRS)

Williams, R. M.; Rembaum, A. (Inventor)

1983-01-01

The surface of a moderate band gap semiconductor such as p-type molybdenum sulfide is modified to contain an adherent film of charge mediating ionene polymer containing an electroactive unit such as bipyridimium. Electron transport between the electrode and the mediator film is favorable and photocorrosion and recombination processes are suppressed. Incorporation of particles of catalyst such as platinum within the film provides a reduction in overvoltage. The polymer film is readily deposited on the electrode surface and can be rendered stable by ionic or addition crosslinking. Catalyst can be predispersed in the polymer film or a salt can be impregnated into the film and reduced therein.

Flexible, Low-Power Thin-Film Transistors Made of Vapor-Phase Synthesized High-k, Ultrathin Polymer Gate Dielectrics.

PubMed

Choi, Junhwan; Joo, Munkyu; Seong, Hyejeong; Pak, Kwanyong; Park, Hongkeun; Park, Chan Woo; Im, Sung Gap

2017-06-21

A series of high-k, ultrathin copolymer gate dielectrics were synthesized from 2-cyanoethyl acrylate (CEA) and di(ethylene glycol) divinyl ether (DEGDVE) monomers by a free radical polymerization via a one-step, vapor-phase, initiated chemical vapor deposition (iCVD) method. The chemical composition of the copolymers was systematically optimized by tuning the input ratio of the vaporized CEA and DEGDVE monomers to achieve a high dielectric constant (k) as well as excellent dielectric strength. Interestingly, DEGDVE was nonhomopolymerizable but it was able to form a copolymer with other kinds of monomers. Utilizing this interesting property of the DEGDVE cross-linker, the dielectric constant of the copolymer film could be maximized with minimum incorporation of the cross-linker moiety. To our knowledge, this is the first report on the synthesis of a cyanide-containing polymer in the vapor phase, where a high-purity polymer film with a maximized dielectric constant was achieved. The dielectric film with the optimized composition showed a dielectric constant greater than 6 and extremely low leakage current densities (<3 × 10 -8 A/cm 2 in the range of ±2 MV/cm), with a thickness of only 20 nm, which is an outstanding thickness for down-scalable cyanide polymer dielectrics. With this high-k dielectric layer, organic thin-film transistors (OTFTs) and oxide TFTs were fabricated, which showed hysteresis-free transfer characteristics with an operating voltage of less than 3 V. Furthermore, the flexible OTFTs retained their low gate leakage current and ideal TFT characteristics even under 2% applied tensile strain, which makes them some of the most flexible OTFTs reported to date. We believe that these ultrathin, high-k organic dielectric films with excellent mechanical flexibility will play a crucial role in future soft electronics.

A comparative study of nano-SiO2 and nano-TiO2 fillers on proton conductivity and dielectric response of a silicotungstic acid-H3PO4-poly(vinyl alcohol) polymer electrolyte.

PubMed

Gao, Han; Lian, Keryn

2014-01-08

The effects of nano-SiO2 and nano-TiO2 fillers on a thin film silicotungstic acid (SiWA)-H3PO4-poly(vinyl alcohol) (PVA) proton conducting polymer electrolyte were studied and compared with respect to their proton conductivity, environmental stability, and dielectric properties, across a temperature range from 243 to 323 K. Three major effects of these fillers have been identified: (a) barrier effect; (b) intrinsic dielectric constant effect; and (c) water retention effect. Dielectric analyses were used to differentiate these effects on polymer electrolyte-enabled capacitors. Capacitor performance was correlated to electrolyte properties through dielectric constant and dielectric loss spectra. Using a single-ion approach, proton density and proton mobility of each polymer electrolyte were derived as a function of temperature. The results allow us to deconvolute the different contributions to proton conductivity in SiWA-H3PO4-PVA-based electrolytes, especially in terms of the effects of fillers on the dynamic equilibrium of free protons and protonated water in the electrolytes.

Ferroelectric polymer dielectrics: Emerging materials for future electrostatic energy storage applications

NASA Astrophysics Data System (ADS)

Panda, Maheswar

2018-05-01

In this manuscript, the dielectric behavior of a variety of ferroelectric polymer dielectrics (FPD), which may bethe materials for future electrostatic energy storage application shave been discussed. The variety of polymer dielectrics, comprising of ferroelectric polymer[polyvinylidene fluoride (PVDF)]/non-polarpolymer [low density polyethylene (LDPE)] and different sizes of metal particles (Ni, quasicrystal of Al-Cu-Fe) as filler, were prepared through different process conditions (cold press/hot press) and are investigated experimentally. Very high values of effective dielectric constants (ɛeff) with low loss tangent (Tan δ) were observed forall the prepared FPD at their respective percolation thresholds (fc). The enhancement of ɛeff and Tan δ at the insulator to metal transition (IMT) is explained through the boundary layer capacitor effect and the percolation theory respectively. The non-universal fc/critical exponents across the IMT have been explained through percolation theory andis attributed to the fillerparticle size& shape, interaction between the components, method of their preparation, adhesiveness, connectivity and homogeneity, etc. of the samples. Recent results on developed FPD with high ɛeff and low Tan δ prepared through cold press have proven themselves to be the better candidates for low frequency and static dielectric applications.

Conjugated Polymers for Flexible Energy Harvesting and Storage.

PubMed

Zhang, Zhitao; Liao, Meng; Lou, Huiqing; Hu, Yajie; Sun, Xuemei; Peng, Huisheng

2018-03-01

Since the discovery of conjugated polymers in the 1970s, they have attracted considerable interest in light of their advantages of having a tunable bandgap, high electroactivity, high flexibility, and good processability compared to inorganic conducting materials. The above combined advantages make them promising for effective energy harvesting and storage, which have been widely studied in recent decades. Herein, the key advancements in the use of conjugated polymers for flexible energy harvesting and storage are reviewed. The synthesis, structure, and properties of conjugated polymers are first summarized. Then, their applications in flexible polymer solar cells, thermoelectric generators, supercapacitors, and lithium-ion batteries are described. The remaining challenges are then discussed to highlight the future direction in the development of conjugated polymers. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nanotube Film Electrode and an Electroactive Device Fabricated with the Nanotube Film Electrode and Methods for Making Same

NASA Technical Reports Server (NTRS)

Kang, Jin Ho (Inventor); Harrison, Joycelyn S. (Inventor); Park, Cheol (Inventor)

2017-01-01

Disclosed is a single wall carbon nanotube (SWCNT) film electrode (FE), all-organic electroactive device systems fabricated with the SWNT-FE, and methods for making same. The SWCNT can be replaced by other types of nanotubes. The SWCNT film can be obtained by filtering SWCNT solution onto the surface of an anodized alumina membrane. A freestanding flexible SWCNT film can be collected by breaking up this brittle membrane. The conductivity of this SWCNT film can advantageously be higher than 280 S/cm. An electroactive polymer (EAP) actuator layered with the SWNT-FE shows a higher electric field-induced strain than an EAP layered with metal electrodes because the flexible SWNT-FE relieves the restraint of the displacement of the polymeric active layer as compared to the metal electrode. In addition, if thin enough, the SWNT-FE is transparent in the visible light range, thus making it suitable for use in actuators used in optical devices.

Method of forming a multiple layer dielectric and a hot film sensor therewith

NASA Technical Reports Server (NTRS)

Hopson, Purnell, Jr. (Inventor); Tran, Sang Q. (Inventor)

1990-01-01

The invention is a method of forming a multiple layer dielectric for use in a hot-film laminar separation sensor. The multiple layer dielectric substrate is formed by depositing a first layer of a thermoelastic polymer such as on an electrically conductive substrate such as the metal surface of a model to be tested under cryogenic conditions and high Reynolds numbers. Next, a second dielectric layer of fused silica is formed on the first dielectric layer of thermoplastic polymer. A resistive metal film is deposited on selected areas of the multiple layer dielectric substrate to form one or more hot-film sensor elements to which aluminum electrical circuits deposited upon the multiple layered dielectric substrate are connected.

Electroactive Polymers With Anti-Counterfeiting Feature

DTIC Science & Technology

2010-09-28

to Braille printing), or different sizes of paper currency, are used to designate different denominations, which can be helpful to those who are...express a denomination (using any one or more of a visual display in large type) an aural report, or in a tactile manner, such as in Braille or

Electroactive Polymers as Artificial Muscles: Capabilities, Potentials and Challenges

NASA Technical Reports Server (NTRS)

Bar-Cohen, Yoseph

2000-01-01

The low density and the relative ease of shaping made polymers highly attractive materials and they are increasingly being chosen for aerospace applications. Polymer matrix composite materials significantly impacted the construction of high performance aircraft components and structures. In recent years, the resilience characteristics of polymers made them attractive to the emerging field of inflatable structures. Balloons were used to cushion the deployment of the Mars Pathfinder lander on July 4, 1997, paving the way for the recent large number of related initiatives. Inflatable structures are now being used to construct a rover, aerial vehicles, telescopes, radar antennas, and others. Some of these applications have reached space flight experiments, whereas others are now at advanced stages of development.

Physical and Electrical Characterization of Aluminum Polymer Capacitors

NASA Technical Reports Server (NTRS)

Liu, David; Sampson, Michael J.

2010-01-01

Polymer aluminum capacitors from several manufacturers with various combinations of capacitance, rated voltage, and ESR values were physically examined and electrically characterized. The physical construction analysis of the capacitors revealed three different capacitor structures, i.e., traditional wound, stacked, and laminated. Electrical characterization results of polymer aluminum capacitors are reported for frequency-domain dielectric response at various temperatures, surge breakdown voltage, and other dielectric properties. The structure-property relations in polymer aluminum capacitors are discussed.

Physical and Electrical Characterization of Polymer Aluminum Capacitors

NASA Technical Reports Server (NTRS)

Liu, David; Sampson, Michael J.

2010-01-01

Polymer aluminum capacitors from several manufacturers with various combinations of capacitance, rated voltage, and ESR values were physically examined and electrically characterized. The physical construction analysis of the capacitors revealed three different capacitor structures, i.e., traditional wound, stacked, and laminated. Electrical characterization results of polymer aluminum capacitors are reported for frequency-domain dielectric response at various temperatures, surge breakdown voltage, and other dielectric properties. The structure-property relations in polymer aluminum capacitors are discussed.

Space charge effects on the dielectric response of polymer nanocomposites

NASA Astrophysics Data System (ADS)

Shen, Zhong-Hui; Wang, Jian-Jun; Zhang, Xin; Lin, Yuanhua; Nan, Ce-Wen; Chen, Long-Qing; Shen, Yang

2017-08-01

Adding high-κ ceramic nanoparticles into polymers is a general strategy to improve the performances in energy storage. Classic effective medium theories may fail to predict the effective permittivity in polymer nanocomposites wherein the space charge effects are important. In this work, a computational model is developed to understand the space charge effects on the frequency-dependent dielectric properties including the real permittivity and the loss for polymer nanocomposites with both randomly distributed and aggregated nanoparticle fillers. It is found that the real permittivity of the SrTiO3/polyethylene (12% SrTiO3 in volume fraction) nanocomposite can be increased to as high as 60 when there is nanoparticle aggregation and the ion concentration in the bulk polymer is around 1016 cm-3. This model can be employed to quantitatively predict the frequency-dependent dielectric properties for polymer nanocomposites with arbitrary microstructures.

Improved Dielectric Properties and Energy Storage Density of Poly(vinylidene fluoride-co-hexafluoropropylene) Nanocomposite with Hydantoin Epoxy Resin Coated BaTiO3.

PubMed

Luo, Hang; Zhang, Dou; Jiang, Chao; Yuan, Xi; Chen, Chao; Zhou, Kechao

2015-04-22

Energy storage materials are urgently demanded in modern electric power supply and renewable energy systems. The introduction of inorganic fillers to polymer matrix represents a promising avenue for the development of high energy density storage materials, which combines the high dielectric constant of inorganic fillers with supernal dielectric strength of polymer matrix. However, agglomeration and phase separation of inorganic fillers in the polymer matrix remain the key barriers to promoting the practical applications of the composites for energy storage. Here, we developed a low-cost and environmentally friendly route to modifying BaTiO3 (BT) nanoparticles by a kind of water-soluble hydantoin epoxy resin. The modified BT nanoparticles exhibited homogeneous dispersion in the ferroelectric polymer poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) matrix and strong interfacial adhesion with the polymer matrix. The dielectric constants of the nanocomposites increased significantly with the increase of the coated BT loading, while the dielectric loss of the nanocomposites was still as low as that of the pure P(VDF-HFP). The energy storage density of the nanocomposites was largely enhanced with the coated BT loading at the same electric field. The nanocomposite with 20 vol % BT exhibited an estimated maximum energy density of 8.13 J cm(-3), which was much higher than that of pure P(VDF-HFP) and other dielectric polymers. The findings of this research could provide a feasible approach to produce high energy density materials for practical application in energy storage.

Low percolation transitions in carbon nanotube networks dispersed in a polymer matrix: dielectric properties, simulations and experiments.

PubMed

Simoes, Ricardo; Silva, Jaime; Vaia, Richard; Sencadas, Vítor; Costa, Pedro; Gomes, João; Lanceros-Méndez, Senentxu

2009-01-21

The low concentration behaviour and the increase of the dielectric constant in carbon nanotubes/polymer nanocomposites near the percolation threshold are still not well understood. In this work, a numerical model has been developed which focuses on the effect of the inclusion of conductive fillers in a dielectric polymer matrix on the dielectric constant and the dielectric strength. Experiments have been carried out in carbon nanotubes/poly(vinylidene fluoride) nanocomposites in order to compare to the simulation results. This work shows how the critical concentration is related to the formation of capacitor networks and that these networks give rise to high variations in the electrical properties of the composites. Based on numerical studies, the dependence of the percolation transition on the preparation of the nanocomposite is discussed. Finally, based on numerical and experimental results, both ours and from other authors, the causes of anomalous percolation behaviour of the dielectric constant are identified.

Synthesis, morphological, electromechanical characterization of (CaMgFex)Fe1-xTi3O12-δ/PDMS nanocomposite thin films for energy storage application

NASA Astrophysics Data System (ADS)

Tripathy, Ashis; Sharma, Priyaranjan; Sahoo, Narayan

2018-03-01

At the present time, flexible and stretchable electronics has intended to use the new cutting-edge technologies for advanced electronic application. Currently, Polymers are being employed for such applications but they are not effective due to their low dielectric constant. To enhance the dielectric properties of polymer for energy storage application, it is necessary to add ceramic material of high dielectric constant to synthesize a polymer-ceramic composite. Therefore, a novel attempt has been made to enhance the dielectric properties of the Polydimethylsiloxane (PDMS) polymer by adding (CaMgFex)Fe1-xTi3O12-δ(0 90%), which can make it a potential material for advanced flexible electronic devices, energy storage and biomedical applications.

Modeling and Simulation of Viscous Electro-Active Polymers

PubMed Central

Vogel, Franziska; Göktepe, Serdar; Steinmann, Paul; Kuhl, Ellen

2014-01-01

Electro-active materials are capable of undergoing large deformation when stimulated by an electric field. They can be divided into electronic and ionic electro-active polymers (EAPs) depending on their actuation mechanism based on their composition. We consider electronic EAPs, for which attractive Coulomb forces or local re-orientation of polar groups cause a bulk deformation. Many of these materials exhibit pronounced visco-elastic behavior. Here we show the development and implementation of a constitutive model, which captures the influence of the electric field on the visco-elastic response within a geometrically non-linear finite element framework. The electric field affects not only the equilibrium part of the strain energy function, but also the viscous part. To adopt the familiar additive split of the strain from the small strain setting, we formulate the governing equations in the logarithmic strain space and additively decompose the logarithmic strain into elastic and viscous parts. We show that the incorporation of the electric field in the viscous response significantly alters the relaxation and hysteresis behavior of the model. Our parametric study demonstrates that the model is sensitive to the choice of the electro-viscous coupling parameters. We simulate several actuator structures to illustrate the performance of the method in typical relaxation and creep scenarios. Our model could serve as a design tool for micro-electro-mechanical systems, microfluidic devices, and stimuli-responsive gels such as artificial skin, tactile displays, or artificial muscle. PMID:25267881

A brief survey of radiation effects on polymer dielectrics

NASA Technical Reports Server (NTRS)

Laghari, Javaid R.; Hammoud, Ahmad N.

1990-01-01

Future space power needs are extrapolated to be at least three to four orders of magnitude more than is currently available. This long-term reliable power will be required on missions such as the Space Station, Pathfinder, Space Plane, and high-powered satellites, and for defense. Electrical insulation and dielectrics are the key electrical materials needed to support these power systems, where a single-point system failure could prove catastrophic or even fatal for the whole mission. Therefore, the impact of radiation, an environmental stress, on the properties and performance of insulation and dielectrics must be understood. The influence of radiation on polymer dielectrics, the insulating materials most commonly used for power transmission and storage, is reviewed. The effects of the type of radiation, dose, rate, and total exposure on the key electrical, mechanical, and physical properties of polymer dielectrics are described and explained.

Lowest of AC-DC power output for electrostrictive polymers energy harvesting systems

NASA Astrophysics Data System (ADS)

Meddad, Mounir; Eddiai, Adil; Hajjaji, Abdelowahed; Guyomar, Daniel; Belkhiat, Saad; Boughaleb, Yahia; Chérif, Aida

2013-11-01

Advances in technology led to the development of electronic circuits and sensors with extremely low electricity consumption. At the same time, structural health monitoring, technology and intelligent integrated systems created a need for wireless sensors in hard to reach places in aerospace vehicles and large civil engineering structures. Powering sensors with energy harvesters eliminates the need to replace batteries on a regular basis. Scientists have been forced to search for new power source that are able to harvested energy from their surrounding environment (sunlight, temperature gradients etc.). Electrostrictive polymer belonging to the family of electro-active polymers, offer unique properties for the electromechanical transducer technology has been of particular interest over the last few years in order to replace conventional techniques such as those based on piezoelectric or electromagnetic, these materials are highly attractive for their low-density, with large strain capability that can be as high as two orders of magnitude greater than the striction-limited, rigid and fragile electroactive ceramics. Electrostrictive polymers sensors respond to vibration with an ac output signal, one of the most important objectives of the electronic interface is to realize the required AC-DC conversion. The goal of this paper is to design an active, high efficiency power doubler converter for electrostrictive polymers exclusively uses a fraction of the harvested energy to supply its active devices. The simulation results show that it is possible to obtain a maximum efficiency of the AC-DC converter equal to 80%. Premiliminary experimental measurements were performed and the results obtained are in good agreement with simulations.

Large-Deformation Curling Actuators Based on Carbon Nanotube Composite: Advanced-Structure Design and Biomimetic Application.

PubMed

Chen, Luzhuo; Weng, Mingcen; Zhou, Zhiwei; Zhou, Yi; Zhang, Lingling; Li, Jiaxin; Huang, Zhigao; Zhang, Wei; Liu, Changhong; Fan, Shoushan

2015-12-22

In recent years, electroactive polymers have been developed as actuator materials. As an important branch of electroactive polymers, electrothermal actuators (ETAs) demonstrate potential applications in the fields of artificial muscles, biomimetic devices, robotics, and so on. Large-shape deformation, low-voltage-driven actuation, and ultrafast fabrication are critical to the development of ETA. However, a simultaneous optimization of all of these advantages has not been realized yet. Practical biomimetic applications are also rare. In this work, we introduce an ultrafast approach to fabricate a curling actuator based on a newly designed carbon nanotube and polymer composite, which completely realizes all of the above required advantages. The actuator shows an ultralarge curling actuation with a curvature greater than 1.0 cm(-1) and bending angle larger than 360°, even curling into a tubular structure. The driving voltage is down to a low voltage of 5 V. The remarkable actuation is attributed not only to the mismatch in the coefficients of thermal expansion but also to the mechanical property changes of materials during temperature change. We also construct an S-shape actuator to show the possibility of building advanced-structure actuators. A weightlifting walking robot is further designed that exhibits a fast-moving motion while lifting a sample heavier than itself, demonstrating promising biomimetic applications.

On the impact of self-clearing on electroactive polymer (EAP) actuators

NASA Astrophysics Data System (ADS)

Ahmed, Saad; Ounaies, Zoubeida; Lanagan, Michael T.

2017-10-01

Electroactive polymer (EAP)-based actuators have large potential for a wide array of applications; however, their practical implementation is still a challenge because of the requirement of high driving voltage, which most often leads to premature defect-driven electrical breakdown. Polymer-based capacitors have the ability to clear defects with partial electrical breakdown and subsequent removal of a localized electrode section near the defect. In this study, this process, which is known as self-clearing, is adopted for EAP technologies. We report a methodical approach to self-clear an EAP, more specifically P(VDF-TrFE-CTFE) terpolymer, to delay premature defect-driven electrical breakdown of the terpolymer actuators at high operating electric fields. Breakdown results show that electrical breakdown strength is improved up to 18% in comparison to a control sample after self-clearing. Furthermore, the electromechanical performance in terms of blocked force and free displacement of P(VDF-TrFE-CTFE) terpolymer-based bending actuators are examined after self-clearing and precleared samples show improved blocked force, free displacement and maximum sustainable electric field compared to control samples. The study demonstrates that controlled self-clearing of EAPs improves the breakdown limit and reliability of the EAP actuators for practical applications without impeding their electromechanical performance.

Fabrication and actuation of electro-active polymer actuator based on PSMI-incorporated PVDF

NASA Astrophysics Data System (ADS)

Lu, Jun; Kim, Sang-Gyun; Lee, Sunwoo; Oh, Il-Kwon

2008-08-01

In this study, an ionic networking membrane (INM) of poly(styrene-alt-maleimide) (PSMI)-incorporated poly(vinylidene fluoride) (PVDF) was applied to fabricate electro-active polymer. Based on the same original membrane of PSMI-incorporated PVDF, various samples of INM actuator were prepared for different reduction times with the electroless-plating technique. The as-prepared INM actuators were tested in terms of surface resistance, platinum morphology, resonance frequency, tip displacement, current and blocked force, and their performances were compared to those of the widely used traditional Nafion actuator. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that much smaller and more uniform platinum particles were formed on the surfaces of the INM actuators as well as within their polymer matrix. Although excellent harmonic responses were observed for the newly developed INM actuators, they were found to be sensitive to the applied reduction times during the fabrication. The mechanical displacement of the INM actuator fabricated after the optimum reduction times was much larger than that of its Nafion counterpart of comparable thickness under the stimulus of constant and alternating current voltage. The PSMI-incorporated PVDF actuator can become a promising smart material to be used in the fields of biomimetic robots, biomedical devices, sensors and actuator, haptic interfaces, energy harvesting and so on.

Influence of polymer dielectrics on C60-based field-effect transistors

NASA Astrophysics Data System (ADS)

Zhou, Jianlin; Zhang, Fujia; Lan, Lifeng; Wen, Shangsheng; Peng, Junbiao

2007-12-01

Fullerene C60 organic field-effect transistors (OFETs) have been fabricated based on two different polymer dielectric materials, poly(methylmethacrylate) (PMMA) and cross-linkable poly(4-vinylphenol). The large grain size of C60 film and small number of traps at the interface of PMMA /C60 were obtained with high electron mobility of 0.66cm2/Vs in the PMMA transistor. The result suggests that the C60 semiconductor cooperating with polymer dielectric is a promising application in the fabrication of n-type organic transistors because of low threshold voltage and high electron mobility.

Functionalised graphene sheets as effective high dielectric constant fillers

PubMed Central

2011-01-01

A new functionalised graphene sheet (FGS) filled poly(dimethyl)siloxane insulator nanocomposite has been developed with high dielectric constant, making it well suited for applications in flexible electronics. The dielectric permittivity increased tenfold at 10 Hz and 2 wt.% FGS, while preserving low dielectric losses and good mechanical properties. The presence of functional groups on the graphene sheet surface improved the compatibility nanofiller/polymer at the interface, reducing the polarisation process. This study demonstrates that functionalised graphene sheets are ideal nanofillers for the development of new polymer composites with high dielectric constant values. PACS: 78.20.Ci, 72.80.Tm, 62.23.Kn PMID:21867505

Functionalised graphene sheets as effective high dielectric constant fillers

NASA Astrophysics Data System (ADS)

Romasanta, Laura J.; Hernández, Marianella; López-Manchado, Miguel A.; Verdejo, Raquel

2011-08-01

A new functionalised graphene sheet (FGS) filled poly(dimethyl)siloxane insulator nanocomposite has been developed with high dielectric constant, making it well suited for applications in flexible electronics. The dielectric permittivity increased tenfold at 10 Hz and 2 wt.% FGS, while preserving low dielectric losses and good mechanical properties. The presence of functional groups on the graphene sheet surface improved the compatibility nanofiller/polymer at the interface, reducing the polarisation process. This study demonstrates that functionalised graphene sheets are ideal nanofillers for the development of new polymer composites with high dielectric constant values. PACS: 78.20.Ci, 72.80.Tm, 62.23.Kn

Ionic conductivity and dielectric permittivity of polymer electrolyte plasticized with polyethylene glycol

NASA Astrophysics Data System (ADS)

Das, S.; Ghosh, A.

2016-05-01

We have studied ionic conductivity and dielectric permittivity of PEO-LiClO4 solid polymer electrolyte plasticized with polyethylene glycol (PEG). The temperature dependence of the ionic conductivity has been well interpreted using Vogel-Tamman-Fulcher equation. The maximum dielectric constant is observed for 30 wt. % of PEG content. To get further insights into the ion dynamics, the complex dielectric permittivity has been studied with Havriliak-Negami function. The variation of relaxation time with inverse temperature obtained from HN formalism follows VTF nature.

Significantly improved dielectric performances of nanocomposites via loading two-dimensional core-shell structure Bi2Te3@SiO2 nanosheets

NASA Astrophysics Data System (ADS)

Chen, Jianwen; Wang, Xiucai; Yu, Xinmei; Fan, Yun; Duan, Zhikui; Jiang, Yewen; Yang, Faquan; Zhou, Yuexia

2018-07-01

Polymer/semiconductor-insulator nanocomposites can display high dielectric constants with a relatively low dissipation factor under low electric fields, and thus seem to promising for high energy density capacitors. Here, a novel nanocomposite films is developed by loading two-dimensional (2D) core-shell structure Bi2Te3@SiO2 nanosheets in the poly (vinylidene fluoride-hexafluoro propylene) (P(VDF-HFP)) polymer matrix. The 2D Bi2Te3 nanosheets were prepared through simple microwave-assisted method. The experimental results suggesting that the SiO2 shell layer between the fillers and polymer matrix could effectively improve the dielectric constant, dielectric loss, AC conductivity, and breakdown strength of composites films. The composite films load with 10 vol.% 2D Bi2Te3@SiO2 nanosheets exhibits a high dielectric constant of 70.3 at 1 kHz and relatively low dielectric loss of 0.058 at 1 kHz. The finite element simulation of electric field and electric current density distribution revealed that the SiO2 shell layer between the fillers and polymer matrix could effectively improve the energy loss, local electric field strength, and breakdown strength of composite films. Therefore, this work will provide a promising route to achieve high-performance capacitors.

Measurement of complex terahertz dielectric properties of polymers using an improved free-space technique

NASA Astrophysics Data System (ADS)

Chang, Tianying; Zhang, Xiansheng; Yang, Chuanfa; Sun, Zhonglin; Cui, Hong-Liang

2017-04-01

The complex dielectric properties of non-polar solid polymer materials were measured in the terahertz (THz) band by a free-space technique employing a frequency-extended vector network analyzer (VNA), and by THz time-domain spectroscopy (TDS). Mindful of THz wave’s unique characteristics, the free-space method for measurement of material dielectric properties in the microwave band was expanded and improved for application in the THz frequency region. To ascertain the soundness and utility of the proposed method, measurements of the complex dielectric properties of a variety of polymers were carried out, including polytetrafluoroethylene (PTFE, known also by the brand name Teflon), polypropylene (PP), polyethylene (PE), and glass fiber resin (Composite Stone). The free-space method relies on the determination of electromagnetic scattering parameters (S-parameters) of the sample, with the gated-reflect-line (GRL) calibration technique commonly employed using a VNA. Subsequently, based on the S-parameters, the dielectric constant and loss characteristic of the sample were calculated by using a Newtonian iterative algorithm. To verify the calculated results, THz TDS technique, which produced Fresnel parameters such as reflection and transmission coefficients, was also used to independently determine the dielectric properties of these polymer samples, with results satisfactorily corroborating those obtained by the free-space extended microwave technique.

Biochemical synthesis of water soluble conducting polymers

NASA Astrophysics Data System (ADS)

Bruno, Ferdinando F.; Bernabei, Manuele

2016-05-01

An efficient biomimetic route for the synthesis of conducting polymers/copolymers complexed with lignin sulfonate and sodium (polystyrenesulfonate) (SPS) will be presented. This polyelectrolyte assisted PEG-hematin or horseradish peroxidase catalyzed polymerization of pyrrole (PYR), 3,4 ethyldioxithiophene (EDOT) and aniline has provided a route to synthesize water-soluble conducting polymers/copolymers under acidic conditions. The UV-vis, FTIR, conductivity and cyclic voltammetry studies for the polymers/copolymer complex indicated the presence of a thermally stable and electroactive polymers. Moreover, the use of water-soluble templates, used as well as dopants, provided a unique combination of properties such as high electronic conductivity, and processability. These polymers/copolymers are nowadays tested/evaluated for antirust features on airplanes and helicopters. However, other electronic applications, such as photovoltaics, for transparent conductive polyaniline, actuators, for polypyrrole, and antistatic films, for polyEDOT, will be proposed.

Adjustable Membrane Mirrors Incorporating G-Elastomers

NASA Technical Reports Server (NTRS)

Chang, Zensheu; Morgan, Rhonda M.; Xu, Tian-Bing; Su, Ji; Hishinuma, Yoshikazu; Yang, Eui-Hyeok

2008-01-01

Lightweight, flexible, large-aperture mirrors of a type being developed for use in outer space have unimorph structures that enable precise adjustment of their surface figures. A mirror of this type includes a reflective membrane layer bonded with an electrostrictive grafted elastomer (G-elastomer) layer, plus electrodes suitably positioned with respect to these layers. By virtue of the electrostrictive effect, an electric field applied to the G-elastomer membrane induces a strain along the membrane and thus causes a deflection of the mirror surface. Utilizing this effect, the mirror surface figure can be adjusted locally by individually addressing pairs of electrodes. G-elastomers, which were developed at NASA Langley Research Center, were chosen for this development in preference to other electroactive polymers partly because they offer superior electromechanical performance. Whereas other electroactive polymers offer, variously, large strains with low moduli of elasticity or small strains with high moduli of elasticity, G-elastomers offer both large strains (as large as 4 percent) and high moduli of elasticity (about 580 MPa). In addition, G-elastomer layers can be made by standard melt pressing or room-temperature solution casting.

Soft Robotic Actuators

NASA Astrophysics Data System (ADS)

Godfrey, Juleon Taylor

In this thesis a survey on soft robotic actuators is conducted. The actuators are classified into three main categories: Pneumatic Artificial Muscles (PAM), Electronic Electroactive Polymers (Electric EAP), and Ionic Electroactive Polymers (Ionic EAP). Soft robots can have many degrees and are more compliant than hard robots. This makes them suitable for applications that are difficult for hard robots. For each actuator background history, build materials, how they operate, and modeling are presented. Multiple actuators in each class are reviewed highlighting both their use and their mathematical formulation. In addition to the survey the McKibben actuator was chosen for fabrication and in-depth experimental analysis. Four McKibben actuators were fabricated using mesh sleeve, barbed hose fittings, and different elastic bladders. All were actuated using compressed air. Tensile tests were performed for each actuator to measure the tension force as air pressure increased from 20 to 100 psi in 10 psi increments. To account for material relaxation properties eleven trials for each actuator were run for 2-3 days. In conclusion, the smallest outer diameter elastic bladder was capable of producing the highest force due to the larger gap between the bladder and the sleeve.

True Low-Power Self-Locking Soft Actuators.

PubMed

Kim, Seung Jae; Kim, Onnuri; Park, Moon Jeong

2018-03-01

Natural double-layered structures observed in living organisms are known to exhibit asymmetric volume changes with environmental triggers. Typical examples are natural roots of plants, which show unique self-organized bending behavior in response to environmental stimuli. Herein, light- and electro-active polymer (LEAP) based actuators with a double-layered structure are reported. The LEAP actuators exhibit an improvement of 250% in displacement and hold an object three times heavier as compared to that in the case of conventional electro-active polymer actuators. Most interestingly, the bending motion of the LEAP actuators can be effectively locked for a few tens of minutes even in the absence of a power supply. Further, the self-locking LEAP actuators show a large and reversible bending strain of more than 2.0% and require only 6.2 mW h cm -2 of energy to hold an object for 15 min at an operating voltage of 3 V. These novel self-locking soft actuators should find wide applicability in artificial muscles, biomedical microdevices, and various innovative soft robot technologies. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Development of electroactive nanofibers based on thermoplastic polyurethane and poly(o-ethoxyaniline) for biological applications.

PubMed

Cruz, Karina Ferreira Noronha; Formaggio, Daniela Maria Ducatti; Tada, Dayane Batista; Cristovan, Fernando Henrique; Guerrini, Lilia Müller

2017-02-01

Electroactive nanofibers based on thermoplastic polyurethane (TPU) and poly(alkoxy anilines) produced by electrospinning has been explored for biomaterials applications. The thermoplastic polyurethane is a biocompatible polymer with good mechanical properties. The production of TPU nanofibers requires the application of high voltage during electrospinning in order to prepare uniform mats due to its weak ability to elongate during the process. To overcome this limitation, a conductive polymer can be incorporated to the process, allowing generates mats without defects. In this study, poly(o-ethoxyaniline) POEA doped with dodecylbenzene sulfonic acid (DBSA) was blended with thermoplastic polyurethane (TPU) by solution method. Films were produced by casting and nanofibers were prepared by electrospinning. The effect of the POEA on morphology, distribution of diameter and cell viability of the nanofibers was evaluated. The results demonstrated that the incorporation of POEA in TPU provided to the mats a suitable morphology for cellular growth. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 601-607, 2017. © 2016 Wiley Periodicals, Inc.

Artificial Muscles Based on Electroactive Polymers as an Enabling Tool in Biomimetics

NASA Technical Reports Server (NTRS)

Bar-Cohen, Y.

2007-01-01

Evolution has resolved many of nature's challenges leading to working and lasting solutions that employ principles of physics, chemistry, mechanical engineering, materials science, and many other fields of science and engineering. Nature's inventions have always inspired human achievements leading to effective materials, structures, tools, mechanisms, processes, algorithms, methods, systems, and many other benefits. Some of the technologies that have emerged include artificial intelligence, artificial vision, and artificial muscles, where the latter is the moniker for electroactive polymers (EAPs). To take advantage of these materials and make them practical actuators, efforts are made worldwide to develop capabilities that are critical to the field infrastructure. Researchers are developing analytical model and comprehensive understanding of EAP materials response mechanism as well as effective processing and characterization techniques. The field is still in its emerging state and robust materials are still not readily available; however, in recent years, significant progress has been made and commercial products have already started to appear. In the current paper, the state-of-the-art and challenges to artificial muscles as well as their potential application to biomimetic mechanisms and devices are described and discussed.

Effect of Bending Stiffness of the Electroactive Polymer Element on the Performance of a Hybrid Actuator System (HYBAS)

NASA Technical Reports Server (NTRS)

Xu, Tian-Bing; Su, Ji; Jiang, Xiaoning; Rehrig, Paul W.; Zhang, Shujun; Shrout, Thomas R.; Zhang, Qiming

2006-01-01

An electroactive polymer (EAP)-ceramic hybrid actuation system (HYBAS) was developed recently at NASA Langley Research Center. This paper focuses on the effect of the bending stiffness of the EAP component on the performance of a HYBAS, in which the actuation of the EAP element can match the theoretical prediction at various length/thickness ratios for a constant elastic modulus of the EAP component. The effects on the bending stiffness of the elastic modulus and length/thickness ratio of the EAP component were studied. A critical bending stiffness to keep the actuation of the EAP element suitable for a rigid beam theory-based modeling was found for electron irradiated P(VDF-TrFE) copolymer. For example, the agreement of experimental data and theoretical modeling for a HYBAS with the length/thickness ratio of EAP element at 375 times is demonstrated. However, the beam based theoretical modeling becomes invalid (i.e., the profile of the HYBAS movement does not follow the prediction of theoretical modeling) when the bending stiffness is lower than a critical value.

Preparation Process and Dielectric Properties of Ba(0.5)Sr(0.5)TiO3-P(VDF-CTFE) Nanocomposites

NASA Technical Reports Server (NTRS)

Zhang, Lin; Wu, Peixuang; Li, Yongtang; Cheng, Z. -Y.; Brewer, Jeffrey C.

2014-01-01

Ceramic-polymer 0-3 nanocomposites, in which nanosized Ba(0.5)Sr(0.5)TiO3 (BST) powders were used as ceramic filler and P(VDF-CTFE) 88/12 mol% [poly(vinylidene fluoridechlorotrifluoroethylene)] copolymer was used as matrix, were studied over a concentration range from 0 to 50 vol.% of BST powders. It is found that the solution cast composites are porous and a hot-press process can eliminate the porosity, which results in a dense composite film. Two different configurations used in the hot-press process are studied. Although there is no clear difference in the uniformity and microstructure of the composites prepared using these two configurations, the composite prepared using one configuration exhibit a higher dielectric constant with a lower loss. For the composite with 40 vol. BST, a dielectric constant of 70 with a loss of 0.07 at 1 kHz is obtained at room temperature. The composites exhibit a lower dielectric loss than the polymer matrix at high frequency. However, at low frequency, the composites exhibit a higher loss than the polymer matrix due to a low frequency relaxation process that appears in the composites. It is believed that this relaxation process is related to the interfacial layer formed between BST particle and the polymer matrix. The temperature dependence of the dielectric property of the composites was studied. It is found that the dielectric constant of these composites is almost independent of the temperature over a temperature range from 20 to 120 C. Key words: A. Polymer-matrix composites (PMCs); B. Electrical Properties; E. Casting; E. Heat treatment; Dielectric properties.

Improved flexoelectricity in PVDF/barium strontium titanate (BST) nanocomposites

NASA Astrophysics Data System (ADS)

Hu, Xinping; Zhou, Yang; Liu, Jie; Chu, Baojin

2018-04-01

The flexoelectric effect of polymers is normally much weaker than that of ferroelectric oxides. In order to improve the flexoelectric response of the poly(vinylidene fluoride) (PVDF) ferroelectric polymer, PVDF/Ba0.67Si0.33TiO3 (BST) nanocomposites were fabricated. BST nanofibers were prepared by the electrospinning method, and the fibers were further surface modified with H2O2 to achieve a stronger interfacial interaction between the fibers and polymer matrix. Due to the high dielectric properties and strong flexoelectric effect of the BST, both dielectric constant and flexoelectric response of the composite with 25 vol. % surface modified BST are 3-4 times higher than those of PVDF. The dependence of the dielectric constant and the flexoelectric coefficient on the composition of the nanocomposites can be fitted by the empirical Yamada model, and the dielectric constant and the flexoelectric coefficient are correlated by a linear relationship. This study provides an approach to enhance the flexoelectric response of PVDF-based polymers.

Ultra-broadband THz time-domain spectroscopy of common polymers using THz air photonics.

PubMed

D'Angelo, Francesco; Mics, Zoltán; Bonn, Mischa; Turchinovich, Dmitry

2014-05-19

Terahertz-range dielectric properties of the common polymers low-density polyethylene (LDPE), cyclic olefin/ethylene copolymer (TOPAS®), polyamide-6 (PA6), and polytetrafluoroethylene (PTFE or Teflon®) are characterized in the ultra-broadband frequency window 2-15 THz, using a THz time-domain spectrometer employing air-photonics for the generation and detection of single-cycle sub-50 fs THz transients. The time domain measurements provide direct access to both the absorption and refractive index spectra. The polymers LDPE and TOPAS® demonstrate negligible absorption and spectrally-flat refractive index across the entire spectroscopy window, revealing the high potential of these polymers for applications in THz photonics such as ultra-broadband polymer-based dielectric mirrors, waveguides, and fibers. Resonant high-frequency polar vibrational modes are observed and assigned in polymers PA6 and PTFE, and their dielectric functions in the complete frequency window 2-15 THz are theoretically reproduced. Our results demonstrate the potential of ultra-broadband air-photonics-based THz time domain spectroscopy as a valuable analytic tool for materials science.

Encapsulation of ionic electroactive polymers: reducing the interaction with environment

NASA Astrophysics Data System (ADS)

Jaakson, P.; Aabloo, A.; Tamm, T.

2016-04-01

Ionic electro-active polymer (iEAP) actuators are composite materials that change their mechanical properties in response to external electrical stimulus. The interest in these devices is mainly driven by their capability to generate biomimetic movements, and their potential use in soft robotics. The driving voltage of an iEAP-actuator (0.5… 3 V) is at least an order of magnitude lower than that needed for other types of electroactive polymers. To apply iEAP-actuators in potential real-world applications, the capability of operating in different environments (open air, different solvents) must be available. In their natural form, the iEAP-actuators are capable of interacting with the surrounding environment (evaporation of solvent from the electrolyte solution, ion or solvent exchange, humidity effects), therefore, for prevention of unpredictable behavior of the actuator and the contamination of the environment, encapsulation of the actuator is needed. The environmental contamination aspect of the encapsulation material is substantial when selecting an applicable encapsulant. The suitable encapsulant should form thin films, be light in weight, elastic, fit tightly, low cost, and easily reproducible. The main goal of the present study is to identify and evaluate the best potential encapsulation techniques for iEAPactuators. Various techniques like thin film on liquid coating, dip coating, hot pressing, hot rolling; and several materials like polydimethylsiloxane, polyurethane, nitrocellulose, paraffin-composite-films were investigated. The advantages and disadvantages of the combinations of the above mentioned techniques and materials are discussed. Successfully encapsulated iEAP-actuators gained durability and were stably operable for long periods of time under ambient conditions. The encapsulation process also increased the stability of the iEAP-actuator by minimizing the environment effects. This makes controlling iEAP-actuators more straight-forward and reliable since there is no need to take the environmental factors like relative humidity and/or gas circulation into account.

Conducting nanotubes or nanostructures based composites, method of making them and applications

NASA Technical Reports Server (NTRS)

Gupta, Mool C. (Inventor); Yang, Yonglai (Inventor); Dudley, Kenneth L. (Inventor); Lawrence, Roland W. (Inventor)

2013-01-01

An electromagnetic interference (EMI) shielding material includes a matrix of a dielectric or partially conducting polymer, such as foamed polystyrene, with carbon nanotubes or other nanostructures dispersed therein in sufficient concentration to make the material electrically conducting. The composite is formed by dispersing the nanotube material in a solvent in which the dielectric or partially conducting polymer is soluble and mixing the resulting suspension with the dielectric or partially conducting polymer. A foaming agent can be added to produce a lightweight foamed material. An organometallic compound can be added to enhance the conductivity further by decomposition into a metal phase.

Carbon nanotube network thin-film transistors on flexible/stretchable substrates

DOEpatents

Takei, Kuniharu; Takahashi, Toshitake; Javey, Ali

2016-03-29

This disclosure provides systems, methods, and apparatus for flexible thin-film transistors. In one aspect, a device includes a polymer substrate, a gate electrode disposed on the polymer substrate, a dielectric layer disposed on the gate electrode and on exposed portions of the polymer substrate, a carbon nanotube network disposed on the dielectric layer, and a source electrode and a drain electrode disposed on the carbon nanotube network.

Effect of Polymer Matrix on the Structure and Electric Properties of Piezoelectric Lead Zirconatetitanate/Polymer Composites

PubMed Central

Li, Rui; Zhou, Jun; Liu, Hujun; Pei, Jianzhong

2017-01-01

Piezoelectric lead zirconatetitanate (PZT)/polymer composites were prepared by two typical polymer matrixes using the hot-press method. The micromorphology, microstructure, dielectric properties, and piezoelectric properties of the PZT/polymer composites were characterized and investigated. The results showed that when the condition of frequency is 103 Hz, the dielectric and piezoelectric properties of PZT/poly(vinylidene fluoride) were both better than that of PZT/polyvinyl chloride (PVC). When the volume fraction of PZT was 50%, PZT/PVDF prepared by the hot-press method had better comprehensive electric property. PMID:28805730

Optimization of structural and dielectric properties of CdSe loaded poly(diallyl dimethyl ammonium chloride) polymer in a desired frequency and temperature window

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tyagi, Chetna, E-mail: ctyagi05@gmail.com; Sharma, Ambika, E-mail: ambikasharma2004@yahoo.com

2016-01-07

In the present paper, investigations of CdSe loaded poly(diallyl dimethyl ammonium chloride) (PDADMAC) nanocomposites and pure PDADMAC synthesized by wet chemical technique have been carried out. Fourier transform infrared and X-ray diffraction analysis have been performed to reveal the structural details of pure polymer and polymer nanocomposite (PNC). The dielectric behavior of pure polymer and PNC has been recorded, which results in higher value of the real and imaginary part of dielectric constant for PNC, as compared with pure PDADMAC. The increase is attributed to the addition of CdSe quantum dots to the pure polymer. The contribution of ionic andmore » electronic polarization has been observed at higher frequency. The theoretical fitting of Cole-Cole function to the experimental data of dielectric constant of PNC and pure PDADMAC results in the determination of relaxation time and conductivity of space charge carriers. The CdSe loaded polymer nanocomposite has been used as an electrolyte in the battery fabrication with configuration Al/PNC/Ag{sub 2}O. The ac conductivity measurements have been carried out for both samples in a frequency window of 1 kHz–5 MHz and at different temperatures varying from 298 K to 523 K. Activation energy (E{sub a}) has been determined for pure polymer as well as PNC and is found to be less for PNC, as compared with pure polymer. Further, impedance measurement at different temperatures results in two frequency ranges corresponding to ionic conduction and blocking electrode effect. The value of bulk resistance for pure polymer and PNC has been found to be 3660 Ω and 442 Ω, respectively, at 298 K temperature. Electric modulus has been determined and is observed to support the dielectric constant data; it further reveals the deviation from Debye behavior at a higher frequency.« less

Preparation of dielectric coating of variable dielectric constant by plasma polymerization

NASA Technical Reports Server (NTRS)

Hudis, M.; Wydeven, T. (Inventor)

1979-01-01

A plasma polymerization process for the deposition of a dielectric polymer coating on a substrate comprising disposing of the substrate in a closed reactor between two temperature controlled electrodes connected to a power supply is presented. A vacuum is maintained within the closed reactor, causing a monomer gas or gas mixture of a monomer and diluent to flow into the reactor, generating a plasma between the electrodes. The vacuum varies and controls the dielectric constant of the polymer coating being deposited by regulating the gas total and partial pressure, the electric field strength and frequency, and the current density.

A Multi-Objective Optimization Technique to Model the Pareto Front of Organic Dielectric Polymers

NASA Astrophysics Data System (ADS)

Gubernatis, J. E.; Mannodi-Kanakkithodi, A.; Ramprasad, R.; Pilania, G.; Lookman, T.

Multi-objective optimization is an area of decision making that is concerned with mathematical optimization problems involving more than one objective simultaneously. Here we describe two new Monte Carlo methods for this type of optimization in the context of their application to the problem of designing polymers with more desirable dielectric and optical properties. We present results of applying these Monte Carlo methods to a two-objective problem (maximizing the total static band dielectric constant and energy gap) and a three objective problem (maximizing the ionic and electronic contributions to the static band dielectric constant and energy gap) of a 6-block organic polymer. Our objective functions were constructed from high throughput DFT calculations of 4-block polymers, following the method of Sharma et al., Nature Communications 5, 4845 (2014) and Mannodi-Kanakkithodi et al., Scientific Reports, submitted. Our high throughput and Monte Carlo methods of analysis extend to general N-block organic polymers. This work was supported in part by the LDRD DR program of the Los Alamos National Laboratory and in part by a Multidisciplinary University Research Initiative (MURI) Grant from the Office of Naval Research.

An electroactive conducting polymer actuator based on NBR/RTIL solid polymer electrolyte

NASA Astrophysics Data System (ADS)

Cho, M. S.; Seo, H. J.; Nam, J. D.; Choi, H. R.; Koo, J. C.; Lee, Y.

2007-04-01

This paper reports the fabrication of a dry-type conducting polymer actuator using nitrile rubber (NBR) as the base material in a solid polymer electrolyte. The conducting polymer, poly(3,4-ethylenedioxythiophene) (PEDOT), was synthesized on the surface of the NBR layer by using a chemical oxidation polymerization technique. Room-temperature ionic liquids (RTIL) based on imidazolium salts, e.g. 1-butyl-3-methyl imidazolium X (where X = BF4-, PF6-, (CF3SO2)2N-), were absorbed into the composite film. The compatibility between the ionic liquids and the NBR polymer was confirmed by DMA. The effect of the anion size of the ionic liquids on the displacement of the actuator was examined. The displacement increased with increasing anion size of the ionic liquids. The cyclic voltammetry responses and the redox switching dynamics of the actuators were examined in different ionic liquids.

Biochemical synthesis of water soluble conducting polymers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bruno, Ferdinando F., E-mail: Ferdinando-Bruno@uml.edu; Bernabei, Manuele

2016-05-18

An efficient biomimetic route for the synthesis of conducting polymers/copolymers complexed with lignin sulfonate and sodium (polystyrenesulfonate) (SPS) will be presented. This polyelectrolyte assisted PEG-hematin or horseradish peroxidase catalyzed polymerization of pyrrole (PYR), 3,4 ethyldioxithiophene (EDOT) and aniline has provided a route to synthesize water-soluble conducting polymers/copolymers under acidic conditions. The UV-vis, FTIR, conductivity and cyclic voltammetry studies for the polymers/copolymer complex indicated the presence of a thermally stable and electroactive polymers. Moreover, the use of water-soluble templates, used as well as dopants, provided a unique combination of properties such as high electronic conductivity, and processability. These polymers/copolymers are nowadaysmore » tested/evaluated for antirust features on airplanes and helicopters. However, other electronic applications, such as photovoltaics, for transparent conductive polyaniline, actuators, for polypyrrole, and antistatic films, for polyEDOT, will be proposed.« less

Synthesis and Characterization of SF-PPV-I

NASA Technical Reports Server (NTRS)

Wang, Y.; Fan, Z.; Taft, C.; Sun, S.

2001-01-01

Conjugated electro-active polymers find their potential applications in developing variety inexpensive and flexible shaped electronic and photonic devices, such as photovoltaic or photo/electro light emitting devices. In many of these opto-electronic polymeric materials, certain electron rich donors and electron deficient acceptors are needed in order to fine-tune the electronic or photonic properties of the desired materials and structures. While many donor type of conjugated polymers have been widely studied and developed in the past decades, there are relatively fewer acceptor type of conjugated polymers have been developed. Key acceptor type conjugated polymers developed so far include C60 and CN-PPV, and each has its limitations. Due to the complexity and diversity of variety future electronic materials and structural needs, alternative and synthetically amenable acceptor conjugated polymers need to be developed. In this paper, we present the synthesis and characterization of a new acceptor conjugated polymer, a sulfone derivatized polyphenylenevinylene "SF-PPV".

Double network bacterial cellulose hydrogel to build a biology-device interface.

PubMed

Shi, Zhijun; Li, Ying; Chen, Xiuli; Han, Hongwei; Yang, Guang

2014-01-21

Establishing a biology-device interface might enable the interaction between microelectronics and biotechnology. In this study, electroactive hydrogels have been produced using bacterial cellulose (BC) and conducting polymer (CP) deposited on the BC hydrogel surface to cover the BC fibers. The structures of these composites thus have double networks, one of which is a layer of electroactive hydrogels combined with BC and CP. The electroconductivity provides the composites with capabilities for voltage and current response, and the BC hydrogel layer provides good biocompatibility, biodegradability, bioadhesion and mass transport properties. Such a system might allow selective biological functions such as molecular recognition and specific catalysis and also for probing the detailed genetic and molecular mechanisms of life. A BC-CP composite hydrogel could then lead to a biology-device interface. Cyclic voltammetry and electrochemical impedance spectroscopy (EIS) are used here to study the composite hydrogels' electroactive property. BC-PAni and BC-PPy respond to voltage changes. This provides a mechanism to amplify electrochemical signals for analysis or detection. BC hydrogels were found to be able to support the growth, spreading and migration of human normal skin fibroblasts without causing any cytotoxic effect on the cells in the cell culture. These double network BC-CP hydrogels are biphasic Janus hydrogels which integrate electroactivity with biocompatibility, and might provide a biology-device interface to produce implantable devices for personalized and regenerative medicine.

Double network bacterial cellulose hydrogel to build a biology-device interface

NASA Astrophysics Data System (ADS)

Shi, Zhijun; Li, Ying; Chen, Xiuli; Han, Hongwei; Yang, Guang

2013-12-01

Establishing a biology-device interface might enable the interaction between microelectronics and biotechnology. In this study, electroactive hydrogels have been produced using bacterial cellulose (BC) and conducting polymer (CP) deposited on the BC hydrogel surface to cover the BC fibers. The structures of these composites thus have double networks, one of which is a layer of electroactive hydrogels combined with BC and CP. The electroconductivity provides the composites with capabilities for voltage and current response, and the BC hydrogel layer provides good biocompatibility, biodegradability, bioadhesion and mass transport properties. Such a system might allow selective biological functions such as molecular recognition and specific catalysis and also for probing the detailed genetic and molecular mechanisms of life. A BC-CP composite hydrogel could then lead to a biology-device interface. Cyclic voltammetry and electrochemical impedance spectroscopy (EIS) are used here to study the composite hydrogels' electroactive property. BC-PAni and BC-PPy respond to voltage changes. This provides a mechanism to amplify electrochemical signals for analysis or detection. BC hydrogels were found to be able to support the growth, spreading and migration of human normal skin fibroblasts without causing any cytotoxic effect on the cells in the cell culture. These double network BC-CP hydrogels are biphasic Janus hydrogels which integrate electroactivity with biocompatibility, and might provide a biology-device interface to produce implantable devices for personalized and regenerative medicine.

Low Dielectric Polymers

NASA Technical Reports Server (NTRS)

Venumbaka, Sreenivasulu R.; Cassidy, Patrick E.

2002-01-01

This report summarizes results obtained from research funded through Research Cooperative Agreement No. NCC-1-01033-"Low Dielectric Polymers" (from 5/10/01 through 5/09/02). Results are reported in three of the proposed research areas (Tasks 1-3 in the original proposal): (1) Repeat and confirm the preparation and properties of the new alkyl-substituted PEK, 6HC17-PEK, (2) Prepare and evaluate polymers derived from a highly fluorinated monomer, and (3) Prepare and evaluate new silicon and/or fluorine-containing polymers expected to retain useful properties at low temperature.

Towards a physics-based multiscale modelling of the electro-mechanical coupling in electro-active polymers.

PubMed

Cohen, Noy; Menzel, Andreas; deBotton, Gal

2016-02-01

Owing to the increasing number of industrial applications of electro-active polymers (EAPs), there is a growing need for electromechanical models which accurately capture their behaviour. To this end, we compare the predicted behaviour of EAPs undergoing homogeneous deformations according to three electromechanical models. The first model is a phenomenological continuum-based model composed of the mechanical Gent model and a linear relationship between the electric field and the polarization. The electrical and the mechanical responses according to the second model are based on the physical structure of the polymer chain network. The third model incorporates a neo-Hookean mechanical response and a physically motivated microstructurally based long-chains model for the electrical behaviour. In the microstructural-motivated models, the integration from the microscopic to the macroscopic levels is accomplished by the micro-sphere technique. Four types of homogeneous boundary conditions are considered and the behaviours determined according to the three models are compared. For the microstructurally motivated models, these analyses are performed and compared with the widely used phenomenological model for the first time. Some of the aspects revealed in this investigation, such as the dependence of the intensity of the polarization field on the deformation, highlight the need for an in-depth investigation of the relationships between the structure and the behaviours of the EAPs at the microscopic level and their overall macroscopic response.

Dielectric studies on PVA/PVP blend polymer electrolyte films

NASA Astrophysics Data System (ADS)

Kumar, B. Ranjit; Basha, S. K. Shahenoor; Rao, M. C.

2018-05-01

Biodegradable blend polymer electrolytes of PVA/PVP with different wt% ratios of MgCl2.6H2O have been prepared using solution cast technique. Dielectric studies were performed on to the prepared films using HIOKI 3532-50 in the frequency range 5000 Hz - 50000 KHz. As increasing the frequency the dielectric constant gradually decreases and found to be high for the sample prepared at 30 wt%; this concludes that the drifting of ions is high giving raise to conductivity phenomenon.

A thin membrane artificial muscle rotary motor

NASA Astrophysics Data System (ADS)

Anderson, Iain A.; Hale, Thom; Gisby, Todd; Inamura, Tokushu; McKay, Thomas; O'Brien, Benjamin; Walbran, Scott; Calius, Emilio P.

2010-01-01

Desirable rotary motor attributes for robotics include the ability to develop high torque in a low mass body and to generate peak power at low rotational speeds. Electro-active polymer artificial muscles offer promise as actuator elements for robotic motors. A promising artificial muscle technology for use as a driving mechanism for rotary motion is the dielectric elastomer actuator (DEA). We present a membrane DEA motor in which phased actuation of electroded sectors of the motor membrane impart orbital motion to a central drive that turns a rotor. The motor is inherently scalable, flexible, flat, silent in operation, amenable to deposition-based manufacturing approaches, and uses relatively inexpensive materials. As a membrane it can also form part of the skin of a robot. We have investigated the torque and power of stacked membrane layers. Specific power and torque ratios when calculated using active membrane mass only were 20.8 W/kg and 4.1 Nm/kg, respectively. These numbers compare favorably with a commercially available stepper motor. Multi-membrane fabrication substantially boosts torque and power and increases the active mass of membrane relative to supporting framework. Through finite element modeling, we show the mechanisms governing the maximum torque the device can generate and how the motor can be improved.

Polyethers containing 4-(carbazol-2-yl)-7-arylbenzo[c]-1,2,5-thiadiazole chromophores as solution processed materials for hole transporting layers of OLEDs

NASA Astrophysics Data System (ADS)

Krucaite, G.; Tavgeniene, D.; Xie, Z.; Lin, X.; Zhang, B.; Grigalevicius, S.

2018-02-01

Two polyethers containing electroactive pendent 4-(carbazol-2-yl)-7-arylbenzo[c]-1,2,5-thiadiazole moieties have been synthesized by the multi-step synthetic route. Full characterization of their structures is presented. The polymers represent derivatives of very high thermal stability with initial thermal degradation temperatures of 425 °C and 431 °C. Glass transition temperatures of the amorphous materials were also very high and reached values of 154 °C and 163 °C. The electron photoemission spectra of thin layers of the polymers showed ionization potentials of 5.84 eV and 5.93 eV. Hole-transporting properties of the polymeric materials were tested in the structures of organic light emitting diodes with Alq3 as the green emitter and electron transporting material. An electroluminescent device containing hole-transporting layer (HTL) of the polymer with electroactive 4-carbazolyl-7-phenylbenzo[c]-1,2,5-thiadiazole moieties exhibited turn on voltage of 6.2 V, maximum photometric efficiency of 2.5 cd/A and maximum brightness exceeding 300 cd/m2. The device containing HTL of the polymer with 4-carbazolyl-7-(1-naphtyl)benzo[c]-1,2,5-thiadiazole moieties demonstrated turn on voltage of 5.2 V, maximum photometric efficiency of 1.6 cd/A and maximum brightness exceeding 1500 cd/m2. The efficiencies were about 30-90% higher than that of the device containing widely used hole transporting layers of poly(9-vinylcarbazole).

Anisotropic Dielectric Properties of Carbon Fiber Reinforced Polymer Composites during Microwave Curing

NASA Astrophysics Data System (ADS)

Zhang, Linglin; Li, Yingguang; Zhou, Jing

2018-01-01

Microwave cuing technology is a promising alternative to conventional autoclave curing technology in high efficient and energy saving processing of polymer composites. Dielectric properties of composites are key parameters related to the energy conversion efficiency during the microwave curing process. However, existing methods of dielectric measurement cannot be applied to the microwave curing process. This paper presented an offline test method to solve this problem. Firstly, a kinetics model of the polymer composites under microwave curing was established based on differential scanning calorimetry to describe the whole curing process. Then several specially designed samples of different feature cure degrees were prepared and used to reflect the dielectric properties of the composite during microwave curing. It was demonstrated to be a feasible plan for both test accuracy and efficiency through extensive experimental research. Based on this method, the anisotropic complex permittivity of a carbon fiber/epoxy composite during microwave curing was accurately determined. Statistical results indicated that both the dielectric constant and dielectric loss of the composite increased at the initial curing stage, peaked at the maximum reaction rate point and decreased finally during the microwave curing process. Corresponding mechanism has also been systematically investigated in this work.

Reconfigurable Optical Elements Based on Single and Coupled Microdisk Resonators with Quantum DOT Active Media

DTIC Science & Technology

2012-06-29

of active-passive integrated polymer waveguides. The active waveguides consist of CdSe quantum dots dispersed in SU8 . Bottom panel shows CCD images...successfully demonstrated (i) incorporation of CdSe QDs into polymer and dielectric host and realization of devices such as active waveguides, microdisk...the significant outcomes of the program: • Successful incorporation of CdSe QDs into polymer and dielectric host and realization of devices such as

Decorating TiO2 Nanowires with BaTiO3 Nanoparticles: A New Approach Leading to Substantially Enhanced Energy Storage Capability of High-k Polymer Nanocomposites.

PubMed

Kang, Da; Wang, Guanyao; Huang, Yanhui; Jiang, Pingkai; Huang, Xingyi

2018-01-31

The urgent demand of high energy density and high power density devices has triggered significant interest in high dielectric constant (high-k) flexible nanocomposites comprising dielectric polymer and high-k inorganic nanofiller. However, the large electrical mismatch between polymer and nanofiller usually leads to earlier electric failure of the nanocomposites, resulting in an undesirable decrease of electrical energy storage capability. A few studies show that the introduction of moderate-k shell onto a high-k nanofiller surface can decrease the dielectric constant mismatch, and thus, the corresponding nanocomposites can withstand high electric field. Unfortunately, the low apparent dielectric enhancement of the nanocomposites and high electrical conductivity mismatch between matrix and nanofiller still result in low energy density and low efficiency. In this study, it is demonstrated that encapsulating moderate-k nanofiller with high-k but low electrical conductivity shell is effective to significantly enhance the energy storage capability of dielectric polymer nanocomposites. Specifically, using BaTiO 3 nanoparticles encapsulated TiO 2 (BaTiO 3 @TiO 2 ) core-shell nanowires as filler, the corresponding poly(vinylidene fluoride-co-hexafluoropylene) nanocomposites exhibit superior energy storage capability in comparison with the nanocomposites filled by either BaTiO 3 or TiO 2 nanowires. The nanocomposite film with 5 wt % BaTiO 3 @TiO 2 nanowires possesses an ultrahigh discharged energy density of 9.95 J cm -3 at 500 MV m -1 , much higher than that of commercial biaxial-oriented polypropylene (BOPP) (3.56 J cm -3 at 600 MV m -1 ). This new strategy and corresponding results presented here provide new insights into the design of dielectric polymer nanocomposites with high electrical energy storage capability.

Direct Fabrication of Inkjet-Printed Dielectric Film for Metal-Insulator-Metal Capacitors

NASA Astrophysics Data System (ADS)

Cho, Cheng-Lin; Kao, Hsuan-ling; Wu, Yung-Hsien; Chang, Li-Chun; Cheng, Chun-Hu

2018-01-01

In this study, an inkjet-printed dielectric film that used a polymer-based SU-8 ink was fabricated for use in a metal-insulator-metal (MIM) capacitor. Thermal treatment of the inkjet-printed SU-8 polymer film affected its surface morphology, chemical structure, and surface wettability. A 20-min soft-bake at 60°C was applied to eliminate inkjet-printed bubbles and ripples. The ultraviolet-exposed SU-8 polymer film was crosslinked at temperatures between 120°C and 220°C and became disordered at 270°C, demonstrated using Fourier-transform infrared spectroscopy. A maximum SU-8 polymer film hard-bake temperature of 120°C was identified, and a printing process was subsequently employed because the appropriate water contact angle of the printed film was 79°. Under the appropriate inkjet printing conditions, the two-transmission-line method was used to extract the dielectric and electrical properties of the SU-8 polymer film, and the electrical behavior of the fabricated MIM capacitor was also characterized.

Cast dielectric composite linear accelerator

DOEpatents

Sanders, David M [Livermore, CA; Sampayan, Stephen [Manteca, CA; Slenes, Kirk [Albuquerque, NM; Stoller, H M [Albuquerque, NM

2009-11-10

A linear accelerator having cast dielectric composite layers integrally formed with conductor electrodes in a solventless fabrication process, with the cast dielectric composite preferably having a nanoparticle filler in an organic polymer such as a thermosetting resin. By incorporating this cast dielectric composite the dielectric constant of critical insulating layers of the transmission lines of the accelerator are increased while simultaneously maintaining high dielectric strengths for the accelerator.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feng, Yefeng; Gong, Honghong; Xie, Yunchuan

Interface polarization and interface zone have been widely utilized to account for the abnormally improved dielectric properties of composites although their formation is rather vague and their influence has never been directly measured. In this work, micro α-SiC was designed as the filler particles incorporated into poly(vinylidenefluoride-co-chlorotrifluoroethylene) with internal double bonds (P(VDF-CTFE-DB)) to construct polymer micro composites through solution casting method. The dielectric constant of the composites is found to be increasing linearly as SiC content increases at lower content and the highest value is obtained as 83 at 100 Hz, which is unusually higher than both pristine polymer (13@100 Hz) andmore » SiC filler (17@100 Hz). By studying the dielectric properties of a bilayer model composite, the real dielectric permittivity of SiC sheet and P(VDF-CTFE-DB) layer has been directly measured to be significantly enhanced than their original value. The induced polarity between high polar PVDF units in polymer matrix and the electron-hole dipoles in α-SiC is responsible for the elevated dielectric properties of both components, which could address the failure of binary series and parallel models in predicting the dielectric permittivity of 0-3 composites as well. The strong dependence of induced polarity on the volume content, thickness, and polar nature of both components strongly suggests establishing promising high induced polarity between polymer matrix and fillers may provide an alternative strategy for fabricating high-k composites.« less

Self-Healing Polymer Dielectric for a High Capacitance Gate Insulator.

PubMed

Ko, Jieun; Kim, Young-Jae; Kim, Youn Sang

2016-09-14

Self-healing materials are required for development of various flexible electronic devices to repair cracks and ruptures caused by repetitive bending or folding. Specifically, a self-healing dielectric layer has huge potential to achieve healing electronics without mechanical breakdown in flexible operations. Here, we developed a high performance self-healing dielectric layer with an ionic liquid and catechol-functionalized polymer which exhibited a self-healing ability for both bulk and film states under mild self-healing conditions at 55 °C for 30 min. Due to the sufficient ion mobility of the ionic liquid in the polymer matrix, it had a high capacitance value above 1 μF/cm(2) at 20 Hz. Moreover, zinc oxide (ZnO) thin-film transistors (TFTs) with a self-healing dielectric layer exhibited a high field-effect mobility of 16.1 ± 3.07 cm(2) V(-1) s(-1) at a gate bias of 3 V. Even after repetitive self-healing of the dielectric layer from mechanical breaking, the electrical performance of the TFTs was well-maintained.

Magnetic nanofiber composite materials and devices using same

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Xing; Zhou, Ziyao

2017-04-11

A nonreciprocal device is described. It includes a housing, a waveguide layer and at least one layer of magnetic nanofiber composite. The magnetic nanofiber composite layer is made up of a polymer base layer, a dielectric matrix comprising magnetic nanofibers. The nanofibers have a high aspect ratio and wherein said dielectric matrix is embedded in the polymer base layer.

Electrical and dielectric properties of PVdF-HFP - PMMA - (PC + DEC)- LiClO4 based gel polymer electrolyte

NASA Astrophysics Data System (ADS)

Gohel, Khushbu; Kanchan, D. K.; Maheshwaran, C.

2018-04-01

In the present paper, AC impedance studies have been measured to evaluate ion conduction behavior of (PVdF-HFP - PMMA) + (PC-DEC) + LiClO4 gel polymer electrolyte system prepared by solution casting method. Structural characterization and morphology has been carried out using XRD and SEM respectively. The AC conductivity and dielectric permittivity, electric modulus and relaxation mechanism have been studied. The variation of ac conductivity with frequency obeys Jonscher power law. Maximum value of dielectric constant ɛ' in the lower frequency region has been observed for the gel polymer electrolyte containing 7.5 wt% LiClO4. The highest conducting sample shows the shortest relaxation time.

Non-Traditional Aromatic Topologies and Biomimetic Assembly Motifs as Components of Functional Pi-Conjugated Oligomers

PubMed Central

Tovar, John D.; Diegelmann, Stephen R.; Peart, Patricia A.

2010-01-01

This article will highlight our recent work using conjugated oligomers as precursors to electroactive polymer films and self-assembling nanomaterials. One area of investigation has focused on nonbenzenoid aromaticity in the context of charge delocalization in conjugated polymers. In these studies, polymerizable pi-conjugated units were coupled onto unusual aromatic cores such as methano[10]annulene. This article will also show how biologically-inspired assembly of molecularly well-defined oligopeptides that flank pi-conjugated oligomers has resulted in the aqueous construction of 1-dimensional nanomaterials that encourage electronic delocalization among the pi-electron systems.

Effect of Polymer Gate Dielectrics on Charge Transport in Carbon Nanotube Network Transistors: Low-k Insulator for Favorable Active Interface.

PubMed

Lee, Seung-Hoon; Xu, Yong; Khim, Dongyoon; Park, Won-Tae; Kim, Dong-Yu; Noh, Yong-Young

2016-11-30

Charge transport in carbon nanotube network transistors strongly depends on the properties of the gate dielectric that is in direct contact with the semiconducting carbon nanotubes. In this work, we investigate the dielectric effects on charge transport in polymer-sorted semiconducting single-walled carbon nanotube field-effect transistors (s-SWNT-FETs) by using three different polymer insulators: A low-permittivity (ε r ) fluoropolymer (CYTOP, ε r = 1.8), poly(methyl methacrylate) (PMMA, ε r = 3.3), and a high-ε r ferroelectric relaxor [P(VDF-TrFE-CTFE), ε r = 14.2]. The s-SWNT-FETs with polymer dielectrics show typical ambipolar charge transport with high ON/OFF ratios (up to ∼10 5 ) and mobilities (hole mobility up to 6.77 cm 2 V -1 s -1 for CYTOP). The s-SWNT-FET with the lowest-k dielectric, CYTOP, exhibits the highest mobility owing to formation of a favorable interface for charge transport, which is confirmed by the lowest activation energies, evaluated by the fluctuation-induced tunneling model (FIT) and the traditional Arrhenius model (E aFIT = 60.2 meV and E aArr = 10 meV). The operational stability of the devices showed a good agreement with the activation energies trend (drain current decay ∼14%, threshold voltage shift ∼0.26 V in p-type regime of CYTOP devices). The poor performance in high-ε r devices is accounted for by a large energetic disorder caused by the randomly oriented dipoles in high-k dielectrics. In conclusion, the low-k dielectric forms a favorable interface with s-SWNTs for efficient charge transport in s-SWNT-FETs.

Dielectric characterization of CuxS-NiySz/FNBR and CuS-NiySz/FNBR nanocomposites

NASA Astrophysics Data System (ADS)

Balayeva, Ofeliya O.; Azizov, Abdulsaid A.; Muradov, Mustafa B.; Eyvazova, Goncha M.

2017-06-01

CuxS-NiySz/FNBR and CuS-NiySz/FNBR nanocomposites (NCs) were prepared from β-NiS/FNBR by ion exchange method and dielectric characterized. Dielectric properties of NCs were investigated at the temperature of 26 °C-120 °C in 120-106 Hz frequency range. With measuring electric capacity and resistance of the samples at different frequency we have studied the dielectric permittivity, dielectric loss tangent, dielectric modulus, conductivity, relaxation times and Cole-Cole plots were obtained. At 120 °C measurement temperature, some of the destruction processes in polymers affect to interfacial interaction between the polymer and particles surface. After high temperature measurement all three samples were cooled to room temperature and their dielectric measurements were carried out at room temperature. It is observed that at high measurement temperature some of carriers transfer from one energy level to another and the dipole orientation did not return completely to the previous situation.

Electron beam irradiated polymer electrolyte film: Morphology, dielectric and AC conductivity studies

NASA Astrophysics Data System (ADS)

Yesappa, L.; Niranjana, M.; Ashokkumar, S. P.; Vijeth, H.; Ganesh, S.; Devendrappa, H.

2018-05-01

The polymer (PVdF-co-HFP: LiClO4=90:10, PHL10) electrolyte films prepared by solution casting method and studied morphology, dielectric properties and ac conductivity before and after electron beam (EB) irradiation. The polarized optical micrographs reveals size of spherulite reduced with increasing EB dose represents increase in amorphousity. The dielectric measurements were studied at different temperatures and observed increase with frequency at different temperatures upon EB irradiation. The ac conductivity increases with frequency due to effect of EB dose.

Charging and breakdown in amorphous dielectrics: Phenomenological modeling approach and applications

NASA Astrophysics Data System (ADS)

Palit, Sambit

Amorphous dielectrics of different thicknesses (nm to mm) are used in various applications. Low temperature processing/deposition of amorphous thin-film dielectrics often result in defect-states or electronic traps. These traps are responsible for increased leakage currents and bulk charge trapping in many associated applications. Additional defects may be generated during regular usage, leading to electrical breakdown. Increased leakage currents, charge trapping and defect generation/breakdown are important and pervasive reliability concerns in amorphous dielectrics. We first explore the issue of charge accumulation and leakage in amorphous dielectrics. Historically, charge transport in amorphous dielectrics has been presumed, depending on the dielectric thickness, to be either bulk dominated (Frenkel-Poole (FP) emission) or contact dominated (Fowler-Nordheim tunneling). We develop a comprehensive dielectric charging modeling framework which solves for the transient and steady state charge accumulation and leakage currents in an amorphous dielectric, and show that for intermediate thickness dielectrics, the conventional assumption of FP dominated current transport is incorrect, and may lead to false extraction of dielectric parameters. We propose an improved dielectric characterization methodology based on an analytical approximation of our model. Coupled with ab-initio computed defect levels, the dielectric charging model explains measured leakage currents more accurately with lesser empiricism. We study RF-MEMS capacitive switches as one of the target applications of intermediate thickness amorphous dielectrics. To achieve faster analysis and design of RF-MEMS switches in particular, and electro-mechanical actuators in general, we propose a set of fundamental scaling relationships which are independent of specific physical dimensions and material properties; the scaling relationships provide an intrinsic classification of all electro-mechanical actuators. However, RF-MEMS capacitive switches are plagued by the reliability issue of temporal shifts of actuation voltages due to dielectric charge accumulation, often resulting in failure due to membrane stiction. Using the dielectric charging model, we show that in spite of unpredictable roughness of deposited dielectrics, there are predictable shifts in actuation voltages due to dielectric charging in RF-MEMS switches. We also propose a novel non-obtrusive, non-contact, fully electronic resonance based technique to characterize charging driven actuation shifts in RF-MEMS switches which overcomes limitations in conventionally used methods. Finally, we look into the issue of defect generation and breakdown in thick polymer dielectrics. Polymer materials often face premature electrical breakdown due to high electric fields and frequencies, and exposure to ambient humidity conditions. Using a field-driven correlated defect generation model, coupled with a model for temperature rise due to dielectric heating at AC stresses, we explain measured trends in time-to-breakdown and breakdown electric fields in polymer materials. Using dielectric heating we are able to explain the observed lifetime and dielectric strength reduction with increasing dielectric thicknesses. Performing lifetime measurements after exposure to controlled humidity conditions, we find that moisture ingress into a polymer material reduces activation barriers for chain breakage and increases dielectric heating. Overall, this thesis develops a comprehensive framework of dielectric charging, leakage and degradation of insulators of different thicknesses that have broad applications in multiple technologies.

Characterization of the electromechanical properties of EAP materials

NASA Technical Reports Server (NTRS)

Bar-Cohen, Yoseph; Sherrita, Stewart; Bhattachary, Kaushik; Lih, Shyh-Shiuh

2001-01-01

Electroactive polymers (EAP) are an emerging class of actuation materials. Their large electrically induced strains (longitudinal or bending), low density, mechanical flexibility, and ease of processing offer advantages over traditional electroactive materials. However, before the capability of these materials can be exploited, their electrical and mechanical behavior must be properly quantified. Two general types of EAP can be identified. The first type is ionic EAP, which requires relatively low voltages (<10V) to achieve large bending deflections. This class usually needs to be hydrated and electrochemical reactions may occur. The second type is Electronic-EAP and it involves electrostrictive and/or Maxwell stresses. This type of materials requires large electric fields (>100MV/m) to achieve longitudinal deformations at the range from 4 - 360%. Some of the difficulties in characterizing EAP include: nonlinear properties, large compliance (large mismatch with metal electrodes), nonhomogeneity resulting from processing, etc. To support the need for reliable data, the authors are developing characterization techniques to quantify the electroactive responses and material properties of EAP materials. The emphasis of the current study is on addressing electromechanical issues related to the ion-exchange type EAP also known as IPMC. The analysis, experiments and test results are discussed in this paper.

Thermal stress in flexible interdigital transducers with anisotropic electroactive cellulose substrates

NASA Astrophysics Data System (ADS)

Yoon, Sean J.; Kim, Jung Woong; Kim, Hyun Chan; Kang, Jinmo; Kim, Jaehwan

2017-12-01

Thermal stress in flexible interdigital transducers a reliability concern in the development of flexible devices, which may lead to interface delamination, stress voiding and plastic deformation. In this paper, a mathematical model is presented to investigate the effect of material selections on the thermal stress in interdigital transducers. We modified the linear relationships in the composite materials theory with the effect of high curvature, anisotropic substrate and small substrate thickness. We evaluated the thermal stresses of interdigital transducers, fabricated with various electrodes, insulators and substrate materials for the comparison. The results show that, among various insulators, organic polymer developed the highest stress level while oxide showed the lowest stress level. Aluminium shows a higher stress level and curvature as an electrode than gold. As substrate materials, polyimide and electroactive cellulose show similar stress levels except the opposite sign convention to each other. Polyimide shows positive curvatures while electroactive cellulose shows negative curvatures, which is attributed to the stress and thermal expansion state of the metal/insulator composite. The results show that the insulator is found to be responsible for the confinement across the metal lines while the substrate is responsible for the confinement along the metal lines.

Pursuing Polymer Dielectric Interfacial Effect in Organic Transistors for Photosensing Performance Optimization.

PubMed

Wu, Xiaohan; Chu, Yingli; Liu, Rui; Katz, Howard E; Huang, Jia

2017-12-01

Polymer dielectrics in organic field-effect transistors (OFETs) are essential to provide the devices with overall flexibility, stretchability, and printability and simultaneously introduce charge interaction on the interface with organic semiconductors (OSCs). The interfacial effect between various polymer dielectrics and OSCs significantly and intricately influences device performance. However, understanding of this effect is limited because the interface is buried and the interfacial charge interaction is difficult to stimulate and characterize. Here, this challenge is overcome by utilizing illumination to stimulate the interfacial effect in various OFETs and to characterize the responses of the effect by measuring photoinduced changes of the OFETs performances. This systemic investigation reveals the mechanism of the intricate interfacial effect in detail, and mathematically explains how the photosensitive OFETs characteristics are determined by parameters including polar group of the polymer dielectric and the OSC side chain. By utilizing this mechanism, performance of organic electronics can be precisely controlled and optimized. OFETs with strong interfacial effect can also show a signal additivity caused by repeated light pulses, which is applicable for photostimulated synapse emulator. Therefore, this work enlightens a detailed understanding on the interface effect and provides novel strategies for optimizing OFET photosensory performances.

Development of advanced polymer nanocomposite capacitors

NASA Astrophysics Data System (ADS)

Mendoza, Miguel

The current development of modern electronics has driven the need for new series of energy storage devices with higher energy density and faster charge/discharge rate. Batteries and capacitors are two of the most widely used energy storage devices. Compared with batteries, capacitors have higher power density and significant higher charge/discharge rate. Therefore, high energy density capacitors play a significant role in modern electronic devices, power applications, space flight technologies, hybrid electric vehicles, portable defibrillators, and pulse power applications. Dielectric film capacitors represent an exceptional alternative for developing high energy density capacitors due to their high dielectric constants, outstanding breakdown voltages, and flexibility. The implementation of high aspect ratio dielectric inclusions such as nanowires into polymer capacitors could lead to further enhancement of its energy density. Therefore, this research effort is focused on the development of a new series of dielectric capacitors composed of nanowire reinforced polymer matrix composites. This concept of nanocomposite capacitors combines the extraordinary physical and chemical properties of the one-dimension (1D) nanoceramics and high dielectric strength of polymer matrices, leading to a capacitor with improved dielectric properties and energy density. Lead-free sodium niobate (NaNbO3) and lead-containing lead magnesium niobate-lead titanate (0.65PMN-0.35PT) nanowires were synthesized following hydrothermal and sol-gel approaches, respectively. The as-prepared nanowires were mixed with a polyvinylidene fluoride (PVDF) matrix using solution-casting method for nanocomposites fabrication. The dielectric constants and breakdown voltages of the NaNbO3/PVDF and 0.65PMN-0.35PT/PVDF nanocomposites were measured under different frequency ranges and temperatures in order to determine their maximum energy (J/cm3) and specific (J/g) densities. The electrical properties of the synthesized nanoceramics were compared with commercially available barium titanate (BaTiO3) and lead zirconate titanate Pb(ZrxTi1-x)O3 powders embedded into a PVDF matrix. The resulting dielectric film capacitors represent an excellent alternative energy storage device for future high energy density applications.

Low-loss electromagnetic composites for RF and microwave applications.

PubMed

Wang, Hong; Yang, Haibo; Xiang, Feng; Yao, Xi

2011-09-01

Low-loss electromagnetic composites with high permittivity and permeability will benefit the miniaturization and multifunctional of RF devices. A kind of low-loss dielectric-magnetic ceramic-ceramic composite was developed by hybrid processing technology with the goal of integrating the dielectric properties and magnetic properties. The hybrid processing technology exhibits the advantage of lowered sintering temperatures for the composites while retaining good microstructure and high performance. By introducing elastomer as matrix, a kind of flexible low-loss dielectric-magnetic ceramic-polymer composite was prepared and studied. The obtained flexible dielectric-magnetic ceramic-polymer composite exhibited low loss and good mechanical properties. The results show good effects on lowering the dielectric loss and extending the cut-off magnetic frequency of the electromagnetic composite. Methods for tailoring the properties of the multifunctional composites were proposed and discussed.

Magnetic and Dielectric Property Studies in Fe- and NiFe-Based Polymer Nanocomposites

NASA Astrophysics Data System (ADS)

Sharma, Himani; Jain, Shubham; Raj, Pulugurtha Markondeya; Murali, K. P.; Tummala, Rao

2015-10-01

Metal-polymer composites were investigated for their microwave properties in the frequency range of 30-1000 MHz to assess their application as inductor cores and electromagnetic isolation shield structures. NiFe and Fe nanoparticles were dispersed in epoxy as nanocomposites, in different volume fractions. The permittivity, permeability, and loss tangents of the composites were measured with an impedance analyzer and correlated with the magnetic properties of the particle such as saturation magnetization and field anisotropy. Fe-epoxy showed lower magnetic permeability but improved frequency stability, compared to the NiFe-epoxy composites of the same volume loading. This is attributed to the differences in nanoparticle's structure such as effective metal core size and particle-porosity distribution in the polymer matrix. The dielectric properties of the nanocomposites were also characterized from 30 MHz to 1000 MHz. The instabilities in the dielectric constant and loss tangent were related to the interfacial polarization relaxation of the particles and the dielectric relaxation of the surface oxides.

Nonvolatile memory characteristics of organic thin film transistors using poly(2-hydroxyethyl methacrylate)-based polymer multilayer dielectric

NASA Astrophysics Data System (ADS)

Chen, Ying-Chih; Su, Yan-Kuin; Yu, Hsin-Chieh; Huang, Chun-Yuan; Huang, Tsung-Syun

2011-10-01

A wide hysteresis width characteristic (memory window) was observed in the organic thin film transistors (OTFTs) using poly(2-hydroxyethyl methacrylate) (PHEMA)-based polymer multilayers. In this study, a strong memory effect was also found in the pentacene-based OTFTs and the electric characteristics were improved by introducing PHEMA/poly(methyl methacrylate) (PMMA)/PHEMA trilayer to replace the conventional PHEMA monolayer or PMMA/PHEMA and PHEMA/PMMA bilayer as the dielectric layers of OTFTs. The memory effect was originated from the electron trapping and slow polarization of the dielectrics. The hydroxyl (-OH) groups inside the polymer dielectric were the main charge storage sites of the electrons. This charge-storage phenomenon could lead to a wide flat-band voltage shift (memory window, △VFB = 22 V) which is essential for the OTFTs' memory-related applications. Moreover, the fabricated transistors also exhibited significant switchable channel current due to the charge-storage and slow charge relaxation.

Method of making organic light emitting devices

DOEpatents

Shiang, Joseph John [Niskayuna, NY; Janora, Kevin Henry [Schenectady, NY; Parthasarathy, Gautam [Saratoga Springs, NY; Cella, James Anthony [Clifton Park, NY; Chichak, Kelly Scott [Clifton Park, NY

2011-03-22

The present invention provides a method for the preparation of organic light-emitting devices comprising a bilayer structure made by forming a first film layer comprising an electroactive material and an INP precursor material, and exposing the first film layer to a radiation source under an inert atmosphere to generate an interpenetrating network polymer composition comprising the electroactive material. At least one additional layer is disposed on the reacted first film layer to complete the bilayer structure. The bilayer structure is comprised within an organic light-emitting device comprising standard features such as electrodes and optionally one or more additional layers serving as a bipolar emission layer, a hole injection layer, an electron injection layer, an electron transport layer, a hole transport layer, exciton-hole transporting layer, exciton-electron transporting layer, a hole transporting emission layer, or an electron transporting emission layer.

Electrochemically mediated electrodeposition/electropolymerization to yield a glucose microbiosensor with improved characteristics.

PubMed

Chen, Xiaohong; Matsumoto, Norio; Hu, Yibai; Wilson, George S

2002-01-15

A procedure is described that provides for electrochemically mediated deposition of enzyme and a polymer layer permselective for endogenous electroactive species. Electrodeposition was first employed for the direct immobilization of glucose oxidase to produce a uniform, thin, and compact film on a Pt electrode. Electropolymerization of phenol was then employed to form an anti-interference and protective polyphenol film within the enzyme layer. In addition, a stability-reinforcing membrane derived from (3-aminopropyl)trimethoxysilane was constructed by electrochemically assisted cross-linking. This hybrid film outside the enzyme layer contributed to the improved stability and permselectivity. The resulting glucose sensor was characterized by a short response time (<4 s), high sensitivity (1200 nA/mM x cm2), low interference from endogenous electroactive species, and working lifetime of more than 50 days.

Photopatternable electrochromic materials from oxetane precursors.

PubMed

Leliège, Antoine; Barik, Satyananda; Skene, W G

2014-05-14

Conjugated thiophenoazomethine triads containing an acid sensitive oxetane group were prepared. The solution processable monomers were immobilized on glass and ITO coated glass substrates by photoacid induced cationic ring-opening polymerization (CROP) of the oxetane moiety. Photolithography using a photoacid generator and photosensitizer were used to pattern an electroactive polymer. Micro- and macroscale patterns ranging between 20 μm and 50 mm were possible with the electrochromic materials. The photopolymerized azomethine remained electroactive, and it could be repeatedly switched electrochemically between its neutral (mauve, λmax=535 nm) and oxidized (blue, λmax=585 nm) states without degradation. The electrochromic properties were evaluated in a simulated device where the colors were successfully cycled between blue (oxidized) and purple (neutral) states with applied biases of +0.6 V and -0.6 V vs Fc/Fc+ under ambient conditions without significant color fatigue or degradation.

Moldable elastomeric polyester-carbon nanotube scaffolds for cardiac tissue engineering.

PubMed

Ahadian, Samad; Davenport Huyer, Locke; Estili, Mehdi; Yee, Bess; Smith, Nathaniel; Xu, Zhensong; Sun, Yu; Radisic, Milica

2017-04-01

Polymer biomaterials are used to construct scaffolds in tissue engineering applications to assist in mechanical support, organization, and maturation of tissues. Given the flexibility, electrical conductance, and contractility of native cardiac tissues, it is desirable that polymeric scaffolds for cardiac tissue regeneration exhibit elasticity and high electrical conductivity. Herein, we developed a facile approach to introduce carbon nanotubes (CNTs) into poly(octamethylene maleate (anhydride) 1,2,4-butanetricarboxylate) (124 polymer), and developed an elastomeric scaffold for cardiac tissue engineering that provides electrical conductivity and structural integrity to 124 polymer. 124 polymer-CNT materials were developed by first dispersing CNTs in poly(ethylene glycol) dimethyl ether porogen and mixing with 124 prepolymer for molding into shapes and crosslinking under ultraviolet light. 124 polymers with 0.5% and 0.1% CNT content (wt) exhibited improved conductivity against pristine 124 polymer. With increasing the CNT content, surface moduli of hybrid polymers were increased, while their bulk moduli were decreased. Furthermore, increased swelling of hybrid 124 polymer-CNT materials was observed, suggesting their improved structural support in an aqueous environment. Finally, functional characterization of engineered cardiac tissues using the 124 polymer-CNT scaffolds demonstrated improved excitation threshold in materials with 0.5% CNT content (3.6±0.8V/cm) compared to materials with 0% (5.1±0.8V/cm) and 0.1% (5.0±0.7V/cm), suggesting greater tissue maturity. 124 polymer-CNT materials build on the advantages of 124 polymer elastomer to give a versatile biomaterial for cardiac tissue engineering applications. Achieving a high elasticity and a high conductivity in a single cardiac tissue engineering material remains a challenge. We report the use of CNTs in making electrically conductive and mechanically strong polymeric scaffolds in cardiac tissue regeneration. CNTs were incorporated in elastomeric polymers in a facile and reproducible approach. Polymer-CNT materials were able to construct complicated scaffold structures by injecting the prepolymer into a mold and crosslinking the prepolymer under ultraviolet light. CNTs enhanced electrical conductivity and structural support of elastomeric polymers. Hybrid polymeric scaffolds containing 0.5wt% CNTs increased the maturation of cardiac tissues fabricated on them compared to pure polymeric scaffolds. The cardiac tissues on hybrid polymer-CNT scaffolds showed earlier beating than those on pure polymer scaffolds. In the future, fabricated polymer-CNT scaffolds could also be used to fabricate other electro-active tissues, such neural and skeletal muscle tissues. In the future, fabricated polymer-CNT scaffolds could also be used to fabricate other electro-active tissues, such as neural and skeletal muscle tissues. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Dielectric relaxation of near-percolated carbon nanofiber polypropylene composites

NASA Astrophysics Data System (ADS)

Paleo, A. J.; Zille, A.; Van Hattum, F. W.; Ares-Pernas, A.; Agostinho Moreira, J.

2017-07-01

In this work, the morphological, structural and dielectric analysis of near-percolated polypropylene (PP) composites containing carbon nanofibers (CNF) processing by melt-mixing are investigated. Whereas the morphological analysis shows that CNF exhibit some tendency to agglomerate within the PP matrix, the structural analysis showed first a general decrease in the intensity of the IR bands as a consequence of the interaction between carbon nanofibers and PP matrix and second an increase of the crystallinity degree of the PP/CNF composites when compared to the pure PP. The dielectric analysis demonstrates enhanced dielectric constants (from 2.97 for neat polymer to 9.7 for 1.9 vol% loaded composites at 200 Hz) and low dielectric losses. Furthermore, the dielectric relaxation for composites with concentrations in the vicinity of percolation is evidenced and well described by the generalized polydispersive Cole-Cole model from which the values of static dielectric constant (εs) , high frequency dielectric constant (ε∞) , distribution of relaxation time (α) and mean relaxation time (τo), are determined, suggesting that this latter analysis constitutes a strong tool for understanding the relationships between microstructure and dielectric properties in this type of polymer composites.

The NRL Program on Electroactive Polymers.

DTIC Science & Technology

1980-09-15

cell of a point in an aggregate involves selecting the smallest cell formed by planes perpendicularly bisecting all the point to neighbor vectors . Such...plane perpendicular to the interatomic vector is located nearer the smaller atom by bisecting the distance between the sur- faces of spheres whose...density waves (and consequent novel excitations such as solitons (6)). The physical structure as well as the chemical bonding of such polymeric

Piezoelectric Polymer/Ceramic Composite

DTIC Science & Technology

1989-05-02

allowed the production of films with a good surface structure. Samples were then thoroughly cleaned with isopropyl alcohol in an ultrasonic bath to...TrFe (Solef 11010) were kindly supplied by Laporte Industries of Lutcn, U.K. Electroactive properties of four composite films, together with those of...Piezel (see Appendix for specification), a commercially available composite of PZT/VDF-TrFE, manufactured by the Daikin Industry Limited of Japan have

Electroactive Polymers as Environmentally Benign Coating Replacements for Cadmium Plating on High Strength Steels

DTIC Science & Technology

2008-06-01

using a modified tap wrench around the square bulk section, within the required 3 to 20 seconds, with an average of approximately 10 seconds. vi...My Documents\\Wa~tz\\Zarras sa~t foq pane~s\\Stee~ 1x3 pane~s\\PZ1764-76PS 24 hrs\\b o ttom ~ eft darker area 22X. spc Labe~ :Adhesion promoter

High-Performance Polymers Sandwiched with Chemical Vapor Deposited Hexagonal Boron Nitrides as Scalable High-Temperature Dielectric Materials.

PubMed

Azizi, Amin; Gadinski, Matthew R; Li, Qi; AlSaud, Mohammed Abu; Wang, Jianjun; Wang, Yi; Wang, Bo; Liu, Feihua; Chen, Long-Qing; Alem, Nasim; Wang, Qing

2017-09-01

Polymer dielectrics are the preferred materials of choice for power electronics and pulsed power applications. However, their relatively low operating temperatures significantly limit their uses in harsh-environment energy storage devices, e.g., automobile and aerospace power systems. Herein, hexagonal boron nitride (h-BN) films are prepared from chemical vapor deposition (CVD) and readily transferred onto polyetherimide (PEI) films. Greatly improved performance in terms of discharged energy density and charge-discharge efficiency is achieved in the PEI sandwiched with CVD-grown h-BN films at elevated temperatures when compared to neat PEI films and other high-temperature polymer and nanocomposite dielectrics. Notably, the h-BN-coated PEI films are capable of operating with >90% charge-discharge efficiencies and delivering high energy densities, i.e., 1.2 J cm -3 , even at a temperature close to the glass transition temperature of polymer (i.e., 217 °C) where pristine PEI almost fails. Outstanding cyclability and dielectric stability over a straight 55 000 charge-discharge cycles are demonstrated in the h-BN-coated PEI at high temperatures. The work demonstrates a general and scalable pathway to enable the high-temperature capacitive energy applications of a wide range of engineering polymers and also offers an efficient method for the synthesis and transfer of 2D nanomaterials at the scale demanded for applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Shellac Films as a Natural Dielectric Layer for Enhanced Electron Transport in Polymer Field-Effect Transistors.

PubMed

Baek, Seung Woon; Ha, Jong-Woon; Yoon, Minho; Hwang, Do-Hoon; Lee, Jiyoul

2018-06-06

Shellac, a natural polymer resin obtained from the secretions of lac bugs, was evaluated as a dielectric layer in organic field-effect transistors (OFETs) on the basis of donor (D)-acceptor (A)-type conjugated semiconducting copolymers. The measured dielectric constant and breakdown field of the shellac layer were ∼3.4 and 3.0 MV/cm, respectively, comparable with those of a poly(4-vinylphenol) (PVP) film, a commonly used dielectric material. Bottom-gate/top-contact OFETs were fabricated with shellac or PVP as the dielectric layer and one of three different D-A-type semiconducting copolymers as the active layer: poly(cyclopentadithiophene- alt-benzothiadiazole) with p-type characteristics, poly(naphthalene-bis(dicarboximide)- alt-bithiophene) [P(NDI2OD-T2)] with n-type characteristics, and poly(dithienyl-diketopyrrolopyrrole- alt-thienothiophene) [P(DPP2T-TT)] with ambipolar characteristics. The electrical characteristics of the fabricated OFETs were then measured. For all active layers, OFETs with a shellac film as the dielectric layer exhibited a better mobility than those with PVP. For example, the mobility of the OFET with a shellac dielectric and n-type P(NDI2OD-T2) active layer was approximately 2 orders of magnitude greater than that of the corresponding OFET with a PVP insulating layer. When P(DPP2T-TT) served as the active layer, the OFET with shellac as the dielectric exhibited ambipolar characteristics, whereas the corresponding OFET with the PVP dielectric operated only in hole-accumulation mode. The total density of states was analyzed using technology computer-aided design simulations. The results revealed that compared with the OFETs with PVP as the dielectric, the OFETs with shellac as the dielectric had a lower trap-site density at the polymer semiconductor/dielectric interface and much fewer acceptor-like trap sites acting as electron traps. These results demonstrate that shellac is a suitable dielectric material for D-A-type semiconducting copolymer-based OFETs, and the use of shellac as a dielectric layer facilitates electron transport at the interface with D-A-type copolymer channels.

Method for producing high dielectric strength microvalves

DOEpatents

Kirby, Brian J [San Francisco, CA; Reichmuth, David S [Oakland, CA; Shepodd, Timothy J [Livermore, CA

2006-04-04

A microvalve having a cast-in-place and lithographically shaped mobile, polymer monolith for fluid flow control in microfluidic devices and method of manufacture. The microvalve contains a porous fluorinated polymer monolithic element whose pores are filled with an electrically insulating, high dielectric strength fluid, typically a perfluorinated liquid. This combination provides a microvalve that combines high dielectric strength with extremely low electrical conductivity. These microvalves have been shown to have resistivities of at least 100 G.OMEGA. and are compatible with solvents such as water at a pH between 2.7 and 9.0, 1-1 propanol, acetonitrile, and acetone.

Investigation of dielectric breakdown in silica-epoxy nanocomposites using designed interfaces.

PubMed

Bell, Michael; Krentz, Timothy; Keith Nelson, J; Schadler, Linda; Wu, Ke; Breneman, Curt; Zhao, Su; Hillborg, Henrik; Benicewicz, Brian

2017-06-01

Adding nano-sized fillers to epoxy has proven to be an effective method for improving dielectric breakdown strength (DBS). Evidence suggests that dispersion state, as well as chemistry at the filler-matrix interface can play a crucial role in property enhancement. Herein we investigate the contribution of both filler dispersion and surface chemistry on the AC dielectric breakdown strength of silica-epoxy nanocomposites. Ligand engineering was used to synthesize bimodal ligands onto 15nm silica nanoparticles consisting of long epoxy compatible, poly(glycidyl methacrylate) (PGMA) chains, and short, π-conjugated, electroactive surface ligands. Surface initiated RAFT polymerization was used to synthesize multiple graft densities of PGMA chains, ultimately controlling the dispersion of the filler. Thiophene, anthracene, and terthiophene were employed as π-conjugated surface ligands that act as electron traps to mitigate avalanche breakdown. Investigation of the synthesized multifunctional nanoparticles was effective in defining the maximum particle spacing or free space length (L f ) that still leads to property enhancement, as well as giving insight into the effects of varying the electronic nature of the molecules at the interface on breakdown strength. Optimization of the investigated variables was shown to increase the AC dielectric breakdown strength of epoxy composites as much as 34% with only 2wt% silica loading. Copyright © 2017 Elsevier Inc. All rights reserved.

Computational screening of organic polymer dielectrics for novel accelerator technologies

DOE PAGES

Pilania, Ghanshyam; Weis, Eric; Walker, Ethan M.; ...

2018-06-18

The use of infrared lasers to power accelerating dielectric structures is a developing area of research. Within this technology, the choice of the dielectric material forming the accelerating structures, such as the photonic band gap (PBG) structures, is dictated by a range of interrelated factors including their dielectric and optical properties, amenability to photo-polymerization, thermochemical stability and other target performance metrics of the particle accelerator. In this direction, electronic structure theory aided computational screening and design of dielectric materials can play a key role in identifying potential candidate materials with the targeted functionalities to guide experimental synthetic efforts. In anmore » attempt to systematically understand the role of chemistry in controlling the electronic structure and dielectric properties of organic polymeric materials, here we employ empirical screening and density functional theory (DFT) computations, as a part of our multi-step hierarchal screening strategy. Our DFT based analysis focused on the bandgap, dielectric permittivity, and frequency-dependent dielectric losses due to lattice absorption as key properties to down-select promising polymer motifs. In addition to the specific application of dielectric laser acceleration, the general methodology presented here is deemed to be valuable in the design of new insulators with an attractive combination of dielectric properties.« less

Substantial enhancement of energy storage capability in polymer nanocomposites by encapsulation of BaTiO3 NWs with variable shell thickness.

PubMed

Wang, Guanyao; Huang, Yanhui; Wang, Yuxin; Jiang, Pingkai; Huang, Xingyi

2017-08-09

Dielectric polymer nanocomposites have received keen interest due to their potential application in energy storage. Nevertheless, the large contrast in dielectric constant between the polymer and nanofillers usually results in a significant decrease of breakdown strength of the nanocomposites, which is unfavorable for enhancing energy storage capability. Herein, BaTiO 3 nanowires (NWs) encapsulated by TiO 2 shells of variable thickness were utilized to fabricate dielectric polymer nanocomposites. Compared with nanocomposites with bare BaTiO 3 NWs, significantly enhanced energy storage capability was achieved for nanocomposites with TiO 2 encapsulated BaTiO 3 NWs. For instance, an ultrahigh energy density of 9.53 J cm -3 at 440 MV m -1 could be obtained for nanocomposites comprising core-shell structured nanowires, much higher than that of nanocomposites with 5 wt% raw ones (5.60 J cm -3 at 360 MV m -1 ). The discharged energy density of the proposed nanocomposites with 5 wt% mTiO 2 @BaTiO 3 -1 NWs at 440 MV m -1 seems to rival or exceed those of some previously reported nanocomposites (mostly comprising core-shell structured nanofillers). More notably, this study revealed that the energy storage capability of the nanocomposites can be tailored by the TiO 2 shell thickness. Finite element simulations were employed to analyze the electric field distribution in the nanocomposites. The enhanced energy storage capability should be mainly attributed to the smoother gradient of dielectric constant between the nanofillers and polymer matrix, which alleviated the electric field concentration and leakage current in the polymer matrix. The methods and results herein offer a feasible approach to construct high-energy-density polymer nanocomposites with core-shell structured nanowires.

Investigation of ITO free transparent conducting polymer based electrode

NASA Astrophysics Data System (ADS)

Sharma, Vikas; Sapna, Sachdev, Kanupriya

2016-05-01

The last few decades have seen a significant improvement in organic semiconductor technology related to solar cell, light emitting diode and display panels. The material and structure of the transparent electrode is one of the major concerns for superior performance of devices such as OPV, OLED, touch screen and LCD display. Commonly used ITO is now restricted due to scarcity of indium, its poor mechanical properties and rigidity, and mismatch of energy levels with the active layer. Nowadays DMD (dielectric-metal-dielectric) structure is one of the prominent candidates as alternatives to ITO based electrode. We have used solution based spin coated polymer layer as the dielectric layer with silver thin film embedded in between to make a polymer-metal-polymer (PMP) structure for TCE applications. The PMP structure shows low resistivity (2.3 x 10-4Ω-cm), high carrier concentration (2.9 x 1021 cm-3) and moderate transparency. The multilayer PMP structure is characterized with XRD, AFM and Hall measurement to prove its suitability for opto-electronic device applications.

Predictive methods of some optoelectronic properties for blends based on quaternized polysulfones

NASA Astrophysics Data System (ADS)

Dobos, Adina Maria; Filimon, Anca

2017-11-01

Blends based on quaternized polysulfones were investigated in terms of optical and electronic properties. By applying the Bicerano formalism the refractive index and dielectric constant were evaluated. Also, the dielectric constant of these blends was studied as a function of temperature and frequency. As the result of the main chain structure and charged groups, an increase in theoretical values of the refractive index and dielectric constant with increasing of the ionic quaternized units content in the polymer blend occurs. Additionally, decrease in the dielectric constant with the increase of frequency and decrease of temperature was observed. Refractive index and dielectric constant values indicate that the analyzed samples are transparent and can be used in obtaining of materials with applications involving a small polarizability. Thus, the results are important in prediction of the special optoelectronic features of new polymers blends to obtain high-performance materials with applications in electronic and biomedical fields.

Fabrication of PVDF-TrFE based bilayered PbTiO3/PVDF-TrFE films capacitor

NASA Astrophysics Data System (ADS)

Nurbaya, Z.; Wahid, M. H.; Rozana, M. D.; Annuar, I.; Alrokayan, S. A. H.; Khan, H. A.; Rusop, M.

2016-07-01

Development of high performance capacitor is reaching towards new generation where the ferroelectric materials take places as the active dielectric layer. The motivation of this study is to produce high capacitance device with long life cycle. This was configured by preparing bilayered films where lead titanate as an active dielectric layer and stacked with the top dielectric layer, poly(vinyledenefluoride-trifluoroethylene). Both of them are being referred that have one in common which is ferroelectric behavior. Therefore the combination of ceramic and polymer ferroelectric material could perform optimum dielectric characteristic for capacitor applications. The fabrication was done by simple sol-gel spin coating method that being varied at spinning speed property for polymer layers, whereas maintaining the ceramic layer. The characterization of PVDF-TrFE/PbTiO3 was performed according to metal-insulator-metal stacked capacitor measurement which includes structural, dielectric, and ferroelectric measurement.

Conductivity and dielectric behaviour of PEO-based solid nanocomposite polymer electrolytes

NASA Astrophysics Data System (ADS)

Ibrahim, Suriani; Mohd Yasin, Siti Mariah; Nee, Ng Meng; Ahmad, Roslina; Johan, Mohd Rafie

2012-03-01

In this research, thin films of poly(ethylene oxide) (PEO) blend with lithium hexafluorophosphate (LiPF) salt and ethylene carbonate (EC) as plasticiser and carbon nanotube (CNT) as filler, are prepared using solution casting method. The conductivity and dielectric response of the nanocomposite polymer electrolyte systems are studied within the broad frequency range of 5 Hz-5 MHz and within a temperature range of 298-373 K. The conductivity-temperature plots are observed to be of Arrhenius nature. The dielectric behaviour is analysed using the dielectric permittivity (ɛr and ɛi), loss tangent (tanδ) and electric modulus (Mi and Mr) of the samples. It is observed that the dielectric permittivity rises sharply towards low frequencies due to electrode polarisation effects. The maxima of the loss tangent (tanδ) shifts towards higher frequencies and the height of the peak increases with increasing temperature.

Analysis and experiment on a self-sensing ionic polymer-metal composite actuator

NASA Astrophysics Data System (ADS)

Nam, Doan Ngoc Chi; Ahn, Kyoung Kwan

2014-07-01

An ionic polymer-metal composite (IPMC) actuator is an electro-active polymer (EAP) that bends in response to a small applied electrical field as a result of the mobility of cations in the polymer network. This paper aims to develop a self-sensing actuator for practical use, since current sensing methods generally face limitations due to the compact size and mobility of the IPMC actuator. Firstly, the variation of surface resistance during bending operations is investigated. Then, the behavior of IPMC corresponding to the variation of surface resistance is mathematically analyzed. Based on the analysis results, a simple configuration to realize the self-sensing behavior is introduced. In this technique, the bending curvature of an IPMC can be obtained accurately by employing several feedback voltage signals along with the IPMC length. Finally, experimental evaluations proved the ability of the proposed scheme to estimate the bending behavior of IPMC actuators.

Electroactive polymers containing 3-arylcarbazolyl units as hole transporting materials for OLEDs

NASA Astrophysics Data System (ADS)

Krucaite, G.; Liu, L.; Tavgeniene, D.; Peciulyte, L.; Grazulevicius, J. V.; Xie, Z.; Zhang, B.; Grigalevicius, S.

2015-04-01

Monomers and their polymers containing 3-arylcarbazolyl electrophores have been synthesized by the multi-step synthetic route. The materials were characterized by thermo-gravimetric analysis, differential scanning calorimetry and electron photoemission technique. The polymers represent materials of high thermal stability having initial thermal degradation temperatures in the range of 331-411 °C. The glass transition temperatures of the amorphous polymeric materials were in the rage of 148-175 °C. The electron photoemission spectra of thin layers of monomers showed ionization potentials in the range of 5.6-5.65 eV. Hole-transporting properties of the polymers were tested in the structures of organic light emitting diodes with Alq3 as the green emitter. The device containing hole-transporting layers of polyether with 3-naphthylcarbazolyl groups exhibited the best overall performance with a maximum current efficiency of 3.3 cd/A and maximum brightness of about 1000 cd/m2.

Composite membranes from photochemical synthesis of ultrathin polymer films

NASA Astrophysics Data System (ADS)

Liu, Chao; Martin, Charles R.

1991-07-01

THERE has recently been a resurgence of interest in synthetic membranes and membrane-based processes1-12. This is motivated by a wide variety of technological applications, such as chemical separations1-7, bioreactors and sensors8,9, energy conversion10,11 and drug-delivery systems12. Many of these technologies require the ability to prepare extremely thin, defect-free synthetic (generally polymeric) films, which are supported on microporous supports to form composite membranes. Here we describe a method for producing composite membranes of this sort that incorporate high-quality polymer films less than 50-nm thick. The method involves interfacial photopolymerization of a thin polymer film on the surface of the microporous substrate. We have been able to use this technique to synthesize a variety of functionalized ultrathin films based on electroactive, photoactive and ion-exchange polymers. We demonstrate the method here with composite membranes that show exceptional gas-transport properties.

Polymers containing isolated phenylvinyl substituted carbazole rings as electroactive materials for OLEDs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Griniene, Raimonda; Tavgeniene, Daiva, E-mail: daiva.tavgen@gmail.com; Grigalevičius, Saulius

2016-05-18

Polymers containing pendent 3-(2-phenylvinyl)carbazole moieties have been synthesized by the multi-step synthetic route. The polymers represent materials of high thermal stability with initial thermal degradation temperatures exceeding 370 °C. The glass transition temperatures of the amorphous materials were in the rage of 56–65 °C. The electron photoemission spectra of thin layers of the polymers showed ionization potentials of about 5.6 eV. Hole-transporting properties of the polymeric materials were tested in the structures of organic light emitting diodes with Alq 3 as the green emitter. The device containing hole-transporting layers of poly{9-[6-(3-methyloxetan-3-ylmethoxy)hexyl]-3-(2-phenylvinyl)carbazole} exhibited the best overall performance with a maximum photometricmore » efficiency of about 4.0 cd/A and maximum brightness exceeding 6430 cd/m{sup 2}.« less

Synthesis, characterization and antioxidant activity of a novel electroactive and biodegradable polyurethane for cardiac tissue engineering application.

PubMed

Baheiraei, Nafiseh; Yeganeh, Hamid; Ai, Jafar; Gharibi, Reza; Azami, Mahmoud; Faghihi, Faezeh

2014-11-01

There has been a growing trend towards applying conducting polymers for electrically excitable cells to increase electrical signal propagation within the cell-loaded substrates. A novel biodegradable electroactive polyurethane containing aniline pentamer (AP-PU) was synthesized and fully characterized by spectroscopic methods. To tune the physico-chemical properties and biocompatibility, the AP-PU was blended with polycaprolactone (PCL). The presence of electroactive moieties and the electroactivity behavior of the prepared films were confirmed by UV-visible spectroscopy and cyclic voltammetry. A conventional four probe analysis demonstrated the electrical conductivity of the films in the semiconductor range (~10(-5)S/cm). MTT assays using L929 mouse fibroblast and human umbilical vein endothelial cells (HUVECs) showed that the prepared blend (PB) displayed more cytocompatibility compared with AP-PU due to the introduction of a biocompatible PCL moiety. The in vitro cell culture also confirmed that PB was as supportive as tissue culture plate. The antioxidant activity of the AP-PU was proved using 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging assay by employing UV-vis spectroscopy. In vitro degradation tests conducted in phosphate-buffered saline, pH7.4 and pH5.5, proved that the films were also biodegradable. The results of this study have highlighted the potential application of this bioelectroactive polyurethane as a platform substrate to study the effect of electrical signals on cell activities and to direct desirable cell function for tissue engineering applications. Copyright © 2014 Elsevier B.V. All rights reserved.

Electroactive Reactive Oligomers and Polymers as Device Components

DTIC Science & Technology

2009-02-03

promise to impact the development of reflective and transmissive color-changing systems spanning ’smart’ polyclu’omic glassing technologies and e-papers...mediated cross-coupling reactions. While the first substitution is expected to have the largest impact on the energy gap of the donor-acceptor system, a...transmissive device applications, it is expected that processable black to transmissive analogues will impact the development of EC windows, e- papers and

Motion of Doped-Polymer-Cholesteric Liquid Crystal Flakes in a Direct-Current Electric Field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trajkovska Petkoska, A.; Kosc, T.Z.; Marshall, K.L.

The behavior of polymer cholesteric liquid crystal (PCLC) flakes suspended in silicone oil host fluids has been explored in the presence of a direct-current electric field. In addition to “neat” (undoped) flakes, the PCLC material was doped with either conductive, carbon-based particles or highly dielectric inorganic particles to modify the dielectric properties of the resulting PCLC flakes. Doping with conductive particles produced flakes with a net charge, and they exhibited either translational or rotational motion depending on both the distribution of dopant within the flake and the dielectric characteristics of the host fluid. Flakes doped with titania (TiO2) particles reorientedmore » 90º when suspended in a host fluid with a differing dielectric permittivity« less

High precision slotted cavity measurement of a novel ceramic state polymer electrolyte

NASA Astrophysics Data System (ADS)

Quan, Wei; NurulAfsar, Mohammed

2018-01-01

Thin film materials are already used in a variety of microwave and higher frequency applications such as electrically tunable microwave devices, integrated circuits like MMICs, radomes, and radar absorbing coating. The determination of the dielectric properties of these films is thus of significant importance. The measurement of complex dielectric permittivity of thin films is very difficult at microwave, millimeter, and THz frequencies because both the amplitude change and phase shift are not large enough to evaluate the real part of the dielectric permittivity. A specially designed transverse slotted cavity for X-band microwave measurement has been designed and constructed to employ with a vector network analyzer to evaluate the real part of dielectric permittivity of thin films accurately and conveniently. Commercially available polymer thin films are measured to validate the methods.

High-Mobility 6,13-Bis(triisopropylsilylethynyl) Pentacene Transistors Using Solution-Processed Polysilsesquioxane Gate Dielectric Layers.

PubMed

Matsuda, Yu; Nakahara, Yoshio; Michiura, Daisuke; Uno, Kazuyuki; Tanaka, Ichiro

2016-04-01

Polysilsesquioxane (PSQ) is a low-temperature curable polymer that is compatible with low-cost plastic substrates. We cured PSQ gate dielectric layers by irradiation with ultraviolet light at ~60 °C, and used them for 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-pentacene) thin film transistors (TFTs). The fabricated TFTs have shown the maximum and average hole mobility of 1.3 and 0.78 ± 0.3 cm2V-1s-1, which are comparable to those of the previously reported transistors using single-crystalline TIPS-pentacene micro-ribbons for their active layers and thermally oxidized SiO2 for their gate dielectric layers. Itis therefore demonstrated that PSQ is a promising polymer gate dielectric material for low-cost organic TFTs.

Tailorable Dielectric Material with Complex Permittivity Characteristics

NASA Technical Reports Server (NTRS)

Smith, Joseph G. (Inventor); Watson, Kent A. (Inventor); Elliott, Holly A (Inventor); Delozier, Donavon Mark (Inventor); Connell, John W. (Inventor); Ghose, Sayata (Inventor); Dudley, Kenneth L. (Inventor)

2014-01-01

A dielectric material includes a network of nanosubstrates, such as but not limited to nanotubes, nanosheets, or other nanomaterials or nanostructures, a polymer base material or matrix, and nanoparticles constructed at least partially of an elemental metal. The network has a predetermined nanosubstrate loading percentage by weight with respect to a total weight of the dielectric material, and a preferential or predetermined longitudinal alignment with respect to an orientation of an incident electrical field. A method of forming the dielectric material includes depositing the metal-based nanoparticles onto the nanosubstrates and subsequently mixing these with a polymer matrix. Once mixed, alignment can be achieved by melt extrusion or a similar mechanical shearing process. Alignment of the nanosubstrate may be in horizontal or vertical direction with respect to the orientation of an incident electrical field.

How fish swim: flexible fin thrusters as an EAP platform

NASA Astrophysics Data System (ADS)

Lauder, George V.

2007-04-01

Fish are capable of remarkable locomotor performance and use their fins extensively for both propulsion and maneuvering. Recent interest in using fishes as inspiration for the design of a new generation of autonomous underwater vehicles has prompted both new experimental studies of fish locomotor function and efforts to use electroactive polymers (EAP) as actuators in fish-inspired propulsive devices. The fins of fishes allow precise control over body position and vectoring of thrust during propulsion and maneuvering. Recent experimental studies of fish locomotion have revealed that fins exhibit much greater flexibility than previously suspected and that there is considerable deformation of the fin surface during locomotion. The fins of the large group known as ray-finned fishes are supported by fin rays, which have a bilaminar structure that allows active curvature control of the ray and fin surface by the fin musculature. Fish have up to seven different fins, and these fins may interact with each other hydrodynamically during locomotion. Fish fins provide an excellent test platform for the use of electroactive polymer actuators as the frequency of movement is typically less than 5 Hz, and fin muscle strains typically range from 2 to 10%. Recent developments of biorobotic fish pectoral fins actuated with EAP are reviewed.

A conducting polymer with enhanced electronic stability applied in cardiac models

PubMed Central

Mawad, Damia; Mansfield, Catherine; Lauto, Antonio; Perbellini, Filippo; Nelson, Geoffrey W.; Tonkin, Joanne; Bello, Sean O.; Carrad, Damon J.; Micolich, Adam P.; Mahat, Mohd M.; Furman, Jennifer; Payne, David; Lyon, Alexander R.; Gooding, J. Justin; Harding, Sian E.; Terracciano, Cesare M.; Stevens, Molly M.

2016-01-01

Electrically active constructs can have a beneficial effect on electroresponsive tissues, such as the brain, heart, and nervous system. Conducting polymers (CPs) are being considered as components of these constructs because of their intrinsic electroactive and flexible nature. However, their clinical application has been largely hampered by their short operational time due to a decrease in their electronic properties. We show that, by immobilizing the dopant in the conductive scaffold, we can prevent its electric deterioration. We grew polyaniline (PANI) doped with phytic acid on the surface of a chitosan film. The strong chelation between phytic acid and chitosan led to a conductive patch with retained electroactivity, low surface resistivity (35.85 ± 9.40 kilohms per square), and oxidized form after 2 weeks of incubation in physiological medium. Ex vivo experiments revealed that the conductive nature of the patch has an immediate effect on the electrophysiology of the heart. Preliminary in vivo experiments showed that the conductive patch does not induce proarrhythmogenic activities in the heart. Our findings set the foundation for the design of electronically stable CP-based scaffolds. This provides a robust conductive system that could be used at the interface with electroresponsive tissue to better understand the interaction and effect of these materials on the electrophysiology of these tissues. PMID:28138526

Finite element analysis of electroactive polymer and magnetoactive elastomer based actuation for origami folding

NASA Astrophysics Data System (ADS)

Zhang, Wei; Ahmed, Saad; Masters, Sarah; Ounaies, Zoubeida; Frecker, Mary

2017-10-01

The incorporation of smart materials such as electroactive polymers and magnetoactive elastomers in origami structures can result in active folding using external electric and magnetic stimuli, showing promise in many origami-inspired engineering applications. In this study, 3D finite element analysis (FEA) models are developed using COMSOL Multiphysics software for three configurations that incorporate a combination of active and passive material layers, namely: (1) a single-notch unimorph folding configuration actuated using only external electric field, (2) a double-notch unimorph folding configuration actuated using only external electric field, and (3) a bifold configuration which is actuated using multi-field (electric and magnetic) stimuli. The objectives of the study are to verify the effectiveness of the FEA models to simulate folding behavior and to investigate the influence of geometric parameters on folding quality. Equivalent mechanical pressure and surface stress are used as external loads in the FEA to simulate electric and magnetic fields, respectively. Compared quantitatively with experimental data, FEA captured the folding performance of electric actuation well for notched configurations and magnetic actuation for a bifold structure, but underestimated electric actuation for the bifold structure. By investigating the impact of geometric parameters and locations to place smart materials, FEA can be used in design, avoiding trial-and-error iterations of experiments.

Thickness dependence of curvature, strain, and response time in ionic electroactive polymer actuators fabricated via layer-by-layer assembly

NASA Astrophysics Data System (ADS)

Montazami, Reza; Liu, Sheng; Liu, Yang; Wang, Dong; Zhang, Qiming; Heflin, James R.

2011-05-01

Ionic electroactive polymer (IEAP) actuators containing porous conductive network composites (CNCs) and ionic liquids can result in high strain and fast response times. Incorporation of spherical gold nanoparticles in the CNC enhances conductivity and porosity, while maintaining relatively small thickness. This leads to improved mechanical strain and bending curvature of the actuators. We have employed the layer-by-layer self-assembly technique to fabricate a CNC with enhanced curvature (0.43 mm-1) and large net intrinsic strain (6.1%). The results demonstrate that curvature and net strain of IEAP actuators due to motion of the anions increase linearly with the thickness of the CNC as a result of the increased volume in which the anions can be stored. In addition, after subtracting the curvature of a bare Nafion actuator without a CNC, it is found that the net intrinsic strain of the CNC layer is independent of thickness for the range of 20-80 nm, indicating that the entire CNC volume contributes equivalently to the actuator motion. Furthermore, the response time of the actuator due to anion motion is independent of CNC thickness, suggesting that traversal through the Nafion membrane is the limiting factor in the anion motion.

Electroactive nanostructured polymer actuators fabricated using sulfonated styrenic pentablock copolymer/montmorillonite/ionic liquid nanocomposite membranes

NASA Astrophysics Data System (ADS)

Lee, Jang-Woo; Hong, Soon Man; Koo, Chong Min

2014-08-01

High-bendable, air-operable ionic polymer-metal composite (IPMC) actuators composed of electroactive nanostructured middle-block sulfonated styrenic pentablock copolymer (SSPB)/sulfonated montmorillonite (s-MMT) nanocomposite electrolyte membranes with bulky imidazolium ionic liquids (ILs) incorporated were fabricated and their bending actuation performances were evaluated. The SSPB-based IPMC actuators showed larger air-operable bending displacements, higher displacement rates, and higher energy efficiency of actuations without conventional IPMC bottlenecks, including back relaxation and actuation instability during actuation in air, than the Nafion counterpart. Incorporation of s-MMT into the SSPB matrix further enhanced the actuation performance of the IPMC actuators in terms of displacement, displacement rate, and energy efficiency. The remarkably high performance of the SSPB/s-MMT/IL IPMCs was considered to be due to the microphase-separated large ionic domains of the SSPB (the average diameter of the ionic domain: ca. 20 nm) and the role of s-MMT as an ionic bridge between the ionic domains, and the ion pumping effect of the bulky imidazolium cations of the ILs as well. The microphase-separated nanostructure of the composite membranes caused a high dimensional stability upon swelling in the presence of ILs, which effectively preserved the original electrode resistance against swelling, leading to a high actuation performance of IPMC.

Soft but Powerful Artificial Muscles Based on 3D Graphene-CNT-Ni Heteronanostructures.

PubMed

Kim, Jaehwan; Bae, Seok-Hu; Kotal, Moumita; Stalbaum, Tyler; Kim, Kwang J; Oh, Il-Kwon

2017-08-01

Bioinspired soft ionic actuators, which exhibit large strain and high durability under low input voltages, are regarded as prospective candidates for future soft electronics. However, due to the intrinsic drawback of weak blocking force, the feasible applications of soft ionic actuators are limited until now. An electroactive artificial muscle electro-chemomechanically reinforced with 3D graphene-carbon nanotube-nickel heteronanostructures (G-CNT-Ni) to improve blocking force and bending deformation of the ionic actuators is demonstrated. The G-CNT-Ni heteronanostructure, which provides an electrically conductive 3D network and sufficient contact area with mobile ions in the polymer electrolyte, is embedded as a nanofiller in both ionic polymer and conductive electrodes of the ionic actuators. An ionic exchangeable composite membrane consisting of Nafion, G-CNT-Ni and ionic liquid (IL) shows improved tensile modulus and strength of up to 166% and 98%, respectively, and increased ionic conductivity of 0.254 S m -1 . The ionic actuator exhibits enhanced actuation performances including three times larger bending deformation, 2.37 times higher blocking force, and 4 h durability. The electroactive artificial muscle electro-chemomechanically reinforced with 3D G-CNT-Ni heteronanostructures offers improvements over current soft ionic actuator technologies and can advance the practical engineering applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Parylene-coated ionic liquid-carbon nanotube actuators for user-safe haptic devices.

PubMed

Bubak, Grzegorz; Gendron, David; Ceseracciu, Luca; Ansaldo, Alberto; Ricci, Davide

2015-07-22

Simple fabrication, high power-to-weight and power-to-volume ratios, and the ability to operate in open air at low voltage make the ionic electroactive polymer actuators highly attractive for haptic applications. Whenever a direct tactile stimulation of the skin is involved, electrical and chemical insulation as well as a long-term stability of the actuator are required. Because of its inherent physicochemical properties such as high dielectric strength, resistance to solvents, and biological inactivity, Parylene C meets the requirements for making biocompatible actuators. We have studied the displacement and the generated force of Parylene-coated carbon nanotube actuators as well as the encapsulation quality. A 2 μm coating creates an effective electrical insulation of the actuators without altering the blocking force at frequencies from 50 mHz to 1 Hz. Moreover, the generated strain is preserved at higher frequencies (from 0.5 to 5 Hz). We employed a simple mechanical model to explain the relation between the key parameters-flexural stiffness, displacement, and force-for uncoated and coated actuators. In addition, we demonstrated that our Parylene-coated actuators are not damaged by rinsing in liquid media such as 2-propanol or water. In conclusion, our results indicate that Parylene C encapsulated actuators are safe to touch and can be used in contact with human skin and in biomedical applications in direct contact with tissues and physiological fluids.

Biohybrid Control of General Linear Systems Using the Adaptive Filter Model of Cerebellum.

PubMed

Wilson, Emma D; Assaf, Tareq; Pearson, Martin J; Rossiter, Jonathan M; Dean, Paul; Anderson, Sean R; Porrill, John

2015-01-01

The adaptive filter model of the cerebellar microcircuit has been successfully applied to biological motor control problems, such as the vestibulo-ocular reflex (VOR), and to sensory processing problems, such as the adaptive cancelation of reafferent noise. It has also been successfully applied to problems in robotics, such as adaptive camera stabilization and sensor noise cancelation. In previous applications to inverse control problems, the algorithm was applied to the velocity control of a plant dominated by viscous and elastic elements. Naive application of the adaptive filter model to the displacement (as opposed to velocity) control of this plant results in unstable learning and control. To be more generally useful in engineering problems, it is essential to remove this restriction to enable the stable control of plants of any order. We address this problem here by developing a biohybrid model reference adaptive control (MRAC) scheme, which stabilizes the control algorithm for strictly proper plants. We evaluate the performance of this novel cerebellar-inspired algorithm with MRAC scheme in the experimental control of a dielectric electroactive polymer, a class of artificial muscle. The results show that the augmented cerebellar algorithm is able to accurately control the displacement response of the artificial muscle. The proposed solution not only greatly extends the practical applicability of the cerebellar-inspired algorithm, but may also shed light on cerebellar involvement in a wider range of biological control tasks.

Dielectric characteristics of CaCu3Ti4O12/P(VDF-TrFE) nanocomposites

NASA Astrophysics Data System (ADS)

Zhang, Lin; Shan, Xiaobing; Wu, Peixuan; Cheng, Z.-Y.

2012-06-01

Composite thin film is highly desirable for the dielectric applications. In order to develop composite thin film, a nanocomposite, in which nanosized CaCu3Ti4O12 (CCTO) particles are used as filler and P(VDF-TrFE) 55/45 mol% copolymer is used as polymer matrix, is investigated. The contents of CCTO in the nanocomposites range from 0% to 50 vol%. The dielectric property of these nanocomposites was characterized at frequencies ranging from 100 Hz to 1 MHz and at temperatures ranging from 200 K to 370 K. A dielectric constant of 62 with a loss of 0.05 was obtained in nanocomposite with 50 vol% CCTO at room temperature at 1 kHz. At the phase transition temperature (˜340 K) of the copolymer, a dielectric constant of 150 with a loss less than 0.1 was obtained in this nanocomposite. It is found that the dielectric loss of the nanocomposites is dominated by the polymer which has a relaxation process. Comparing to composites made using microsized CCTO, the nanocomposites exhibit a much lower dielectric loss and a lower dielectric constant. This indicates that the nanosized CCTO particles have a lower dielectric constant than the microsized CCTO particles.

Molecular dynamics simulation of low dielectric constant polymer electrolytes

NASA Astrophysics Data System (ADS)

Wheatle, Bill; Lynd, Nathaniel; Ganesan, Venkat

Recent experimental studies measured the ionic conductivities of a series of poly(glycidyl ether)s with varying neat dielectric constants (ɛ), viscosities (η), and glass transition temperatures (Tg), as hosts for lithium bistrifluoromethanesulfonimide (LiTFSI) salt. In such a context, it was demonstrated that the ionic conductivity of these polymer electrolytes was a function of ɛ rather than Tg or η, suggesting that there may exist regimes in which ionic conductivity is not limited by slow segmental dynamics but rather by low ionic dissociation. Motivated by such results, we used atomistic molecular dynamics to study the structure and transport characteristics of the same set of host polymers. We found that the coordination number of TFSI- about Li+ in the first solvation shell and the total fraction of free ions increased as a function of ɛ, implying the polymer hosts enhanced ion dissociation. In addition, we found that increasing the dielectric constant of the host polymer enhanced self-correlated ion transport, as evidenced by an increase in the diffusion coefficients of each ion species. Overall, we confirmed that limited ion dissociation in low- ɛ polymer electrolyte hosts hampers ionic conductivity. We would like to thank the National Science Foundation Graduate Research Fellowship Program for funding this research endeavor.

Injectable, degradable, electroactive nanocomposite hydrogels containing conductive polymer nanoparticles for biomedical applications

PubMed Central

Wang, Qinmei; Wang, Qiong; Teng, Wei

2016-01-01

Injectable electroactive hydrogels (eGels) are promising in regenerative medicine and drug delivery, however, it is still a challenge to obtain such hydrogels simultaneously possessing other properties including uniform structure, degradability, robustness, and biocompatibility. An emerging strategy to endow hydrogels with desirable properties is to incorporate functional nanoparticles in their network. Herein, we report the synthesis and characterization of an injectable hydrogel based on oxidized alginate (OA) crosslinking gelatin reinforced by electroactive tetraaniline-graft-OA nanoparticles (nEOAs), where nEOAs are expected to impart electroactivity besides reinforcement without significantly degrading the other properties of hydrogels. Assays of transmission electron microscopy, 1H nuclear magnetic resonance, and dynamic light scattering reveal that EOA can spontaneously and quickly self-assemble into robust nanoparticles in water, and this nanoparticle structure can be kept at pH 3~9. Measurement of the gel time by rheometer and the stir bar method confirms the formation of the eGels, and their gel time is dependent on the weight content of nEOAs. As expected, adding nEOAs to hydrogels does not cause the phase separation (scanning electron microscopy observation), but it improves mechanical strength up to ~8 kPa and conductivity up to ~10−6 S/cm in our studied range. Incubating eGels in phosphate-buffered saline leads to their further swelling with an increase of water content <6% and gradual degradation. When growing mesenchymal stem cells on eGels with nEOA content ≤14%, the growth curves and morphology of cells were found to be similar to that on tissue culture plastic; when implanting these eGels on a chick chorioallantoic membrane for 1 week, mild inflammation response appeared without any other structural changes, indicating their good in vitro and in vivo biocompatibility. With injectability, uniformity, degradability, electroactivity, relative robustness, and biocompatibility, these eGels may have a huge potential as scaffolds for tissue regeneration and matrix for stimuli responsive drug release. PMID:26792990

Multilayer polymer dielectric films for hollow glass waveguides

NASA Astrophysics Data System (ADS)

Kendall, Wesley; Harrington, James A.

2018-02-01

Hollow glass waveguides (HGWs) have been extensively investigated for the transmission of broadband, high-power radiation, particularly in the mid-infrared. One area of particular interest is the deposition of dielectric thin films within the hollow core of the HGW in order to reduce the losses at desired wavelengths. By implementing a thin film multilayer structure with high index mismatch between adjacent films, it is possible to dramatically improve the losses of the waveguides due to the thin film interference effect. Existing multilayer film research has utilized heavy metal halides, which although provide considerable index contrast, are toxic and unsuitable for clinical applications in which they are often used. Polymer dielectric thin films provide desirable optical properties for HGWs but are hindered by solvent compatibility in the deposition procedure. This work demonstrates implementation of a polymer multilayer dielectric thin film stack within a HGW, using ChemoursTM Teflon AF (n = 1.29) as the low-index material and polystyrene (n = 1.59) as the high-index material. These two polymers were deposited using liquid phase techniques within a HGW; the absorption spectra of waveguide as each layer was deposited on was analyzed in the mid-IR with an FTIR, and straight and bending losses were measured on a CO2 laser. Appreciable losses were realized with the addition of the second polymer film and the interference bands red-shifted with the second layer, suggesting the successful creation of the multilayer structure.

Dielectric performance of high permitivity nanocomposites: impact of polystyrene grafting on BaTiO 3 and TiO 2

DOE PAGES

Grabowski, Christopher A.; Fillery, Scott P.; Koerner, Hilmar; ...

2016-09-22

Polymer nanocomposites are a promising concept to improve energy storage density of capacitors, but realizing their hypothetical gains has proved challenging. The introduction of high permittivity fillers often leads to reduction in breakdown strength due to field exclusion, which intensifies the applied electric field within the polymer matrix near nanoparticle interfaces. This has prompted research in developing new nanoparticle functionalization chemistries and processing concepts to maximize particle separation. Herein, we compare the dielectric performance of blended nanocomposites to matrix free assemblies of hairy (polymer-grafted) nanoparticles (HNPs) that exhibit comparable overall morphology. The dielectric breakdown strength of polystyrene-grafted BaTiO3 (PS@BaTiO3) systemsmore » was over 40% greater than a blended nanocomposite with similar loading (~25% v/v BaTiO3). Hairy nanoparticles with TiO2 cores followed similar trends in breakdown strength as a function of inorganic loading up to 40% v/v. Dielectric loss for PS@BaTiO3 HNPs was 2-5 times lower than analogous blended films for a wide frequency spectrum (1 Hz to 100 kHz). For BaTiO3 content above 7% v/v, grafting the polymer chains to the nanoparticle significantly improved energy storage density and efficiency, likely due to the polymer canopy mitigating interfacial transport and restricting particle-particle hot-spots by establishing a finite minimum particle separation.« less

Dielectric performance of high permitivity nanocomposites: impact of polystyrene grafting on BaTiO 3 and TiO 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grabowski, Christopher A.; Fillery, Scott P.; Koerner, Hilmar

Polymer nanocomposites are a promising concept to improve energy storage density of capacitors, but realizing their hypothetical gains has proved challenging. The introduction of high permittivity fillers often leads to reduction in breakdown strength due to field exclusion, which intensifies the applied electric field within the polymer matrix near nanoparticle interfaces. This has prompted research in developing new nanoparticle functionalization chemistries and processing concepts to maximize particle separation. Herein, we compare the dielectric performance of blended nanocomposites to matrix free assemblies of hairy (polymer-grafted) nanoparticles (HNPs) that exhibit comparable overall morphology. The dielectric breakdown strength of polystyrene-grafted BaTiO3 (PS@BaTiO3) systemsmore » was over 40% greater than a blended nanocomposite with similar loading (~25% v/v BaTiO3). Hairy nanoparticles with TiO2 cores followed similar trends in breakdown strength as a function of inorganic loading up to 40% v/v. Dielectric loss for PS@BaTiO3 HNPs was 2-5 times lower than analogous blended films for a wide frequency spectrum (1 Hz to 100 kHz). For BaTiO3 content above 7% v/v, grafting the polymer chains to the nanoparticle significantly improved energy storage density and efficiency, likely due to the polymer canopy mitigating interfacial transport and restricting particle-particle hot-spots by establishing a finite minimum particle separation.« less

Synthesis, structural, characterization and dielectric spectroscopy of PVDF - BaTiO3 polymer composite

NASA Astrophysics Data System (ADS)

Kulkarni, S. S.; Belavi, P. B.; Khadke, U. V.

2018-05-01

In this paper we report the method of synthesis of ferroelectric polymer Polyvinyldene fluoride (PVDF) and Barium Titanate (BaTiO3) composite self supporting thin films and its dielectric response. BaTiO3 was synthesized by solid state reaction method. The PVDF - BaTiO3 polymer composites with various concentrations were synthesized by solution mixing method using Dimethylformadide (DMF) as a solvent. The phase transformation and surface methodology of the prepared composites were characterized by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) respectively. The XRD pattern confirms the formation of tetragonal pervoskite structure of ferroelectric phase. The XRD pattern shows the proper mixing of BaTiO3 particles intestinally and found to be improving its crystallinity with increase of BaTiO3 composition in the PVDF matrix. The dielectric properties of the composites as a function of frequency were computed using impedance analyzer. The dielectric constant decreases with increase of frequency shows the Maxwell - Wagner type of interfacial polarization in accordance with Koop's phenomenological theory.

Propulsion of swimming microrobots inspired by metachronal waves in ciliates: from biology to material specifications.

PubMed

Palagi, Stefano; Jager, Edwin W H; Mazzolai, Barbara; Beccai, Lucia

2013-12-01

The quest for swimming microrobots originates from possible applications in medicine, especially involving navigation in bodily fluids. Swimming microorganisms have become a source of inspiration because their propulsion mechanisms are effective in the low-Reynolds number regime. In this study, we address a propulsion mechanism inspired by metachronal waves, i.e. the spontaneous coordination of cilia leading to the fast swimming of ciliates. We analyse the biological mechanism (referring to its particular embodiment in Paramecium caudatum), and we investigate the contribution of its main features to the swimming performance, through a three-dimensional finite-elements model, in order to develop a simplified, yet effective artificial design. We propose a bioinspired propulsion mechanism for a swimming microrobot based on a continuous cylindrical electroactive surface exhibiting perpendicular wave deformations travelling longitudinally along its main axis. The simplified propulsion mechanism is conceived specifically for microrobots that embed a micro-actuation system capable of executing the bioinspired propulsion (self-propelled microrobots). Among the available electroactive polymers, we select polypyrrole as the possible actuation material and we assess it for this particular embodiment. The results are used to appoint target performance specifications for the development of improved or new electroactive materials to attain metachronal-waves-like propulsion.

Thermally stable, low dielectric polyquinolines for aerospace and electronics applications

NASA Technical Reports Server (NTRS)

Hendricks, Neil H.; Marrocco, Matthew L.; Stoakley, Diane M.; St. Clair, Anne K.

1990-01-01

Four new high molecular weight, linear chain polyquinolines have been synthesized and fabricated into high quality free standing films. These polymers are characterized by moderate to high glass transition temperatures, excellent thermal and thermooxidative stability, extremely low dielectric constants and good planarizing characteristics. The polymers absorb very low quantities of moisture. As a consequence, the dielectric constant of one new polyquinoline has been shown to be quite insensitive to exposure to warm/wet conditions. Isothermal aging of one new derivative in air has been carried out at elevated temperatures (250 C to 345 C). The results demonstrate truly outstanding thermooxidative stability. Additional characterizations include molecular weight determinations, solubilities and film-forming characteristics, density measurements, and UV-Vis spectroscopy. The data acquired to date suggest that the polymers may find use as refractive films and coatings and as interlevel planarizers in microelectronics applications.

Synthesis, characterization, and applications of electroactive polymeric nanostructures for organic coatings

NASA Astrophysics Data System (ADS)

Suryawanshi, Abhijit Jagnnath

Electroactive polymers (EAP) such as polypyrrole (PPy) and polyaniline (PANI) are being explored intensively in the scientific community. Nanostructures of EAPs have low dimensions and high surface area enabling them to be considered for various useful applications. These applications are in several fields including corrosion inhibition, capacitors, artificial muscles, solar cells, polymer light emitting diodes, and energy storage devices. Nanostructures of EAPs have been synthesized in different morphologies such as nanowires, nanorods, nanotubes, nanospheres, and nanocapsules. This variety in morphology is traditionally achieved using soft templates, such as surfactant micelles, or hard templates, such as anodized aluminum oxide (AAO). Templates provide stability and groundwork from which the polymer can grow, but the templates add undesirable expense to the process and can change the properties of the nanoparticles by integrating its own properties. In this study a template free method is introduced to synthesize EAP nanostructures of PPy and PANI utilizing ozone oxidation. The simple techniques involve ozone exposure to the monomer solution to produce aqueous dispersions of EAP nanostructures. The synthesized nanostructures exhibit uniform morphology, low particle size distribution, and stability against agglomeration. Ozone oxidation is further explored for the synthesis of silver-PPy (Ag-PPy) core-shell nanospheres (CSNs). Coatings containing PPy nanospheres were formulated to study the corrosion inhibition efficiency of PPy nanospheres. Investigation of the coatings using electrochemical techniques revealed that the PPy nanospheres may provide corrosion inhibition against filiform corrosion by oxygen scavenging mechanism. Finally, organic corrosion inhibitors were incorporated in PPy to develop efficient corrosion inhibiting systems, by using the synergistic effects from PPy and organic corrosion inhibitors.

Various design approaches to achieve electric field-driven segmented folding actuation of electroactive polymer (EAP) sheets

NASA Astrophysics Data System (ADS)

Ahmed, Saad; Hong, Jonathan; Zhang, Wei; Kopatz, Jessica; Ounaies, Zoubeida; Frecker, Mary

2018-03-01

Electroactive polymer (EAPs) based technologies have shown promise in areas such as artificial muscles, aerospace, medical and soft robotics. In this work, we demonstrate ways to harness on-demand segmented folding actuation from pure bending of relaxor-ferroelectric P(VDF-TrFE-CTFE) based films, using various design approaches, such as `stiffener' and `notch' based approaches. The in-plane actuation of the P(VDF-TrFE-CTFE) is converted into bending actuation using unimorph configurations, where one passive substrate layer is attached to the active polymer. First, we experimentally show that placement of thin metal strips as stiffener in between active EAPs and passive substrates leads to segmented actuation as opposed to pure bending actuation; stiffeners made of different materials, such as nickel, copper and aluminum, are studied which reveals that a higher Young's modulus favors more pronounced segmented actuation. Second, notched samples are prepared by mounting passive substrate patches of various materials on top of the passive layers of the unimorph EAP actuators. Effect of notch materials, size of the notches and position of the notches on the folding actuation are studied. The motion of the human finger inspires a finger-like biomimetic actuator, which is realized by assigning multiple notches on the structure; finite element analysis (FEA) is also performed using COMSOL Multiphysics software for the notched finger actuator. Finally, a versatile soft-gripper is developed using the notched approach to demonstrate the capability of a properly designed EAP actuator to hold objects of various sizes and shapes.

Weak-link capacitor

DOEpatents

Dirk, Shawn M [Albuquerque, NM; Johnson, Ross S [Albuquerque, NM; Wheeler, David R [Albuquerque, NM; Bogart, Gregory R [Corrales, NM

2011-06-07

A process for making a dielectric material where a precursor polymer selected from poly(phenylene vinylene) polyacetylene, poly(p-phenylene), poly(thienylene vinylene), poly(1,4-naphthylene vinylene), and poly(p-pyridine vinylene) is energized said by exposure by radiation or increase in temperature to a level sufficient to eliminate said leaving groups contained within the precursor polymer, thereby transforming the dielectric material into a conductive polymer. The leaving group in the precursor polymer can be a chloride, a bromide, an iodide, a fluoride, an ester, an xanthate, a nitrile, an amine, a nitro group, a carbonate, a dithiocarbamate, a sulfonium group, an oxonium group, an iodonium group, a pyridinium group, an ammonium group, a borate group, a borane group, a sulphinyl group, or a sulfonyl group.

Weak-link capacitor

DOEpatents

Dirk, Shawn M.; Johnson, Ross S.; Wheeler, David R.; Bogart, Gregory R.

2013-04-23

A process for making a dielectric material where a precursor polymer selected from poly(phenylene vinylene)polyacetylene, poly(p-phenylene), poly(thienylene vinylene), poly(1,4-naphthylene vinylene), and poly(p-pyridine vinylene) is energized said by exposure by radiation or increase in temperature to a level sufficient to eliminate said leaving groups contained within the precursor polymer, thereby transforming the dielectric material into a conductive polymer. The leaving group in the precursor polymer can be a chloride, a bromide, an iodide, a fluoride, an ester, an xanthate, a nitrile, an amine, a nitro group, a carbonate, a dithiocarbamate, a sulfonium group, an oxonium group, an iodonium group, a pyridinium group, an ammonium group, a borate group, a borane group, a sulphinyl group, or a sulfonyl group.

Free volume dependence on electrical properties of Poly (styrene co-acrylonitrile)/Nickel oxide polymer nanocomposites

NASA Astrophysics Data System (ADS)

Ningaraju, S.; Hegde, Vinayakaprasanna N.; Prakash, A. P. Gnana; Ravikumar, H. B.

2018-04-01

Polymer nanocomposites of Poly (styrene co-acrylonitrile)/Nickel Oxide (PSAN/NiO) have been prepared. The increased free volume sizes up to 0.4 wt% of NiO loading indicates overall reduction in packing density of polymer network. The decreased o-Ps lifetime (τ3) at higher concentration of NiO indicates improved interfacial interaction between the surface of NiO nanoparticles and side chain of PSAN polymer matrix. The increased AC/DC conductivity at lower wt% of NiO loading demonstrates increased number of electric charge carriers/mobile ions and their mobility. The increased dielectric constant and dielectric loss up to 0.4 wt% of NiO loading suggests the increased dipoles polarization.

Clustering effects in ionic polymers: Molecular dynamics simulations.

PubMed

Agrawal, Anupriya; Perahia, Dvora; Grest, Gary S

2015-08-01

Ionic clusters control the structure, dynamics, and transport in soft matter. Incorporating a small fraction of ionizable groups in polymers substantially reduces the mobility of the macromolecules in melts. These ionic groups often associate into random clusters in melts, where the distribution and morphology of the clusters impact the transport in these materials. Here, using molecular dynamic simulations we demonstrate a clear correlation between cluster size and morphology with the polymer mobility in melts of sulfonated polystyrene. We show that in low dielectric media ladderlike clusters that are lower in energy compared with spherical assemblies are formed. Reducing the electrostatic interactions by enhancing the dielectric constant leads to morphological transformation from ladderlike clusters to globular assemblies. Decrease in electrostatic interaction significantly enhances the mobility of the polymer.

Understanding the Effects of Defect Modification on the Structure and Properties of Fluorinated Polymers and Implications for Capacitive Energy Storage Technologies

NASA Astrophysics Data System (ADS)

Gadinski, Matthew R.

As the world begins to turn to alternative energy technologies and our electronic devices have become more both mobile and integral to everyday life, increasing interest has been focused on energy storage technologies. Capacitors are one of these energy storage technologies that utilize the polarization of an insulating material sandwiched by two electrodes as a means to store electric charge. Polymers are a preferred dielectric material for capacitors because of both their performance and practicality. However, polymer dielectrics are limited in energy density by low dielectric constant, and high loss at elevated temperature. This work aims to address these issues in order to enable polymer dielectrics for future applications and demands. As most polymer tend to have low dielectric constants (˜2-3), but impressive breakdown strengths, only a moderate improvement in dielectric constant has the potential to vastly improve the energy density of polymer capacitors. As such tremendous interest has been placed on poly(vinylidene fluoride) (PVDF) which has a dielectric of 10+ due to the highly polar C-F bonds of its backbone. To improve PVDF's performance defect monomers have been introduced to tailor the polymorphic crystalline phase to tune its properties. Additionally, this defect modification has implications for piezoelectric, electrocaloric, and thermoelectric applications of PVDF. In Chapter 2 a copolymer of VDF and bromotrifluoroethylene (BTFE) was produced. The effect of BTFE on the structure and dielectric properties of the resulting copolymer had not been previously evaluated, and its synthesis allowed for the comparison to previously reported VDF based copolymers including P(VDF-CTFE) and P(VDF-HFP). Through 19F NMR it was determined due to reactivity ratio differences of BTFE in comparison to previously explored copolymers, BTFE during synthesis is much more likely to link with itself. This results in long runs of BTFE-BTFE defects along with isolated single defects. These long runs are found to have dramatic effects on the distribution of chain conformations determined from FTIR, the melting temperature and total crystallinity determined by DSC, and the crystallite size, lattice spacing, and crystalline phase as determined by XRD. These results indicate that P(VDF-BTFE) has a mix of both included (single) and excluded defects (runs of defects) that rapidly inhibit crystallinity and alter phase. The dielectric analysis also confirmed this by a broadening of the Tg peak in the temperature dependent dielectric spectroscopy with increasing BTFE content in the monomer feed indicative of expansion of the interlamellar region due to defect exclusion. Chapter 3 explores P(VDF-BTFE) copolymers for capacitive energy storage. Due to the rapid decrease in crystallinity only low concentration copolymers (>2 mol %) BTFE were used. This was ultimately a result of stretching being required for high energy density to be exhibited. The 0.5 mol% BTFE copolymer samples was found to possess a discharge energy density of 20.8 J/cm 3 at 750 MV/m along with the highest breakdown strength of any reported PVDF based copolymer. It was found that for this small amount of defect monomer the gamma phase of PVDF was stabilized and mixed with beta phase and along with small crystallite size accounted for the high breakdown strength and energy density. Additionally, by utilizing only a small amount of defect monomer the decrease in crystallinity and melting temperature observed in previously examined PVDF copolymers was avoided. Chapter 4 examines a terpolymer of VDF, trifluoroethylene (TrFE), and chlorotrifluoroethylene (CTFE). The terpolymers of VDF have gained extensive interest as the use of the two defect monomer increases the dielectric constant to 40+ along with altering the polarization behavior from a normal ferroelectric to a relaxor ferroelectric characterized by a slim hysteresis loop. The current understanding of this behavior suggests that only the size of the third bulky monomer (CTFE in this case) determines whether a single hysteresis (SHL) or double hysteresis loop (DHL) will develop. This chapter shows that for a single composition of the terpolymer normal ferroelectric, SHL, and DHL behavior can be tuned through processing of the film. This was rationalized as films give long times to crystallize developed large ferroelectric domains within a paraelectric matrix resulting in the DHL behavior due to reversible switching of these domains. While if these films were stretched below the Tc SHL behavior was observed as this had the effect of dispersing these domains within the crystal. Chapter 5 changes focus to high temperature performance of polymer capacitors. The primary strategy to enable high temperature polymer capacitors has been the utilization of high Tg polymers because of their thermal stability. While these polymers have demonstrated stable dielectric properties at low field and high breakdown strengths at elevated temperatures, the high field loss limits their use at even mildly elevated temperature well below T g. Additionally, these polymers are expensive, brittle, and difficult to process, essentially defeating some of the primary reasons for utilizing a polymer in the first place. This chapter examines a commercially available, extrudable, high temperature fluoropolymer, known as polychlorotrifluoroethylene (PCTFE). The same defect monomer discussed with PVDF above. While this polymer showed comparable performance to BOPP at room temperature, it showed equally susceptible to high field loss at elevated temperature. However, the chlorine of the monomers allow for crosslinking of this polymer by commercially used peroxide/co-agent chemistry. Crosslinking lead to a substantial improvement of the crosslinked film over the pristine polymer, and superior energy density to the commercial high Tg polymers up to 150 °C. The reason for the improvement was found to be the formation of chemical defects produced during the crosslinking that were excluded from the crystalline phase. Through TSDC it was found that these defects concentrated in the interlamellar region led to a substantial enhancement of the charge trapping properties of this relaxation.

Actuator model of electrostrictive polymers (EPs) for microactuators

NASA Astrophysics Data System (ADS)

Kim, Hunmo; Oh, Sinjong; Hwang, Kyoil; Choi, Hyoukryeol; Jeon, Jaewook; Nam, Jaedo

2001-07-01

Recently, Electrostrictive polymers (EPs) are studied for micro-actuator, because of similarity of body tissue. Electrostrictive polymers (EPs) are based on the deformation of dielectric elastomer polymer in the presence of an electric field. Modeling of electrostrictive polymer has been studied, which is about voltage and displacement. And there are many parameters such as Young's modulus, voltage, thickness of EPs, pre-strain, dielectric, frequency and temperature which effect to movement of EPs. To do exact modeling, all parameters are included. In order to use as actuator, we accurately understood about the parameter that we refer above. And we have to execute modeling which parameters are considered. We used FEM in order to understand effects of parameters. Specially, because of pre-strain effects are very important, we derive the relations of stress and strain by using elastic strain energy.

Polymer/metal oxide hybrid dielectrics for low voltage field-effect transistors with solution-processed, high-mobility semiconductors

NASA Astrophysics Data System (ADS)

Held, Martin; Schießl, Stefan P.; Miehler, Dominik; Gannott, Florentina; Zaumseil, Jana

2015-08-01

Transistors for future flexible organic light-emitting diode (OLED) display backplanes should operate at low voltages and be able to sustain high currents over long times without degradation. Hence, high capacitance dielectrics with low surface trap densities are required that are compatible with solution-processable high-mobility semiconductors. Here, we combine poly(methyl methacrylate) (PMMA) and atomic layer deposition hafnium oxide (HfOx) into a bilayer hybrid dielectric for field-effect transistors with a donor-acceptor polymer (DPPT-TT) or single-walled carbon nanotubes (SWNTs) as the semiconductor and demonstrate substantially improved device performances for both. The ultra-thin PMMA layer ensures a low density of trap states at the semiconductor-dielectric interface while the metal oxide layer provides high capacitance, low gate leakage and superior barrier properties. Transistors with these thin (≤70 nm), high capacitance (100-300 nF/cm2) hybrid dielectrics enable low operating voltages (<5 V), balanced charge carrier mobilities and low threshold voltages. Moreover, the hybrid layers substantially improve the bias stress stability of the transistors compared to those with pure PMMA and HfOx dielectrics.

Investigation of ITO free transparent conducting polymer based electrode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, Vikas; Sapna,; Sachdev, Kanupriya

2016-05-23

The last few decades have seen a significant improvement in organic semiconductor technology related to solar cell, light emitting diode and display panels. The material and structure of the transparent electrode is one of the major concerns for superior performance of devices such as OPV, OLED, touch screen and LCD display. Commonly used ITO is now restricted due to scarcity of indium, its poor mechanical properties and rigidity, and mismatch of energy levels with the active layer. Nowadays DMD (dielectric-metal-dielectric) structure is one of the prominent candidates as alternatives to ITO based electrode. We have used solution based spin coatedmore » polymer layer as the dielectric layer with silver thin film embedded in between to make a polymer-metal-polymer (PMP) structure for TCE applications. The PMP structure shows low resistivity (2.3 x 10{sup −4}Ω-cm), high carrier concentration (2.9 x 10{sup 21} cm{sup −3}) and moderate transparency. The multilayer PMP structure is characterized with XRD, AFM and Hall measurement to prove its suitability for opto-electronic device applications.« less

Structure-property relationships in polymers for dielectric capacitors

NASA Astrophysics Data System (ADS)

Gupta, Sahil

Effective energy storage is a key challenge of the 21st century that has fueled research in the area of energy storage devices. In this dissertation, structure-property relationships have been evaluated for polymers that might be suitable for storing energy in high-energy density, high-temperature capacitors. Firstly, hydroxyl-modified polypropylenes (PPOH) were synthesized by copolymerization of the propylene and undecenyloxytrimethylsilane monomers. The presence of H-bonding in PPOH copolymers increased their glass-transition temperature. Steric hindrance by the comonomer reduced the PP crystal growth rate and crystal size, resulting in a melting point depression. The comonomer was restricted outside the crystalline domains leaving the alpha-monoclinic crystal structure of PP unaffected, but increasing the fold-surface free energy. Crystallization was slower for PPOH copolymers than PP, but exhibited a skewed bell curve as a function of hydroxyl concentration. H-bonding persisted even at melt temperatures up to 250°C resulting in a higher elasticity and viscosity for PPOH copolymers. Secondly, sulfonated poly(ether ether ketone) (HSPEEK) was synthesized by sulfonating PEEK with sulfuric acid, and further neutralized with Zn to obtain ZnSPEEK. The thermal and dielectric properties of SPEEK were compared with PEEK. The glass-transition increased and melting point were high enough to enable the use of polymer at 180°C. The incorporation of sulfonic groups in PEEK increased the dielectric constant. HSPEEK had a higher dielectric constant than ZnSPEEK due to higher dipolar mobility, but the dielectric loss was also higher for HSPEEK due to electrode polarization and DC conduction. These results were consistent with our observations from sulfonated polystyrene (HSPS), which was used as a >model&lang' polymer. Lastly, commercial poly(4-methyl-1-pentene) (P4MP) was characterized to check its viability as a high-temperature polymer dielectric. Thermal stability up to 200°C, high melting point (> 225°C) and melting onset at 160 - 190°C indicated that P4MP could be used at 180 - 200°C. Thin free-standing films (~10 mum) with controlled crystal structure and surface morphology were prepared using blade coating and their drying dynamics were measured using a custom-designed solvent-casting platform. These films were further stretched uniaxially or biaxially, and their effect on the dielectric properties of P4MP was studied.

Origin of dielectric relaxor behavior in PVDF-based copolymer and terpolymer films

NASA Astrophysics Data System (ADS)

Pramanick, Abhijit; Osti, Naresh C.; Jalarvo, Niina; Misture, Scott T.; Diallo, Souleymane Omar; Mamontov, Eugene; Luo, Y.; Keum, Jong-Kahk; Littrell, Ken

2018-04-01

Relaxor ferroelectrics exhibit frequency-dispersion of their dielectric permittivity peak as a function of temperature, the origin of which has been widely debated. Microscopic understanding of such behavior for polymeric ferroelectrics has presented new challenges since unlike traditional ceramic ferroelectrics, dielectric relaxation in polymers is a consequence of short-range molecular dynamics that are difficult to measure directly. Here, through careful analysis of atomic-level H-atom dynamics as determined by Quasi-elastic Neutron Scattering (QENS), we show that short-range molecular dynamics within crystalline domains cannot explain the macroscopic frequency-dispersion of dielectric properties observed in prototypical polyvinylidene-fluoride (PVDF)-based relaxor ferroelectrics. Instead, from multiscale quantitative microstructural characterization, a clear correlation between the amount of crystalline-amorphous interfaces and dielectric relaxation is observed, which indicates that such interfaces play a central role. These results provide critical insights into the role of atomic and microscopic structures towards relaxor behavior in ferroelectric polymers, which will be important for their future design.

Thermally stimulated depolarization currents and dielectric properties of Mg0.95Ca0.05TiO3 filled HDPE composites

NASA Astrophysics Data System (ADS)

Shi, Yunzhou; Zhang, Li; Zhang, Jie; Yue, Zhenxing

2017-12-01

Mg0.95Ca0.05TiO3 (MCT) filled high density polyethylene (HDPE) composites were prepared by twin-screw extrusion followed by hot pressing technique. The thermally stimulated depolarization current (TSDC) measurement was performed to analyze the contribution of charge distribution and interfacial characteristics to the dielectric loss. TSDC spectra under different polarization conditions show that the introduction of ceramic fillers engenders shallow traps in the vicinity of ceramic-polymer interface, which hinders the injection of space charge from the electrode into the polymer matrix. In the composite materials applied to an external field, charges tend to be captured by these traps. The temperature dependence of relative permittivity and dielectric loss of the composites was measured, and a strong reliance of dielectric loss on temperature was observed. In the heating process, the release of charges accumulating at interfacial region is considered to contribute to the rise in dielectric loss with the increase of temperature.

Fabrication of PVDF-TrFE based bilayered PbTiO{sub 3}/PVDF-TrFE films capacitor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nurbaya, Z., E-mail: nurbayazainal@gmail.com; Razak School of Engineering and Advanced Technology, Universiti Teknologi Malaysia, 54100 Kuala Lumpur; Wahid, M. H.

2016-07-06

Development of high performance capacitor is reaching towards new generation where the ferroelectric materials take places as the active dielectric layer. The motivation of this study is to produce high capacitance device with long life cycle. This was configured by preparing bilayered films where lead titanate as an active dielectric layer and stacked with the top dielectric layer, poly(vinyledenefluoride-trifluoroethylene). Both of them are being referred that have one in common which is ferroelectric behavior. Therefore the combination of ceramic and polymer ferroelectric material could perform optimum dielectric characteristic for capacitor applications. The fabrication was done by simple sol-gel spin coatingmore » method that being varied at spinning speed property for polymer layers, whereas maintaining the ceramic layer. The characterization of PVDF-TrFE/PbTiO3 was performed according to metal-insulator-metal stacked capacitor measurement which includes structural, dielectric, and ferroelectric measurement.« less

High energy density capacitors for low cost applications

NASA Astrophysics Data System (ADS)

Iyore, Omokhodion David

Polyvinylidene fluoride (PVDF) and its copolymers with trifluoroethylene, hexafluoropropylene and chlorotrifluoroethylene are the most widely investigated ferroelectric polymers, due to their relatively high electromechanical properties and potential to achieve high energy density. [Bauer, 2010; Zhou et al., 2009] The research community has focused primarily on melt pressed or extruded films of PVDF-based polymers to obtain the highest performance with energy density up to 25 Jcm-3. [Zhou et al., 2009] Solution processing offers an inexpensive, low temperature alternative, which is also easily integrated with flexible electronics. This dissertation focuses on the fabrication of solution-based polyvinylidene fluoride-hexafluoropropylene metal-insulator-metal capacitors on flexible substrates using a photolithographic process. Capacitors were optimized for maximum energy density, high dielectric strength and low leakage current density. It is demonstrated that with the right choice of solvent, electrodes, spin-casting and annealing conditions, high energy density thin film capacitors can be fabricated repeatably and reproducibly. The high electric field dielectric constants were measured and the reliabilities of the polymer capacitors were also evaluated via time-zero breakdown and time-dependent breakdown techniques. Chapter 1 develops the motivation for this work and provides a theoretical overview of dielectric materials, polarization, leakage current and dielectric breakdown. Chapter 2 is a literature review of polymer-based high energy density dielectrics and covers ferroelectric polymers, highlighting PVDF and some of its derivatives. Chapter 3 summarizes some preliminary experimental work and presents materials and electrical characterization that support the rationale for materials selection and process development. Chapter 4 discusses the fabrication of solution-processed PVDF-HFP and modification of its properties by photo-crosslinking. It is followed by a comparison of the structural, chemical and electrical properties of the neat and crosslinked films. Chapter 5 investigates the reliability and lifetime of PVDF-HFP thin films via time-zero and time-dependent dielectric breakdown. A power law relationship between the breakdown strength and characteristic breakdown time was determined, allowing extrapolation of lifetime at a desired operating voltage. The dissertation concludes with a summary and project outlook in chapter 7.

Dielectric, electric and thermal properties of carboxylic functionalized multiwalled carbon nanotubes impregnated polydimethylsiloxane nanocomposite

NASA Astrophysics Data System (ADS)

Sagar, Sadia; Iqbal, Nadeem; Maqsood, Asghari

2013-06-01

The dielectric, electric and thermal properties of carboxylic functionalized multiwalled carbon nanotubes (F-MWCNT) incorporated into the polydimethylsiloxane (PDMS) were evaluated to determine their potential in the field of electronic materials. Carboxylic functionalization of the pristine multi walled carbon tubes (Ps-MWCNT) was confirmed through Fourier transform infrared spectroscopy, X-ray diffraction patterns for both Ps-MWCNTs and F-MWCNTs elaborated that crystalline behavior did not change with carboxylic moieties. Thermogravimetric and differential thermal analyses were performed to elucidate the thermal stability with increasing weight % addition of F-MWCNTs in the polymer matrix. Crystallization/glass transition / melting temperatures were evaluated using differential scanning calorimeter and it was observed that glass transition and crystallization temperatures were diminished while temperatures of first and second melting transitions were progressed with increasing F-MWCNT concentration in the PDMS matrix. Scanning electron microscopy and energy dispersive x-ray spectroscopy were carried out to confirm the morphology, functionalization, and uniform dispersion of F-MWCNTs in the polymer matrix. Electrical resistivity at temperature range (100-300°C), dielectric loss (tanδ) and dielectric parameters (epsilon/ epsilon//) were measured in the frequency range (1MHz-3GHz). The measured data simulate that the aforementioned properties were influenced by increasing filler contents in the polymer matrix because of the high polarization of conductive F-MWCNTs at the reinforcement/polymer interface.

Silver-containing polymer composition used in spacecraft and semiconductor optoelectronics control systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ivanov, A. A., E-mail: alexchemtsu@rambler.ru; Tuev, V. I., E-mail: tvi-retem@main.tusur.ru

2015-10-27

The copolymer of the vinyl chloride-maleic anhydride and silver nano- and microparticle (70 wt %) composition is offered as a conductive adhesive for fixing various chips on the dielectric substrate. The wiring volume resistivity is up to 3.1×10{sup −8} Ohm×m. The adhesive strength of the silver-containing polymer composition (70% of Ag) applied under a shear on the dielectric substrate is 106 N/mm{sup 2}. Adhesive layers obtained from these substances have a high thermal conductivity up to λ = 199.93 W/m×K that depends on the amount of Ag in the polymer composition.

Castable three-dimensional stationary phase for electric field-driven applications

DOEpatents

Shepodd, Timothy J.; Whinnery, Jr., Leroy; Even, Jr., William R.

2005-01-25

A polymer material useful as the porous dielectric medium for microfluidic devices generally and electrokinetic pumps in particular. The polymer material is produced from an inverse (water-in-oil) emulsion that creates a 3-dimensional network characterized by small pores and high internal volume, characteristics that are particularly desirable for the dielectric medium for electrokinetic pumps. Further, the material can be cast-to-shape inside a microchannel. The use of bifunctional monomers provides for charge density within the polymer structure sufficient to support electroosmotic flow. The 3-dimensional polymeric material can also be covalently bound to the channel walls thereby making it suitable for high-pressure applications.

Castable three-dimensional stationary phase for electric field-driven applications

DOEpatents

Shepodd, Timothy J [Livermore, CA; Whinnery, Jr., Leroy; Even, Jr., William R.

2009-02-10

A polymer material useful as the porous dielectric medium for microfluidic devices generally and electrokinetic pumps in particular. The polymer material is produced from an inverse (water-in-oil) emulsion that creates a 3-dimensional network characterized by small pores and high internal volume, characteristics that are particularly desirable for the dielectric medium for electrokinetic pumps. Further, the material can be cast-to-shape inside a microchannel. The use of bifunctional monomers provides for charge density within the polymer structure sufficient to support electroosmotic flow. The 3-dimensional polymeric material can also be covalently bound to the channel walls thereby making it suitable for high-pressure applications.

Dielectric spectroscopy of PMMA-LiClO4 based polymer electrolyte plasticized with ethylene carbonate EC

NASA Astrophysics Data System (ADS)

Pal, P.; Ghosh, A.

2018-04-01

Dielectric spectroscopy covering the frequency range 0.01 Hz - 2 MHz for PMMA-LiClO4 based polymer electrolyte embedded with different concentration of ethylene carbonate (x = 0, 20 and 40 wt%) has been analyzed using Havrilliak-Negami formalism. The reciprocal temperature dependence of inverse relaxation time obtained from the analysis of dielectric spectra follows Vogel-Tammann-Fulcher behaviour. The shape parameters obtained from this analysis change with ethylene carbonate concentrations. From the fits of the experimental result using Kohlrausch-Williams-Watts function. We have obtained stretched exponent β which indicates that the relaxation is highly non-exponential. The decay function obtained from electric modulus data is highly asymmetric.

Molecular dynamics of oligofluorenes: A dielectric spectroscopy investigation

NASA Astrophysics Data System (ADS)

Papadopoulos, P.; Floudas, G.; Chi, C.; Wegner, G.

2004-02-01

The molecular dynamics were investigated in a series of "defect-free" oligofluorenes up to the polymer by dielectric spectroscopy (DS). The method is very sensitive to the presence of keto "defects" that when incorporated on the backbone give rise to poor optical and electronic properties. Two dielectrically active processes were found (β and α process). The latter process (α) displays strongly temperature dependent relaxation times and temperature- and molecular weight-dependent spectral broadening associated with intramolecular correlations. The glass temperature (Tg) obeys the Fox-Flory equation and the polymer Tg is obtained by DS at 332 K. The effective dipole moment associated with the α process is 0.27±0.03 D.

Filling in the voids of electrospun hydroxypropyl cellulose network: Dielectric investigations

NASA Astrophysics Data System (ADS)

Maximean, Doina Manaila; Danila, Octavian; Ganea, Constantin Paul; Almeida, Pedro L.

2018-04-01

Here we describe an organic electro-optic device, obtained using electrospun hydroxypropyl cellulose (HPC) polymer fibres and nematic liquid crystals (LC). Its working mechanism is similar to that of a classic polymer-dispersed liquid crystal (PDLC) device. The scanning electron microscopy of the HPC deposited fibres shows a mat of fibres with diameters in the nano and micron size range. Dielectric spectroscopy measurements allow the determination of the dependence of the dielectric constant and electric energy loss on frequency and temperature as well as the determination of the activation energy. The electro-optic study shows a very good optical transmission curve, with an "on"-"off" switching voltage of less than 1V/μ m.

Hysteresis mechanism and control in pentacene organic field-effect transistors with polymer dielectric

NASA Astrophysics Data System (ADS)

Huang, Wei; Shi, Wei; Han, Shijiao; Yu, Junsheng

2013-05-01

Hysteresis mechanism of pentacene organic field-effect transistors (OFETs) with polyvinyl alcohol (PVA) and/or polymethyl methacrylate (PMMA) dielectrics is studied. Through analyzing the electrical characteristics of OFETs with various PVA/PMMA arrangements, it shows that charge, which is trapped in PVA bulk and at the interface of pentacene/PVA, is one of the origins of hysteresis. The results also show that memory window is proportional to both trap amount in PVA and charge density at the gate/PVA or PVA/pentacene interfaces. Hence, the controllable memory window of around 0 ˜ 10 V can be realized by controlling the thickness and combination of triple-layer polymer dielectrics.

Production of atmospheric pressure microwave plasma with dielectric half-mirror resonator and its application to polymer surface treatment

NASA Astrophysics Data System (ADS)

Sasai, Kensuke; Keyamura, Kazuki; Suzuki, Haruka; Toyoda, Hirotaka

2018-06-01

For the surface treatment of a polymer tube, a ring-shaped atmospheric pressure microwave plasma (APMP) using a coaxial waveguide is studied. In this APMP, a dielectric plate is used not only as a partial mirror for cavity resonation but also for the precise alignment of the discharge gap for ring-shaped plasma production. The optimum position of the dielectric plate is investigated by electromagnetic wave simulation. On the basis of simulation results, a ring-shaped plasma with good uniformity along the ring is produced. The coaxial APMP is applied to the surface treatment of ethylene tetrafluoroethylene. A very fast surface modification within 3 s is observed.

Flory-type theories of polymer chains under different external stimuli

NASA Astrophysics Data System (ADS)

Budkov, Yu A.; Kiselev, M. G.

2018-01-01

In this Review, we present a critical analysis of various applications of the Flory-type theories to a theoretical description of the conformational behavior of single polymer chains in dilute polymer solutions under a few external stimuli. Different theoretical models of flexible polymer chains in the supercritical fluid are discussed and analysed. Different points of view on the conformational behavior of the polymer chain near the liquid-gas transition critical point of the solvent are presented. A theoretical description of the co-solvent-induced coil-globule transitions within the implicit-solvent-explicit-co-solvent models is discussed. Several explicit-solvent-explicit-co-solvent theoretical models of the coil-to-globule-to-coil transition of the polymer chain in a mixture of good solvents (co-nonsolvency) are analysed and compared with each other. Finally, a new theoretical model of the conformational behavior of the dielectric polymer chain under the external constant electric field in the dilute polymer solution with an explicit account for the many-body dipole correlations is discussed. The polymer chain collapse induced by many-body dipole correlations of monomers in the context of statistical thermodynamics of dielectric polymers is analysed.

Electrostatically assisted fabrication of silver-dielectric core/shell nanoparticles thin film capacitor with uniform metal nanoparticle distribution and controlled spacing.

PubMed

Li, Xue; Niitsoo, Olivia; Couzis, Alexander

2016-03-01

An electrostatically-assisted strategy for fabrication of thin film composite capacitors with controllable dielectric constant (k) has been developed. The capacitor is composed of metal-dielectric core/shell nanoparticle (silver/silica, Ag@SiO2) multilayer films, and a backfilling polymer. Compared with the simple metal particle-polymer mixtures where the metal nanoparticles (NP) are randomly dispersed in the polymer matrix, the metal volume fraction in our capacitor was significantly increased, owing to the densely packed NP multilayers formed by the electrostatically assisted assembly process. Moreover, the insulating layer of silica shell provides a potential barrier that reduces the tunneling current between neighboring Ag cores, endowing the core/shell nanocomposites with a stable and relatively high dielectric constant (k) and low dielectric loss (D). Our work also shows that the thickness of the SiO2 shell plays a dominant role in controlling the dielectric properties of the nanocomposites. Control over metal NP separation distance was realized not only by variation the shell thickness of the core/shell NPs but also by introducing a high k nanoparticle, barium strontium titanate (BST) of relatively smaller size (∼8nm) compared to 80-160nm of the core/shell Ag@SiO2 NPs. The BST assemble between the Ag@SiO2 and fill the void space between the closely packed core/shell NPs leading to significant enhancement of the dielectric constant. This electrostatically assisted assembly method is promising for generating multilayer films of a large variety of NPs over large areas at low cost. Copyright © 2015 Elsevier Inc. All rights reserved.

Broadband Dielectric Spectroscopy and Quasi-Elastic Neutron Scattering on Single-Ion Polymer Conductors

NASA Astrophysics Data System (ADS)

Soles, Christopher; Peng, Hua-Gen; Page, Kirt; Snyder, Chad; Pandy, Ashoutosh; Jeong, Youmi; Runt, James; NIST Collaboration; Pennsylvania Collaboration

2011-03-01

The application of solid polymer electrolytes in rechargeable batteries has not been fully realized after decades of research due to its low conductivity. Dramatic increases of the ion conductivity are needed and this progress requires the understanding of conduction mechanism. We address this topic in two fronts, namely, the effect of plasticizer additives and geometric confinement on the charge transfer mechanism. To this end, we combine broadband dielectric spectroscopy (BDS) to characterize the ion mobility and quasi-elastic neutron scattering (QENS) to quantify segmental motion on a single-ion model polymer electrolyte. Deuterated small molecules were used as plasticizers so that the segmental motion of the polymer electrolyte could be monitored by QENS to understand the mechanism behind the increased conductivity. Anodic aluminum oxide (AAO) membranes with well defined channel sizes are used as the matrix to study the transport of ions solvated in a 1D polymer electrolyte.

Structure, dielectric, thermal and I-V studies of electron beam irradiated PVDF-HFP/LiClO4 electrolyte film

NASA Astrophysics Data System (ADS)

Yesappa, L.; Niranjana, M.; Ashokkumar, S. P.; Vijeth, H.; Basappa, M.; Ganesh, S.; Devendrappa, H.

2018-05-01

The effect of electron beam (EB) irradiation on polymer electrolyte (PVDF-HFP: LiClO4=90:10, PHL10) films prepared by solution casting method. FT-IR confirms the complexation between salt and polymer upon EB dose. Degradation of polymer and decrease in % of crystallinity from 50.10 to 40.96 at 2θ=19.90° at 120 kGy dose indicates increased amorphousity confirmed by XRD. The TGA result show decrease in Tm from 460 °C to 418 °C is leads to degradation of polymer chain at higher dosage. The dielectric parameters have been determined and observed decreasing trend with increased frequency as well as temperature due to increase the mobility of charge carrier confirms the capacitive nature. I-V plots exhibit an ohmic behavior with applied voltage and irradiation dose. The results notice the change in polymer properties upon irradiation.

Clustering effects in ionic polymers: Molecular dynamics simulations

DOE PAGES

Agrawal, Anupriya; Perahia, Dvora; Grest, Gary S.

2015-08-18

Ionic clusters control the structure, dynamics, and transport in soft matter. Incorporating a small fraction of ionizable groups in polymers substantially reduces the mobility of the macromolecules in melts. Furthermore, these ionic groups often associate into random clusters in melts, where the distribution and morphology of the clusters impact the transport in these materials. Here, using molecular dynamic simulations we demonstrate a clear correlation between cluster size and morphology with the polymer mobility in melts of sulfonated polystyrene. We show that in low dielectric media ladderlike clusters that are lower in energy compared with spherical assemblies are formed. Reducing themore » electrostatic interactions by enhancing the dielectric constant leads to morphological transformation from ladderlike clusters to globular assemblies. Finally, decrease in electrostatic interaction significantly enhances the mobility of the polymer.« less

Composites Based on Core-Shell Structured HBCuPc@CNTs-Fe3O4 and Polyarylene Ether Nitriles with Excellent Dielectric and Mechanical Properties

NASA Astrophysics Data System (ADS)

Pu, Zejun; Zhong, Jiachun; Liu, Xiaobo

2017-10-01

Core-shell structured magnetic carbon nanotubes (CNTs-Fe3O4) coated with hyperbranched copper phthalocyanine (HBCuPc) (HBCuPc@CNTs-Fe3O4) hybrids were prepared by the solvent-thermal method. The results indicated that the HBCuPc molecules were decorated on the surface of CNTs-Fe3O4 through coordination behavior of phthalocyanines, and the CNTs-Fe3O4 core was completely coaxial wrapped by a functional intermediate HBCuPc shell. Then, polymer-based composites with a relatively high dielectric constant and low dielectric loss were fabricated by using core-shell structured HBCuPc@CNTs-Fe3O4 hybrids as fillers and polyarylene ether nitriles (PEN) as the polymer matrix. The cross-sectional scanning electron microscopy (SEM) images of composites showed that there is almost no agglomeration and internal delamination. In addition, the rheological analysis reveals that the core-shell structured HBCuPc@CNTs-Fe3O4 hybrids present better dispersion and stronger interface adhesion with the PEN matrix than CNTs-Fe3O4, thus resulting in significant improvement of the mechanical, thermal and dielectric properties of polymer-based composites.

On the nature of high field charge transport in reinforced silicone dielectrics: Experiment and simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Yanhui, E-mail: huangy12@rpi.edu; Schadler, Linda S.

The high field charge injection and transport properties in reinforced silicone dielectrics were investigated by measuring the time-dependent space charge distribution and the current under dc conditions up to the breakdown field and were compared with the properties of other dielectric polymers. It is argued that the energy and spatial distribution of localized electronic states are crucial in determining these properties for polymer dielectrics. Tunneling to localized states likely dominates the charge injection process. A transient transport regime arises due to the relaxation of charge carriers into deep traps at the energy band tails and is successfully verified by amore » Monte Carlo simulation using the multiple-hopping model. The charge carrier mobility is found to be highly heterogeneous due to the non-uniform trapping. The slow moving electron packet exhibits a negative field dependent drift velocity possibly due to the spatial disorder of traps.« less

Soft electroactive actuators and hard ratchet-wheels enable unidirectional locomotion of hybrid machine

NASA Astrophysics Data System (ADS)

Sun, Wenjie; Liu, Fan; Ma, Ziqi; Li, Chenghai; Zhou, Jinxiong

2017-01-01

Combining synergistically the muscle-like actuation of soft materials and load-carrying and locomotive capability of hard mechanical components results in hybrid soft machines that can exhibit specific functions. Here, we describe the design, fabrication, modeling and experiment of a hybrid soft machine enabled by marrying unidirectionally actuated dielectric elastomer (DE) membrane-spring system and ratchet wheels. Subjected to an applied voltage 8.2 kV at ramping velocity 820 V/s, the hybrid machine prototype exhibits monotonic uniaxial locomotion with an averaged velocity 0.5mm/s. The underlying physics and working mechanisms of the soft machine are verified and elucidated by finite element simulation.

Sequential growth for lifetime extension in biomimetic polypyrrole actuator systems

NASA Astrophysics Data System (ADS)

Sarrazin, J. C.; Mascaro, Stephen A.

2015-04-01

Electroactive polymers (EAPs) present prospective use in actuation and manipulation devices due to their low electrical activation requirements, biocompatibility, and mechanical performance. One of the main drawbacks with EAP actuators is a decrease in performance over extended periods of operation caused by over-oxidation of the polymer and general polymer degradation. Synthesis of the EAP material, polypyrrole with an embedded metal helix allows for sequential growth of the polymer during operation. The helical metal electrode acts as a scaffolding to support the polymer, and direct the 3-dimensional change in volume of the polymer along the axis of the helix during oxidative and reductive cycling. The metal helix also provides a working metal electrode through the entire length of the polymer actuator to distribute charge for actuation, as well as for sequential growth steps during the lifetime of operation of the polymer. This work demonstrates the method of sequential growth can be utilized after extended periods of use to partially restore electrical and mechanical performance of polypyrrole actuators. Since the actuation must be temporarily stopped to allow for a sequential growth cycle to be performed and reverse some of the polymer degradation, these actuator systems more closely mimic natural muscle in their analogous maintenance and repair.

Flexible Low-Mass Devices and Mechanisms Actuated by Electroactive Polymers

NASA Technical Reports Server (NTRS)

Bar-Cohen, Y; Leary, S.; Shahinpoor, M.; Harrison, J. O.; Smith, J.

1999-01-01

Miniature, lightweight, miser actuators that operate similar to biological muscles can be used to develop robotic devices with unmatched capabilities to impact many technology areas. Electroactive polymers (EAP) offer the potential to producing such actuators and their main attractive feature is their ability to induce relatively large bending or longitudinal strain. Generally, these materials produce a relatively low force and the applications that can be considered at the current state of the art are relatively limited. This reported study is concentrating on the development of effective EAPs and the resultant enabling mechanisms employing their unique characteristics. Several EAP driven mechanisms, which emulate human hand, were developed including a gripper, manipulator arm and surface wiper. The manipulator arm was made of a composite rod with an EAP actuator consisting of a scrolled rope that is activated longitudinally by an electrostatic field. A gripper was made to serve as an end effector and it consisted of multiple bending EAP fingers for grabbing and holding such objects as rocks. An EAP surface wiper was developed to operate like a human finger and to demonstrate the potential to remove dust from optical and IR windows as well as solar cells. These EAP driven devices are taking advantage of the large actuation displacement of these materials but there is need for a significantly greater actuation force capability.

A review of integrating electroactive polymers as responsive systems for specialized drug delivery applications.

PubMed

Pillay, Viness; Tsai, Tong-Sheng; Choonara, Yahya E; du Toit, Lisa C; Kumar, Pradeep; Modi, Girish; Naidoo, Dinesh; Tomar, Lomas K; Tyagi, Charu; Ndesendo, Valence M K

2014-06-01

Electroactive polymers (EAPs) are promising candidate materials for the design of drug delivery technologies, especially in conditions where an "on-off" drug release mechanism is required. To achieve this, EAPs such as polyaniline, polypyrrole, polythiophene, ethylene vinyl acetate, and polyethylene may be blended into responsive hydrogels in conjunction with the desired drug to obtain a patient-controlled drug release system. The "on-off" drug release mechanism can be achieved through the environmental-responsive nature of the interpenetrating hydrogel-EAP complex via (i) charged ions initiated diffusion of drug molecules; (ii) conformational changes that occur during redox switching of EAPs; or (iii) electroerosion. These release mechanisms are not exhaustive and new release mechanisms are still under investigation. Therefore, this review seeks to provide a concise incursion and critical overview of EAPs and responsive hydrogels as a strategy for advanced drug delivery, for example, controlled release of neurotransmitters, sulfosalicyclic acid from cross-linked hydrogel, and vaccine delivery. The review further discusses techniques such as linear sweep voltammetry, cyclic voltammetry, impedance spectroscopy, and chronoamperometry for the determination of the redox capability of EAPs. The future implications of the hydrogel-EAP composites include, but not limited to, application toward biosensors, DNA hybridizations, microsurgical tools, and miniature bioreactors and may be utilized to their full potential in the form of injectable devices as nanorobots or nanobiosensors. Copyright © 2013 Wiley Periodicals, Inc.

Bioelectrochemical control of neural cell development on conducting polymers.

PubMed

Collazos-Castro, Jorge E; Polo, José L; Hernández-Labrado, Gabriel R; Padial-Cañete, Vanesa; García-Rama, Concepción

2010-12-01

Electrically conducting polymers hold promise for developing advanced neuroprostheses, bionic systems and neural repair devices. Among them, poly(3, 4-ethylenedioxythiophene) doped with polystyrene sulfonate (PEDOT:PSS) exhibits superior physicochemical properties but biocompatibility issues have limited its use. We describe combinations of electrochemical and molecule self-assembling methods to consistently control neural cell development on PEDOT:PSS while maintaining very low interfacial impedance. Electro-adsorbed polylysine enabled long-term neuronal survival and growth on the nanostructured polymer. Neurite extension was strongly inhibited by an additional layer of PSS or heparin, which in turn could be either removed electrically or further coated with spermine to activate cell growth. Binding basic fibroblast growth factor (bFGF) to the heparin layer inhibited neurons but promoted proliferation and migration of precursor cells. This methodology may orchestrate neural cell behavior on electroactive polymers, thus improving cell/electrode communication in prosthetic devices and providing a platform for tissue repair strategies. Copyright © 2010 Elsevier Ltd. All rights reserved.

Fabrications and Applications of Stimulus-Responsive Polymer Films and Patterns on Surfaces: A Review

PubMed Central

Chen, Jem-Kun; Chang, Chi-Jung

2014-01-01

In the past two decades, we have witnessed significant progress in developing high performance stimuli-responsive polymeric materials. This review focuses on recent developments in the preparation and application of patterned stimuli-responsive polymers, including thermoresponsive layers, pH/ionic-responsive hydrogels, photo-responsive film, magnetically-responsive composites, electroactive composites, and solvent-responsive composites. Many important new applications for stimuli-responsive polymers lie in the field of nano- and micro-fabrication, where stimuli-responsive polymers are being established as important manipulation tools. Some techniques have been developed to selectively position organic molecules and then to obtain well-defined patterned substrates at the micrometer or submicrometer scale. Methods for patterning of stimuli-responsive hydrogels, including photolithography, electron beam lithography, scanning probe writing, and printing techniques (microcontact printing, ink-jet printing) were surveyed. We also surveyed the applications of nanostructured stimuli-responsive hydrogels, such as biotechnology (biological interfaces and purification of biomacromoles), switchable wettability, sensors (optical sensors, biosensors, chemical sensors), and actuators. PMID:28788489

Strain-dependent characterization of electrode and polymer network of electrically activated polymer actuators

NASA Astrophysics Data System (ADS)

Töpper, Tino; Osmani, Bekim; Weiss, Florian M.; Winterhalter, Carla; Wohlfender, Fabian; Leung, Vanessa; Müller, Bert

2015-04-01

Fecal incontinence describes the involuntary loss of bowel content and affects about 45 % of retirement home residents and overall more than 12 % of the adult population. Artificial sphincter implants for treating incontinence are currently based on mechanical systems with failure rates resulting in revision after three to five years. To overcome this drawback, artificial muscle sphincters based on bio-mimetic electro-active polymer (EAP) actuators are under development. Such implants require polymer films that are nanometer-thin, allowing actuation below 24 V, and electrodes that are stretchable, remaining conductive at strains of about 10 %. Strain-dependent resistivity measurements reveal an enhanced conductivity of 10 nm compared to 30 nm sputtered Au on silicone for strains higher than 5 %. Thus, strain-dependent morphology characterization with optical microscopy and atomic force microscopy could demonstrate these phenomena. Cantilever bending measurements are utilized to determine elastic/viscoelastic properties of the EAP films as well as their long-term actuation behavior. Controlling these properties enables the adjustment of growth parameters of nanometer-thin EAP actuators.

Multilevel organization in hybrid thin films for optoelectronic applications.

PubMed

Vohra, Varun; Bolognesi, Alberto; Calzaferri, Gion; Botta, Chiara

2009-10-20

In this work we report two simple approaches to prepare hybrid thin films displaying a high concentration of zeolite crystals that could be used as active layers in optoelectronic devices. In the first approach, in order to organize nanodimensional zeolite crystals of 40 nm diameter in an electroactive environment, we chemically modify their external surface and play on the hydrophilic/hydrophobic forces. We obtain inorganic nanocrystals that self-organize in honeycomb electroluminescent polymer structures obtained by breath figure formation. The different functionalizations of the zeolite surface result in different organizations inside the cavities of the polymeric structure. The second approach involving soft-litography techniques allows one to arrange single dye-loaded zeolite L crystals of 800 nm of length by mechanical loading into the nanocavities of a conjugated polymer. Both techniques result in the formation of thin hybrid films displaying three levels of organization: organization of the dye molecules inside the zeolite nanochannels, organization of the zeolite crystals inside the polymer cavities, and micro- or nanostructuration of the polymer.

Stiff, strong, yet tough free-standing dielectric films of graphene nanosheets-polyurethane nanocomposites with very high dielectric constant and loss

NASA Astrophysics Data System (ADS)

Jan, Rahim; Habib, Amir; Gul, Iftikhar Hussain

2016-01-01

In this study, graphene nanosheets (GNS) prepared through a liquid exfoliation technique are dispersed in thermoplastic polyurethane (TPU) at a volume fraction (Vf) of up to 0.19. Then, the electrical and mechanical properties of the obtained composites are characterized. The dielectric spectroscopy shows an excessive variation in dielectric constant (1.1 to 3.53 × 107) and dielectric tangent loss (0.03 to 2515) with varying Vf over the frequency range of 25 kHz to 5 MHz. A considerable enhancement in electrical conductivity (DC) is found, from 3.87 × 10-10 S/m (base polymer) to 53.5 S/m for the 0.19 Vf GNS-TPU nanocomposite. The GNS-TPU composites are mechanically robust, with a considerable increase in stiffness (˜4-fold) and strength (almost twice), maintaining its ductility up to 0.09 Vf GNS. The high dielectric constant at lower frequencies is attributed to the well-established Maxwell-Wagner polarization effect, whereas the high dielectric tangent loss is due to leakage currents as a physical conducting network is formed at high filler loadings. The layered structure, high aspect ratio, and improved dispersion of GNS are the main reasons for the improvement in both the dielectric characteristics and the mechanical properties of the host polymer. [Figure not available: see fulltext.

Ultra-high polarity ceramics induced extrinsic high permittivity of polymers contributing to high permittivity of 2-2 series composites

NASA Astrophysics Data System (ADS)

Feng, Yefeng; Zhang, Jianxiong; Hu, Jianbing; Peng, Cheng; He, Renqi

2018-01-01

Induced polarization at interface has been confirmed to have significant impact on the dielectric properties of 2-2 series composites bearing Si-based semi-conductor sheet and polymer layer. By compositing, the significantly elevated high permittivity in Si-based semi-conductor sheet should be responsible for the obtained high permittivity in composites. In that case, interface interaction could include two aspects namely a strong electrostatic force from high polarity polymeric layer and a newborn high polarity induced in Si-based ceramic sheet. In this work, this class of interface induced polarization was successfully extended into another 2-2 series composite system made up of ultra-high polarity ceramic sheet and high polarity polymer layer. By compositing, the greatly improved high permittivity in high polarity polymer layer was confirmed to strongly contribute to the high permittivity achieved in composites. In this case, interface interaction should consist of a rather large electrostatic force from ultra-high polarity ceramic sheet with ionic crystal structure and an enhanced high polarity induced in polymer layer based on a large polarizability of high polarity covalent dipoles in polymer. The dielectric and conductive properties of four designed 2-2 series composites and their components have been detailedly investigated. Increasing of polymer inborn polarity would lead to a significant elevating of polymer overall polarity in composite. Decline of inherent polarities in two components would result in a mild improving of polymer total polarity in composite. Introducing of non-polarity polymeric layer would give rise to a hardly unaltered polymer overall polarity in composite. The best 2-2 composite could possess a permittivity of ˜463 at 100 Hz 25.7 times of the original permittivity of polymer in it. This work might offer a facile route for achieving the promising composite dielectrics by constructing the 2-2 series samples from two high polarity components.

Ion-Containing Polymers: Ionomers.

ERIC Educational Resources Information Center

Bazuin, C. G.; Eisenberg, A.

1981-01-01

Demonstrates how the incorporation of relatively low amounts of ionic material into nonionic polymers affects the structure and properties of these polymers. The extent to which properties are altered depends on dielectric constant of the backbone, position and type of ionic group, counterion type, ion concentration, and degree of neutralization.…

A Comprehensive Study on Dielectric Properties of Volcanic Rock/PANI Composites

NASA Astrophysics Data System (ADS)

Kiliç, M.; Karabul, Y.; Okutan, M.; İçelli, O.

2016-05-01

Basalt is a very well-known volcanic rock that is dark colored and relatively rich in iron and magnesium, almost located each country in the world. These rocks have been used in the refused rock industry, to produce building tiles, construction industrial, highway engineering. Powders and fibers of basalt rocks are widely used of radiation shielding, thermal stability, heat and sound insulation. This study examined three different basalt samples (coded CM-1, KYZ-13 and KYZ-24) collected from different regions of Van province in Turkey. Polyaniline (PANI) is one of the representative conductive polymers due to its fine environmental stability, huge electrical conductivity, as well as a comparatively low cost. Also, the electrical and thermal properties of polymer composites containing PANI have been widely studied. The dielectric properties of Basalt/Polyaniline composites in different concentrations (10, 25, 50 wt.% PANI) have been investigated by dielectric spectroscopy method at the room temperature. The dielectric parameters (dielectric constants, loss and strength) were measured in the frequency range of 102 Hz-106 Hz at room temperature. The electrical mechanism change with PANI dopant. A detailed dielectrically analysis of these composites will be presented.

High-speed droplet actuation on single-plate electrode arrays.

PubMed

Banerjee, Arghya Narayan; Qian, Shizhi; Joo, Sang Woo

2011-10-15

This paper reports a droplet-based microfluidic device composed of patterned co-planar electrodes in an all-in-a-single-plate arrangement and coated with dielectric layers for electrowetting-on-dielectric (EWOD) actuation of discrete droplets. The co-planar arrangement is preferred over conventional two-plate electrowetting devices because it provides simpler manufacturing process, reduced viscous drag, and easier liquid-handling procedures. These advantages lead to more versatile and efficient microfluidic devices capable of generating higher droplet speed and can incorporate various other droplet manipulation functions into the system for biological, sensing, and other microfluidic applications. We have designed, fabricated, and tested the devices using an insulating layer with materials having relatively high dielectric constant (SiO(2)) and compared the results with polymer coatings (Cytop) with low dielectric constant. Results show that the device with high dielectric layer generates more reproducible droplet transfer over a longer distance with a 25% reduction in the actuation voltage with respect to the polymer coatings, leading to more energy efficient microfluidic applications. We can generate droplet speeds as high as 26 cm/s using materials with high dielectric constant such as SiO(2). Copyright © 2011. Published by Elsevier Inc.

Rationally designed polyimides for high-energy density capacitor applications.

PubMed

Ma, Rui; Baldwin, Aaron F; Wang, Chenchen; Offenbach, Ido; Cakmak, Mukerrem; Ramprasad, Rampi; Sotzing, Gregory A

2014-07-09

Development of new dielectric materials is of great importance for a wide range of applications for modern electronics and electrical power systems. The state-of-the-art polymer dielectric is a biaxially oriented polypropylene (BOPP) film having a maximal energy density of 5 J/cm(3) and a high breakdown field of 700 MV/m, but with a limited dielectric constant (∼2.2) and a reduced breakdown strength above 85 °C. Great effort has been put into exploring other materials to fulfill the demand of continuous miniaturization and improved functionality. In this work, a series of polyimides were investigated as potential polymer materials for this application. Polyimide with high dielectric constants of up to 7.8 that exhibits low dissipation factors (<1%) and high energy density around 15 J/cm(3), which is 3 times that of BOPP, was prepared. Our syntheses were guided by high-throughput density functional theory calculations for rational design in terms of a high dielectric constant and band gap. Correlations of experimental and theoretical results through judicious variations of polyimide structures allowed for a clear demonstration of the relationship between chemical functionalities and dielectric properties.

Polymer/metal oxide hybrid dielectrics for low voltage field-effect transistors with solution-processed, high-mobility semiconductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Held, Martin; Schießl, Stefan P.; Gannott, Florentina

Transistors for future flexible organic light-emitting diode (OLED) display backplanes should operate at low voltages and be able to sustain high currents over long times without degradation. Hence, high capacitance dielectrics with low surface trap densities are required that are compatible with solution-processable high-mobility semiconductors. Here, we combine poly(methyl methacrylate) (PMMA) and atomic layer deposition hafnium oxide (HfO{sub x}) into a bilayer hybrid dielectric for field-effect transistors with a donor-acceptor polymer (DPPT-TT) or single-walled carbon nanotubes (SWNTs) as the semiconductor and demonstrate substantially improved device performances for both. The ultra-thin PMMA layer ensures a low density of trap states atmore » the semiconductor-dielectric interface while the metal oxide layer provides high capacitance, low gate leakage and superior barrier properties. Transistors with these thin (≤70 nm), high capacitance (100–300 nF/cm{sup 2}) hybrid dielectrics enable low operating voltages (<5 V), balanced charge carrier mobilities and low threshold voltages. Moreover, the hybrid layers substantially improve the bias stress stability of the transistors compared to those with pure PMMA and HfO{sub x} dielectrics.« less

Temperature dependent dielectric properties and ion transportation in solid polymer electrolyte for lithium ion batteries

NASA Astrophysics Data System (ADS)

Sengwa, R. J.; Dhatarwal, Priyanka; Choudhary, Shobhna

2016-05-01

Solid polymer electrolyte (SPE) film consisted of poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA) blend matrix with lithium tetrafluroborate (LiBF4) as dopant ionic salt and poly(ethylene glycol) (PEG) as plasticizer has been prepared by solution casting method followed by melt pressing. Dielectric properties and ionic conductivity of the SPE film at different temperatures have been determined by dielectric relaxation spectroscopy. It has been observed that the dc ionic conductivity of the SPE film increases with increase of temperature and also the decrease of relaxation time. The temperature dependent relaxation time and ionic conductivity values of the electrolyte are governed by the Arrhenius relation. Correlation observed between dc conductivity and relaxation time confirms that ion transportation occurs with polymer chain segmental dynamics through hopping mechanism. The room temperature ionic conductivity is found to be 4 × 10-6 S cm-1 which suggests the suitability of the SPE film for rechargeable lithium batteries.

Temperature dependent dielectric properties and ion transportation in solid polymer electrolyte for lithium ion batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sengwa, R. J., E-mail: rjsengwa@rediffmail.com; Dhatarwal, Priyanka, E-mail: dhatarwalpriyanka@gmail.com; Choudhary, Shobhna, E-mail: shobhnachoudhary@rediffmail.com

2016-05-06

Solid polymer electrolyte (SPE) film consisted of poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA) blend matrix with lithium tetrafluroborate (LiBF{sub 4}) as dopant ionic salt and poly(ethylene glycol) (PEG) as plasticizer has been prepared by solution casting method followed by melt pressing. Dielectric properties and ionic conductivity of the SPE film at different temperatures have been determined by dielectric relaxation spectroscopy. It has been observed that the dc ionic conductivity of the SPE film increases with increase of temperature and also the decrease of relaxation time. The temperature dependent relaxation time and ionic conductivity values of the electrolyte are governedmore » by the Arrhenius relation. Correlation observed between dc conductivity and relaxation time confirms that ion transportation occurs with polymer chain segmental dynamics through hopping mechanism. The room temperature ionic conductivity is found to be 4 × 10{sup −6} S cm{sup −1} which suggests the suitability of the SPE film for rechargeable lithium batteries.« less

High-Temperature Capacitor Polymer Films

NASA Astrophysics Data System (ADS)

Tan, Daniel; Zhang, Lili; Chen, Qin; Irwin, Patricia

2014-12-01

Film capacitor technology has been under development for over half a century to meet various applications such as direct-current link capacitors for transportation, converters/inverters for power electronics, controls for deep well drilling of oil and gas, direct energy weapons for military use, and high-frequency coupling circuitry. The biaxially oriented polypropylene film capacitor remains the state-of-the-art technology; however, it is not able to meet increasing demand for high-temperature (>125°C) applications. A number of dielectric materials capable of operating at high temperatures (>140°C) have attracted investigation, and their modifications are being pursued to achieve higher volumetric efficiency as well. This paper highlights the status of polymer dielectric film development and its feasibility for capacitor applications. High-temperature polymers such as polyetherimide (PEI), polyimide, and polyetheretherketone were the focus of our studies. PEI film was found to be the preferred choice for high-temperature film capacitor development due to its thermal stability, dielectric properties, and scalability.

PREFACE: Dielectrics 2009: Measurement Analysis and Applications

NASA Astrophysics Data System (ADS)

Vaughan, Alun; Williams, Graham

2009-07-01

The conference Dielectrics 2009: Measurements, Analysis and Applications represents a significant milestone in the evolution of dielectrics research in the UK. It is reasonable to state that the academic study of dielectrics has led to many fundamental advances and that dielectric materials underpin the modern world in devices ranging from field effect transistors, which operate at extremely high fields, albeit low voltages, to the high voltage plants that provide the energy that powers our economy. The origins of the Dielectrics Group of the Institute of Physics (IOP), which organized this conference, can be traced directly back to the early 1960s, when Professor Mansel Davies was conducting research into the dielectric relaxation behaviour of polar liquids and solids at The Edward Davies Chemical Laboratories of the University College of Wales, Aberystwyth. He was already well-known internationally for his studies of molecular structure and bonding of small molecules, using infra-red-spectroscopy, and of the physical properties of hydrogen-bonded liquids and solids, using thermodynamic methods. Dielectric spectroscopy was a fairly new area for him and he realized that opportunities for scientists in the UK to gather together and discuss their research in this developing area of physical chemistry/chemical physics were very limited. He conceived the idea of forming a Dielectrics Discussion Group (DDG), which would act as a meeting point and provide a platform for dielectrics research in the UK and beyond and, as a result, a two-day Meeting was convened in the spring of 1968 at Gregynog Hall of the University of Wales, near Newtown, Montgomeryshire. It was organized by Mansel Davies, Alun Price and Graham Williams, all physical chemists from the UCW, Aberystwyth. Fifty scientists attended, being a mix of physical chemists, theoretical chemists, physicists, electrical engineers, polymer and materials scientists, all from the UK, except Dr Brendan Scaife of Trinity College, Dublin. The Meeting discussed dielectric relaxation behaviour arising from molecular motions of dipolar molecules in the liquid and elastomeric states (now known as soft condensed matter) with measurements spanning a frequency range from a few Hz, through power and radiofrequencies, UHF and VHF, the microwave range and into the far infra-red. As a result of its success, it was decided at the Meeting that a continuing Dielectrics Discussion Group would be established to meet not more frequently than once a year. It was appreciated at the time that the subject of 'Dielectrics' covered many sub-areas, broadly classified into those of polarization, relaxation, conduction and high-field phenomena. For the DDG, a solution was to run annual meetings on chosen themes in dielectrics research, where the theme would change from one meeting to the next. Topics addressed in the early years of the DDG included high field phenomena and impurity effects, heterogeneous systems and biomaterials, polarization and conduction and non-linear dielectrics and ferroelectrics. The number of participants at these early meetings grew from 50 to the low 100's, which reflected both the increased awareness of the Group and increased participation from researchers in Continental Europe. However, the majority of participants in this period were from the UK, which reflected the considerable activities in dielectrics research in University, Industry and Government laboratories in the UK. There followed a series of DDG Meetings until 1974, at which point, the DDG became a registered charity: The Dielectrics Society. Many of the earlier meetings were held in the attractive and convenient venues of Oxford and Cambridge colleges but, in the early 1990's, a new venue for the meetings was established at the University of Kent at Canterbury. In 2001, the next major change occurred when The Dielectrics Society was incorporated into the Institute of Physics, becoming their Dielectrics Group. From 1968 to 2001 the Annual Meetings focused on numerous topics, including relaxation and conduction processes in liquids, solids, liquid crystals, synthetic polymers and biopolymers, piezoelectric materials, electrets and ferroelectrets, interfacial phenomena, high field conduction and breakdown phenomena in solids, liquids and gases and, importantly, the remarkable developments in dielectric instrumentation during this period. These activities reflected the need, and willingness, to move dielectrics researches with the times. As examples of the variety and diversity of these meetings we may refer briefly to the 1981, 1989 and 1996 Meetings. The 1981 Oxford Meeting on High Field Phenomena in Dielectrics included strong themes on fundamental and practical effects of high E-fields on the dielectric and conduction behaviour of liquids and solids, electrical treeing and dielectric breakdown, non-linear dielectric effects, electrets, thin-film devices and electro-rheology. The late 1980's had seen large initiatives in the UK and globally in the general area of Molecular Electronics so, in timely fashion, this was the subject of the 1989 Meeting in Bangor. The 1996 Smart Dielectrics Meeting at Canterbury reported subsequent advances in designer materials having electro-responsive and electro-optical properties. The programme concerned electro- and photo-active materials, mainly organic, in the form of polar dielectrics, polyelectrolytes, organic semi- and photo-conductors, photo-refractive polymer films, organic ferroelectric films, liquid crystalline polymer films, piezo- and pyro-electric polymer films, electroluminescent polymers, electro-rheological fluids and non-linear optical polymer films as described by leading international scientists. The physico-chemical functions of the materials were demonstrated and interpreted in terms of fundamental molecular properties. An Archive, containing full details of all the Meetings of the DDG and the Dielectrics Society, has been placed on the Website of the IOP Dielectrics Group by Professor John Fothergill. The 2009 meeting of The Dielectrics Group of the IOP at Reading was therefore held to celebrate 40 years of coordinated dielectrics research activity in the UK and beyond, as presented at these DDG and Dielectrics Society Meetings. To reflect the range of topics addressed since the first DDG meeting in 1968, the organizing committee chose to break away from the tradition of a strongly- themed event and, rather, adopted a general, inclusive approach, albeit based upon four broad technical areas: Theme 1: Molecular and bulk relaxation processes Theme 2: Space charge and charge transport in insulators Theme 3: Functional materials Theme 4: Bio-dielectrics and complex systems. The result was a highly successful conference that attracted some 90 delegates from 11 countries, giving the event a truly international flavour, and which included both regular and new attendees. Consequently, the organizing committee would like to thank, our colleagues at the IOP, the invited speakers, our sponsors at National Grid, EDF Energy and Dow Wire and Cables and all the delegates for making the event such a success. Professor Alun Vaughan, Professor Graham Williams

Electroactive polymer (EAP) actuators for planetary applications

NASA Astrophysics Data System (ADS)

Bar-Cohen, Yoseph; Leary, Sean P.; Shahinpoor, Mohsen; Harrison, Joycelyn S.; Smith, J.

1999-05-01

NASA is seeking to reduce the mass, size, consumed power, and cost of the instrumentation used in its future missions. An important element of many instruments and devices is the actuation mechanism and electroactive polymers (EAP) are offering an effective alternative to current actuators. In this study, two families of EAP materials were investigated, including bending ionomers and longitudinal electrostatically driven elastomers. These materials were demonstrated to effectively actuate manipulation devices and their performance is being enhanced in this on-going study. The recent observations are reported in this paper, include the operation of the bending-EAP at conditions that exceed the harsh environment on Mars, and identify the obstacles that its properties and characteristics are posing to using them as actuators. Analysis of the electrical characteristics of the ionomer EAP showed that it is a current driven material rather than voltage driven and the conductivity distribution on the surface of the material greatly influences the bending performance. An accurate equivalent circuit modeling of the ionomer EAP performance is essential for the design of effective drive electronics. The ionomer main limitations are the fact that it needs to be moist continuously and the process of electrolysis that takes place during activation. An effective coating technique using a sprayed polymer was developed extending its operation in air from a few minutes to about four months. The coating technique effectively forms the equivalent of a skin to protect the moisture content of the ionomer. In parallel to the development of the bending EAP, the development of computer control of actuated longitudinal EAP has been pursued. An EAP driven miniature robotic arm was constructed and it is controlled by a MATLAB code to drop and lift the arm and close and open EAP fingers of a 4-finger gripper.

Modeling and control of a self-sensing polymer metal composite actuator

NASA Astrophysics Data System (ADS)

Nam, Doan Ngoc Chi; Ahn, Kyoung Kwan

2014-02-01

An ion polymer metal composite (IPMC) is an electro-active polymer (EAP) that bends in response to a small applied electrical field as a result of mobility of cations in the polymer network and vice versa. One drawback in the use of an IPMC is the sensing problem for such a small size actuator. The aim of this paper is to develop a physical model for a self-sensing IPMC actuator and to verify its applicability for practical position control. Firstly, ion dynamics inside a polymer membrane is investigated with an asymmetric solution in the presence of distributed surface resistance. Based on this analysis, a modified equivalent circuit and a simple configuration to realize the self-sensing IPMC actuator are proposed. Mathematical modelling and experimental evaluation indicate that the bending curvature can be obtained accurately using several feedback voltage signals along with the IPMC length. Finally, the controllability of the developed self-sensing IPMC actuator is investigated using a robust position control. Experimental results prove that the self-sensing characteristics can be applied in engineering control problems to provide a more convenient sensing method for IPMC actuating systems.

Reversible modulation of the redox activity in conducting polymer nanofilms induced by hydrophobic collapse of a surface-grafted polyelectrolyte.

PubMed

Fenoy, Gonzalo E; Giussi, Juan M; von Bilderling, Catalina; Maza, Eliana M; Pietrasanta, Lía I; Knoll, Wolfgang; Marmisollé, Waldemar A; Azzaroni, Omar

2018-05-15

We present the covalent modification of a Pani-like conducting polymer (polyaminobenzylamine, PABA) by grafting of a polyelectrolyte brush (poly [2-(methacryloyloxy)-ethyl-trimethylammonium chloride], PMETAC). As PABA has extra pendant amino moieties, the grafting procedure does not affect the backbone nitrogen atoms that are implicated in the electronic structure of the conducting polymers. Moreover, perchlorate anions interact very strongly with the quaternary ammonium pendant groups of PMETAC through ion pairing. Therefore, the grafting does not only keep the electroactivity of PABA in aqueous solutions but it adds the ion-actuation properties of the PMETAC brush to the modified electrode as demonstrated by contact angle measurements and electrochemical methods. In this way, the conjugation of the electron transfer properties of the conducting polymer with the anion responsiveness of the integrated brush renders perchlorate actuation of the electrochemical response. These results constitute a rational integration of nanometer-sized polymer building blocks that yields synergism of functionalities and illustrate the potentialities of nanoarchitectonics for pushing the limits of soft material science into the nanoworld. Copyright © 2018 Elsevier Inc. All rights reserved.

Modification of Optical, Structural and Dielectric Properties of MeV Ions Irradiated PS/Cu Nanocomposites.

PubMed

Gavade, Chaitali; Singh, N L; Khanna, P K; Shah, Sunil

2015-12-01

In order to study structural, thermal, optical and dielectric behaviors of composites, the films of Cu/polystyrene nanocomposites were synthesized at different concentrations of Cu-nanoparticles. These polymer nanocomposites were irradiated with carbon (85 MeV) and silicon (120 MeV) ions at different fluences. The samples were characterized using different techniques viz: X-ray diffraction, UV-visible spectroscopy, differential scanning calorimetry, and impedance gain phase analyzer. A noticeable increase in the intensity of X-ray diffraction peaks was observed after irradiation with 120 MeV Si-ions, which may be attributed to radiation-induced cross-linking in polymer. Optical properties like band gap was estimated for pure polymer and nanocomposite films from their optical absorption spectra in the wavelength region 200-800 nm. It was found that the band gap value shifted to lower energy (from 4.38 eV to 3.40 eV) on doping with silver nanoparticles and also upon irradiation. Differential scanning calorimetry analysis revealed an increase in the glass transition temperature upon irradiation, which may be attributed to cross linking of polymer chain due to ion beam irradiation which is also corroborated with XRD analysis. Dependence of dielectric properties on frequency, ions and filler concentration was studied. The results revealed the enhancement in dielectric properties after doping nanoparticles and also upon irradiation. It was observed that the effect of Si-beam is more effectual than the C-beam because of large electronic energy loss of heavy ion.

Directed Self-Assembly of Block Copolymers for High Breakdown Strength Polymer Film Capacitors.

PubMed

Samant, Saumil P; Grabowski, Christopher A; Kisslinger, Kim; Yager, Kevin G; Yuan, Guangcui; Satija, Sushil K; Durstock, Michael F; Raghavan, Dharmaraj; Karim, Alamgir

2016-03-01

Emerging needs for fast charge/discharge yet high-power, lightweight, and flexible electronics requires the use of polymer-film-based solid-state capacitors with high energy densities. Fast charge/discharge rates of film capacitors on the order of microseconds are not achievable with slower charging conventional batteries, supercapacitors and related hybrid technologies. However, the current energy densities of polymer film capacitors fall short of rising demand, and could be significantly enhanced by increasing the breakdown strength (EBD) and dielectric permittivity (εr) of the polymer films. Co-extruded two-homopolymer component multilayered films have demonstrated much promise in this regard showing higher EBD over that of component polymers. Multilayered films can also help incorporate functional features besides energy storage, such as enhanced optical, mechanical, thermal and barrier properties. In this work, we report accomplishing multilayer, multicomponent block copolymer dielectric films (BCDF) with soft-shear driven highly oriented self-assembled lamellar diblock copolymers (BCP) as a novel application of this important class of self-assembling materials. Results of a model PS-b-PMMA system show ∼50% enhancement in EBD of self-assembled multilayer lamellar BCP films compared to unordered as-cast films, indicating that the breakdown is highly sensitive to the nanostructure of the BCP. The enhancement in EBD is attributed to the "barrier effect", where the multiple interfaces between the lamellae block components act as barriers to the dielectric breakdown through the film. The increase in EBD corresponds to more than doubling the energy storage capacity using a straightforward directed self-assembly strategy. This approach opens a new nanomaterial paradigm for designing high energy density dielectric materials.

Directed self-assembly of block copolymers for high breakdown strength polymer film capacitors

DOE PAGES

Samant, Saumil P.; Grabowski, Christopher A.; Kisslinger, Kim; ...

2016-03-04

Emerging needs for fast charge/discharge yet high-power, lightweight, and flexible electronics requires the use of polymer-film-based solid-state capacitors with high energy densities. Fast charge/discharge rates of film capacitors on the order of microseconds are not achievable with slower charging conventional batteries, supercapacitors and related hybrid technologies. However, the current energy densities of polymer film capacitors fall short of rising demand, and could be significantly enhanced by increasing the breakdown strength (E BD) and dielectric permittivity (ε r) of the polymer films. Co-extruded two-homopolymer component multilayered films have demonstrated much promise in this regard showing higher E BD over that ofmore » component polymers. Multilayered films can also help incorporate functional features besides energy storage, such as enhanced optical, mechanical, thermal and barrier properties. In this work, we report accomplishing multilayer, multicomponent block copolymer dielectric films (BCDF) with soft-shear driven highly oriented self-assembled lamellar diblock copolymers (BCP) as a novel application of this important class of self-assembling materials. Results of a model PS- b-PMMA system show ~50% enhancement in E BD of self-assembled multilayer lamellar BCP films compared to unordered as-cast films, indicating that the breakdown is highly sensitive to the nanostructure of the BCP. The enhancement in E BD is attributed to the “barrier effect”, where the multiple interfaces between the lamellae block components act as barriers to the dielectric breakdown through the film. The increase in E BD corresponds to more than doubling the energy storage capacity using a straightforward directed self-assembly strategy. Lastly, this approach opens a new nanomaterial paradigm for designing high energy density dielectric materials.« less

Paper Actuators Made with Cellulose and Hybrid Materials

PubMed Central

Kim, Jaehwan; Yun, Sungryul; Mahadeva, Suresha K.; Yun, Kiju; Yang, Sang Yeol; Maniruzzaman, Mohammad

2010-01-01

Recently, cellulose has been re-discovered as a smart material that can be used as sensor and actuator materials, which is termed electro-active paper (EAPap). This paper reports recent advances in paper actuators made with cellulose and hybrid materials such as multi-walled carbon nanotubes, conducting polymers and ionic liquids. Two distinct actuator principles in EAPap actuators are demonstrated: piezoelectric effect and ion migration effect in cellulose. Piezoelectricity of cellulose EAPap is quite comparable with other piezoelectric polymers. But, it is biodegradable, biocompatible, mechanically strong and thermally stable. To enhance ion migration effect in the cellulose, polypyrrole conducting polymer and ionic liquids were nanocoated on the cellulose film. This hybrid cellulose EAPap nanocomposite exhibits durable bending actuation in an ambient humidity and temperature condition. Fabrication, characteristics and performance of the cellulose EAPap and its hybrid EAPap materials are illustrated. Also, its possibility for remotely microwave-driven paper actuator is demonstrated. PMID:22294882

A Novel Ionic Polymer Metal ZnO Composite (IPMZC)

PubMed Central

Kim, Sang-Mun; Tiwari, Rashi; Kim, Kwang J.

2011-01-01

The presented research introduces a new Ionic Polymer-Metal-ZnO Composite (IPMZC) demonstrating photoluminescence (PL)-quenching on mechanical bending or application of an electric field. The newly fabricated IPMZC integrates the optical properties of ZnO and the electroactive nature of Ionic Polymer Metal Composites (IPMC) to enable a non-contact read-out of IPMC response. The electro-mechano-optical response of the IPMZC was measured by observing the PL spectra under mechanical bending and electrical regimes. The working range was measured to be 375–475 nm. It was noted that the PL-quenching increased proportionally with the increase in curvature and applied field at 384 and 468 nm. The maximum quenching of 53.4% was achieved with the membrane curvature of 78.74/m and 3.01% when electric field (12.5 × 103 V/m) is applied. Coating IPMC with crystalline ZnO was observed to improve IPMC transduction. PMID:22163869

Paper actuators made with cellulose and hybrid materials.

PubMed

Kim, Jaehwan; Yun, Sungryul; Mahadeva, Suresha K; Yun, Kiju; Yang, Sang Yeol; Maniruzzaman, Mohammad

2010-01-01

Recently, cellulose has been re-discovered as a smart material that can be used as sensor and actuator materials, which is termed electro-active paper (EAPap). This paper reports recent advances in paper actuators made with cellulose and hybrid materials such as multi-walled carbon nanotubes, conducting polymers and ionic liquids. Two distinct actuator principles in EAPap actuators are demonstrated: piezoelectric effect and ion migration effect in cellulose. Piezoelectricity of cellulose EAPap is quite comparable with other piezoelectric polymers. But, it is biodegradable, biocompatible, mechanically strong and thermally stable. To enhance ion migration effect in the cellulose, polypyrrole conducting polymer and ionic liquids were nanocoated on the cellulose film. This hybrid cellulose EAPap nanocomposite exhibits durable bending actuation in an ambient humidity and temperature condition. Fabrication, characteristics and performance of the cellulose EAPap and its hybrid EAPap materials are illustrated. Also, its possibility for remotely microwave-driven paper actuator is demonstrated.

Gel electrolytes and electrodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fleischmann, Sven; Bunte, Christine; Mikhaylik, Yuriy V.

Gel electrolytes, especially gel electrolytes for electrochemical cells, are generally described. In some embodiments, the gel electrolyte layers comprise components a) to c). Component a) may be at least one layer of at least one polymer comprising polymerized units of: a1) at least one monomer containing an ethylenically unsaturated unit and an amido group and a2) at least one crosslinker. Component b) may be at least one conducting salt and component c) may be at least one solvent. Electrodes may comprise the components a), d) and e), wherein component a) may be at least one layer of at least onemore » polymer as described herein. Component d) may be at least one electroactive layer and component e) may be at least one ceramic layer. Furthermore, electrochemical cells comprising component a) which may be at least one layer of at least one polymer as described herein, are also provided.« less

Focus tunable device actuator based on ionic polymer metal composite

NASA Astrophysics Data System (ADS)

Zhang, Yi-Wei; Su, Guo-Dung J.

2015-09-01

IPMC (Ionic Polymer Metallic Composite) is a kind of electroactive polymer (EAP) which is used as an actuator because of its low driving voltage and small size. The mechanism of IPMC actuator is due to the ionic diffusion when the voltage gradient is applied. In this paper, the complex IPMC fabrication such as Ag-IPMC be further developed in this paper. The comparison of response time and tip bending displacement of Pt-IPMC and Ag-IPMC will also be presented. We also use the optimized IPMC as the lens actuator integrated with curvilinear microlens array, and use the 3D printer to make a simple module and spring stable system. We also used modeling software, ANSYS Workbench, to confirm the effect of spring system. Finally, we successfully drive the lens system in 200μm stroke under 2.5V driving voltage within 1 seconds, and the resonant frequency is approximately 500 Hz.

Accurate determination of dielectric permittivity of polymers from 75  GHz to 1.6  THz using both S-parameters and transmission spectroscopy.

PubMed

Chang, Tianying; Zhang, Xiansheng; Zhang, Xiaoxuan; Cui, Hong-Liang

2017-04-20

Interactions of terahertz (THz) electromagnetic radiation with polymer materials have been studied recently with increasing depth and breadth, for purposes of both using polymers in fabricating THz optical components such as lenses, waveplates, waveguides, and sample holders/containers, and employing THz spectral imaging as a new tool for nondestructive testing of polymer composite structures. Either endeavor cannot even begin without a quantitative knowledge of the complex dielectric permittivity, i.e., the propagation and attenuation properties of such polymers in the requisite wave band. In this paper, a number of non-polar and non-magnetic polymers, such as polytetrafluoroethylene, polypropylene, high-density polyethylene, and polymethyl methacrylate, are studied for the purpose of determining their complex dielectric permittivity, including its real part and imaginary parts, in the wide frequency band from millimeter wave to THz wave (75 GHz-1.6 THz), in two ways. The first is a free space method based on a vector network analyzer covering the frequency region from 75 to 500 GHz, and the second is the THz time-domain spectroscopy (THz-TDS), effective for the region of 100 GHz-1.6 THz. The results are consistent with existing data (with discrepancies less than 1% in most cases for both the index of refraction and the absorption coefficient), and where they overlap in frequency coverage, the two methods yield identical results to within measurement error.

High-brightness laser imaging with tunable speckle reduction enabled by electroactive micro-optic diffusers.

PubMed

Farrokhi, Hamid; Rohith, Thazhe Madam; Boonruangkan, Jeeranan; Han, Seunghwoi; Kim, Hyunwoong; Kim, Seung-Woo; Kim, Young-Jin

2017-11-10

High coherence of lasers is desirable in high-speed, high-resolution, and wide-field imaging. However, it also causes unavoidable background speckle noise thus degrades the image quality in traditional microscopy and more significantly in interferometric quantitative phase imaging (QPI). QPI utilizes optical interference for high-precision measurement of the optical properties where the speckle can severely distort the information. To overcome this, we demonstrated a light source system having a wide tunability in the spatial coherence over 43% by controlling the illumination angle, scatterer's size, and the rotational speed of an electroactive-polymer rotational micro-optic diffuser. Spatially random phase modulation was implemented for the lower speckle imaging with over a 50% speckle reduction without a significant degradation in the temporal coherence. Our coherence control technique will provide a unique solution for a low-speckle, full-field, and coherent imaging in optically scattering media in the fields of healthcare sciences, material sciences and high-precision engineering.

Natural gum-assisted phthalocyanine immobilization in electroactive nanocomposites: physicochemical characterization and sensing applications.

PubMed

Zampa, Maysa F; de Brito, Ana Cristina F; Kitagawa, Igor L; Constantino, Carlos J L; Oliveira, Osvaldo N; da Cunha, Helder N; Zucolotto, Valtencir; dos Santos, José Ribeiro; Eiras, Carla

2007-11-01

Natural gums have been traditionally applied in cosmetics and the food industry, mainly as emulsification agents. Due to their biodegradability and excellent mechanical properties, new technological applications have been proposed involving their use with conventional polymers forming blends and composites. In this study, we take advantage of the polyelectrolyte character exhibited by the natural gum ChichA (Sterculia striata), extracted in the Northeastern region of Brazil, to produce electroactive nanocomposites. The nanocomposites were fabricated in the form of ultrathin films by combining a metallic phthalocyanine (nickel tetrasulfonated phthalocyanine, NiTsPc) and the ChichA gum in a tetralayer architecture, in conjunction with conventional polyelectrolytes. The presence of the gum led to an efficient adsorption of the phthalocyanine and enhanced the electrochemical response of the films. Upon combining the electrochemical and UV-vis absorption data, energy diagrams of the ChichA/NiTsPc-based system were obtained. Furthermore, modified electrodes based on gum/phthalocyanine films were able to detect dopamine at concentrations as low as 10-5 M.

Dielectric and thermal properties of the methacrylate polymer bearing chalcone side group

NASA Astrophysics Data System (ADS)

Çelik, Taner; Coşkun, Mehmet Fatih

2018-04-01

The 1-(1-benzofuran-2yl)-3-(4-hydroxyphenyl)propen-1-one (compound 1) from the reaction between 1-(1-benzofuran-2-yl) ethanone and 4-hydroxybenzaldehyde was firstly synthesized. And secondly, we synthesized 4-[3-(1-benzofuran-2-yl)-3-oxoprop-1-en-1-yl] phenyl chloroacetate (compound 2) as the result of the reaction between the compound 1 and chloroacetyl chloride. The monomer was prepared by the reaction of compound 2 and sodium methacrylate. The monomer was polymerized using the free radicalic polymerization method (FRP). The structure characterization of the polymer was determined utilizing 1H,13C- NMR and FT-IR techniques. Thermal behaviour of the homopolymer was studied by measurements of TGA and DSC. For thermal decomposition kinetics of homopolymer, Flynn-Wall-Ozawa method was applied to thermogravimetry curves. The dielectric measurements were studied using the impedance analyzer technique at a frequency which varied between 100 Hz and 20 kHz Hz depending on the alternating current (AC) conductivities. The dielectric parameters such as dielectric constant and dielectric loss are changed with the temperature.

Sol-gel derived polymer composites for energy storage and conversion

NASA Astrophysics Data System (ADS)

Han, Kuo

Sol-gel process is a simple chemistry to convert the small precursor molecules into an inorganic polymer, which could be applied to synthesize inorganic materials, modify the interface of materials, bridge the organic and inorganic materials, etc. In this dissertation, novel sol-gel derived composites have been developed for high dielectric breakdown capacitors, low high frequency loss capacitors and flexible piezoelectrics. Numerous efforts have been made in the past decades to improve the energy storage capability of composite materials by incorporating nanometer scale ceramic addictives with high dielectric permittivity into dielectric polymers with high breakdown strength. However, most composites suffer from the low breakdown strength and make the potential gain in energy density small. Here, a new chemical strategy is proposed that, through sol-gel reactions between ceramic precursors and functional groups at the end of the functionalized Poly(vinylidene fluoride -co-chlorotrifluoroethylene) chains, amorphous low permittivity ceramics was in-situ generated in the polymer matrix and cross-linked the polymer chains simultaneously. By carefully tuning precursors, the polymer/precursors feeding ratios, a series of nanocomposites were systematically designed. All the samples are comprehensively characterized and the structure-property correlations are well investigated. The optimal samples exhibit higher breakdown strength than the pristine polymer. The enhanced breakdown strength ascribed to low contrast in permittivity, great dispersion and improved electrical and mechanical properties. This newly developed approach has shown great promise for new composite capacitors. The percolative polymer composites have recently exhibited great potential in energy storage due to their high dielectric permittivities at the neighborhood of the percolation threshold. Yet high energy dissipation and poor voltage endurance of the percolative composites resulted from electrical conduction are still open issues to be addressed before full potential can be realized. Herein we report the percolative composites based on ferroelectric poly(vinylidene fluoride-co-chlorotrifluoroethylene) as the matrix and sol-gel derived SiO2 coated reduced graphene oxide nanosheets as the filler. By capitalizing on the SiO2 surface layers which have high electrical resistivity and breakdown strength, the composites exhibit superior dielectric performance as compared to the respective composites containing bare reduced graphene oxide nanosheet fillers. In addition to greatly reduced dielectric loss, little change in dielectric loss has been observed within medium frequency range (ie. 300 KHz-3 MHz) in the prepared composites even with a filler concentration beyond the percolation threshold, indicating significantly suppressed energy dissipation and the feasibility of using the conductor-insulator composites beyond the percolation threshold. Moreover, remarkable breakdown strength of 80 MV/m at the percolation threshold has been achieved in the composite, which far exceeds those of conventional percolative composites (lower than 0.1 MV/m in most cases) and thus enables the applications of the percolative composites at high electric fields. This work offers a new avenue to the percolative polymer composites exhibiting high permittivity, reduced loss and excellent breakdown strength for electrical energy storage applications. Flexible piezoelectric materials have attracted extensive attention because they can provide a practical way to scavenge energy from the environment and motions. It also provides the possibility to fabricate wearable and self-powered energy generator for powering small electronic devices. In the dissertation a new composite including BTO 3D structure and PDMS has been successfully fabricated using the sol-gel process. The structure, flexibility, dielectric and piezoelectric properties have been well studied. The new material shows a high g33 value of more than 400 mV m/N. Moreover, the durability of this composite has been confirmed by cycle tests even though the BTO structure falls apart into small pieces in the PDMS matrix. The unique morphology of the composite allows the broken piece to connect with each other to generate power under stress. This work also opens a new route toward flexible piezoelectric composites.

The origin of excellent gate-bias stress stability in organic field-effect transistors employing fluorinated-polymer gate dielectrics.

PubMed

Kim, Jiye; Jang, Jaeyoung; Kim, Kyunghun; Kim, Haekyoung; Kim, Se Hyun; Park, Chan Eon

2014-11-12

Tuning of the energetic barriers to charge transfer at the semiconductor/dielectric interface in organic field-effect transistors (OFETs) is achieved by varying the dielectric functionality. Based on this, the correlation between the magnitude of the energy barrier and the gate-bias stress stability of the OFETs is demonstrated, and the origin of the excellent device stability of OFETs employing fluorinated dielectrics is revealed. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dielectric Properties of PMMA and its Composites with ZrO2

NASA Astrophysics Data System (ADS)

Sannakki, Basavaraja; Anita

The polymer films of PMMA with different thickness and its composites with ZrO2 at various weight percentages but of same thickness have been studied. The determination of its dielectric properties, dielectric loss, a.conductivity and dielectric modulus were carried out using capacitance measurements of the above samples as a function of frequency, over the range 50 Hz - 5 MHz at room temperature. The films of PMMA and its composites have been characterized using X-Ray Diffractometer. The dielectric permittivity of films of PMMA behaves nonlinearly as frequency increases over the range 50-300 Hz, where as above 300 Hz the values of dielectric constant remains constant. But it is observed that the dielectric constant of PMMA increases as thickness of the film increases. In case of composite films of PMMA with ZrO2 the values of dielectric permittivity decreases gradually up to frequency of around 1 KHz and at higher frequencies it remains constant for all the weight percentages of ZrO2. The complex form of dielectric modulus of PMMA is obtained from the experimentally measured data of dielectric constant and dielectric loss values. The relaxation time of the orientation of dipoles is obtained from the peak value of angular frequency through the plots of imaginary part of electrical modulus as function of frequency. The impedance of PMMA polymer increases as thickness of the films increases. The a c conductivity of PMMA film remains constant up to frequency of 1 MHz and above. It shows a nonlinear phenomenon with peak values at frequency 4 MHz. Shape and size of the nanoparticles of composite film of PMMA with ZrO2 was analyzed by Field Emission Scanning Electron Microscope (FESEM).

New secondary batteries utilizing electronically conductive polymer cathodes

NASA Technical Reports Server (NTRS)

Martin, Charles R.; White, Ralph E.

1989-01-01

The objectives of this project are to optimize the transport rates in electronically conductive polypyrrole films by controlling the morphology of the film and to assess the utility of these films as cathodes in a lithium/polypyrrole secondary battery. During this research period, progress has been made in improving the charge transport rate of the supermolecular-engineered polypyrrole electrode by eliminating the polypyrrole baselayer that hampered earlier work. Also, the fibril density of the polypyrrole electrode was increased, providing more electroactive sites per unit area.

Multifunctional Carbon Nanotube Fiber Composites

DTIC Science & Technology

2004-12-26

Opt. Eng. 4234 (Smart Materials), 223-23 1, (2001). 9. " Microfabricated Electroactive Carbon Nanotube Actuators", A. Ahluwalia, R.H. Baughman, D. De...peristaltic pumped circulating flow of PVA operating in an open loop consisting of a 1.5 m long, 0.40 cm diameter glass pipe , flex-tubing, and a polymer reserve...forming a gel-like ribbon that flows down the length of the pipe before being released into a rotating water bath where it is collected on a mandrel. Our

X-Ray Diffraction Studies of the Structure of Ordered Polymers and Related Electro-Active Materials

DTIC Science & Technology

1990-12-31

benzothiazole, 2-[2-(N,N-diethylamino)-5-nitropHenyl]benzothiazole, and 2-(trimethylsilylethynyl)-4-nitro-N,N-dimethylaniline. In all four compounds , the alkyl...nitrophenyl]benzothiazole, and 2-(trimethylsilylethynyl)-4-nitro-N,N-dimethylaniline isee Preprint 2 for details). In all four compounds , the alkyl groups...septiphenyl (DPSP), and 1,2.4- Iriphenylbenzene TPS). The fm four compounds have the genral smcurn (1) where n - I and R - H for PQP. n a I and R

Ultrasonic and dielectric studies of polymer PDMS composites with ZnO and onion-like carbons nanoinclusions

NASA Astrophysics Data System (ADS)

Samulionis, V.; Macutkevic, J.; Banys, J.; Belovickis, J.; Shenderova, O.

2015-07-01

The ultrasonic and dielectric temperature investigations were performed in polydi- methylsiloxane (PDMS) with zinc oxide (ZnO) and onion-like carbon (OLC) nanocomposites. In the glass transition region, the ultrasonic velocity dispersion and large ultrasonic attenuation maxima were observed. The positions of ultrasonic attenuation peaks were slightly shifted to higher temperatures after doping PDMS with OLC and ZnO nanoparticles. The ultrasonic relaxation was compared to that of dielectric and such behaviour was described by Vogel- Fulcher law. The upshift of the glass transition temperature with addition of nanoparticles was confirmed by both methods. The additional increase of ultrasonic attenuation in composites doped with OLC and ZnO was observed at room temperature and such behaviour we attributed to ultrasound-nanofiller interaction in polymer matrix.

Electromagnetic Nondestructive Evaluation of Wire Insulation and Models of Insulation Material Properties

NASA Technical Reports Server (NTRS)

Bowler, Nicola; Kessler, Michael R.; Li, Li; Hondred, Peter R.; Chen, Tianming

2012-01-01

Polymers have been widely used as wiring electrical insulation materials in space/air-craft. The dielectric properties of insulation polymers can change over time, however, due to various aging processes such as exposure to heat, humidity and mechanical stress. Therefore, the study of polymers used in electrical insulation of wiring is important to the aerospace industry due to potential loss of life and aircraft in the event of an electrical fire caused by breakdown of wiring insulation. Part of this research is focused on studying the mechanisms of various environmental aging process of the polymers used in electrical wiring insulation and the ways in which their dielectric properties change as the material is subject to the aging processes. The other part of the project is to determine the feasibility of a new capacitive nondestructive testing method to indicate degradation in the wiring insulation, by measuring its permittivity.

Directionally Aligned Amorphous Polymer Chains via Electrohydrodynamic-Jet Printing: Analysis of Morphology and Polymer Field-Effect Transistor Characteristics.

PubMed

Kim, Yebyeol; Bae, Jaehyun; Song, Hyun Woo; An, Tae Kyu; Kim, Se Hyun; Kim, Yun-Hi; Park, Chan Eon

2017-11-15

Electrohydrodynamic-jet (EHD-jet) printing provides an opportunity to directly assembled amorphous polymer chains in the printed pattern. Herein, an EHD-jet printed amorphous polymer was employed as the active layer for fabrication of organic field-effect transistors (OFETs). Under optimized conditions, the field-effect mobility (μ FET ) of the EHD-jet printed OFETs was 5 times higher than the highest μ FET observed in the spin-coated OFETs, and this improvement was achieved without the use of complex surface templating or additional pre- or post-deposition processing. As the chain alignment can be affected by the surface energy of the dielectric layer in EHD-jet printed OFETs, dielectric layers with varying wettability were examined. Near-edge X-ray absorption fine structure measurements were performed to compare the amorphous chain alignment in OFET active layers prepared by EHD-jet printing and spin coating.

Hybrid polymer networks as ultra low `k` dielectric layers

DOEpatents

Lewicki, James; Worsley, Marcus A.

2016-02-16

According to one embodiment, a polymeric material includes at least one polydimethylsiloxane (PDMS) polymer, and at least one polyhedral oligomericsilsequioxane (POSS) molecule. According to another embodiment, a method includes providing at least one polydimethylsiloxane (PDMS) polymer, providing at least one polyhedral oligomericsilsequioxane (POSS) molecule, and coupling the at least one PDSM polymer to the at least one POSS molecule to form a hybrid polymeric material.

High temperature dielectric properties of Apical, Kapton, Peek, Teflon AF, and Upilex polymers

NASA Technical Reports Server (NTRS)

Hammoud, A. N.; Baumann, E. D.; Overton, E.; Myers, I. T.; Suthar, J. L.; Khachen, W.; Laghari, J. R.

1992-01-01

Reliable lightweight systems capable of providing electrical power at the magawatt level are a requirement for future manned space exploration missions. This can be achieved by the development of high temperature insulating materials which are not only capable of surviving the hostile space environment but can contribute to reducing the mass and weight of the heat rejection system. In this work, Apical, Upilex, Kapton, Teflon AF, and Peek polymers are characterized for AC and DC dielectric breakdown in air and in silicone oil at temperatures up to 250 C. The materials are also tested in terms of their dielectric constant and dissipation factor at high temperatures with an electrical stress of 60 Hz, 200 V/mil present. The effects of thermal aging on the properties of the films are determined after 15 hours of exposure to 200 and 250 C, each. The results obtained are discussed and conclusions are made concerning the suitability of these dielectrics for use in capacitors and cable insulations in high temperature environments.

High temperature dielectric properties of Apical, Kapton, Peek, Teflon AF, and Upilex polymers

NASA Astrophysics Data System (ADS)

Hammoud, A. N.; Baumann, E. D.; Overton, E.; Myers, I. T.; Suthar, J. L.; Khachen, W.; Laghari, J. R.

1992-06-01

Reliable lightweight systems capable of providing electrical power at the magawatt level are a requirement for future manned space exploration missions. This can be achieved by the development of high temperature insulating materials which are not only capable of surviving the hostile space environment but can contribute to reducing the mass and weight of the heat rejection system. In this work, Apical, Upilex, Kapton, Teflon AF, and Peek polymers are characterized for AC and DC dielectric breakdown in air and in silicone oil at temperatures up to 250 C. The materials are also tested in terms of their dielectric constant and dissipation factor at high temperatures with an electrical stress of 60 Hz, 200 V/mil present. The effects of thermal aging on the properties of the films are determined after 15 hours of exposure to 200 and 250 C, each. The results obtained are discussed and conclusions are made concerning the suitability of these dielectrics for use in capacitors and cable insulations in high temperature environments.

Supercapacitors: Ferroelectric Polymer-Ceramic Nanoparticle Composite Films for Use in the Capacitive Storage of Electrical Energy

NASA Astrophysics Data System (ADS)

Parsons, Dana; Pierce, Andrew; Porter, Tim; Dillingham, Randy; Cornelison, David

2010-03-01

Most new alternative energy solutions including wind and solar power, will require short term energy storage for widespread implementation. One means of storage would be the use of capacitors owing to their rapid delivery of power and longevity compared to chemical batteries. Capacitor materials exhibiting high dielectric permittivity and breakdown strength, as well as light weight and environmental safety are most desirable. Recently, new classes of capacitor dielectric materials, consisting of ferroelectric polymer matrices containing ceramic nanoparticles have attracted renewed interest due to their high potential energy storage, charge and discharge properties and lightweight. In this study, polyvinylidene flouride (PVDF) thin films containing nanoparticles of the ceramic titanium dioxide created using a physical vapor deposition process, are analyzed for use as dielectrics for a supercapacitor. Measured results of the film parameters including dielectric properties and breakdown voltages will be presented. These parameters will be analyzed with respect to film characteristics such as, dispersion of the ceramic particles, thickness of the films and composition ratios.

Dielectric Properties of Generation 3 Pamam Dendrimer Nanocomposites

NASA Astrophysics Data System (ADS)

Ristić, Sanja; Mijović, Jovan

2008-08-01

Broadband dielectric relaxation spectroscopy (DRS) was employed to study molecular dynamics of blends composed of generation 3 poly(amidoamine) (PAMAM) dendrimers with ethylenediamine core and amino surface groups and four linear polymers: poly(propylene oxide)—PPO, two block copolymers, poly(propylene oxide)/poly(ethylene oxide)—PPO/PEO with different mol ratios (29/6 and 10/31) and poly(ethylene oxide)—PEO. The results were generated over a broad range of frequency. Dielectric spectra of dendrimers in PPO matrix reveal slight shift of normal and segmental processes to higher frequency with increasing concentration of dendrimers. In the 29PPO/6PEO matrix, no effect of concentration on the average relaxation time for normal and segmental processes was observed. In the 10PPO/31PEO matrix the relaxation time of the segmental process increases with increasing dendrimer concentration, while in the PEO matrix, local processes in dendrimers slow down. A detailed analysis of the effect of concentration of dendrimers and morphology of polymer matrix on the dielectric properties of dendrimer nanocomposites will be presented.

Coated electroactive materials

DOEpatents

Amine, Khalil; Abouimrane, Ali

2016-08-30

A process includes suspending an electroactive material in a solvent, suspending or dissolving a carbon precursor in the solvent; and depositing the carbon precursor on the electroactive material to form a carbon-coated electroactive material. Compositions include a graphene-coated electroactive material prepared from a solution phase mixture or suspension of an electroactive material and graphene, graphene oxide, or a mixture thereof.

Bandlike Transport in Ferroelectric-Based Organic Field-Effect Transistors

NASA Astrophysics Data System (ADS)

Laudari, A.; Guha, S.

2016-10-01

The dielectric constant of polymer-ferroelectric dielectrics may be tuned by changing the temperature, offering a platform for monitoring changes in interfacial transport with the polarization strength in organic field-effect transistors (FETs). Temperature-dependent transport studies of FETs are carried out from a solution-processed organic semiconductor, 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene), using both ferroelectric- and nonferroelectric-gate insulators. Nonferroelectric dielectric-based TIPS-pentacene FETs show a clear activated transport, in contrast to the ferroelectric dielectric polymer, poly(vinylidene fluoride-trifluoroethylene), where a negative temperature coefficient of the mobility is observed in the ferroelectric temperature range. The current-voltage (I -V ) characteristics from TIPS-pentacene diodes signal a space-charge-limited conduction (SCLC) for a discrete set of trap levels, suggesting that charge injection and transport occurs through regions of ordering in the semiconductor. The carrier mobility extracted from temperature-dependent I -V characteristics from the trap-free SCLC region shows a negative coefficient beyond 200 K, similar to the trend observed in FETs with the ferroelectric dielectric. At moderate temperatures, the polarization-fluctuation-dominant transport inherent in a ferroelectric dielectric, in conjunction with the nature of traps, results in an effective detrapping of the shallow-trap states into more mobile states in TIPS-pentacene.

Dielectric breakdown of additively manufactured polymeric materials

DOE PAGES

Monzel, W. Jacob; Hoff, Brad W.; Maestas, Sabrina S.; ...

2016-01-11

Dielectric strength testing of selected Polyjet-printed polymer plastics was performed in accordance with ASTM D149. This dielectric strength data is compared to manufacturer-provided dielectric strength data for selected plastics printed using the stereolithography (SLA), fused deposition modeling (FDM), and selective laser sintering (SLS) methods. Tested Polyjet samples demonstrated dielectric strengths as high as 47.5 kV/mm for a 0.5 mm thick sample and 32.1 kV/mm for a 1.0 mm sample. As a result, the dielectric strength of the additively manufactured plastics evaluated as part of this study was lower than the majority of non-printed plastics by at least 15% (with themore » exception of polycarbonate).« less

Dielectric breakdown of additively manufactured polymeric materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Monzel, W. Jacob; Hoff, Brad W.; Maestas, Sabrina S.

Dielectric strength testing of selected Polyjet-printed polymer plastics was performed in accordance with ASTM D149. This dielectric strength data is compared to manufacturer-provided dielectric strength data for selected plastics printed using the stereolithography (SLA), fused deposition modeling (FDM), and selective laser sintering (SLS) methods. Tested Polyjet samples demonstrated dielectric strengths as high as 47.5 kV/mm for a 0.5 mm thick sample and 32.1 kV/mm for a 1.0 mm sample. As a result, the dielectric strength of the additively manufactured plastics evaluated as part of this study was lower than the majority of non-printed plastics by at least 15% (with themore » exception of polycarbonate).« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Samant, Saumil P.; Grabowski, Christopher A.; Kisslinger, Kim

Emerging needs for fast charge/discharge yet high-power, lightweight, and flexible electronics requires the use of polymer-film-based solid-state capacitors with high energy densities. Fast charge/discharge rates of film capacitors on the order of microseconds are not achievable with slower charging conventional batteries, supercapacitors and related hybrid technologies. However, the current energy densities of polymer film capacitors fall short of rising demand, and could be significantly enhanced by increasing the breakdown strength (E BD) and dielectric permittivity (ε r) of the polymer films. Co-extruded two-homopolymer component multilayered films have demonstrated much promise in this regard showing higher E BD over that ofmore » component polymers. Multilayered films can also help incorporate functional features besides energy storage, such as enhanced optical, mechanical, thermal and barrier properties. In this work, we report accomplishing multilayer, multicomponent block copolymer dielectric films (BCDF) with soft-shear driven highly oriented self-assembled lamellar diblock copolymers (BCP) as a novel application of this important class of self-assembling materials. Results of a model PS-b-PMMA system show ~50% enhancement in E BD of self-assembled multilayer lamellar BCP films compared to unordered as-cast films, indicating that the breakdown is highly sensitive to the nanostructure of the BCP. The enhancement in E BD is attributed to the “barrier effect”, where the multiple interfaces between the lamellae block components act as barriers to the dielectric breakdown through the film. The increase in E BD corresponds to more than doubling the energy storage capacity using a straightforward directed self-assembly strategy. This approach opens a new nanomaterial paradigm for designing high energy density dielectric materials.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Samant, Saumil P.; Grabowski, Christopher A.; Kisslinger, Kim

Emerging needs for fast charge/discharge yet high-power, lightweight, and flexible electronics requires the use of polymer-film-based solid-state capacitors with high energy densities. Fast charge/discharge rates of film capacitors on the order of microseconds are not achievable with slower charging conventional batteries, supercapacitors and related hybrid technologies. However, the current energy densities of polymer film capacitors fall short of rising demand, and could be significantly enhanced by increasing the breakdown strength (E BD) and dielectric permittivity (ε r) of the polymer films. Co-extruded two-homopolymer component multilayered films have demonstrated much promise in this regard showing higher E BD over that ofmore » component polymers. Multilayered films can also help incorporate functional features besides energy storage, such as enhanced optical, mechanical, thermal and barrier properties. In this work, we report accomplishing multilayer, multicomponent block copolymer dielectric films (BCDF) with soft-shear driven highly oriented self-assembled lamellar diblock copolymers (BCP) as a novel application of this important class of self-assembling materials. Results of a model PS- b-PMMA system show ~50% enhancement in E BD of self-assembled multilayer lamellar BCP films compared to unordered as-cast films, indicating that the breakdown is highly sensitive to the nanostructure of the BCP. The enhancement in E BD is attributed to the “barrier effect”, where the multiple interfaces between the lamellae block components act as barriers to the dielectric breakdown through the film. The increase in E BD corresponds to more than doubling the energy storage capacity using a straightforward directed self-assembly strategy. Lastly, this approach opens a new nanomaterial paradigm for designing high energy density dielectric materials.« less

Polymer loaded microemulsions: Changeover from finite size effects to interfacial interactions

NASA Astrophysics Data System (ADS)

Kuttich, B.; Ivanova, O.; Grillo, I.; Stühn, B.

2016-10-01

Form fluctuations of microemulsion droplets are observed in experiments using dielectric spectroscopy (DS) and neutron spin echo spectroscopy (NSE). Previous work on dioctyl sodium sulfosuccinate based water in oil microemulsions in the droplet phase has shown that adding a water soluble polymer (Polyethylene glycol M = 1500 g mol-1) modifies these fluctuations. While for small droplet sizes (water core radius rc < 37 Å) compared to the size of the polymer both methods consistently showed a reduction in the bending modulus of the surfactant shell as a result of polymer addition, dielectric spectroscopy suggests the opposite behaviour for large droplets. This observation is now confirmed by NSE experiments on large droplets. Structural changes due to polymer addition are qualitatively independent of droplet size. Dynamical properties, however, display a clear variation with the number of polymer chains per droplet, leading to the observed changes in the bending modulus. Furthermore, the contribution of structural and dynamical properties on the changes in bending modulus shifts in weight. With increasing droplet size, we initially find dominating finite size effects and a changeover to a system, where interactions between the confined polymer and the surfactant shell dominate the bending modulus.

Enhancement of the optical, thermal and electrical properties of PEO/PAM:Li polymer electrolyte films doped with Ag nanoparticles

NASA Astrophysics Data System (ADS)

Morsi, M. A.; El-Khodary, Sherif A.; Rajeh, A.

2018-06-01

Both lithium bromide (LiBr) and biosynthesized silver nanoparticles (Ag NPs) with average size 2-30 nm have been incorporated into the polymeric matrix of polyethylene oxide and polyacrylamide (PEO/PAM) blend by the casting method. FT-IR analysis indicates the formation of hydrogen bond between the blend components. Also, LiBr and Ag NPs interact with the functional groups of PEO/PAM matrix. The results of XRD analysis depict the semi-crystalline nature of these polymer samples and the degree of crystallinity is decreased due to the addition process. The values of optical energy gap from UV-Vis. data are decreased from 3.55 eV for blend to 3.26 for the nanocomposite sample in the indirect transition. LiBr/Ag NPs assist the improvement of the thermal stability of the PEO/PAM blend, as evidenced by TGA and DTA techniques. Upon the addition of LiBr and Ag NPs, an improvement for the conductivity, dielectric permittivity (έ) and dielectric loss (ἕ) of PEO/PAM solid polymer electrolytes are observed. It's clear that the improvement of the electrical conductivity and dielectric parameters for PEO/PAM: Li+/Ag NPs polymer electrolyte system makes it as a promising candidate for solid-state Li battery applications.

Enhancement of the electromechanical transduction properties of a silicone elastomer by blending with a conjugated polymer

NASA Astrophysics Data System (ADS)

Carpi, F.; Gallone, G.; Galantini, F.; De Rossi, D.

2008-03-01

The need for high driving electric fields currently limits the diffusion of dielectric elastomer actuation in some areas of potential application, especially in the case of biomedical disciplines. A reduction of the driving fields may be achieved with new elastomers offering intrinsically superior electromechanical properties. So far, most of attempts in this direction have been focused on composites between elastomer matrixes and high-permittivity ceramic fillers, yielding to limited results. In this work, the electromechanical response of a silicone rubber (poly-dimethyl-siloxane) was improved by blending, rather than loading, the elastomer with a highly polarizable conjugated polymer (undoped poly-hexyl-thiophene). Very low percentages (1-6 wt%) of poly-hexyl-thiophene yielded both an increase of the dielectric permittivity and an unexpected reduction of the tensile elastic modulus. Both these factors contributed to a remarkable increase of the electromechanical response, which reached a maximum at 1 wt% content of conjugated polymer. This approach may lead to the development of new types of improved dielectric elastomers for actuation.

Actuated polymer based dielectric mirror for visual spectral range applications

NASA Astrophysics Data System (ADS)

Vergara, Pedro P.; Lunardi, Leda

2017-08-01

Miniature dielectric mirrors are useful components for lasers, thin film beam splitters and high quality mirrors in optics. These mirrors usually made from rigid inorganic materials can achieve a reflectance of almost one hundred percent. Being structural components, as soon as fabricated their reflectance and/or bandwidth remains constant. Here it is presented a novel fabrication process of a dielectric mirror based on free standing polymer layers. By applying an electrostatic force between the top and the bottom layers the reflectance can be changed. The large difference between the polymers refractive index and the air allows to achieve a reflectance of more than 85% using only six pairs of nanolayers. Preliminary simulations indicate an actuation speed of less than 1ms. Experimental optical characterization of fabricated structures agrees well with simulation results. Furthermore, structures can be designed to reflect a particular set of colors and/or isolated by using color filters, so a color pixel is fabricated, where the reflectance for each isolated color can be voltage controlled. Potential applications include an active component in a reflective screen display.

Structural and Dielectric Properties of Ionic Liquid Doped Metal Organic Framework based Polymer Electrolyte Nanocomposites

NASA Astrophysics Data System (ADS)

Dutta, Rituraj; Kumar, Ashok

2016-10-01

Metal Organic Frameworks (MOFs) are mesoporous materials that can be treated as potential hosts for trapping guest molecules in their pores. Ion conduction and phase behavior dynamics of Ionic Liquids (ILs) can be controlled by tunable interactions of MOFs with the ILs. MOFs incorporated with ionic liquid can be dispersed in the polymers to synthesize polymer electrolyte nanocomposites with high ionic conductivity, electrochemical and thermal stability for applications in energy storage and conversion devices such as rechargeable Li-ion batteries. In the present work we have synthesized Cu-based MOF [Cu3(l,3,5-benzene tricarboxylate)2(H2O)] incorporated with the ionic liquid 1-Butyl-3-methylimidazolium bromide at different weight ratios of MOF and IL. The synthesized MOF-IL composites are dispersed in Poly (ethylene oxide) (PEO). Frequency dependent behavior of permittivity and dielectric loss of the nanocomposites depict the non-Debye dielectric relaxation mechanism. The room temperature Nyquist plots reveal decreasing bulk resistance upto 189 Ω with optimum ionic conductivity of 1.3×10-3S cm-1at maximum doping concentration of IL in the nanocomposite system.

Electroactive and biocompatible functionalization of graphene for the development of biosensing platforms.

PubMed

Halder, Arnab; Zhang, Minwei; Chi, Qijin

2017-01-15

Design and synthesis of low-cost, highly stable, electroactive and biocompatible material is one of the key steps for the advancement of electrochemical biosensing systems. To this end, we have explored a facile way for the successful synthesis of redox active and bioengineering of reduced graphene oxide (RGO) for the development of versatile biosensing platform. A highly branched polymer (PEI) is used for reduction and simultaneous derivation of graphene oxide (GO) to form a biocompatible polymeric matrix on RGO nanosheet. Ferrocene redox moieties are then wired onto RGO nanosheets through the polymer matrix. The as-prepared functional composite is electrochemically active and enables to accommodate enzymes stably. For proof-of-concept studies, two crucial redox enzymes for biosensors (i.e. cholesterol oxidase and glucose oxidase) are targeted. The enzyme integrated and RGO supported biosensing hybrid systems show high stability, excellent selectivity, good reproducibility and fast sensing response. As measured, the detection limit of the biosensors for glucose and cholesterol is 5µM and 0.5µM (S/N=3), respectively. The linear response range of the biosensor is from 0.1 to 15.5mM for glucose and from 2.5 to 25µM for cholesterol. Furthermore, this biosensing platform shows good anti-interference ability and reasonable stability. The nanohybrid biosensing materials can be combined with screen-printed electrodes, which are successfully used for measuring the glucose and cholesterol level of real human serum samples. Copyright © 2016 Elsevier B.V. All rights reserved.

Negative Dielectric Constant Material Based on Ion Conducting Materials

NASA Technical Reports Server (NTRS)

Gordon, Keith L. (Inventor); Kang, Jin Ho (Inventor); Park, Cheol (Inventor); Lillehei, Peter T. (Inventor); Harrison, Joycelyn S. (Inventor)

2017-01-01

Metamaterials or artificial negative index materials (NIMs) have generated great attention due to their unique and exotic electromagnetic properties. One exemplary negative dielectric constant material, which is an essential key for creating the NIMs, was developed by doping ions into a polymer, a protonated poly (benzimidazole) (PBI). The doped PBI showed a negative dielectric constant at megahertz (MHz) frequencies due to its reduced plasma frequency and an induction effect. The magnitude of the negative dielectric constant and the resonance frequency were tunable by doping concentration. The highly doped PBI showed larger absolute magnitude of negative dielectric constant at just above its resonance frequency than the less doped PBI.

Negative Dielectric Constant Material Based on Ion Conducting Materials

NASA Technical Reports Server (NTRS)

Gordon, Keith L. (Inventor); Kang, Jin Ho (Inventor); Harrison, Joycelyn S. (Inventor); Park, Cheol (Inventor); Lillehei, Peter T. (Inventor)

2014-01-01

Metamaterials or artificial negative index materials (NIMs) have generated great attention due to their unique and exotic electromagnetic properties. One exemplary negative dielectric constant material, which is an essential key for creating the NIMs, was developed by doping ions into a polymer, a protonated poly(benzimidazole) (PBI). The doped PBI showed a negative dielectric constant at megahertz (MHz) frequencies due to its reduced plasma frequency and an induction effect. The magnitude of the negative dielectric constant and the resonance frequency were tunable by doping concentration. The highly doped PBI showed larger absolute magnitude of negative dielectric constant at just above its resonance frequency than the less doped PBI.

Large enhanced dielectric permittivity in polyaniline passivated core-shell nano magnetic iron oxide by plasma polymerization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Joy, Lija K.; Sooraj, V.; Sethulakshmi, N.

2014-03-24

Commercial samples of Magnetite with size ranging from 25–30 nm were coated with polyaniline by using radio frequency plasma polymerization to achieve a core shell structure of magnetic nanoparticle (core)–Polyaniline (shell). High resolution transmission electron microscopy images confirm the core shell architecture of polyaniline coated iron oxide. The dielectric properties of the material were studied before and after plasma treatment. The polymer coated magnetite particles exhibited a large dielectric permittivity with respect to uncoated samples. The dielectric behavior was modeled using a Maxwell–Wagner capacitor model. A plausible mechanism for the enhancement of dielectric permittivity is proposed.

Giant dielectric constant in titania nanoparticles embedded in conducting polymer matrix.

PubMed

Dey, Ashis; De, Sukanta; De, Amitabha; De, S K

2006-05-01

Complex impedance and dielectric permittivity of titania-polypyrrole nanocomposites have been investigated as a function of frequency and temperature at different compositions. A very large dielectric constant of about 13,000 at room temperature has been observed. The colossal dielectric constant is mainly dominated by interfacial polarization due to Maxwell-Wagner relaxation effect. Two completely separate groups of dielectric relaxation have been observed. The low frequency dielectric relaxation arises from surface defect states of titania nanoparticles. The broad peak at high frequency region is attributed to Maxwell-Wagner type polarization originating from the inhomogeneous property of nanocomposite. An abrupt change in grain boundary conductivity and dielectric relaxation associated with titania was observed at around 150 K. Anomalous behavior in conductivity and dielectric relaxation is qualitatively explained by band tail structure of titania nanoparticle.

Electrode materials

DOEpatents

Amine, Khalil; Abouimrane, Ali; Belharouak, Ilias

2017-01-31

A process for forming a surface-treatment layer on an electroactive material includes heating the electroactive material and exposing the electroactive material to a reducing gas to form a surface-treatment layer on the electroactive material, where the surface-treatment layer is a layer of partial reduction of the electroactive material.

Electroactive 3D materials for cardiac tissue engineering

NASA Astrophysics Data System (ADS)

Gelmi, Amy; Zhang, Jiabin; Cieslar-Pobuda, Artur; Ljunngren, Monika K.; Los, Marek Jan; Rafat, Mehrdad; Jager, Edwin W. H.

2015-04-01

By-pass surgery and heart transplantation are traditionally used to restore the heart's functionality after a myocardial Infarction (MI or heart attack) that results in scar tissue formation and impaired cardiac function. However, both procedures are associated with serious post-surgical complications. Therefore, new strategies to help re-establish heart functionality are necessary. Tissue engineering and stem cell therapy are the promising approaches that are being explored for the treatment of MI. The stem cell niche is extremely important for the proliferation and differentiation of stem cells and tissue regeneration. For the introduction of stem cells into the host tissue an artificial carrier such as a scaffold is preferred as direct injection of stem cells has resulted in fast stem cell death. Such scaffold will provide the proper microenvironment that can be altered electronically to provide temporal stimulation to the cells. We have developed an electroactive polymer (EAP) scaffold for cardiac tissue engineering. The EAP scaffold mimics the extracellular matrix and provides a 3D microenvironment that can be easily tuned during fabrication, such as controllable fibre dimensions, alignment, and coating. In addition, the scaffold can provide electrical and electromechanical stimulation to the stem cells which are important external stimuli to stem cell differentiation. We tested the initial biocompatibility of these scaffolds using cardiac progenitor cells (CPCs), and continued onto more sensitive induced pluripotent stem cells (iPS). We present the fabrication and characterisation of these electroactive fibres as well as the response of increasingly sensitive cell types to the scaffolds.

High temperature polymer dielectric film-wire insulation

NASA Technical Reports Server (NTRS)

Nairus, John G.

1994-01-01

The highlights of the program are outlined including two major accomplishments. TRW identified and demonstrated the potential of two aromatic/heterocyclic polymers to have an outstanding and superior combination of electrical, thermal, and chemical resistance properties versus state-of-the-art Kapton for spacecraft and/or aircraft dielectric insulation applications. (Supporting data is provided in tables.) Feasibility was demonstrated for supporting/enabling technologies such as ceramic coatings, continuous film casting, and conductor wire wrapping, which are designed to accelerate qualification and deployment of the new wire insulation materials for USAF systems applications during the mid- to late-1990's.

Novel organic semiconductors and dielectric materials for high performance and low-voltage organic thin-film transistors

NASA Astrophysics Data System (ADS)

Yoon, Myung-Han

Two novel classes of organic semiconductors based on perfluoroarene/arene-modified oligothiophenes and perfluoroacyl/acyl-derivatized quaterthiophens are developed. The frontier molecular orbital energies of these compounds are studied by optical spectroscopy and electrochemistry while solid-state/film properties are investigated by thermal analysis, x-ray diffraction, and scanning electron microscopy. Organic thin film transistors (OTFTs) performance parameters are discussed in terms of the interplay between semiconductor molecular energetics and film morphologies/microstructures. For perfluoroarene-thiophene oligomer systems, majority charge carrier type and mobility exhibit a strong correlation with the regiochemistry of perfluoroarene incorporation. In quaterthiophene-based semiconductors, carbonyl-functionalization allows tuning of the majority carrier type from p-type to ambipolar and to n-type. In situ conversion of a p-type semiconducting film to n-type film is also demonstrated. Very thin self-assembled or spin-on organic dielectric films have been integrated into OTFTs to achieve 1 - 2 V operating voltages. These new dielectrics are deposited either by layer-by-layer solution phase deposition of molecular precursors or by spin-coating a mixture of polymer and crosslinker, resulting in smooth and virtually pinhole-free thin films having exceptionally large capacitances (300--700 nF/cm2) and low leakage currents (10 -9 - 10-7 A/cm2). These organic dielectrics are compatible with various vapor- or solution-deposited p- and n-channel organic semiconductors. Furthermore, it is demonstrated that spin-on crosslinked-polymer-blend dielectrics can be employed for large-area/patterned electronics, and complementary inverters. A general approach for probing semiconductor-dielectric interface effects on OTFT performance parameters using bilayer gate dielectrics is presented. Organic semiconductors having p-, n-type, or ambipolar majority charge carriers are grown on six different bilayer dielectrics consisting of various spin-coated polymers/HMDS on 300 nm SiO2/p+-Si, followed by transistor fabrication. In case of air-sensitive n-type semiconductors, dielectric surface modifications induce large variations in the corresponding OTFT performance parameters while film morphologies and microstructures remain unchanged. In contrast, the device performance of air-stable n-type and p-type semiconductors is not significantly affected by dielectric surface modifications. The origin of the mobility sensitivity to the various surface chemistries in the case of air sensitive n-type semiconductors is found to be due to electron trapping by silanol and carbonyl functionalities at the semiconductor-dielectric interface.

Aligned and Electrospun Piezoelectric Polymer Fiber Assembly and Scaffold

NASA Technical Reports Server (NTRS)

Holloway, Nancy M. (Inventor); Scott-Carnell, Lisa A. (Inventor); Siochi, Emilie J. (Inventor); Leong, Kam W. (Inventor); Kulangara, Karina (Inventor)

2015-01-01

A scaffold assembly and related methods of manufacturing and/or using the scaffold for stem cell culture and tissue engineering applications are disclosed which at least partially mimic a native biological environment by providing biochemical, topographical, mechanical and electrical cues by using an electroactive material. The assembly includes at least one layer of substantially aligned, electrospun polymer fiber having an operative connection for individual voltage application. A method of cell tissue engineering and/or stem cell differentiation uses the assembly seeded with a sample of cells suspended in cell culture media, incubates and applies voltage to one or more layers, and thus produces cells and/or a tissue construct. In another aspect, the invention provides a method of manufacturing the assembly including the steps of providing a first pre-electroded substrate surface; electrospinning a first substantially aligned polymer fiber layer onto the first surface; providing a second pre-electroded substrate surface; electrospinning a second substantially aligned polymer fiber layer onto the second surface; and, retaining together the layered surfaces with a clamp and/or an adhesive compound.

Aligned and Electrospun Piezoelectric Polymer Fiber Assembly and Scaffold

NASA Technical Reports Server (NTRS)

Kulangara, Karina (Inventor); Scott Carnell, Lisa A. (Inventor); Holloway, Nancy M. (Inventor); Leong, Kam W. (Inventor); Siochi, Emilie J. (Inventor)

2017-01-01

A method of manufacturing and/or using a scaffold assembly for stem cell culture and tissue engineering applications is disclosed. The scaffold at least partially mimics a native biological environment by providing biochemical, topographical, mechanical and electrical cues by using an electroactive material. The assembly includes at least one layer of substantially aligned, electrospun polymer fiber having an operative connection for individual voltage application. A method of cell tissue engineering and/or stem cell differentiation that uses the assembly seeded with a sample of cells suspended in cell culture media, incubates and applies voltage to one or more layers, and thus produces cells and/or a tissue construct. In another aspect, the invention provides a method of manufacturing the assembly including the steps of providing a first pre-electroded substrate surface; electrospinning a first substantially aligned polymer fiber layer onto the first surface; providing a second pre-electroded substrate surface; electrospinning a second substantially aligned polymer fiber layer onto the second surface; and, retaining together the layered surfaces with a clamp and/or an adhesive compound.

Conducting polymers with immobilised fibrillar collagen for enhanced neural interfacing.

PubMed

Liu, Xiao; Yue, Zhilian; Higgins, Michael J; Wallace, Gordon G

2011-10-01

Conducting polymers with pendant functionality are advantageous in various bionic and organic bioelectronic applications, as they allow facile incorporation of bio-regulative cues to provide bio-mimicry and conductive environments for cell growth, differentiation and function. In this work, polypyrrole substrates doped with chondroitin sulfate (CS), an extracellular matrix molecule bearing carboxylic acid moieties, were electrochemically synthesized and conjugated with type I collagen. During the coupling process, the conjugated collagen formed a 3-dimensional fibrillar matrix in situ at the conducting polymer interface, as evidenced by atomic force microscopy (AFM) and fluorescence microscopy under aqueous physiological conditions. Cyclic voltammetry (CV) and impedance measurement confirmed no significant reduction in the electroactivity of the fibrillar collagen-modified conducting polymer substrates. Rat pheochromocytoma (nerve) cells showed increased differentiation and neurite outgrowth on the fibrillar collagen, which was further enhanced through electrical stimulation of the underlying conducting polymer substrate. Our study demonstrates that the direct coupling of ECM components such as collagen, followed by their further self-assembly into 3-dimensional matrices, has the potential to improve the neural-electrode interface of implant electrodes by encouraging nerve cell attachment and differentiation. Copyright © 2011 Elsevier Ltd. All rights reserved.

Ras Labs-CASIS-ISS NL experiment for synthetic muscle returned to Earth: resistance to ionizing radiation

NASA Astrophysics Data System (ADS)

Rasmussen, Lenore; Albers, Leila N.; Rodriguez, Simone; Gentile, Charles; Meixler, Lewis D.; Ascione, George; Hitchner, Robert; Taylor, James; Hoffman, Dan; Cylinder, David; Gaza, Ramona; Moy, Leon; Mark, Patrick S.; Prillaman, Daniel L.; Nodarse, Robert; Menegus, Michael J.; Ratto, Jo Ann; Thellen, Christopher T.; Froio, Danielle; Valenza, Logan; Poirier, Catherine; Sinkler, Charles; Corl, Dylan; Hablani, Surbhi; Fuerst, Tyler; Gallucci, Sergio; Blocher, Whitney; Liffland, Stephanie

2017-04-01

In anticipation of deep space travel, new materials are being explored to assist and relieve humans in dangerous environments, such as high radiation, extreme temperature, and extreme pressure. Ras Labs Synthetic Muscle™ - electroactive polymers (EAPs) that contract and expand at low voltages - which mimic the unique gentle-yet-strong nature of human tissue, is a potential asset to manned space travel through protective gear and human assist robotics and for unmanned space exploration through deep space. Gen 3 Synthetic Muscle™ was proven to be resistant to extreme temperatures, and there were indications that these materials would also be radiation resistant. The purpose of the Ras Labs-CASIS-ISS Experiment was to test the radiation resistivity of the third and fourth generation of these EAPs, as well as to make them even more radiation resistant. On Earth, exposure of the Generation 3 and Generation 4 EAPs to a Cs-137 radiation source for 47.8 hours with a total dose of 305.931 kRad of gamma radiation was performed at the US Department of Energy's Princeton Plasma Physics Laboratory (PPPL) at Princeton University, followed by pH, peroxide, Shore Hardness durometer, and electroactivity testing to determine the inherent radiation resistivity of these contractile EAPs, and to determine whether the EAPs could be made even more radiation resistant through the application of appropriate additives and coatings. The on Earth preliminary tests determined that selected Ras Labs EAPs were not only inherently radiation resistant, but with the appropriate coatings and additives, could be made even more radiation resistant. G-force testing to over 10 G's was performed at US Army's ARDEC Labs, with excellent results, in preparation for space flight to the International Space Station National Laboratory (ISS-NL). Selected samples of Generation 3 and Generation 4 Synthetic Muscle™, with various additives and coatings, were launched to the ISS-NL on April 14, 2015 on the SpaceX CRS-6 payload, and after 1+ year space exposure, returned to Earth on May 11, 2016 on SpaceX CRS-8. The results were very good, with the survival of all flown samples, which compared very well with the ground control samples. The most significant change observed was color change (yellowing) in some of the flown EAP samples, which in polymers can be indicative of accelerated aging. While the Synthetic Muscle Experiment was in orbit on the ISS-NL, photo events occur every 4 to 6 weeks to observe any changes, such as color, in the samples. Both the 32 flown EAP samples and 32 ground control samples were tested for pH, material integrity, durometer, and electroactivity, with very good results. The samples were also analyzed using stereo microscopy, scanning electron microscopy (SEM)), and energy dispersive X-ray spectroscopy (EDS). Smart electroactive polymer based materials and actuators promise to transform prostheses and robots, allowing for the treatment, reduction, and prevention of debilitating injury and fatalities, and to further our exploration by land, sea, air, and space.

Ordered polymer nanofibers enhance output brightness in bilayer light-emitting field-effect transistors.

PubMed

Hsu, Ben B Y; Seifter, Jason; Takacs, Christopher J; Zhong, Chengmei; Tseng, Hsin-Rong; Samuel, Ifor D W; Namdas, Ebinazar B; Bazan, Guillermo C; Huang, Fei; Cao, Yong; Heeger, Alan J

2013-03-26

Polymer light emitting field effect transistors are a class of light emitting devices that reveal interesting device physics. Device performance can be directly correlated to the most fundamental polymer science. Control over surface properties of the transistor dielectric can dramatically change the polymer morphology, introducing ordered phase. Electronic properties such as carrier mobility and injection efficiency on the interface can be promoted by ordered nanofibers in the polymer. Moreover, by controlling space charge in the polymer interface, the recombination zone can be spatially extended and thereby enhance the optical output.

NMR Investigations of Structure and Dynamics in Polymers for Energy Storage Applications

NASA Astrophysics Data System (ADS)

Greenbaum, Steven

Materials innovation is needed to realize major progress in energy storage capacity for lithium batteries and capacitors. Polymers hold considerable promise as ion conducting media in batteries and electrochemical capacitors and as dielectrics in thin film capacitors. Structural studies of materials utilized in lithium battery technology are hampered by the lack of long-range order found in well-defined crystalline phases. Powder x-ray diffraction yields structural parameters that have been averaged over hundreds of lattice sites, and is unable to provide structural information about amorphous phases. Our laboratory uses solid state nuclear magnetic resonance (NMR) methods to investigate structural and chemical aspects of lithium ion cathodes, anodes, electrolytes, interfaces and interphases. NMR is element- (nuclear-) specific and sensitive to small variations in the immediate environment of the ions being probed, for example Li+, and in most cases is a reliably quantitative spectroscopy in that the integrated intensity of a particular spectral component is directly proportional to the number of nuclei in the corresponding material phase. NMR is also a powerful tool for probing ionic and molecular motion in lithium battery electrolytes with a dynamic range spanning some ten orders of magnitude through spin-lattice relaxation and self-diffusion measurements. Broadband relaxometry based on Fast Field Cycling NMR (FFCNMR) methods can span three to four of these orders of magnitude in a single set of measurements. Results of several recent NMR investigations performed on our lab will be presented. We explore the ion transport mechanism in polyether-based and lithium polymer electrolytes and those based on other base polymers, in particular, the extent to which ionic motion is coupled to polymer segmental motion. Polycarbonates are being considered as a possible replacement for polypropylene in high power thin film capacitors due to their favorable dielectric properties. We investigate the effects of incorporation of two types of additives in the polymer film on the ring-flip motions corresponding to the γ relaxation: (i) high dielectric constant ceramic particles; (ii) polar organic diluent molecules, The low frequency realm of broadband relaxometry allows meaningful comparison with dielectric relaxation studies of these samples performed by collaborators. Work Supported in part by the U.S. Office of Naval Research.

Glass transition and relaxation processes of nanocomposite polymer electrolytes.

PubMed

Money, Benson K; Hariharan, K; Swenson, Jan

2012-07-05

This study focus on the effect of δ-Al(2)O(3) nanofillers on the dc-conductivity, glass transition, and dielectric relaxations in the polymer electrolyte (PEO)(4):LiClO(4). The results show that there are three dielectric relaxation processes, α, β, and γ, in the systems, although the structural α-relaxation is hidden in the strong conductivity contribution and could therefore not be directly observed. However, by comparing an enhanced dc-conductivity, by approximately 2 orders of magnitude with 4 wt % δ-Al(2)O(3) added, with a decrease in calorimetric glass transition temperature, we are able to conclude that the dc-conductivity is directly coupled to the hidden α-relaxation, even in the presence of nanofillers (at least in the case of δ-Al(2)O(3) nanofillers at concentrations up to 4 wt %). This filler induced speeding up of the segmental polymer dynamics, i.e., the α-relaxation, can be explained by the nonattractive nature of the polymer-filler interactions, which enhance the "free volume" and mobility of polymer segments in the vicinity of filler surfaces.

Structural and optical characterization of PVA:KMnO4 based solid polymer electrolyte

NASA Astrophysics Data System (ADS)

Abdullah, Omed Gh.; Aziz, Shujahadeen B.; Rasheed, Mariwan A.

Solid polymer electrolyte films of polyvinyl alcohol (PVA) doped with a different weight percent of potassium permanganate (KMnO4) were prepared by standard solution cast method. XRD and FTIR techniques were performed for structural study. Complex formation between the PVA polymer and KMnO4 salt was confirmed by Fourier transform infrared (FTIR) spectroscopy. The description of crystalline nature of the solid polymer electrolyte films has been confirmed by XRD analysis. The UV-Visible absorption spectra were analyzed in terms of absorption formula for non-crystalline materials. The fundamental optical parameters such as optical band gap energy, refractive index, optical conductivity, and dielectric constants have been investigated and showed a clear dependence on the KMnO4 concentration. The observed value of optical band gap energy for pure PVA is about 6.27 eV and decreases to a value 3.12 eV for the film sample formed with 4 wt% KMnO4 salt. The calculated values of refractive index and the dielectric constants of the polymer electrolyte films increase with increasing KMnO4 content.

Dielectric Elastomers for Fluidic and Biomedical Applications

NASA Astrophysics Data System (ADS)

McCoul, David James

Dielectric elastomers have demonstrated tremendous potential as high-strain electromechanical transducers for a myriad of novel applications across all engineering disciplines. Because their soft, viscoelastic mechanical properties are similar to those of living tissues, dielectric elastomers have garnered a strong foothold in a plethora of biomedical and biomimetic applications. Dielectric elastomers consist of a sheet of stretched rubber, or elastomer, coated on both sides with compliant electrode materials; application of a voltage generates an electrostatic pressure that deforms the elastomer. They can function as soft generators, sensors, or actuators, and this last function is the focus of this dissertation. Many design configurations are possible, such as stacks, minimum energy structures, interpenetrating polymer networks, shape memory dielectric elastomers, and others; dielectric elastomers are already being applied to many fields of biomedicine. The first part of the original research presented in this dissertation details a PDMS microfluidic system paired with a dielectric elastomer stack actuator of anisotropically prestrained VHB(TM) 4910 (3M(TM)) and single-walled carbon nanotubes. These electroactive microfluidic devices demonstrated active increases in microchannel width when 3 and 4 kV were applied. Fluorescence microscopy also indicated an accompanying increase in channel depth with actuation. The cross-sectional area strains at 3 and 4 kV were approximately 2.9% and 7.4%, respectively. The device was then interfaced with a syringe pump, and the pressure was measured upstream. Linear pressure-flow plots were developed, which showed decreasing fluidic resistance with actuation, from 0.192 psi/(microL/min) at 0 kV, to 0.160 and 0.157 psi/(microL/min) at 3 and 4 kV, respectively. This corresponds to an ~18% drop in fluidic resistance at 4 kV. Active de-clogging was tested in situ with the device by introducing ~50 microm diameter PDMS microbeads and other smaller particulate debris into the system. After a channel blockage was confirmed, three actuation attempts successfully cleared the blockage. Further tests indicated that the device were biocompatible with HeLa cells at 3 kV. To our knowledge this is the first pairing of dielectric elastomers with microfluidics in a non-electroosmotic context. Applications may include adaptive microfilters, micro-peristaltic pumps, and reduced-complexity lab-on-a-chip devices. Dielectric elastomers can also be adapted to manipulate fluidic systems on a larger scale. The second part of the dissertation research reports a novel low-profile, biomimetic dielectric elastomer tubular actuator capable of actively controlling hydraulic flow. The tubular actuator has been established as a reliable tunable valve, pinching a secondary silicone tube completely shut in the absence of a fluidic pressure bias or voltage, offering a high degree of resistance against fluidic flow, and able to open and completely remove this resistance to flow with an applied low power actuation voltage. The system demonstrates a rise in pressure of ~3.0 kPa when the dielectric elastomer valve is in the passive, unactuated state, and there is a quadratic fall in this pressure with increasing actuation voltage, until ~0 kPa is reached at 2.4 kV. The device is reliable for at least 2,000 actuation cycles for voltages at or below 2.2 kV. Furthermore, modeling of the actuator and fluidic system yields results consistent with the observed experimental dependence of intrasystem pressure on input flow rate, actuator prestretch, and actuation voltage. To our knowledge, this is the first actuator of its type that can control fluid flow by directly actuating the walls of a tube. Potential applications may include an implantable artificial sphincter, part of a peristaltic pump, or a computerized valve for fluidic or pneumatic control. The final part of the dissertation presents a novel dielectric elastomer band with integrated rigid elements for the treatment of chronic acid reflux disorders. This dielectric elastomer ring actuator consists of a two-layer stack of prestretched VHB(TM) 4905 with SWCNT electrodes. Its transverse prestretch was maintained by selective rigidification of the VHB(TM) using a UV-curable, solution-processable polymer network. The actuator exhibited a maximum vertical (circumferential) actuation strain of 25% at 3.4 kV in an 24.5 g weighted isotonic setup. It also exhibited the required passive force of 0.25 N and showed a maximum force drop of 0.11 N at 3.32 kV during isometric tests at 4.5 cm. Modeling was performed to determine the prestretches necessary to achieve maximum strain while simultaneously exerting the force of 0.25 N, which corresponds to a required pinching pressure of 3.35 kPa. Modeling also determined the spacing between and number of rigid elements required. The theoretical model curves were adjusted to account for the passive rigid elements, as well as for the addition of margins; the resulting plots agrees well with experiment. The performance of the DE band is comparable to that of living muscle, and this is the first application of dielectric elastomer actuators in the design of a medical implant for the treatment of gastrointestinal disorders. Related applications that could result from this technology are very low-profile linear peristaltic pumps, artificial intestines, an artificial urethra, and artificial blood vessels.

The effect of MRET polymer compound on SAR values of RF phones.

PubMed

Smirnov, Igor

2008-01-01

This article is related to the proposed hypothesis and experimental data regarding the ability of defined polar polymer compound (MRET polymer) applied to RF phones to increase the dielectric permittivity of water based solutions and to reduce the SAR (Specific Absorption Rate) values inside the "phantom head" filled with the jelly simulating muscle and brain tissues. Due to the high organizational state of fractal structures of MRET polymer compounds and the phenomenon of piezoelectricity, this polymer generates specific subtle, low frequency, non-coherent electromagnetic oscillations (optimal random field) that can affect the hydrogen lattice of the molecular structure of water and subsequently modify the electrodynamic properties of water. The increase of dielectric permittivity of water finally leads to the reduction of the absorption rate of the electromagnetic field by living tissue. The reduction of SAR values is confirmed by the research conducted in June - July of 2006 at RF Exposure Laboratory in Escondido, California. This test also confirmed that the application of MRET polymer to RF phones does not significantly affect the air measurements of RF phone signals, and subsequently does not lead to any significant distortion of transmitted RF signals.

Enhanced Thermal Conductivity and Dielectric Properties of Iron Oxide/Polyethylene Nanocomposites Induced by a Magnetic Field.

PubMed

Chi, Qingguo; Ma, Tao; Dong, Jiufeng; Cui, Yang; Zhang, Yue; Zhang, Changhai; Xu, Shichong; Wang, Xuan; Lei, Qingquan

2017-06-08

Iron Oxide (Fe 3 O 4 ) nanoparticles were deposited on the surface of low density polyethylene (LDPE) particles by solvothermal method. A magnetic field was introduced to the preparation of Fe 3 O 4 /LDPE composites, and the influences of the magnetic field on thermal conductivity and dielectric properties of composites were investigated systematically. The Fe 3 O 4 /LDPE composites treated by a vertical direction magnetic field exhibited a high thermal conductivity and a large dielectric constant at low filler loading. The enhancement of thermal conductivity and dielectric constant is attributed to the formation of the conductive chains of Fe 3 O 4 in LDPE matrix under the action of the magnetic field, which can effectively enhance the heat flux and interfacial polarization of the Fe 3 O 4 /LDPE composites. Moreover, the relatively low dielectric loss and low conductivity achieved are attributed to the low volume fraction of fillers and excellent compatibility between Fe 3 O 4 and LDPE. Of particular note is the dielectric properties of Fe 3 O 4 /LDPE composites induced by the magnetic field also retain good stability across a wide temperature range, and this contributes to the stability and lifespan of polymer capacitors. All the above-mentioned properties along with the simplicity and scalability of the preparation for the polymer nanocomposites make them promising for the electronics industry.

Characterization of bending EAP beams

NASA Technical Reports Server (NTRS)

Bao, Xiaoqi; Bar-Cohen, Yoseph; Chang, Zensheu; Sherrit, Stewart

2004-01-01

Electroactive polymers are attractive actuation materials because of their large deformation, flexibility, and lightweight. A CCD camera system was constructed to record the curved shapes of bending during the activation of EAP films and image-processing software was developed to digitize the bending curves. A computer program was developed to solve the invese problem of cantilever EAP beams with tip position limiter. using the developed program and acquired curves without tip position limiter as well as the corresponding tip force, the EAP material properties of voltage-strain sensitivity and Young's modulus were determined.

Electrochemical supercapacitors from conducting polyaniline-graphene platforms.

PubMed

Ashok Kumar, Nanjundan; Baek, Jong-Beom

2014-06-18

Energy storage devices such as electrochemical supercapacitors, with high power and energy densities are required to address the colossal energy requirements against the backdrop of global warming and the looming energy crisis. Nanocarbon, particularly two-dimensional graphene and graphene-based conducting polymer composites are promising electrode materials for such energy storage devices. Owing to their environmental stability, the low cost of polymers with high electroactivity and pseudocapacitance, such composite hybrids are expected to have wide implications in next generation clean and efficient energy systems. In this feature article, an overview of current research and important advances over the past four years on the development of conducting polyaniline (PANI)-graphene based composite electrodes for electrochemical supercapacitors are highlighted. Particular emphasis is made on the design, fabrication and assembly of nanostructured electrode architectures comprising PANI and graphene along with metal oxides/hydroxides and carbon nanotubes. Comments on the challenges and perspectives towards rational design and synthesis of graphene-based conducting polymer composites for energy storage are discussed.

Minimizing analyte electrolysis in electrospray ionization mass spectrometry using a redox buffer coated emitter electrode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peintler-Krivan, Emese; Van Berkel, Gary J; Kertesz, Vilmos

2010-01-01

An emitter electrode with an electroactive poly(pyrrole) (PPy) polymer film coating was constructed for use in electrospray ionization mass spectrometry (ESI-MS). The PPy film acted as a surface-attached redox buffer limiting the interfacial potential of the emitter electrode. While extensive oxidation of selected analytes (reserpine and amodiaquine) was observed in positive ion mode ESI using a bare metal (gold) emitter electrode, the oxidation was suppressed for these same analytes when using the PPy-coated electrode. A semi-quantitative relationship between the rate of oxidation observed and the interfacial potential of the emitter electrode was shown. The redox buffer capacity, and therefore themore » lifetime of the redox buffering effect, correlated with the oxidation potential of the analyte and with the magnitude of the film charge capacity. Online reduction of the PPy polymer layer using negative ion mode ESI between analyte injections was shown to successfully restore the redox buffering capacity of the polymer film to its initial state.« less

Electro-Statically Stricted Polymers (ESSP)

NASA Technical Reports Server (NTRS)

Liu, C.; Bar-Cohen, Y.; Leary, S.

1999-01-01

Miniature, lightweight, miser actuators that operate similar to biological muscles can be used to develop robotic devices with unmatched capabilities and impact many technology areas. Electroactive polymers (EAP) offer the potential to producing such actuators and their main attractive feature is their ability to induce relatively large bending or longitudinal strain. EAP actuators can change the paradigm about the complexity of robots, where robotic components such as motors, gears, bearings, and others can be eliminated with simple drive mechanisms. Generally, these materials produce a relatively low force and the applications that can be considered at the current state of the art are relatively limited. While improved material are being developed there is a need for methods to develop longitudinal actuators that can contract similar to muscles. In this study, the authors began investigating the electromechanical behavior of polymers in reaction to a complex configuration of electric fields. A computer model was used to simulate the electromechanical response. Efforts were made to develop both the material basis as well as the electromechanical modeling of the actuator.

Behavior of ionic conducting IPN actuators in simulated space conditions

NASA Astrophysics Data System (ADS)

Fannir, Adelyne; Plesse, Cédric; Nguyen, Giao T. M.; Laurent, Elisabeth; Cadiergues, Laurent; Vidal, Frédéric

2016-04-01

The presentation focuses on the performances of flexible all-polymer electroactive actuators under space-hazardous environmental factors in laboratory conditions. These bending actuators are based on high molecular weight nitrile butadiene rubber (NBR), poly(ethylene oxide) (PEO) derivative and poly(3,4-ethylenedioxithiophene) (PEDOT). The electroactive PEDOT is embedded within the PEO/NBR membrane which is subsequently swollen with an ionic liquid as electrolyte. Actuators have been submitted to thermal cycling test between -25 to 60°C under vacuum (2.4 10-8 mbar) and to ionizing Gamma radiations at a level of 210 rad/h during 100 h. Actuators have been characterized before and after space environmental condition ageing. In particular, the viscoelasticity properties and mechanical resistance of the materials have been determined by dynamic mechanical analysis and tensile tests. The evolution of the actuation properties as the strain and the output force have been characterized as well. The long-term vacuuming, the freezing temperature and the Gamma radiations do not affect significantly the thermomechanical properties of conducting IPNs actuators. Only a slight decrease on actuation performances has been observed.

An ionic electro-active actuator made with graphene film electrode, chitosan and ionic liquid

NASA Astrophysics Data System (ADS)

He, Qingsong; Yu, Min; Yang, Xu; Kim, Kwang Jin; Dai, Zhendong

2015-06-01

A newly developed ionic electro-active actuator composed of an ionic electrolyte layer sandwiched between two graphene film layers was investigated. Scanning electronic microscopy observation and x-ray diffraction analysis showed that the graphene sheets in the film stacked in a nearly face-to-face fashion but did not restack back to graphite, and the resulting graphene film with low sheet resistance (10 Ω sq-1) adheres well to the electrolyte membrane. Contact angle measurement showed the surface energy (37.98 mJ m-2) of the ionic electrolyte polymer is 2.67 times higher than that (14.2 mJ m-2) of the Nafion membrane, contributing to the good adhesion between the graphene film electrode and the electrolyte membrane. An electric double-layer is formed at the interface between the graphene film electrode and the ionic electrolyte membrane under the input potential, resulting in a higher capacitance of 27.6 mF cm-2. We report that this ionic actuator exhibits adequate bending strain, ranging from 0.032 to 0.1% (305 to 945 μm) as functions of voltage.

Characterization of stable, electroactive protein cage/synthetic polymer multilayer thin films prepared by layer-by-layer assembly

NASA Astrophysics Data System (ADS)

Uto, Koichiro; Yamamoto, Kazuya; Kishimoto, Naoko; Muraoka, Masahiro; Aoyagi, Takao; Yamashita, Ichiro

2013-04-01

We have fabricated electroactive multilayer thin films containing ferritin protein cages. The multilayer thin films were prepared on a solid substrate by the alternate electrostatic adsorption of (apo)ferritin and poly( N-isopropylacrylamide- co-2-carboxyisopropylacrylamide) (NIPAAm- co-CIPAAm) in pH 3.5 acetate buffer solution. The assembly process was monitored using a quartz crystal microbalance. The (apo)ferritin/poly(NIPAAm- co-CIPAAm) multilayer thin films were then cross-linked using a water-soluble carbodiimide, 1-[3-(dimethylamino)propyl]-3-ethylcarbodiimide. The cross-linked films were stable under a variety of conditions. The surface morphology and thickness of the multilayer thin films were characterized by atomic force microscopy, and the ferritin iron cores were observed by scanning electron microscopy to confirm the assembly mechanism. Cyclic voltammetry measurements showed different electrochemical properties for the cross-linked ferritin and apoferritin multilayer thin films, and the effect of stability of the multilayer film on its electrochemical properties was also examined. Our method for constructing multilayer films containing protein cages is expected to be useful in building more complex functional inorganic nanostructures.

Surface-modified multifunctional MIP nanoparticles

NASA Astrophysics Data System (ADS)

Moczko, Ewa; Poma, Alessandro; Guerreiro, Antonio; Perez de Vargas Sansalvador, Isabel; Caygill, Sarah; Canfarotta, Francesco; Whitcombe, Michael J.; Piletsky, Sergey

2013-04-01

The synthesis of core-shell molecularly imprinted polymer nanoparticles (MIP NPs) has been performed using a novel solid-phase approach on immobilised templates. The same solid phase also acts as a protective functionality for high affinity binding sites during subsequent derivatisation/shell formation. This procedure allows for the rapid synthesis, controlled separation and purification of high-affinity materials, with each production cycle taking just 2 hours. The aim of this approach is to synthesise uniformly sized imprinted materials at the nanoscale which can be readily grafted with various polymers without affecting their affinity and specificity. For demonstration purposes we grafted anti-melamine MIP NPs with coatings which introduce the following surface characteristics: high polarity (PEG methacrylate); electro-activity (vinylferrocene); fluorescence (eosin acrylate); thiol groups (pentaerythritol tetrakis(3-mercaptopropionate)). The method has broad applicability and can be used to produce multifunctional imprinted nanoparticles with potential for further application in the biosensors, diagnostics and biomedical fields and as an alternative to natural receptors.The synthesis of core-shell molecularly imprinted polymer nanoparticles (MIP NPs) has been performed using a novel solid-phase approach on immobilised templates. The same solid phase also acts as a protective functionality for high affinity binding sites during subsequent derivatisation/shell formation. This procedure allows for the rapid synthesis, controlled separation and purification of high-affinity materials, with each production cycle taking just 2 hours. The aim of this approach is to synthesise uniformly sized imprinted materials at the nanoscale which can be readily grafted with various polymers without affecting their affinity and specificity. For demonstration purposes we grafted anti-melamine MIP NPs with coatings which introduce the following surface characteristics: high polarity (PEG methacrylate); electro-activity (vinylferrocene); fluorescence (eosin acrylate); thiol groups (pentaerythritol tetrakis(3-mercaptopropionate)). The method has broad applicability and can be used to produce multifunctional imprinted nanoparticles with potential for further application in the biosensors, diagnostics and biomedical fields and as an alternative to natural receptors. Electronic supplementary information (ESI) available: Details of the synthesis of eosin O-acrylate monomer and 1H-NMR spectrum of MIP NPs post-derivatised with PEG shell. See DOI: 10.1039/c3nr00354j

Effects of Radiation on Capacitor Dielectrics

NASA Technical Reports Server (NTRS)

Bouquet, F. L.; Somoano, R. B.; Frickland, P. O.

1987-01-01

Data gathered on key design parameters. Report discusses study of electrical and mechanical properties of irradiated polymer dielectric materials. Data compiled for use by designers of high-energy-density capacitors that operate in presence of ionizing radiation. Study focused on polycarbonates, polyetheretherketones, polymethylpentenes, polyimides (including polyetherimide), polyolefins, polysulfones (including polyethersulfone and polyphenylsulfone), and polyvinylidene fluorides.

Dielectric properties of magnetorheological elastomers with different microstructure

NASA Astrophysics Data System (ADS)

Moucka, R.; Sedlacik, M.; Cvek, M.

2018-03-01

Composite materials containing magnetic particles organised within the polymer matrix by the means of an external magnetic field during the curing process were prepared, and their dielectric properties were compared with their isotropic analogues of the same filler concentration but homogeneous spatial distribution. A substantial dielectric response observed for anisotropic systems in a form of relaxation processes was explained as charge transport via the mechanism of variable range hopping. The changes in registered relaxations' critical frequency and shape of dielectric spectra with the filler concentration were discussed in terms of decreasing anisotropy of the system. The knowledge of the dielectric response of studied systems is essential for their practical applications such as piezoresistive sensors or radio-absorbing materials.

Effect of methyl red dye on dielectric and conductivity properties of PEO/CdCl{sub 2} electrolytes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kamath, Archana; Devendrappa, H., E-mail: dehu2010@gmail.com

2016-05-06

In this report the conductivity and dielectric properties of polyethylene oxide-cadmium chloride (PEO/CdCl{sub 2}) polymer electrolyte films doped with an azo dye methyl red (MR) are discussed. The films were prepared by solution casting technique at different concentrations of the dye in PEO/CdCl{sub 2} electrolyte. The thermal behavior, chemical interaction of the dye with the electrolyte and surface morphology were studied by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) respectively. The conductivity and dielectric properties were measured as a function of composition and temperature using complex impedance spectroscopy. The temperature dependent electrical conductivitymore » of the films exhibited Arrhenius type behavior. Conductivity and dielectric results also signify the enhancement in the amorphous phase of the polymer electrolyte dye systems. The value of highest conductivity observed is 1.21x10{sup −4} at 343K and the conductivity of the film was enhanced by a three orders of magnitude.« less

Optical and Electrical Characteristics of Silver Ion Conducting Nanocomposite Solid Polymer Electrolytes Based on Chitosan

NASA Astrophysics Data System (ADS)

Aziz, Shujahadeen B.; Rasheed, Mariwan A.; Abidin, Zul H. Z.

2017-10-01

Optical and electrical properties of nanocomposite solid polymer electrolytes based on chitosan have been investigated. Incorporation of alumina nanoparticles into the chitosan:silver triflate (AgTf) system broadened the surface plasmon resonance peaks of the silver nanoparticles and shifted the absorption edge to lower photon energy. A clear decrease of the optical bandgap in nanocomposite samples containing alumina nanoparticles was observed. The variation of the direct-current (DC) conductivity and dielectric constant followed the same trend with alumina concentration. The DC conductivity increased by two orders of magnitude, which can be attributed to hindrance of silver ion reduction. Transmission electron microscopy was used to interpret the space-charge and blocking effects of alumina nanoparticles on the DC conductivity and dielectric constant. The ion conduction mechanism was interpreted based on the dependences of the electrical and dielectric parameters. The dependence of the DC conductivity on the dielectric constant is explained empirically. Relaxation processes associated with conductivity and viscoelasticity were distinguished based on the incomplete semicircular arcs in plots of the real and imaginary parts of the electric modulus.

Local Dielectric Property Detection of the Interface between Nanoparticle and Polymer in Nanocomposite Dielectrics

NASA Astrophysics Data System (ADS)

Peng, Simin; Zeng, Qibin; Yang, Xiao; Hu, Jun; Qiu, Xiaohui; He, Jinliang

2016-12-01

The interface between nanoparticles and polymer matrix is considered to have an important effect on the properties of nanocomposites. In this experimental study, electrostatic force microscopy (EFM) is used to study the local dielectric property of the interface of low density polyethylene (LDPE)/TiO2 nanocomposites at nanometer scale. The results show that the addition of TiO2 nanoparticles leads to a decrease in local permittivity. We then carry out the finite element simulation and confirm that the decrease of local permittivity is related to the effect of interface. According to the results, we propose several models and validate the dielectric effect and range effect of interface. Through the analysis of DSC and solid-state NMR results, we find TiO2 nanoparticles can suppress the mobility of local chain segments in the interface, which influences the dipolar polarization of chain segments in the interface and eventually results in a decrease in local permittivity. It is believed the results would provide important hint to the research of the interface in future research.

Local Dielectric Property Detection of the Interface between Nanoparticle and Polymer in Nanocomposite Dielectrics

PubMed Central

Peng, Simin; Zeng, Qibin; Yang, Xiao; Hu, Jun; Qiu, Xiaohui; He, Jinliang

2016-01-01

The interface between nanoparticles and polymer matrix is considered to have an important effect on the properties of nanocomposites. In this experimental study, electrostatic force microscopy (EFM) is used to study the local dielectric property of the interface of low density polyethylene (LDPE)/TiO2 nanocomposites at nanometer scale. The results show that the addition of TiO2 nanoparticles leads to a decrease in local permittivity. We then carry out the finite element simulation and confirm that the decrease of local permittivity is related to the effect of interface. According to the results, we propose several models and validate the dielectric effect and range effect of interface. Through the analysis of DSC and solid-state NMR results, we find TiO2 nanoparticles can suppress the mobility of local chain segments in the interface, which influences the dipolar polarization of chain segments in the interface and eventually results in a decrease in local permittivity. It is believed the results would provide important hint to the research of the interface in future research. PMID:27958347

Design, fabrication, and properties of 2-2 connectivity cement/polymer based piezoelectric composites with varied piezoelectric phase distribution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dongyu, Xu; Department of Mechanical Engineering, University of South Carolina, Columbia, South Carolina 29208; Xin, Cheng

2014-12-28

The laminated 2-2 connectivity cement/polymer based piezoelectric composites with varied piezoelectric phase distribution were fabricated by employing Lead Zirconium Titanate ceramic as active phase, and mixture of cement powder, epoxy resin, and hardener as matrix phase with a mass proportion of 4:4:1. The dielectric, piezoelectric, and electromechanical coupling properties of the composites were studied. The composites with large total volume fraction of piezoelectric phase have large piezoelectric strain constant and relative permittivity, and the piezoelectric and dielectric properties of the composites are independent of the dimensional variations of the piezoelectric ceramic layer. The composites with small total volume fraction ofmore » piezoelectric phase have large piezoelectric voltage constant, but also large dielectric loss. The composite with gradually increased dimension of piezoelectric ceramic layer has the smallest dielectric loss, and that with the gradually increased dimension of matrix layer has the largest piezoelectric voltage constant. The novel piezoelectric composites show potential applications in fabricating ultrasonic transducers with varied surface vibration amplitude of the transducer.« less

Temperature characterization of dielectric permittivity and AC conductivity of nano copper oxide-doped polyaniline composite

NASA Astrophysics Data System (ADS)

Shubha, L. N.; Madhusudana Rao, P.

2016-06-01

The polyaniline/copper oxide (PANI/CuO) nanocomposite was prepared by mixing solutions of polyaniline and copper oxide nanoparticles in dimethyl sulfoxide (DMSO). The synthesized polymer nanocomposites were characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM) and UV-visible spectroscopy. The characteristic peaks in XRD and UV-visible spectra confirmed the presence of CuO in the polymer structure. SEM images indicated morphological changes in the composite matrix as compared to the pristine PANI. The DC conductivity measurements were performed using two-probe method for various temperatures. AC conductivity and dielectric response of the composites were investigated in the frequency range of 102-106Hz using LCR meter. Dielectric permittivity ɛ‧(w) and dielectric loss factor ɛ‧‧(w) were investigated. It was observed that ɛ‧(w) and ɛ‧‧(w) decrease with increase in frequency at all temperatures. At a particular frequency it is observed that both ɛ‧(w) and ɛ‧‧(w) increase with increase in temperature. It was also observed that AC conductivity increased with increase in frequency and temperature.

High-Temperature and High-Energy-Density Dipolar Glass Polymers Based on Sulfonylated Poly(2,6-dimethyl-1,4-phenylene oxide).

PubMed

Zhang, Zhongbo; Wang, David H; Litt, Morton H; Tan, Loon-Seng; Zhu, Lei

2018-02-05

A new class of high-temperature dipolar polymers based on sulfonylated poly(2,6-dimethyl-1,4-phenylene oxide) (SO 2 -PPO) was synthesized by post-polymer functionalization. Owing to the efficient rotation of highly polar methylsulfonyl side groups below the glass transition temperature (T g ≈220 °C), the dipolar polarization of these SO 2 -PPOs was enhanced, and thus the dielectric constant was high. Consequently, the discharge energy density reached up to 22 J cm -3 . Owing to its high T g  , the SO 2 -PPO 25 sample also exhibited a low dielectric loss. For example, the dissipation factor (tan δ) was 0.003, and the discharge efficiency at 800 MV m -1 was 92 %. Therefore, these dipolar glass polymers are promising for high-temperature, high-energy-density, and low-loss electrical energy storage applications. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Current State of Silicone-Based Dielectric Elastomer Transducers.

PubMed

Madsen, Frederikke B; Daugaard, Anders E; Hvilsted, Søren; Skov, Anne L

2016-03-01

Silicone elastomers are promising materials for dielectric elastomer transducers (DETs) due to their superior properties such as high efficiency, reliability and fast response times. DETs consist of thin elastomer films sandwiched between compliant electrodes, and they constitute an interesting class of transducer due to their inherent lightweight and potentially large strains. For the field to progress towards industrial implementation, a leap in material development is required, specifically targeting longer lifetime and higher energy densities to provide more efficient transduction at lower driving voltages. In this review, the current state of silicone elastomers for DETs is summarised and critically discussed, including commercial elastomers, composites, polymer blends, grafted elastomers and complex network structures. For future developments in the field it is essential that all aspects of the elastomer are taken into account, namely dielectric losses, lifetime and the very often ignored polymer network integrity and stability. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

New three-phase polymer-ceramic composite materials for miniaturized microwave antennas

NASA Astrophysics Data System (ADS)

Zhang, Li; Zhang, Jie; Yue, Zhenxing; Li, Longtu

2016-09-01

Unique polymer-ceramic composites for microwave antenna applications were prepared via melt extrusion using high-density polyethylene (HDPE) as the matrix and low-density polyethylene (LDPE) coated BaO-Nd2O3-TiO2 (BNT) ceramic-powders as the filler. By incorporating LDPE into the composites via a coating route, high ceramic-powder volume content (up to 50 vol%) could be achieved. The composites exhibited good microwave dielectric and thermomechanical behaviors. As BNT ceramic content increased from 10 vol% to 50 vol%, the permittivity of the composites increased from 3.45 (9 GHz) to 11.87 (7 GHz), while the dielectric loss remained lower than 0.0016. Microstrip antennas for applications in global positioning systems (GPS) were designed and fabricated from the composites containing 50 vol% BNT ceramics. The results indicate that the composites that have suitable permittivity and low dielectric loss are promising candidates for applications in miniaturized microwave devices, such as antennas.

Polymer (PDMS-Fe3O4) magneto-dielectric substrate for a MIMO antenna array

NASA Astrophysics Data System (ADS)

Alqadami, Abdulrahman Shueai Mohsen; Jamlos, Mohd Faizal; Soh, Ping Jack; Kamarudin, Muhammad Ramlee

2016-01-01

This paper presents the design of a 2 × 4 multiple-input multiple-output (MIMO) antenna array fabricated on a nanocomposite magneto-dielectric polymer substrate. The 10-nm iron oxide (Fe3O4) nanoparticles and polydimethylsiloxane (PDMS) composite is used as substrate to enhance the performance of a MIMO antenna array. The measured results showed up to 40.8 % enhancement in terms of bandwidth, 9.95 dB gain, and 57 % of radiation efficiency. Furthermore, it is found that the proposed magneto-dielectric (PDMS-Fe3O4) composite substrate provides excellent MIMO parameters such as correlation coefficient, diversity gain, and mutual coupling. The prototype of the proposed antenna is transparent, flexible, lightweight, and resistant against dust and corrosion. Measured results indicate that the proposed antenna is suitable for WLAN and ultra-wideband biomedical applications within frequency range of 5.33-7.70 GHz.

High dielectric constant and energy density induced by the tunable TiO2 interfacial buffer layer in PVDF nanocomposite contained with core-shell structured TiO2@BaTiO3 nanoparticles

NASA Astrophysics Data System (ADS)

Hu, Penghao; Jia, Zhuye; Shen, Zhonghui; Wang, Peng; Liu, Xiaoru

2018-05-01

To realize application in high-capacity capacitors and portable electric devices, large energy density is eagerly desired for polymer-based nanocomposite. The core-shell structured nanofillers with inorganic buffer layer are recently supposed to be promising in improving the dielectric property of polymer nanocomposite. In this work, core-shell structured TO@BT nanoparticles with crystalline TiO2 buffer layer coated on BaTiO3 nanoparticle were fabricated via solution method and heat treatment. The thickness of the TO buffer layer can be tailored by modulating the additive amount of the titanate coupling agent in preparation process, and the apparent dielectric properties of nanocomposite are much related to the thickness of the TO layer. The relatively thin TO layer prefer to generate high polarization to increase dielectric constant while the relatively thick TO layer would rather to homogenize field to maintain breakdown strength. Simulation of electric field distribution in the interfacial region reveals the improving effect of the TO buffer layer on the dielectric properties of nanocomposite which accords with the experimental results well. The optimized nanoparticle TO@BT-2 with a mean thickness of 3-5 nm buffer layer of TO is effective in increasing both the ε and Eb in the PVDF composite film. The maximal discharged energy density of 8.78 J/cm3 with high energy efficiency above 0.6 is obtained in TO@BT-2/PVDF nanocomposite with 2.5 vol% loading close to the breakdown strength of 380 kV/mm. The present study demonstrates the approach to optimize the structure of core-shell nanoparticles by modulating buffer layer and provides a new way to further enlarge energy density in polymer nanocomposite.

Synthesis and Characterization of High-Dielectric-Constant Nanographite-Polyurethane Composite

NASA Astrophysics Data System (ADS)

Mishra, Praveen; Bhat, Badekai Ramachandra; Bhattacharya, B.; Mehra, R. M.

2018-05-01

In the face of ever-growing demand for capacitors and energy storage devices, development of high-dielectric-constant materials is of paramount importance. Among various dielectric materials available, polymer dielectrics are preferred for their good processability. We report herein synthesis and characterization of nanographite-polyurethane composite with high dielectric constant. Nanographite showed good dispersibility in the polyurethane matrix. The thermosetting nature of polyurethane gives the composite the ability to withstand higher temperature without melting. The resultant composite was studied for its dielectric constant (ɛ) as a function of frequency. The composite exhibited logarithmic variation of ɛ from 3000 at 100 Hz to 225 at 60 kHz. The material also exhibited stable dissipation factor (tan δ) across the applied frequencies, suggesting its ability to resist current leakage.

Thermally Stable, Piezoelectric and Pyroelectric Polymeric Substrates and Method Relating Thereto

NASA Technical Reports Server (NTRS)

Simpson, Joycelyn O. (Inventor); St.Clair, Terry L. (Inventor)

1995-01-01

Production of an electric voltage in response to mechanical excitation (piezoelectricity) or thermal excitation (pyroelectricity) requires a material to have a preferred dipole orientation in its structure. This preferred orientation or polarization occurs naturally in some crystals such as quartz and can be induced into some ceramic and polymeric materials by application of strong electric or mechanical fields. For some materials, a combination of mechanical and electrical orientation is necessary to completely polarize the material. The only commercially available piezoelectric polymer is poly(vinylidene fluoride) (PVF2). However, this polymer has material and process limitations which prohibit its use in numerous device applications where thermal stability is a requirement. By the present invention, thermally stable, piezoelectric and pyroelectric polymeric substrates were prepared from polymers having a softening temperature greater than 1000C. A metal electrode material is deposited onto the polymer substrate and several electrical leads are attached to it. The polymer substrate is heated in a low dielectric medium to enhance molecular mobility of the polymer chains. A voltage is then applied to the polymer substrate inducing polarization. The voltage is then maintained while the polymer substrate is cooled 'freezing in' the molecular orientation. The novelty of the invention resides in the process of preparing the piezoelectric and pyroelectric polymeric substrate. The nonobviousness of the invention is found in heating the polymeric substrate in a low dielectric medium while applying a voltage.

Plasma treatment of polyethylene tubes in continuous regime using surface dielectric barrier discharge with water electrodes

NASA Astrophysics Data System (ADS)

Galmiz, Oleksandr; Zemánek, Miroslav; Pavliňák, David; Černák, Mirko

2018-05-01

Combining the surface dielectric barrier discharges generated in contact with water based electrolytes, as the discharge electrodes, we have designed a new type of surface electric discharge, generating thin layers of plasma which propagate along the treated polymer surfaces. The technique was aimed to achieve uniform atmospheric pressure plasma treatment of polymeric tubes and other hollow bodies. The results presented in this work show the possibility of such system to treat outer surface of polymer materials in a continuous mode. The technical details of experimental setup are discussed as well as results of treatment of polyethylene tubes are shown.

Deep-Blue Fluorescent Particles via Microwave Heating of Polyacrylonitrile Dispersions.

PubMed

Go, Dennis; Jurásková, Alena; Hoffmann, Andreas; Kapiti, Gent; Kuehne, Alexander J C

2017-03-01

This study presents a new method to produce fluorescent particles. Established methods are based on the incorporation of conjugated dye molecules into dielectric polymer matrices or preparation of colloids, which are composed of fluorescent conjugated polymer. By contrast, this study presents a method where dielectric polyacrylonitrile is exposed to microwave radiation leading to an intramolecular cyclization reaction producing π-conjugated segments, which fluoresce blue. During this conversion, the particles shrink in diameter but as an ensemble they retain their monodispersity. This work investigates the optimal reaction conditions and characterizes the optical properties. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The effect of electron-beam irradiation and halogen-free flame retardants on properties of poly butylene terephthalate

NASA Astrophysics Data System (ADS)

Hooshangi, Zhila; Feghhi, Seyed Amir Hossein; Sheikh, Nasrin

2015-03-01

Engineering plastics like Poly (butylene terephthalate) due to their desirable properties have various industrial applications. Neat PBT is highly combustible, so it is necessary to improve significantly its fire retardancy to meet the fire safety requirements. The combustion performance of PBT can be improved by addition of appropriate flame retardant additives. In this study we have investigated the effect of halogen free flame retardants, i.e. melamine and aluminum phosphate, and instantaneously electron beam radiation-induced crosslinking in the presence of Triallyl cyanurate on various properties of PBT. The results of gel content showed that a dose range of 200-400 kGy leads to high cross linked structure in this polymer. Also mechanical experiments showed that its structure became rigid and fragile due to irradiation. Radiation crosslinking of this polymer made its dielectric loss coefficient ten times lower than non-irradiated polymer, but had no effect on its dielectric constant. Moreover the addition of the fire retardant additives as impurity decreased the dielectric loss coefficient. TGA analysis in nitrogen exhibited that irradiation increases char formation and use of the fire retardant additives leads to reduction of onset temperature and formation of higher char quantity than pure PBT. According to the results of UL-94, irradiated samples burned with lower speed and less dripping in vertical and horizontal positions than pure polymer. Finally irradiation of the polymers containing fire retardant additives with a dose of 400 kGy led to self-extinguishing and non-dripping and reach to V-0 level in the UL-94 V.

Summary Report of the Summer Conference DARPA-Materials Research Council Held in La Jolla, California on 10 July thru 4 August 1989

DTIC Science & Technology

1989-08-04

ceramic substrate and a multilayer thin film metal (copper) and polymer ( polyimide ) overlays. 73 The MCM technology was pioneered by IBM, which has made...packaging. The first is the use of polymeric dielectric layers such as polyimides . In fact, the current MCP’s 3 being developed for the DoD use... polyimide dielectrics. Nonetheless, much work remains to be done before these organic dielectrics can be regarded as Isatisfactory. Polyimides have a

Novel Polymeric Dielectric Materials for the Additive Manufacturing of Microwave Devices

NASA Astrophysics Data System (ADS)

O'Keefe, Shamus E.

The past decade has seen a rapid increase in the deployment of additive manufacturing (AM) due to the perceived benefits of lower cost, higher quality, and a smaller environmental footprint. And while the hardware behind most of AM processes is mature, the study and development of material feedstock(s) are in their infancy, particularly so for niche areas. In this dissertation, we look at novel polymeric materials to support AM for microwave devices. Chapter 1 provides an overview of the benefits of AM, followed by the specific motivation for this work, and finally a scope defining the core objectives. Chapter 2 delves into a higher-level background of dielectric theory and includes a brief overview of the two common dielectric spectroscopy techniques used in this work. The remaining chapters, summarized below, describe experiments in which novel polymeric materials were developed and their microwave dielectric properties measured. Chapter 3 describes the successful synthesis of polytetrafluroethylene (PTFE)/polyacrylate (PA) core-shell nanoparticles and their measured microwave dielectric properties. PTFE/PA core-shell nanoparticles with spherical morphology were successfully made by aerosol deposition followed by a brief annealing. The annealing temperature is closely controlled to exceed the glass transition (Tg) of the PA shell yet not exceed the Tg of the PTFE core. Furthermore, the annealing promotes coalescence amongst the PA shells of neighboring nanoparticles and results in the formation of a contiguous PA matrix that has excellent dispersion of PTFE cores. The measured dielectric properties agree well with theoretical predictions and suggest the potential of this material as a feedstock for AM microwave devices. Chapter 4 delves into the exploration of various polyimide systems with the aim of replacing the PA in the previously studied PTFE/PA core-shell nanoparticles. Fundamental relationships between polymer attributes (flexibility/rigidity and functional groups) and dielectric properties were explored. The results indicate that backbone rigidity and the inclusion of fluorine lead to excellent dielectric properties, however, often at the expense of mechanical properties. Chapter 5 explores the optimization of PTFE core-shell nanoparticles via a novel PTFE/polyimide (PI) core-shell nanoparticle. PTFE/PI core-shell nanoparticles were synthesized via electrostatic interaction between the PTFE cores and a PI precursor, poly(amic) acid salt (PAAS). The PAAS is converted to PI by thermal imidization. The PI has properties superior to those of PA for microwave applications and the results suggest the promise of PTFE/PI core-shell nanoparticles for use in AM of microwave devices. Chapter 6 describes the first report of on actively-tunable microwave substrate made possible by a semiconducting polymer composite blend. The composite blend is comprised of poly(3-hexylthiophene) (P3HT) as the semiconducting polymer and [6,6]-Phenyl C61 butyric acid methyl ester (PCBM) while the remainder of the composite is comprised of a low dielectric constant polymer polydimethylsiloxane (PDMS). When subjected to photo excitation (white light, spectrum centered at 532 nm), the composite exhibits a tunability of the permittivity up to 20%. The results suggest strong promise for the use of semiconducting polymers in actively-tunable microwave devices. Finally, Chapter 7 presents a summary of the salient conclusions of the reported studies. The chapter concludes with a few brief remarks of my personal experience as a non-traditional student and the challenges therein.

Characterization of Tantalum Polymer Capacitors

NASA Technical Reports Server (NTRS)

Spence, Penelope

2012-01-01

Overview Reviewed data Caution must be taken when accelerating test conditions Data not useful to establish an acceleration model Introduction of new failure mechanism skewing results Evidence of Anti-Wear-Out De-doping of polymer Decreased capacitance Increased ESR Not dielectric breakdown Needs further investigation Further investigation into tantalum polymer capacitor technology Promising acceleration model for Manufacturer A Possibility for use in high-reliability space applications with suitable voltage derating.

Thermophysical Properties of Polymer Materials with High Thermal Conductivity

NASA Astrophysics Data System (ADS)

Lebedev, S. M.; Gefle, O. S.; Dneprovskii, S. N.; Amitov, E. T.

2015-06-01

Results of studies on the main thermophysical properties of new thermally conductive polymer materials are presented. It is shown that modification of polymer dielectrics by micron-sized fillers allows thermally conductive materials with thermal conductivity not less than 2 W/(m K) to be produced, which makes it possible to use such materials as cooling elements of various electrical engineering and semiconductor equipment and devices.

Dependence of Pentacene Crystal Growth on Dielectric Roughness for Fabrication of Flexible Field-Effect Transistors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, H.; Yang, C; Kim, S

2010-01-01

The dependence of pentacene nanostructures on gate dielectric surfaces were investigated for flexible organic field-effect transistor (OFET) applications. Two bilayer types of polymer/aluminum oxide (Al{sub 2}O{sub 3}) gate dielectrics were fabricated on commercial Al foils laminated onto a polymer back plate. Some Al foils were directly used as gate electrodes, and others were smoothly polished by an electrolytic etching. These Al surfaces were then anodized and coated with poly({alpha}-methyl styrene) (PAMS). For PAMS/Al{sub 2}O{sub 3} dielectrics onto etched Al foils, surface roughness up to 1 nm could be reached, although isolated dimples with a lateral diameter of several micrometers weremore » still present. On PAMS/Al{sub 2}O{sub 3} dielectrics (surface roughness >40 nm) containing mechanical grooves of Al foil, average hole mobility ({mu}FET) of 50 nm thick pentacene-FETs under the low operating voltages (|V| < 6 V) was {approx}0.15 cm{sup 2} V{sup -1} s{sup -1}. In contrast, pentacene-FETs employing the etched Al gates exhibited {mu}FET of 0.39 cm{sup 2} V{sup -1} s{sup -1}, which was comparable to that of reference samples with PAMS/Al{sub 2}O{sub 3} dielectrics onto flat sputtered Al gates. Conducting-probe atomic force microscopy and two-dimensional X-ray diffraction of pentacene films with various thicknesses revealed different out-of-plane and in-plane crystal orderings of pentacene, depending on the surface roughness of the gate dielectrics.« less

Multilayer Coextrusion of Polymer Composites to Develop Organic Capacitors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mondy, L.; Mrozek, R.; Rao, R.

Multilayer coextrusion is applied to produce a tape containing layers of alternating electrical properties to demonstrate the potential for using coextrusion to manufacture capacitors. To obtain the desired properties, we develop two filled polymer systems, one for conductive layers and one for dielectric layers. We describe numerical models used to help determine the material and processing parameters that impact processing and layer stability. These models help quantify the critical ratios of densities and viscosities of the two layers to maintain stable layers, as well as the effect of increasing the flow rate of one of the two materials. The conductingmore » polymer is based on polystyrene filled with a blend of low-melting-point eutectic metal and nickel particulate filler, as described by Mrozek et al. (2010). The appropriate concentrations of fillers are determined by balancing measured conductivity with processability in a twin screw extruder. Based on results of the numerical models and estimates of the viscosity of emulsions and suspensions, a dielectric layer composed of polystyrene filled with barium titanate is formulated. Despite the fact that the density of the dielectric filler is less than the metallic filler of the conductive phase, as well as rheological measurements that later showed that the dielectric formulation is not an ideal match to the viscosity of the conductive material, the two materials can be successfully coextruded if the flow rates of the two materials are not identical. A measurable capacitance of the layered structure is obtained.« less

Multilayer Coextrusion of Polymer Composites to Develop Organic Capacitors

DOE PAGES

Mondy, L.; Mrozek, R.; Rao, R.; ...

2015-05-29

Multilayer coextrusion is applied to produce a tape containing layers of alternating electrical properties to demonstrate the potential for using coextrusion to manufacture capacitors. To obtain the desired properties, we develop two filled polymer systems, one for conductive layers and one for dielectric layers. We describe numerical models used to help determine the material and processing parameters that impact processing and layer stability. These models help quantify the critical ratios of densities and viscosities of the two layers to maintain stable layers, as well as the effect of increasing the flow rate of one of the two materials. The conductingmore » polymer is based on polystyrene filled with a blend of low-melting-point eutectic metal and nickel particulate filler, as described by Mrozek et al. (2010). The appropriate concentrations of fillers are determined by balancing measured conductivity with processability in a twin screw extruder. Based on results of the numerical models and estimates of the viscosity of emulsions and suspensions, a dielectric layer composed of polystyrene filled with barium titanate is formulated. Despite the fact that the density of the dielectric filler is less than the metallic filler of the conductive phase, as well as rheological measurements that later showed that the dielectric formulation is not an ideal match to the viscosity of the conductive material, the two materials can be successfully coextruded if the flow rates of the two materials are not identical. A measurable capacitance of the layered structure is obtained.« less

Enhancing breakdown strength and energy storage performance of PVDF-based nanocomposites by adding exfoliated boron nitride

NASA Astrophysics Data System (ADS)

Xie, Yunchuan; Wang, Jian; Yu, Yangyang; Jiang, Wanrong; Zhang, Zhicheng

2018-05-01

Polymer/ceramic nanocomposites are promising dielectrics for high energy storage density (Ue) capacitors. However, their low breakdown strength (Eb) and high dielectric loss due to heterogeneous structure seriously limit their applications under high electric field. In this work, boron nitride nano-sheets (BNNS) exfoliated from BN particles were introduced into PVDF-based BaTiO3 (mBT) binary composites to reduce the dielectric loss and promote the Ue. The effects of BNNS on the dielectric properties, especially breakdown resistance, and energy storage performance of the resultant composites were carefully investigated by comparing with the composites without BNNS. The introduction of BNNS could significantly improve Eb and Ue of the final composites. Ternary composite with particle contents of 6 wt% BNNS and 5 wt% mBT presented a Eb of about 400 MV/m and Ue of 5.2 J/cm3, which is 40% and 30% superior to that of the binary composite with 5 wt% mBT, respectively. That may be attributed to the 2D structure, high bulk electrical resistivity, and fine dispersion in PVDF of BNNS, which is acting as an efficient insulating barrier against the leakage current and charges conduction. The depression effect of BNNS onto the charge mobility and the interfacial polarization of the polymer composites is finely addressed, which may offer a promising strategy for the fabrication of high-k polymer composites with low loss.

Radiation Shielding Systems Using Nanotechnology

NASA Technical Reports Server (NTRS)

Chen, Bin (Inventor); McKay, Christoper P. (Inventor)

2011-01-01

A system for shielding personnel and/or equipment from radiation particles. In one embodiment, a first substrate is connected to a first array or perpendicularly oriented metal-like fingers, and a second, electrically conducting substrate has an array of carbon nanostructure (CNS) fingers, coated with an electro-active polymer extending toward, but spaced apart from, the first substrate fingers. An electric current and electric charge discharge and dissipation system, connected to the second substrate, receives a current and/or voltage pulse initially generated when the first substrate receives incident radiation. In another embodiment, an array of CNSs is immersed in a first layer of hydrogen-rich polymers and in a second layer of metal-like material. In another embodiment, a one- or two-dimensional assembly of fibers containing CNSs embedded in a metal-like matrix serves as a radiation-protective fabric or body covering.

PVDF-based copolymers, terpolymers and their multi-component material systems for capacitor applications

NASA Astrophysics Data System (ADS)

Chu, Baojin

Miniature of power electronics, scaling-down of microelectronics and other electrical and electronic systems, and development of many technologies (such as hybrid vehicles or implantable heart defibrillators) require capacitors with high energy density to improve the weight and volume efficiency of the whole system. Various capacitor technologies are investigated to meet the requirements of developing future technologies. Among these technologies, polymer film capacitor technology is one of the most promising. Besides high energy density, polymer-based capacitors possess the merits of high power density, low loss, high reliability (self-healing), easy processing, and feasibility (in size, shape and energy level). Due to the ferroelectricity of polyvinylidene fluoride (PVDF)-based polymers, they exhibit much higher polarization response under an electric field, in comparison with other linear dielectric polymers for capacitor applications. The maximum polarization level of PVDF-based polymers can be as high as 0.1 C/m2 and the breakdown field can be higher than 600 MV/m. An estimated energy density of around 30 J/cm3 can be expected in this class of materials. However, this value is much higher than the energy density that can be achieved in the PVDF homopolymer and the poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) copolymers due to the polarization hysteresis in these polymers. Therefore, in this thesis, PVDF-based polymer materials were investigated and developed to approach this expected energy density by various strategies. An energy density of higher than 24 J/cm 3, which is close to the predicted value, was found in PVDF-based copolymers. Recently, the poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)) terpolymer was developed in Prof. Qiming Zhang's group. Previous works have shown that incorporation of CTE into P(VDF-TrFE) copolymers, in which bulky CFE acts as a defect, could convert the copolymer into relaxor ferroelectrics. P(VDF-TrFE-CFE) terpolymers possess a high dielectric constant (larger than 50 at 1 kHz) at room temperature and excellent electromechanical properties. Here, the P(VDF-TrFE-CFE) terpolymers were studied as dielectric materials for capacitor applications. The electrical, thermal and microstructure characterizations were performed on the terpolymers. The terpolymers exhibit a high breakdown field (higher than 400 MV/m) and energy density (larger than 9 J/cm 3). The energy discharge characteristics of the terpolymer were studied by directly discharging the stored energy in the terpolymers to a load resistor. Due to the highly field-dependent nonlinear and frequency dependent dielectric response of the terpolymers, the discharge energy density and equivalent series resistance strongly depend on the load resistor and discharge speed. This study found that for high energy density dielectric materials, a very high dielectric constant might not be an advantage. In the case of terpolymers, this leads to early polarization saturation, i.e., polarization response saturates under an electric field much lower than the breakdown field and causes lower than expected energy density. Due to the dielectric nonlinearity and early saturation of polarization, the energy density of the terpolymers increases linearly with the applied electric fields. It was also found that the polymer-metal interface played an important role for conduction and the breakdown field in the terpolymers, which was related to the charge injection from the metal to the polymer. Due to highly nonlinear dielectric behavior and early polarization saturation in the terpolymers, it was proposed that a high dielectric constant might not be desirable to obtain high energy density. Poly(vinylidene fluoride-chlorotrifluoroethylene) (P(VDFCTFE), 10, 15 and 20 wt% CTFE) and Poly(vinylidene fluoride-hexafluoropropylene) (P(VDF-HFP), 10 and 12 wt% HFP) copolymers, which possess a much lower dielectric constant (about 12 at 1 kHz at room temperature), were further investigated for dielectric materials of high energy density. Due to the lower dielectric constant, the early polarization saturation was avoided and these polymers showed a very high breakdown field and energy density. For the P(VDF-CTFE) copolymer with 15 wt% CTFE, an energy density of higher than 24 J/cm 3 at an electric field higher than 650 MV/m could be obtained. Based on thermal and microstructure studies, the high energy density was found to be caused by the structural modification of PVDF by bulky CTFE or HFP, which also act as defects, similar to the terpolymers. The discharge behavior of the copolymers mainly relies on the load resistors, suggesting that the copolymers have lower equivalent series resistance. Multi-component material system based on current available materials was found to be a useful strategy to tailor and improve the performance of dielectric materials. Nanocomposites composed of the P(VDF-TrFE-CFE) terpolymers and ZrO2 or TiO2 nanoparticles were found to greatly enhance the polarization response and energy density of terpolymers (from 9 J/cm3 to 10.5 J/cm3). Based on comprehensive thermal, dielectric and microstructure studies, the enhancement was believed to be related to the large amount of interfaces in the nanocomposites. In the interfaces, the chain mobility is increased and the energy barrier between the polar and nonpolar phases is reduced, resulting in higher polarization response and energy density at a reduced electric field. The P(VDF-TrFE-CFE) terpolymer/P(VDF-CTFE) copolymer and the P(VDFTrFE-CFE) terpolymer/PMMA blends were also studied. It was found that the P(VDFTrFE-CFE) terpolymers could not be completely miscible with the P(VDF-CTFE) copolymer. In the P(VDF-TrFE-CFE) terpolymer/P(VDF-CTFE) copolymer blends, with a small amount of the copolymer (5 and 10 wt%) in the terpolymer, enhancement of the polarization response similar to that observed in the terpolymer/ZrO 2 nanocomposites was observed. This enhancement was also thought to be mainly caused by the interface effect. The breakdown field of blends was also greatly improved, which resulted in a significant improvement in energy density (from 9 J/cm3 to 11.5 J/cm3). The P(VDF-TrFE-CFE) terpolymers are miscible with PMMA. Addition of PMMA was found to reduce the dielectric response of blends, but also to improve the breakdown field due to the improvement of mechanical properties. The optimum composition of the blends is around 2.5 wt% PMMA. With this composition, the breakdown field of the blends can be improved without reduction of energy density.

High temperature polymers - A review of novel thermally stable hexafluoroisopropylidene-containing polymers

NASA Technical Reports Server (NTRS)

Kane, K. M.; Cassidy, P. E.; Tullos, G. L.; Reynolds, D. W.

1990-01-01

The synthesis and properties to date of several novel HFIP-containing polymers and copolymers are presented. Thermal analyses of polyether ketones (PEK), aromatic polyesters, and polymers from a novel 18F-diacid were performed on a thermal analyzer. All three polymer types exhibited enhanced solubility, thermal stability, and low dielectric constants that are predicted for polymers containing the HFIP moiety. The moderate thermal stability observed in the polymers derived from the 18F-diacid is attributed to the oxidatively weak methylene linkage between the HFIP groups and the phenyl rings. PEKs and polyarylates show potential as high emissivity coatings under conditions where atomic oxygen is present.

A polymer dataset for accelerated property prediction and design.

PubMed

Huan, Tran Doan; Mannodi-Kanakkithodi, Arun; Kim, Chiho; Sharma, Vinit; Pilania, Ghanshyam; Ramprasad, Rampi

2016-03-01

Emerging computation- and data-driven approaches are particularly useful for rationally designing materials with targeted properties. Generally, these approaches rely on identifying structure-property relationships by learning from a dataset of sufficiently large number of relevant materials. The learned information can then be used to predict the properties of materials not already in the dataset, thus accelerating the materials design. Herein, we develop a dataset of 1,073 polymers and related materials and make it available at http://khazana.uconn.edu/. This dataset is uniformly prepared using first-principles calculations with structures obtained either from other sources or by using structure search methods. Because the immediate target of this work is to assist the design of high dielectric constant polymers, it is initially designed to include the optimized structures, atomization energies, band gaps, and dielectric constants. It will be progressively expanded by accumulating new materials and including additional properties calculated for the optimized structures provided.

Effect of mechanical loading on the electrical durability of polymers

NASA Astrophysics Data System (ADS)

Slutsker, A. I.; Veliev, T. M.; Alieva, I. K.; Alekperov, V. A.; Polikarpov, Yu. I.; Karov, D. D.

2017-01-01

A decrease in the electrical durability, which is defined as an amount of time required for dielectric breakdown at a constant electric field strength, of polyethylene and Lavsan (polyethylene terephthalate) films under tensile loading is registered in a temperature range from 100 to 300 K. It is established that the pulling apart of the axes of neighbor chain molecules in consequence of tensile loading gives rise to a decrease in the energy level of the intermolecular electron traps. In the amorphous region of a polymer, this accelerates the release of electrons from the traps through over-barrier transitions at higher temperatures ranging from about 230 to 350 K and quantum tunneling transitions at lower temperatures in the range from about 80 to 200 K. As a result, the time required for the formation of a critical space charge, i.e., the waiting period of dielectric breakdown, decreases, which means a reduction in the electrical durability of polymers.

Dielectric spectroscopy of polymer-metal composites across the percolation threshold

NASA Astrophysics Data System (ADS)

Panda, Maheswar; Srinivas, V.; Thakur, A. K.

2014-11-01

Polymer (polar/nonpolar)/metal composites (PMC) were prepared under different process conditions. In polar PMC, dipolar relaxation plays a predominant role below percolation threshold (fc) and anomalous low frequency dispersion (ALFD) becomes dominant above fc while ALFD is the only likely possibility for nonpolar PMC above fc. The magnitude of relaxation exponents "m", "p" and "n", evaluated from the experimental results using Jonscher's universal dielectric response (JUDR) laws, falls within the universal limit [0, 1] with additional feature of strong dependence on volume fraction of conductor (fcon). The decrease in the relaxation exponent "m" with an increase of fcon is directly linked with decrease in the number of dipoles of the polymer in the composite and is accompanied by a distribution of relaxation time due to increased heterogeneity of the system. The magnitude of the relaxation exponent "n" decreases at fc, due to the prevalence of Maxwell-Wagner-Sillar polarization contributed by uncorrelated electrons.

Role of the Strength of Drug-Polymer Interactions on the Molecular Mobility and Crystallization Inhibition in Ketoconazole Solid Dispersions.

PubMed

Mistry, Pinal; Mohapatra, Sarat; Gopinath, Tata; Vogt, Frederick G; Suryanarayanan, Raj

2015-09-08

The effects of specific drug-polymer interactions (ionic or hydrogen-bonding) on the molecular mobility of model amorphous solid dispersions (ASDs) were investigated. ASDs of ketoconazole (KTZ), a weakly basic drug, with each of poly(acrylic acid) (PAA), poly(2-hydroxyethyl methacrylate) (PHEMA), and polyvinylpyrrolidone (PVP) were prepared. Drug-polymer interactions in the ASDs were evaluated by infrared and solid-state NMR, the molecular mobility quantified by dielectric spectroscopy, and crystallization onset monitored by differential scanning calorimetry (DSC) and variable temperature X-ray diffractometry (VTXRD). KTZ likely exhibited ionic interactions with PAA, hydrogen-bonding with PHEMA, and weaker dipole-dipole interactions with PVP. On the basis of dielectric spectroscopy, the α-relaxation times of the ASDs followed the order: PAA > PHEMA > PVP. In addition, the presence of ionic interactions also translated to a dramatic and disproportionate decrease in mobility as a function of polymer concentration. On the basis of both DSC and VTXRD, an increase in strength of interaction translated to higher crystallization onset temperature and a decrease in extent of crystallization. Stronger drug-polymer interactions, by reducing the molecular mobility, can potentially delay the crystallization onset temperature as well as crystallization extent.

Ion solvation in polymer blends and block copolymer melts: effects of chain length and connectivity on the reorganization of dipoles.

PubMed

Nakamura, Issei

2014-05-29

We studied the thermodynamic properties of ion solvation in polymer blends and block copolymer melts and developed a dipolar self-consistent field theory for polymer mixtures. Our theory accounts for the chain connectivity of polymerized monomers, the compressibility of the liquid mixtures under electrostriction, the permanent and induced dipole moments of monomers, and the resultant dielectric contrast among species. In our coarse-grained model, dipoles are attached to the monomers and allowed to rotate freely in response to electrostatic fields. We demonstrate that a strong electrostatic field near an ion reorganizes dipolar monomers, resulting in nonmonotonic changes in the volume fraction profile and the dielectric function of the polymers with respect to those of simple liquid mixtures. For the parameter sets used, the spatial variations near an ion can be in the range of 1 nm or larger, producing significant differences in the solvation energy among simple liquid mixtures, polymer blends, and block copolymers. The solvation energy of an ion depends substantially on the chain length in block copolymers; thus, our theory predicts the preferential solvation of ions arising from differences in chain length.

Polyethylene oxide-polytetrahydrofurane-PEDOT conducting interpenetrating polymer networks for high speed actuators

NASA Astrophysics Data System (ADS)

Plesse, C.; Khaldi, A.; Wang, Q.; Cattan, E.; Teyssié, D.; Chevrot, C.; Vidal, F.

2011-12-01

In recent years, numerous studies on electro-active polymer (EAP) actuators have been reported. One promising technology is the elaboration of electronic conducting polymer-based actuators with interpenetrating polymer network (IPNs) architecture. In this study, the synthesis and characterisation of conducting IPNs for actuator applications is described. The IPNs are synthesised from polyethylene oxide (PEO) and polytetrahydrofurane (PTHF) networks in which the conducting polymer (poly(3,4-ethylenedioxythiophene)) is incorporated. In a first step, PEO/PTHF IPNs were prepared via an 'in situ' process using poly(ethylene glycol) methacrylate and dimethacrylate and hydroxytelechelic PTHF as starting materials. The IPN mechanical properties were examined by DMA and tensile strength tests. N-ethylmethylimidazolium bis(trifluoromethanesulfonyl)imide (EMITFSI) swollen PEO/PTHF IPNs show ionic conductivities up to 10-3 S cm-1 at 30 °C. In a second step, the conducting IPN actuators were prepared by oxidative polymerisation of 3,4-ethylenedioxithiophene (EDOT) using FeCl3 as an oxidising agent within the PEO/PTHF IPN host matrix. The frequency response performance of the bending conducting IPN actuator was then evaluated. The resulting actuator exhibits a mechanical resonance frequency of up to 125 Hz with 0.75% strain for an applied potential of ± 5 V.

Control of a chemical reaction (photodegradation of the p3ht polymer) with nonlocal dielectric environments

PubMed Central

Peters, V. N.; Tumkur, T. U.; Zhu, G.; Noginov, M. A.

2015-01-01

Proximity to metallic surfaces, plasmonic structures, cavities and other inhomogeneous dielectric environments is known to control spontaneous emission, energy transfer, scattering, and many other phenomena of practical importance. The aim of the present study was to demonstrate that, in spirit of the Marcus theory, the rates of chemical reactions can, too, be influenced by nonlocal dielectric environments, such as metallic films and metal/dielectric bilayer or multilayer structures. We have experimentally shown that metallic, composite metal/dielectric substrates can, indeed, control ordering as well as photodegradation of thin poly-3-hexylthiophene (p3ht) films. In many particular experiments, p3ht films were separated from metal by a dielectric spacer, excluding conventional catalysis facilitated by metals and making modification of the nonlocal dielectric environment a plausible explanation for the observed phenomena. This first step toward understanding of a complex relationship between chemical reactions and nonlocal dielectric environments is to be followed by the theory development and a broader scope of thorough experimental studies. PMID:26434679

Surface and Electrochemical Properties of Polymer Brush-Based Redox Poly(Ionic Liquid).

PubMed

Bui-Thi-Tuyet, Van; Trippé-Allard, Gaëlle; Ghilane, Jalal; Randriamahazaka, Hyacinthe

2016-10-26

Redox-active poly(ionic liquid) poly(3-(2-methacryloyloxy ethyl)-1-(N-(ferrocenylmethyl) imidazolium bis(trifluoromethylsulfonyl)imide deposited onto electrode surfaces has been prepared using surface-initiated atom transfer radical polymerization SI-ATRP. The process starts by electrochemical immobilization of initiator layer, and then methacrylate monomer carrying ferrocene and imidazolium units is polymerized in ionic liquid media via SI-ATRP process. The surfaces analyses of the polymer exhibit a well-defined polymer brushlike structure and confirm the presence of ferrocene and ionic moieties within the film. Furthermore, the electrochemical investigations of poly(redox-active ionic liquid) in different media demonstrate that the electron transfer is not restricted by the rate of counterion migration into/out of the polymer. The attractive electrochemical performance of these materials is further demonstrated by performing electrochemical measurement, of poly(ferrocene ionic liquid), in solvent-free electrolyte. The facile synthesis of such highly ordered electroactive materials based ionic liquid could be useful for the fabrication of nanostructured electrode suitable for performing electrochemistry in solvent free electrolyte. We also demonstrate possible applications of the poly(FcIL) as electrochemically reversible surface wettability system and as electrochemical sensor for the catalytic activity toward the oxidation of tyrosine.

A new composite consisting of electrosynthesized conducting polymers, graphene sheets and biosynthesized gold nanoparticles for biosensing acute lymphoblastic leukemia.

PubMed

Mazloum-Ardakani, Mohammad; Barazesh, Behnaz; Khoshroo, Alireza; Moshtaghiun, Mohammad; Sheikhha, Mohammad Hasan

2018-06-01

In this work we report the synthesis of a stable composite with excellent electrical properties, on the surface of a biosensor. Conductive polymers offer both high electrical conductivity and mechanical strength. Many reports have focused on synthesizing conductive polymers with the aid of high-cost enzymes. In the current work we introduce a novel electrochemical, one-step, facile and cost effective procedure for synthesizing poly (catechol), without using expensive enzymes. The poly (catechol) conductivity was enhanced by modification with graphene sheets and biosynthesized gold nanoparticles. Four different robust methods, DPV, EIS, CV and chronoamperometry, were used to monitor the biosensor modifications. The peak currents of the catechol (an electroactive probe) were linearly related to the logarithm of the concentrations of target DNA in the range 100.0 μM to 10.0 pM, with a detection limit of 1.0 pM for the DNA strand. The current work investigates a new, stable composite consisting of conductive polymers and nanoparticles, which was applied to the detection of acute lymphoblastic leukemia. Copyright © 2018 Elsevier B.V. All rights reserved.

Effect of the aggregate morphology on the dispersability of MWCNTs in polymer melts

NASA Astrophysics Data System (ADS)

de Luna, M. Salzano; Tito, A.; Citterio, A.; Mazzocchia, C.; Acierno, D.; Filippone, G.

2012-07-01

Polystyrene nanocomposites filled with multi-walled carbon nanotubes have been prepared through a masterbatch melt mixing method and subjected to morphological, rheological and dielectrical analyses. The role of the structure of the initial aggregates has been investigated by comparing commercially available and synthesized MWCNTs prepared through fluidized bed chemical vapor deposition method and purified through a scalable one-pot route. Electron microscopy analyses reveal a less compact structure of the synthesized particles, in which the nanotubes are arranged in less entangled bundles. This reduces the strength of the initial agglomerates, thus enhancing their dispersability inside the host polymer by means of melt compounding as confirmed by both rheological and dielectrical measurements.

Benzocyclobutene (BCB) Polymer as Amphibious Buffer Layer for Graphene Field-Effect Transistor.

PubMed

Wu, Yun; Zou, Jianjun; Huo, Shuai; Lu, Haiyan; Kong, Yuecan; Chen, Tangshen; Wu, Wei; Xu, Jingxia

2015-08-01

Owing to the scattering and trapping effects, the interfaces of dielectric/graphene or substrate/graphene can tailor the performance of field-effect transistor (FET). In this letter, the polymer of benzocyclobutene (BCB) was used as an amphibious buffer layer and located at between the layers of substrate and graphene and between the layers of dielectric and graphene. Interestingly, with the help of nonpolar and hydrophobic BCB buffer layer, the large-scale top-gated, chemical vapor deposited (CVD) graphene transistors was prepared on Si/SiO2 substrate, its cutoff frequency (fT) and the maximum cutoff frequency (fmax) of the graphene field-effect transistor (GFET) can be reached at 12 GHz and 11 GHz, respectively.

Incorporation of glass-reinforced hydroxyapatite microparticles into poly(lactic acid) electrospun fibre mats for biomedical applications.

PubMed

Santos, Daniel; Correia, Cristina O; Silva, Dina M; Gomes, Pedro S; Fernandes, Maria H; Santos, José D; Sencadas, Vitor

2017-06-01

Tissue engineering is constantly evolving towards novel materials that mimic the properties of the replaced injured tissue or organ. A hybrid electrospun membrane of electroactive poly(l-acid lactic) (PLLA) polymer with glass reinforced hydroxyapatite (Bonelike®) microparticles placed among the polymer fibres in a morphology like "islands in the sea" was processed. The incorporation of 60 to 80wt% Bonelike® bone grafts granules with ≤150μm into the polymer solution lead to an amorphous polymeric fibre membranes, and a decrease of the average polymer fibre diameter from 550±150nm for neat PLA down to 440±170nm for the hybrid composite. The presence of Bonelike® in the polymer mats reduced the activation energy for thermal degradation from 134kJ·mol -1 , obtained for the neat PLLA membranes down to 71kJ·mol -1 , calculated for the hybrid composite membranes. In vitro cell culture results suggest that the developed processing method does not induce cytotoxic effects in MG 63 osteoblastic cells, and creates an environment that enhances cell proliferation, when compared to the neat PLLA membrane. The simplicity and scalability of the processing method suggests a large application potential of this novel hybrid polymer-microparticles fibre membranes for bone regenerative medicine. Copyright © 2017 Elsevier B.V. All rights reserved.

Pulse Power Capability Of High Energy Density Capacitors Based on a New Dielectric Material

NASA Technical Reports Server (NTRS)

Winsor, Paul; Scholz, Tim; Hudis, Martin; Slenes, Kirk M.

1999-01-01

A new dielectric composite consisting of a polymer coated onto a high-density metallized Kraft has been developed for application in high energy density pulse power capacitors. The polymer coating is custom formulated for high dielectric constant and strength with minimum dielectric losses. The composite can be wound and processed using conventional wound film capacitor manufacturing equipment. This new system has the potential to achieve 2 to 3 J/cu cm whole capacitor energy density at voltage levels above 3.0 kV, and can maintain its mechanical properties to temperatures above 150 C. The technical and manufacturing development of the composite material and fabrication into capacitors are summarized in this paper. Energy discharge testing, including capacitance and charge-discharge efficiency at normal and elevated temperatures, as well as DC life testing were performed on capacitors manufactured using this material. TPL (Albuquerque, NM) has developed the material and Aerovox (New Bedford, MA) has used the material to build and test actual capacitors. The results of the testing will focus on pulse power applications specifically those found in electro-magnetic armor and guns, high power microwave sources and defibrillators.

Quantitative property-structural relation modeling on polymeric dielectric materials

NASA Astrophysics Data System (ADS)

Wu, Ke

Nowadays, polymeric materials have attracted more and more attention in dielectric applications. But searching for a material with desired properties is still largely based on trial and error. To facilitate the development of new polymeric materials, heuristic models built using the Quantitative Structure Property Relationships (QSPR) techniques can provide reliable "working solutions". In this thesis, the application of QSPR on polymeric materials is studied from two angles: descriptors and algorithms. A novel set of descriptors, called infinite chain descriptors (ICD), are developed to encode the chemical features of pure polymers. ICD is designed to eliminate the uncertainty of polymer conformations and inconsistency of molecular representation of polymers. Models for the dielectric constant, band gap, dielectric loss tangent and glass transition temperatures of organic polymers are built with high prediction accuracy. Two new algorithms, the physics-enlightened learning method (PELM) and multi-mechanism detection, are designed to deal with two typical challenges in material QSPR. PELM is a meta-algorithm that utilizes the classic physical theory as guidance to construct the candidate learning function. It shows better out-of-domain prediction accuracy compared to the classic machine learning algorithm (support vector machine). Multi-mechanism detection is built based on a cluster-weighted mixing model similar to a Gaussian mixture model. The idea is to separate the data into subsets where each subset can be modeled by a much simpler model. The case study on glass transition temperature shows that this method can provide better overall prediction accuracy even though less data is available for each subset model. In addition, the techniques developed in this work are also applied to polymer nanocomposites (PNC). PNC are new materials with outstanding dielectric properties. As a key factor in determining the dispersion state of nanoparticles in the polymer matrix, the surface tension components of polymers are modeled using ICD. Compared to the 3D surface descriptors used in a previous study, the model with ICD has a much improved prediction accuracy and stability particularly for the polar component. In predicting the enhancement effect of grafting functional groups on the breakdown strength of PNC, a simple local charge transfer model is proposed where the electron affinity (EA) and ionization energy (IE) determines the main charge trap depth in the system. This physical model is supported by first principle computation. QSPR models for EA and IE are also built, decreasing the computation time of EA and IE for a single molecule from several hours to less than one second. Furthermore, the designs of two web-based tools are introduced. The tools represent two commonly used applications for QSPR studies: data inquiry and prediction. Making models and data public available and easy to use is particularly crucial for QSPR research. The web tools described in this work should provide a good guidance and starting point for the further development of information tools enabling more efficient cooperation between computational and experimental communities.

Electrochemical characterization and control of triple-layer muscles

NASA Astrophysics Data System (ADS)

Otero, Toribio F.; Cortes, Maria T.

2000-06-01

The electrochemical characterization of triple-layers formed by a EPA (Electroactive Polymer)/double-sided tape/EPA, like artificial muscles is described. Those muscles were characterized working under constant potential or under constant current. Due to the electrochemical nature of the electrochemomechanical property, muscles working under constant current produce constant movements, consuming increasing energies at decreasing temperatures, decreasing concentrations of electrolytes or trailing increasing masses. Muscles working at constant potential response with a faster movement if the temperature or the concentration of the electrolyte increase, or if the trailed weight decreases. Specific charges and specific energies were determined for every experimental condition.

Artificial Muscle Kits for the Classroom

NASA Technical Reports Server (NTRS)

2004-01-01

Commonly referred to as "artificial muscles," electroactive polymer (EAP) materials are lightweight strips of highly flexible plastic that bend or stretch when subjected to electric voltage. EAP materials may prove to be a substitution for conventional actuation components such as motors and gears. Since the materials behave similarly to biological muscles, this emerging technology has the potential to develop improved prosthetics and biologically-inspired robots, and may even one day replace damaged human muscles. The practical application of artificial muscles provides a challenge, however, since the material requires improved effectiveness and durability before it can fulfill its potential.

Biologically inspired technologies using artificial muscles

NASA Technical Reports Server (NTRS)

Bar-Cohen, Yoseph

2005-01-01

One of the newest fields of biomimetics is the electroactive polymers (EAP) that are also known as artificial muscles. To take advantage of these materials, efforts are made worldwide to establish a strong infrastructure addressing the need for comprehensive analytical modeling of their response mechanism and develop effective processing and characterization techniques. The field is still in its emerging state and robust materials are still not readily available however in recent years significant progress has been made and commercial products have already started to appear. This paper covers the current state of- the-art and challenges to making artificial muscles and their potential biomimetic applications.

High Temperature DC Bus Capacitor Cost Reduction & Performance Improvements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yializis, Angelo; Taylor, Ralph S.

The goal of this DOE program is to develop high temperature, high energy density, lower cost DC- Link capacitors, for inverters used in electric drive vehicles. Most electric motors in Hybrid Electric Vehicles (“HEVs”), Plug-in Hybrid Vehicles (“PHVs”) and Electric Vehicles (“EVs”) are driven with variable AC voltage supplied by an inverter/converter power module that converts the DC battery voltage to three-phase AC voltage. A key component of the inverter circuit is the DC- Link capacitor used to minimize ripple current, voltage fluctuation, and transient suppression. The DC-Link capacitor is one of the largest, costliest, and most failure-prone components inmore » today’s electric drive invertersystems. The principal weakness of present day DC- Link capacitors is their reliance on a low temperature thermoplastic polypropylene (“PP”) film dielectric. PP is the dielectric of choice for inverter capacitor applications due to its high breakdown strength and low dissipation factor. Major limitations of metallized PP film capacitors include volumetric efficiency, performance under high thermal loads and cost. The latter is especially effectual at lower voltage applications (400V) where PP films with a thickness of about 2.5 m are required that are costly to process. Metallized PP capacitors also do not meet the traditional “under-the-hood” requirements for automotive electronics. The standard temperature requirement for most passive components in the automotive industry has been 125ºC and it is evolving to 140°C. The industry has addressed this problem by reducing the ambient temperature specification for PP capacitors from 125ºC to 105ºC, and also by placing the capacitors on a water-cooled bus bar to extend their life and reliably. The supply chain for the production of PP capacitors is, for the most part, horizontally integrated. It includes the producer of the PP film, the toll metallizer, that deposits a patterned aluminum conductor onto the PP film, and the capacitor producer that winds the metallized film, forms electrical connections, and packages the capacitor (some large capacitor OEMs also metallize their films). The horizontal nature of the supply chain is principally due to the very high capital costs required to integrate the film production process as well as the corresponding depreciation costs. The result is that hundreds of capacitor OEMs use the same base films and capacitor products vary mainly in the way they are wound, formed and packaged, with little or no ability to innovate. Sigma Technologies (“Sigma”) has developed a disruptive process for producing polymer dielectric capacitors that overcome the limitations of PP film capacitors. Metallized self-supported films are replaced with deposited polymer dielectrics, metallized in-line with the polymer deposition process. Highly cross linked, high temperature polymers are formed, that have a thickness as low as 0.1μm, a wide range of dielectric constants and breakdown strength higher than that of PP. The supply chain for producing such capacitors is reduced to a single step performed by the capacitor OEM, in which aluminum wire and a liquid monomer are introduced into a machine to create a large area bulk capacitor material. Polymer Multi-Layer (PML) capacitors are produced by depositing 1000s of dielectric and aluminum electrode on a rotating process drum, forming a nanolaminate “mother capacitor” material, that is segmented and processed into individual capacitor elements. The PML process combines the conventional stepsof a) polymer dielectric formation, b) electrode deposition, and c) winding the capacitor, into a single continuous process performed in a single machine. This allows for complete vertical integration of the capacitor production process, where the capacitor OEM has complete control the dielectric chemistry, the polymer thickness and the electrode metallization process. Sigma partnered with Delphi Automotive Systems (“Delphi”) and Oak Ridge National Labs (“ORNL”) to respond to a DOE Vehicle Technologies Office solicitation to develop a DC-Link capacitor with reduced cost, lower volume and superior thermal properties. The major objectives of the development program included: • Optimization of the polymer dielectric to meet an 140ºC operating environment • Improvements to Sigma’s PML capacitor pilot line to allow the production of sample quantities of DC-Link capacitors • Evaluation of the thermal properties of the PML capacitors • Development of a thermal model to predict capacitor performance under various operating conditions • Electrical and environmental evaluation of PML capacitors based on AEC Q200 standard • Development of a package for PML capacitors • Development of a business plan to transition the PML capacitor technology into production.« less

Nano-Engineering of Active Metamaterials

DTIC Science & Technology

2014-10-29

simulation of linear and nonlinear optical properties and dielectric permittivity including those of dipolar liquids, dendrimers , polymers, and...orders of magnitude with simple variation of chromophore structure. Note that chromophores in dendrimers are usually more stable than the same...chromophore in polymer composites consistent with reduced oxygen accessability in the dendrimer material lattice. Lattice hardening (crosslinking) and

Power and Thermal Technologies for Air and Space -- Scientific Research Program. Delivery Order 0016: Developing and Processing High Energy Density Polymer Film Dielectrics for High Temperature Air Force Power Electronic Applications

DTIC Science & Technology

2010-01-01

a vacuum controller. A vacuum of < 1 µ torr was achieved with a combination of a turbo pump and a scroll pump system. The sample probing is...the polymer was reprecipitated in heptane non-solvent. The filtered polymer was washed with heptane and was finally dried in vacuum at 100ºC for three...solution was added to a large excess of methanol to precipitate the polymer. After soxhlet extraction with methanol and vacuum drying, the polymer was

Metamaterial Behavior of Polymer Nanocomposites Based on Polypropylene/Multi-Walled Carbon Nanotubes Fabricated by Means of Ultrasound-Assisted Extrusion

PubMed Central

Pérez-Medina, Juan C.; Waldo-Mendoza, Miguel A.; Cruz-Delgado, Víctor J.; Quiñones-Jurado, Zoe V.; González-Morones, Pablo; Ziolo, Ronald F.; Martínez-Colunga, Juan G.; Soriano-Corral, Florentino; Avila-Orta, Carlos A.

2016-01-01

Metamaterial behavior of polymer nanocomposites (NCs) based on isotactic polypropylene (iPP) and multi-walled carbon nanotubes (MWCNTs) was investigated based on the observation of a negative dielectric constant (ε′). It is demonstrated that as the dielectric constant switches from negative to positive, the plasma frequency (ωp) depends strongly on the ultrasound-assisted fabrication method, as well as on the melt flow index of the iPP. NCs were fabricated using ultrasound-assisted extrusion methods with 10 wt % loadings of MWCNTs in iPPs with different melt flow indices (MFI). AC electrical conductivity (σ(AC)) as a function of frequency was determined to complement the electrical classification of the NCs, which were previously designated as insulating (I), static-dissipative (SD), and conductive (C) materials. It was found that the SD and C materials can also be classified as metamaterials (M). This type of behavior emerges from the negative dielectric constant observed at low frequencies although, at certain frequencies, the dielectric constant becomes positive. Our method of fabrication allows for the preparation of metamaterials with tunable ωp. iPP pure samples show only positive dielectric constants. Electrical conductivity increases in all cases with the addition of MWCNTs with the largest increases observed for samples with the highest MFI. A relationship between MFI and the fabrication method, with respect to electrical properties, is reported. PMID:28774042

Preliminary investigation of polystyrene/MoS{sub 2}-Oleylamine polymer composite for potential application as low-dielectric material in microelectronics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Landi, Giovanni, E-mail: glandi@unisa.it; Department of Industrial Engineering, University of Salerno, Via G. Paolo II 132, 84084 Fisciano; Altavilla, Claudia

2015-12-17

Insulating materials play a vital role in the design and performance of electrical systems for both steady and transient state conditions. Among the other properties, also in this field, polymer nanocomposites promise to offer exciting improvements. Many studies in the last decade has witnessed significant developments in the area of nano-dielectric materials and significant effects of nano-scale fillers on electric, thermal and mechanical properties of polymeric materials have been observed. However, the developments of new and advanced materials to be used the miniaturization of electronic devices fabrication require extensive studies on electrical insulation characteristics of these materials before they canmore » be used in commercial systems. In this work, Polystyrene (PS) composites were prepared by the blend solution method using MoS{sub 2}@Oleylamine nanosheets as filler. The dielectric properties of the resulting comoposite have been investigated at 300K and in the frequency range between 1000 Hz and 1 MHz. The addition of the MoS{sub 2}@Oleylamine nanosheets leads to a decreasing of the relative dielectric constant and of the electrical conductivity measured in the voltage range between ±500V. Thanks to a possibility to tune the electrical permittivity with the control of MoS{sub 2} concentration, these materials could be used as a low-dielectric material in the microelectronics applications.« less

Electrical and dielectric properties of foam injection-molded polypropylene/multiwalled carbon nanotube composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ameli, A.; Nofar, M.; Saniei, M.

A combination of high dielectric permittivity (ε′) and low dielectric loss (tan δ) is required for charge storage applications. In percolative systems such as conductive polymer composites, however, obtaining high ε′ and low tan δ is very challenging due to the sharp insulation-conduction transition near the threshold region. Due to the particular arrangement of conductive fillers induced by both foaming and injection molding processes, they may address this issue. Therefore, this work evaluates the application of foam injection molding process in fabricating polymer nanocomposites for energy storage. Polypropylene-multiwalled carbon nanotubes (PP-MWCNT) composites were prepared by melt mixing and foamed inmore » an injection molding process. Electrical conductivity (σ), ε′ and tan δ were then characterized. Also, scanning and transmission electron microscopy (SEM and TEM) was used to investigate the carbon nanotube’s arrangement as well as cellular morphology. The results showed that foam injection-molded composites exhibited highly superior dielectric properties to those of solid counterparts. For instance, foamed samples had ε′=68.3 and tan δ =0.05 (at 1.25 vol.% MWCNT), as opposed to ε′=17.8 and tan δ=0.04 in solid samples (at 2.56 vol.% MWCNT). The results of this work reveal that high performance dielectric nanocomposites can be developed using foam injection molding technologies for charge storage applications.« less

Mechanism and influencing factors on critical pulse width of oil-immersed polymer insulators under short pulses

NASA Astrophysics Data System (ADS)

Zhao, Liang; Su, Jian Cang; Li, Rui; Zeng, Bo; Cheng, Jie; Zheng, Lei; Yu, Bin Xiong; Wu, Xiao Long; Zhang, Xi Bo; Pan, Ya Feng

2015-04-01

The critical pulse width (τc) is a pulse width at which the surface flashover threshold (Ef) is equal to the bulk breakdown threshold (EBD) for liquid-polymer composite insulation systems, which is discovered by Zhao et al. [Annual Report Conference on Electrical Insulation and Dielectric Phenomena (IEEE Dielectrics and Electrical Insulation Society, Shenzhen, China, 2013), Vol. 2, pp. 854-857]. In this paper, the mechanism of τc is interpreted in perspective of the threshold and the time delay (td) of surface flashover and bulk breakdown, respectively. It is found that two changes appear as the pulse width decreases which are responsible for the existence of τc: (1) EBD is lower than Ef; (2) td of bulk breakdown is shorter than td of surface flashover. In addition, factors which have influences on τc are investigated, such as the dielectric type, the insulation length, the dielectric thickness, the dielectrics configuration, the pulse number, and the liquid purity. These influences of factors are generalized as three types if τc is expected to increase: (1) factors causing EBD to decrease, such as increasing the pulse number or employing a dielectric of lower EBD; (2) factors causing Ef to increase, such as complicating the insulator's configuration or increasing the liquid purity; (3) factors causing EBD and Ef to increase together, but Ef increases faster than EBD, such as decreasing the dielectric thickness or the insulation length. With the data in references, all the three cases are verified experimentally. In the end, a general method based on τc for solid insulation design is presented and the significance of τc on solid insulation design and on solid demolition are discussed.