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Sample records for piezoelectric field enhanced

  1. Piezoelectrically Enhanced Photocathodes

    NASA Technical Reports Server (NTRS)

    Beach, Robert A.; Nikzad, Shouleh; Bell, Lloyd Douglas; Strittmatter, Robert

    2011-01-01

    Doping of photocathodes with materials that have large piezoelectric coefficients has been proposed as an alternative means of increasing the desired photoemission of electrons. Treating cathode materials to increase emission of electrons is called "activation" in the art. It has been common practice to activate photocathodes by depositing thin layers of suitable metals (usually, cesium). Because cesium is unstable in air, fabrication of cesiated photocathodes and devices that contain them must be performed in sealed tubes under vacuum. It is difficult and costly to perform fabrication processes in enclosed, evacuated spaces. The proposed piezoelectrically enhanced photocathodes would have electron-emission properties similar to those of cesiated photocathodes but would be stable in air, and therefore could be fabricated more easily and at lower cost. Candidate photocathodes include nitrides of elements in column III of the periodic table . especially compounds of the general formula Al(x)Ga(1.x)N (where 0< or = x < or =.1). These compounds have high piezoelectric coefficients and are suitable for obtaining response to ultraviolet light. Fabrication of a photocathode according to the proposal would include inducement of strain in cathode layers during growth of the layers on a substrate. The strain would be induced by exploiting structural mismatches among the various constituent materials of the cathode. Because of the piezoelectric effect in this material, the strain would give rise to strong electric fields that, in turn, would give rise to a high concentration of charge near the surface. Examples of devices in which piezoelectrically enhanced photocathodes could be used include microchannel plates, electron- bombarded charge-coupled devices, image tubes, and night-vision goggles. Piezoelectrically enhanced photocathode materials could also be used in making highly efficient monolithic photodetectors. Highly efficient and stable piezoelectrically enhanced

  2. Piezoelectrically enhanced photocathode

    NASA Technical Reports Server (NTRS)

    Beach, Robert A. (Inventor); Nikzad, Shouleh (Inventor); Strittmatter, Robert P. (Inventor); Bell, Lloyd Douglas (Inventor)

    2009-01-01

    A photocathode, for generating electrons in response to incident photons in a photodetector, includes a base layer having a first lattice structure and an active layer having a second lattice structure and epitaxially formed on the base layer, the first and second lattice structures being sufficiently different to create a strain in the active layer with a corresponding piezoelectrically induced polarization field in the active layer, the active layer having a band gap energy corresponding to a desired photon energy.

  3. Radial Field Piezoelectric Diaphragms

    NASA Technical Reports Server (NTRS)

    Bryant, R. G.; Effinger, R. T., IV; Copeland, B. M., Jr.

    2002-01-01

    A series of active piezoelectric diaphragms were fabricated and patterned with several geometrically defined Inter-Circulating Electrodes "ICE" and Interdigitated Ring Electrodes "ICE". When a voltage potential is applied to the electrodes, the result is a radially distributed electric field that mechanically strains the piezoceramic along the Z-axis (perpendicular to the applied electric field). Unlike other piezoelectric bender actuators, these Radial Field Diaphragms (RFDs) strain concentrically yet afford high displacements (several times that of the equivalent Unimorph) while maintaining a constant circumference. One of the more intriguing aspects is that the radial strain field reverses itself along the radius of the RFD while the tangential strain remains relatively constant. The result is a Z-deflection that has a conical profile. This paper covers the fabrication and characterization of the 5 cm. (2 in.) diaphragms as a function of poling field strength, ceramic thickness, electrode type and line spacing, as well as the surface topography, the resulting strain field and displacement as a function of applied voltage at low frequencies. The unique features of these RFDs include the ability to be clamped about their perimeter with little or no change in displacement, the environmentally insulated packaging, and a highly repeatable fabrication process that uses commodity materials.

  4. Piezoelectric enhancement under negative pressure

    PubMed Central

    Kvasov, Alexander; McGilly, Leo J.; Wang, Jin; Shi, Zhiyong; Sandu, Cosmin S.; Sluka, Tomas; Tagantsev, Alexander K.; Setter, Nava

    2016-01-01

    Enhancement of ferroelectric properties, both spontaneous polarization and Curie temperature under negative pressure had been predicted in the past from first principles and recently confirmed experimentally. In contrast, piezoelectric properties are expected to increase by positive pressure, through polarization rotation. Here we investigate the piezoelectric response of the classical PbTiO3, Pb(Zr,Ti)O3 and BaTiO3 perovskite ferroelectrics under negative pressure from first principles and find significant enhancement. Piezoelectric response is then tested experimentally on free-standing PbTiO3 and Pb(Zr,Ti)O3 nanowires under self-sustained negative pressure, confirming the theoretical prediction. Numerical simulations verify that negative pressure in nanowires is the origin of the enhanced electromechanical properties. The results may be useful in the development of highly performing piezoelectrics, including lead-free ones. PMID:27396411

  5. Piezoelectric enhancement under negative pressure

    NASA Astrophysics Data System (ADS)

    Kvasov, Alexander; McGilly, Leo J.; Wang, Jin; Shi, Zhiyong; Sandu, Cosmin S.; Sluka, Tomas; Tagantsev, Alexander K.; Setter, Nava

    2016-07-01

    Enhancement of ferroelectric properties, both spontaneous polarization and Curie temperature under negative pressure had been predicted in the past from first principles and recently confirmed experimentally. In contrast, piezoelectric properties are expected to increase by positive pressure, through polarization rotation. Here we investigate the piezoelectric response of the classical PbTiO3, Pb(Zr,Ti)O3 and BaTiO3 perovskite ferroelectrics under negative pressure from first principles and find significant enhancement. Piezoelectric response is then tested experimentally on free-standing PbTiO3 and Pb(Zr,Ti)O3 nanowires under self-sustained negative pressure, confirming the theoretical prediction. Numerical simulations verify that negative pressure in nanowires is the origin of the enhanced electromechanical properties. The results may be useful in the development of highly performing piezoelectrics, including lead-free ones.

  6. Piezoelectric Field Enhanced Second-Order Nonlinear Optical Susceptibilities in Wurtzite GaN/AlGaN Quantum Wells

    NASA Technical Reports Server (NTRS)

    Liu, Ansheng; Chuang, S.-L.; Ning, C. Z.; Woo, Alex (Technical Monitor)

    1999-01-01

    Second-order nonlinear optical processes including second-harmonic generation, optical rectification, and difference-frequency generation associated with intersubband transitions in wurtzite GaN/AlGaN quantum well (QW) are investigated theoretically. Taking into account the strain-induced piezoelectric (PZ) effects, we solve the electronic structure of the QW from coupled effective-mass Schrodinger equation and Poisson equation including the exchange-correlation effect under the local-density approximation. We show that the large PZ field in the QW breaks the symmetry of the confinement potential profile and leads to large second-order susceptibilities. We also show that the interband optical pump-induced electron-hole plasma results in an enhancement in the maximum value of the nonlinear coefficients and a redshift of the peak position in the nonlinear optical spectrum. By use of the difference-frequency generation, THz radiation can be generated from a GaN/Al(0.75)Ga(0.25)N with a pump laser of 1.55 micron.

  7. Enhanced sensitivity of piezoelectric pressure sensor with microstructured polydimethylsiloxane layer

    NASA Astrophysics Data System (ADS)

    Choi, Wook; Lee, Junwoo; Kyoung Yoo, Yong; Kang, Sungchul; Kim, Jinseok; Hoon Lee, Jeong

    2014-03-01

    Highly sensitive detection tools that measure pressure and force are essential in palpation as well as real-time pressure monitoring in biomedical applications. So far, measurement has mainly been done by force sensing resistors and field effect transistor (FET) sensors for monitoring biological pressure and force sensing. We report a pressure sensor by the combination of a piezoelectric sensor layer integrated with a microstructured Polydimethylsiloxane (μ-PDMS) layer. We propose an enhanced sensing tool to be used for analyzing gentle touches without the external voltage source that is used in FET sensors, by incorporating a microstructured PDMS layer in a piezoelectric sensor. By measuring the directly induced electrical charge from the microstructure-enhanced piezoelectric signal, we observed a 3-fold increased sensitivity in a signal response. Both fast signal relaxation from force removal and wide dynamic range from 0.23 to 10 kPa illustrate the good feasibility of the thin film piezoelectric sensor for mimicking human skin.

  8. Piezoelectric enhancement by surface effect in hydrofluorinated graphene bilayer

    SciTech Connect

    Kim, Hye Jung; Noor-A-Alam, Mohammad; Shin, Young-Han

    2015-04-14

    We investigated the piezoelectricity of dipolar hydrofluorinated graphene (C{sub 2}HF){sub n} multilayers with first-principles calculations. Our results reveal that the dipole moment decreases as the number of layers increases, because electron and hole carriers are induced at the top and bottom layers due to the depolarization field. These carriers make (C{sub 2}HF){sub n} multilayers more stable by decreasing the depolarization field in the material. Through the calculation of the average layer piezoelectric stress constant e{sub 31}/ℓ in ℓ-layer chair (C{sub 2}HF){sub n} multilayers, we confirmed that the piezoelectricity of the bilayer is about three times larger than that of the monolayer and bulk material. Moreover, we found that the electron and hole carriers on the top and bottom layers played a significant role in the piezoelectric enhancement of the bilayer.

  9. A field theory of piezoelectric media containing dislocations

    SciTech Connect

    Taupin, V. Fressengeas, C.; Ventura, P.; Lebyodkin, M.

    2014-04-14

    A field theory is proposed to extend the standard piezoelectric framework for linear elastic solids by accounting for the presence and motion of dislocation fields and assessing their impact on the piezoelectric properties. The proposed theory describes the incompatible lattice distortion and residual piezoelectric polarization fields induced by dislocation ensembles, as well as the dynamic evolution of these fields through dislocation motion driven by coupled electro-mechanical loading. It is suggested that (i) dislocation mobility may be enhanced or inhibited by the electric field, depending on the polarity of the latter, (ii) plasticity mediated by dislocation motion allows capturing long-term time-dependent properties of piezoelectric polarization. Due to the continuity of the proposed electro-mechanical framework, the stress/strain and polarization fields are smooth even in the dislocation core regions. The theory is applied to gallium nitride layers for validation. The piezoelectric polarization fields associated with bulk screw/edge dislocations are retrieved and surface potential modulations are predicted. The results are extended to dislocation loops.

  10. Enhanced piezoelectric response in the artificial ferroelectric polymer multilayers

    SciTech Connect

    Zhao, X. L.; Wang, J. L. E-mail: lin-tie@mail.sitp.ac.cn; Tian, B. B.; Liu, B. L.; Wang, X. D.; Sun, S.; Zou, Y. H.; Lin, T. E-mail: lin-tie@mail.sitp.ac.cn; Sun, J. L.; Meng, X. J.; Chu, J. H.

    2014-12-01

    An actuator with a high piezoelectric response, the ferroelectric polymer multilayer actuator, is described. The ferroelectric polymer multilayers consisting of alternative ferroelectric poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) copolymer and relaxor poly(vinylidene fluoride-trifluoroethylene-chlorofloroethylene) (P(VDF-TrFE-CFE)) terpolymer with different periodicities and fixed total thickness are prepared by the Langmuir-Blodgett technique. Both X-ray diffraction and Raman spectroscopic measurements indicate that the structure of the multilayer with thin alternating layer is similar to that of the ferroelectric copolymer. Compared with that of the copolymer, it is found that the piezoelectric coefficient of the multilayer could be improved by 57%. We attributed the enhanced piezoelectric response of the multilayers to the internal electric fields that arises from the electrostatic couplings between different layers.

  11. Composite lateral electric field excited piezoelectric resonator.

    PubMed

    Zaitsev, B D; Shikhabudinov, A M; Borodina, I A; Teplykh, A A; Kuznetsova, I E

    2017-01-01

    The novel method of suppression of parasitic oscillations in lateral electric field excited piezoelectric resonator is suggested. Traditionally such resonator represents the piezoelectric plate with two electrodes on one side of the plate. The crystallographic orientation of the plate is selected so that the tangential components of electric field excite bulk acoustic wave with given polarization travelling along the normal to the plate sides. However at that the normal components of field excite the parasitic Lamb waves and bulk waves of other polarization which deteriorate the resonant properties of the resonator. In this work we suggest to separate the source of the HF electric field and resounded piezoelectric plate by air gap. In this case the tangential components of the field in piezoelectric plate do not practically weaken but normal components significantly decrease. This method is realized on the composite resonator having the structure "glass plate with rectangular electrodes - air gap - plate of 128 Y-X lithium niobate." It has been shown that there exist the optimal value of the width gap which ensure the good quality of series and parallel resonances in frequency range 3-4MHz with record values of Q-factor of ∼15,000 in both cases.

  12. Radial-Electric-Field Piezoelectric Diaphragm Pumps

    NASA Technical Reports Server (NTRS)

    Bryant, Robert G.; Working, Dennis C.; Mossi, Karla; Castro, Nicholas D.; Mane, Pooma

    2009-01-01

    In a recently invented class of piezoelectric diaphragm pumps, the electrode patterns on the piezoelectric diaphragms are configured so that the electric fields in the diaphragms have symmetrical radial (along-the-surface) components in addition to through-the-thickness components. Previously, it was accepted in the piezoelectric-transducer art that in order to produce the out-of-plane bending displacement of a diaphragm needed for pumping, one must make the electric field asymmetrical through the thickness, typically by means of electrodes placed on only one side of the piezoelectric material. In the present invention, electrodes are placed on both sides and patterned so as to produce substantial radial as well as through-the-thickness components. Moreover, unlike in the prior art, the electric field can be symmetrical through the thickness. Tests have shown in a given diaphragm that an electrode configuration according to this invention produces more displacement than does a conventional one-sided electrode pattern. The invention admits of numerous variations characterized by various degrees of complexity. Figure 1 is a simplified depiction of a basic version. As in other piezoelectric diaphragm pumps of similar basic design, the prime mover is a piezoelectric diaphragm. Application of a suitable voltage to the electrodes on the diaphragm causes it to undergo out-of-plane bending. The bending displacement pushes a fluid out of, or pulls the fluid into, a chamber bounded partly by the diaphragm. Also as in other diaphragm pumps in general, check valves ensure that the fluid flows only in through one port and only out through another port.

  13. Pressure and electric field effects on piezoelectric responses of KNbO3

    NASA Astrophysics Data System (ADS)

    Liang, Linyun; Li, Y. L.; Xue, Fei; Chen, Long-Qing

    2012-09-01

    The dielectric and piezoelectric properties of a KNbO3 single crystal under applied hydrostatic pressure and positive bias electric field are investigated using phenomenological Landau-Ginzburg-Devonshire thermodynamic theory. It is shown that the hydrostatic pressure effect on the dielectric and piezoelectric properties is similar to temperature, suggesting a common underlying mechanism for the piezoelectric anisotropy and its enhancement. The stable phase diagram of KNbO3 as a function of temperature and positive bias electric field is constructed. The maximum piezoelectric coefficient d33o* varying with temperature and electric field is calculated.

  14. Pressure and electric field effects on piezoelectric responses of KNbO3

    SciTech Connect

    Liang, Linyun; Li, Yulan; Xue, Fei; Chen , L.Q.

    2012-09-18

    The dielectric and piezoelectric properties of a KNbO3 single crystal under applied hydrostatic pressure and positive bias electric field are investigated using phenomenological Landau-Ginzburg-Devonshire (LGD) thermodynamic theory. It is shown that the hydrostatic pressure effect on the dielectric and piezoelectric properties is similar to temperature, suggesting a common underlying mechanism for the piezoelectric anisotropy and its enhancement. The stable phase diagram of KNbO3 as a function of temperature and positive bias electric field is constructed. The maximum piezoelectric coefficient d33o* varying with temperature and electric field is calculated.

  15. Enhanced piezoelectric performance from carbon fluoropolymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Baur, Cary; DiMaio, Jeffrey R.; McAllister, Elliot; Hossini, Reza; Wagener, Earl; Ballato, John; Priya, Shashank; Ballato, Arthur; Smith, Dennis W.

    2012-12-01

    The piezoelectric performance of polyvinylidene fluoride (PVDF) is shown to double through the controlled incorporation of carbon nanomaterial. Specifically, PVDF composites containing carbon fullerenes (C60) and single-walled carbon nanotubes (SWNT) are fabricated over a range of compositions and optimized for their Young's modulus, dielectric constant, and d31 piezoelectric coefficient. Thermally stimulated current measurements show a large increase in internal charge and polarization in the composites over pure PVDF. The electromechanical coupling coefficients (k31) at optimal loading levels are found to be 1.84 and 2 times greater than pure PVDF for the PVDF-C60 and PVDF-SWNT composites, respectively. Such property-enhanced nanocomposites could have significant benefit to electromechanical systems employed for structural sensing, energy scavenging, sonar, and biomedical imaging.

  16. Enhanced converse magnetoelectric effect in cylindrical piezoelectric-magnetostrictive composites

    NASA Astrophysics Data System (ADS)

    Wu, Gaojian; Zhang, Ru; Zhang, Ning

    2016-10-01

    Enhanced converse magnetoelectric (ME) effect has been experimentally observed in cylindrical PZT-Terfenol-D piezoelectric-magnetostrictive bilayered composites, where the piezoelectric and magnetostrictive components are coupled through normal stresses instead of shear stresses that act in most of previous multiferroic composites. A theoretical model based on elastodynamics analysis has been proposed to describe the frequency response of converse ME effect for axial and radial modes in the bilayered cylindrical composites. The theory shows good agreement with the experimental results. The different variation tendency of resonant converse ME coefficient, as well as different variation rate of resonance frequency with bias magnetic field for axial and radial modes is interpreted in terms of demagnetizing effect. This work is of theoretical and technological significance for the application of converse ME effect as magnetic sensor, transducers, coil-free flux switch, etc.

  17. Power enhancement of piezoelectric transformers by adding thermal pad

    NASA Astrophysics Data System (ADS)

    Su, Y. H.; Liu, Y. P.; Vasic, D.; Costa, F.

    2012-04-01

    It is well known that power density of piezoelectric transformers is limited by mechanical stress. The power density of piezoelectric transformers calculated by the stress boundary can reach 330 W/cm3. However, no piezoelectric transformer has ever reached such a high power density in practice. The power density of the piezoelectric transformer is limited to 33 W/cm3 typically. This fact implies that there is another physical limitation in piezoelectric transformer. In fact, it is also known that piezoelectric material is constrained by vibration velocity. Once the vibration velocity is too large, the piezoelectric transformer generates heat until it cracks. To explain the instability of piezoelectric transformer, we will first model the relationship between vibration velocity and resulting heat by a physical feedback loop. It will be shown that the vibration velocity as well as the heat generation determines the loop gain. A large vibration velocity and heat may cause the feedback loop to enter into an unstable state. Therefore, to enhance the power capacity of piezoelectric transformer, the heat needs to be dissipated. In this paper, we used commercial thermal pads on the surface of the piezoelectric transformer to dissipate the heat. The mechanical current of piezoelectric transformers can move from 0.382A/2W to 0.972A/9W at a temperature of 55°C experimentally. It implies that the power capacity possibly increases 3 times in the piezoelectric material. Moreover, piezoelectric transformers that are well suited in applications of high voltage/low current becomes also well suited for low voltage/high current power supplies that are widely spread. This technique not only increases the power capacity of the piezoelectric transformer but also allows it to be used in enlarged practical applications. In this paper, the theoretical modeling will be detailed and verified by experiments.

  18. Enhanced piezoelectric performance of composite sol-gel thick films evaluated using piezoresponse force microscopy.

    PubMed

    Liu, Yuanming; Lam, Kwok Ho; Kirk Shung, K; Li, Jiangyu; Zhou, Qifa

    2013-05-14

    Conventional composite sol-gel method has been modified to enhance the piezoelectric performance of ceramic thick films. Lead zirconate titanate (PZT) and lead magnesium niobate-lead titanate (PMN-PT) thick films were fabricated using the modified sol-gel method for ultrasonic transducer applications. In this work, piezoresponse force microscopy was employed to evaluate the piezoelectric characteristics of PZT and PMN-PT composite sol-gel thick films. The images of the piezoelectric response and the strain-electric field hysteresis loop behavior were measured. The effective piezoelectric coefficient (d33,eff) of the films was determined from the measured loop data. It was found that the effective local piezoelectric coefficient of both PZT and PMN-PT composite films is comparable to that of their bulk ceramics. The promising results suggest that the modified composite sol-gel method is a promising way to prepare the high-quality, crack-free ceramic thick films.

  19. Piezoelectric resonance enhanced microwave and optoelectronic interactive devices

    NASA Astrophysics Data System (ADS)

    McIntosh, Robert

    Electro-optic (EO) devices that modulate optical signals by electric fields are an integrative part of the photonics industry and device optimization is an important area of research. As applications move to large bandwidth and higher frequency, low electro-optic effects and the requirement for large dimension become restrictive for microwave-optical devices. Both experimental and computational evaluations indicate that strain and polarization distribution have a significant impact on electromagnetic wave propagation resulting from a resonant structure; however, no systematic study or fundamental understandings are available. This dissertation research has been carried out to study and further develop the subject of piezoelectric resonance enhanced electro-acoustic-optic process, in order to improve the sensitivity and efficiency of electro-optic sensors and to explore novel applications. Many finite element models have been constructed for evaluating the mechanisms of the phenomena and the effectiveness of the device structure. The enhancement in transmission is found to be directly related to the strain-coupled local polarization. At piezoelectric resonance oscillating dipoles or local polarizations become periodic in the material and have the greatest impact on transmission. Results suggest that the induced charge distribution by a piezoelectric material at certain resonant frequencies is effective for aiding or impeding the transmission of a propagating wave. The behavior of both piezoelectric-defined (or intrinsic piezoelectric materials) and engineered periodic structures are reported. The piezoelectric response of the surface displacement of samples is investigated using an ultra-high frequency laser Doppler vibrometer. A two dimensional view of the surface is obtained and the surface displacement, velocity and acceleration are compared to the electro-optic response under the resonant condition. A study of the acousto-optic (AO) effect in a family of oxide

  20. Micro-structured PDMS piezoelectric enhancement through charging conditions

    NASA Astrophysics Data System (ADS)

    Kachroudi, Achraf; Basrour, Skandar; Rufer, Libor; Sylvestre, Alain; Jomni, Fathi

    2016-10-01

    Micro-structured cellular polydimethylsiloxane (PDMS) materials were prepared by a low-cost molding process allowing us to control geometry and sample size. Cellular structures are charged with a triangular quasi-static voltage with amplitudes between 1 kV and 4 kV and a frequency of 0.5 Hz fixed after having evaluated the conditions enhancing the piezoelectric response of the cellular PDMS. The piezo-electret PDMS material charged at room temperature has a piezoelectric coefficient d 33 of 350 pC/N, which is ten times larger than that of polyvinylidene fluoride. The high piezoelectric coefficient with a very low elastic modulus of 300 kPa makes these materials very useful for wearable device applications. The piezoelectric coefficient d 33 of the samples poled at high temperatures improves thermal stability but reduces PDMS piezo-electret piezoelectricity, which is explained by the structure’s stiffness. These results are useful and allow us to set the conditions for the preparation of the piezo-electret materials according to desired applications.

  1. Development of enhanced piezoelectric energy harvester induced by human motion.

    PubMed

    Minami, Y; Nakamachi, E

    2012-01-01

    In this study, a high frequency piezoelectric energy harvester converted from the human low vibrated motion energy was newly developed. This hybrid energy harvester consists of the unimorph piezoelectric cantilever and a couple of permanent magnets. One magnet was attached at the end of cantilever, and the counterpart magnet was set at the end of the pendulum. The mechanical energy provided through the human walking motion, which is a typical ubiquitous presence of vibration, is converted to the electric energy via the piezoelectric cantilever vibration system. At first, we studied the energy convert mechanism and the performance of our energy harvester, where the resonance free vibration of unimorph cantilever with one permanent magnet under a rather high frequency was induced by the artificial low frequency vibration. The counterpart magnet attached on the pendulum. Next, we equipped the counterpart permanent magnet pendulum, which was fluctuated under a very low frequency by the human walking, and the piezoelectric cantilever, which had the permanent magnet at the end. The low-to-high frequency convert "hybrid system" can be characterized as an enhanced energy harvest one. We examined and obtained maximum values of voltage and power in this system, as 1.2V and 1.2 µW. Those results show the possibility to apply for the energy harvester in the portable and implantable Bio-MEMS devices.

  2. Piezoelectric annular array for large depth of field photoacoustic imaging

    PubMed Central

    Passler, K.; Nuster, R.; Gratt, S.; Burgholzer, P.; Paltauf, G.

    2011-01-01

    A piezoelectric detection system consisting of an annular array is investigated for large depth of field photoacoustic imaging. In comparison to a single ring detection system, X-shaped imaging artifacts are suppressed. Sensitivity and image resolution studies are performed in simulations and in experiments and compared to a simulated spherical detector. In experiment an eight ring detection systems offers an extended depth of field over a range of 16 mm with almost constant lateral resolution. PMID:21991555

  3. r-Shaped hybrid nanogenerator with enhanced piezoelectricity.

    PubMed

    Han, Mengdi; Zhang, Xiao-Sheng; Meng, Bo; Liu, Wen; Tang, Wei; Sun, Xuming; Wang, Wei; Zhang, Haixia

    2013-10-22

    Piezoelectric and triboelectric nanogenerators (NGs) have been proposed in the past few years to effectively harvest mechanical energy from the environment. Here, a polydimethylsiloxane (PDMS) layer is placed under the aluminum electrode of polyvinylidene fluoride (PVDF), thus forming an r-shaped hybrid NG. Micro/nanostructures have been fabricated on the PDMS surface and the aluminum electrodes of PVDF to enhance the output performance. Power densities of the piezoelectric part and the triboelectric part are 10.95 and 2.04 mW/cm(3), respectively. Moreover, influence of the triboelectric charges on the piezoelectric output voltage is investigated. Both finite element method simulations and experimental measurements are conducted to verify this phenomenon. The novel hybrid NG is also demonstrated as a power source for consumer electronics. Through one cycle of electric generation, 10 light-emitting diodes are lighted up instantaneously, and a 4-bit liquid crystal display can display continuously for more than 15 s. Besides, the device is integrated into a keyboard to harvest energy in the typing process.

  4. Enhanced Magnetoelectric Coupling in Layered Structure of Piezoelectric Bimorph and Metallic Alloy

    NASA Astrophysics Data System (ADS)

    Petrov, V. M.; Bichurin, M. I.; Lavrentyeva, K. V.; Leontiev, V. S.

    2016-08-01

    We have investigated the enhanced magnetoelectric (ME) coupling in a layered structure of piezoelectric bimorph and magnetostrictive metallic alloy. The observed ME coefficient in the piezoelectric bimorph-based structure was found to be two times higher than in the traditional piezoelectric/magnetostrictive bilayer. The observed enhancement in ME coupling strength is related to equal signs of induced voltage in both lead zirconate titanate layers with opposite poling directions due to the flexural deformations. The piezoelectric bimorph-based structure has promising potential for sensor and technological applications.

  5. Silver nanowire dopant enhancing piezoelectricity of electrospun PVDF nanofiber web

    NASA Astrophysics Data System (ADS)

    Li, Baozhang; Zheng, Jianming; Xu, Chunye

    2013-08-01

    A highly sensitive flexible piezoelectric material is developed by using a composite nanofibers web of polymer and metal. The nanofibers webs are made by electrospinning a mixed solution of poly(vinylidene fluoride) (PVDF) and silver nanowires (AgNWs) in the co-solvent of dimethyl formamide and acetone. SEM images show that the obtained webs are composed of AgNWs doped PVDF fibers with diameters ranging from 200nm to 500nm. Our FTIR and XRD results indicate that doping AgNWs into PVDF fiber can enhance the contents of beta phase of the PVDF. UV-Vis spectrum shows a slightly red shift at 324 nm and 341 nm after the AgNWs doping into PVDF, proving the presence of interaction between AgNWs and the PVDF polymer chain. The piezoelectric constant d33 of the nanofibers webs tested with a homemade system, reveals a good agreement with FTIR and XRD characteristic, and the highest one is up to 29.8 pC/N for the nanofibers webs containing 1.5% AgNWs, which is close to that of poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE), 77/23). This study may provide a way to develop high-performance flexible sensors.

  6. Contactless ultrasonic energy transfer for wireless systems: acoustic-piezoelectric structure interaction modeling and performance enhancement

    NASA Astrophysics Data System (ADS)

    Shahab, S.; Erturk, A.

    2014-12-01

    There are several applications of wireless electronic components with little or no ambient energy available to harvest, yet wireless battery charging for such systems is still of great interest. Example applications range from biomedical implants to sensors located in hazardous environments. Energy transfer based on the propagation of acoustic waves at ultrasonic frequencies is a recently explored alternative that offers increased transmitter-receiver distance, reduced loss and the elimination of electromagnetic fields. As this research area receives growing attention, there is an increased need for fully coupled model development to quantify the energy transfer characteristics, with a focus on the transmitter, receiver, medium, geometric and material parameters. We present multiphysics modeling and case studies of the contactless ultrasonic energy transfer for wireless electronic components submerged in fluid. The source is a pulsating sphere, and the receiver is a piezoelectric bar operating in the 33-mode of piezoelectricity with a fundamental resonance frequency above the audible frequency range. The goal is to quantify the electrical power delivered to the load (connected to the receiver) in terms of the source strength. Both the analytical and finite element models have been developed for the resulting acoustic-piezoelectric structure interaction problem. Resistive and resistive-inductive electrical loading cases are presented, and optimality conditions are discussed. Broadband power transfer is achieved by optimal resistive-reactive load tuning for performance enhancement and frequency-wise robustness. Significant enhancement of the power output is reported due to the use of a hard piezoelectric receiver (PZT-8) instead of a soft counterpart (PZT-5H) as a result of reduced material damping. The analytical multiphysics modeling approach given in this work can be used to predict and optimize the coupled system dynamics with very good accuracy and dramatically

  7. Ferroelectric instabilities and enhanced piezoelectric response in Ce modified BaTiO3 lead-free ceramics

    NASA Astrophysics Data System (ADS)

    Brajesh, Kumar; Kalyani, Ajay Kumar; Ranjan, Rajeev

    2015-01-01

    The crystal structure, ferroelectric, and piezoelectric behaviors of the Ba(Ti1-xCex)O3 solid solution have been investigated at close composition intervals in the dilute concentration regime. Ce concentration as low as 2 mol. % induces tetragonal-orthorhombic instability and coexistence of the phases, leading to enhanced high-field strain and direct piezoelectric response. Detailed structural analysis revealed tetragonal + orthorhombic phase coexistence for x = 0.02, orthorhombic for 0.03 ≤ x ≤ 0.05, and orthorhombic + rhombohedral for 0.06 ≤ x ≤ 0.08. The results suggest that Ce-modified BaTiO3 is a potential lead-free piezoelectric material.

  8. Power enhancement of piezoelectric transformers by adding heat transfer equipment.

    PubMed

    Su, Yu-Hao; Liu, Yuan-Ping; Vasic, Dejan; Wu, Wen-Jong; Costa, François; Lee, Chih-Kung

    2012-10-01

    It is known that piezoelectric transformers have several inherent advantages compared with conventional electromagnetic transformers. However, the maximum power capacity of piezoelectric transformers is not as large as electromagnetic transformers in practice, especially in the case of high output current. The theoretical power density of piezoelectric transformers calculated by stress boundary can reach 330 W/cm(3), but no piezoelectric transformer has ever reached such a high power density in practice. The power density of piezoelectric transformers is limited to 33 W/cm(3) in practical applications. The underlying reason is that the maximum passing current of the piezoelectric material (mechanical current) is limited by the temperature rise caused by heat generation. To increase this current and the power capacity, we proposed to add a thermal pad to the piezoelectric transformer to dissipate heat. The experimental results showed that the proposed techniques can increase by 3 times the output current of the piezoelectric transformer. A theoretical-phenomenological model which explains the relationship between vibration velocity and generated heat is also established to verify the experimental results.

  9. Coupled mixed-field laminate theory and finite element for smart piezoelectric composite shell structures

    NASA Technical Reports Server (NTRS)

    Saravanos, Dimitris A.

    1996-01-01

    Mechanics for the analysis of laminated composite shells with piezoelectric actuators and sensors are presented. A new mixed-field laminate theory for piezoelectric shells is formulated in curvilinear coordinates which combines single-layer assumptions for the displacements and a layerwise representation for the electric potential. The resultant coupled governing equations for curvilinear piezoelectric laminates are described. Structural mechanics are subsequently developed and an 8-node finite-element is formulated for the static and dynamic analysis of adaptive composite structures of general laminations containing piezoelectric layers. Evaluations of the method and comparisons with reported results are presented for laminated piezoelectric-composite plates, a closed cylindrical shell with a continuous piezoceramic layer and a laminated composite semi-circular cantilever shell with discrete cylindrical piezoelectric actuators and/or sensors.

  10. Surface mapping of field-induced piezoelectric strain at elevated temperature employing full-field interferometry.

    PubMed

    Stevenson, Tim; Quast, Tatjana; Bartl, Guido; Schmitz-Kempen, Thorsten; Weaver, Paul M

    2015-01-01

    Piezoelectric actuators and sensors are widely used for flow control valves, including diesel injectors, ultrasound generation, optical positioning, printing, pumps, and locks. Degradation and failure of material and electrical properties at high temperature typically limits these applications to operating temperatures below 200°C, based on the ubiquitous Pb(Zr,Ti)O3 ceramic. There are, however, many applications in sectors such as automotive, aerospace, energy and process control, and oil and gas, where the ability to operate at higher temperatures would open up new markets for piezoelectric actuation. Presented here is a review of recent progress and initial results toward a European effort to develop measurement techniques to characterize high-temperature materials. Full-field, multi-wavelength absolute length interferometry has, for the first time, been used to map the electric-field-induced piezoelectric strain across the surface of a PZT ceramic. The recorded variation as a function of temperature has been evaluated against a newly developed commercial single-beam system. Conventional interferometry allows measurement of the converse piezoelectric effect with high precision and resolution, but is often limited to a single point, average measurement and to limited sample environments because of optical aberrations in varying atmospheres. Here, the full-field technique allows the entire surface to be analyzed for strain and, in a bespoke sample chamber, for elevated temperatures.

  11. Enhancing the piezoelectric properties of flexible hybrid AlN materials using semi-crystalline parylene

    NASA Astrophysics Data System (ADS)

    Jackson, Nathan; Mathewson, Alan

    2017-04-01

    Flexible piezoelectric materials are desired for numerous applications including biomedical, wearable, and flexible electronics. However, most flexible piezoelectric materials are not compatible with CMOS fabrication technology, which is desired for most MEMS applications. This paper reports on the development of a hybrid flexible piezoelectric material consisting of aluminium nitride (AlN) and a semi-crystalline polymer substrate. Various types of semi-crystalline parylene and polyimide materials were investigated as the polymer substrate. The crystallinity and surfaces of the polymer substrates were modified by micro-roughening and annealing in order to determine the effects on the AlN quality. The AlN crystallinity and piezoelectric properties decreased when the polymer surfaces were treated with O2 plasma. However, increasing the crystallinity of the parylene substrate prior to deposition of AlN caused enhanced c-axis (002) AlN crystallinity and piezoelectric response of the AlN. Piezoelectric properties of 200 °C annealed parylene-N substrate resulted in an AlN d 33 value of 4.87 pm V‑1 compared to 2.17 pm V‑1 for AlN on polyimide and 4.0 pm V‑1 for unannealed AlN/parylene-N. The electrical response measurements to an applied force demonstrated that the parylene/AlN hybrid material had higher V pp (0.918 V) than commercial flexible piezoelectric material (PVDF) (V pp 0.36 V). The results in this paper demonstrate that the piezoelectric properties of a flexible AlN hybrid material can be enhanced by increasing the crystallinity of the polymer substrate, and the enhanced properties can function better than previous flexible piezoelectrics.

  12. An adaptive piezoelectric vibration absorber enhanced by a negative capacitance applied to a shell structure

    NASA Astrophysics Data System (ADS)

    Gripp, J. A. B.; Góes, L. C. S.; Heuss, O.; Scinocca, F.

    2015-12-01

    Piezoelectric shunt damping is a well-known technique to damp mechanical vibrations of a structure, using a piezoelectric transducer to convert mechanical vibration energy into electrical energy, which is dissipated in an electrical resistance. Resonant shunts consisting of a resistance and an inductance connected to a piezoelectric transducer are used to damp structural vibrations in narrow frequency bands, but their performance is very sensitive to variations in structural modal frequencies and transducer capacitance. In order to overcome this drawback, a piezoelectric shunt damping technique with improved performance and robustness is presented in this paper. The design of the adaptive circuit considers the variation of the host structure’s natural frequency as a project parameter. This paper describes an adaptive resonant piezoelectric vibration absorber enhanced by a synthetic negative capacitance applied to a shell structure. The resonant shunt circuit autonomously adapts its inductance value by comparing the phase difference of the vibration velocity and the current flowing through the shunt circuit. Moreover, a synthetic negative capacitance is added to the shunt circuit to enhance the vibration attenuation provided by the piezoelectric absorber. The circuitry is implemented using analog components. Validation of the proposed method is done by bonding the piezoelectric absorber on a free-formed metallic shell.

  13. Enhanced Piezoelectric Response due to Polarization Rotation in Cobalt-Substituted BiFeO3 Epitaxial Thin Films.

    PubMed

    Shimizu, Keisuke; Hojo, Hajime; Ikuhara, Yuichi; Azuma, Masaki

    2016-10-01

    Polarization rotation induced by an external electric field in piezoelectric materials such as PbZr1-x Tix O3 is generally regarded as the origin of their large piezoelectric responses. Here, the piezoelectric responses of high-quality cobalt-substituted BiFeO3 epitaxial thin films with monoclinic distortions are systematically examined. It is demonstrated that polarization rotation plays a crucial role in improving the piezoelectric responses in this material.

  14. Energy harvesting from stray power-frequency magnetic field employing a piezoelectric unimorph based heterostructure

    NASA Astrophysics Data System (ADS)

    He, Wei; Lu, Yueran; Zhang, Jitao; Qu, Chiwen; Che, Gaofeng; Peng, Jiancai

    2016-03-01

    An energy harvester using a piezoelectric unimorph based heterostructure is presented to convert stray power-frequency (50 Hz or 60 Hz) magnetic field energy into electrical energy. The harvester consists a piezoelectric unimorph and a U-shaped mass structure. The U-shaped mass structure with two parallel bar magnets leads to a large rotary inertia for the given proof mass. An enhanced exciting torque is induced on the unimorph and the response of the harvester to the external magnetic field is strengthened. Under the resonant frequency of 50 Hz, the harvester produces a power of 154.6 µW with a matching load resistance of 199 kΩ at a magnetic field of 0.5 Oe. Through an up-conversion management circuit, the energy harvester can successfully drive a wireless sensor node with high power consumption (90 mW at transmitting and 18 mW at receiving) at a duration of 205 ms. Note to the reader: The article number 30902 in PDF file was a mistake and has been corrected in 30903 on May 11, 2016.

  15. Theoretical and experimental research on the influence of multiple piezoelectric effects on physical parameters of piezoelectric actuator

    NASA Astrophysics Data System (ADS)

    Shi, Liping; Zhou, Haimin; Huang, Jie; Tan, Jiliang

    2015-04-01

    Compared with the traditional actuator of machinery and electricity, the piezoelectric actuator has the advantages of a compact structure, small volume, no mechanical friction, athermancy and no electromagnetic interference. Therefore, it has high application value in the fields of MEMS, bioengineering, medical science and so on. This article draws conclusions from the influence of multiple piezoelectric effects on the physical parameters (dielectric coefficient, equivalent capacity, energy conversion and piezoelectric coefficient) of piezoelectric actuators. These data from theoretical and experimental research show the following: (1) The rate between the dielectric coefficient of piezoelectric in mechanical freedom and clamping is obtained from the secondary direct piezoelectric effect, which enhances the dielectric property, increases the dielectric coefficient and decreases the coefficient of dielectric isolation; (2) Under external field, En ( ex ) = E 1 , exterior stress T = 0, that is to say, under the boundary condition of mechanical freedom, piezoelectric can store electric energy and elasticity, which obtains power density, elastic density and an electromechanical coupling factor; (3) According to the piezoelectric strain Si ( 1 ) , piezoelectric displacement Dm ( 2 ) and piezoelectric strain Si ( 3 ) of multiple piezoelectric effects, when the dielectric coefficient of the first converse piezoelectric effect ɛ33 is 1326 and the dielectric coefficient of the secondary direct piezoelectric effect increases to 3336, the dielectric coefficient of the ceramic chip increases. When the piezoelectric coefficient of the first converse piezoelectric effect d33 is 595 and the piezoelectric coefficient of the secondary direct piezoelectric effect decreases to 240, the piezoelectric coefficient of the ceramic chip will decrease. It is of major significance both in the applications and in basic theory to research the influence of multiple piezoelectric effects on the

  16. Multimodal cantilevers with novel piezoelectric layer topology for sensitivity enhancement

    PubMed Central

    Ruppert, Michael G; Yong, Yuen Kuan

    2017-01-01

    Self-sensing techniques for atomic force microscope (AFM) cantilevers have several advantageous characteristics compared to the optical beam deflection method. The possibility of down scaling, parallelization of cantilever arrays and the absence of optical interference associated imaging artifacts have led to an increased research interest in these methods. However, for multifrequency AFM, the optimization of the transducer layout on the cantilever for higher order modes has not been addressed. To fully utilize an integrated piezoelectric transducer, this work alters the layout of the piezoelectric layer to maximize both the deflection of the cantilever and measured piezoelectric charge response for a given mode with respect to the spatial distribution of the strain. On a prototype cantilever design, significant increases in actuator and sensor sensitivities were achieved for the first four modes without any substantial increase in sensor noise. The transduction mechanism is specifically targeted at multifrequency AFM and has the potential to provide higher resolution imaging on higher order modes. PMID:28326225

  17. Enhanced High Temperature Piezoelectrics Based on BiScO3-PbTiO3 Ceramics

    NASA Technical Reports Server (NTRS)

    Sehirlioglu, Alp; Sayir, Ali; Dynys, Fred

    2009-01-01

    High-temperature piezoelectrics are a key technology for aeronautics and aerospace applications such as fuel modulation to increase the engine efficiency and decrease emissions. The principal challenge for the insertion of piezoelectric materials is the limitation on upper use temperature which is due to low Curie-Temperature (TC) and increasing electrical conductivity. BiScO3-PbTiO3 (BS-PT) system is a promising candidate for improving the operating temperature for piezoelectric actuators due to its high TC (greater than 400 C). Bi2O3 was shown to be a good sintering aid for liquid phase sintering resulting in reduced grain size and increased resistivity. Zr doped and liquid phase sintered BS-PT ceramics exhibited saturated and square hysteresis loops with enhanced remenant polarization (37 microC per square centimeter) and coercive field (14 kV/cm). BS-PT doped with Mn showed enhanced field induced strain (0.27% at 50kV/cm). All the numbers indicated in parenthesis were collected at 100 C.

  18. Enhanced piezoelectric properties of vertically aligned single-crystalline NKN nano-rod arrays

    PubMed Central

    Kang, Min-Gyu; Oh, Seung-Min; Jung, Woo-Suk; Gyu Moon, Hi; Baek, Seung-Hyub; Nahm, Sahn; Yoon, Seok-Jin; Kang, Chong-Yun

    2015-01-01

    Piezoelectric materials capable of converting between mechanical and electrical energy have a great range of potential applications in micro- and nano-scale smart devices; however, their performance tends to be greatly degraded when reduced to a thin film due to the large clamping force by the substrate and surrounding materials. Herein, we report an effective method for synthesizing isolated piezoelectric nano-materials as means to relax the clamping force and recover original piezoelectric properties of the materials. Using this, environmentally friendly single-crystalline NaxK1-xNbO3 (NKN) piezoelectric nano-rod arrays were successfully synthesized by conventional pulsed-laser deposition and demonstrated to have a remarkably enhanced piezoelectric performance. The shape of the nano-structure was also found to be easily manipulated by varying the energy conditions of the physical vapor. We anticipate that this work will provide a way to produce piezoelectric micro- and nano-devices suitable for practical application, and in doing so, open a new path for the development of complex metal-oxide nano-structures. PMID:25955763

  19. Enhanced piezoelectric properties of vertically aligned single-crystalline NKN nano-rod arrays.

    PubMed

    Kang, Min-Gyu; Oh, Seung-Min; Jung, Woo-Suk; Moon, Hi Gyu; Baek, Seung-Hyub; Nahm, Sahn; Yoon, Seok-Jin; Kang, Chong-Yun

    2015-05-08

    Piezoelectric materials capable of converting between mechanical and electrical energy have a great range of potential applications in micro- and nano-scale smart devices; however, their performance tends to be greatly degraded when reduced to a thin film due to the large clamping force by the substrate and surrounding materials. Herein, we report an effective method for synthesizing isolated piezoelectric nano-materials as means to relax the clamping force and recover original piezoelectric properties of the materials. Using this, environmentally friendly single-crystalline NaxK1-xNbO3 (NKN) piezoelectric nano-rod arrays were successfully synthesized by conventional pulsed-laser deposition and demonstrated to have a remarkably enhanced piezoelectric performance. The shape of the nano-structure was also found to be easily manipulated by varying the energy conditions of the physical vapor. We anticipate that this work will provide a way to produce piezoelectric micro- and nano-devices suitable for practical application, and in doing so, open a new path for the development of complex metal-oxide nano-structures.

  20. Field stability of piezoelectric shear properties in PIN-PMN-PT crystals under large drive field.

    PubMed

    Zhang, Shujun; Li, Fei; Luo, Jun; Xia, Ru; Hackenberger, Wesley; Shrout, Thomas

    2011-02-01

    The coercive fields (E(C)) of Pb(In₀.₅Nb₀.₅)O₃-Pb(Mg(¹/₃)Nb(²/₃)O₃-PbTiO₃ (PIN-PMN-PT) ternary single crystals were found to be 5 kV/cm, double the value of binary Pb(Mg(¹/₃)Nb(²/₃)O₃-PbTiO₃ (PMNT) crystals, further increased to 6 to 9 kV/cm using Mn modifications. In addition to an increased EC, the acceptor modification resulted in the developed internal bias (E(int)), on the order of ~1 kV/cm. The piezoelectric shear properties of unmodified and Mn-modified PIN-PMN-PT crystals with various domain configurations were investigated. The shear piezoelectric coefficients and electromechanical coupling factors for different domain configurations were found to be >2000 pC/N and >0.85, respectively, with slightly reduced properties observed in Mn-modified tetragonal crystals. Fatigue/cycling tests performed on shearmode samples as a function of ac drive field level demonstrated that the allowable ac field levels (the maximum applied ac field before the occurrence of depolarization) were only ~2 kV/cm for unmodified crystals, less than half of their coercive field. Allowable ac drive levels were on the order of 4 to 6 kV/cm for Mn-modified crystals with rhombohedral/orthorhombic phase, further increased to 5 to 8 kV/cm in tetragonal crystals, because of their higher coercive fields. It is of particular interest that the allowable ac drive field level for Mn-modified crystals was found to be ≥ 60% of their coercive fields, because of the developed E(int), induced by the acceptor-oxygen vacancy defect dipoles.

  1. Enhanced performance of a GaN piezoelectric nanogenerator with an embedded nanoporous layer via the suppressed carrier screening effect

    NASA Astrophysics Data System (ADS)

    Kang, Jin-Ho; Jeong, Dae Kyung; Ha, Jun-Seok; Key Lee, June; Ryu, Sang-Wan

    2017-02-01

    Highly efficient nanoporous GaN-based piezoelectric nanogenerators (PNGs) were demonstrated using an electrochemical etching process. The output of the PNGs was enhanced significantly with increasing porosity because Fermi-level pinning depletes free carriers in nanoporous GaN with thin walls, which reduces the internal screening of piezoelectric charges by free carriers. With the average wall thickness below 30 nm, the output of the PNG increased significantly with decreasing wall thickness. It was attributed to the piezoelectric and mechanical size effects, i.e., enhanced piezoelectric polarization by increased piezoelectric coefficient and reduced elastic coefficient in a nano structure. The energy-harvesting capability of a PNG was sufficient for the operation of a microelectronic device when it was combined with a charging capacitor and rectifying circuit.

  2. Influence of the external electric field on propagation of Lamb waves in piezoelectric plates.

    PubMed

    Burkov, Sergei I; Zolotova, Olga P; Sorokin, Boris P

    2011-01-01

    The influence of the electric field on the properties of the Lamb and SH-waves in piezoelectric Bi(12)GeO(20) and La(3)Ga(5)SiO1(4) crystal plates has been investigated. Using basic equations and boundary conditions, the formulas for computer simulation have been obtained. The effect of acoustic modes hybridization has been considered.

  3. All-fiber transparent piezoelectric harvester with a cooperatively enhanced structure.

    PubMed

    Fuh, Yiin-Kuen; Ho, Hsi-Chun; Wang, Bo-Sheng; Li, Shan-Chien

    2016-10-28

    In this paper, we demonstrated a highly-flexible all-fiber based transparent piezoelectric harvester (ATPH) by using the direct-write, near-field electrospinning (NFES) technique and polyvinylidene fluoride (PVDF) micro/nano fibers (MNFs) as source materials. Here, we comprehensively show that transferred high performance transparent electrodes with Au-coated nanowire (NW) electrodes can be obtained using a facile and scalable combined fabrication route of both electrospinning and sputtering processes. Au-coated MNFs of a.c. 110 nm thick can significantly reduce junction resistance, which results in high transmittance (90%) at low sheet resistance (175 Ω sq(-1)). The Au-coated MNFs electrodes also show great flexibility and stretchability, which easily surpass the brittleness of indium tin oxide (ITO) films. Further improvement in ATPH performance was realized by rolling the device into a cylindrical shape, resulting in an increase in power output due to the cooperatively enhanced effect. The rolled ATPH with 0.34 cm diameter produces a high output voltage of ∼4.1 V, current ∼295 nA at a strain of 0.5% and 5 hz. This can efficiently run commercially available electronic components in a self-powered mode without any external electrical supply.

  4. All-fiber transparent piezoelectric harvester with a cooperatively enhanced structure

    NASA Astrophysics Data System (ADS)

    Fuh, Yiin-Kuen; Ho, Hsi-Chun; Wang, Bo-Sheng; Li, Shan-Chien

    2016-10-01

    In this paper, we demonstrated a highly-flexible all-fiber based transparent piezoelectric harvester (ATPH) by using the direct-write, near-field electrospinning (NFES) technique and polyvinylidene fluoride (PVDF) micro/nano fibers (MNFs) as source materials. Here, we comprehensively show that transferred high performance transparent electrodes with Au-coated nanowire (NW) electrodes can be obtained using a facile and scalable combined fabrication route of both electrospinning and sputtering processes. Au-coated MNFs of a.c. 110 nm thick can significantly reduce junction resistance, which results in high transmittance (90%) at low sheet resistance (175 Ω sq-1). The Au-coated MNFs electrodes also show great flexibility and stretchability, which easily surpass the brittleness of indium tin oxide (ITO) films. Further improvement in ATPH performance was realized by rolling the device into a cylindrical shape, resulting in an increase in power output due to the cooperatively enhanced effect. The rolled ATPH with 0.34 cm diameter produces a high output voltage of ˜4.1 V, current ˜295 nA at a strain of 0.5% and 5 hz. This can efficiently run commercially available electronic components in a self-powered mode without any external electrical supply.

  5. Large piezoelectricity in electric-field modified single crystals of SrTiO3

    NASA Astrophysics Data System (ADS)

    Khanbabaee, B.; Mehner, E.; Richter, C.; Hanzig, J.; Zschornak, M.; Pietsch, U.; Stöcker, H.; Leisegang, T.; Meyer, D. C.; Gorfman, S.

    2016-11-01

    Defect engineering is an effective and powerful tool to control the existing material properties and produce completely new ones, which are symmetry-forbidden in a defect-free crystal. For example, the application of a static electric field to a single crystal of SrTiO3 forms a strained near-surface layer through the migration of oxygen vacancies out of the area beneath the positively charged electrode. While it was previously shown that this near-surface phase holds pyroelectric properties, which are symmetry-forbidden in centrosymmetric bulk SrTiO3, this paper reports that the same phase is strongly piezoelectric. We demonstrate the piezoelectricity of this phase through stroboscopic time-resolved X-ray diffraction under alternating electric field and show that the effective piezoelectric coefficient d33 ranges between 60 and 100 pC/N. The possible atomistic origins of the piezoelectric activity are discussed as a coupling between the electrostrictive effect and spontaneous polarization of this near-surface phase.

  6. Second-order optical susceptibility in doped III-V piezoelectric semiconductors in the presence of a magnetostatic field

    NASA Astrophysics Data System (ADS)

    Lal, B.; Aghamkar, P.; Kumar, S.; Kashyap, M. K.

    2011-02-01

    A detailed analytical investigation of second-order optical susceptibility has been made in moderately doped III-V weakly piezoelectric semiconductor crystal, viz. n-InSb, in the absence and presence of an external magnetostatic field, using the coupled mode theory. The second-order optical susceptibility arises from the nonlinear interaction of a pump beam with internally generated density and acoustic perturbations. The effect of doping concentration, magnetostatic field and pump intensity on second-order optical susceptibility of III-V semiconductors has been studied in detail. The numerical estimates are made for n-type InSb crystals duly shined by pulsed 10.6 μm CO2 laser and efforts are made towards optimising the doping level, applied magnetostatic field and pump intensity to achieve a large value of second-order optical susceptibility and change of its sign. The enhancement in magnitude and change of sign of second-order optical susceptibility, in weakly piezoelectric III-V semiconductor under proper selection of doping concentration and externally applied magnetostatic field, confirms the chosen nonlinear medium as a potential candidate material for the fabrication of nonlinear optical devices. In particular, at B 0 = 14.1 T, the second-order susceptibility was found to be 3.4 × 10-7 (SI unit) near the resonance condition.

  7. DC magnetic field sensor based on electric driving and magnetic tuning in piezoelectric/magnetostrictive bilayer

    NASA Astrophysics Data System (ADS)

    Zhang, Long; Wing Or, Siu; Ming Leung, Chung; Ho, S. L.

    2014-05-01

    A dc magnetic field sensor possessing an interestingly high electric voltage-driven, magnetic field-tuned dc magnetoelectric (ME) effect is developed based on a bilayer of Pb(Zr, Ti)O3 piezoelectric transformer and Tb0.3Dy0.7Fe1.92 magnetostrictive substrate. The dc ME effect in the sensor, as evaluated experimentally and theoretically, is induced by driving the bilayer at its zero-field longitudinal resonance frequency (fr0) using an ac electric voltage (Vac) referenced at the input of the piezoelectric transformer, as well as, by tuning the field-dependent compliance and resonance characteristics of the bilayer with the dc magnetic field to be measured (Hdc) upon the negative-ΔE effect intrinsic in the magnetostrictive substrate. The sensor shows a good linear negative response of ac ME voltage (VME) at the output of the piezoelectric transformer to a broad range of Hdc of 0-350 Oe under a small Vac of 2.5 V peak at the designated fr0 of 125.3 kHz. This gives a high negative dc magnetic field sensitivity (S) of -1.58 mV/Oe.

  8. Concurrent operational modes and enhanced current sensitivity in heterostructure of magnetoelectric ring and piezoelectric transformer

    NASA Astrophysics Data System (ADS)

    Zhang, Shengyao; Ming Leung, Chung; Kuang, Wei; Wing Or, Siu; Ho, S. L.

    2013-05-01

    A heterostructure possessing two concurrent operational modes: current sensing (CS) mode and current transduction (CT) mode and an enhanced current sensitivity associated with the CT mode is proposed by combining a magnetoelectric ring (MER) with a piezoelectric transformer (PET). The MER is a ring-shaped magnetoelectric laminate having an axially polarized Pb(Zr, Ti)O3 (PZT) piezoelectric ceramic ring sandwiched between two circumferentially magnetized, inter-magnetically biased Tb0.3Dy0.7Fe1.92 (Terfenol-D) short-fiber/NdFeB magnet/epoxy three-phase magnetostrictive composite rings, while the PET is a Rosen-type PZT piezoelectric ceramic transformer. The current sensitivity (SI) and magnetoelectric voltage coefficient (αV) of the heterostructure in the two operational modes are evaluated theoretically and experimentally. The CS mode provides a large SI of ˜10 mV/A over a flat frequency range of 10 Hz-40 kHz with a high resonance SI of 157 mV/A at 62 kHz. The CT mode gives a 6.4-times enhancement in resonance SI, reaching 1000 mV/A at 62 kHz, as a result of the amplified vortex magnetoelectric effect caused by the vortex magnetoelectric effect in the MER, the matching of the resonance frequencies between the MER and the PET, and the resonance voltage step-up effect in the PET.

  9. Conformable amplified lead zirconate titanate sensors with enhanced piezoelectric response for cutaneous pressure monitoring

    NASA Astrophysics Data System (ADS)

    Dagdeviren, Canan; Su, Yewang; Joe, Pauline; Yona, Raissa; Liu, Yuhao; Kim, Yun-Soung; Huang, Yongan; Damadoran, Anoop R.; Xia, Jing; Martin, Lane W.; Huang, Yonggang; Rogers, John A.

    2014-08-01

    The ability to measure subtle changes in arterial pressure using devices mounted on the skin can be valuable for monitoring vital signs in emergency care, detecting the early onset of cardiovascular disease and continuously assessing health status. Conventional technologies are well suited for use in traditional clinical settings, but cannot be easily adapted for sustained use during daily activities. Here we introduce a conformal device that avoids these limitations. Ultrathin inorganic piezoelectric and semiconductor materials on elastomer substrates enable amplified, low hysteresis measurements of pressure on the skin, with high levels of sensitivity (~0.005 Pa) and fast response times (~0.1 ms). Experimental and theoretical studies reveal enhanced piezoelectric responses in lead zirconate titanate that follow from integration on soft supports as well as engineering behaviours of the associated devices. Calibrated measurements of pressure variations of blood flow in near-surface arteries demonstrate capabilities for measuring radial artery augmentation index and pulse pressure velocity.

  10. Charged vacancy induced enhanced piezoelectric response of reactive assistive IBSD grown AlN thin films

    NASA Astrophysics Data System (ADS)

    Sharma, Neha; Rath, Martando; Ilango, S.; Ravindran, T. R.; Ramachandra Rao, M. S.; Dash, S.; Tyagi, A. K.

    2017-01-01

    Piezoelectric response of AlN thin films was investigated in a AlN/Ti/Si(1 0 0) layer structure prepared by ion beam sputter deposition (IBSD) in reactive assistance of N+/\\text{N}2+ ions. The samples were characterized for their microstructure, piezoelectric response and charged defects using high resolution x-ray diffraction (HR-XRD), piezo force microscopy (PFM) and photoluminescence (PL) spectroscopy respectively. Our results show that the films are highly textured along the a-axis and charged native point defects are present in the microstructure. Phase images of these samples obtained from PFM show that the films are predominantly N-polar. The measured values of piezoelectric coefficient d 33(eff) for these samples are as high as 206  ±  20 pm V-1 and 668  ±  60 pm V-1 calculated by piezo response loop for AlN films of a thickness of 235 nm and 294 nm respectively. A mechanism for high d 33(eff) values is proposed with a suitable model based on the charged defects induced enhanced polarization in the dielectric continuum of AlN.

  11. Stress-induced piezoelectric field in GaN-based 450-nm light-emitting diodes

    SciTech Connect

    Tawfik, Wael Z.; Hyeon, Gil Yong; Lee, June Key

    2014-10-28

    We investigated the influence of the built-in piezoelectric field induced by compressive stress on the characteristics of GaN-based 450-nm light-emitting diodes (LEDs) prepared on sapphire substrates of different thicknesses. As the sapphire substrate thickness was reduced, the compressive stress in the GaN layer was released, resulting in wafer bowing. The wafer bowing-induced mechanical stress altered the piezoelectric field, which in turn reduced the quantum confined Stark effect in the InGaN/GaN active region of the LED. The flat-band voltage was estimated by measuring the applied bias voltage that induced a 180° phase shift in the electro-reflectance (ER) spectrum. The piezoelectric field estimated by the ER spectra changed by ∼110 kV/cm. The electroluminescence spectral peak wavelength was blue-shifted, and the internal quantum efficiency was improved by about 22% at a high injection current of 100 mA. The LED on the 60-μm-thick sapphire substrate exhibited the highest light output power of ∼59 mW at an injection current of 100 mA, with the operating voltage unchanged.

  12. High fidelity phase locked PIV measurements analysing the flow fields surrounding an oscillating piezoelectric fan

    NASA Astrophysics Data System (ADS)

    Jeffers, Nicholas; Nolan, Kevin; Stafford, Jason; Donnelly, Brian

    2014-07-01

    Piezoelectric fans have been studied extensively and are seen as a promising technology for thermal management due to their ability to provide quiet, reliable cooling with low power consumption. The fluid mechanics of an unconfined piezoelectric fan are complex which is why the majority of the literature to date confines the fan in an attempt to simplify the flow field. This paper investigates the fluid mechanics of an unconfined fan operating in its first vibration frequency mode. The piezoelectric fan used in this study measures 12.7mm × 70mm and resonates at 92.5Hz in air. A custom built experimental facility was developed to capture the fan's flow field using phase locked Particle Image Velocimetry (PIV). The phase locked PIV results are presented in terms of vorticity and show the formation of a horse shoe vortex. A three dimensional A2 criterion constructed from interpolated PIV measurements was used to identify the vortex core in the vicinity of the fan. This analysis was used to clearly identify the formation of a horse shoe vortex that turns into a hairpin vortex before it breaks up due to a combination of vortex shedding and flow along the fan blade. The results presented in this paper contribute to both the fluid dynamics and heat transfer literature concerning first mode fan oscillation.

  13. Fracture and buckling of piezoelectric nanowires subject to an electric field

    SciTech Connect

    Zhang, Jin; Wang, Chengyuan Adhikari, Sondipon

    2013-11-07

    Fracture and buckling are major failure modes of thin and long nanowires (NWs), which could be affected significantly by an electric field when piezoelectricity is involved in the NWs. This paper aims to examine the issue based on the molecular dynamics simulations, where the gallium nitride (GaN) NWs are taken as an example. The results show that the influence of the electric field is strong for the fracture and the critical buckling strains, detectable for the fracture strength but almost negligible for the critical buckling stress. In addition, the reversed effects are achieved for the fracture and the critical buckling strains. Subsequently, the Timoshenko beam model is utilized to account for the effect of the electric field on the axial buckling of the GaN NWs, where nonlocal effect is observed and characterized by the nonlocal coefficient e{sub 0}a=1.1 nm. The results show that the fracture and buckling of piezoelectric NWs can be controlled by applying an electric field.

  14. Fracture and buckling of piezoelectric nanowires subject to an electric field

    NASA Astrophysics Data System (ADS)

    Zhang, Jin; Wang, Chengyuan; Adhikari, Sondipon

    2013-11-01

    Fracture and buckling are major failure modes of thin and long nanowires (NWs), which could be affected significantly by an electric field when piezoelectricity is involved in the NWs. This paper aims to examine the issue based on the molecular dynamics simulations, where the gallium nitride (GaN) NWs are taken as an example. The results show that the influence of the electric field is strong for the fracture and the critical buckling strains, detectable for the fracture strength but almost negligible for the critical buckling stress. In addition, the reversed effects are achieved for the fracture and the critical buckling strains. Subsequently, the Timoshenko beam model is utilized to account for the effect of the electric field on the axial buckling of the GaN NWs, where nonlocal effect is observed and characterized by the nonlocal coefficient e0a=1.1 nm. The results show that the fracture and buckling of piezoelectric NWs can be controlled by applying an electric field.

  15. Depolarization field effect on dielectric and piezoelectric properties of particulate ferroelectric ceramic-polymer composites

    NASA Astrophysics Data System (ADS)

    Ma, Fengde D.; Wang, Yu U.

    2015-03-01

    The effects of depolarization field on the dielectric and piezoelectric properties of ferroelectric ceramic particle-filled polymer-matrix composites are investigated at the underlying domain level. Phase field modeling and simulation reveals that the macroscopic properties of the composites are dominated by depolarization field effect, which depends on the arrangement and alignment rather than the size or internal grain structure of the ferroelectric particulates. It is found that 0-3 particulate composites with random dispersion of ferroelectric particles behave essentially like linear dielectric rather than ferroelectric materials, and domain-level analysis reveals the physical mechanism for lack of domain switching or hysteresis as attributed to strong depolarization effect. Thus, without effective reduction or elimination of the depolarization field, the composites cannot benefit from the functional fillers regardless of their superior properties. In order to exhibit the desired ferroelectric behaviors, it necessitates continuous ferroelectric phase connectivity in the composites.

  16. Enhancement of the magnetoelectric coupling in an A-line shape magnetostrictive/piezoelectric structure

    NASA Astrophysics Data System (ADS)

    Zhang, Juanjuan; Kang, Yan; Yu, Yang; Gao, Yuanwen

    2017-01-01

    In this study, a new kind of magnetoelectric (ME) structure is designed with Terfenol-D, PZT-5A and nonmagnetic and nonelectric trestle. The configuration of this ME structure presents "A-line" type, PZT-5A and Terfenol-D are respectively bonded with the trestles, which adopt the knuckle joint assembly. Differently from the conventional ME layered structure, in the new structure, the deformation of the PZT-5A of larger size is driven by a Terfenol-D layer of smaller size at an external magnetic field. Since the driven force is applied at the ends of piezoelectric layer through the trestles, the whole piezoelectric layer can be completely stretched or compressed, and the larger voltage should be induced. For the new ME structure with mica trestle, the maximum value of αE is twice higher than that for the conventional laminated ME structure. Furthermore, a wider range of response frequency is also observed in this structure. For the new ME structure with ABS trestle, the experimental results indicate that the maximum ME voltage coefficient is measured as high as 31.85 V/cm Oe at 405 Oe.

  17. High piezoelectric properties of cement piezoelectric composites containing kaolin

    NASA Astrophysics Data System (ADS)

    Pan, Huang Hsing; Yang, Ruei-Hao; Cheng, Yu-Chieh

    2015-04-01

    To obtain high piezoelectric properties, PZT/cement composites with kaolin were fabricated and polarized by 1.5kV/mm electric field for 40 min, where lead zirconate titanate (PZT) inclusion with 50% by volume was used. After the polarization, piezoelectric properties of the composite were measured daily till 100 days. Results indicated that relative dielectric constant (ɛr) and piezoelectric strain constant (d33) increase with aging day, and approach to asymptotic values after 70 days. Temperature treatment to the composite is a dominate factor to enhance piezoelectric properties. The d33 and ɛr values of PZT/cement composites treated at the ambient temperature (23℃) were 57pC/N and 275 at the 70th aging day respectively, and then reached 106pC/N and 455 in turn with 150℃ treatment. The composite contains 4% kaolin having the highest value of d33=111pC/N and ɛr=500 at 90 days because the porosity is the less than the others. Cement piezoelectric composites containing kaolin own the higher d33 and ɛr value, compared with the other reported composites with 50% PZT. The porosity, the electromechanical coupling factor and impedance-frequency spectra of the cement piezoelectric composites were also discussed.

  18. Enhanced dielectric and piezoelectric responses in Zn1-xMgxO thin films near the phase separation boundary

    NASA Astrophysics Data System (ADS)

    Kang, Xiaoyu; Shetty, Smitha; Garten, Lauren; Ihlefeld, Jon F.; Trolier-McKinstry, Susan; Maria, Jon-Paul

    2017-01-01

    Dielectric and piezoelectric properties for Zn1-xMgxO (ZMO) thin films are reported as a function of MgO composition up to and including the phase separation region. Zn1-xMgxO (0.25 ≤ x ≤ 0.5) thin films with c-axis textures were deposited by pulsed laser deposition on platinized sapphire substrates. The films were phase pure wurtzite for MgO concentrations up to 40%; above that limit, a second phase with rocksalt structure evolves with strong {100} texture. With increasing MgO concentration, the out-of-plane (d33,f) and in-plane (e31,f) piezoelectric coefficients increase by 360% and 290%, respectively. The increase in piezoelectric coefficients is accompanied by a 35% increase in relative permittivity. Loss tangent values fall monotonically with increasing MgO concentration, reaching a minimum of 0.001 for x ≥ 0.30, at which point the band gap is reported to be 4 eV. The enhanced piezoelectric response, the large band gap, and the low dielectric loss make Zn1-xMgxO an interesting candidate for thin film piezoelectric devices, and demonstrate that compositional phase transformations provide opportunities for property engineering.

  19. Enhanced dielectric and piezoelectric responses in Zn1-xMgxO thin films near the phase separation boundary

    DOE PAGES

    Kang, Xiaoyu; Shetty, Smitha; Garten, Lauren; ...

    2017-01-23

    Dielectric and piezoelectric properties for Zn1-xMgxO (ZMO) thin films are reported as a function of MgO composition up to and including the phase separation region. Zn1-xMgxO (0.25 ≤ x ≤ 0.5) thin films with c-axis textures were deposited by pulsed laser deposition on platinized sapphire substrates. The films were phase pure wurtzite for MgO concentrations up to 40%; above that limit, a second phase with rocksalt structure evolves with strong {100} texture. With increasing MgO concentration, the out-of-plane (d33,f) and in-plane (e31,f) piezoelectric coefficients increase by 360% and 290%, respectively. The increase in piezoelectric coefficients is accompanied by a 35%more » increase in relative permittivity. Loss tangent values fall monotonically with increasing MgO concentration, reaching a minimum of 0.001 for x ≥ 0.30, at which point the band gap is reported to be 4 eV. As a result, the enhanced piezoelectric response, the large band gap, and the low dielectric loss make Zn1-xMgxO an interesting candidate for thin film piezoelectric devices, and demonstrate that compositional phase transformations provide opportunities for property engineering.« less

  20. Enhanced ferroeletric and piezoelectric properties of Nd3+ doped PZT nanoceramics

    NASA Astrophysics Data System (ADS)

    Kour, Paramjit; Pradhan, Sudipta Kishore; Kumar, Pawan; Sinha, Sanjay Kumar; Kar, Manoranjan

    2016-05-01

    The sol gel technique was used to prepare Pb1-xNdx Zr0.52Ti0.48O3 with x = 0.02, 0.04, 0.06 and 0.10 samples. Room temperature Raman spectra of all the sample were recorded in the range of wave number 30-1000 cm-1. It suggests that the increase in contribution of tetragonal crystallographic phase with the increase in Nd concentration in the sample. FTIR study shows the presence of characteristic bending and streching vibrations of perovskite (ABO3) structure. Ferroelectric and piezoelectric properties were enhanced by the Nd substitution at Pb site of PbZr0.52Ti0.48O3.

  1. Piezoelectrically assisted ultrafiltration

    SciTech Connect

    Ahner, N.; Gottschlich, D.; Narang, S.; Roberts, D.; Sharma, S.; Ventura, S.

    1993-01-01

    The authors have demonstrated the feasibility of using piezoelectrically assisted ultrafiltration to reduce membrane fouling and enhance the flux through ultrafiltration membranes. A preliminary economic evaluation, accounting for the power consumption of the piezoelectric driver and the extent of permeate flow rate enhancement, has also shown that piezoelectrically assisted ultrafiltration is cost effective and economically competitive in comparison with traditional separation processes. Piezoelectric transducers, such as a piezoelectric lead zirconate titanate (PZT) disc or a piezoelectric horn, driven by moderate power, significantly enhance the permeate flux on fouled membranes, presumably because they promote local turbulence. Several experiments were conducted on polysulfone and regenerated cellulose UF membranes fouled during filtration of model feed solutions. Solutions of poly(ethylene glycol) and of high-molecular weight dextran were used as models. The authors found that they could significantly increase the permeate flux by periodically driving the piezoelectric transducer, horn or PZT disc, by application of moderate power over short periods of time, from 20 to 90 seconds. Enhancements as high as a factor of 8 were recorded within a few seconds, and enhanced permeate fluxes were maintained over a prolonged period (up to 3 hours). The prolonged flux enhancement makes it feasible to drive the piezoelectric transducer intermittently, thereby reducing the power consumption of the piezoelectric driver. As piezoelectric drivers of sonically assisted ultrafiltration, PZT disc transducers are preferred over the piezoelectric horn because of their small size and ease of adaptability to ultrafiltration test cells. The horn transmits sonic energy to the UF membrane through a titanium element driven by a separate piezoelectric transducer, but a piezoelectric ceramic disc transmits energy directly to the UF membrane.

  2. Customization of the acoustic field produced by a piezoelectric array through interelement delays

    PubMed Central

    Chitnis, Parag V.; Barbone, Paul E.; Cleveland, Robin O.

    2008-01-01

    A method for producing a prescribed acoustic pressure field from a piezoelectric array was investigated. The array consisted of 170 elements placed on the inner surface of a 15 cm radius spherical cap. Each element was independently driven by using individual pulsers each capable of generating 1.2 kV. Acoustic field customization was achieved by independently controlling the time when each element was excited. The set of time delays necessary to produce a particular acoustic field was determined by using an optimization scheme. The acoustic field at the focal plane was simulated by using the angular spectrum method, and the optimization searched for the time delays that minimized the least squared difference between the magnitudes of the simulated and desired pressure fields. The acoustic field was shaped in two different ways: the −6 dB focal width was increased to different desired widths and the ring-shaped pressure distributions of various prescribed diameters were produced. For both cases, the set of delays resulting from the respective optimization schemes were confirmed to yield the desired pressure distributions by using simulations and measurements. The simulations, however, predicted peak positive pressures roughly half those obtained from the measurements, which was attributed to the exclusion of nonlinearity in the simulations. PMID:18537369

  3. Blast-induced electromagnetic fields in the brain from bone piezoelectricity.

    PubMed

    Lee, Ka Yan Karen; Nyein, Michelle K; Moore, David F; Joannopoulos, J D; Socrate, Simona; Imholt, Timothy; Radovitzky, Raul; Johnson, Steven G

    2011-01-01

    In this paper, we show that bone piezoelectricity-a phenomenon in which bone polarizes electrically in response to an applied mechanical stress and produces a short-range electric field-may be a source of intense blast-induced electric fields in the brain, with magnitudes and timescales comparable to fields with known neurological effects. We compute the induced charge density in the skull from stress data on the skull from a finite-element full-head model simulation of a typical IED-scale blast wave incident on an unhelmeted human head as well as a human head protected by a kevlar helmet, and estimate the resulting electric fields in the brain in both cases to be on the order of 10 V/m in millisecond pulses. These fields are more than 10 times stronger than the IEEE safety guidelines for controlled environments (IEEE Standards Coordinating Committee 28, 2002) and comparable in strength and timescale to fields from repetitive Transcranial Magnetic Stimulation (rTMS) that are designed to induce neurological effects (Wagner et al., 2006a). They can be easily measured by RF antennas, and may provide the means to design a diagnostic tool that records a quantitative measure of the head's exposure to blast insult.

  4. Lead-Free Piezoceramics: Revealing the Role of the Rhombohedral-Tetragonal Phase Coexistence in Enhancement of the Piezoelectric Properties.

    PubMed

    Rubio-Marcos, Fernando; López-Juárez, Rigoberto; Rojas-Hernandez, Rocio E; del Campo, Adolfo; Razo-Pérez, Neftalí; Fernandez, Jose F

    2015-10-21

    Until now, lead zirconate titanate (PZT) based ceramics are the most widely used in piezoelectric devices. However, the use of lead is being avoided due to its toxicity and environmental risks. Indeed, the attention in piezoelectric devices has been moved to lead-free ceramics, especially on (K,Na)NbO3-based materials, due to growing environmental concerns. Here we report a systematic evaluation of the effects of the compositional modifications induced by replacement of the B-sites with Sb(5+) ions in 0.96[(K0.48Na0.52)0.95Li0.05Nb1-xSbxO3]-0.04[BaZrO3] lead-free piezoceramics. We show that this compositional design is the driving force for the development of the high piezoelectric properties. So, we find that this phenomenon can be explained by the stabilization of a Rhombohedral-Tetragonal (R-T) phase boundary close to room temperature, that facilities the polarization process of the system and exhibits a significantly high piezoelectric response with a d33 value as high as ∼400 pC/N, which is comparable to part soft PZTs. As a result, we believe that the general strategy and design principles described in this study open the possibility of obtaining (K,Na)NbO3-based lead-free ceramics with enhanced properties, expanding their application range.

  5. Effect of piezoelectric field of threading dislocations on electron transport and capture in nitride semiconductors

    NASA Astrophysics Data System (ADS)

    Romanov, Dmitri; Auner, Gregory

    2001-03-01

    In nitride semiconductor structures, stress is known to induce considerable electric fields due to piezoelectric effect. We consider an AlN layer grown on a sapphire substrate and containing a number of threading dislocations. Most them are edge dislocations running in the growth direction. The strain field of such a dislocation results in electric field aligned with the dislocation axis and having alternate directions in the areas of compression and tension. These electric fields make for anisotropic electron diffusion in the layer. They also change the rates of electron capture by impurities, depending on the distance to the dislocation core. We apply these results to photoexcited electrons in a GaN/AlN quantum dot system where the dot nucleation occurred preferably in the tension regions near the dislocations [1]. The biased diffusion leads to photoinduced polarization of the dot-containing layer even in the absence of external electric field. [1] J.L. Rouviere, J. Simon, N. Pelekanos, B. Daudin, and G. Feuillet, Appl. Phys. Lett., 75, 2632-2634 (1999)

  6. Enhanced active piezoelectric 0-3 nanocomposites fabricated through electrospun nanowires

    SciTech Connect

    Feenstra, Joel; Sodano, Henry A.

    2008-06-15

    The use of monolithic piezoceramic materials in sensing and actuation applications has become quite common over the past decade. However, these materials have several properties that limit their application in practical systems. These materials are very brittle due to the ceramic nature of the monolithic material, making them vulnerable to accidental breakage during handling and bonding procedures. In addition, they have very poor ability to conform to curved surfaces and result in large add-on mass associated with using a typically lead-based ceramic. These limitations have motivated the development of alternative methods of applying the piezoceramic material, including piezoceramic fiber composites and piezoelectric 0-3 composites (also known as piezoelectric paint). Piezoelectric paint is desirable because it can be spayed or painted on and can be used with abnormal surfaces. However, the piezoelectric paint developed in prior studies has resulted in low coupling, limiting its application. In order to increase the coupling of the piezoelectric paint, this effort has investigated the use of piezoelectric nanowires rather than spherical piezoelectric particle, which are difficult to strain when embedded in a polymer matrix. The piezoceramic wires were electrospun from a barium titanate (BaTiO{sub 3}) sol gel to produce fibers with 500-1000 nm diameters and subsequently calcinated to acquire perovskite BaTiO{sub 3}. An active nanocomposite paint was formed using the resulting piezoelectric wires and was compared to the same paint with piezoelectric nanoparticles. The results show that the piezoceramic wires produce 0-3 nanocomposites with as high as 300% increase in electromechanical coupling.

  7. Enhancement of piezoelectric constants induced by cation-substitution and two-dimensional strain effects on ZnO predicted by density functional perturbation theory

    NASA Astrophysics Data System (ADS)

    Nakamura, Kaoru; Higuchi, Sadao; Ohnuma, Toshiharu

    2016-03-01

    Using density functional perturbation theory, we investigated the effect of various substitutional dopant elements and in-plane strain on the piezoelectric properties of ZnO. The piezoelectric stress constant e33 of doped ZnO was found to depend on the formal charge of the substitutional dopant. By decomposing the piezoelectric stress constant e33 into the individual atomic contributions, the change in the piezoelectric properties was found to originate from a change in the coupling between the atomic displacement and the strain. Furthermore, we found that in-plane tensile strain along the a axis, which is specific to the thin film, can enhance the piezoelectric constant of ZnO. A phase transition from wurtzite to h-BN-type structure was found to occur with increasing in-plane tensile. The piezoelectric strain constant d33 was predicted to reach ˜200 pC/N for 2.78 at. % V-substituted ZnO at 5.5% in-plane strain, just before the phase transition. These theoretical results suggest that the piezoelectric constant of ZnO can be enhanced by controlling the in-plane strain via selection of the substrate material and dopant element.

  8. The field induced e{sub 31,f} piezoelectric and Rayleigh response in barium strontium titanate thin films

    SciTech Connect

    Garten, L. M. Trolier-McKinstry, S.

    2014-09-29

    The electric field induced e{sub 31,f} piezoelectric response and tunability of Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} (70:30) and Ba{sub 0.6}Sr{sub 0.4}TiO{sub 3} (60:40) thin films on MgO and silicon was measured. The relative dielectric tunabilities for the 70:30 and 60:40 compositions on MgO were 83% and 70%, respectively, with a dielectric loss of less than 0.011 and 0.004 at 100 kHz. A linear increase in induced piezoelectricity to −3.0 C/m{sup 2} and −1.5 C/m{sup 2} at 110 kV/cm was observed in Ba{sub 0.6}Sr{sub 0.4}TiO{sub 3} on MgO and Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} on Si. Hysteresis in the piezoelectric and dielectric response of the 70:30 composition films was consistent with the positive irreversible dielectric Rayleigh coefficient. Both indicate a ferroelectric contribution to the piezoelectric and dielectric response over 40–80 °C above the global paraelectric transition temperature.

  9. The magnetoresonance operation of microwiggler on the piezoelectrics with a strong magnetic guide field

    SciTech Connect

    Choi, J.S.; So, C.H.; Moon, J.D.

    1995-12-31

    We proposed that a new type of the electrostatic microwiggler with a wiggler period (0.1 mm {le}1{sub w}{le}1 mm) and the wiggler field strength (E{sub w}{le} 100 kV/m) can be produced on the surface of a PZT when a high power and high frequency ultrasonic wave travels through a PZT bar. Numerical simulations in the linear and nonlinear gain regime show that a weak microwiggler (E{sub w}100 kV/m,{lambda}{sub w}{approx}100 periods), operating in magnetoresonance with a strong guide field (B{sub o}{approx} 3.6T), can generate a millimeter and submillimeter radiations with medium electronic efficiency of few percents. It is shown that the maximum output power of the compact FEL using the wiggler system generated on the surface of the piezoelectric material may be upto a few Watts with a relatively low energy and low current electron beam (Ew {approx}100 keV and I{sub b}1 mA).

  10. Enhanced piezoelectric response of the two-tetragonal-phase-coexisted BiFeO3 epitaxial film

    NASA Astrophysics Data System (ADS)

    Zhao, Yajuan; Yin, Zhigang; Fu, Zhen; Zhang, Xingwang; Zhu, Jingbin; Wu, Jinliang; You, Jingbi

    2017-02-01

    A BiFeO3 epitaxial film composed of two tetragonal phases was deposited on SrTiO3 substrates by using oxygen-deficient La0.3Sr0.7MnO3-δ as the buffer. One of these phases is a high-temperature form of the highly elongated monoclinic type-C BiFeO3, and the other belongs to the strain-distorted version of the rhombohedral phase. The piezoelectric constant d33 of the mixed-phase structure was determined to be 210 pm/V, much larger than that of the pure rhombohedral BiFeO3. Electric-field-induced strain up to 4% was observed, suggesting a strong electromechanical coupling of the film. These results enrich the knowledge on the strain-driven morphotropic phase boundary of BiFeO3, and thereby provide a possible way for future lead-free piezoelectric applications.

  11. Study of field-induced chain conformation transformation in poly(L-lactic acid) based piezoelectric film by infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Du, Xinyu; Zhao, Chunlin; Zhang, Jinxi; Ren, Kailiang

    2016-10-01

    In this investigation, the chain conformation transformation of the piezoelectric polymer of a poly(L-Lactic Acid) (PLLA) film was analyzed under an electric field for the first time using infrared spectroscopy. It is revealed that the piezoelectric shear mode coefficient d14 (˜10 pC/N) of a stretched α form PLLA film mainly comes from the rotation of C  O dipoles inside the polymer main chain. The reorientation of the dipoles causes the deformation of the crystal structure, which corresponds to a shear mode strain macroscopically in the PLLA film along a 45° direction to the polymer length. The back-bone of the molecular chain keeps its own conformation of a 103 helix under an external field up to 100 MV/m.

  12. Symmetry Breaking and Fine Structure Splitting in Zincblende Quantum Dots: Atomistic Simulations of Long-Range Strain and Piezoelectric Field

    NASA Astrophysics Data System (ADS)

    Ahmed, Shaikh; Usman, Muhammad; Heitzinger, Clemens; Rahman, Rajib; Schliwa, Andrei; Klimeck, Gerhard

    2007-04-01

    Electrons and holes captured in self-assembled quantum dots (QDs) are subject to symmetry breaking that cannot be represented in with continuum material representations. Atomistic calculations reveal symmetry lowering due to effects of strain and piezo-electric fields. These effects are fundamentally based on the crystal topology in the quantum dots. This work studies these two competing effects and demonstrates the fine structure splitting that has been demonstrated experimentally can be attributed to the underlying atomistic structure of the quantum dots.

  13. Enhanced piezoelectric and mechanical properties of AlN-modified BaTiO3 composite ceramics.

    PubMed

    Xu, Dan; Wang, Lidong; Li, Weili; Wang, Wei; Hou, Yafei; Cao, Wenping; Feng, Yu; Fei, Weidong

    2014-07-14

    BaTiO3-xAlN (BT-xAlN) composite ceramics were prepared by conventional solid state reaction sintering. The effects of the AlN content on the crystalline structures, densities, and electrical and mechanical properties of the BT ceramics were investigated. The BT-1.5%AlN ceramic exhibits a good piezoelectric constant of 305 pC N(-1) and an improved Vickers hardness of 5.9 GPa. The enhanced piezoelectricity originates from interactions between defect dipoles and spontaneous polarization inside the domains due to the occurrence of local symmetry, caused by the preferential distribution of the Al(3+)-N(3-) pairs vertical to the c axis. The hardening of the material is attributed to the improved density, and particle and grain boundary strengthening. Our work indicates that if a suitable doping ion pair is designed, lead-free ceramic systems prepared from ordinary raw materials by a conventional sintering method have a high probability of exhibiting good piezoelectric and mechanical properties simultaneously.

  14. Enhanced piezoelectricity and modified dielectric screening of two-dimensional group-IV monochalcogenides

    NASA Astrophysics Data System (ADS)

    Gomes, Lídia C.; Carvalho, A.; Castro Neto, A. H.

    2015-12-01

    We use first-principles calculations to investigate the lattice properties of group-IV monochalcogenides. These include static dielectric permittivity, elastic and piezoelectric tensors. For the monolayer, it is found that the static permittivity, besides acquiring a dependence on the interlayer distance, is comparatively higher than in the 3D system. In contrast, it is found that elastic properties are little changed by the lower dimensionality. Poisson ratios relating in-plane deformations are close to zero, and the existence of a negative Poisson ratio is also predicted for the GeS compound. Finally, the monolayer shows piezoelectricity, with piezoelectric constants higher than those recently predicted to occur in other 2D systems, such as hexagonal BN and transition-metal dichalcogenide monolayers.

  15. Strongly Enhanced Piezoelectric Response in Lead Zirconate Titanate Films with Vertically Aligned Columnar Grains.

    PubMed

    Nguyen, Minh D; Houwman, Evert P; Dekkers, Matthijn; Rijnders, Guus

    2017-03-08

    Pb(Zr0.52Ti0.48)O3 (PZT) films with (001) orientation were deposited on Pt(111)/Ti/SiO2/Si(100) substrates using pulsed laser deposition. Variation of the laser pulse rate during the deposition of the PZT films was found to play a key role in the control of the microstructure and to change strongly the piezoelectric response of the thin film. The film deposited at low pulse rate has a denser columnar microstructure, which improves the transverse piezoelectric coefficient (d31f) and ferroelectric remanent polarization (Pr), whereas the less densely packed columnar grains in the film deposited at high pulse rates give rise to a significantly higher longitudinal piezoelectric coefficient (d33f) value. The effect of film thickness on the ferroelectric and piezoelectric properties of the PZT films was also investigated. With increasing film thickness, the grain column diameter gradually increases, and also the average Pr and d33f values become larger. The largest piezoelectric coefficient of d33f = 408 pm V(-1) was found for a 4-μm film thickness. From a series of films in the thickness range 0.5-5 μm, the z-position dependence of the piezoelectric coefficient could be deduced. A local maximum value of 600 pm V(-1) was deduced in the 3.5-4.5 μm section of the thickest films. The dependence of the film properties on film thickness is attributed to the decreasing effect of the clamping constraint imposed by the substrate and the increasing spatial separation between the grains with increasing film thickness.

  16. Strongly Enhanced Piezoelectric Response in Lead Zirconate Titanate Films with Vertically Aligned Columnar Grains

    PubMed Central

    2017-01-01

    Pb(Zr0.52Ti0.48)O3 (PZT) films with (001) orientation were deposited on Pt(111)/Ti/SiO2/Si(100) substrates using pulsed laser deposition. Variation of the laser pulse rate during the deposition of the PZT films was found to play a key role in the control of the microstructure and to change strongly the piezoelectric response of the thin film. The film deposited at low pulse rate has a denser columnar microstructure, which improves the transverse piezoelectric coefficient (d31f) and ferroelectric remanent polarization (Pr), whereas the less densely packed columnar grains in the film deposited at high pulse rates give rise to a significantly higher longitudinal piezoelectric coefficient (d33f) value. The effect of film thickness on the ferroelectric and piezoelectric properties of the PZT films was also investigated. With increasing film thickness, the grain column diameter gradually increases, and also the average Pr and d33f values become larger. The largest piezoelectric coefficient of d33f = 408 pm V–1 was found for a 4-μm film thickness. From a series of films in the thickness range 0.5–5 μm, the z-position dependence of the piezoelectric coefficient could be deduced. A local maximum value of 600 pm V–1 was deduced in the 3.5–4.5 μm section of the thickest films. The dependence of the film properties on film thickness is attributed to the decreasing effect of the clamping constraint imposed by the substrate and the increasing spatial separation between the grains with increasing film thickness. PMID:28247756

  17. Characterization of Piezoelectric Actuators for Flow Control Over a Wing

    NASA Technical Reports Server (NTRS)

    Mossi, Karla M.; Bryant, Robert G.

    2004-01-01

    During the past decade, piezoelectric actuators as the active element in synthetic jets demonstrated that they could significantly enhance the overall lift on an airfoil. However, durability, system weight, size, and power have limited their use outside a laboratory. These problems are not trivial, since piezoelectric actuators are physically brittle and display limited displacement. The objective of this study is to characterize the relevant properties for the design of a synthetic jet utilizing three types of piezoelectric actuators as mechanical diaphragms, Radial Field Diaphragms, Thunders, and Bimorphs so that the shape cavity volume does not exceed 147.5 cubic centimeters on a 7centimeter x 7centimeter aerial coverage. These piezoelectric elements were selected because of their geometry, and overall free-displacement. Each actuator was affixed about its perimeter in a cavity, and relevant parameters such as clamped displacement variations with voltage and frequency, air velocities produced through an aperture, and sound pressure levels produced by the piezoelectric diaphragms were measured.

  18. (100)-Textured KNN-based thick film with enhanced piezoelectric property for intravascular ultrasound imaging

    PubMed Central

    Zhu, Benpeng; Zhang, Zhiqiang; Ma, Teng; Yang, Xiaofei; Li, Yongxiang; Shung, K. Kirk; Zhou, Qifa

    2015-01-01

    Using tape-casting technology, 35 μm free-standing (100)-textured Li doped KNN (KNLN) thick film was prepared by employing NaNbO3 (NN) as template. It exhibited similar piezoelectric behavior to lead containing materials: a longitudinal piezoelectric coefficient (d33) of ∼150 pm/V and an electromechanical coupling coefficient (kt) of 0.44. Based on this thick film, a 52 MHz side-looking miniature transducer with a bandwidth of 61.5% at −6 dB was built for Intravascular ultrasound (IVUS) imaging. In comparison with 40 MHz PMN-PT single crystal transducer, the rabbit aorta image had better resolution and higher noise-to-signal ratio, indicating that lead-free (100)-textured KNLN thick film may be suitable for IVUS (>50 MHz) imaging. PMID:25991874

  19. (100)-Textured KNN-based thick film with enhanced piezoelectric property for intravascular ultrasound imaging

    NASA Astrophysics Data System (ADS)

    Zhu, Benpeng; Zhang, Zhiqiang; Ma, Teng; Yang, Xiaofei; Li, Yongxiang; Shung, K. Kirk; Zhou, Qifa

    2015-04-01

    Using tape-casting technology, 35 μm free-standing (100)-textured Li doped KNN (KNLN) thick film was prepared by employing NaNbO3 (NN) as template. It exhibited similar piezoelectric behavior to lead containing materials: a longitudinal piezoelectric coefficient (d33) of ˜150 pm/V and an electromechanical coupling coefficient (kt) of 0.44. Based on this thick film, a 52 MHz side-looking miniature transducer with a bandwidth of 61.5% at -6 dB was built for Intravascular ultrasound (IVUS) imaging. In comparison with 40 MHz PMN-PT single crystal transducer, the rabbit aorta image had better resolution and higher noise-to-signal ratio, indicating that lead-free (100)-textured KNLN thick film may be suitable for IVUS (>50 MHz) imaging.

  20. Effect of piezoelectric fields of ultrasonic vibrations on raman scattering in GaAs/AlGaAs heterostructures

    SciTech Connect

    Kurylyuk, V. V. Korotchenkov, O. A.

    2009-04-15

    The resonance electroacoustic vibrations in the GaAs/AlGaAs-LiNbO{sub 3} hybrid structure with the slippery interface and the effect of redistribution of the two-dimensional electron gas density in the heterostructure by the induced piezoelectric fields are analyzed theoretically. The calculations are performed by the finite element method. The experimentally recorded time-resolved Raman spectra exhibit some specific features of the behavior of the LO-phonon-plasmon mode. The features are consistent with the theoretically calculated redistribution of the density of the electron gas.

  1. Piezoelectric Polymers

    NASA Technical Reports Server (NTRS)

    Harrison, J. S.; Ounaies, Z.; Bushnell, Dennis M. (Technical Monitor)

    2001-01-01

    The purpose of this review is to detail the current theoretical understanding of the origin of piezoelectric and ferroelectric phenomena in polymers; to present the state-of-the-art in piezoelectric polymers and emerging material systems that exhibit promising properties; and to discuss key characterization methods, fundamental modeling approaches, and applications of piezoelectric polymers. Piezoelectric polymers have been known to exist for more than forty years, but in recent years they have gained notoriety as a valuable class of smart materials.

  2. Measurement of the internal stress and electric field in a resonating piezoelectric transformer for high-voltage applications using the electro-optic and photoelastic effects

    SciTech Connect

    VanGordon, James A.; Kovaleski, Scott D. Norgard, Peter; Gall, Brady B.; Dale, Gregory E.

    2014-02-15

    The high output voltages from piezoelectric transformers are currently being used to accelerate charged particle beams for x-ray and neutron production. Traditional methods of characterizing piezoelectric transformers (PTs) using electrical probes can decrease the voltage transformation ratio of the device due to the introduction of load impedances on the order of hundreds of kiloohms to hundreds of megaohms. Consequently, an optical diagnostic was developed that used the photoelastic and electro-optic effects present in piezoelectric materials that are transparent to a given optical wavelength to determine the internal stress and electric field. The combined effects of the piezoelectric, photoelastic, and electro-optic effects result in a time-dependent change the refractive indices of the material and produce an artificially induced, time-dependent birefringence in the piezoelectric material. This induced time-dependent birefringence results in a change in the relative phase difference between the ordinary and extraordinary wave components of a helium-neon laser beam. The change in phase difference between the wave components was measured using a set of linear polarizers. The measured change in phase difference was used to calculate the stress and electric field based on the nonlinear optical properties, the piezoelectric constitutive equations, and the boundary conditions of the PT. Maximum stresses of approximately 10 MPa and electric fields of as high as 6 kV/cm were measured with the optical diagnostic. Measured results were compared to results from both a simple one-dimensional (1D) model of the piezoelectric transformer and a three-dimensional (3D) finite element model. Measured stresses and electric fields along the length of an operating length-extensional PT for two different electrical loads were within at least 50 % of 3D finite element simulated results. Additionally, the 3D finite element results were more accurate than the results from the 1D model

  3. Measurement of the internal stress and electric field in a resonating piezoelectric transformer for high-voltage applications using the electro-optic and photoelastic effects.

    PubMed

    VanGordon, James A; Kovaleski, Scott D; Norgard, Peter; Gall, Brady B; Dale, Gregory E

    2014-02-01

    The high output voltages from piezoelectric transformers are currently being used to accelerate charged particle beams for x-ray and neutron production. Traditional methods of characterizing piezoelectric transformers (PTs) using electrical probes can decrease the voltage transformation ratio of the device due to the introduction of load impedances on the order of hundreds of kiloohms to hundreds of megaohms. Consequently, an optical diagnostic was developed that used the photoelastic and electro-optic effects present in piezoelectric materials that are transparent to a given optical wavelength to determine the internal stress and electric field. The combined effects of the piezoelectric, photoelastic, and electro-optic effects result in a time-dependent change the refractive indices of the material and produce an artificially induced, time-dependent birefringence in the piezoelectric material. This induced time-dependent birefringence results in a change in the relative phase difference between the ordinary and extraordinary wave components of a helium-neon laser beam. The change in phase difference between the wave components was measured using a set of linear polarizers. The measured change in phase difference was used to calculate the stress and electric field based on the nonlinear optical properties, the piezoelectric constitutive equations, and the boundary conditions of the PT. Maximum stresses of approximately 10 MPa and electric fields of as high as 6 kV/cm were measured with the optical diagnostic. Measured results were compared to results from both a simple one-dimensional (1D) model of the piezoelectric transformer and a three-dimensional (3D) finite element model. Measured stresses and electric fields along the length of an operating length-extensional PT for two different electrical loads were within at least 50 % of 3D finite element simulated results. Additionally, the 3D finite element results were more accurate than the results from the 1D model

  4. A self-powered vibration sensor based on electrospun poly(vinylidene fluoride) nanofibres with enhanced piezoelectric response

    NASA Astrophysics Data System (ADS)

    Pan, Xumin; Wang, Zhao; Cao, Zilan; Zhang, Shenqiu; He, Yahua; Zhang, Youdong; Chen, Kansong; Hu, Yongming; Gu, Haoshuang

    2016-10-01

    The development of self-powered vibration sensors using polymeric piezoelectric nanomaterials has attracted great attention owing to their outstanding flexibility and energy harvesting behaviours. In this study, ultra-long poly (vinylidene fluoride) (PVDF) nanofibres with optimised β-phase content were synthesised through electrospinning method with different DC voltages. The increase in the β-phase content of the PVDF nanofibres greatly enhanced their piezoelectric response with nearly tripled output voltage and current under the same strain condition. Moreover, the output voltage exhibited linear correlations with both the amplitude and frequency of the strain. Under a fixed frequency of 1.54 Hz, the output voltage exhibited a linear correlation to the strain amplitude with strain sensitivity up to 0.92 V rad-1 and 0.61 V mm-1. The frequency-dependent strain sensing behaviour also confirmed the necessity for frequency calibration to the measured results of vibration. Accordingly, the sensor can be used for self-powered monitoring of the vibration state of a metal foil and measuring the intrinsic resonance frequency of the objects without any powering source.

  5. Piezoelectric valve

    SciTech Connect

    Petrenko, Serhiy Fedorovich

    2013-01-15

    A motorized valve has a housing having an inlet and an outlet to be connected to a pipeline, a saddle connected with the housing, a turn plug having a rod, the turn plug cooperating with the saddle, and a drive for turning the valve body and formed as a piezoelectric drive, the piezoelectric drive including a piezoelectric generator of radially directed standing acoustic waves, which is connected with the housing and is connectable with a pulse current source, and a rotor operatively connected with the piezoelectric generator and kinematically connected with the rod of the turn plug so as to turn the turn plug when the rotor is actuated by the piezoelectric generator.

  6. Piezoelectric cantilever sensors

    NASA Technical Reports Server (NTRS)

    Shih, Wan Y. (Inventor); Shih, Wei-Heng (Inventor); Shen, Zuyan (Inventor)

    2008-01-01

    A piezoelectric cantilever with a non-piezoelectric, or piezoelectric tip useful as mass and viscosity sensors. The change in the cantilever mass can be accurately quantified by monitoring a resonance frequency shift of the cantilever. For bio-detection, antibodies or other specific receptors of target antigens may be immobilized on the cantilever surface, preferably on the non-piezoelectric tip. For chemical detection, high surface-area selective absorbent materials are coated on the cantilever tip. Binding of the target antigens or analytes to the cantilever surface increases the cantilever mass. Detection of target antigens or analytes is achieved by monitoring the cantilever's resonance frequency and determining the resonance frequency shift that is due to the mass of the adsorbed target antigens on the cantilever surface. The use of a piezoelectric unimorph cantilever allows both electrical actuation and electrical sensing. Incorporating a non-piezoelectric tip (14) enhances the sensitivity of the sensor. In addition, the piezoelectric cantilever can withstand damping in highly viscous liquids and can be used as a viscosity sensor in wide viscosity range.

  7. Enhanced optical, dielectric and piezoelectric behavior in dye doped zinc tris-thiourea sulphate (ZTS) single crystals

    NASA Astrophysics Data System (ADS)

    Bhandari, Sonia; Sinha, Nidhi; Ray, Geeta; Kumar, Binay

    2014-01-01

    Pure and 0.1 mol% amaranth dye doped zinc tris-thiourea sulphate (ZTS) crystals were grown by slow evaporation technique. Orthorhombic structures with changed morphology were observed. Various functional groups present were identified by FTIR and Raman analysis. UV-Vis spectra shows wide transmittance and increased optical band gap from 4.54 to 4.59 eV, with lower extinction coefficient in doped case. In photoluminescence measurement, an intense peak at 416 nm was observed for doped ZTS. Dielectric constant value increases from 3.28 to 9.40 at 1 kHz with doping. Piezoelectric coefficient d33 is also enhanced from 0.24 to 3 pC/N.

  8. Hybrid Energy Harvester Consisting of Piezoelectric Fibers with Largely Enhanced 20 V for Wearable and Muscle-Driven Applications.

    PubMed

    Fuh, Yiin-Kuen; Ye, Jia-Cheng; Chen, Po-Chou; Ho, Hsi-Chun; Huang, Zih-Ming

    2015-08-12

    We present a polyvinylidene fluoride (PVDF) nanogenerator (NG) with advantages of direct writing and in situ poling via near-field electrospinning (NFES), which is completely location addressable and substrate independent. The maximum output voltage reached 20 V from the three layers piled NGs with serial connections, and the maximum output current can exceed 390 nA with the parallel integration setup. Linear superposition and switching polarity of current and voltage tests were validated by the authentic piezoelectric output. Nanofiber (NF)-based devices with a length ∼5 cm can be easily attached on the human finger under folding-releasing at ∼45°, and the output voltage and current can reach 0.8 V and 30 nA, respectively. This work based on NFs can potentially have a huge impact on harvesting various external sources from mechanical energies.

  9. Expression of picogram sensitive bending modes in piezoelectric cantilever sensors with nonuniform electric fields generated by asymmetric electrodes

    NASA Astrophysics Data System (ADS)

    Johnson, Blake N.; Mutharasan, Raj

    2010-12-01

    Single-layer uniform cross-sectioned piezoelectric macro-cantilevers fabricated with an asymmetric electrode configuration enabled electrical measurement of picogram-sensitive resonant bending modes in liquids. Bending modes were otherwise not electrically measurable without excitation by a nonuniform electric field created by the geometric asymmetry in electrode design used. Electrode modification was confirmed by energy-dispersive X-ray spectroscopy (EDS). Mass-change sensitivity was tested using both bulk density changes and surface chemisorption experiments in a continuous flow apparatus. Significant response to density changes as small as 0.004 g/mL was measured. A sensitivity limit of ˜1 picogram in liquid was determined from 1-dodecanethiol chemisorption experiments. The sensitivity decreased with chemisorbed mass and was log-linear over five orders of magnitude. The observed resonance responses were in agreement with previously reported models of resonating cantilever sensors. This work demonstrates experimentally for the first time that introducing electrode asymmetry enables measurement of bending modes in cantilevers containing only a single piezoelectric layer.

  10. Progress in engineering high strain lead-free piezoelectric ceramics

    PubMed Central

    Leontsev, Serhiy O; Eitel, Richard E

    2010-01-01

    Environmental concerns are strongly driving the need to replace the lead-based piezoelectric materials currently employed as multilayer actuators. The current review describes both compositional and structural engineering approaches to achieve enhanced piezoelectric properties in lead-free materials. The review of the compositional engineering approach focuses on compositional tuning of the properties and phase behavior in three promising families of lead-free perovskite ferroelectrics: the titanate, alkaline niobate and bismuth perovskites and their solid solutions. The ‘structural engineering’ approaches focus instead on optimization of microstructural features including grain size, grain orientation or texture, ferroelectric domain size and electrical bias field as potential paths to induce large piezoelectric properties in lead-free piezoceramics. It is suggested that a combination of both compositional and novel structural engineering approaches will be required in order to realize viable lead-free alternatives to current lead-based materials for piezoelectric actuator applications. PMID:27877343

  11. Active Piezoelectric Diaphragms

    NASA Technical Reports Server (NTRS)

    Bryant, Robert G.; Effinger, Robert T., IV; Aranda, Isaiah, Jr.; Copeland, Ben M.; Covington, Ed W., III

    2002-01-01

    Several active piezoelectric diaphragms were fabricated by placing unelectroded piezoelectric disks between copper clad films patterned with Inter-Circulating Electrodes "ICE". When a voltage potential is applied to the electrodes, the result is radially distributed electric field that mechanically strains the piezo-ceramic along the Z-axis (perpendicular to the applied electric field), rather than the expected in-plane (XY-axis) direction. Unlike other out of plane piezoelectric actuators, which are benders, these Radial Field Diaphragms (RFDs) strain concentrically yet afford high displacements while maintaining a constant circumference. This paper covers the fabrication and characterization of these diaphragms as a function of poling field strength, ceramic diameter and line spacing, as well as the surface topography, the resulting strain field and displacement as a function of applied voltage ranging from DC to 10 Hz.

  12. Experimental study of the flow field induced by a resonating piezoelectric flapping wing

    NASA Astrophysics Data System (ADS)

    Bidakhvidi, M. Ahmadi; Shirzadeh, R.; Steenackers, G.; Vanlanduit, S.

    2013-11-01

    Flexible plate structures with integrated piezoelectric patches offer interesting possibilities when considered as actuation mechanisms for energy harvesting devices, cooling devices and propulsion devices of micro-aerial vehicles. Most of the studies reported in literature are based on the assumption of a 2D aerodynamic flow. However, the flow behind a finite span wing is significantly more complex than that of an infinite span wing. In order to corroborate this statement, the present experimental study contains high-speed particle image velocimetry measurements performed on a piezoelectric finite span wing oscillating in air, at 84.8 Hz. The paper focuses on the situation of low Keulegan-Carpenter numbers (KC < 3). The dimensionless KC number describes the relative importance of the drag forces over inertia forces for objects that oscillate in a fluid flow at rest. The evolution of the unsteady vortex structures near the plate is characterized for different conditions. This allows a better understanding of the unsteady aerodynamics of flapping flight. The accomplished experimental data analysis has shown that the flow phenomena are strongly dependent on the KC values.

  13. Band structure engineering via piezoelectric fields in strained anisotropic CdSe/CdS nanocrystals

    PubMed Central

    Christodoulou, Sotirios; Rajadell, Fernando; Casu, Alberto; Vaccaro, Gianfranco; Grim, Joel Q.; Genovese, Alessandro; Manna, Liberato; Climente, Juan I.; Meinardi, Francesco; Rainò, Gabriele; Stöferle, Thilo; Mahrt, Rainer F.; Planelles, Josep; Brovelli, Sergio; Moreels, Iwan

    2015-01-01

    Strain in colloidal heteronanocrystals with non-centrosymmetric lattices presents a unique opportunity for controlling optoelectronic properties and adds a new degree of freedom to existing wavefunction engineering and doping paradigms. We synthesized wurtzite CdSe nanorods embedded in a thick CdS shell, hereby exploiting the large lattice mismatch between the two domains to generate a compressive strain of the CdSe core and a strong piezoelectric potential along its c-axis. Efficient charge separation results in an indirect ground-state transition with a lifetime of several microseconds, almost one order of magnitude longer than any other CdSe/CdS nanocrystal. Higher excited states recombine radiatively in the nanosecond time range, due to increasingly overlapping excited-state orbitals. k̇p calculations confirm the importance of the anisotropic shape and crystal structure in the buildup of the piezoelectric potential. Strain engineering thus presents an efficient approach to highly tunable single- and multiexciton interactions, driven by a dedicated core/shell nanocrystal design. PMID:26219691

  14. Development of a Hybrid Piezo Natural Rubber Piezoelectricity and Piezoresistivity Sensor with Magnetic Clusters Made by Electric and Magnetic Field Assistance and Filling with Magnetic Compound Fluid.

    PubMed

    Shimada, Kunio; Saga, Norihiko

    2017-02-10

    Piezoelements used in robotics require large elasticity and extensibility to be installed in an artificial robot skin. However, the piezoelements used until recently are vulnerable to large forces because of the thin solid materials employed. To resolve this issue, we utilized a natural rubber and applied our proposed new method of aiding with magnetic and electric fields as well as filling with magnetic compound fluid (MCF) and doping. We have verified the piezoproperties of the resulting MCF rubber. The effect of the created magnetic clusters is featured in a new two types of multilayered structures of the piezoelement. By measuring the piezoelectricity response to pressure, the synergetic effects of the magnetic clusters, the doping and the electric polymerization on the piezoelectric effect were clarified. In addition, by examining the relation between the piezoelectricity and the piezoresistivity created in the MCF piezo element, we propose a hybrid piezoelement.

  15. Development of a Hybrid Piezo Natural Rubber Piezoelectricity and Piezoresistivity Sensor with Magnetic Clusters Made by Electric and Magnetic Field Assistance and Filling with Magnetic Compound Fluid

    PubMed Central

    Shimada, Kunio; Saga, Norihiko

    2017-01-01

    Piezoelements used in robotics require large elasticity and extensibility to be installed in an artificial robot skin. However, the piezoelements used until recently are vulnerable to large forces because of the thin solid materials employed. To resolve this issue, we utilized a natural rubber and applied our proposed new method of aiding with magnetic and electric fields as well as filling with magnetic compound fluid (MCF) and doping. We have verified the piezoproperties of the resulting MCF rubber. The effect of the created magnetic clusters is featured in a new two types of multilayered structures of the piezoelement. By measuring the piezoelectricity response to pressure, the synergetic effects of the magnetic clusters, the doping and the electric polymerization on the piezoelectric effect were clarified. In addition, by examining the relation between the piezoelectricity and the piezoresistivity created in the MCF piezo element, we propose a hybrid piezoelement. PMID:28208625

  16. Label-free flow-enhanced specific detection of Bacillus anthracis using a piezoelectric microcantilever sensor†

    PubMed Central

    McGovern, John-Paul; Rest, Richard; Purohit, Mitali; Pandya, Yognandan; Shih, Wei-Heng

    2009-01-01

    Differentiation between species of similar biological structure is of critical importance in biosensing applications. Here, we report specific detection of Bacillus anthracis (BA) spores from that of close relatives, such as B. thuringiensis (BT), B. cereus (BC), and B. subtilis (BS) by varying the flow speed of the sampling liquid over the surface of a piezoelectric microcantilever sensor (PEMS). Spore binding to the anti-BA spore IgG coated PEMS surface is determined by monitoring the resonance frequency change in the sensor’s impedance vs. frequency spectrum. Flow increases the resonance frequency shift at lower flow rates until the impingement force from the flow overcomes the binding strength of the antigen and decreases the resonance frequency shift at higher flow rates. We showed that the change from increasing to decreasing resonance frequency shift occurred at a lower fluid flow speed for BT, BC, and BS spores than for BA spores. This trend reduces the cross reactivity ratio of BC, BS, and BT to the anti-BA spore IgG immobilized PEMS from around 0.4 at low flow velocities to less than 0.05 at 3.8 mm s−1. This cross reactivity ratio of 0.05 was essentially negligible considering the experimental uncertainty. The use of the same flow that is used for detection to further distinguish the specific binding (BA to anti-BA spore antibody) from nonspecific binding (BT, BC, and BS to anti-BA spore antibody) is unique and has great potential in the detection of general biological species. PMID:18427687

  17. Piezoelectric wave motor

    DOEpatents

    Yerganian, Simon Scott

    2003-02-11

    A piezoelectric motor having a stator in which piezoelectric elements are contained in slots formed in the stator transverse to the desired wave motion. When an electric field is imposed on the elements, deformation of the elements imposes a force perpendicular to the sides of the slot, deforming the stator. Appropriate frequency and phase-shifting of the electric field will produce a wave in the stator and motion in a rotor. In a preferred aspect, the piezoelectric elements are configured so that deformation of the elements in the direction of an imposed electric field, generally referred to as the d.sub.33 direction, is utilized to produce wave motion in the stator. In a further aspect, the elements are compressed into the slots so as to minimize tensile stresses on the elements in use.

  18. Piezoelectric wave motor

    DOEpatents

    Yerganian, Simon Scott

    2001-07-17

    A piezoelectric motor having a stator in which piezoelectric elements are contained in slots formed in the stator transverse to the desired wave motion. When an electric field is imposed on the elements, deformation of the elements imposes a force perpendicular to the sides of the slot, deforming the stator. Appropriate frequency and phase shifting of the electric field will produce a wave in the stator and motion in a rotor. In a preferred aspect, the piezoelectric elements are configured so that deformation of the elements in direction of an imposed electric field, generally referred to as the d.sub.33 direction, is utilized to produce wave motion in the stator. In a further aspect, the elements are compressed into the slots so as to minimize tensile stresses on the elements in use.

  19. Digital enhancement of flow field images

    NASA Technical Reports Server (NTRS)

    Kudlinski, Robert A.; Park, Stephen K.

    1988-01-01

    Most photographs of experimentally generated fluid flow fields have inherently poor photographic quality, specifically low contrast. Thus, there is a need to establish a process for quickly and accurately enhancing these photographs to provide improved versions for physical interpretation, analysis, and publication. A sequence of digital image processing techniques which have been demonstrated to effectively enhance such photographs is described.

  20. Dual-enhancement of ferro-/piezoelectric and photoluminescent performance in Pr{sup 3+} doped (K{sub 0.5}Na{sub 0.5})NbO{sub 3} lead-free ceramics

    SciTech Connect

    Wei, Yongbin; Jia, Yanmin E-mail: ymjia@zjnu.edu.cn; Wu, Jiang; Shen, Yichao; Wu, Zheng E-mail: ymjia@zjnu.edu.cn; Luo, Haosu

    2014-07-28

    A mutual enhancement action between the ferro-/piezoelectric polarization and the photoluminescent performance of rare earth Pr{sup 3+} doped (K{sub 0.5}Na{sub 0.5})NbO{sub 3} (KNN) lead-free ceramics is reported. After Pr{sup 3+} doping, the KNN ceramics exhibit the maximum enhancement of ∼1.2 times in the ferroelectric remanent polarization strength and ∼1.25 times in the piezoelectric coefficient d{sub 33}, respectively. Furthermore, after undergoing a ferro-/piezoelectric polarization treatment, the maximum enhancement of ∼1.3 times in photoluminescence (PL) was observed in the poled 0.3% Pr{sup 3+} doped sample. After the trivalent Pr{sup 3+} unequivalently substituting the univalent (K{sub 0.5}Na{sub 0.5}){sup +}, A-sites ionic vacancies will occur to maintain charge neutrality, which may reduce the inner stress and ease the domain wall motions, yielding to the enhancement in ferro-/piezoelectric performance. The polarization-induced enhancement in PL is attributed to the decrease of crystal symmetry abound the Pr{sup 3+} ions after polarization. The dual-enhancement of the ferro-/piezoelectric and photoluminescent performance makes the Pr{sup 3+} doped KNN ceramic hopeful for piezoelectric/luminescent multifunctional devices.

  1. Flow-enhanced detection of biological pathogens using piezoelectric microcantilever arrays

    NASA Astrophysics Data System (ADS)

    McGovern, John-Paul

    The piezoelectric microcantilever sensor (PEMS) is an all-electrical resonant oscillator biosensor system capable of in-situ and label-free detection. With various insulation and antibody immobilization schemes, it is well-suited for sensitive, specific pathogen detection applications with limits of detection on the order of relevant lethal infectious dosages. Initial PEMS implementation demonstrated biodetection of just 36 total Bacillus anthracis (BA) spores in 0.8 ml of liquid. However, concerns of cross reactivity between the antibody and closely related species of the target pathogens casts doubts on the usefulness of antibody-based assays in terms of the specificity of detection. The goal of this thesis is to develop the PEMS as a method for in-situ, label-free, pathogen detection with better limits of detection than current antibody-based methods as well as high sensitivity and specificity, by exploring PEMS array detection and engineered fluidics specificity augmentation. Experimentation in an 8 mm wide channel revealed that optimal discriminatory detection of BA spores among close cousins (B. cereus (BC), thuringiensis (BT) and subtilis (BS)) was achieved at 14 ml/min. At this flow rate, the detection signals of BC, BT, and BS all fell to within the noise level of the sensor, while that of BA was still nearly optimal. Thus, it was deduced that the interaction forces of BC, BT, and BS were 100 pN. Implementation of array sensing systems enabled real-time, redundant biosensor assays and concurrent background determination by a reference PEMS. Consequentially, successful real-time detection of 10 BA spores/ml was achieved, and single Cryptosporidium parvum (CP) oocyst detection at 0.1 oocysts/ml was accomplished with step-wise resonance frequency shifts of 290 Hz and signal to noise ratios (SNR) greater than 5. In a 19 mm wide flow channel, optimal single oocyst detection efficiency was achieved at 2 ml/min. Optimal discrimination of CP from C. muris (CM

  2. Piezoelectric Motors and Transformers

    NASA Astrophysics Data System (ADS)

    Uchino, K.

    Piezoelectric ceramics forms a new field between electronic and structural ceramics [1-4]. Application fields are classified into three categories: positioners, motors, and vibration suppressors. From the market research result for 80 Japanese component industries in 1992, tiny motors in the range of 5-8 mm are required in large numbers for office and portable equipment; the conventional electromagnetic (EM) motors are rather difficult to produce in this size with sufficient energy efficiency, while Silicon MEMS actuators are too small to be used in practice. Piezoelectric ultrasonic motors whose efficiency is insensitive to size are superior in the millimeter motor area. The manufacturing precision of optical instruments such as lasers and cameras, and the positioning accuracy for fabricating semiconductor chips are of the order of 0.1μm which is much smaller than the backlash of the EM motors. Vibration suppression in space structures and military vehicles also require compact but mighty piezoelectric actuators.

  3. Significantly enhanced piezoelectricity in low-temperature sintered Aurivillius-type ceramics with ultrahigh Curie temperature of 800 °C

    NASA Astrophysics Data System (ADS)

    Cai, Kai; Huang, Chengcheng; Guo, Dong

    2017-04-01

    We report an Aurivillius-type piezoelectric ceramic (Ca1‑2x (LiCe) x Bi4Ti3.99Zn0.01O15) that has an ultrahigh Curie temperature (T c) around 800 °C and a significantly enhanced piezoelectric coefficient (d 33), comparable to that of textured ceramics fabricated using the complicated templating method. Surprisingly, the highest d 33 of 26 pC/N was achieved at an unexpectedly low sintering temperature (T s) of only 920 °C (~200 °C lower than usual) despite the non-ideal density. Study of different synthesized samples indicates that a relatively low T s is crucial for suppressing Bi evaporation and abnormal grain growth, which are indispensable for high resistivity and effective poling due to decreased carrier density and restricted anisotropic conduction. Because the layered structure is sensitive to lattice defects, controlled Bi loss is considered to be crucial for maintaining structural order and spontaneous polarization. This low-T s system is very promising for practical applications due to its high piezoelectricity, low cost and high reproducibility. Contrary to our usual understanding, the results reveal that a delicate balance of density, Bi loss and grain morphology achieved by adjusting the sintering temperature is crucial for the enhancing performance in Aurivillius-type high-T c ceramics.

  4. Q-factor enhancement for self-actuated self-sensing piezoelectric MEMS resonators applying a lock-in driven feedback loop

    NASA Astrophysics Data System (ADS)

    Kucera, M.; Manzaneque, T.; Sánchez-Rojas, J. L.; Bittner, A.; Schmid, U.

    2013-08-01

    This paper presents a robust Q-control approach based on an all-electrical feedback loop enhancing the quality factor of a resonant microstructure by using the self-sensing capability of a piezoelectric thin film actuator made of aluminium nitride. A lock-in amplifier is used to extract the feedback signal which is proportional to the piezoelectric current. The measured real part is used to replace the originally low-quality and noisy feedback signal to modulate the driving voltage of the piezoelectric thin-film actuator. Since the lock-in amplifier reduces the noise in the feedback signal substantially, the proposed enhancement loop avoids the disadvantage of a constant signal-to-noise ratio, which an analogue feedback circuit usually suffers from. The quality factor was increased from the intrinsic value of 1766 to a maximum of 34 840 in air. These promising results facilitate precise measurements for self-actuated and self-sensing MEMS cantilevers even when operated in static viscous media.

  5. Piezoelectric Film.

    ERIC Educational Resources Information Center

    Garrison, Steve

    1992-01-01

    Presents activities that utilize piezoelectric film to familiarize students with fundamental principles of electricity. Describes classroom projects involving chemical sensors, microbalances, microphones, switches, infrared sensors, and power generation. (MDH)

  6. Field Enhancement using Noble Metal Structures

    NASA Astrophysics Data System (ADS)

    Liu, Benliang

    Resonance may be one of the most fundamental rules of nature. Electromagnetic resonance at nanometer scale could produce a giant field enhancement at optical frequency, providing a way to measure and control the process of atoms and molecules at single molecule scale. For example, the giant field enhancement would provide single molecule sensitivity for Raman scattering, which provides unique tools in measuring the quantity in extremely low concentration. In addition, light-emitting diodes could have high brightness but low input power that would be revolutionary in the optoelectronic industry. Although light enhancement is promising in several key technology areas, there are several challenges remain to be tackled. In particular, since the field enhancement is so strongly geometry dependent that slight modification of the geometry can lead to large variations in the outcome, a thorough understanding in how the geometry of the structure affects the field enhancement and creating proper methods to fabricate these structures reproducibly is of most importance. This thesis is devoted to design, fabrication and characterization of field enhancement generated on the surface of noble metals such as silver or gold with 1D structure. The s-polarized field enhancement arising from one-dimensional metal gratings is designed and optimized by using Rigorous Coupling Wave Analysis (RCWA). After optimization, the strongest enhancement factor is found to be 9.7 for 514nm wavelength light. The theoretical results arc confirmed by angle-dependent reflectivity measurements and the experimental results are found to support the theory. A novel single slit structure employing surface plasmon polaritons (SPPs) for enhancing the electric field is studied. SPPs are first generated on a 50 nm thick metal film using attenuated total reflection coupling, and they are subsequently coupled to the cavity mode induced by the single slit. As a result, the field enhancement is found at least 3

  7. Giant field enhancement in electromagnetic Helmholtz nanoantenna

    NASA Astrophysics Data System (ADS)

    Chevalier, Paul; Bouchon, Patrick; Greffet, Jean-Jacques; Pelouard, Jean-Luc; Haïdar, Riad; Pardo, Fabrice

    2014-11-01

    Inspired by the acoustic Helmholtz resonator, we propose a slit-box electromagnetic nanoantenna able to concentrate the energy of an incident beam into surfaces a thousand times smaller than with a classical lens. This design produces a giant electric field enhancement throughout the slit. The intensity enhancement reaches 104 in the visible range up to 108 in the THz range even with focused beams, thanks to an omnidirectional reception. These properties could target applications requiring extreme light concentration, such as surface-enhanced infrared absorption, nonlinear optics, and biophotonics.

  8. Determination of piezoelectric and spontaneous polarization fields in CdZnO/ZnO quantum wells grown along the polar <0001> direction

    NASA Astrophysics Data System (ADS)

    Benharrats, F.; Zitouni, K.; Kadri, A.; Gil, B.

    2010-05-01

    By iteratively solving the Schrödinger and Poisson equations, we determine theoretical values of built-in electric field induced by spontaneous and piezoelectric polarizations in würtzite Cd xZn 1- xO/ZnO ( x≤0.2) quantum wells (QWs) grown along <0001> polar direction. By adjusting recent photoluminescence data, we find that this internal field increases with x with a linear slope A=17.83 MV/cm. Spontaneous and piezoelectric polarization variations are also determined together with the sheet charge densities at Cd xZn 1- xO/ZnO heterointerface. Our results indicate similar, but much stronger polarization effects than previously reported for Mg xZn 1- xO/ZnO QWs. They constitute record polarization effects ever reported for wide bandgap heterostructures, including group III-nitrides.

  9. Modulation of the properties of thin ferromagnetic films with an externally applied electric field in ferromagnetic/piezoelectric/ferromagnetic hybrids

    NASA Astrophysics Data System (ADS)

    Stamopoulos, D.; Zeibekis, M.; Zhang, S. J.

    2013-10-01

    In many cases, technological advances are based on artificial low-dimensional structures of heterogeneous constituents, thus called hybrids, that when come together they provide stand-alone entities that exhibit entirely different properties. Such hybrids are nowadays intensively studied since they are attractive for both basic research and oncoming practical applications. Here, we studied hybrids constituted of piezoelectric (PE) and ferromagnetic (FM) components in the form FM/PE/FM, ultimately aiming to provide means for the controlled modulation of the properties of the FM electrodes, originating from the strain imposed to them by the PE mediator when an electric field is applied. The PE component is in single crystal form, 0.71Pb(Mg1/3Nb2/3)O3-0.29PbTiO3 (PMN-PT), while the FM outer layers are Cobalt (Co) in thin film form. Detailed magnetization measurements performed under variation of the electric field applied to PMN-PT demonstrated the efficient modulation of the properties of the Co electrodes at low temperature (coercive field modulation up to 27% and saturation magnetization absolute modulation up to 4% at T = 10 K for electric field not exceeding 6 kV/cm). The modulation degree faints upon increase of the temperature, evidencing that the thermal energy eventually dominates all other relevant energy scales. Candidate mechanisms are discussed for the explanation of these experimental observations. The results presented here demonstrate that commercially available materials can result in quantitatively noticeable effects. Thus, such elemental Co/PMN-PT/Co units can be used as a solid basis for the development of devices.

  10. Surfactant-enhanced alkaline flooding field project

    SciTech Connect

    French, T.R.

    1991-10-01

    The Tucker sand of Helper (KS) field is a candidate for surfactant-enhanced alkaline flooding. The geology of the Helper site is typical of many DOE Class I reservoirs. The Tucker sand of Helper field was deposited in a fluvial dominated deltaic environment. Helper oil can be mobilized with either chemical system 2 or chemical system 3, as described in this report. Oil fields in the Gulf Coast region are also good candidates for surfactant-enhanced alkaline flooding. The results from laboratory tests conducted in Berea sandstone cores with oil brine from Helper (KS) field are encouraging. The crude oil is viscous and non-acidic and, yet, was mobilized by the chemical formulations described in this report. Significant amounts of the oil were mobilized under simulated reservoir conditions. The results in Berea sandstone cores were encouraging and should be verified by tests with field core. Consumption of alkali, measured with field core, was very low. Surfactant loss appeared to be acceptable. Despite the good potential for mobilization of Helper oil, certain reservoir characteristics such as low permeability, compartmentalization, and shallow depth place constraints on applications of any chemical system in the Tucker sand. These constraints are typical of many DOE Class I reservoirs. Although Hepler field is not a perfect reservoir in which to apply surfactant- enhanced alkaline flooding, Hepler oil is particularly amenable to mobilization by surfactant-enhanced alkaline systems. A field test is recommended, dependent upon final evaluation of well logs and cores from the proposed pilot area. 14 refs., 21 figs., 10 tabs.

  11. Piezoelectric extraction of ECG signal.

    PubMed

    Ahmad, Mahmoud Al

    2016-11-17

    The monitoring and early detection of abnormalities or variations in the cardiac cycle functionality are very critical practices and have significant impact on the prevention of heart diseases and their associated complications. Currently, in the field of biomedical engineering, there is a growing need for devices capable of measuring and monitoring a wide range of cardiac cycle parameters continuously, effectively and on a real-time basis using easily accessible and reusable probes. In this paper, the revolutionary generation and extraction of the corresponding ECG signal using a piezoelectric transducer as alternative for the ECG will be discussed. The piezoelectric transducer pick up the vibrations from the heart beats and convert them into electrical output signals. To this end, piezoelectric and signal processing techniques were employed to extract the ECG corresponding signal from the piezoelectric output voltage signal. The measured electrode based and the extracted piezoelectric based ECG traces are well corroborated. Their peaks amplitudes and locations are well aligned with each other.

  12. Piezoelectric extraction of ECG signal

    NASA Astrophysics Data System (ADS)

    Ahmad, Mahmoud Al

    2016-11-01

    The monitoring and early detection of abnormalities or variations in the cardiac cycle functionality are very critical practices and have significant impact on the prevention of heart diseases and their associated complications. Currently, in the field of biomedical engineering, there is a growing need for devices capable of measuring and monitoring a wide range of cardiac cycle parameters continuously, effectively and on a real-time basis using easily accessible and reusable probes. In this paper, the revolutionary generation and extraction of the corresponding ECG signal using a piezoelectric transducer as alternative for the ECG will be discussed. The piezoelectric transducer pick up the vibrations from the heart beats and convert them into electrical output signals. To this end, piezoelectric and signal processing techniques were employed to extract the ECG corresponding signal from the piezoelectric output voltage signal. The measured electrode based and the extracted piezoelectric based ECG traces are well corroborated. Their peaks amplitudes and locations are well aligned with each other.

  13. Static electric field enhancement in nanoscale structures

    NASA Astrophysics Data System (ADS)

    Lepetit, Bruno; Lemoine, Didier; Márquez-Mijares, Maykel

    2016-08-01

    We study the effect of local atomic- and nano-scale protrusions on field emission and, in particular, on the local field enhancement which plays a key role as known from the Fowler-Nordheim model of electronic emission. We study atomic size defects which consist of right angle steps forming an infinite length staircase on a tungsten surface. This structure is embedded in a 1 GV/m ambient electrostatic field. We perform calculations based upon density functional theory in order to characterize the total and induced electronic densities as well as the local electrostatic fields taking into account the detailed atomic structure of the metal. We show how the results must be processed to become comparable with those of a simple homogeneous tungsten sheet electrostatic model. We also describe an innovative procedure to extrapolate our results to nanoscale defects of larger sizes, which relies on the microscopic findings to guide, tune, and improve the homogeneous metal model, thus gaining predictive power. Furthermore, we evidence analytical power laws for the field enhancement characterization. The main physics-wise outcome of this analysis is that limited field enhancement is to be expected from atomic- and nano-scale defects.

  14. Treatment with orthophosphoric acid enhances the thermal stability of the piezoelectricity in low-density polyethylene ferroelectrets

    NASA Astrophysics Data System (ADS)

    Rychkov, Dmitry; Alberto Pisani Altafim, Ruy; Qiu, Xunlin; Gerhard, Reimund

    2012-06-01

    Ferroelectrets have been fabricated from low-density polyethylene (LDPE) films by means of a template-based lamination. The temperature dependence of the piezoelectric d33 coefficient has been investigated. It was found that low-density polyethylene ferroelectrets have rather low thermal stability with the piezoelectric coefficient decaying almost to zero already at 100 °C. This behavior is attributed to the poor electret properties of the polyethylene films used for the fabrication of the ferroelectrets. In order to improve the charge trapping and the thermal stability of electret charge and piezoelectricity, LDPE ferroelectrets were treated with orthophosphoric acid. The treatment resulted in considerable improvements of the charge stability in LDPE films and in ferroelectret systems made from them. For example, the charge and piezoelectric-coefficient decay curves shifted to higher temperatures by 60 K and 40 K, respectively. It is shown that the decay of the piezoelectric coefficient in LDPE ferroelectrets is governed by the relaxation of less stable positive charges. The treatment also leads to noticeable changes in the chemical composition of the LDPE surface. Infrared spectroscopy reveals absorption bands attributed to phosphorus-containing structures, while scanning electron microscopy shows new island-like structures, 50-200 nm in diameter, on the modified surface.

  15. A new global approach using a network of piezoelectric elements and energy redistribution for enhanced vibration damping of smart structure

    NASA Astrophysics Data System (ADS)

    Wu, Dan; Guyomar, Daniel; Richard, Claude

    2013-04-01

    A new global approach for improved vibration damping of smart structure, based on global energy redistribution by means of a network of piezoelectric elements is proposed. It is basically using semi-active Synchronized Switch Damping technique. SSD technique relies on a cumulative build-up of the voltage resulting from the continuous switching and it was shown that the performance is strongly related to this voltage. The increase of the piezoelectric voltage results in improvement of the damping performance. External voltage sources or improved switching sequences were previously designed to increase this voltage in the case of single piezoelectric element structure configurations. This paper deals with extended structure with many embedded piezoelectric elements. The proposed strategy consist of using an electric network made with non-linear component and switches in order to set up and control a low-loss energy transfer from source piezoelements extracting the vibration energy of the structure and oriented toward a given piezoelement in order to increase its operative energy for improving a given mode damping. This paper presents simulation of a clamped plate with four piezoelectric elements implemented in the Matlab/SimulinkTM environment and SimscapeTM library. The various simulation cases show the relationship between the damping performance on a given targeted mode and the established power flow. SSDD and SSDT are two proposed original networks. Performances are compared to the SSDI baseline. A damping increase of 18dB can be obtained even with a weakly coupled piezoelectric element in the multi-sine excitation case. This result proves the importance of new global non-linear multi-actuator strategies for improved vibration damping of extended smart structure.

  16. Impedance characterization of a piezoelectric immunosensor part II: Salmonella typhimurium detection using magnetic enhancement.

    PubMed

    Kim, Gi Ho; Rand, A Garth; Letcher, Stephen V

    2003-01-01

    This study investigated the usefulness and characteristics of a 5-MHz quartz crystal resonator as a sensor of biological pathogens such as Salmonella typhimurium. An impedance analyzer measured the impedance behavior of the oscillating quartz crystal exposed to various concentrations of Salmonella (10(2)-10(8) cells per ml). The Salmonella cells were captured by antibody-coated paramagnetic microspheres, and then these complexes were moved magnetically to the sensing quartz and were captured by antibodies immobilized on the crystal surface. The response of the crystal was expressed in terms of equivalent circuit parameters. The motional inductance and the motional resistance increased as a function of the concentration of Salmonella. The viscous damping was the main contributor to the resistance and the inductance in a liquid environment. The load resistance was the most effective and sensitive circuit parameter. A magnetic force was a useful method to collect the complexes of Salmonella-microspheres on the crystal surface and enhance the response of the sensor. In this system, the detection limit, based on resistance monitoring, was about 10(3) cells per ml.

  17. Enhanced mathematical modeling of the displacement amplification ratio for piezoelectric compliant mechanisms

    NASA Astrophysics Data System (ADS)

    Ling, Mingxiang; Cao, Junyi; Zeng, Minghua; Lin, Jing; Inman, Daniel J.

    2016-07-01

    Piezo-actuated, flexure hinge-based compliant mechanisms have been frequently used in precision engineering in the last few decades. There have been a considerable number of publications on modeling the displacement amplification behavior of rhombus-type and bridge-type compliant mechanisms. However, due to an unclear geometric approximation and mechanical assumption between these two flexures, it is very difficult to obtain an exact description of the kinematic performance using previous analytical models, especially when the designed angle of the compliant mechanisms is small. Therefore, enhanced theoretical models of the displacement amplification ratio for rhombus-type and bridge-type compliant mechanisms are proposed to improve the prediction accuracy based on the distinct force analysis between these two flexures. The energy conservation law and the elastic beam theory are employed for modeling with consideration of the translational and rotational stiffness. Theoretical and finite elemental results show that the prediction errors of the displacement amplification ratio will be enlarged if the bridge-type flexure is simplified as a rhombic structure to perform mechanical modeling. More importantly, the proposed models exhibit better performance than the previous models, which is further verified by experiments.

  18. Silicon nanopillars for field enhanced surface spectroscopy

    SciTech Connect

    Wells, Sabrina M; Merkulov, Igor A; Kravchenko, Ivan I; Lavrik, Nickolay V; Sepaniak, Michael J

    2012-01-01

    Silicon nanowire and nanopillar structures have continued to draw increased attention in recent years due in part to their unique optical properties. Herein, electron beam lithography combined with reactive-ion etching is used to reproducibly create individual silicon nanopillars of various sizes, shapes, and heights. Finite difference time domain numerical analysis predicts enhancements in localized fields in the vicinity of appropriately-sized and coaxially-illuminated silicon nanopillars of approximately two orders of magnitude. By analyzing experimentally measured strength of the silicon Raman phonon line (500 cm-1), it was determined that nanopillars produced field enhancement that are consistent with these predictions. Additionally, we demonstrate that a thin layer of Zn phthalocyanine deposited on the nanopillar surface produced prominent Raman spectra yielding enhancement factors (EFs) better than 300. Finally, silicon nanopillars of cylindrical and elliptical shapes were labeled with different fluorophors and evaluated for their surface enhanced fluorescence (SEF) capability. The EF derived from analysis of the acquired fluorescence microscopy images indicate that silicon nanopillar structures can provide enhancement comparable or even stronger than those typically achieved using plasmonic SEF structures without the drawbacks of the metal-based substrates. It is anticipated that scaled up arrays of silicon nanopillars will enable SEF assays with extremely high sensitivity, while a broader impact of the reported phenomena are anticipated in photovoltaics, subwavelength light focusing, and fundamental nanophotonics.

  19. Giant electric-field-induced strain in lead-free piezoelectric materials

    PubMed Central

    Chen, Lan; Yang, Yurong; Meng, X. K.

    2016-01-01

    First-principles calculations are performed to investigate the structures, electrical, and magnetic properties of compressive BiFeO3 films under electric-field and pressure perpendicular to the films. A reversible electric-field-induced strain up 10% is achieved in the compressive BiFeO3 films. The giant strain originates from rhombohedral-tetragonal (R-T) phase transition under electric-filed, and is recoverable from tetragonal-rhombohedral (T-R) phase transition by compressive stress. Additionally, the weak ferromagnetism in BiFeO3 films is largely changed in R-T phase transition under electric-filed and T-R phase transition under pressure – reminiscent of magnetoelectric effect and magnetoelastic effect. These results suggest exciting device opportunities arising from the giant filed-induced strain, large magnetoelectric effect and magnetoelastic effect. PMID:27139526

  20. Piezoelectric transducer

    NASA Technical Reports Server (NTRS)

    Conragan, J.; Muller, R. S.

    1970-01-01

    Transducer consists of a hybrid thin film and a piezoelectric transistor that acts as a stress-sensitive device with built-in gain. It provides a stress/strain transducer that incorporates a signal amplification stage and sensor in a single package.

  1. A nanoscale piezoelectric transformer for low-voltage transistors.

    PubMed

    Agarwal, Sapan; Yablonovitch, Eli

    2014-11-12

    A novel piezoelectric voltage transformer for low-voltage transistors is proposed. Placing a piezoelectric transformer on the gate of a field-effect transistor results in the piezoelectric transformer field-effect transistor that can switch at significantly lower voltages than a conventional transistor. The piezoelectric transformer operates by using one piezoelectric to squeeze another piezoelectric to generate a higher output voltage than the input voltage. Multiple piezoelectrics can be used to squeeze a single piezoelectric layer to generate an even higher voltage amplification. Coupled electrical and mechanical modeling in COMSOL predicts a 12.5× voltage amplification for a six-layer piezoelectric transformer. This would lead to more than a 150× reduction in the power needed for communications.

  2. Additional Drive Circuitry for Piezoelectric Screw Motors

    NASA Technical Reports Server (NTRS)

    Smythe, Robert; Palmer, Dean; Gursel, Yekta; Reder, Leonard; Savedra, Raymond

    2004-01-01

    Modules of additional drive circuitry have been developed to enhance the functionality of a family of commercially available positioning motors (Picomotor . or equivalent) that provide linear motion controllable, in principle, to within increments .30 nm. A motor of this type includes a piezoelectric actuator that turns a screw. Unlike traditional piezoelectrically actuated mechanisms, a motor of this type does not rely on the piezoelectric transducer to hold position: the screw does not turn except when the drive signal is applied to the actuator.

  3. Orientation field estimation for latent fingerprint enhancement.

    PubMed

    Feng, Jianjiang; Zhou, Jie; Jain, Anil K

    2013-04-01

    Identifying latent fingerprints is of vital importance for law enforcement agencies to apprehend criminals and terrorists. Compared to live-scan and inked fingerprints, the image quality of latent fingerprints is much lower, with complex image background, unclear ridge structure, and even overlapping patterns. A robust orientation field estimation algorithm is indispensable for enhancing and recognizing poor quality latents. However, conventional orientation field estimation algorithms, which can satisfactorily process most live-scan and inked fingerprints, do not provide acceptable results for most latents. We believe that a major limitation of conventional algorithms is that they do not utilize prior knowledge of the ridge structure in fingerprints. Inspired by spelling correction techniques in natural language processing, we propose a novel fingerprint orientation field estimation algorithm based on prior knowledge of fingerprint structure. We represent prior knowledge of fingerprints using a dictionary of reference orientation patches. which is constructed using a set of true orientation fields, and the compatibility constraint between neighboring orientation patches. Orientation field estimation for latents is posed as an energy minimization problem, which is solved by loopy belief propagation. Experimental results on the challenging NIST SD27 latent fingerprint database and an overlapped latent fingerprint database demonstrate the advantages of the proposed orientation field estimation algorithm over conventional algorithms.

  4. Piezoelectric Films for Innovations in the Field of MEMS and Biosensors

    NASA Astrophysics Data System (ADS)

    Muralt, P.

    Microelectromechanical systems (MEMS) were born as a new technological discipline during the 1980s (for an introductory textbook, see, for instance [1]). The idea of the pioneers was to enlarge capabilities of integrated circuits based on silicon beyond pure electronics by adding mechanical elements, which were made of silicon and further materials of semiconductor technology. The addition of mechanics extended the application range of silicon technology to motion sensors, pressure and force sensors, small actuators, and a number of acoustic and ultrasonic devices, most importantly resonators for signal treatment. In order to profit from the symbiosis with electronics, those mechanical elements should, of course, be controlled by electronic signals. Evidently, this new silicon technology makes sense only for small, miniaturized devices. The technical advantage comes from the fact that powerful thin-film deposition and patterning techniques as used for semiconductor fabrication allow unprecedented precision of mechanics in the nano- to micrometer range. As a large number of devices are produced in parallel on the same wafer (batch processing), the cost level is acceptable in spite of expensive fabrication tools, at least at high production volumes. Concerning processing, the chemistry of silicon turned out to be very helpful: high etching rates of anisotropic wet etching in a base solution (as, e.g., KOH) and anisotropic deep silicon etching in a plasma reactor are crucial issues in efficiently tailoring silicon. Over the last 20 years, MEMS technology has became a proven and mature technology with many applications. While "MEMS" is still taken as a standing brand name for the field, the actual MEMS field has become much wider than stipulated by the notion of electromechanics, including thermal, optical, magnetic, chemical, biochemical, and further functional properties. Also, the main material of the device is not necessarily silicon, but may be glass or plastics

  5. Patterned growth of ZnO nanowires on flexible substrates for enhanced performance of flexible piezoelectric nanogenerators

    NASA Astrophysics Data System (ADS)

    Yang, Dechao; Qiu, Yu; Jiang, Qingyu; Guo, Zhaoshuai; Song, Wenbin; Xu, Jin; Zong, Yang; Feng, Qiuxia; Sun, Xiaoling

    2017-02-01

    Flexible piezoelectric nanogenerators (NGs) based on patterned growth of ZnO nanowires (PNWs) by the hydrothermal method are proposed for high-efficiency energy harvesting applications. The use of the PNWs in ZnO-based FPNGs results in a significant improvement in terms of the magnitude of the output currents of up to 6 times when compared with pristine ZnO NW-based FPNGs without patterned growth mode. The maximum output current was measured to be about 150 nA, which was enough to drive some micro/nanoelectronic devices. The improved output performance is mainly attributed to the patterned growth mode in FPNGs, which may significantly reduce the piezoelectric potential screening effect caused by free electrons in ZnO. This strategy may provide a highly promising platform as energy harvesting devices for viable industrial applications in portable/wearable nanodevices.

  6. Harmonic demodulation and minimum enhancement factors in field-enhanced near-field optical microscopy.

    PubMed

    Scarpettini, A F; Bragas, A V

    2015-01-01

    Field-enhanced scanning optical microscopy relies on the design and fabrication of plasmonic probes which had to provide optical and chemical contrast at the nanoscale. In order to do so, the scattering containing the near-field information recorded in a field-enhanced scanning optical microscopy experiment, has to surpass the background light, always present due to multiple interferences between the macroscopic probe and sample. In this work, we show that when the probe-sample distance is modulated with very low amplitude, the higher the harmonic demodulation is, the better the ratio between the near-field signal and the interferometric background results. The choice of working at a given n harmonic is dictated by the experiment when the signal at the n + 1 harmonic goes below the experimental noise. We demonstrate that the optical contrast comes from the nth derivative of the near-field scattering, amplified by the interferometric background. By modelling the far and near field we calculate the probe-sample approach curves, which fit very well the experimental ones. After taking a great amount of experimental data for different probes and samples, we conclude with a table of the minimum enhancement factors needed to have optical contrast with field-enhanced scanning optical microscopy.

  7. Enhanced visual fields in hammerhead sharks.

    PubMed

    McComb, D M; Tricas, T C; Kajiura, S M

    2009-12-01

    Several factors that influence the evolution of the unusual head morphology of hammerhead sharks (family Sphyrnidae) are proposed but few are empirically tested. In this study we tested the 'enhanced binocular field' hypothesis (that proposes enhanced frontal binocularity) by comparison of the visual fields of three hammerhead species: the bonnethead shark, Sphyrna tiburo, the scalloped hammerhead shark, Sphyrna lewini, and the winghead shark, Eusphyra blochii, with that of two carcharhinid species: the lemon shark, Negaprion brevirostris, and the blacknose shark, Carcharhinus acronotus. Additionally, eye rotation and head yaw were quantified to determine if species compensate for large blind areas anterior to the head. The winghead shark possessed the largest anterior binocular overlap (48 deg.) and was nearly four times larger than that of the lemon (10 deg.) and blacknose (11 deg.) sharks. The binocular overlap in the scalloped hammerhead sharks (34 deg.) was greater than the bonnethead sharks (13 deg.) and carcharhinid species; however, the bonnethead shark did not differ from the carcharhinids. These results indicate that binocular overlap has increased with lateral head expansion in hammerhead sharks. The hammerhead species did not demonstrate greater eye rotation in the anterior or posterior direction. However, both the scalloped hammerhead and bonnethead sharks exhibited greater head yaw during swimming (16.9 deg. and 15.6 deg., respectively) than the lemon (15.1 deg.) and blacknose (15.0 deg.) sharks, indicating a behavioral compensation for the anterior blind area. This study illustrates the larger binocular overlap in hammerhead species relative to their carcharhinid sister taxa and is consistent with the 'enhanced binocular field' hypothesis.

  8. Quantum Enhanced Estimation of a Multidimensional Field.

    PubMed

    Baumgratz, Tillmann; Datta, Animesh

    2016-01-22

    We present a framework for the quantum enhanced estimation of multiple parameters corresponding to noncommuting unitary generators. Our formalism provides a recipe for the simultaneous estimation of all three components of a magnetic field. We propose a probe state that surpasses the precision of estimating the three components individually, and we discuss measurements that come close to attaining the quantum limit. Our study also reveals that too much quantum entanglement may be detrimental to attaining the Heisenberg scaling in the estimation of unitarily generated parameters.

  9. Structural Origins of Silk Piezoelectricity

    PubMed Central

    Yucel, Tuna; Cebe, Peggy

    2012-01-01

    Uniaxially oriented, piezoelectric silk films were prepared by a two-step method that involved: (1) air drying aqueous, regenerated silk fibroin solutions into films, and (2) drawing the silk films to a desired draw ratio. The utility of two different drawing techniques, zone drawing and water immersion drawing were investigated for processing the silk for piezoelectric studies. Silk films zone drawn to a ratio of λ= 2.7 displayed relatively high dynamic shear piezoelectric coefficients of d14 = −1.5 pC/N, corresponding to over two orders of magnitude increase in d14 due to film drawing. A strong correlation was observed between the increase in the silk II, β-sheet content with increasing draw ratio measured by FTIR spectroscopy (Cβ∝ e2.5 λ), the concomitant increasing degree of orientation of β-sheet crystals detected via WAXD (FWHM = 0.22° for λ= 2.7), and the improvement in silk piezoelectricity (d14∝ e2.4 λ). Water immersion drawing led to a predominantly silk I structure with a low degree of orientation (FWHM = 75°) and a much weaker piezoelectric response compared to zone drawing. Similarly, increasing the β-sheet crystallinity without inducing crystal alignment, e.g. by methanol treatment, did not result in a significant enhancement of silk piezoelectricity. Overall, a combination of a high degree of silk II, β-sheet crystallinity and crystalline orientation are prerequisites for a strong piezoelectric effect in silk. Further understanding of the structural origins of silk piezoelectricity will provide important options for future biotechnological and biomedical applications of this protein. PMID:23335872

  10. Full Piezoelectric Multilayer-Stacked Hybrid Actuation/Transduction Systems

    NASA Technical Reports Server (NTRS)

    Su, Ji; Jiang, Xiaoning; Zu, Tian-Bing

    2011-01-01

    The Stacked HYBATS (Hybrid Actuation/Transduction system) demonstrates significantly enhanced electromechanical performance by using the cooperative contributions of the electromechanical responses of multilayer, stacked negative strain components and positive strain components. Both experimental and theoretical studies indicate that, for Stacked HYBATS, the displacement is over three times that of a same-sized conventional flextensional actuator/transducer. The coupled resonance mode between positive strain and negative strain components of Stacked HYBATS is much stronger than the resonance of a single element actuation only when the effective lengths of the two kinds of elements match each other. Compared with the previously invented hybrid actuation system (HYBAS), the multilayer Stacked HYBATS can be designed to provide high mechanical load capability, low voltage driving, and a highly effective piezoelectric constant. The negative strain component will contract, and the positive strain component will expand in the length directions when an electric field is applied on the device. The interaction between the two elements makes an enhanced motion along the Z direction for Stacked-HYBATS. In order to dominate the dynamic length of Stacked-HYBATS by the negative strain component, the area of the cross-section for the negative strain component will be much larger than the total cross-section areas of the two positive strain components. The transverse strain is negative and longitudinal strain positive in inorganic materials, such as ceramics/single crystals. Different piezoelectric multilayer stack configurations can make a piezoelectric ceramic/single-crystal multilayer stack exhibit negative strain or positive strain at a certain direction without increasing the applied voltage. The difference of this innovation from the HYBAS is that all the elements can be made from one-of-a-kind materials. Stacked HYBATS can provide an extremely effective piezoelectric

  11. Piezoelectric Properties of Non-Polar Block Copolymers

    SciTech Connect

    Pester, Christian; Ruppel, Markus A; Schoberth, Heiko; Schmidt, K.; Liedel, Clemens; Van Rijn, Patrick; Littrell, Ken; Schindler, Kerstin; Hiltl, Stephanie; Czubak, Thomas; Mays, Jimmy; Urban, Volker S; Boker, Alexander

    2011-01-01

    Piezoelectric properties in non-polar block copolymers are a novelty in the field of electroactive polymers. The piezoelectric susceptibility of poly(styrene-b-isoprene) block copolymer lamellae is found to be up to an order of magnitude higher when compared to classic piezoelectric materials. The electroactive response increases with temperature and is found to be strongest in the disordered phase.

  12. Effects of surface tension and axis stress on piezoelectric behaviors of ferroelectric nanowires

    NASA Astrophysics Data System (ADS)

    Chen, Y. Q.; En, Y. F.; Huang, Y.; Kong, X. D.; Zheng, X. J.; Lu, Y. D.

    2011-11-01

    The effects of surface tension and axis stress on piezoelectric behaviors of ferroelectric nanowires with radius polarization were investigated by the time-dependent Ginzburg-Landau theory. When surface tension increases, both of coercive field and remnant strain decrease. The larger the surface tension is, the more they decrease. The axis compressive stress enhances the coercive field and remnant strain, while the axis tensile stress has contrary effect. The reason for the stress-modulated piezoelectricity is that radius polarization is forced by axis compressive stress but restrained by surface tension and axis tensile stress. The research is useful for ferroelectric nanostructures in strain engineering.

  13. Enhanced piezoelectric performance of (0.98-x)Bi(Sc{sub 3/4}In{sub 1/4})O{sub 3}-xPbTiO{sub 3}-0.02Pb(Zn{sub 1/3}Nb{sub 2/3})O{sub 3} ternary high temperature piezoelectric ceramics

    SciTech Connect

    Chen Jianguo; Zhao Tianlong; Cheng Jinrong; Dong Shuxiang

    2013-04-14

    (0.98-x)Bi(Sc{sub 3/4}In{sub 1/4})O{sub 3}-xPbTiO{sub 3}-0.02Pb(Zn{sub 1/3}Nb{sub 2/3})O{sub 3} (BSI-PT-PZN) high temperature piezoelectric ceramics were prepared by traditional solid-state reaction method. Combining X-ray diffraction results with piezoelectric data, it was found that the morphotropic phase boundary (MPB) occurred at x = 0.575. The piezoelectric constant d{sub 33}, curie temperature T{sub c}, and electromechanical coupling factor k{sub p} of BIS-PT-PZN ceramics with MPB composition were 427 pC/N, 412 Degree-Sign C, and 0.51, respectively. Furthermore, the strain of BIS-PT-PZN ceramics reached up to 0.25% under the electric field of 40 kV/cm. Temperature-dependent electromechanical coupling coefficient for MPB composition was stable from room temperature up to 350 Degree-Sign C. The piezoelectric properties of BIS-PT-PZN ceramics were comparable to that of 0.36BiScO{sub 3}-0.64PbTiO{sub 3} (BS-PT) ceramics, and the piezoelectric constant d{sub 33} of BIS-PT-PZN ceramics was about twice that of our previous reported 0.4Bi(Sc{sub 3/4}In{sub 1/4})O{sub 3}-0.6PbTiO{sub 3} (BSI-PT) ceramics. The reduction in the expensive Sc{sub 2}O{sub 3} content and comparable piezoelectric properties with BS-PT ceramics indicated that BIS-PT-PZN ceramics were promising for commercial applications as high temperature actuators and sensors.

  14. Piezoelectric wind turbine

    NASA Astrophysics Data System (ADS)

    Kishore, Ravi Anant; Priya, Shashank

    2013-03-01

    In past few years, there has been significant focus towards developing small scale renewable energy based power sources for powering wireless sensor nodes in remote locations such as highways and bridges to conduct continuous health monitoring. These prior efforts have led to the development of micro-scale solar modules, hydrogen fuel cells and various vibration based energy harvesters. However, the cost effectiveness, reliability, and practicality of these solutions remain a concern. Harvesting the wind energy using micro-to-small scale wind turbines can be an excellent solution in variety of outdoor scenarios provided they can operate at few miles per hour of wind speed. The conventional electromagnetic generator used in the wind mills always has some cogging torque which restricts their operation above certain cut-in wind speed. This study aims to develop a novel piezoelectric wind turbine that utilizes bimorph actuators for electro-mechanical energy conversion. This device utilizes a Savonius rotor that is connected to a disk having magnets at the periphery. The piezoelectric actuators arranged circumferentially around the disk also have magnets at the tip which interacts with the magnetic field of the rotating disk and produces cyclical deflection. The wind tunnel experiments were conducted between 2-12 mph of wind speeds to characterize and optimize the power output of the wind turbine. Further, testing was conducted in the open environment to quantify the response to random wind gusts. An attempt was made towards integration of the piezoelectric wind turbine with the wireless sensor node.

  15. Peak divergence in the curve of magnetoelectric coefficient versus dc bias magnetic field at resonance region for bi-layer magnetostrictive/piezoelectric composites

    SciTech Connect

    Zuo, Z. J.; Pan, D. A. Zhang, S. G.; Qiao, L. J.; Jia, Y. M.

    2013-12-15

    Magnetoelectric (ME) coefficient dependence on the bias magnetic field at resonance frequencies for the bi-layered bonded Terfenol-D/Pb(Zr,Ti)O{sub 3} composite was investigated. The resonance frequency decreases first and then increases with the bias magnetic field (H{sub DC}), showing a “V” shape in the range of 0 ∼ 5 kOe. Below the resonance frequency, the pattern of ME coefficient dependence on the H{sub DC} shows a single peak, but splits into a double-peak pattern when the testing frequency increases into a certain region. With increasing the frequency, a divergent evolution of the H{sub DC} patterns was observed. Domain motion and ΔE effect combined with magnetostriction-piezoelectric coupling effect were employed to explain this experimental result.

  16. Relaxor ferroelectricity and electric-field-driven structural transformation in the giant lead-free piezoelectric (Ba ,Ca ) (Ti ,Zr ) O3

    NASA Astrophysics Data System (ADS)

    Brajesh, Kumar; Tanwar, Khagesh; Abebe, Mulualem; Ranjan, Rajeev

    2015-12-01

    There is great interest in lead-free (B a0.85C a0.15 ) (T i0.90Z r0.10 ) O3 (15/10BCTZ) because of its exceptionally large piezoelectric response [Liu and Ren, Phys. Rev. Lett. 103, 257602 (2009), 10.1103/PhysRevLett.103.257602]. In this paper, we have analyzed the nature of: (i) crystallographic phase coexistence at room temperature, (ii) temperature- and field-induced phase transformation to throw light on the atomistic mechanisms associated with the large piezoelectric response of this system. A detailed temperature-dependent dielectric and lattice thermal expansion study proved that the system exhibits a weak dielectric relaxation, characteristic of a relaxor ferroelectric material on the verge of exhibiting a normal ferroelectric-paraelectric transformation. Careful structural analysis revealed that a ferroelectric state at room temperature is composed of three phase coexistences, tetragonal (P 4 m m )+ orthorhombic(Amm 2 )+rhombohedral(R 3 m ) . We also demonstrate that the giant piezoresponse is associated with a significant fraction of the tetragonal phase transforming to rhombohedral. It is argued that the polar nanoregions associated with relaxor ferroelectricity amplify the piezoresponse by providing an additional degree of intrinsic structural inhomogeneity to the system.

  17. A compact ion source and accelerator based on a piezoelectric driver

    SciTech Connect

    Norgard, P.; Kovaleski, S. D.; VanGordon, J. A.; Baxter, E. A.; Gall, B. B.; Kwon, Jae Wan; Kim, Baek Hyun; Dale, G. E.

    2013-04-19

    Compact ion sources and accelerators using piezoelectric devices for the production of energetic ion beams are being evaluated. A coupled source-accelerator is being tested as a neutron source to be incorporated into oil-well logging diagnostics. Two different ion sources are being investigated, including a piezoelectric transformer-based plasma source and a silicon-based field ion source. The piezoelectric transformer plasma ion source uses a cylindrical, resonantly driven piezoelectric crystal to produce high voltage inside a confined volume filled with low pressure deuterium gas. The plasma generated in the confined chamber is ejected through a small aperture into an evacuated drift region. The silicon field ion source uses localized electric field enhancement produced by an array of sharp emitters etched into a silicon blank to produce ions through field desorption ionization. A second piezoelectric device of a different design is used to generate an accelerating potential on the order of 130 kV; this potential is applied to a deuterated target plate positioned perpendicular to the ion stream produced by either plasma source. This paper discusses the results obtained by the individual components as they relate to the final neutron source.

  18. Studying electric field enhancement factor of the nanostructured emission surface

    NASA Astrophysics Data System (ADS)

    Zartdinov, A. N.; Nikiforov, K. A.

    2016-08-01

    Mathematical model of nanostructured field emission surface is proposed. In order to determine geometrical parameters of the surface structure digital processing of scanning electron microscopy images was used. Effective value of local electrical field enhancement factor is defined and calculated within the Fowler-Nordheim theory. It was found effective enhancement factor decreases as the applied electrical field increases for a fixed geometry.

  19. Charge and current reservoirs for electric and magnetic field enhancement.

    PubMed

    Wang, Dongxing; Yang, Tian; Crozier, Kenneth B

    2010-05-10

    Two optical antenna designs incorporating structures termed charge and current reservoirs are proposed to realize localized high electric and magnetic field enhancement, respectively. Simulation results show that the fan-rod electric antenna design combines the advantages of the rod antenna and the bowtie antenna, and has higher field enhancement than either. The performance of a loop shaped magnetic antenna consisting of a pair of metallic strips with offsets is also verified numerically, with high magnetic field enhancement being observed in the simulation. In both of the designs, the concepts of charge and current reservoirs contribute to high electric and magnetic field enhancement.

  20. Piezoelectric extraction of ECG signal

    PubMed Central

    Ahmad, Mahmoud Al

    2016-01-01

    The monitoring and early detection of abnormalities or variations in the cardiac cycle functionality are very critical practices and have significant impact on the prevention of heart diseases and their associated complications. Currently, in the field of biomedical engineering, there is a growing need for devices capable of measuring and monitoring a wide range of cardiac cycle parameters continuously, effectively and on a real-time basis using easily accessible and reusable probes. In this paper, the revolutionary generation and extraction of the corresponding ECG signal using a piezoelectric transducer as alternative for the ECG will be discussed. The piezoelectric transducer pick up the vibrations from the heart beats and convert them into electrical output signals. To this end, piezoelectric and signal processing techniques were employed to extract the ECG corresponding signal from the piezoelectric output voltage signal. The measured electrode based and the extracted piezoelectric based ECG traces are well corroborated. Their peaks amplitudes and locations are well aligned with each other. PMID:27853180

  1. Numerical simulation of piezoelectric effect of bone under ultrasound irradiation

    NASA Astrophysics Data System (ADS)

    Hosokawa, Atsushi

    2015-07-01

    The piezoelectric effect of bone under ultrasound irradiation was numerically simulated using an elastic finite-difference time-domain method with piezoelectric constitutive equations (PE-FDTD method). First, to demonstrate the validity of the PE-FDTD method, the ultrasound propagation in piezoelectric ceramics was simulated and then compared with the experimental results. The simulated and experimental waveforms propagating through the ceramics were in good agreement. Next, the piezoelectric effect of human cortical bone on the ultrasound propagation was investigated by PE-FDTD simulation. The simulated result showed that the difference between the waveforms propagating through the bone without and with piezoelectricity was negligible. Finally, the spatial distributions of the electric fields in a human femur induced by ultrasound irradiation were simulated. The electric fields were changed by a bone fracture, which depended on piezoelectric anisotropy. In conclusion, the PE-FDTD method is considered to be useful for investigating the piezoelectric effect of bone.

  2. Piezoelectric ultrasonic motors

    SciTech Connect

    Wallaschek, J.

    1994-12-31

    Piezoelectric ultrasonic motors are a new type of actuator. They are characterized by high torque at low rotational speed, simple mechanical design and good controllability. They also provide a high holding torque even if no power is applied. Compared to electromagnetic actuators the torque per volume ratio of piezoelectric ultrasonic motors can be higher by an order of magnitude. Recently various types of piezoelectric ultrasonic motors have been developed for industrial applications. This paper describes several types of piezoelectric ultrasonic motors.

  3. "Mighty Worm" Piezoelectric Actuator

    NASA Technical Reports Server (NTRS)

    Bamford, Robert M.; Wada, Ben K.; Moore, Donald M.

    1994-01-01

    "Mighty Worm" piezoelectric actuator used as adjustable-length structural member, active vibrator or vibration suppressor, and acts as simple (fixed-length) structural member when inactive. Load force not applied to piezoelectric element in simple-structural-member mode. Piezoelectric element removed from load path when not in use.

  4. Piezoelectric drive circuit

    DOEpatents

    Treu, C.A. Jr.

    1999-08-31

    A piezoelectric motor drive circuit is provided which utilizes the piezoelectric elements as oscillators and a Meacham half-bridge approach to develop feedback from the motor ground circuit to produce a signal to drive amplifiers to power the motor. The circuit automatically compensates for shifts in harmonic frequency of the piezoelectric elements due to pressure and temperature changes. 7 figs.

  5. Piezoelectric drive circuit

    DOEpatents

    Treu, Jr., Charles A.

    1999-08-31

    A piezoelectric motor drive circuit is provided which utilizes the piezoelectric elements as oscillators and a Meacham half-bridge approach to develop feedback from the motor ground circuit to produce a signal to drive amplifiers to power the motor. The circuit automatically compensates for shifts in harmonic frequency of the piezoelectric elements due to pressure and temperature changes.

  6. Near-field enhanced Raman spectroscopy using side illumination optics

    NASA Astrophysics Data System (ADS)

    Hayazawa, Norihiko; Tarun, Alvarado; Inouye, Yasushi; Kawata, Satoshi

    2002-12-01

    We demonstrate near-field enhanced Raman spectroscopy with the use of a metallized cantilever tip and highly p-polarized light directed onto the tip with side illumination optics using a long working distance objective lens. The highly p-polarized light field excites surface plasmon polaritons localized at the tip apex, which results in the enhanced near-field Raman scattering. In this article, we achieved an enhancement factor of 4000 for Rhodamine 6G molecules adsorbed on a silver island film. The side illumination is also applicable to an opaque sample and to near-field photolithography.

  7. TECHNICAL NOTE: Electrically aligned cellulose film for electro-active paper and its piezoelectricity

    NASA Astrophysics Data System (ADS)

    Yun, Sungryul; Jang, Sangdong; Yun, Gyu-Young; Kim, Jaehwan

    2009-11-01

    Electrically aligned regenerated cellulose films were fabricated and the effect of applied electric field was investigated for the piezoelectricity of electro-active paper (EAPap). The EAPap was fabricated by coating gold electrodes on both sides of regenerated cellulose film. The cellulose film was prepared by dissolving cotton pulp in LiCl/N,N-dimethylacetamide solution followed by a cellulose chain regeneration process. During the regeneration process an external electric field was applied in the direction of mechanical stretching. Alignment of cellulose fiber chains was investigated as a function of applied electric field. The material characteristics of the cellulose films were analyzed by using an x-ray diffractometer, a field emission scanning electron microscope and a high voltage electron microscope. The application of external electric fields was found to induce formation of nanofibers in the cellulose, resulting in an increase in the crystallinity index (CI) values. It was also found that samples with higher CI values showed higher in-plane piezoelectric constant, d31, values. The piezoelectricity of the current EAPap films was measured to be equivalent or better than that of ordinary PVDF films. Therefore, an external electric field applied to a cellulose film along with a mechanical stretching during the regeneration process can enhance the piezoelectricity.

  8. Piezoelectric enhancement of (PbTiO3)m/(BaTiO3)n ferroelectric superlattices through domain engineering

    SciTech Connect

    Hong, Liang; Wu, Pingping; Li, Yulan; Gopalan, Venkatraman; Eom, Chang-Beom; Schlom, Darrell G.; Chen, Long-Qing

    2014-11-01

    The phase diagram of (PbTiO3)m/(BaTiO3)n ferroelectric superlattices was computed using the phase-field approach as a function of layer volume fraction and biaxial strain to tune ferroelectric properties through domain engineering. Two interesting domain structures are found: one with mixed Bloch-Néel-Ising domain wall structures and the other with stabilized monoclinic phases. The polarization of the monoclinic phase is able to rotate from out-of-plane to in-plane or vice versa under an electric field, and thus facilitates the domain reversal of rhombohedral domains. This contributes significantly to both reduced coercive fields and enhanced piezoelectric responses.

  9. Acoustic gain in piezoelectric semiconductors at ɛ-near-zero response

    NASA Astrophysics Data System (ADS)

    Willatzen, M.; Christensen, J.

    2014-01-01

    We demonstrate strong acoustic gain in electric-field biased piezoelectric semiconductors at frequencies near the plasmon frequency in the terahertz range. When the electron drift velocity produced by an external electric field is higher than the speed of sound, Cherenkov radiation of phonons generates amplification of sound. It is demonstrated that this effect is particularly effective at ɛ-near-zero response, leading to giant levels of acoustic gain. Operating at conditions with strong acoustic amplification, we predict unprecedented enhancement of the scattered sound field radiated from an electrically controlled piezoelectric slab waveguide. This extreme sound field enhancement in an active piezo material shows potential for acoustic sensing and loss compensation in metamaterials and nonlinear devices.

  10. New strategy for enhancing in situ cell viability of cell-printing process via piezoelectric transducer-assisted three-dimensional printing.

    PubMed

    Koo, YoungWon; Kim, GeunHyung

    2016-05-20

    Tissue engineering has become one of the great applications of three-dimensional cell printing because of the possibility of fabricating complex cell-laden scaffolds. Three typical methods (inkjet, micro-extrusion, and laser-assisted bio-printing) have been used to fabricate structures. Of these, micro-extrusion is a comparatively easy method, but has some drawbacks such as low in situ cell viability after fabricating cell-laden structures because of the high wall shear stress in micro-sized nozzles. To overcome this shortcoming, we suggest an innovative cell printing method, which is assisted by a piezoelectric transducer (PZT). The PZT assistance in the dispensing process enhances the printing efficiency and cell viability by decreasing the wall shear stress within a nozzle because the PZT effect can lower the shear viscosity of the bioink via micro-scale vibration. In this study, 5 wt% cell-laden alginate was used as a bioink, and various PZT conditions (frequencies up to ∼400 Hz and amplitudes up to ∼40.5 μm) were simultaneously applied to the cell-printing process to examine the effectiveness of the PZT. The PZT-assisted cell-printing method was found to be highly effective in direct cell printing and could achieve cell-laden structures with high in situ cell viability.

  11. A piezoelectric pseudo-bimorph actuator

    NASA Astrophysics Data System (ADS)

    Shi, Huaduo; Chen, Jianguo; Liu, Guoxi; Xiao, Wenlei; Dong, Shuxiang

    2013-06-01

    We report a piezoelectric pseudo-bimorph actuator, which is made of only one single plate with interdigitated electrodes on both sides and polarized alternately in longitudinal direction. Like a bimorph actuator, it can also produce a large bending actuation based on anti-symmetrically longitudinal piezoelectric d33 strain effect under an applied electric field. The presented pseudo-bimorph actuator shows much better temperature stability than conventional piezoelectric bimorph actuators from room temperature to the depolarization temperature of the material due to lacking of interface strain loss.

  12. Silicon/Carbon Nanotube/BaTiO₃ Nanocomposite Anode: Evidence for Enhanced Lithium-Ion Mobility Induced by the Local Piezoelectric Potential.

    PubMed

    Lee, Byoung-Sun; Yoon, Jihyun; Jung, Changhoon; Kim, Dong Young; Jeon, Seung-Yeol; Kim, Ki-Hong; Park, Jun-Ho; Park, Hosang; Lee, Kang Hee; Kang, Yoon-Sok; Park, Jin-Hwan; Jung, Heechul; Yu, Woong-Ryeol; Doo, Seok-Gwang

    2016-02-23

    We report on the synergetic effects of silicon (Si) and BaTiO3 (BTO) for applications as the anode of Li-ion batteries. The large expansion of Si during lithiation was exploited as an energy source via piezoelectric BTO nanoparticles. Si and BTO nanoparticles were dispersed in a matrix consisting of multiwalled carbon nanotubes (CNTs) using a high-energy ball-milling process. The mechanical stress resulting from the expansion of Si was transferred via the CNT matrix to the BTO, which can be poled, so that a piezoelectric potential is generated. We found that this local piezoelectric potential can improve the electrochemical performance of the Si/CNT/BTO nanocomposite anodes. Experimental measurements and simulation results support the increased mobility of Li-ions due to the local piezoelectric potential.

  13. Performance of a novel piezoelectric motor at 4.7 T: applications and initial tests.

    PubMed

    Turowski, Steven G; Seshadri, Mukund; Loecher, Michael; Podniesinski, Edward; Spernyak, Joseph A; Mazurchuk, Richard V

    2008-04-01

    The focus of this report was to test the performance of a novel piezoelectric motor under high magnetic field strength conditions and to investigate its potential applications in small animal magnetic resonance imaging (MRI). The device is made entirely of nonferrous materials and consists of four piezoelectric ceramic plates connected to a threaded metal tube through which a screw migrates. Ultrasonic vibrations of the threads inherent to the tube result in rotational and translational motion of the screw. Potential applications of the piezoelectric motor were investigated at 4.7 T. Firstly, phantom studies showed the motor was capable of accurately delivering low injection volumes ( approximately 0.01 ml). Dynamic contrast-enhanced MRI (DCE-MRI) studies performed in vivo using serially acquired T1-weighted, spin-echo imaging demonstrated the ability of the motor to reliably administer MR contrast-enhancing agent into live tumor-bearing mice without the introduction of image artifacts. In a second set of experiments, the motor allowed for controlled, dynamic repositioning of an anatomic slice of interest in a live animal to magnetic field isocenter, which resulted in reduced geometric distortion and image artifact due to improved radiofrequency and gradient field homogeneity. In conclusion, piezoelectric motors are MR compatible and offer great potential for improving MRI efficiency and throughput, particularly in a preclinical setting. Further investigation into applications such as automated capacitor tuning and impedance matching for MR transceiver coils is warranted.

  14. Optical fiber tip for field-enhanced second harmonic generation.

    PubMed

    Pal, Sudipta Sarkar; Mondal, Samir K; Bajpai, Phun Phun; Kapur, Pawan

    2012-10-01

    We propose a simple optical fiber tip for field-enhanced second harmonic generation (SHG). The tip shows nonlinear phenomena of SHG over a wide range of sources, at least from 630 to 830 nm. The optical field corresponding to the second harmonic appears as a nondiffracting bottle beam with voids due to the surface curvature of the tip. The field-enhanced second harmonic can also induce surface plasmons, converting the tip to a plasmonic probe with reduced background signal. The tip can be useful in nanophotonics characterization. As an example, we demonstrate the tip's response as a surface-enhanced Raman spectroscopy probe.

  15. Numerical simulation of piezoelectric effect under ultrasound irradiation with consideration of conductivity

    NASA Astrophysics Data System (ADS)

    Hosokawa, Atsushi

    2016-07-01

    Using a piezoelectric finite-difference time-domain (PE-FDTD) method, numerical simulation of the piezoelectric effect under ultrasound irradiation was performed considering conductivity. From the simulated results, it was shown that the ultrasound amplitude in piezoelectric ceramics decreased owing to piezoelectricity with the increase in conductivity. The simulated ultrasound waveform at a low conductivity agreed with the experimental waveform. The electric field induced in the ceramics decreased with conductivity, and the electric field at a high conductivity decreased with time, which represented piezoelectric relaxation. Moreover, the effect of conductivity on piezoelectricity in human cortical bone was investigated.

  16. Piezoelectric field effect on the optical properties of In0.21Ga0.79As/GaAs (113) MQW

    NASA Astrophysics Data System (ADS)

    Fraj, Ibtissem; Saidi, Faouzi; Bouzaiene, Lotfi; Sfaxi, Larbi; Maaref, Hassen

    2016-08-01

    Photoluminescence study PL has been performed for the In0.21Ga0.79As multiple quantum wells MQW grown by molecular beam epitaxy MBE on (001) and (113) A GaAs substrates. The electronic structure was obtained by solving the Schrödinger equation, including piezoelectric field and strain effect on the conduction and valence bands of the unequal QWs. We critically review the explanation of S-shape in temperature dependence of PL peak energy for polar Middle In0.21Ga0.79As QW at intermediate temperatures. This abnormal behavior is merely linked to the impact of carrier localization and polarization-induced electric fields in optical properties. A significant blue shift of 18 meV for polar and a negligible shift for non-polar In0.21Ga0.79As/GaAs Middle QW has been observed. In order to follow the evolution of the PL peak energies for each QW in both samples versus temperature, three theoretical models (Varshni, Vïna and Pässler) have been reported. A comparison between theoretical and experimental data demonstrates that the Pässler model is the most accurate fit despite none of the classical models can replicate the excitonic PL energy evolution at cryogenic temperature for Middle QW in the structure grown on (113).

  17. On the Binding Stress-Enhanced Sensitivity of (Pb(Mg1/3Nb2/3)O3)0.65-(PbTiO3) 0.35 (PMN-PT) Piezoelectric Plate Sensor (PEPS)

    NASA Astrophysics Data System (ADS)

    Wu, Wei

    (Pb(Mg1/3Nb2/3)O3)0.65-(PbTiO 3)0.35 (PMN-PT) piezoelectric plate sensor (PEPS) showed enhanced sensitivity in chemical and biological sensing applications which has been attributed to binding-induced crystalline orientation switching in the PMN-PT layer. However, so far there has been no direct demonstration of PEPS crystalline orientation switching upon target-analyte binding. Using biotin and streptavidin binding as a model detection system and by direct X-Ray diffraction observations after analyte binding we have unambiguously demonstrated that switching of the crystalline orientations of the PMN-PT layer indeed occurred. In addition, we have shown that PEPS sensitivity enhancement increased with an increasing transverse electromechanical coupling constant, -k31, of the PMN-PT layer--which is known to correlate with the crystalline orientation switching capability--by increasing the grain size of the PMN-PT layer or by applying a DC bias electric field. Finally, unprecedented high sensitivity of PEPS with high -k31, (i.e., -k31 > 0.3) were illustrated by the aM (10-18 M) sensitivity of in situ DNA hybridization detection without amplification and by the 100 fg/ml (10-13 g/ml) sensitivity of rapid, in situ protein detection in biological fluids such as troponin I detection in serum for early sign of myocardial infarction (heart attack), Her2 detection in serum for cancer treatment and monitoring, Tn antigen and anti-Tn antibody detection in serum for early cancer detection, and Toxins detection in stool for Clostridium difficile infection detection.

  18. Edge enhancement control in linear arrays of ungated field emitters

    NASA Astrophysics Data System (ADS)

    Harris, J. R.; Jensen, K. L.; Shiffler, D. A.

    2016-01-01

    In arrays of ungated field emitters, the field enhancement factor of each emitter decreases as the distance between the emitters decreases, an effect known as screening. At the edge of these arrays, emitters experience reduced screening, leading to higher field enhancement factors than emitters at the array center, causing nonuniform emission across the array. Here, we consider this effect in linear arrays of ungated field emitters spaced at distances comparable to their heights, which is the regime that generally maximizes their average current density. A Line Charge Model is used to assess the degree to which these edge effects propagate into the array interior, and to study the impact of varying the height, location, and tip radius of emitters at the ends of an array on the edge enhancement. It is shown that each of these techniques can accomplish this edge enhancement control, but each has advantages and disadvantages that will be discussed.

  19. Enhanced Fair-Weather Electric Fields Soon After Sunrise

    NASA Technical Reports Server (NTRS)

    Marshall, T. C.; Rust, W. D.; Stolzenburg, M.; Roeder, W.; Krehbiel, P. R.

    1999-01-01

    The typical fair weather electric field at the ground is between -100 and -300 V/m. At the NASA Kennedy Space Center and US Air Force Cape Canaveral Air Station (KSC) the electric field at the ground sometimes reaches -400 to -1200 V/m within an hour or two after sunrise on days that otherwise seem to be fair weather. We refer to the enhanced negative electric fields as the "sunrise enhancement." To investigate the sunrise enhancement at KSC we measured the electric field (E) in the first few hundred meters above the ground before and during several sunrise enhancements. From these E soundings we can infer the presence of charge layers and determine their thickness and charge density.

  20. Large optical field enhancement for nanotips with large opening angles

    NASA Astrophysics Data System (ADS)

    Thomas, Sebastian; Wachter, Georg; Lemell, Christoph; Burgdörfer, Joachim; Hommelhoff, Peter

    2015-06-01

    We theoretically investigate the dependence of the enhancement of optical near-fields at nanometric tips on the shape, size, and material of the tip. We confirm the strong dependence of the field enhancement factor on the radius of curvature. In addition, we find a surprisingly strong increase of field enhancement with increasing opening angle of the nanotips. For gold and tungsten nanotips in the experimentally relevant parameter range (radius of curvature ≥slant 5 nm at 800 nm laser wavelength), we obtain field enhancement factors of up to ∼ 35 for Au and ∼ 12 for W for large opening angles. We confirm this strong dependence on the opening angle for many other materials featuring a wide variety in their dielectric response. For dielectrics, the opening angle dependence is traced back to the electrostatic force of the induced surface charge at the tip shank. For metals, the plasmonic response strongly increases the field enhancement and shifts the maximum field enhancement to smaller opening angles.

  1. A piezoelectric transformer

    NASA Technical Reports Server (NTRS)

    Won, C. C.

    1993-01-01

    This work describes a modeling and design method whereby a piezoelectric system is formulated by two sets of second-order equations, one for the mechanical system, and the other for the electrical system, coupled through the piezoelectric effect. The solution to this electromechanical coupled system gives a physical interpretation of the piezoelectric effect as a piezoelectric transformer that is a part of the piezoelectric system, which transfers the applied mechanical force into a force-controlled current source, and short circuit mechanical compliance into capacitance. It also transfers the voltage source into a voltage-controlled relative velocity input, and free motional capacitance into mechanical compliance. The formulation and interpretation simplify the modeling of smart structures and lead to physical insight that aids the designer. Due to its physical realization, the smart structural system can be unconditional stable and effectively control responses. This new concept has been demonstrated in three numerical examples for a simple piezoelectric system.

  2. Micromachined Piezoelectric Microspeaker

    NASA Astrophysics Data System (ADS)

    Yi, Seung Hwan; Kim, Eun Sok

    2005-06-01

    A diaphragm-based piezoelectric microspeaker is fabricated on a heavily compressive silicon-nitride film, and is compared to commercial speakers. The largest sound pressure level (SPL) produced by the fabricated microspeaker is 92 dB (when measured 2 mm away from the microspeaker in open field) at around 3 kHz for 6 Vpeak-to-peak input. The microspeaker produces a comparable sound output as a commercial piezo-ceramic and electro-dynamic speaker used in current cellular phones. The keys to this success are as follows: (1) the usage of a diaphragm that has a very high compressive residual stress, high enough to cause the diaphragm to be wrinkled and (2) the usage of high quality ZnO film deposited by two-step deposition technique.

  3. Surface effects on vibration analysis of elastically restrained piezoelectric nanobeams subjected to magneto-thermo-electrical field embedded in elastic medium

    NASA Astrophysics Data System (ADS)

    Marzbanrad, Javad; Boreiry, Mahya; Shaghaghi, Gholam Reza

    2017-04-01

    In the present study, a generalized nonlocal beam theory is utilized to study the magneto-thermo-mechanical vibration characteristic of piezoelectric nanobeam by considering surface effects rested in elastic medium for various elastic boundary conditions. The nonlocal elasticity of Eringen as well as surface effects, including surface elasticity, surface stress and surface density are implemented to inject size-dependent effects into equations. Using the Hamilton's principle and Euler-Bernoulli beam theory, the governing differential equations and associated boundary conditions will be obtained. The differential transformation method (DTM) is used to discretize resultant motion equations and related boundary conditions accordingly. The natural frequencies are obtained for the various elastic boundary conditions in detail to show the significance of nonlocal parameter, external voltage, temperature change, surface effects, elastic medium, magnetic field and length of nanobeam. Moreover, it should be noted that by changing the spring stiffness at each end, the conventional boundary conditions will be obtained which are validated by well-known literature.

  4. Circuit for Driving Piezoelectric Transducers

    NASA Technical Reports Server (NTRS)

    Randall, David P.; Chapsky, Jacob

    2009-01-01

    The figure schematically depicts an oscillator circuit for driving a piezoelectric transducer to excite vibrations in a mechanical structure. The circuit was designed and built to satisfy application-specific requirements to drive a selected one of 16 such transducers at a regulated amplitude and frequency chosen to optimize the amount of work performed by the transducer and to compensate for both (1) temporal variations of the resonance frequency and damping time of each transducer and (2) initially unknown differences among the resonance frequencies and damping times of different transducers. In other words, the circuit is designed to adjust itself to optimize the performance of whichever transducer is selected at any given time. The basic design concept may be adaptable to other applications that involve the use of piezoelectric transducers in ultrasonic cleaners and other apparatuses in which high-frequency mechanical drives are utilized. This circuit includes three resistor-capacitor networks that, together with the selected piezoelectric transducer, constitute a band-pass filter having a peak response at a frequency of about 2 kHz, which is approximately the resonance frequency of the piezoelectric transducers. Gain for generating oscillations is provided by a power hybrid operational amplifier (U1). A junction field-effect transistor (Q1) in combination with a resistor (R4) is used as a voltage-variable resistor to control the magnitude of the oscillation. The voltage-variable resistor is part of a feedback control loop: Part of the output of the oscillator is rectified and filtered for use as a slow negative feedback to the gate of Q1 to keep the output amplitude constant. The response of this control loop is much slower than 2 kHz and, therefore, does not introduce significant distortion of the oscillator output, which is a fairly clean sine wave. The positive AC feedback needed to sustain oscillations is derived from sampling the current through the

  5. Piezoelectric devices for generating low power

    NASA Astrophysics Data System (ADS)

    Chilibon, Irinela

    2016-12-01

    This paper reviews concepts and applications in low-power electronics and energy harvesting technologies. Various piezoelectric materials and devices for small power generators useful in renewable electricity are presented. The vibrating piezoelectric device differs from the typical electrical power source in that it has capacitive rather than inductive source impedance, and may be driven by mechanical vibrations of varying amplitude. In general, vibration energy could be converted into electrical energy using one of three techniques: electrostatic charge, magnetic fields and piezoelectric. A low power piezoelectric generator, having a PZT element was realised in order to supply small electronic elements, such as optoelectronic small devices, LEDs, electronic watches, small sensors, interferometry with lasers or Micro-electro-mechanical System (MEMS) array with multi-cantilevers.

  6. Development of Piezoelectric Zinc Oxide Nanoparticle-Poly(Vinylidene Fluoride) Nanocomposites for Sensing and Actuation

    NASA Astrophysics Data System (ADS)

    Dodds, John Steven

    Structural health monitoring (SHM) is vital for detecting the onset of damage and for preventing catastrophic failure of civil infrastructure systems. In particular, piezoelectric transducers have the ability to excite and actively interrogate structures (e.g., using surface waves) while measuring their response for damage detection. In fact, piezoelectric transducers such as lead zirconate titanate (PZT) and poly(vinylidene fluoride) (PVDF) have been used for various laboratory and field tests and have demonstrated significant advantages as compared to visual inspection and vibration-based methods, to name a few. However, PZTs are inherently brittle, and PVDF films do not possess high piezoelectricity, thereby limiting each of these devices to certain specific applications. Piezoelectric nanocomposites, which enjoy a combination of the best properties of these material types, are at the forefront of emerging SHM technologies. The objective of this study is to design, characterize, and validate piezoelectric nanocomposites consisting of zinc oxide (ZnO) nanoparticles assembled in a PVDF copolymer matrix for sensing and actuation. It will be shown that these films provide greater mechanical flexibility as compared to PZTs, yet possess enhanced piezoelectricity as compared to pristine PVDF copolymers. The results obtained from this research will be crucial for future SHM applications using these piezoelectric nanocomposites. This study began with spin coating dispersed ZnO-based solutions for piezoelectric nanocomposite fabrication. The concentration of ZnO nanoparticles was varied from 0 to 20 wt.% (in 5% increments) to determine their influence on bulk film piezoelectricity. Second, their electric polarization responses were obtained for quantifying thin film remnant polarization, which is directly correlated to piezoelectricity. Based on these results, the films were poled at 50 MV-m-1 to permanently align film electrical domains and to enhance bulk film

  7. Structure-Property Study of Piezoelectricity in Polyimides

    NASA Technical Reports Server (NTRS)

    Ounaies, Zoubeida; Park, Cheol; Harrison, Joycelyn S.; Smith, Joseph G.; Hinkley, Jeffrey

    1999-01-01

    High performance piezoelectric polymers are of interest to NASA as they may be useful for a variety of sensor applications. Over the past few years research on piezoelectric polymers has led to the development of promising high temperature piezoelectric responses in some novel polyimides. In this study, a series of polyimides have been studied with systematic variations in the diamine monomers that comprise the polyimide while holding the dianhydride constant. The effect of structural changes, including variations in the nature and concentration of dipolar groups, on the remanent polarization and piezoelectric coefficient is examined. Fundamental structure-piezoelectric property insight will enable the molecular design of polymers possessing distinct improvements over state-of-the-art piezoelectric polymers including enhanced polarization, polarization stability at elevated temperatures, and improved processability.

  8. Effect of material uncertainties on dynamic analysis of piezoelectric fans

    NASA Astrophysics Data System (ADS)

    Srivastava, Swapnil; Yadav, Shubham Kumar; Mukherjee, Sujoy

    2015-04-01

    A piezofan is a resonant device that uses a piezoceramic material to induce oscillations in a cantilever beam. In this study, lumped-mass modelling is used to analyze a piezoelectric fan. Uncertainties are associated with the piezoelectric structures due to several reasons such as variation during manufacturing process, temperature, presence of adhesive layer between the piezoelectric actuator/sensor and the shim stock etc. Presence of uncertainty in the piezoelectric materials can influence the dynamic behavior of the piezoelectric fan such as natural frequency, tip deflection etc. Moreover, these quantities will also affect the performance parameters of the piezoelectric fan. Uncertainty analysis is performed using classical Monte Carlo Simulation (MCS). It is found that the propagation of uncertainty causes significant deviations from the baseline deterministic predictions, which also affect the achievable performance of the piezofan. The numerical results in this paper provide useful bounds on several performance parameters of the cooling fan and will enhance confidence in the design process.

  9. Surface plasmon field enhancements in deterministic aperiodic structures.

    PubMed

    Shugayev, Roman

    2010-11-22

    In this paper we analyze optical properties and plasmonic field enhancements in large aperiodic nanostructures. We introduce extension of Generalized Ohm's Law approach to estimate electromagnetic properties of Fibonacci, Rudin-Shapiro, cluster-cluster aggregate and random deterministic clusters. Our results suggest that deterministic aperiodic structures produce field enhancements comparable to random morphologies while offering better understanding of field localizations and improved substrate design controllability. Generalized Ohm's law results for deterministic aperiodic structures are in good agreement with simulations obtained using discrete dipole method.

  10. Analysis on enhanced depth of field for integral imaging microscope.

    PubMed

    Lim, Young-Tae; Park, Jae-Hyeung; Kwon, Ki-Chul; Kim, Nam

    2012-10-08

    Depth of field of the integral imaging microscope is studied. In the integral imaging microscope, 3-D information is encoded as a form of elemental images Distance between intermediate plane and object point decides the number of elemental image and depth of field of integral imaging microscope. From the analysis, it is found that depth of field of the reconstructed depth plane image by computational integral imaging reconstruction is longer than depth of field of optical microscope. From analyzed relationship, experiment using integral imaging microscopy and conventional microscopy is also performed to confirm enhanced depth of field of integral imaging microscopy.

  11. Formation of Enhanced Uniform Chiral Fields in Symmetric Dimer Nanostructures

    NASA Astrophysics Data System (ADS)

    Tian, Xiaorui; Fang, Yurui; Sun, Mengtao

    2015-12-01

    Chiral fields with large optical chirality are very important in chiral molecules analysis, sensing and other measurements. Plasmonic nanostructures have been proposed to realize such super chiral fields for enhancing weak chiral signals. However, most of them cannot provide uniform chiral near-fields close to the structures, which makes these nanostructures not so efficient for applications. Plasmonic helical nanostructures and blocked squares have been proved to provide uniform chiral near-fields, but structure fabrication is a challenge. In this paper, we show that very simple plasmonic dimer structures can provide uniform chiral fields in the gaps with large enhancement of both near electric fields and chiral fields under linearly polarized light illumination with polarization off the dimer axis at dipole resonance. An analytical dipole model is utilized to explain this behavior theoretically. 30 times of volume averaged chiral field enhancement is gotten in the whole gap. Chiral fields with opposite handedness can be obtained simply by changing the polarization to the other side of the dimer axis. It is especially useful in Raman optical activity measurement and chiral sensing of small quantity of chiral molecule.

  12. Formation of Enhanced Uniform Chiral Fields in Symmetric Dimer Nanostructures

    PubMed Central

    Tian, Xiaorui; Fang, Yurui; Sun, Mengtao

    2015-01-01

    Chiral fields with large optical chirality are very important in chiral molecules analysis, sensing and other measurements. Plasmonic nanostructures have been proposed to realize such super chiral fields for enhancing weak chiral signals. However, most of them cannot provide uniform chiral near-fields close to the structures, which makes these nanostructures not so efficient for applications. Plasmonic helical nanostructures and blocked squares have been proved to provide uniform chiral near-fields, but structure fabrication is a challenge. In this paper, we show that very simple plasmonic dimer structures can provide uniform chiral fields in the gaps with large enhancement of both near electric fields and chiral fields under linearly polarized light illumination with polarization off the dimer axis at dipole resonance. An analytical dipole model is utilized to explain this behavior theoretically. 30 times of volume averaged chiral field enhancement is gotten in the whole gap. Chiral fields with opposite handedness can be obtained simply by changing the polarization to the other side of the dimer axis. It is especially useful in Raman optical activity measurement and chiral sensing of small quantity of chiral molecule. PMID:26621558

  13. Formation of Enhanced Uniform Chiral Fields in Symmetric Dimer Nanostructures.

    PubMed

    Tian, Xiaorui; Fang, Yurui; Sun, Mengtao

    2015-12-01

    Chiral fields with large optical chirality are very important in chiral molecules analysis, sensing and other measurements. Plasmonic nanostructures have been proposed to realize such super chiral fields for enhancing weak chiral signals. However, most of them cannot provide uniform chiral near-fields close to the structures, which makes these nanostructures not so efficient for applications. Plasmonic helical nanostructures and blocked squares have been proved to provide uniform chiral near-fields, but structure fabrication is a challenge. In this paper, we show that very simple plasmonic dimer structures can provide uniform chiral fields in the gaps with large enhancement of both near electric fields and chiral fields under linearly polarized light illumination with polarization off the dimer axis at dipole resonance. An analytical dipole model is utilized to explain this behavior theoretically. 30 times of volume averaged chiral field enhancement is gotten in the whole gap. Chiral fields with opposite handedness can be obtained simply by changing the polarization to the other side of the dimer axis. It is especially useful in Raman optical activity measurement and chiral sensing of small quantity of chiral molecule.

  14. Surface modification of piezoelectric aluminum nitride with functionalizable organosilane adlayers

    NASA Astrophysics Data System (ADS)

    Chan, Edmund; Jackson, Nathan; Mathewson, Alan; Galvin, Paul; Alamin Dow, Ali B.; Kherani, Nazir P.; Blaszykowski, Christophe; Thompson, Michael

    2013-10-01

    The world of biosensors is expanding at a rapid pace with an ever-increasing demand for more sensitive miniaturized devices. Acoustic wave biosensors are not spared from this trend. In this domain, the search for enhanced sensitivity is increasingly oriented toward the rational design of new piezoelectric materials with superior properties to substitute for prevalent quartz. With respect to surface chemistry, construction of the biorecognition element, more often than not, requires the use of bifunctional molecules that can spontaneously assemble on the substrate and form organic surfaces readily biofunctionalizable in a subsequent, ideally single step. In this context, we present herein the surface modification of aluminum nitride (AlN) with alkyltrichlorosilane cross-linking molecules bearing a functionalizable benzenethiosulfonate moiety. This latter feature is next demonstrated through the straightforward, preactivation-free immobilization of thiolated biotin probes. To date, AlN has only received little attention in the field of piezoelectric biosensors despite its many attractive properties and the perspective to operate devices at ultra-high frequencies (GHz) with unprecedented sensitivity. To our knowledge, this work describes one of the first examples of direct surface derivatization of AlN with bifunctional trichlorosilane molecules. It also constitutes a first step toward the development of electrodeless GHz piezoelectric biosensing platforms based on AlN and trichlorosilane surface chemistry.

  15. Analytic Optimization of Near-Field Optical Chirality Enhancement

    PubMed Central

    2017-01-01

    We present an analytic derivation for the enhancement of local optical chirality in the near field of plasmonic nanostructures by tuning the far-field polarization of external light. We illustrate the results by means of simulations with an achiral and a chiral nanostructure assembly and demonstrate that local optical chirality is significantly enhanced with respect to circular polarization in free space. The optimal external far-field polarizations are different from both circular and linear. Symmetry properties of the nanostructure can be exploited to determine whether the optimal far-field polarization is circular. Furthermore, the optimal far-field polarization depends on the frequency, which results in complex-shaped laser pulses for broadband optimization. PMID:28239617

  16. A wave-shaped hybrid piezoelectric and triboelectric nanogenerator based on P(VDF-TrFE) nanofibers.

    PubMed

    Chen, Xuexian; Han, Mengdi; Chen, Haotian; Cheng, Xiaoliang; Song, Yu; Su, Zongming; Jiang, Yonggang; Zhang, Haixia

    2017-01-19

    A wave-shaped hybrid nanogenerator (NG) with mutually enhanced piezoelectric and triboelectric output is presented in this work. By sandwiching piezoelectric P(VDF-TrFE) nanofibers between wave-shaped Kapton films, the device forms a three-layer structure, which can generate piezoelectric and triboelectric outputs simultaneously in one press and release cycle. Through systematic situational analysis and experimental validation, the three-layer structure can achieve obvious improvement of the output performance for both parts. When triggered with 4 Hz external force, the piezoelectric part generates a peak output and current of 96 V and 3.8 μA, which is ∼2 times higher than its initial output. Meanwhile, the performance of triboelectric parts also increases 8 V and 16 V with the assistance of piezoelectric potential. The enhanced high output enables the hybrid nanogenerator to instantaneously light up LEDs and charges capacitors quickly, which shows extensive application prospects in the field of self-powered systems or sensor networks.

  17. Enormous enhancement of electric field in active gold nanoshells

    NASA Astrophysics Data System (ADS)

    Jiang, Shu-Min; Wu, Da-Jian; Wu, Xue-Wei; Liu, Xiao-Jun

    2014-04-01

    The electric field enhancement properties of an active gold nanoshell with gain material inside have been investigated by using Mie theory. As the gain coefficient of the inner core increases to a critical value, a super-resonance appears in the active gold nanoshell, and enormous enhancements of the electric fields can be found near the surface of the particle. With increasing shell thickness, the critical value of the gain coefficient for the super-resonance of the active gold nanoshell first decreases and then increases, and the corresponding surface enhanced Raman scattering (SERS) enhancement factor (G factor) also first increases and then decreases. The optimized active gold nanoshell can be obtained with an extremely high SERS G factor of the order of 1019-1020. Such an optimized active gold nanoshell possesses a high-efficiency SERS effect and may be useful for single-molecule detection.

  18. Role of enhanced laser field in laser processing of nanomaterials

    NASA Astrophysics Data System (ADS)

    Zhang, Tao; Kuk, Seungkuk; Kim, Eunpa; Grigoropoulos, Costas P.; Hwang, David J.

    2016-03-01

    Lasers have proven to be unique tools for a highly selective processing of nanomaterials system on the basis of the enhanced laser field, maintaining other sensitive portion in the system untouched. However, in many practical applications, a wide interspacing distribution among nanomaterials and nonlinear laser absorption properties of the nanomaterials in the highly excited nanomaterials states, frequently lead to rather adverse effects in terms of controlled nanomaterials processing. In this study, we will take a few laser nanomaterials processing examples mainly based on the nanowires system including the spin coated metallic nanowires for transparent electrode applications and selective semiconductor nanowires growth from the metallic nanocatalysts, and discuss on the role of the enhanced laser field via the combined theoretical and experimental investigations. Specific aims of properly utilizing the enhanced laser fields are to achieve improved electrical conductance for practical transparent electrode applications, and to facilitate directed growth of semiconductor nanowires at designated sample locations, respectively.

  19. Nonresonant 104 Terahertz Field Enhancement with 5-nm Slits

    PubMed Central

    Suwal, Om Krishna; Rhie, Jiyeah; Kim, Nayeon; Kim, Dai-Sik

    2017-01-01

    Transmission of Terahertz (THz) electromagnetic wave through a substrate is encumbered because of scattering, multiple reflections, absorption, and Fabry–Perot effects when the wave interacts with the substrate. We present the experimental realization of nonresonant electromagnetic field enhancement by a factor of almost 104 in substrate-free 5-nm gold nanoslits. Our nanoslits yielded greater than 90% normalized electric field transmission in the low-frequency THz region; the slit width was 5 nm, and the gap coverage ratio was 10−4 of the entire membrane, 0.42 mm2. This large field enhancement was attributed to gap plasmons generated by the THz wave, which squeezes the charge cross-section, thus enabling very highly dense oscillating charges and strong THz field transmission from the nanoslits. PMID:28368048

  20. Application of Terahertz Field Enhancement Effect in Metal Microstructures

    NASA Astrophysics Data System (ADS)

    Nakajima, M.; Kurihara, T.; Tadokoro, Y.; Kang, B.; Takano, K.; Yamaguchi, K.; Watanabe, H.; Oto, K.; Suemoto, T.; Hangyo, M.

    2016-12-01

    Applications of high-field terahertz pulses are attractive in physics and terahertz technology. In this study, two applications related to high-intensity terahertz pulses are demonstrated. The field enhancement effect by subwavelength metallic microstructures is utilized for terahertz excitation measurement. The spin precession dynamics in magnetic materials was induced by a terahertz magnetic field. Spin precession was amplified by one order of magnitude in amplitude by the enhanced magnetic terahertz field in orthoferrite ErFeO3 with metal microstructures. The induced spin dynamics was analyzed and explained by LLG-LCR model. Moreover, a detection method for terahertz pulses was developed using a cholesteric liquid crystal at room temperature without any electronic devices. The beam profile of terahertz pulses was visualized and compared to other methods such as the knife edge method using pyroelectric detector and micro-bolometer array. The liquid crystal terahertz imager is very simple and has good applicability as a portable terahertz-sensing card.

  1. Surfactant-enhanced alkaline flooding field project. Annual report, Revision

    SciTech Connect

    French, T.R.

    1991-10-01

    The Tucker sand of Helper (KS) field is a candidate for surfactant-enhanced alkaline flooding. The geology of the Helper site is typical of many DOE Class I reservoirs. The Tucker sand of Helper field was deposited in a fluvial dominated deltaic environment. Helper oil can be mobilized with either chemical system 2 or chemical system 3, as described in this report. Oil fields in the Gulf Coast region are also good candidates for surfactant-enhanced alkaline flooding. The results from laboratory tests conducted in Berea sandstone cores with oil brine from Helper (KS) field are encouraging. The crude oil is viscous and non-acidic and, yet, was mobilized by the chemical formulations described in this report. Significant amounts of the oil were mobilized under simulated reservoir conditions. The results in Berea sandstone cores were encouraging and should be verified by tests with field core. Consumption of alkali, measured with field core, was very low. Surfactant loss appeared to be acceptable. Despite the good potential for mobilization of Helper oil, certain reservoir characteristics such as low permeability, compartmentalization, and shallow depth place constraints on applications of any chemical system in the Tucker sand. These constraints are typical of many DOE Class I reservoirs. Although Hepler field is not a perfect reservoir in which to apply surfactant- enhanced alkaline flooding, Hepler oil is particularly amenable to mobilization by surfactant-enhanced alkaline systems. A field test is recommended, dependent upon final evaluation of well logs and cores from the proposed pilot area. 14 refs., 21 figs., 10 tabs.

  2. Dielectrically induced sensitivity enhancements in electro-optic field sensors

    NASA Astrophysics Data System (ADS)

    Garzarella, A.; Qadri, S. B.; Wieting, Terence J.; Wu, Dong Ho; Hinton, R. J.

    2007-04-01

    The sensitivity of an electro-optic (EO) field sensor depends inversely on the dielectric constant of the nonlinear crystal. In EO sensors based on lithium niobate the effective value of this dielectric constant is affected by dielectric relaxation effects and is identified with its smaller, high-frequency component. Because of this effect, the EO modulation is significantly enhanced, thus improving the field strength sensitivity.

  3. Enhanced proton acceleration in an applied longitudinal magnetic field

    NASA Astrophysics Data System (ADS)

    Arefiev, A.; Toncian, T.; Fiksel, G.

    2016-10-01

    Using two-dimensional particle-in-cell simulations, we examine how an externally applied strong magnetic field impacts proton acceleration in laser-irradiated solid-density targets. We find that a kT-level external magnetic field can sufficiently inhibit transverse transport of hot electrons in a flat laser-irradiated target. While the electron heating by the laser remains mostly unaffected, the reduced electron transport during proton acceleration leads to an enhancement of maximum proton energies and the overall number of energetic protons. The resulting proton beam is much better collimated compared to a beam generated without applying a kT-level magnetic field. A factor of three enhancement of the laser energy conversion efficiency into multi-MeV protons is another effect of the magnetic field. The required kT-level magnetic fields are becoming feasible due to a significant progress that has been made in generating magnetic fields with laser-driven coils using ns-long laser pulses. The possibility of improving characteristics of laser-driven proton beams using such fields is a strong motivation for further development of laser-driven magnetic field capabilities.

  4. Optical and mechanical detection of near-field light by atomic force microscopy using a piezoelectric cantilever

    NASA Astrophysics Data System (ADS)

    Satoh, Nobuo; Kobayashi, Kei; Watanabe, Shunji; Fujii, Toru; Matsushige, Kazumi; Yamada, Hirofumi

    2016-08-01

    In this study, we developed an atomic force microscopy (AFM) system with scanning near-field optical microscopy (SNOM) using a microfabricated force-sensing cantilever with a lead zirconate titanate (PZT) thin film. Both optical and mechanical detection techniques were adopted in SNOM to detect scattered light induced by the interaction of the PZT cantilever tip apex and evanescent light, and SNOM images were obtained for each detection scheme. The mechanical detection technique did allow for a clear observation of the light scattered from the PZT cantilever without the interference observed by the optical detection technique, which used an objective lens, a pinhole, and a photomultiplier tube.

  5. Additional Enhancement of Electric Field in Surface-Enhanced Raman Scattering due to Fresnel Mechanism

    NASA Astrophysics Data System (ADS)

    Jayawardhana, Sasani; Rosa, Lorenzo; Juodkazis, Saulius; Stoddart, Paul R.

    2013-08-01

    Surface-enhanced Raman scattering (SERS) is attracting increasing interest for chemical sensing, surface science research and as an intriguing challenge in nanoscale plasmonic engineering. Several studies have shown that SERS intensities are increased when metal island film substrates are excited through a transparent base material, rather than directly through air. However, to our knowledge, the origin of this additional enhancement has never been satisfactorily explained. In this paper, finite difference time domain modeling is presented to show that the electric field intensity at the dielectric interface between metal particles is higher for ``far-side'' excitation than ``near-side''. This is reasonably consistent with the observed enhancement for silver islands on SiO2. The modeling results are supported by a simple analytical model based on Fresnel reflection at the interface, which suggests that the additional SERS signal is caused by near-field enhancement of the electric field due to the phase shift at the dielectric interface.

  6. High Power Piezoelectric Characterization for Piezoelectric Transformer Development

    NASA Astrophysics Data System (ADS)

    Ural, Seyit O.

    circuit to leave the resonator in an open circuit condition. The newly introduced open circuits burst have resulted in antiresonance quality factor measurements along with resonance quality factors in a "non-heating" sample. In this technique too, resonance and antiresonance losses showed significant difference. Resonance burst mode characterizations at elevated ambient temperatures have shown that the lower vibration velocity mechanical quality factors appear to be more sensitive to the ambient temperature. Design criteria's to produce the most power dense structure were investigated. Common device shapes were investigated to see which one does enhance the power density of the piezoelectric device. Disk shaped piezoelectric actuators have proven to have lower matching impedances and higher, farther persisting mechanical quality factors with respect to vibration velocities. In order to achieve identical power level, plate shaped samples will have been to strain ~3.5 times more than disk shaped samples. Thus the most power dense structure has been concluded to be a disk shape ~1W/cm3 Once the actuators shape was fixed, further design on structure were conducted with (c)ATILA finite element method. For the transformer application, the design considered following key factors; 1-Controlling the output impedance by optimizing number of layers and layer thicknesses of the multilayer and 2- Evaluation of various electrodes and their affect on high power performance was evaluated. As the thickness of active layers decreased, the number of electrode layers increases. This increase in the metal to piezoelectric ratio and the relative increase in the electrode resistance under high current loads, both will have to be accounted for. Thus; with the piezoelectric composition and the device structure optimized, the research input electrical power. Once the actuators shape was fixed, further design on structure were conducted with (c)ATILA finite element method. For the transformer

  7. Momentum transfer from solar wind to interplanetary field enhancements inferred from magnetic field draping signatures

    NASA Astrophysics Data System (ADS)

    Lai, H. R.; Russell, C. T.; Jia, Y. D.; Wei, H. Y.; Angelopoulos, V.

    2015-03-01

    Characterized by a cusp-shaped enhancement in the magnetic field strength, the magnetic structure in the solar wind, called an interplanetary field enhancement (IFE), has been investigated since its discovery. To understand its three-dimensional magnetic field geometry, we study an IFE detected by five spacecraft simultaneously. Field lines are seen draping around in the upstream region and rotating in the ambient convection electric field direction in the downstream region. Earlier studies suggest that IFEs are created when the solar wind accelerates newly formed dust clouds. Both signatures found in our study support this hypothesis: the field line draping is caused by dust-solar wind momentum exchange, while the field line rotation is a typical signature of dusty plasma pickup. The force that exchanges the momentum is approximately 106 N. This study illustrates the nature of the interaction between two flowing plasmas of very different mass-to-charge ratio.

  8. Aperiodic Photonic-Plasmonic Structures with Broadband Field Enhancement

    DTIC Science & Technology

    2012-10-15

    monomer, (d and g) dimer, (e and i ) trimer...components of the radial distribution function. (a-d) numerator, (e-h) denominator, ( i -l) entire radial distribution function...in the Y direction is 400 nm. Fig 7 d- i shows the scattering efficiency and maximum field enhancement of each array compared with that of the

  9. Enhancing Field Research Methods with Mobile Survey Technology

    ERIC Educational Resources Information Center

    Glass, Michael R.

    2015-01-01

    This paper assesses the experience of undergraduate students using mobile devices and a commercial application, iSurvey, to conduct a neighborhood survey. Mobile devices offer benefits for enhancing student learning and engagement. This field exercise created the opportunity for classroom discussions on the practicalities of urban research, the…

  10. Enhancement of gas phase heat transfer by acoustic field application.

    PubMed

    Komarov, Sergey; Hirasawa, Masahiro

    2003-06-01

    This study discusses a possibility for enhancement of heat transfer between solids and ambient gas by application of powerful acoustic fields. Experiments are carried out by using preheated Pt wires (length 0.1-0.15 m, diameter 50 and 100 micro m) positioned at the velocity antinode of a standing wave (frequency range 216-1031 Hz) or in the path of a travelling wave (frequency range 6.9-17.2 kHz). A number of experiments were conducted under conditions of gas flowing across the wire surface. Effects of sound frequency, sound strength, gas flow velocity and wire preheating temperature on the Nusselt number are examined with and without sound application. The gas phase heat transfer rate is enhanced with acoustic field strength. Higher temperatures result in a vigorous radiation from the wire surface and attenuate the effect of sound. The larger the gas flow velocity, the smaller is the effect of sound wave on heat transfer enhancement.

  11. Optical field enhancement by strong plasmon interaction in graphene nanostructures.

    PubMed

    Thongrattanasiri, Sukosin; García de Abajo, F Javier

    2013-05-03

    The ability of plasmons to enhance the electromagnetic field intensity in the gap between metallic nanoparticles derives from their strong optical confinement relative to the light wavelength. The spatial extension of plasmons in doped graphene has recently been shown to be boldly reduced with respect to conventional plasmonic metals. Here, we show that graphene nanostructures are capable of capitalizing such strong confinement to yield unprecedented levels of field enhancement, well beyond what is found in noble metals of similar dimensions (~ tens of nanometers). We perform realistic, quantum-mechanical calculations of the optical response of graphene dimers formed by nanodisks and nanotriangles, showing a strong sensitivity of the level of enhancement to the type of carbon edges near the gap region, with armchair edges favoring stronger interactions than zigzag edges. Our quantum-mechanical description automatically incorporates nonlocal effects that are absent in classical electromagnetic theory, leading to over an order of magnitude higher enhancement in armchair structures. The classical limit is recovered for large structures. We predict giant levels of light concentration for dimers ~200 nm, leading to infrared-absorption enhancement factors ~10(8). This extreme light enhancement and confinement in nanostructured graphene has great potential for optical sensing and nonlinear devices.

  12. On the generation of magnetic field enhanced microwave plasma line

    NASA Astrophysics Data System (ADS)

    Chen, Longwei; Zhao, Ying; Wu, Kenan; Wang, Qi; Meng, Yuedong; Ren, Zhaoxing

    2016-12-01

    Microwave linear plasmas sustained by surface waves have attracted much attention due to the potential abilities to generate large-scale and uniform non-equilibrium plasmas. An external magnetic field was generally applied to enhance and stabilize plasma sources because the magnetic field decreased the electron losses on the wall. The effects of magnetic field on the generation and propagation mechanisms of the microwave plasma were tentatively investigated based on a 2-D numerical model combining a coupled system of Maxwell's equations and continuity equations. The mobility of electrons and effective electric conductivity of the plasma were considered as a full tensor in the presence of magnetic field. Numerical results indicate that both cases of magnetic field in the axial-direction and radial-direction benefit the generation of a high-density plasma; the former one allows the microwave to propagate longer in the axis direction compared to the latter one. The time-averaged power flow density and the amplitude of the electric field on the inner rod of coaxial waveguide attenuate with the propagation of the microwave for both cases of with and without external magnetic field. The attenuation becomes smaller in the presence of appropriately higher axial-direction magnetic field, which allows more microwave energies to transmit along the axial direction. Meanwhile, the anisotropic properties of the plasma, like electron mobility, in the presence of the magnetic field confine more charged particles in the direction of the magnetic field line.

  13. Investigations of Magnetically Enhanced RIE Reactors with Rotating Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Babaeva, Natalia Yu.; Kushner, Mark J.

    2008-10-01

    In Magnetically Enhanced Reactive Ion Etching (MERIE) reactors, a magnetic field parallel to the substrate enables higher plasma densities and control of ion energy distributions. Since it is difficult to make the B-field uniform across the wafer, the B-field is often azimuthally rotated at a few Hz to average out non-uniformities. The rotation is slow enough that the plasma is in quasi-equilibrium with the instantaneous B-field. For the pressures (10's mTorr or less) and B-fields (10's - 100's G) of interest, electrons are magnetized whereas ions are usually not. The orientation and intersection of the B-field with the wafer are important, as intersecting field lines provide a low resistance path for electron current to the substrate. We report on a modeling study of plasma properties in MERIE reactors having rotating B-fields by investigating a series of quasi-steady states of B-field profiles. To resolve side-to-side variations, computations are performed in Cartesian coordinates. The model, nonPDPSIM, was improved with full tensor conductivities in the fluid portions of the code and v x B forces in the kinetic portions. Results are discussed while varying the orientation and strength of the B-field for electropositive (argon) and electronegative (Ar/CxFy, Ar/Cl2) gas mixtures.

  14. Towards field malaria diagnosis using surface enhanced Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Chen, Keren; Xiong, Aoli; Yuen, Clement; Preiser, Peter; Liu, Quan

    2016-04-01

    We report three strategies of surface enhanced Raman spectroscopy (SERS) for β-hematin and hemozoin detection in malaria infected human blood, which can be potentially developed for field malaria diagnosis. In the first strategy, we used silver coated magnetic nanoparticles (Fe3O4@Ag) in combination with an external magnetic field to enhance the Raman signal of β-hematin. Then we developed two SERS methods without the requirement of magnetic field for malaria infection diagnosis. In Method 1, silver nanoparticles were synthesized separately and then mixed with lysed blood just like in traditional SERS measurements; while in Method 2, we developed an ultrasensitive SERS method by synthesizing silver nanoparticles directly inside the parasites of Plasmodium falciparum. Method 2 can be also used to detect single parasites in the ring stage.

  15. Photo-enhanced field electron emission of cadmium sulfide nanowires

    NASA Astrophysics Data System (ADS)

    Zhang, Jinling; Lv, Yinghua; Liu, Ning; Li, Yanqing; Gao, Peng; Bai, Xuedong

    2011-11-01

    The response of field electron emission of cadmium sulfide (CdS) nanowires (NWs) to visible light has been investigated. It is found that, upon light illumination, the turn-on voltage drops, emission current increases obviously, and the Fowler-Nordheim behavior deviates from a straight line. A process of field emission coupled with semiconducting properties of CdS NWs is proposed. Photon-excited electron transition from the valence band to the conductance band of CdS nanowires increases the quantity of emitting electrons, and the photoemission decreases the effective work function of CdS emitters, which largely enhances the field emission performance. The response of field emission of CdS NWs to light illumination suggests an approach for tuning field emission of semiconductor emitters.

  16. Overcoming diffusion-limited processes using enhanced advective fields

    SciTech Connect

    Rasmussen, T.C.

    1995-12-31

    Many subsurface cleanup activities focus on the remediation of organic contaminants using induced advective fields. Subsurface heterogeneities cause most advective transport to occur in more permeable zones, with transport from the lower permeability units being limited by diffusion to the higher permeable units. While diffusion rates can be enhanced using thermal sources, many of the treatment strategies, including pump and treat, vapor extraction and bioremediation, are limited by mass exchange rates between the higher and lower permeability sand and clay mixtures. Instead of relying on the enhancement of diffusion rates, it is proposed that remediation strategies should focus on the enhancement of induced advective transport rates through the lower permeability units. Injection-extraction strategies using crosshole and huff-and-puff methods are presented for maximizing advective transport through lower permeability units. Optimization of the design can incorporate diffusion-enhancement technologies, bionourishment, capillary confinement in the unsaturated zone, and DNAPL slurping.

  17. Adaptive piezoelectric sensoriactuator

    NASA Technical Reports Server (NTRS)

    Clark, Jr., Robert L. (Inventor); Vipperman, Jeffrey S. (Inventor); Cole, Daniel G. (Inventor)

    1996-01-01

    An adaptive algorithm implemented in digital or analog form is used in conjunction with a voltage controlled amplifier to compensate for the feedthrough capacitance of piezoelectric sensoriactuator. The mechanical response of the piezoelectric sensoriactuator is resolved from the electrical response by adaptively altering the gain imposed on the electrical circuit used for compensation. For wideband, stochastic input disturbances, the feedthrough capacitance of the sensoriactuator can be identified on-line, providing a means of implementing direct-rate-feedback control in analog hardware. The device is capable of on-line system health monitoring since a quasi-stable dynamic capacitance is indicative of sustained health of the piezoelectric element.

  18. Notes on Piezoelectricity

    SciTech Connect

    Redondo, Antonio

    2016-02-03

    These notes provide a pedagogical discussion of the physics of piezoelectricity. The exposition starts with a brief analysis of the classical (continuum) theory of piezoelectric phenomena in solids. The main subject of the notes is, however, a quantum mechanical analysis. We first derive the Frohlich Hamiltonian as part of the description of the electron-phonon interaction. The results of this analysis are then employed to derive the equations of piezoelectricity. A couple of examples with the zinc blende and and wurtzite structures are presented at the end

  19. Radiation engineering of optical antennas for maximum field enhancement.

    PubMed

    Seok, Tae Joon; Jamshidi, Arash; Kim, Myungki; Dhuey, Scott; Lakhani, Amit; Choo, Hyuck; Schuck, Peter James; Cabrini, Stefano; Schwartzberg, Adam M; Bokor, Jeffrey; Yablonovitch, Eli; Wu, Ming C

    2011-07-13

    Optical antennas have generated much interest in recent years due to their ability to focus optical energy beyond the diffraction limit, benefiting a broad range of applications such as sensitive photodetection, magnetic storage, and surface-enhanced Raman spectroscopy. To achieve the maximum field enhancement for an optical antenna, parameters such as the antenna dimensions, loading conditions, and coupling efficiency have been previously studied. Here, we present a framework, based on coupled-mode theory, to achieve maximum field enhancement in optical antennas through optimization of optical antennas' radiation characteristics. We demonstrate that the optimum condition is achieved when the radiation quality factor (Q(rad)) of optical antennas is matched to their absorption quality factor (Q(abs)). We achieve this condition experimentally by fabricating the optical antennas on a dielectric (SiO(2)) coated ground plane (metal substrate) and controlling the antenna radiation through optimizing the dielectric thickness. The dielectric thickness at which the matching condition occurs is approximately half of the quarter-wavelength thickness, typically used to achieve constructive interference, and leads to ∼20% higher field enhancement relative to a quarter-wavelength thick dielectric layer.

  20. Tip-enhanced near-field optical microscopy

    PubMed Central

    Mauser, Nina; Hartschuh, Achim

    2013-01-01

    Tip-enhanced near-field optical microscopy (TENOM) is a scanning probe technique capable of providing a broad range of spectroscopic information on single objects and structured surfaces at nanometer spatial resolution and with highest detection sensitivity. In this review, we first illustrate the physical principle of TENOM that utilizes the antenna function of a sharp probe to efficiently couple light to excitations on nanometer length scales. We then discuss the antenna-induced enhancement of different optical sample responses including Raman scattering, fluorescence, generation of photocurrent and electroluminescence. Different experimental realizations are presented and several recent examples that demonstrate the capabilities of the technique are reviewed. PMID:24100541

  1. Investigation of nanogap localized field enhancement in gold plasmonic structures

    NASA Astrophysics Data System (ADS)

    Debu, Desalegn Tadesse; Bauman, Stephen; Saylor, Cameron; Novak, Eric; French, David; Herzog, Joseph

    2015-03-01

    Nanogaps between plasmonic structures allow confining the localized electric field with moreenhancements. Based on previously implemented two-step lithography process, we introducea nano-masking technique to fabricate nanostructrues and nanogaps for various geometrical patterns. This new method can fabricate gold nanostructures as well as nanogaps that are less than 10nm, below the limiting scale of lithography. Simulation from finite element method (FEM) shows strong gap dependence of optical properties and peak enhancement of these devices. The fabricated plasmonic nanostructure provides wide range of potential future application including highly sensitive optical antenna, surface enhanced Raman spectroscopy and biosensing.

  2. Strongly enhanced field-dependent single-molecule electroluminescence

    NASA Astrophysics Data System (ADS)

    Lee, Tae-Hee; Gonzalez, Jose I.; Dickson, Robert M.

    2002-08-01

    Individual, strongly electroluminescent Agn molecules (n = 28 atoms) have been electrically written within otherwise nonemissive silver oxide films. Exhibiting characteristic single-molecule behavior, these individual room-temperature molecules exhibit extreme electroluminescence enhancements (>104 vs. bulk and dc excitation on a per molecule basis) when excited with specific ac frequencies. Occurring through field extraction of electrons with subsequent reinjection and radiative recombination, single-molecule electroluminescence is enhanced by a general mechanism that avoids slow bulk material response. Thus, while we detail strong electroluminescence from single, highly fluorescent Agn molecules, this mechanism also yields strong ac-excited electroluminescence from similarly prepared, but otherwise nonemissive, individual Cu nanoclusters.

  3. Contour Enhancement Benefits Older Adults with Simulated Central Field Loss

    PubMed Central

    Kwon, MiYoung; Ramachandra, Chaithanya; Satgunam, PremNandhini; Mel, Bartlett W.; Peli, Eli; Tjan, Bosco S.

    2012-01-01

    Purpose Age-related macular degeneration (AMD) is the leading cause of vision loss among Americans over the age of 65. Currently, no effective treatment can reverse the central vision loss associated with most AMD. Digital image-processing techniques have been developed to improve image visibility for peripheral vision; however, both the selection and efficacy of such methods are limited. Progress has been difficult for two reasons: the exact nature of image enhancement that might benefit peripheral vision is not well understood, and efficient methods for testing such techniques have been elusive. The current study aims to develop both an effective image-enhancement technique for peripheral vision and an efficient means for validating the technique. Methods We used a novel contour detection algorithm to locate shape-defining edges in images based on natural-image statistics. We then enhanced the scene by locally boosting the luminance contrast along such contours. Using a gaze-contingent display, we simulated central visual field loss in normally-sighted young (ages 18–30) and older adults (ages 58–88). Visual search performance was measured as a function of contour enhancement strength ("Original" (unenhanced), "Medium", and "High"). For preference task, a separate group of subjects judged which image in a pair "would lead to better search performance". Results We found that while contour enhancement had no significant effect on search time and accuracy in young adults, Medium enhancement resulted in significantly shorter search time in older adults (~13% reduction relative to Original). Both age groups preferred images with Medium enhancement over Original (2 to 7 times). Furthermore, across age groups, image content types and enhancement strengths, there was a robust correlation between preference and performance. Conclusions Our findings demonstrate a beneficial role of contour enhancement in peripheral vision for older adults. Our findings further suggest

  4. Piezoelectric micromotors for microrobots

    NASA Astrophysics Data System (ADS)

    Flynn, Anita M.; Tavrow, Lee S.; Bart, Stephen F.; Brooks, Rodney A.; Ehrlich, Daniel J.; Udayakumar, K. R.; Cross, L. E.

    1992-03-01

    The authors have begun research into piezoelectric ultrasonic motors using ferroelectric thin films. The authors have fabricated the stator components of these millimeter diameter motors on silicon wafers. Ultrasonic motors consist of two pieces: a stator and a rotor. The stator includes a piezoelectric film in which bending is induced in the form of a traveling wave. A small glass lens placed upon the stator becomes the spinning rotor. Piezoelectric micromotors overcome the problems currently associated with electrostatic micromotors such as low torque, friction, and the need for high voltage excitation. More importantly, they may offer a much simpler mechanism for coupling power out. Using thin films of lead zirconate titanate on silicon nitride membranes, various types of actuator structures can be fabricated. By combining new robot control systems with piezoelectric motors and micromechanics, the authors propose creating micromechanical systems that are small, cheap and completely autonomous.

  5. Energy collection via Piezoelectricity

    NASA Astrophysics Data System (ADS)

    Naveen Kumar, Ch

    2015-12-01

    In the present days, wireless data transmission techniques are commonly used in electronic devices. For powering them connection needs to be made to the power supply through wires else power may be supplied from batteries. Batteries require charging, replacement and other maintenance efforts. So, some alternative methods need to be developed to keep the batteries full time charged and to avoid the need of any consumable external energy source to charge the batteries. Mechanical energy harvesting utilizes piezoelectric components where deformations produced by different means are directly converted to electrical charge via piezoelectric effect. The proposed work in this research recommends Piezoelectricity as a alternate energy source. The motive is to obtain a pollution-free energy source and to utilize and optimize the energy being wasted. Current work also illustrates the working principle of piezoelectric crystal and various sources of vibration for the crystal.

  6. Effects of the poling process on dielectric, piezoelectric, and ferroelectric properties of lead zirconate titanate

    NASA Astrophysics Data System (ADS)

    Prewitt, Anderson D.

    Smart materials are widely used in many of today's relevant technologies such as nano and micro electromechanical systems (NEMS and MEMS), sensors, actuators, nonvolatile memory, and solid state devices. Many of these systems rely heavily on the electromechanical properties of certain smart materials, such as piezoelectricity and ferroelectricity. By definition, piezoelectricity is a mechanical stress in a material that produces an electric displacement (known as the direct piezoelectric effect) or electrical charge in a material which produces a mechanical strain (known as the converse piezoelectric effect). Ferroelectricity is a sub-class of piezoelectricity in which the polarization occurs spontaneously and the dipoles can be reoriented. Domain walls are the nanoscale regions separating two finite distinctively polarized areas in a ferroelectric. The reorientation of polarization in a material is called the poling process and many factors can influence the effectiveness of this process. A more fundamental understanding of how electrical and mechanical loading changes the domain structure of these materials could lead to enhanced properties such as increased energy transduction and decreased nonlinear behavior. This research demonstrates the influence of mechanical pressure and electrical field during and after the poling process on domain walls. The effects of strong mechanical forces on large-scale domain switching and weak cyclic forces on small-scale domain wall motion are investigated to show how they affect the macroscopic behavior of these materials. Commercial lead zirconate titanate ceramics were studied under various poling conditions and the effect of domain wall motion on the piezoelectric, dielectric, and ferroelectric properties was investigated. Polarization and strain measurements from samples poled at specific conditions and converse piezoelectric coefficient and dielectric permittivity data was extracted and interpreted in the context of

  7. Giant piezoelectricity of monolayer group IV monochalcogenides

    NASA Astrophysics Data System (ADS)

    Fei, Ruixiang; Li, Wenbin; Li, Ju; Yang, Li

    We predict enormous, anisotropic piezoelectric effects in intrinsic monolayer group IV monochalcogenides (MX, M =Sn or Ge, X =Se or S), including SnSe, SnS, GeSe, and GeS. Using first-principle simulations based on the modern theory of polarization, we find that their piezoelectric coefficients are about one to two orders of magnitude larger than those of other 2D materials, such as MoS2 and GaSe, and bulk quartz and AlN which are widely used in industry. This enhancement is a result of the unique ``puckered'' C2v symmetry and electronic structure of monolayer group IV monochalcogenides. Given the achieved experimental advances in the fabrication of monolayers, their flexible character, and ability to withstand enormous strain, these 2D structures with giant piezoelectric effects may be promising for a broad range of applications such as nano-sized sensors, piezotronics, and energy harvesting in portable electronic devices.

  8. Enhancement of fast electron energy deposition by external magnetic fields

    NASA Astrophysics Data System (ADS)

    Honrubia, J. J.; Murakami, M.; Mima, K.; Johzaki, T.; Sunahara, A.; Nagatomo, H.; Fujioka, S.; Shiraga, H.; Azechi, H.

    2016-03-01

    Recently, generation of external magnetic fields of a few kT has been reported [Fujioka et al. Scientific Reports 2013 3 1170]. These fields can be used in fast ignition to mitigate the large fast electron divergence. In this summary, two fast ignition applications are briefly outlined. The first one deals with electron guiding by external B-fields applied at the end of the shell implosion of a re-entrant cone target. Preliminary results show that the B-field strength at the time of peak ρR may be sufficiently high for fast electron guiding. The second application deals with guiding of fast electrons in magnetized wires surrounded by plasma. Results show a significant enhancement of electron energy deposition at the end of the wire, which is particularly important for low-Z wires.

  9. ZAP - enhanced PCA sky subtraction for integral field spectroscopy

    NASA Astrophysics Data System (ADS)

    Soto, Kurt T.; Lilly, Simon J.; Bacon, Roland; Richard, Johan; Conseil, Simon

    2016-05-01

    We introduce Zurich Atmosphere Purge (ZAP), an approach to sky subtraction based on principal component analysis (PCA) that we have developed for the Multi Unit Spectrographic Explorer (MUSE) integral field spectrograph. ZAP employs filtering and data segmentation to enhance the inherent capabilities of PCA for sky subtraction. Extensive testing shows that ZAP reduces sky emission residuals while robustly preserving the flux and line shapes of astronomical sources. The method works in a variety of observational situations from sparse fields with a low density of sources to filled fields in which the target source fills the field of view. With the inclusion of both of these situations, the method is generally applicable to many different science cases and should also be useful for other instrumentation. ZAP is available for download at http://muse-vlt.eu/science/tools.

  10. Laminated piezoelectric transformer

    NASA Technical Reports Server (NTRS)

    Vazquez Carazo, Alfredo (Inventor)

    2006-01-01

    A laminated piezoelectric transformer is provided using the longitudinal vibration modes for step-up voltage conversion applications. The input portions are polarized to deform in a longitudinal plane and are bonded to an output portion. The deformation of the input portions is mechanically coupled to the output portion, which deforms in the same longitudinal direction relative to the input portion. The output portion is polarized in the thickness direction relative its electrodes, and piezoelectrically generates a stepped-up output voltage.

  11. Piezoelectric Energy Harvesting Solutions

    PubMed Central

    Caliò, Renato; Rongala, Udaya Bhaskar; Camboni, Domenico; Milazzo, Mario; Stefanini, Cesare; de Petris, Gianluca; Oddo, Calogero Maria

    2014-01-01

    This paper reviews the state of the art in piezoelectric energy harvesting. It presents the basics of piezoelectricity and discusses materials choice. The work places emphasis on material operating modes and device configurations, from resonant to non-resonant devices and also to rotational solutions. The reviewed literature is compared based on power density and bandwidth. Lastly, the question of power conversion is addressed by reviewing various circuit solutions. PMID:24618725

  12. Piezoelectric and magnetoelectric thick films for fabricating power sources in wireless sensor nodes.

    PubMed

    Priya, Shashank; Ryu, Jungho; Park, Chee-Sung; Oliver, Josiah; Choi, Jong-Jin; Park, Dong-Soo

    2009-01-01

    In this manuscript, we review the progress made in the synthesis of thick film-based piezoelectric and magnetoelectric structures for harvesting energy from mechanical vibrations and magnetic field. Piezoelectric compositions in the system Pb(Zr,Ti)O(3)-Pb(Zn(1/3)Nb(2/3))O(3) (PZNT) have shown promise for providing enhanced efficiency due to higher energy density and thus form the base of transducers designed for capturing the mechanical energy. Laminate structures of PZNT with magnetostrictive ferrite materials provide large magnitudes of magnetoelectric coupling and are being targeted to capture the stray magnetic field energy. We analyze the models used to predict the performance of the energy harvesters and present a full system description.

  13. Piezoelectric and Magnetoelectric Thick Films for Fabricating Power Sources in Wireless Sensor Nodes

    PubMed Central

    Priya, Shashank; Ryu, Jungho; Park, Chee-Sung; Oliver, Josiah; Choi, Jong-Jin; Park, Dong-Soo

    2009-01-01

    In this manuscript, we review the progress made in the synthesis of thick film-based piezoelectric and magnetoelectric structures for harvesting energy from mechanical vibrations and magnetic field. Piezoelectric compositions in the system Pb(Zr,Ti)O3–Pb(Zn1/3Nb2/3)O3 (PZNT) have shown promise for providing enhanced efficiency due to higher energy density and thus form the base of transducers designed for capturing the mechanical energy. Laminate structures of PZNT with magnetostrictive ferrite materials provide large magnitudes of magnetoelectric coupling and are being targeted to capture the stray magnetic field energy. We analyze the models used to predict the performance of the energy harvesters and present a full system description. PMID:22454590

  14. Enhanced proton acceleration in an applied longitudinal magnetic field

    NASA Astrophysics Data System (ADS)

    Toncian, Toma; Arefiev, Alexey; Fiksel, Gennady

    2016-10-01

    Using two-dimensional particle-in-cell simulations, we examine how an externally applied strong magnetic impacts proton acceleration in laser-irradiated solid-density targets. We find that a kT-level external magnetic field can sufficiently inhibit transverse transport of hot electrons in a flat laser-irradiated target. While the electron heating by the laser remains mostly unaffected, the reduced electron transport during proton acceleration leads to an enhancement of maximum proton energies and the overall number of energetic protons. The resulting proton beam is much better collimated compared to a beam generated without applying a kT-level magnetic field. A factor of three enhancement of the laser energy conversion efficiency into multi-MeV protons is another effect of the magnetic field. The required kT magnetic fields are becoming feasible due to a significant progress that has been made in generating magnetic fields with laser-driven coils using ns-long laser pulses. The predicted improved characteristics of laser-driven proton beams would be critical for a number of applications. The work was supported by U.S. Department of Energy - National Nuclear Security Administration Cooperative Agreement No. DE-NA0002008. HPC resources were provided by the Texas Advanced Computing Center at The University of Texas.

  15. Piezoelectrically Initiated Pyrotechnic Igniter

    NASA Technical Reports Server (NTRS)

    Quince, Asia; Dutton, Maureen; Hicks, Robert; Burnham, Karen

    2013-01-01

    This innovation consists of a pyrotechnic initiator and piezoelectric initiation system. The device will be capable of being initiated mechanically; resisting initiation by EMF, RF, and EMI (electromagnetic field, radio frequency, and electromagnetic interference, respectively); and initiating in water environments and space environments. Current devices of this nature are initiated by the mechanical action of a firing pin against a primer. Primers historically are prone to failure. These failures are commonly known as misfires or hang-fires. In many cases, the primer shows the dent where the firing pin struck the primer, but the primer failed to fire. In devices such as "T" handles, which are commonly used to initiate the blowout of canopies, loss of function of the device may result in loss of crew. In devices such as flares or smoke generators, failure can result in failure to spot a downed pilot. The piezoelectrically initiated ignition system consists of a pyrotechnic device that plugs into a mechanical system (activator), which on activation, generates a high-voltage spark. The activator, when released, will strike a stack of electrically linked piezo crystals, generating a high-voltage, low-amperage current that is then conducted to the pyro-initiator. Within the initiator, an electrode releases a spark that passes through a pyrotechnic first-fire mixture, causing it to combust. The combustion of the first-fire initiates a primary pyrotechnic or explosive powder. If used in a "T" handle, the primary would ramp the speed of burn up to the speed of sound, generating a shock wave that would cause a high explosive to go "high order." In a flare or smoke generator, the secondary would produce the heat necessary to ignite the pyrotechnic mixture. The piezo activator subsystem is redundant in that a second stack of crystals would be struck at the same time with the same activation force, doubling the probability of a first strike spark generation. If the first

  16. Can a spectator scalar field enhance inflationary tensor mode?

    NASA Astrophysics Data System (ADS)

    Fujita, Tomohiro; Yokoyama, Jun'ichi; Yokoyama, Shuichiro

    2015-04-01

    We consider the possibility of enhancing the inflationary tensor mode by introducing a spectator scalar field with a small sound speed which induces gravitational waves as a second-order effect. We analytically obtain the power spectra of gravitational waves and curvature perturbation induced by the spectator scalar field. We find that the small sound speed amplifies the curvature perturbation much more than the tensor mode and the current observational constraint forces the induced gravitational waves to be negligible compared with those from the vacuum fluctuation during inflation.

  17. Stretchable piezoelectric nanocomposite generator.

    PubMed

    Park, Kwi-Il; Jeong, Chang Kyu; Kim, Na Kyung; Lee, Keon Jae

    2016-01-01

    Piezoelectric energy conversion that generate electric energy from ambient mechanical and vibrational movements is promising energy harvesting technology because it can use more accessible energy resources than other renewable natural energy. In particular, flexible and stretchable piezoelectric energy harvesters which can harvest the tiny biomechanical motions inside human body into electricity properly facilitate not only the self-powered energy system for flexible and wearable electronics but also sensitive piezoelectric sensors for motion detectors and in vivo diagnosis kits. Since the piezoelectric ZnO nanowires (NWs)-based energy harvesters (nanogenerators) were proposed in 2006, many researchers have attempted the nanogenerator by using the various fabrication process such as nanowire growth, electrospinning, and transfer techniques with piezoelectric materials including polyvinylidene fluoride (PVDF) polymer and perovskite ceramics. In 2012, the composite-based nanogenerators were developed using simple, low-cost, and scalable methods to overcome the significant issues with previously-reported energy harvester, such as insufficient output performance and size limitation. This review paper provides a brief overview of flexible and stretchable piezoelectric nanocomposite generator for realizing the self-powered energy system with development history, power performance, and applications.

  18. Stretchable piezoelectric nanocomposite generator

    NASA Astrophysics Data System (ADS)

    Park, Kwi-Il; Jeong, Chang Kyu; Kim, Na Kyung; Lee, Keon Jae

    2016-06-01

    Piezoelectric energy conversion that generate electric energy from ambient mechanical and vibrational movements is promising energy harvesting technology because it can use more accessible energy resources than other renewable natural energy. In particular, flexible and stretchable piezoelectric energy harvesters which can harvest the tiny biomechanical motions inside human body into electricity properly facilitate not only the self-powered energy system for flexible and wearable electronics but also sensitive piezoelectric sensors for motion detectors and in vivo diagnosis kits. Since the piezoelectric ZnO nanowires (NWs)-based energy harvesters (nanogenerators) were proposed in 2006, many researchers have attempted the nanogenerator by using the various fabrication process such as nanowire growth, electrospinning, and transfer techniques with piezoelectric materials including polyvinylidene fluoride (PVDF) polymer and perovskite ceramics. In 2012, the composite-based nanogenerators were developed using simple, low-cost, and scalable methods to overcome the significant issues with previously-reported energy harvester, such as insufficient output performance and size limitation. This review paper provides a brief overview of flexible and stretchable piezoelectric nanocomposite generator for realizing the self-powered energy system with development history, power performance, and applications.

  19. Could Radiotherapy Effectiveness Be Enhanced by Electromagnetic Field Treatment?

    PubMed Central

    Francisco, Artacho-Cordón; del Mar, Salinas-Asensio María; Irene, Calvente; Sandra, Ríos-Arrabal; Josefa, León; Elisa, Román-Marinetto; Nicolás, Olea; Isabel, Núñez María

    2013-01-01

    One of the main goals in radiobiology research is to enhance radiotherapy effectiveness without provoking any increase in toxicity. In this context, it has been proposed that electromagnetic fields (EMFs), known to be modulators of proliferation rate, enhancers of apoptosis and inductors of genotoxicity, might control tumor recruitment and, thus, provide therapeutic benefits. Scientific evidence shows that the effects of ionizing radiation on cellular compartments and functions are strengthened by EMF. Although little is known about the potential role of EMFs in radiotherapy (RT), the radiosensitizing effect of EMFs described in the literature could support their use to improve radiation effectiveness. Thus, we hypothesized that EMF exposure might enhance the ionizing radiation effect on tumor cells, improving the effects of RT. The aim of this paper is to review reports of the effects of EMFs in biological systems and their potential therapeutic benefits in radiotherapy. PMID:23867611

  20. Field Enhancement Properties of Nanotubes in a Field Emission Set-Up

    NASA Technical Reports Server (NTRS)

    Adessi, Ch.; Devel, M.

    2001-01-01

    This slide presentation reviews the mechanisms of emission of nanotubes. The field enhancement properties of carbon nanotubes, involved in the emission of electrons, is investigated theoretically for various single-wall (SWNT) and multi-wall nanotubes (MWNT). The presentation points out big differences between (n,0) and (n,n) nanotubes, and propose phenomenological laws for the variations of the enhancement factor with length and diameter

  1. Thermal model for piezoelectric transducers (L).

    PubMed

    Butler, John L; Butler, Alexander L; Butler, Stephen C

    2012-10-01

    A lumped parameter equivalent circuit basis for calculating and allocating heat power sources in a transducer is presented along with experimental results. The simple model allows heat power calculations at resonance based on readily attainable parameters for transducers with uniform fields. Measured and finite element analysis of steady state thermal results are compared for the monopole mode of the single crystal driven modal transducer projector. The model serves as a physical and computational aid in the evaluation of piezoelectric transducer heating and may be used for evaluating highly coupled single crystal as well as ceramic piezoelectric transducers.

  2. Passively Damped Laminated Piezoelectric Shell Structures with Integrated Electric Networks

    NASA Technical Reports Server (NTRS)

    Saravanos, Dimitris A.

    1999-01-01

    Multi-field mechanics are presented for curvilinear piezoelectric laminates interfaced with distributed passive electric components. The equations of motion for laminated piezoelectric shell structures with embedded passive electric networks are directly formulated and solved using a finite element methodology. The modal damping and frequencies of the piezoelectric shell are calculated from the poles of the system. Experimental and numerical results are presented for the modal damping and frequency of composite beams with a resistively shunted piezoceramic patch. The modal damping and frequency of plates, cylindrical shells and cylindrical composite blades with piezoelectric-resistor layers are predicted. Both analytical and experimental studies illustrate a unique dependence of modal damping and frequencies on the shunting resistance and show the effect of structural shape and curvature on piezoelectric damping.

  3. Intrinsic space charge layers and field enhancement in ferroelectric nanojunctions

    DOE PAGES

    Cao, Ye; Ievlev, Anton V.; Morozovska, Anna N.; ...

    2015-07-13

    The conducting characteristics of topological defects in the ferroelectric materials, such as charged domain walls in ferroelectric materials, engendered broad interest and extensive study on their scientific merit and the possibility of novel applications utilizing domain engineering. At the same time, the problem of electron transport in ferroelectrics themselves still remains full of unanswered questions, and becomes still more relevant over the impending revival of interest in ferroelectric semiconductors and new improper ferroelectric materials. We have employed self-consistent phase-field modeling to investigate the physical properties of a local metal-ferroelectric (Pb(Zr0.2Ti0.8)O3) junction in applied electric field. We revealed an up tomore » 10-fold local field enhancement realized by large polarization gradient and over-polarization effects once the inherent non-linear dielectric properties of PZT are considered. The effect is independent of bias polarity and maintains its strength prior, during and after ferroelectric switching. The local field enhancement can be considered equivalent to increase of doping level, which will give rise to reduction of the switching bias and significantly smaller voltages to charge injection and electronic injection, electrochemical and photoelectrochemical processes.« less

  4. Intrinsic space charge layers and field enhancement in ferroelectric nanojunctions

    NASA Astrophysics Data System (ADS)

    Cao, Ye; Ievlev, Anton V.; Morozovska, Anna N.; Chen, Long-Qing; Kalinin, Sergei V.; Maksymovych, Petro

    2015-07-01

    Conducting characteristics of topological defects in ferroelectric materials, such as charged domain walls, engendered a broad interest on their scientific merit and the possibility of novel applications utilizing domain engineering. At the same time, the problem of electron transport in ferroelectrics still remains full of unanswered questions and becomes yet more relevant over the growing interest in ferroelectric semiconductors and new improper ferroelectric materials. We have employed self-consistent phase-field modeling to investigate the physical properties of a local metal-ferroelectric (Pb(Zr0.2Ti0.8)O3) junction in applied electric field. We revealed an up to 10-fold local enhancement of electric field realized by large polarization gradient and over-polarization effects due to inherent non-linear dielectric properties of Pb(Zr0.2Ti0.8)O3. The effect is independent of bias polarity and maintains its strength prior, during and after ferroelectric switching. The observed field enhancement can be considered on similar grounds as increased doping level, giving rise to reduced switching bias and threshold voltages for charge injection, electrochemical and photoelectrochemical processes.

  5. Intrinsic space charge layers and field enhancement in ferroelectric nanojunctions

    SciTech Connect

    Cao, Ye; Ievlev, Anton V.; Morozovska, Anna N.; Chen, Long-Qing; Kalinin, Sergei V.; Maksymovych, Petro

    2015-07-13

    The conducting characteristics of topological defects in the ferroelectric materials, such as charged domain walls in ferroelectric materials, engendered broad interest and extensive study on their scientific merit and the possibility of novel applications utilizing domain engineering. At the same time, the problem of electron transport in ferroelectrics themselves still remains full of unanswered questions, and becomes still more relevant over the impending revival of interest in ferroelectric semiconductors and new improper ferroelectric materials. We have employed self-consistent phase-field modeling to investigate the physical properties of a local metal-ferroelectric (Pb(Zr0.2Ti0.8)O3) junction in applied electric field. We revealed an up to 10-fold local field enhancement realized by large polarization gradient and over-polarization effects once the inherent non-linear dielectric properties of PZT are considered. The effect is independent of bias polarity and maintains its strength prior, during and after ferroelectric switching. The local field enhancement can be considered equivalent to increase of doping level, which will give rise to reduction of the switching bias and significantly smaller voltages to charge injection and electronic injection, electrochemical and photoelectrochemical processes.

  6. Intrinsic space charge layers and field enhancement in ferroelectric nanojunctions

    SciTech Connect

    Cao, Ye; Ievlev, Anton V.; Kalinin, Sergei V.; Maksymovych, Petro; Morozovska, Anna N.; Chen, Long-Qing

    2015-07-13

    Conducting characteristics of topological defects in ferroelectric materials, such as charged domain walls, engendered a broad interest on their scientific merit and the possibility of novel applications utilizing domain engineering. At the same time, the problem of electron transport in ferroelectrics still remains full of unanswered questions and becomes yet more relevant over the growing interest in ferroelectric semiconductors and new improper ferroelectric materials. We have employed self-consistent phase-field modeling to investigate the physical properties of a local metal-ferroelectric (Pb(Zr{sub 0.2}Ti{sub 0.8})O{sub 3}) junction in applied electric field. We revealed an up to 10-fold local enhancement of electric field realized by large polarization gradient and over-polarization effects due to inherent non-linear dielectric properties of Pb(Zr{sub 0.2}Ti{sub 0.8})O{sub 3}. The effect is independent of bias polarity and maintains its strength prior, during and after ferroelectric switching. The observed field enhancement can be considered on similar grounds as increased doping level, giving rise to reduced switching bias and threshold voltages for charge injection, electrochemical and photoelectrochemical processes.

  7. Research on micro-displacement driving technology based on piezoelectric ceramic

    NASA Astrophysics Data System (ADS)

    Hu, Bo; Tang, Xiaoping; Hu, Song; Yan, Wei; Hu, Zhicheng

    2012-10-01

    Piezoelectric ceramic driving power is one critical technology of achieving the piezoelectric ceramic nano-precision positioning, which has been widely used in precision manufacturing, optical instruments, aerospace and other fields. In this paper, piezoelectric ceramic driving power will be summarized on micro-displacement driving technical development and research. The domestic and overseas piezoelectric-driven ways will be compared and control model algorithms will be discussed. Describe the advantages and disadvantages of piezoelectric ceramic driving power in a different driving and control model, and then show the scope of application of driving power.

  8. Electric-field-enhanced condensation on superhydrophobic nanostructured surfaces.

    PubMed

    Miljkovic, Nenad; Preston, Daniel J; Enright, Ryan; Wang, Evelyn N

    2013-12-23

    When condensed droplets coalesce on a superhydrophobic nanostructured surface, the resulting droplet can jump due to the conversion of excess surface energy into kinetic energy. This phenomenon has been shown to enhance condensation heat transfer by up to 30% compared to state-of-the-art dropwise condensing surfaces. However, after the droplets jump away from the surface, the existence of the vapor flow toward the condensing surface increases the drag on the jumping droplets, which can lead to complete droplet reversal and return to the surface. This effect limits the possible heat transfer enhancement because larger droplets form upon droplet return to the surface, which impedes heat transfer until they can be either removed by jumping again or finally shedding via gravity. By characterizing individual droplet trajectories during condensation on superhydrophobic nanostructured copper oxide (CuO) surfaces, we show that this vapor flow entrainment dominates droplet motion for droplets smaller than R ≈ 30 μm at moderate heat fluxes (q″ > 2 W/cm(2)). Subsequently, we demonstrate electric-field-enhanced condensation, whereby an externally applied electric field prevents jumping droplet return. This concept leverages our recent insight that these droplets gain a net positive charge due to charge separation of the electric double layer at the hydrophobic coating. As a result, with scalable superhydrophobic CuO surfaces, we experimentally demonstrated a 50% higher overall condensation heat transfer coefficient compared to that on a jumping-droplet surface with no applied field for low supersaturations (<1.12). This work not only shows significant condensation heat transfer enhancement but also offers avenues for improving the performance of self-cleaning and anti-icing surfaces as well as thermal diodes.

  9. Piezoelectric Templates - New Views on Biomineralization and Biomimetics.

    PubMed

    Stitz, Nina; Eiben, Sabine; Atanasova, Petia; Domingo, Neus; Leineweber, Andreas; Burghard, Zaklina; Bill, Joachim

    2016-05-23

    Biomineralization in general is based on electrostatic interactions and molecular recognition of organic and inorganic phases. These principles of biomineralization have also been utilized and transferred to bio-inspired synthesis of functional materials during the past decades. Proteins involved in both, biomineralization and bio-inspired processes, are often piezoelectric due to their dipolar character hinting to the impact of a template's piezoelectricity on mineralization processes. However, the piezoelectric contribution on the mineralization process and especially the interaction of organic and inorganic phases is hardly considered so far. We herein report the successful use of the intrinsic piezoelectric properties of tobacco mosaic virus (TMV) to synthesize piezoelectric ZnO. Such films show a two-fold increase of the piezoelectric coefficient up to 7.2 pm V(-1) compared to films synthesized on non-piezoelectric templates. By utilizing the intrinsic piezoelectricity of a biotemplate, we thus established a novel synthesis pathway towards functional materials, which sheds light on the whole field of biomimetics. The obtained results are of even broader and general interest since they are providing a new, more comprehensive insight into the mechanisms involved into biomineralization in living nature.

  10. Characterization and in vitro cytocompatibility of piezoelectric electrospun scaffolds.

    PubMed

    Weber, N; Lee, Y-S; Shanmugasundaram, S; Jaffe, M; Arinzeh, T L

    2010-09-01

    Previous studies have shown that electrical charges influence cell behavior (e.g. enhancement of nerve regeneration, cell adhesion, cell morphology). Thus, piezoelectric scaffolds might be useful for various tissue engineering applications. Fibrous scaffolds were successfully fabricated from permanent piezoelectric poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) by the electrospinning technique. Scanning electron microscopy and capillary flow analyses verified that the fiber mats had an average fiber diameter of 970 +/- 480 nm and a mean pore diameter of 1.7 microm, respectively. Thermally stimulated depolarization current spectroscopy measurements confirmed the piezoelectric property of the PVDF-TrFE fibrous scaffolds by the generation of a spontaneous current with the increase in temperature in the absence of an electric field, which was not detected in the unprocessed PVDF-TrFE powder. Differential scanning calorimetry, thermogravimetric analysis, X-ray diffraction and Fourier transform infrared spectroscopy results showed that the electrospinning process increased the crystallinity and presence of the polar, beta-phase crystal compared with the unprocessed powder. Confocal fluorescence microscopy and a cell proliferation assay demonstrated spreading and increased cell numbers (human skin fibroblasts) over time on PVDF-TrFE scaffolds, which was comparable with tissue culture polystyrene. The relative quantity of gene expression for focal adhesion proteins (measured by real-time RT-PCR) increased in the following order: paxillin < vinculin < focal adhesion kinase < talin. However, no differences could be seen among the TCPS surface and the fibrous scaffolds. Future studies will focus on possible applications of these cytocompatible PVDF-TrFE scaffolds in the field of regenerative medicine.

  11. Overview of NASA Langley's Piezoelectric Ceramic Packaging Technology and Applications

    NASA Technical Reports Server (NTRS)

    Bryant, Robert G.

    2007-01-01

    Over the past decade, NASA Langley Research Center (LaRC) has developed several actuator packaging concepts designed to enhance the performance of commercial electroactive ceramics. NASA LaRC focused on properly designed actuator and sensor packaging for the following reasons, increased durability, protect the working material from the environment, allow for proper mechanical and electrical contact, afford "ready to use" mechanisms that are scalable, and develop fabrication methodology applicable to any active material of the same physical class. It is more cost effective to enhance or tailor the performance of existing systems, through innovative packaging, than to develop, test and manufacture new materials. This approach led to the development of several solid state actuators that include THUNDER, the Macrofiber Composite or (MFC) and the Radial Field Diaphragm or (RFD). All these actuators are fabricated using standard materials and processes derived from earlier concepts. NASA s fabrication and packaging technology as yielded, piezoelectric actuators and sensors that are easy to implement, reliable, consistent in properties, and of lower cost to manufacture in quantity, than their predecessors (as evidenced by their continued commercial availability.) These piezoelectric actuators have helped foster new research and development in areas involving computational modeling, actuator specific refinements, and engineering system redesign which led to new applications for piezo-based devices that replace traditional systems currently in use.

  12. Piezoelectric Ceramics and Their Applications

    ERIC Educational Resources Information Center

    Flinn, I.

    1975-01-01

    Describes the piezoelectric effect in ceramics and presents a quantitative representation of this effect. Explains the processes involved in the manufacture of piezoelectric ceramics, the materials used, and the situations in which they are applied. (GS)

  13. Quantum dynamical simulations of local field enhancement in metal nanoparticles.

    PubMed

    Negre, Christian F A; Perassi, Eduardo M; Coronado, Eduardo A; Sánchez, Cristián G

    2013-03-27

    Field enhancements (Γ) around small Ag nanoparticles (NPs) are calculated using a quantum dynamical simulation formalism and the results are compared with electrodynamic simulations using the discrete dipole approximation (DDA) in order to address the important issue of the intrinsic atomistic structure of NPs. Quite remarkably, in both quantum and classical approaches the highest values of Γ are located in the same regions around single NPs. However, by introducing a complete atomistic description of the metallic NPs in optical simulations, a different pattern of the Γ distribution is obtained. Knowing the correct pattern of the Γ distribution around NPs is crucial for understanding the spectroscopic features of molecules inside hot spots. The enhancement produced by surface plasmon coupling is studied by using both approaches in NP dimers for different inter-particle distances. The results show that the trend of the variation of Γ versus inter-particle distance is different for classical and quantum simulations. This difference is explained in terms of a charge transfer mechanism that cannot be obtained with classical electrodynamics. Finally, time dependent distribution of the enhancement factor is simulated by introducing a time dependent field perturbation into the Hamiltonian, allowing an assessment of the localized surface plasmon resonance quantum dynamics.

  14. Additional Enhancement of Electric Field in Surface-Enhanced Raman Scattering due to Fresnel Mechanism

    PubMed Central

    Jayawardhana, Sasani; Rosa, Lorenzo; Juodkazis, Saulius; Stoddart, Paul R.

    2013-01-01

    Surface-enhanced Raman scattering (SERS) is attracting increasing interest for chemical sensing, surface science research and as an intriguing challenge in nanoscale plasmonic engineering. Several studies have shown that SERS intensities are increased when metal island film substrates are excited through a transparent base material, rather than directly through air. However, to our knowledge, the origin of this additional enhancement has never been satisfactorily explained. In this paper, finite difference time domain modeling is presented to show that the electric field intensity at the dielectric interface between metal particles is higher for “far-side” excitation than “near-side”. This is reasonably consistent with the observed enhancement for silver islands on SiO2. The modeling results are supported by a simple analytical model based on Fresnel reflection at the interface, which suggests that the additional SERS signal is caused by near-field enhancement of the electric field due to the phase shift at the dielectric interface. PMID:23903714

  15. High Temperature Piezoelectric Drill

    NASA Technical Reports Server (NTRS)

    Bao, Xiaoqi; Scott, James; Boudreau, Kate; Bar-Cohen, Yoseph; Sherrit, Stewart; Badescu, Mircea; Shrout, Tom; Zhang, Shujun

    2009-01-01

    The current NASA Decadal mission planning effort has identified Venus as a significant scientific target for a surface in-situ sampling/analyzing mission. The Venus environment represents several extremes including high temperature (460 deg C), high pressure (9 MPa), and potentially corrosive (condensed sulfuric acid droplets that adhere to surfaces during entry) environments. This technology challenge requires new rock sampling tools for these extreme conditions. Piezoelectric materials can potentially operate over a wide temperature range. Single crystals, like LiNbO3, have a Curie temperature that is higher than 1000 deg C and the piezoelectric ceramics Bismuth Titanate higher than 600 deg C. A study of the feasibility of producing piezoelectric drills that can operate in the temperature range up to 500 deg C was conducted. The study includes the high temperature properties investigations of engineering materials and piezoelectric ceramics with different formulas and doping. The drilling performances of a prototype Ultrasonic/Sonic Drill/Corer (USDC) using high temperate piezoelectric ceramics and single crystal were tested at temperature up to 500 deg C. The detailed results of our study and a discussion of the future work on performance improvements are presented in this paper.

  16. Evanescent field in surface plasmon resonance and surface plasmon field-enhanced fluorescence spectroscopies.

    PubMed

    Ekgasit, Sanong; Thammacharoen, Chuchaat; Yu, Fang; Knoll, Wolfgang

    2004-04-15

    The highly sensitive nature of surface plasmon resonance (SPR) spectroscopy and surface plasmon field-enhanced fluorescence spectroscopy (SPFS) are governed by the strong surface plasmon resonance-generated evanescent field at the metal/dielectric interface. The greatest evanescent field amplitude at the interface and the maximum attenuation of the reflectance are observed when a nonabsorbing dielectric is employed. An absorbing dielectric decreases the evanescent field enhancement at the interface. The SPR curve of an absorbing dielectric is characterized by a greater reflectance minimum and a broader curve, as compared to those of the nonabsorbing dielectric with the same refractive index. For a weakly absorbing dielectric, such as nanometer-thick surface-confined fluorophores, the absorption is too small to induce a significant change in the SPR curve. However, the presence of a minute amount of the fluorophore can be detected by the highly sensitive SPFS. The angle with the maximum fluorescence intensity of an SPFS curve is always smaller than the resonance angle of the corresponding SPR curve. This discrepancy is due to the differences of evanescent field distributions and their decay characteristics within the metal film and the dielectric medium. The fluorescence intensity in an SPFS curve can be expressed in terms of the evanescent field amplitude. Excellent correlations between the experimentally measured fluorescence intensities and the evanescent field amplitudes are observed.

  17. Polarization to the field enhancement by a gold dimer

    NASA Astrophysics Data System (ADS)

    Hong, Xin; Jin, Zheng

    2016-11-01

    Due to the effect of plasmonic coupling, gold nanoparticle dimers have been paid more attentions in bio-imaging. The coupling effect existing at the gap between a closely linked particle pair can make the local field strongly enhanced and in which the angle between the excitation polarization and the dimer axis plays a dominant role. We calculated the amplitude distribution under a highly focused illumination objective. The simulation results show that for such a model, 45 degrees between the excitation polarization and the dimer axis can produce an optimum signal. The enhancement thus obtained is 10.78 fold while the variation between peak-peak can reach 6.59 fold compared to a single plasmoic particle during the rotation of the polarization.

  18. Field emission theory for an enhanced surface potential: a model for carbon field emitters

    NASA Astrophysics Data System (ADS)

    Choy, T. C.; Harker, A. H.; Stoneham, A. M.

    2004-02-01

    We propose a non-JWKB-based theory of electron field emission for carbon field emitters in which, for electrons with energy in the vicinity of the order of ϑ to the Fermi level, the effective (1/x) surface potential is strongly enhanced. The model grossly violates the WKB validity criteria and necessitates an analytic treatment of the one-dimensional Schrödinger equation, which we first obtain. We determine ϑ (which is field-dependent) from the wavefunction matching point close to the surface. For reasonable values of the surface parameters—work function \\varphi \\approx 2 -5 eV, electron affinity \\chi \\approx 2 \\varphi and an empirical electron loss factor \\sigma \\approx 10^{-3} (and with no other adjustable parameters)—the theory provides an intriguing agreement with experimental data from carbon epoxy graphite composite (PFE) and certain graphitized carbon nanotube field emitters. We speculate on the surface potential enhancement, which can be interpreted as a massive (field-induced) dielectric effect of dynamic origin. This can be related via time-dependent perturbation theory to second-order non-linear polarizability enhancements at ultraviolet {\\sim }3000~\\AA wavelengths near the tunnelling region. Finally some exact mathematical results are included in the appendix for future reference.

  19. Differentiation of optical isomers through enhanced weak-field interactions

    NASA Technical Reports Server (NTRS)

    Aronowitz, S.

    1980-01-01

    The influence of weak field interaction terms due to the cooperative effects which arise from a macroscopic assemblage of interacting sites is studied. Differential adsorption of optical isomers onto an achiral surface is predicted to occur if the surface was continuous and sufficiently large. However, the quantity of discontinuous crystal surfaces did not enhance the percentage of differentiation and thus the procedure of using large quantities of small particles was not a viable technique for obtaining a detectable differentiation of optical isomers on an achiral surface.

  20. Field Testing of Nano-PCM Enhanced Building Envelope Components

    SciTech Connect

    Biswas, Kaushik; Childs, Phillip W; Atchley, Jerald Allen

    2013-08-01

    The U.S. Department of Energy s (DOE) Building Technologies Program s goal of developing high-performance, energy efficient buildings will require more cost-effective, durable, energy efficient building envelopes. Forty-eight percent of the residential end-use energy consumption is spent on space heating and air conditioning. Reducing envelope-generated heating and cooling loads through application of phase change material (PCM)-enhanced envelope components can facilitate maximizing the energy efficiency of buildings. Field-testing of prototype envelope components is an important step in estimating their energy benefits. An innovative phase change material (nano-PCM) was developed with PCM encapsulated with expanded graphite (interconnected) nanosheets, which is highly conducive for enhanced thermal storage and energy distribution, and is shape-stable for convenient incorporation into lightweight building components. During 2012, two test walls with cellulose cavity insulation and prototype PCM-enhanced interior wallboards were installed in a natural exposure test (NET) facility at Charleston, SC. The first test wall was divided into four sections, which were separated by wood studs and thin layers of foam insulation. Two sections contained nano-PCM-enhanced wallboards: one was a three-layer structure, in which nano-PCM was sandwiched between two gypsum boards, and the other one had PCM dispersed homogeneously throughout graphite nanosheets-enhanced gypsum board. The second test wall also contained two sections with interior PCM wallboards; one contained nano-PCM dispersed homogeneously in gypsum and the other was gypsum board containing a commercial microencapsulated PCM (MEPCM) for comparison. Each test wall contained a section covered with gypsum board on the interior side, which served as control or a baseline for evaluation of the PCM wallboards. The walls were instrumented with arrays of thermocouples and heat flux transducers. Further, numerical modeling of

  1. Piezoelectric micromotors for microrobots

    NASA Astrophysics Data System (ADS)

    Flynn, Anita M.; Tavrow, Lee S.; Bart, Stephen F.; Brooks, Rodney A.

    1991-02-01

    Mobile robots are able to carry more and more intelligence (and in smaller packages) onboard everyday. Now we would like to match the brawn of our robots to the same scale as the brain. Towards this end, we have fabricated some small, a few millimeters in diameter, piezoelectric motors using ferroelectric thin films. These motors consist of two pieces: a stator and a rotor. The stationary stator includes a piezoelectric film in which we induce bending in the form of a traveling wave. Anything which sits atop the stator is propelled by the wave. A small glass lens placed upon the stator becomes the spinning rotor. Piezoelectric micromotors overcome the problems currently associated with electrostatic micromotors such as low torque, friction, and the need for high voltage excitation.

  2. Enhanced germination and gravitropism of soybean in a hypogeomagnetic field

    NASA Astrophysics Data System (ADS)

    Mo, Weichuan

    For the future manned space exploration, the duration of the missions would significantly in-crease. Investigating plant growth and development under the space environmental conditions is of essential importance for the food supply projects for the astronauts. Hypogeomagnetic field (HGMF), namely, extremely low magnetic field, is one of the main characters of the space environment. Germination is the first vital step of plant growth and development, which determines the final yield of plants. The effect of HGMF on plant growth, especially early ger-mination, still remains open. In this study, we established a hypogeomagnetic field (HGMF) incubation system, the remnant magnetic field inside no more than 250 nT. Soybean seeds were incubated at 25 in HGMF, and the very beginning of soybean germination, from water ab-sorbance of cotyledon to radicle emergence, was examined within 24 h. Our results showed that the germination ratio and weight ratio of emerged soybean radicles were markedly increased during germination in HGMF. Furthermore, the tropism angle of emerged radicle with gravity in HGMF was statistically smaller than that in GMF when the radicle direction was placed opposite to gravity before germination. These results indicate that the germination and gravit-ropism of soybean is enhanced in a hypogeomagnetic environment, This is a new finding about the early seed germination in such a low environmental magnetic field which is comparable to the magnetic field of Lunar Swirls on the Moon (a few hundred nT), and it might provide new perspectives on the space science researches concerning plant growth and food supply.

  3. Piezoelectric allostery of protein

    NASA Astrophysics Data System (ADS)

    Ohnuki, Jun; Sato, Takato; Takano, Mitsunori

    2016-07-01

    Allostery is indispensable for a protein to work, where a locally applied stimulus is transmitted to a distant part of the molecule. While the allostery due to chemical stimuli such as ligand binding has long been studied, the growing interest in mechanobiology prompts the study of the mechanically stimulated allostery, the physical mechanism of which has not been established. By molecular dynamics simulation of a motor protein myosin, we found that a locally applied mechanical stimulus induces electrostatic potential change at distant regions, just like the piezoelectricity. This novel allosteric mechanism, "piezoelectric allostery", should be of particularly high value for mechanosensor/transducer proteins.

  4. Analysis and Testing of Plates with Piezoelectric Sensors and Actuators

    NASA Technical Reports Server (NTRS)

    Bevan, Jeffrey S.

    1998-01-01

    Piezoelectric material inherently possesses coupling between electrostatics and structural dynamics. Utilizing linear piezoelectric theory results in an intrinsically coupled pair of piezoelectric constitutive equations. One equation describes the direct piezoelectric effect where strains produce an electric field and the other describes the converse effect where an applied electrical field produces strain. The purpose of this study is to compare finite element analysis and experiments of a thin plate with bonded piezoelectric material. Since an isotropic plate in combination with a thin piezoelectric layer constitutes a special case of a laminated composite, the classical laminated plate theory is used in the formulation to accommodated generic laminated composite panels with multiple bonded and embedded piezoelectric layers. Additionally, the von Karman large deflection plate theory is incorporated. The formulation results in laminate constitutive equations that are amiable to the inclusion of the piezoelectric constitutive equations yielding in a fully electro-mechanically coupled composite laminate. Using the finite element formulation, the governing differential equations of motion of a composite laminate with embedded piezoelectric layers are derived. The finite element model not only considers structural degrees of freedom (d.o.f.) but an additional electrical d.o.f. for each piezoelectric layer. Comparison between experiment and numerical prediction is performed by first treating the piezoelectric as a sensor and then again treating it as an actuator. To assess the piezoelectric layer as a sensor, various uniformly distributed pressure loads were simulated in the analysis and the corresponding generated voltages were calculated using both linear and nonlinear finite element analyses. Experiments were carried out by applying the same uniformly distributed loads and measuring the resulting generated voltages and corresponding maximum plate deflections. It is

  5. Enhancement and suppression in the visual field under perceptual load.

    PubMed

    Parks, Nathan A; Beck, Diane M; Kramer, Arthur F

    2013-01-01

    The perceptual load theory of attention proposes that the degree to which visual distractors are processed is a function of the attentional demands of a task-greater demands increase filtering of irrelevant distractors. The spatial configuration of such filtering is unknown. Here, we used steady-state visual evoked potentials (SSVEPs) in conjunction with time-domain event-related potentials (ERPs) to investigate the distribution of load-induced distractor suppression and task-relevant enhancement in the visual field. Electroencephalogram (EEG) was recorded while subjects performed a foveal go/no-go task that varied in perceptual load. Load-dependent distractor suppression was assessed by presenting a contrast reversing ring at one of three eccentricities (2, 6, or 11°) during performance of the go/no-go task. Rings contrast reversed at 8.3 Hz, allowing load-dependent changes in distractor processing to be tracked in the frequency-domain. ERPs were calculated to the onset of stimuli in the load task to examine load-dependent modulation of task-relevant processing. Results showed that the amplitude of the distractor SSVEP (8.3 Hz) was attenuated under high perceptual load (relative to low load) at the most proximal (2°) eccentricity but not at more eccentric locations (6 or 11°). Task-relevant ERPs revealed a significant increase in N1 amplitude under high load. These results are consistent with a center-surround configuration of load-induced enhancement and suppression in the visual field.

  6. Piezoelectric PU/PVDF electrospun scaffolds for wound healing applications.

    PubMed

    Guo, Hong-Feng; Li, Zhen-Sheng; Dong, Shi-Wu; Chen, Wei-Jun; Deng, Ling; Wang, Yu-Fei; Ying, Da-Jun

    2012-08-01

    Previous studies have shown that piezoelectric materials may be used to prepare bioactive electrically charged surfaces. In the current study, polyurethane/polyvinylidene fluoride (PU/PVDF) scaffolds were prepared by electrospinning. The mechanical property and piezoelectric property of the scaffolds were evaluated. The crystalline phase of PVDF in the scaffolds was characterised by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). In vitro cell culture was performed to investigate cytocompatibility of the scaffolds. Wound-healing assay, cell-adhesion assay, quantitative RT-PCR and Western blot analyses were performed to investigate piezoelectric effect of the scaffolds on fibroblast activities. Further, the scaffolds were subcutaneously implanted in Sprague-Dawley (SD) rats to investigate their biocompatibility and the piezoelectric effect on fibrosis in vivo. The results indicated that the electrospinning process had changed PVDF crystalline phase from the nonpiezoelectric α phase to the piezoelectric β phase. The fibroblasts cultured on the scaffolds showed normal morphology and proliferation. The fibroblasts cultured on the piezoelectric-excited scaffolds showed enhanced migration, adhesion and secretion. The scaffolds that were subcutaneously implanted in SD rats showed higher fibrosis level due to the piezoelectrical stimulation, which was caused by random animal movements followed by mechanical deformation of the scaffolds. The scaffolds are potential candidates for wound healing applications.

  7. Piezoelectric Nanoparticle-Polymer Composite Materials

    NASA Astrophysics Data System (ADS)

    McCall, William Ray

    Herein we demonstrate that efficient piezoelectric nanoparticle-polymer composite materials can be synthesized and fabricated into complex microstructures using sugar-templating methods or optical printing techniques. Stretchable foams with excellent tunable piezoelectric properties are created by incorporating sugar grains directly into polydimethylsiloxane (PDMS) mixtures containing barium titanate (BaTiO3 -- BTO) nanoparticles and carbon nanotubes (CNTs), followed by removal of the sugar after polymer curing. Porosities and elasticity are tuned by simply adjusting the sugar/polymer mass ratio and the electrical performance of the foams showed a direct relationship between porosity and the piezoelectric outputs. User defined 2D and 3D optically printed piezoelectric microstructures are also fabricated by incorporating BTO nanoparticles into photoliable polymer solutions such as polyethylene glycol diacrylate (PEGDA) and exposing to digital optical masks that can be dynamically altered. Mechanical-to-electrical conversion efficiency of the optically printed composite is enhanced by chemically altering the surface of the BTO nanoparticles with acrylate groups which form direct covalent linkages with the polymer matrix under light exposure. Both of these novel materials should find exciting uses in a variety of applications including energy scavenging platforms, nano- and microelectromechanical systems (NEMS/MEMS), sensors, and acoustic actuators.

  8. Origin of enhanced field emission characteristics postplasma treatment of multiwalled carbon nanotube array

    SciTech Connect

    Lee, Kyu; Lim, Seong Chu; Lee, Young Hee; Choi, Young Chul

    2008-08-11

    Field emission properties of chemical-vapor-deposition-grown multiwalled carbon nanotubes (MWCNTs) with plasma treatment have been investigated. Origin of the enhanced field emission current was interpreted in terms of surface morphology of MWCNTs, work function, field enhancement factor, and emission area. Contrary to the general belief, the change in the work function increased slightly with the plasma treatment time, whereas the field enhancement factor decreased. We found that the number of emittable MWCNTs played a dominant role in the current enhancement.

  9. UHV piezoelectric translator

    SciTech Connect

    Oversluizen, T.; Watson, G.

    1985-01-01

    A UHV compatible piezoelectric translator has been developed to correct for angular misalignments in the crysals of a UHV x-ray monochromator. The unit is small, bakeable to 150/sup 0/C, and uses only ceramic materials for insulation. We report on the construction details, vacuum compatibility, mechanical properties, and uses of the device.

  10. Piezoelectric actuator renaissance

    NASA Astrophysics Data System (ADS)

    Uchino, Kenji

    2015-03-01

    This paper resumes the content of the invited talk of the author, read at the occasion of the International Workshop on Relaxor Ferroelectrics, IWRF 14, held on October 12-16, 2014 in Stirin, Czech Republic. It reviews the recent advances in materials, designing concepts, and new applications of piezoelectric actuators, as well as the future perspectives of this area.

  11. Interaction between a piezoelectric screw dislocation and a finite crack with surface piezoelectricity

    NASA Astrophysics Data System (ADS)

    Wang, Xu; Xu, Yang

    2015-12-01

    We analytically investigate the contribution of surface piezoelectricity to the interaction between a piezoelectric screw dislocation and a finite crack in a hexagonal piezoelectric solid. The piezoelectric screw dislocation suffers jumps in the displacement and in the electric potential across the slip plane, and meanwhile it is subjected to a line force and a line charge at its core. The original boundary value problem is reduced to two sets of coupled first-order Cauchy singular integro-differential equations by considering a distribution of line dislocations, electric-potential-dislocations, line forces and line charges on the crack. By using a diagonalization method, the two sets of equations are decoupled into four independent singular integro-differential equations, each of which can be numerically solved by means of the collocation method. Our analysis reveals that in general the stresses, strains, electric displacements and electric fields exhibit both the weak logarithmic and the strong square root singularities at the two crack tips. The image force acting on the piezoelectric screw dislocation due to its interaction with the finite crack is calculated.

  12. Surface micromachined differential piezoelectric shear-stress sensors

    NASA Astrophysics Data System (ADS)

    Williams, Randall P.; Kim, Donghwan; Gawalt, David P.; Hall, Neal A.

    2017-01-01

    The ability to measure viscous wall shear stress in high-speed flows is important for verifying simulated results typically obtained from direct numerical simulation in the aerodynamics research community, and robust sensors are required to measure wall shear reliably under such high-speed conditions. This letter summarizes the design, fabrication, and testing of a surface micromachined piezoelectric shear-stress sensor which uses a thin piezoelectric film to generate a voltage proportional to an applied shear stress without additional moving parts. A differential-cell architecture is used to enhance selectivity to shear stress while canceling normal-stress sensitivity. The conceptual design, fabrication details, and experimental measurements of device sensitivity are presented. A finite element model is used to validate the device performance against measurements, and to provide insight into the potential and electric fields underlying the device concept. The potential for understanding device behavior and optimization through modeling is illustrated using finite element analysis results. The minimum detectable shear stress for the sensor is estimated to be 52.9 mPa  √Hz-1 at 1.5 kHz.

  13. Challenges and New Trends for Piezoelectric Actuators

    NASA Technical Reports Server (NTRS)

    Sehirlioglu, Alp

    2008-01-01

    BiScO3-PbTiO3 ceramics with TC greater than 400 C has been successfully processed. Despite the increase in TC, excess Pb addition increases both the bulk conductivity and the grain boundary contribution to conductivity at elevated temperatures. Conductivity at elevated temperatures, that limits the operating temperature for actuators, has been greatly reduced by excess Bi additions. Excess Bi doping improves poling conditions resulting in enhanced piezoelectric coefficient (d(sub 33) = 408 pC/N).

  14. Spectrally Enhanced Lighting Program Implementation for Energy Savings: Field Evaluation

    SciTech Connect

    Gordon, Kelly L.; Sullivan, Gregory P.; Armstrong, Peter R.; Richman, Eric E.; Matzke, Brett D.

    2006-08-22

    This report provides results from an evaluation PNNL conducted of a spectrally enhanced lighting demonstration project. PNNL performed field measurements and occupant surveys at three office buildings in California before and after lighting retrofits were made in August and December 2005. PNNL measured the following Overhead lighting electricity demand and consumption, Light levels in the workspace, Task lighting use, and Occupant ratings of satisfaction with the lighting. Existing lighting, which varied in each building, was replaced with lamps with correlated color temperature (CCT) of 5000 Kelvin, color rendering index (CRI) of 85, of varying wattages, and lower ballast factor electronic ballasts. The demonstrations were designed to decrease lighting power loads in the three buildings by 22-50 percent, depending on the existing installed lamps and ballasts. The project designers hypothesized that this reduction in electrical loads could be achieved by the change to higher CCT lamps without decreasing occupant satisfaction with the lighting.

  15. Enhancement and suppression in the visual field under perceptual load

    PubMed Central

    Parks, Nathan A.; Beck, Diane M.; Kramer, Arthur F.

    2013-01-01

    The perceptual load theory of attention proposes that the degree to which visual distractors are processed is a function of the attentional demands of a task—greater demands increase filtering of irrelevant distractors. The spatial configuration of such filtering is unknown. Here, we used steady-state visual evoked potentials (SSVEPs) in conjunction with time-domain event-related potentials (ERPs) to investigate the distribution of load-induced distractor suppression and task-relevant enhancement in the visual field. Electroencephalogram (EEG) was recorded while subjects performed a foveal go/no-go task that varied in perceptual load. Load-dependent distractor suppression was assessed by presenting a contrast reversing ring at one of three eccentricities (2, 6, or 11°) during performance of the go/no-go task. Rings contrast reversed at 8.3 Hz, allowing load-dependent changes in distractor processing to be tracked in the frequency-domain. ERPs were calculated to the onset of stimuli in the load task to examine load-dependent modulation of task-relevant processing. Results showed that the amplitude of the distractor SSVEP (8.3 Hz) was attenuated under high perceptual load (relative to low load) at the most proximal (2°) eccentricity but not at more eccentric locations (6 or 11°). Task-relevant ERPs revealed a significant increase in N1 amplitude under high load. These results are consistent with a center-surround configuration of load-induced enhancement and suppression in the visual field. PMID:23734135

  16. Elastodynamic cloaking and field enhancement for soft spheres

    NASA Astrophysics Data System (ADS)

    Diatta, Andre; Guenneau, Sebastien

    2016-11-01

    We propose a spherical cloak described by a non-singular asymmetric elasticity tensor {C} depending upon a small parameter η, that defines the softness of a region one would like to conceal from elastodynamic waves. By varying η, we generate a class of soft spheres dressed by elastodynamic cloaks, which are shown to considerably reduce the scattering of the soft spheres. Importantly, such cloaks also provide some wave protection except for a countable set of frequencies, for which some large elastic field enhancement can be observed within the soft spheres. Through an investigation of trapped modes in elasticity, we supply a good approximation of such Mie-type resonances by some transcendental equation. Our results, unlike previous studies that focused merely on the invisibility aspects, shed light on potential pitfalls of elastodynamic cloaks for earthquake protection designed via geometric transforms: a seismic cloak needs to be designed in such a way that its inner resonances differ from eigenfrequencies of the building one wishes to protect. In order to circumvent this downfall of field enhancement inside the cloaked area, we introduce a novel generation of cloaks, named here, mixed cloaks. Such mixed cloaks consist of a shell that detours incoming waves, hence creating an invisibility region, and of a perfectly matched layer (PML, located at the inner boundary of the cloaks) that absorbs residual wave energy in such a way that aforementioned resonances in the soft sphere are strongly attenuated. The designs of mixed cloaks with a non-singular elasticity tensor combined with an inner PML and non-vanishing density bring seismic cloaks one step closer to a practical implementation. Note in passing that the concept of mixed cloaks also applies in the case of singular cloaks and can be translated in other wave areas for a similar purpose (i.e. to smear down inner resonances within the invisibility region).

  17. Electric field enhanced dropwise condensation on hydrophobic surfaces

    NASA Astrophysics Data System (ADS)

    Baratian, Davood; Hoek, Harmen; van den Ende, Dirk; Mugele, Frieder; Physics of Complex Fluids Team

    2016-11-01

    Dropwise condensation occurs when vapor condenses on a low surface energy surface, and the substrate is just partially wetted by the condensate. Dropwise condensation has attracted significant attention due to its reported superior heat transfer performance compared to filmwise condensation. Extensive research efforts are focused on how to promote, and enhance dropwise condensation by considering both physical and chemical factors. We have studied electrowetting-actuated condensation on hydrophobic surfaces, aiming for enhancement of heat transfer in dropwise condensation. The idea is to use suitably structured patterns of micro-electrodes that generate a heterogeneous electric field at the interface and thereby promote both the condensation itself and the shedding of condensed drops. Comforting the shedding of droplets on electrowetting-functionalized surfaces allows more condensing surface area for re-nucleation of small droplets, leading to higher condensation rates. Possible applications of this innovative concept include heat pipes for (micro) coolers in electronics as well as in more efficient heat exchangers. We acknowledge financial support by the Dutch Technology Foundation STW, which is part of the Netherlands Organization for Scientific Research (NWO), within the VICI program.

  18. Hole transport assisted by the piezoelectric field in In{sub 0.4}Ga{sub 0.6}N/GaN quantum wells under electrical injection

    SciTech Connect

    Zhang, Shuailong; Gu, Erdan E-mail: huxd@pku.edu.cn; Xie, Enyuan; Herrnsdof, Johannes; Gong, Zheng; Watson, Ian M.; Dawson, Martin D.; Yan, Tongxing; Yang, Wei; Hu, Xiaodong E-mail: huxd@pku.edu.cn

    2015-09-28

    The authors observe the significant penetration of electrically injected holes through InGaN/GaN quantum wells (QWs) with an indium mole fraction of 40%. This effect and its current density dependence were analysed by studies on micro-pixel light-emitting diodes, which allowed current densities to be varied over a wide range up to 5 kA/cm{sup 2}. The systematic changes in electroluminescence spectra are discussed in the light of the piezoelectric field in the high-indium-content QWs and its screening by the carriers. Simulations were also carried out to clarify the unusual hole transport mechanism and the underlying physics in these high-indium QWs.

  19. Field-enhanced electrodes for additive-injection non-thermal plasma (NTP) processor

    DOEpatents

    Rosocha, Louis A.; Ferreri, Vincent; Kim, Yongho

    2009-04-21

    The present invention comprises a field enhanced electrode package for use in a non-thermal plasma processor. The field enhanced electrode package includes a high voltage electrode and a field-enhancing electrode with a dielectric material layer disposed in-between the high voltage electrode and the field-enhancing electrode. The field-enhancing electrode features at least one raised section that includes at least one injection hole that allows plasma discharge streamers to occur primarily within an injected additive gas.

  20. The Heliocentric Variation of the Properties of Interplanetary Field Enhancement

    NASA Astrophysics Data System (ADS)

    Lai, H.; Russell, C. T.; Wei, H.; Zhang, T.

    2013-05-01

    Interplanetary Field Enhancements (IFEs) are increases of the interplanetary magnetic field usually to a sharp maximum and containing a current sheet near the center of the event. They have been observed at Helios and MESSENGER as close as 0.3 AU to the Sun, at VEX and PVO at 0.72 AU; at STEREO, ACE, Wind, Geotail, ARTEMIS at 1 AU and Ulysses from 1 to 5 AU. Our model for the physical mechanism for creating these disturbances is that collisions of bodies in the size range 10 - 1000m are catastrophically disrupted by a collision with a fast moving smaller object. The rate of detection of IFEs is dependent on heliocentric range increasing closer to the Sun. There are several possible reasons for this increase which we explore. The mass of the dust cloud that is picked up is significant about 108kg. The magnetic gradient force of the IFE is large enough to lift this mass through the Sun's gravitational potential wall. The momentum transfer that enables this outward transport is a small fraction of the solar wind momentum flux but this transfer can be detected using superposed epoch studies of the solar wind, and is consistent with the hypothesis. We note that the rate of IFE observations in the Helios and MESSENGER data at 0.3 AU is less than expected from extrapolating the observations at and beyond 0.7 AU. This result can soon be extended closer to the Sun with Solar Orbiter and Solar Probe Plus.

  1. Melamine sensing based on evanescent field enhanced optical fiber sensor

    NASA Astrophysics Data System (ADS)

    Luo, Ji; Yao, Jun; Wang, Wei-min; Zhuang, Xu-ye; Ma, Wen-ying; Lin, Qiao

    2013-08-01

    Melamine is an insalubrious chemical, and has been frequently added into milk products illegally, to make the products more protein-rich. However, it can cause some various diseases, such as kidney stones and bladder cancer. In this paper, a novel optical fiber sensor with high sensitivity based on absorption of the evanescent field for melamine detection is successfully proposed and developed. Different concentrations of melamine changing from 0 to 10mg/mL have been detected using the micro/nano-sensing fiber decorated with silver nanoparticles cluster layer. As the concentration increases, the sensing fiber's output intensity gradually deceases and the absorption of the analyte becomes large. The concentration changing of 1mg/ml can cause the absorbance varying 0.664 and the limit of the melamine detectable concentration is 1ug/mL. Besides, the coupling properties between silver nanoparticles have also been analyzed by the FDTD method. Overall, this evanescent field enhanced optical fiber sensor has potential to be used in oligo-analyte detection and will promote the development of biomolecular and chemical sensing applications.

  2. Electromagnetic field enhancement and light localization in deterministic aperiodic nanostructures

    NASA Astrophysics Data System (ADS)

    Gopinath, Ashwin

    The control of light matter interaction in periodic and random media has been investigated in depth during the last few decades, yet structures with controlled degree of disorder such as Deterministic Aperiodic Nano Structures (DANS) have been relatively unexplored. DANS are characterized by non-periodic yet long-range correlated (deterministic) morphologies and can be generated by the mathematical rules of symbolic dynamics and number theory. In this thesis, I have experimentally investigated the unique light transport and localization properties in planar dielectric and metal (plasmonics) DANS. In particular, I have focused on the design, nanofabrication and optical characterization of DANS, formed by arranging metal/dielectric nanoparticles in an aperiodic lattice. This effort is directed towards development of on-chip nanophotonic applications with emphasis on label-free bio-sensing and enhanced light emission. The DANS designed as Surface Enhanced Raman Scattering (SERS) substrate is composed of multi-scale aperiodic nanoparticle arrays fabricated by e-beam lithography and are capable of reproducibly demonstrating enhancement factors as high as ˜107. Further improvement of SERS efficiency is achieved by combining DANS formed by top-down approach with bottom-up reduction of gold nanoparticles, to fabricate novel nanostructures called plasmonic "nano-galaxies" which increases the SERS enhancement factors by 2--3 orders of magnitude while preserving the reproducibility. In this thesis, along with presenting details of fabrication and SERS characterization of these "rationally designed" SERS substrates, I will also present results on using these substrates for detection of DNA nucleobases, as well as reproducible label-free detection of pathogenic bacteria with species specificity. In addition to biochemical detection, the combination of broadband light scattering behavior and the ability for the generation of reproducible high fields in DANS make these

  3. Improvement of efficiency of piezoelectric element attached to beam based on mechanical impedance matching

    NASA Astrophysics Data System (ADS)

    Yamada, Keisuke; Matsuhisa, Hiroshi; Utsuno, Hideo

    2014-01-01

    This paper describes new methods that improve the efficiency of a piezoelectric element attached to a beam based on mechanical impedance matching. Piezoelectric elements are often used to suppress bending vibration. They are also used as sensors or energy-harvesting sources. In such cases, the piezoelectric element is usually bonded onto the host structure by an adhesive bond. The efficiency of the piezoelectric element depends on the bonding location. When the efficiency is insufficient despite a good location, the size or number of piezoelectric elements is increased. However, the efficiency of the piezoelectric element is usually insufficient even if these methods are applied. In order to enhance the efficiency of the piezoelectric elements without using active methods, this paper proposes a mechanical impedance matching method that uses spacers or tuning for the size of the piezoelectric element. Because the attached piezoelectric element and host structure in this region behave as springs in parallel to the bending deformation, the stored strain energy in the piezoelectric element is maximized under the condition that their spring constants match. The proposed methods were theoretically investigated with consideration for the effects of the bonding layer, spacers, and host structure. The optimum conditions for the proposed methods were theoretically formulated, and the effectiveness of the proposed methods and theoretical analysis was verified through simulations and experiments.

  4. Tonpilz Piezoelectric Transducer with a Bending Piezoelectric Disk on The Radiation Surface

    NASA Astrophysics Data System (ADS)

    Yamamoto, Mitsuru; Shiba, Hiroshi; Fujii, Taro; Hama, Yoshinori; Hoshino, Takamichi; Inoue, Takeshi

    2003-05-01

    In recent years, it has become necessary to use wide-band signals in various kinds of signal processing and communication technology fields. One of these is the field of underwater acoustic technology, and therefore wide-band transducers are needed in this field. To address this need, we developed a Tonpilz piezoelectric transducer with a bending piezoelectric disk on the radiation surface of the front mass. This transducer was designed by providing a bending piezoelectric disk on the radiation surface of the front mass of a conventional Tonpilz piezoelectric transducer to enable it to generate in two resonance modes: the longitudinal vibration resonance mode and the bending vibration resonance mode of the bending disk. Coupling these two resonance modes makes it possible to achieve low-frequency transmission, and wide-band signals can be attained by adjusting the phase in the two modes. We obtained the optimum design dimensions of the transducer through analysis using the finite element method (FEM), and constructed a prototype based on the analysis. Experiments verified that the measured results for the prototype correspond well to the simulation results and that the bandwidth can be widened without changing the external size of the conventional transducer.

  5. A model for effective field enhancement for Fowler-Nordheim field emission

    SciTech Connect

    Feng, Y.; Verboncoeur, J.P.

    2005-10-01

    The local field enhancement factor {beta} is often introduced in the Fowler-Nordheim equation to represent the geometrical effects at the surface of the cathode, where {beta}(s)=E{sub n}(s)/E{sub 0} for macroscopic applied field E{sub 0}. Local variation of {beta} determines the local normal surface electric field, E{sub n}(s), resulting in local dependence of injection current by the Fowler-Nordheim law. In computational models, it is impractical to determine the time-dependent local surface field each time step on a microscopic space scale. Effective {beta} is introduced in this paper which allows us to study the emission properties at a macroscopic scale. Microscopic (subgrid) local effective {beta} is calculated only at the initial time step, and then the effective {beta} can be recomputed for different surface electrical field through this model. The model allows reduction of dimensionality as well as the ability to include subgrid effects. The model is demonstrated on fundamental cases and compared to a calculation with a mesh fine enough to resolve the geometric features.

  6. Piezoelectric Resonator with Two Layers

    NASA Technical Reports Server (NTRS)

    Stephanou, Philip J. (Inventor); Black, Justin P. (Inventor)

    2013-01-01

    A piezoelectric resonator device includes: a top electrode layer with a patterned structure, a top piezoelectric layer adjacent to the top layer, a middle metal layer adjacent to the top piezoelectric layer opposite the top layer, a bottom piezoelectric layer adjacent to the middle layer opposite the top piezoelectric layer, and a bottom electrode layer with a patterned structure and adjacent to the bottom piezoelectric layer opposite the middle layer. The top layer includes a first plurality of electrodes inter-digitated with a second plurality of electrodes. A first one of the electrodes in the top layer and a first one of the electrodes in the bottom layer are coupled to a first contact, and a second one of the electrodes in the top layer and a second one of the electrodes in the bottom layer are coupled to a second contact.

  7. Piezoelectric step-motion actuator

    DOEpatents

    Mentesana; Charles P.

    2006-10-10

    A step-motion actuator using piezoelectric material to launch a flight mass which, in turn, actuates a drive pawl to progressively engage and drive a toothed wheel or rod to accomplish stepped motion. Thus, the piezoelectric material converts electrical energy into kinetic energy of the mass, and the drive pawl and toothed wheel or rod convert the kinetic energy of the mass into the desired rotary or linear stepped motion. A compression frame may be secured about the piezoelectric element and adapted to pre-compress the piezoelectric material so as to reduce tensile loads thereon. A return spring may be used to return the mass to its resting position against the compression frame or piezoelectric material following launch. Alternative embodiment are possible, including an alternative first embodiment wherein two masses are launched in substantially different directions, and an alternative second embodiment wherein the mass is eliminated in favor of the piezoelectric material launching itself.

  8. Planar Rotary Piezoelectric Motor Using Ultrasonic Horns

    NASA Technical Reports Server (NTRS)

    Sherrit, Stewart; Bao, Xiaoqi; Badescu, Mircea; Bar-Cohen, Yoseph; Geiyer, Daniel; Ostlund, Patrick N.; Allen, Phillip

    2011-01-01

    A motor involves a simple design that can be embedded into a plate structure by incorporating ultrasonic horn actuators into the plate. The piezoelectric material that is integrated into the horns is pre-stressed with flexures. Piezoelectric actuators are attractive for their ability to generate precision high strokes, torques, and forces while operating under relatively harsh conditions (temperatures at single-digit K to as high as 1,273 K). Electromagnetic motors (EM) typically have high rotational speed and low torque. In order to produce a useful torque, these motors are geared down to reduce the speed and increase the torque. This gearing adds mass and reduces the efficiency of the EM. Piezoelectric motors can be designed with high torques and lower speeds directly without the need for gears. Designs were developed for producing rotary motion based on the Barth concept of an ultrasonic horn driving a rotor. This idea was extended to a linear motor design by having the horns drive a slider. The unique feature of these motors is that they can be designed in a monolithic planar structure. The design is a unidirectional motor, which is driven by eight horn actuators, that rotates in the clockwise direction. There are two sets of flexures. The flexures around the piezoelectric material are pre-stress flexures and they pre-load the piezoelectric disks to maintain their being operated under compression when electric field is applied. The other set of flexures is a mounting flexure that attaches to the horn at the nodal point and can be designed to generate a normal force between the horn tip and the rotor so that to first order it operates independently and compensates for the wear between the horn and the rotor.

  9. Static aeroelastic behavior of an adaptive laminated piezoelectric composite wing

    NASA Technical Reports Server (NTRS)

    Weisshaar, T. A.; Ehlers, S. M.

    1990-01-01

    The effect of using an adaptive material to modify the static aeroelastic behavior of a uniform wing is examined. The wing structure is idealized as a laminated sandwich structure with piezoelectric layers in the upper and lower skins. A feedback system that senses the wing root loads applies a constant electric field to the piezoelectric actuator. Modification of pure torsional deformaton behavior and pure bending deformation are investigated, as is the case of an anisotropic composite swept wing. The use of piezoelectric actuators to create an adaptive structure is found to alter static aeroelastic behavior in that the proper choice of the feedback gain can increase or decrease the aeroelastic divergence speed. This concept also may be used to actively change the lift effectiveness of a wing. The ability to modify static aeroelastic behavior is limited by physical limitations of the piezoelectric material and the manner in which it is integrated into the parent structure.

  10. Improved Piezoelectric Loudspeakers And Transducers

    NASA Technical Reports Server (NTRS)

    Regan, Curtis Randall; Jalink, Antony; Hellbaum, Richard F.; Rohrbach, Wayne W.

    1995-01-01

    Loudspeakers and related acoustic transducers of improved type feature both light weight and energy efficiency of piezoelectric transducers and mechanical coupling efficiency. Active component of transducer made from wafer of "rainbow" piezoelectric material, ceramic piezoelectric material chemically reduced on one face. Chemical treatment forms wafer into dishlike shallow section of sphere. Both faces then coated with electrically conductive surface layers serving as electrodes. Applications include high-fidelity loudspeakers, and underwater echo ranging devices.

  11. High Temperature Piezoelectric Drill

    NASA Technical Reports Server (NTRS)

    Bao, Xiaoqi; Bar-Cohen, Yoseph; Sherrit, Stewart; Badescu, Mircea; Shrout, Tom

    2012-01-01

    Venus is one of the planets in the solar systems that are considered for potential future exploration missions. It has extreme environment where the average temperature is 460 deg C and its ambient pressure is about 90 atm. Since the existing actuation technology cannot maintain functionality under the harsh conditions of Venus, it is a challenge to perform sampling and other tasks that require the use of moving parts. Specifically, the currently available electromagnetic actuators are limited in their ability to produce sufficiently high stroke, torque, or force. In contrast, advances in developing electro-mechanical materials (such as piezoelectric and electrostrictive) have enabled potential actuation capabilities that can be used to support such missions. Taking advantage of these materials, we developed a piezoelectric actuated drill that operates at the temperature range up to 500 deg C and the mechanism is based on the Ultrasonic/Sonic Drill/Corer (USDC) configuration. The detailed results of our study are presented in this paper

  12. Enhanced Soundings for Local Coupling Studies Field Campaign Report

    SciTech Connect

    Ferguson, Craig R; Santanello, Joseph A; Gentine, Pierre

    2016-04-01

    This document presents initial analyses of the enhanced radiosonde observations obtained during the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility Enhanced Soundings for Local Coupling Studies Field Campaign (ESLCS), which took place at the ARM Southern Great Plains (SGP) Central Facility (CF) from June 15 to August 31, 2015. During ESLCS, routine 4-times-daily radiosonde measurements at the ARM-SGP CF were augmented on 12 days (June 18 and 29; July 11, 14, 19, and 26; August 15, 16, 21, 25, 26, and 27) with daytime 1-hourly radiosondes and 10-minute ‘trailer’ radiosondes every 3 hours. These 12 intensive operational period (IOP) days were selected on the basis of prior-day qualitative forecasts of potential land-atmosphere coupling strength. The campaign captured 2 dry soil convection advantage days (June 29 and July 14) and 10 atmospherically controlled days. Other noteworthy IOP events include: 2 soil dry-down sequences (July 11-14-19 and August 21-25-26), a 2-day clear-sky case (August 15-16), and the passing of Tropical Storm Bill (June 18). To date, the ESLCS data set constitutes the highest-temporal-resolution sampling of the evolution of the daytime planetary boundary layer (PBL) using radiosondes at the ARM-SGP. The data set is expected to contribute to: 1) improved understanding and modeling of the diurnal evolution of the PBL, particularly with regard to the role of local soil wetness, and (2) new insights into the appropriateness of current ARM-SGP CF thermodynamic sampling strategies.

  13. Piezoelectric Pulsed Microjets

    DTIC Science & Technology

    2011-04-29

    hydraulic fluid flow within the cylinder head, and hyperelastic stress-strain behavior of the top diaphragm that is coupled to the hydraulic pressure...displacement due to the form of the hyperelastic constitutive equation used to describe its deformation. The input operator, [B(u)](t), is written as a...piezoelectric response. Based on previous experiments, the nylon polymer deforms with the stack without any significant reduction in stack actuator

  14. Hybrid piezoelectric energy harvesting transducer system

    NASA Technical Reports Server (NTRS)

    Xu, Tian-Bing (Inventor); Jiang, Xiaoning (Inventor); Su, Ji (Inventor); Rehrig, Paul W. (Inventor); Hackenberger, Wesley S. (Inventor)

    2008-01-01

    A hybrid piezoelectric energy harvesting transducer system includes: (a) first and second symmetric, pre-curved piezoelectric elements mounted separately on a frame so that their concave major surfaces are positioned opposite to each other; and (b) a linear piezoelectric element mounted separately on the frame and positioned between the pre-curved piezoelectric elements. The pre-curved piezoelectric elements and the linear piezoelectric element are spaced from one another and communicate with energy harvesting circuitry having contact points on the frame. The hybrid piezoelectric energy harvesting transducer system has a higher electromechanical energy conversion efficiency than any known piezoelectric transducer.

  15. The quantum mechanics of ion-enhanced field emission and how it influences microscale gas breakdown

    SciTech Connect

    Li, Yingjie; Go, David B.

    2014-09-14

    The presence of a positive gas ion can enhance cold electron field emission by deforming the potential barrier and increasing the tunneling probability of electrons—a process known as ion-enhanced field emission. In microscale gas discharges, ion-enhanced field emission produces additional emission from the cathode and effectively reduces the voltage required to breakdown a gaseous medium at the microscale (<10 μm). In this work, we enhance classic field emission theory by determining the impact of a gaseous ion on electron tunneling and compute the effect of ion-enhanced field emission on the breakdown voltage. We reveal that the current density for ion-enhanced field emission retains the same scaling as vacuum cold field emission and that this leads to deviations from traditional breakdown theory at microscale dimensions.

  16. Highly stable piezo-immunoglobulin-biosensing of a SiO2/ZnO nanogenerator as a self-powered/active biosensor arising from the field effect influenced piezoelectric screening effect

    NASA Astrophysics Data System (ADS)

    Zhao, Yayu; Fu, Yongming; Wang, Penglei; Xing, Lili; Xue, Xinyu

    2015-01-01

    Highly stable piezo-immunoglobulin-biosensing has been realized from a SiO2/ZnO nanowire (NW) nanogenerator (NG) as a self-powered/active biosensor. The piezoelectric output generated by the SiO2/ZnO NW NG can act not only as a power source for driving the device, but also as a sensing signal for detecting immunoglobulin G (IgG). The stability of the device is very high, and the relative standard deviation (RSD) ranges from 1.20% to 4.20%. The limit of detection (LOD) of IgG on the device can reach 5.7 ng mL-1. The response of the device is in a linear relationship with IgG concentration. The biosensing performance of SiO2/ZnO NWs is much higher than that of bare ZnO NWs. A SiO2 layer uniformly coated on the surface of the ZnO NW acts as the gate insulation layer, which increases mechanical robustness and protects it from the electrical leakages and short circuits. The IgG biomolecules modified on the surface of the SiO2/ZnO NW act as a gate potential, and the field effect can influence the surface electron density of ZnO NWs, which varies the screening effect of free-carriers on the piezoelectric output. The present results demonstrate a feasible approach for a highly stable self-powered/active biosensor.

  17. Highly stable piezo-immunoglobulin-biosensing of a SiO2/ZnO nanogenerator as a self-powered/active biosensor arising from the field effect influenced piezoelectric screening effect.

    PubMed

    Zhao, Yayu; Fu, Yongming; Wang, Penglei; Xing, Lili; Xue, Xinyu

    2015-02-07

    Highly stable piezo-immunoglobulin-biosensing has been realized from a SiO2/ZnO nanowire (NW) nanogenerator (NG) as a self-powered/active biosensor. The piezoelectric output generated by the SiO2/ZnO NW NG can act not only as a power source for driving the device, but also as a sensing signal for detecting immunoglobulin G (IgG). The stability of the device is very high, and the relative standard deviation (RSD) ranges from 1.20% to 4.20%. The limit of detection (LOD) of IgG on the device can reach 5.7 ng mL(-1). The response of the device is in a linear relationship with IgG concentration. The biosensing performance of SiO2/ZnO NWs is much higher than that of bare ZnO NWs. A SiO2 layer uniformly coated on the surface of the ZnO NW acts as the gate insulation layer, which increases mechanical robustness and protects it from the electrical leakages and short circuits. The IgG biomolecules modified on the surface of the SiO2/ZnO NW act as a gate potential, and the field effect can influence the surface electron density of ZnO NWs, which varies the screening effect of free-carriers on the piezoelectric output. The present results demonstrate a feasible approach for a highly stable self-powered/active biosensor.

  18. Interaction of magnetic resonators studied by the magnetic field enhancement

    SciTech Connect

    Hou, Yumin

    2013-12-15

    It is the first time that the magnetic field enhancement (MFE) is used to study the interaction of magnetic resonators (MRs), which is more sensitive than previous parameters–shift and damping of resonance frequency. To avoid the coherence of lattice and the effect of Bloch wave, the interaction is simulated between two MRs with same primary phase when the distance is changed in the range of several resonance wavelengths, which is also compared with periodic structure. The calculated MFE oscillating and decaying with distance with the period equal to resonance wavelength directly shows the retardation effect. Simulation also shows that the interaction at normal incidence is sensitive to the phase correlation which is related with retardation effect and is ultra-long-distance interaction when the two MRs are strongly localized. When the distance is very short, the amplitude of magnetic resonance is oppressed by the strong interaction and thus the MFE can be much lower than that of single MR. This study provides the design rules of metamaterials for engineering resonant properties of MRs.

  19. Energy harvesting from electrospun piezoelectric nanofibers for structural health monitoring of a cable-stayed bridge

    NASA Astrophysics Data System (ADS)

    Maruccio, Claudio; Quaranta, Giuseppe; De Lorenzis, Laura; Monti, Giorgio

    2016-08-01

    Wireless monitoring could greatly impact the fields of structural health assessment and infrastructure asset management. A common problem to be tackled in wireless networks is the electric power supply, which is typically provided by batteries replaced periodically. A promising remedy for this issue would be to harvest ambient energy. Within this framework, the present paper proposes to harvest ambient-induced vibrations of bridge structures using a new class of piezoelectric textiles. The considered case study is an existing cable-stayed bridge located in Italy along a high-speed road that connects Rome and Naples, for which a recent monitoring campaign has allowed to record the dynamic responses of deck and cables. Vibration measurements have been first elaborated to provide a comprehensive dynamic assessment of this infrastructure. In order to enhance the electric energy that can be converted from ambient vibrations, the considered energy harvester exploits a power generator built using arrays of electrospun piezoelectric nanofibers. A finite element analysis is performed to demonstrate that such power generator is able to provide higher energy levels from recorded dynamic loading time histories than a standard piezoelectric energy harvester. Its feasibility for bridge health monitoring applications is finally discussed.

  20. Piezoelectric electrospun nanocomposite comprising Au NPs/PVDF for nerve tissue engineering.

    PubMed

    Motamedi, Asma Sadat; Mirzadeh, Hamid; Hajiesmaeilbaigi, Fereshteh; Bagheri Khoulenjani, Shadab; Shokrgozar, Mohammad Ali

    2017-03-03

    In this study, gold nanoparticles/Polyvinylidenefluoride composite electrospun mat with enhanced piezoelectricity were fabricated and characterized. Gold colloidal nanoparticles (Au NPs) were prepared via laser ablation of metallic targets in liquid media. The active Q-switched Nd:YAG laser was used as an irradiation source. Then, PVDF (Polyvinylidenefluoride) was dissolved in Au NPs colloidal solution at 30% wt for the synthesis of Au NPs/PVDF composite nanofibers by electrospinning. The optical absorbance spectra of Au NPS and the polymeric solutions were obtained by the UV-Visible spectroscopy. Moreover, the morphology of Au NPS, nanostructures of fibers and diameter size distribution of nanofibers were analyzed by Scanning Electron Microscopy (SEM), Field Emission Scanning Electron Microscopy (FESEM) and Transmitted Electron Microscopy (TEM) methods. The crystallinity and piezoelectricity of PVDF and Au NPs/PVDF composite nanofibers mats were measured by X-Ray Diffraction (XRD) and Fourier Transform Infrared (FTIR) methods. Subsequently, in vitro cytocompatibility was evaluated by MTT assay and the attachment and morphology of PC-12 cells cultured on scaffolds were studied. It was found that laser ablated Au NPs can be used in electrospun nanofibers of PVDF with adequate structural properties and increase piezoelectricity of nanofibers which might be suitable for applying as nerve tissue engineering scaffolds. This article is protected by copyright. All rights reserved.

  1. Analysis of second-harmonic generation by primary ultrasonic guided wave propagation in a piezoelectric plate.

    PubMed

    Deng, Mingxi; Xiang, Yanxun

    2015-08-01

    The effect of second-harmonic generation (SHG) by primary ultrasonic guided wave propagation is analyzed, where the nonlinear elastic, piezoelectric, and dielectric properties of the piezoelectric plate material are considered simultaneously. The formal solution of the corresponding second-harmonic displacement field is presented. Theoretical and numerical investigations clearly show that the SHG effect of primary guided wave propagation is highly sensitive to the electrical boundary conditions of the piezoelectric plate. The results obtained may provide a means through which the SHG efficiency of ultrasonic guided wave propagation can effectively be regulated by changing the electrical boundary conditions of the piezoelectric plate.

  2. Three dimensional transient multifield analysis of a piezoelectric micropump for drug delivery system for treatment of hemodynamic dysfunctions.

    PubMed

    Nisar, Asim; Afzulpurkar, Nitin; Tuantranont, Adisorn; Mahaisavariya, Banchong

    2008-12-01

    In this paper, we present design of a transdermal drug delivery system for treatment of cardiovascular or hemodynamic disorders such as hypertension. The system comprises of integrated control electronics and microelectromechanical system devices such as micropump, micro blood pressure sensor and microneedle array. The objective is to overcome the limitations of oral therapy such as variable absorption profile and the need for frequent dosing, by fabricating a safe, reliable and cost effective transdermal drug delivery system to dispense various pharmacological agents through the skin for treatment of hemodynamic dysfunction such as hypertension. Moreover, design optimization of a piezoelectrically actuated valveless micropump is presented for the drug delivery system. Because of the complexity in analysis of piezoelectric micropump, which involves structural and fluid field couplings in a complicated geometrical arrangement, finite element (FE) numerical simulation rather than an analytical system has been used. The behavior of the piezoelectric actuator with biocompatible polydimethylsiloxane membrane is first studied by conducting piezoelectric analysis. Then the performance of the valveless micropump is analyzed by building a three dimensional electric-solid-fluid model of the micropump. The effect of geometrical dimensions on micropump characteristics and efficiency of nozzle/diffuser elements of a valveless micropump is investigated in the transient analysis using multiple code coupling method. The deformation results of the membrane using multifield code coupling analysis are in good agreement with analytical as well as results of single code coupling analysis of a piezoelectric micropump. The analysis predicts that to enhance the performance of the micropump, diffuser geometrical dimensions such as diffuser length, diffuser neck width and diffuser angle need to be optimized. Micropump flow rate is not strongly affected at low excitation frequencies from 10

  3. Characterization of Hard Piezoelectric Lead-Free Ceramics

    PubMed Central

    Zhang, Shujun; Lim, Jong Bong; Lee, Hyeong Jae; Shrout, Thomas R.

    2010-01-01

    K4CuNb8O23 doped K0.45Na0.55NbO3 (KNN-KCN) ferroelectric ceramics were found to exhibit asymmetrical polarization hysteresis loops, related to the development of an internal bias field. The internal bias field is believed to be the result of defect dipoles of acceptor ions and oxygen vacancies, which lead to piezoelectric “hardening” effect, by stabilizing and pinning of the domain wall motion. The dielectric loss for the hard lead-free piezoelectric ceramic was found to be 0.6%, with mechanical quality factors Q on the order of >1500. Furthermore, the piezoelectric properties were found to decrease and the coercive field increased, when compared with the undoped material, exhibiting a typical characteristic of “hard” behavior. The temperature usage range was limited by the polymorphic phase transition temperature, being 188°C. The full set of material constants was determined for the KNN-KCN materials. Compared with conventional hard PZT ceramics, the lead-free possessed lower dielectric and piezoelectric properties; however, comparable values of mechanical Q, dielectric loss, and coercive fields were obtained, making acceptor modified KNN based lead-free piezoelectric material promising for high-power applications, where lead-free materials are desirable. PMID:19686966

  4. Enhancing molecular orientation by combining electrostatic and four-color laser fields

    NASA Astrophysics Data System (ADS)

    Xu, Shuwu; Yao, Yunhua; Lu, Chenhui; Jia, Tianqing; Ding, Jingxin; Zhang, Shian; Sun, Zhenrong

    2014-09-01

    We propose a scheme to enhance molecular orientation by combing an intense electrostatic field and a four-color laser field. We show that molecular orientation by the combined field can be obtained under a laser-field-free condition, and the maximal orientation degree can be enhanced by comparing with the sum of that individually created by the electrostatic field and the four-color laser field. Our results show that the orientation enhancement results from the larger asymmetry of the four-color laser field because of the existence of the electrostatic field. Furthermore, we also discuss the dependence of the orientation enhancement on the carrier-envelope phase, laser intensity, and pulse duration of the four-color laser field and the molecular rotational temperature.

  5. Energy Harvesting Using PVDF Piezoelectric Nanofabric

    NASA Astrophysics Data System (ADS)

    Shafii, Chakameh Shafii

    Energy harvesting using piezoelectric nanomaterial provides an opportunity for advancement towards self-powered electronics. The fabrication complexities and limited power output of these nano/micro generators have hindered these advancements thus far. This thesis presents a fabrication technique with electrospinning using a grounded cylinder as the collector. This method addresses the difficulties with the production and scalability of the nanogenerators. The non-aligned nanofibers are woven into a textile form onto the cylindrical drum that can be easily removed. The electrical poling and mechanical stretching induced by the electric field and the drum rotation increase the concentration of the piezoelectric beta phase in the PVDF nanofabric. The nanofabric is placed between two layers of polyethylene terephthalate (PET) that have interdigitated electrodes painted on them with silver paint. Applying continuous load onto the flexible PVDF nanofabric at 35Hz produces a peak voltage of 320 mV and maximum power of 2200 pW/(cm2) .

  6. High-temperature piezoelectric sensing.

    PubMed

    Jiang, Xiaoning; Kim, Kyungrim; Zhang, Shujun; Johnson, Joseph; Salazar, Giovanni

    2013-12-20

    Piezoelectric sensing is of increasing interest for high-temperature applications in aerospace, automotive, power plants and material processing due to its low cost, compact sensor size and simple signal conditioning, in comparison with other high-temperature sensing techniques. This paper presented an overview of high-temperature piezoelectric sensing techniques. Firstly, different types of high-temperature piezoelectric single crystals, electrode materials, and their pros and cons are discussed. Secondly, recent work on high-temperature piezoelectric sensors including accelerometer, surface acoustic wave sensor, ultrasound transducer, acoustic emission sensor, gas sensor, and pressure sensor for temperatures up to 1,250 °C were reviewed. Finally, discussions of existing challenges and future work for high-temperature piezoelectric sensing are presented.

  7. A Piezoelectric Shear Stress Sensor

    NASA Technical Reports Server (NTRS)

    Kim, Taeyang; Saini, Aditya; Kim, Jinwook; Gopalarathnam, Ashok; Zhu, Yong; Palmieri, Frank L.; Wohl, Christopher J.; Jiang, Xiaoning

    2016-01-01

    In this paper, a piezoelectric sensor with a floating element was developed for shear stress measurement. The piezoelectric sensor was designed to detect the pure shear stress suppressing effects of normal stress generated from the vortex lift-up by applying opposite poling vectors to the: piezoelectric elements. The sensor was first calibrated in the lab by applying shear forces and it showed high sensitivity to shear stress (=91.3 +/- 2.1 pC/Pa) due to the high piezoelectric coefficients of PMN-33%PT (d31=-1330 pC/N). The sensor also showed almost no sensitivity to normal stress (less than 1.2 pC/Pa) because of the electromechanical symmetry of the device. The usable frequency range of the sensor is 0-800 Hz. Keywords: Piezoelectric sensor, shear stress, floating element, electromechanical symmetry

  8. High-Temperature Piezoelectric Sensing

    PubMed Central

    Jiang, Xiaoning; Kim, Kyungrim; Zhang, Shujun; Johnson, Joseph; Salazar, Giovanni

    2014-01-01

    Piezoelectric sensing is of increasing interest for high-temperature applications in aerospace, automotive, power plants and material processing due to its low cost, compact sensor size and simple signal conditioning, in comparison with other high-temperature sensing techniques. This paper presented an overview of high-temperature piezoelectric sensing techniques. Firstly, different types of high-temperature piezoelectric single crystals, electrode materials, and their pros and cons are discussed. Secondly, recent work on high-temperature piezoelectric sensors including accelerometer, surface acoustic wave sensor, ultrasound transducer, acoustic emission sensor, gas sensor, and pressure sensor for temperatures up to 1,250 °C were reviewed. Finally, discussions of existing challenges and future work for high-temperature piezoelectric sensing are presented. PMID:24361928

  9. Far-Field to Near-Field Coupling for Enhancing Light-Matter Interaction

    NASA Astrophysics Data System (ADS)

    Bonakdar, Alireza

    This thesis reports on theoretical, modeling, and experimental research within the framework of a key scientific question, which is enhancing the coupling between diffraction-limited far-field and sub-wavelength quantum emitter/absorber. A typical optoelectronic device delivers an optical process such as light detection (e.g. photodetector) or light intensity modulation (e.g. electro-absorptive modulator). In conventional devices, optical process is in the form of far-field or guided wave modes. The main aim of this thesis is to show that converting these modes into near-field domain can enhance the performance of the optoelectronic device. Light in the form of far-field can be converted into near-field domain by the optical antenna. Among different optoelectronic devices, this thesis focuses mainly on integrating the optical antenna with infrared photodetectors. The available semiconductors have weak infrared absorption that reduces light detection efficiency. Integration of the optical antenna with infrared absorber (such as quantum wells in quantum well infrared photodetector (QWIP)) increases the infrared absorption. Particularly this integration is favorable as the optical antenna has low metallic loss in infrared region. The author of this thesis believes that optical antenna has unique properties in confining light on the scale of deep sub-wavelength, enhancing electric field intensity and delivering optical energy to semiconductor absorbers. These properties are reaching into practical applications only if overall optical performance is low loss, parameter free (independent of optical parameters such a polarization and angle of incident) and broadband. In this thesis, the integration of optical antenna with infrared photodetectors and thermophotovoltaic are researched and developed which satisfy the aforementioned criteria. In addition, several different optical antennas have been designed, fabricated and characterized in order to analyze and demonstrate

  10. Piezoelectric properties of rhombohedral ferroelectric materials with phase transition

    NASA Astrophysics Data System (ADS)

    Zhao, Xiaofang; Soh, A. K.

    2015-12-01

    The temporal evolution of domain structure and its piezoelectric behavior of ferroelectric material BaTiO3 during the transition process from rhombohedral to tetragonal phase under an applied electric field have been studied by employing Landau-Ginzburg theory and the phase-field method. The results obtained show that, during the transformation process, the intermediate phase was monoclinic MA phase, and several peak values of piezoelectric coefficient appeared at the stage where obvious change of domain pattern occurred. In addition, by comparing the cases of applied electric field with different frequencies, it was found that the maximum piezoelectric coefficient obtained decreased with increasing frequency value. These results are of great significance in tuning the properties of engineering domains in ferroelectrics, and could provide more fundamentals to the design of ferroelectric devices.

  11. A piezoelectric screw dislocation near an elliptical inhomogeneity containing a confocal rigid line

    NASA Astrophysics Data System (ADS)

    Jiang, C. Z.; Zhao, Y. X.; Liu, Y. W.

    2012-09-01

    The interaction between a piezoelectric screw dislocation and an elliptical inhomogeneity in piezoelectric composite material which contains an electrically conductive confocal rigid line is studied, especially analyzing the shielding effect of a piezoelectric screw dislocation near an elliptical inhomogeneity. By applying the complex variable method, the analytical solution to the elastic field and the electric field, the field intensity factors at the tip of the rigid line are derived. The image force acting on the piezoelectric screw dislocation is calculated by using the generalized Peach-Koehler formula. Accordingly, the location and the orientation of the dislocation, the material properties upon the shielding or anti-shielding effect on the stress intensity factors, as well as the effects of the rigid line and the electroelastic properties of the piezoelectric materials on the image force are discussed.

  12. Enhancement of Far Field Sound Levels by Refractive Focusing

    NASA Technical Reports Server (NTRS)

    Thomson, D. W.; Roth, S. D.

    1981-01-01

    The enhancement of sound pressure levels resulting from refractive focusing was calculated for meteorological conditions representative of those observed at the MOD-1 site near Boone, N.C. The results show that 10 to 20dB enhancements can occur over ranges of several hundred meters. Localized enhancements in excess of 20dB can occur but will probably be of limited duration as a consequence of normal temporally varying meteorological conditions.

  13. Glory of piezoelectric perovskites

    PubMed Central

    Uchino, Kenji

    2015-01-01

    This article reviews the history of piezoelectric perovskites and forecasts future development trends, including Uchino’s discoveries such as the Pb(Mg1/3Nb2/3)O3–PbTiO3 electrostrictor, Pb(Zn1/3Nb2/3)O3–PbTiO3 single crystal, (Pb, La)(Zr, Ti)O3 photostriction, and Pb(Zr, Ti)O3–Terfenol magnetoelectric composites. We discuss five key trends in the development of piezomaterials: performance to reliability, hard to soft, macro to nano, homo to hetero, and single to multi-functional. PMID:27877827

  14. Piezoelectric effect in InAs/InP quantum rod nanowires grown on silicon substrate

    SciTech Connect

    Anufriev, Roman; Chauvin, Nicolas Bru-Chevallier, Catherine; Khmissi, Hammadi; Naji, Khalid; Gendry, Michel; Patriarche, Gilles

    2014-05-05

    We report on the evidence of a strain-induced piezoelectric field in wurtzite InAs/InP quantum rod nanowires. This electric field, caused by the lattice mismatch between InAs and InP, results in the quantum confined Stark effect and, as a consequence, affects the optical properties of the nanowire heterostructure. It is shown that the piezoelectric field can be screened by photogenerated carriers or removed by increasing temperature. Moreover, a dependence of the piezoelectric field on the quantum rod diameter is observed in agreement with simulations of wurtzite InAs/InP quantum rod nanowire heterostructures.

  15. Piezoelectric Active Humidity Sensors Based on Lead-Free NaNbO3 Piezoelectric Nanofibers

    PubMed Central

    Gu, Li; Zhou, Di; Cao, Jun Cheng

    2016-01-01

    The development of micro-/nano-scaled energy harvesters and the self-powered sensor system has attracted great attention due to the miniaturization and integration of the micro-device. In this work, lead-free NaNbO3 piezoelectric nanofibers with a monoclinic perovskite structure were synthesized by the far-field electrospinning method. The flexible active humidity sensors were fabricated by transferring the nanofibers from silicon to a soft polymer substrate. The sensors exhibited outstanding piezoelectric energy-harvesting performance with output voltage up to 2 V during the vibration process. The output voltage generated by the NaNbO3 sensors exhibited a negative correlation with the environmental humidity varying from 5% to 80%, where the peak-to-peak value of the output voltage generated by the sensors decreased from 0.40 to 0.07 V. The sensor also exhibited a short response time, good selectively against ethanol steam, and great temperature stability. The piezoelectric active humidity sensing property could be attributed to the increased leakage current in the NaNbO3 nanofibers, which was generated due to proton hopping among the H3O+ groups in the absorbed H2O layers under the driving force of the piezoelectric potential. PMID:27338376

  16. Piezoelectric Active Humidity Sensors Based on Lead-Free NaNbO₃ Piezoelectric Nanofibers.

    PubMed

    Gu, Li; Zhou, Di; Cao, Jun Cheng

    2016-06-07

    The development of micro-/nano-scaled energy harvesters and the self-powered sensor system has attracted great attention due to the miniaturization and integration of the micro-device. In this work, lead-free NaNbO₃ piezoelectric nanofibers with a monoclinic perovskite structure were synthesized by the far-field electrospinning method. The flexible active humidity sensors were fabricated by transferring the nanofibers from silicon to a soft polymer substrate. The sensors exhibited outstanding piezoelectric energy-harvesting performance with output voltage up to 2 V during the vibration process. The output voltage generated by the NaNbO₃ sensors exhibited a negative correlation with the environmental humidity varying from 5% to 80%, where the peak-to-peak value of the output voltage generated by the sensors decreased from 0.40 to 0.07 V. The sensor also exhibited a short response time, good selectively against ethanol steam, and great temperature stability. The piezoelectric active humidity sensing property could be attributed to the increased leakage current in the NaNbO₃ nanofibers, which was generated due to proton hopping among the H₃O⁺ groups in the absorbed H₂O layers under the driving force of the piezoelectric potential.

  17. Enhanced Field Emission Studies on Niobium Surfaces Relevant to High Field Superconducting Radio-Frequency Devices

    SciTech Connect

    Wang, Tong

    2002-09-18

    Enhanced field emission (EFE) presents the main impediment to higher acceleration gradients in superconducting niobium (Nb) radiofrequency cavities for particle accelerators. The strength, number and sources of EFE sites strongly depend on surface preparation and handling. The main objective of this thesis project is to systematically investigate the sources of EFE from Nb, to evaluate the best available surface preparation techniques with respect to resulting field emission, and to establish an optimized process to minimize or eliminate EFE. To achieve these goals, a scanning field emission microscope (SFEM) was designed and built as an extension to an existing commercial scanning electron microscope (SEM). In the SFEM chamber of ultra high vacuum, a sample is moved laterally in a raster pattern under a high voltage anode tip for EFE detection and localization. The sample is then transferred under vacuum to the SEM chamber equipped with an energy-dispersive x-ray spectrometer for individual emitting site characterization. Compared to other systems built for similar purposes, this apparatus has low cost and maintenance, high operational flexibility, considerably bigger scan area, as well as reliable performance. EFE sources from planar Nb have been studied after various surface preparation, including chemical etching and electropolishing, combined with ultrasonic or high-pressure water rinse. Emitters have been identified, analyzed and the preparation process has been examined and improved based on EFE results. As a result, field-emission-free or near field-emission-free surfaces at ~140 MV/m have been consistently achieved with the above techniques. Characterization on the remaining emitters leads to the conclusion that no evidence of intrinsic emitters, i.e., no fundamental electric field limit induced by EFE, has been observed up to ~140 MV/m. Chemically etched and electropolished Nb are compared and no significant difference is observed up to ~140 MV/m. To

  18. Optical field enhancement of nanometer-sized gaps at near-infrared frequencies.

    PubMed

    Ahn, Jae Sung; Kang, Taehee; Singh, Dilip K; Bahk, Young-Mi; Lee, Hyunhwa; Choi, Soo Bong; Kim, Dai-Sik

    2015-02-23

    We report near-field and far-field measurements of transmission through nanometer-sized gaps at near-infrared frequencies with varying the gap size from 1 nm to 10 nm. In the far-field measurements, we excluded direct transmission on the metal film surface via interferometric method. Kirchhoff integral formalism was used to relate the far-field intensity to the electric field at the nanogaps. In near-field measurements, field enhancement factors of the nanogaps were quantified by measuring transmission of the nanogaps using near-field scanning optical microscopy. All the measurements produce similar field enhancements of about ten, which we put in the context of comparing with the giant field enhancements in the terahertz regime.

  19. Enhancing Photoresponsivity of Self-Aligned MoS2 Field-Effect Transistors by Piezo-Phototronic Effect from GaN Nanowires.

    PubMed

    Liu, Xingqiang; Yang, Xiaonian; Gao, Guoyun; Yang, Zhenyu; Liu, Haitao; Li, Qiang; Lou, Zheng; Shen, Guozhen; Liao, Lei; Pan, Caofeng; Lin Wang, Zhong

    2016-08-23

    We report high-performance self-aligned MoS2 field-effect transistors (FETs) with enhanced photoresponsivity by the piezo-phototronic effect. The FETs are fabricated based on monolayer MoS2 with a piezoelectric GaN nanowire (NW) as the local gate, and a self-aligned process is employed to define the source/drain electrodes. The fabrication method allows the preservation of the intrinsic property of MoS2 and suppresses the scattering center density in the MoS2/GaN interface, which results in high electrical and photoelectric performances. MoS2 FETs with channel lengths of ∼200 nm have been fabricated with a small subthreshold slope of 64 mV/dec. The photoresponsivity is 443.3 A·W(-1), with a fast response and recovery time of ∼5 ms under 550 nm light illumination. When strain is introduced into the GaN NW, the photoresponsivity is further enhanced to 734.5 A·W(-1) and maintains consistent response and recovery time, which is comparable with that of the mechanical exfoliation of MoS2 transistors. The approach presented here opens an avenue to high-performance top-gated piezo-enhanced MoS2 photodetectors.

  20. Fatigue crack monitoring with coupled piezoelectric film acoustic emission sensors

    NASA Astrophysics Data System (ADS)

    Zhou, Changjiang

    Fatigue-induced cracking is a commonly seen problem in civil infrastructures reaching their original design life. A number of high-profile accidents have been reported in the past that involved fatigue damage in structures. Such incidences often happen without prior warnings due to lack of proper crack monitoring technique. In order to detect and monitor the fatigue crack, acoustic emission (AE) technique, has been receiving growing interests recently. AE can provide continuous and real-time monitoring data on damage progression in structures. Piezoelectric film AE sensor measures stress-wave induced strain in ultrasonic frequency range and its feasibility for AE signal monitoring has been demonstrated recently. However, extensive work in AE monitoring system development based on piezoelectric film AE sensor and sensor characterization on full-scale structures with fatigue cracks, have not been done. A lack of theoretical formulations for understanding the AE signals also hinders the use of piezoelectric film AE sensors. Additionally, crack detection and source localization with AE signals is a very important area yet to be explored for this new type of AE sensor. This dissertation presents the results of both analytical and experimental study on the signal characteristics of surface stress-wave induced AE strain signals measured by piezoelectric film AE sensors in near-field and an AE source localization method based on sensor couple theory. Based on moment tensor theory, generalized expression for AE strain signal is formulated. A special case involving the response of piezoelectric film AE sensor to surface load is also studied, which could potentially be used for sensor calibration of this type of sensor. A new concept of sensor couple theory based AE source localization technique is proposed and validated with both simulated and experimental data from fatigue test and field monitoring. Two series of fatigue tests were conducted to perform fatigue crack

  1. Piezoelectric axial flow microvalve

    DOEpatents

    Gemmen, Randall; Thornton, Jimmy; Vipperman, Jeffrey S.; Clark, William W.

    2007-01-09

    This invention is directed to a fuel cell operable with a quantity of fuel and a quantity of an oxidizer to produce electrical power, the fuel cell including a fuel cell body including a labyrinth system structured to permit the fuel and the oxidizer to flow therethrough; at least a first catalyst in fluid communication with the labyrinth; and at least a first microvalve operably disposed within at least a portion of the labyrinth. The microvalve utilizes a deflectable member operable upon the application of a voltage from a voltage source. The microvalve includes an elongated flow channel formed therein and extending substantially longitudinally between the first and second ends to permit substantially longitudinal flow of the fluid therethrough and between the first and second ends; and the deflectable member disposed on the valve body, the deflectable member including at least a first piezoelectric portion that is piezoelectrically operable to deflect the deflectable member between an open position and a closed position upon the application of a voltage, the deflectable member in the closed position being operable to resist the flow of the fluid through the flow channel.

  2. Shear piezoelectricity in bone at the nanoscale

    NASA Astrophysics Data System (ADS)

    Minary-Jolandan, Majid; Yu, Min-Feng

    2010-10-01

    Recent demonstration of shear piezoelectricity in an isolated collagen fibril, which is the origin of piezoelectricity in bone, necessitates investigation of shear piezoelectric behavior in bone at the nanoscale. Using high resolution lateral piezoresponse force microcopy (PFM), shear piezoelectricity in a cortical bone sample was studied at the nanoscale. Subfibrillar structure of individual collagen fibrils with a periodicity of 60-70 nm were revealed in PFM map, indicating the direct contribution of collagen fibrils to the shear piezoelectricity of bone.

  3. Design Requirements for Amorphous Piezoelectric Polymers

    NASA Technical Reports Server (NTRS)

    Ounaies, Z.; Young, J. A.; Harrison, J. S.

    1999-01-01

    An overview of the piezoelectric activity in amorphous piezoelectric polymers is presented. The criteria required to render a polymer piezoelectric are discussed. Although piezoelectricity is a coupling between mechanical and electrical properties, most research has concentrated on the electrical properties of potentially piezoelectric polymers. In this work, we present comparative mechanical data as a function of temperature and offer a summary of polarization and electromechanical properties for each of the polymers considered.

  4. Piezoelectrically Actuated Shutter for High Vacuum

    NASA Technical Reports Server (NTRS)

    Thompson, Robert; Klose, Gerhard

    2003-01-01

    A piezoelectrically actuated shutter is undergoing development for use in experiments on laser cooling of atoms. The shutter is required to be compatible with ultrahigh vacuum [pressure of 10(exp -9) torr (.1.3 x 10(exp -7) Pa) or less] and to be capable of performing reliably in the vacuum for at least one year. In operation, the shutter would enable the collection and launch of successive samples of cold atoms and would enable the interrogation of the immediately preceding sample while preventing disturbance of the atoms of that sample by light from the collection region. A major constraint is imposed on the design and operation of the shutter by a requirement that it not generate a magnetic field large enough to perturb an atomic clock. An electromagnetically actuated shutter could satisfy all requirements except this one. Hence, it was decided to use piezoelectric instead of electromagnetic actuation. The shutter (see figure) includes two commercial piezoelectrically driven flexure stages that produce a travel of 0.5 mm. Levers mechanically amplify the travel to the required level of 1 cm. Problems that remained to be addressed at the time of reporting the information for this article included lifetime testing and correction of a tendency for shutter blades to bounce open.

  5. Magnetic domain-wall velocity enhancement induced by a transverse magnetic field

    NASA Astrophysics Data System (ADS)

    Yang, Jusang; Beach, Geoffrey S. D.; Knutson, Carl; Erskine, James L.

    2016-01-01

    Spin dynamics of field-driven domain walls (DWs) guided by permalloy nanowires are studied by high-speed magneto-optic polarimetry and numerical simulations. DW velocities and spin configurations are determined as functions of longitudinal drive field, transverse bias field, and nanowire width. Nanowires having cross-sectional dimensions large enough to support vortex wall structures exhibit regions of drive-field strength (at zero bias field) that have enhanced DW velocity resulting from coupled vortex structures that suppress oscillatory motion. Factor of 10 enhancements of the DW velocity are observed above the critical longitudinal drive-field (that marks the onset of oscillatory DW motion) when a transverse bias field is applied. Nanowires having smaller cross-sectional dimensions that support transverse wall structures also exhibit a region of higher mobility above the critical field, and similar transverse-field induced velocity enhancement but with a smaller enhancement factor. The bias-field enhancement of DW velocity is explained by numerical simulations of the spin distribution and dynamics within the propagating DW that reveal dynamic stabilization of coupled vortex structures and suppression of oscillatory motion in the nanowire conduit resulting in uniform DW motion at high speed. The enhanced velocity and drive field range are achieved at the expense of a less compact DW spin distribution.

  6. Local field enhancement on metallic periodic surface structures produced by femtosecond laser pulses

    SciTech Connect

    Ionin, Andrei A; Kudryashov, Sergei I; Ligachev, A E; Makarov, Sergei V; Mel'nik, N N; Rudenko, A A; Seleznev, L V; Sinitsyn, D V; Khmelnitskii, R A

    2013-04-30

    Periodic surface structures on aluminium are produced by femtosecond laser pulses for efficient excitation of surface electromagnetic waves using a strong objective (NA = 0.5). The local electromagnetic field enhancement on the structures is measured using the technique of surface-enhanced Raman scattering from pyridine molecules. (extreme light fields and their applications)

  7. Dielectric Properties of Piezoelectric Polyimides

    NASA Technical Reports Server (NTRS)

    Ounaies, Z.; Young, J. A.; Simpson, J. O.; Farmer, B. L.

    1997-01-01

    Molecular modeling and dielectric measurements are being used to identify mechanisms governing piezoelectric behavior in polyimides such as dipole orientation during poling, as well as degree of piezoelectricity achievable. Molecular modeling on polyimides containing pendant, polar nitrile (CN) groups has been completed to determine their remanent polarization. Experimental investigation of their dielectric properties evaluated as a function of temperature and frequency has substantiated numerical predictions. With this information in hand, we are then able to suggest changes in the molecular structures, which will then improve upon the piezoelectric response.

  8. REPLY: Reply to comment on 'Model calculation of the scanned field enhancement factor of CNTs'

    NASA Astrophysics Data System (ADS)

    Ahmad, Amir; Tripathi, V. K.

    2010-09-01

    In the paper (Ahmad and Tripathi 2006 Nanotechnology 17 3798), we derived an expression to compute the field enhancement factor of CNTs under any positional distribution of CNTs by using the model of a floating sphere between parallel anode and cathode plates. Using this expression we can compute the field enhancement factor of a CNT in a cluster (non-uniformly distributed CNTs). This expression was used to compute the field enhancement factor of a CNT in an array (uniformly distributed CNTs). We used an approximation to calculate the field enhancement factor. Hence, our expressions are correct in that assumption only. Zhbanov et al (2010 Nanotechnology 21 358001) suggest a correction that can calculate the field enhancement factor without using the approximation. Hence, this correction can improve the applicability of this model.

  9. Critical field enhancement of asymptotic optical bound states in the continuum

    PubMed Central

    Yoon, Jae Woong; Song, Seok Ho; Magnusson, Robert

    2015-01-01

    We study spectral singularities and critical field enhancement factors associated with embedded photonic bound states in subwavelength periodic Si films. Ultrahigh-Q resonances supporting field enhancement factor exceeding 108 are obtained in the spectral vicinity of exact embedded eigenvalues in spite of deep surface modulation and vertical asymmetry of the given structure. Treating relations between the partial resonance Q and field enhancement factors with an analytical coupled-mode model, we derive a general strategy to maximize the field enhancement associated with these photonic bound states in the presence of material dissipation. The analytical expression for the field enhancement quantitatively agrees with rigorous numerical calculations. Therefore, our results provide a general knowledge for designing practical resonance elements based on optical bound states in the continuum in various applications. PMID:26673548

  10. Generation of isolated attosecond extreme ultraviolet pulses employing nanoplasmonic field enhancement: optimization of coupled ellipsoids

    NASA Astrophysics Data System (ADS)

    Stebbings, S. L.; Süßmann, F.; Yang, Y.-Y.; Scrinzi, A.; Durach, M.; Rusina, A.; Stockman, M. I.; Kling, M. F.

    2011-07-01

    The production of extreme ultraviolet (XUV) radiation via nanoplasmonic field-enhanced high-harmonic generation (HHG) in gold nanostructures at MHz repetition rates is investigated theoretically in this paper. Analytical and numerical calculations are employed and compared in order to determine the plasmonic fields in gold ellipsoidal nanoparticles. The comparison indicates that numerical calculations can accurately predict the field enhancement and plasmonic decay, but may encounter difficulties when attempting to predict the oscillatory behavior of the plasmonic field. Numerical calculations for coupled symmetric and asymmetric ellipsoids for different carrier-envelope phases (CEPs) of the driving laser field are combined with time-dependent Schrödinger equation simulations to predict the resulting HHG spectra. The studies reveal that the plasmonic field oscillations, which are controlled by the CEP of the driving laser field, play a more important role than the nanostructure configuration in finding the optimal conditions for the generation of isolated attosecond XUV pulses via nanoplasmonic field enhancement.

  11. Geochemical Enhancement Of Enhanced Geothermal System Reservoirs: An Integrated Field And Geochemical Approach

    SciTech Connect

    Joseph N. Moore

    2007-12-31

    . In contrast, fluid inclusions trapped prior to injection are relatively gas rich. These results suggest that the rocks undergo extensive microfracturing during injection and that the composition of the fluid inclusions will be biased toward the youngest event. Interactions between the reservoir rocks and injectate were modeled using the non-isothermal reactive geochemical transport code TOUGHREACT. Changes in fluid pH, fracture porosity, fracture permeability, fluid temperature, and mineral abundances were monitored. The simulations predict that amorphous silica will precipitate primarily within a few meters of the injection well and that mineral deposition will lead to rapid declines in fracture porosity and permeability, consistent with field observations. In support of Enhanced Geothermal System development, petrologic studies of Coso well 46A-19RD were conducted to determine the regions that are most likely to fail when stimulated. These studies indicate that the most intensely brecciated and altered rocks in the zone targeted for stimulation (below 10,000 ft (3048 m)) occur between 11,200 and 11,350 ft (3414 and 3459 m). This zone is interpreted as a shear zone that initially juxtaposed quartz diorite against granodiorite. Strong pervasive alteration and veining within the brecciated quartz diorite and granodiorite suggest this shear zone was permeable in the past. This zone of weakness was subsequently exploited by a granophyre dike whose top occurs at 11,350 ft (3459 m). The dike is unaltered. We anticipate, based on analysis of the well samples that failure during stimulation will most likely occur on this shear zone.

  12. Piezoelectric Rotary Tube Motor

    NASA Technical Reports Server (NTRS)

    Fisher, Charles D.; Badescu, Mircea; Braun, David F.; Culhane, Robert

    2011-01-01

    A custom rotary SQUIGGLE(Registered TradeMark) motor has been developed that sets new benchmarks for small motor size, high position resolution, and high torque without gear reduction. Its capabilities cannot be achieved with conventional electromagnetic motors. It consists of piezoelectric plates mounted on a square flexible tube. The plates are actuated via voltage waveforms 90 out of phase at the resonant frequency of the device to create rotary motion. The motors were incorporated into a two-axis postioner that was designed for fiber-fed spectroscopy for ground-based and space-based projects. The positioner enables large-scale celestial object surveys to take place in a practical amount of time.

  13. Dynamic effective elastic modulus of polymer matrix composites with dense piezoelectric nano-fibers considering surface/interface effect

    NASA Astrophysics Data System (ADS)

    Fang, XueQian; Huang, MingJuan; Zhu, ZiTao; Liu, JinXi; Feng, WenJie

    2015-01-01

    Based on effective field method, the dynamic effective elastic modulus of polymer matrix composites embedded with dense piezoelectric nano-fibers is obtained, and the interacting effect of piezoelectric surfaces/interfaces around the nano-fibers is considered. The multiple scattering effects of harmonic anti-plane shear waves between the piezoelectric nano-fibers with surface/interface are averaged by effective field method. To analyze the interacting results among the random nano-fibers, the problem of two typical piezoelectric nano-fibers is introduced by employing the addition theorem of Bessel functions. Through numerical calculations, the influence of the distance between the randomly distributed piezoelectric nano-fibers under different surface/interface parameters is analyzed. The effect of piezoelectric property of surface/interface on the effective shear modulus under different volume fractions is also examined. Comparison with the simplified cases is given to validate this dynamic electro-elastic model.

  14. Longitudinal modes along thin piezoelectric waveguides for liquid sensing applications.

    PubMed

    Caliendo, Cinzia

    2015-06-02

    The propagation of longitudinally polarized acoustic modes along thin piezoelectric plates (BN, ZnO, InN, AlN and GaN) is theoretically studied, aiming at the design of high frequency electroacoustic devices suitable for work in liquid environments. The investigation of the acoustic field profile across the plate revealed the presence of longitudinally polarized Lamb modes, travelling at velocities close to that of the longitudinal bulk acoustic wave propagating in the same direction. Such waves are suitable for the implementation of high-frequency, low-loss electroacoustic devices operating in liquid environments. The time-averaged power flow density, the phase velocity and the electroacoustic coupling coefficient K2 dispersion curves were studied, for the first (S0) and four higher order (S1, S2, S3, S4) symmetrical modes for different electrical boundary conditions. Two electroacoustic coupling configurations were investigated, based on interdigitated transducers, with or without a metal floating electrode at the opposite plate surface. Enhanced performances, such as a K2 as high as 8.5% and a phase velocity as high as 16,700 m/s, were demostrated for the ZnO- and BN-based waveguides, as an example. The relative velocity changes, and the inertial and viscous sensitivities of the first symmetric and anti-symmetric mode, S0 and A0, propagating along thin plates bordered by a viscous liquid were derived using the perturbation approach. The present study highlights the feasibility of the piezoelectric waveguides to the development of high-frequency, integrated-circuits compatible electroacoustic devices suitable for working in liquid environment.

  15. Longitudinal Modes along Thin Piezoelectric Waveguides for Liquid Sensing Applications

    PubMed Central

    Caliendo, Cinzia

    2015-01-01

    The propagation of longitudinally polarized acoustic modes along thin piezoelectric plates (BN, ZnO, InN, AlN and GaN) is theoretically studied, aiming at the design of high frequency electroacoustic devices suitable for work in liquid environments. The investigation of the acoustic field profile across the plate revealed the presence of longitudinally polarized Lamb modes, travelling at velocities close to that of the longitudinal bulk acoustic wave propagating in the same direction. Such waves are suitable for the implementation of high-frequency, low-loss electroacoustic devices operating in liquid environments. The time-averaged power flow density, the phase velocity and the electroacoustic coupling coefficient K2 dispersion curves were studied, for the first (S0) and four higher order (S1, S2, S3, S4) symmetrical modes for different electrical boundary conditions. Two electroacoustic coupling configurations were investigated, based on interdigitated transducers, with or without a metal floating electrode at the opposite plate surface. Enhanced performances, such as a K2 as high as 8.5% and a phase velocity as high as 16,700 m/s, were demostrated for the ZnO- and BN-based waveguides, as an example. The relative velocity changes, and the inertial and viscous sensitivities of the first symmetric and anti-symmetric mode, S0 and A0, propagating along thin plates bordered by a viscous liquid were derived using the perturbation approach. The present study highlights the feasibility of the piezoelectric waveguides to the development of high-frequency, integrated-circuits compatible electroacoustic devices suitable for working in liquid environment. PMID:26043174

  16. A very promising piezoelectric property of Ta{sub 2}O{sub 5} thin films. II: Birefringence and piezoelectricity

    SciTech Connect

    Audier, M.; Chenevier, B.; Roussel, H.; Vincent, L.; Pena, A.

    2011-08-15

    Birefringent and piezoelectric properties of Ta{sub 2}O{sub 5} ceramic thin films of monoclinic and trigonal structures were analyzed. The birefringence, observed by reflected polarized light microscopy, yields information on thin film microstructures, crystal shapes and sizes and on crystallographic orientations of grains of trigonal structure. Such an information was considered for investigating piezoelectric properties by laser Doppler vibrometry and by piezoresponse force microscopy. The vibration velocity was measured by applying an oscillating electric field between electrodes on both sides of a Ta{sub 2}O{sub 5} film deposited on a Si substrate which was pasted on an isolating mica sheet. In this case, it is shown that the vibration velocity results were not only from a converse piezoelectric effect, proportional to the voltage, but also from the Coulomb force, proportional to the square of the voltage. A huge piezoelectric strain effect, up to 7.6%, is found in the case of Ta{sub 2}O{sub 5} of trigonal structure. From an estimation of the electrical field through the Ta{sub 2}O{sub 5} thin film, this strain likely corresponds to a very high longitudinal coefficient d{sub 33} of several thousand picometers. Results obtained by piezoresponse force microscopy show that trigonal grains exhibit a polarization at zero field, which is probably due to stress caused expansion in the transition monoclinic-trigonal, presented in a previous article (part I). - Graphical abstract: Image of cross-polarized optical microscopy showing grains of trigonal structure embedded in the monoclinic phase (on the left); (a) mounting of the sample for Laser Doppler Vibrometry, sample constituted of several layers and its equivalent electrical circuit; (b) longitudinal displacements due to converse piezoelectric and Coulomb effects and corresponding piezoelectric strain-U{sub app.}. hystereses. Highlights: > A new Ta{sub 2}O{sub 5} trigonal phase is shown to be birefringent and

  17. Piezoelectric inkjet printing of medical adhesives and sealants

    NASA Astrophysics Data System (ADS)

    Boehm, Ryan D.; Gittard, Shaun D.; Byrne, Jacqueline M. H.; Doraiswamy, Anand; Wilker, Jonathan J.; Dunaway, Timothy M.; Crombez, Rene; Shen, Weidian; Lee, Yuan-Shin; Narayan, Roger J.

    2010-07-01

    Piezoelectric inkjet printing is a noncontact process that enables microscale processing of biological materials. In this research summary, the use of piezoelectric inkjet printing for patterning medical adhesives and sealants, including a two-component polyethylene glycol hydrogel-based medical sealant, an N-butyl cyanoacrylate tissue adhesive, and a mussel adhesive protein biological adhesive, is described The effect of Fe(III) on mussel adhesive protein structure was evaluated by means of atomic force microscopy. The ability to process microscale patterns of medical sealants and adhesives will provide an improvement in tissue joining, including enhanced tissue integrity, reduced bond lines, and decreased adhesive toxicity. Piezoelectric inkjet deposition of medical adhesives and sealants may be used in wound closure, fracture fixation, and microscale vascular surgery.

  18. Electric field enhanced hydrogen storage on polarizable materials substrates.

    PubMed

    Zhou, J; Wang, Q; Sun, Q; Jena, P; Chen, X S

    2010-02-16

    Using density functional theory, we show that an applied electric field can substantially improve the hydrogen storage properties of polarizable substrates. This new concept is demonstrated by adsorbing a layer of hydrogen molecules on a number of nanomaterials. When one layer of H(2) molecules is adsorbed on a BN sheet, the binding energy per H(2) molecule increases from 0.03 eV/H(2) in the field-free case to 0.14 eV/H(2) in the presence of an electric field of 0.045 a.u. The corresponding gravimetric density of 7.5 wt% is consistent with the 6 wt% system target set by Department of Energy for 2010. The strength of the electric field can be reduced if the substrate is more polarizable. For example, a hydrogen adsorption energy of 0.14 eV/H(2) can be achieved by applying an electric field of 0.03 a.u. on an AlN substrate, 0.006 a.u. on a silsesquioxane molecule, and 0.007 a.u. on a silsesquioxane sheet. Thus, application of an electric field to a polarizable substrate provides a novel way to store hydrogen; once the applied electric field is removed, the stored H(2) molecules can be easily released, thus making storage reversible with fast kinetics. In addition, we show that materials with rich low-coordinated nonmetal anions are highly polarizable and can serve as a guide in the design of new hydrogen storage materials.

  19. Piezoelectric tunable microwave superconducting cavity

    NASA Astrophysics Data System (ADS)

    Carvalho, N. C.; Fan, Y.; Tobar, M. E.

    2016-09-01

    In the context of engineered quantum systems, there is a demand for superconducting tunable devices, able to operate with high-quality factors at power levels equivalent to only a few photons. In this work, we developed a 3D microwave re-entrant cavity with such characteristics ready to provide a very fine-tuning of a high-Q resonant mode over a large dynamic range. This system has an electronic tuning mechanism based on a mechanically amplified piezoelectric actuator, which controls the resonator dominant mode frequency by changing the cavity narrow gap by very small displacements. Experiments were conducted at room and dilution refrigerator temperatures showing a large dynamic range up to 4 GHz and 1 GHz, respectively, and were compared to a finite element method model simulated data. At elevated microwave power input, nonlinear thermal effects were observed to destroy the superconductivity of the cavity due to the large electric fields generated in the small gap of the re-entrant cavity.

  20. Magnetic fields suppress Pseudomonas aeruginosa biofilms and enhance ciprofloxacin activity.

    PubMed

    Bandara, H M H N; Nguyen, D; Mogarala, S; Osiñski, M; Smyth, H D C

    2015-01-01

    Due to the refractory nature of pathogenic microbial biofilms, innovative biofilm eradication strategies are constantly being sought. Thus, this study addresses a novel approach to eradicate Pseudomonas aeruginosa biofilms. Magnetic nanoparticles (MNP), ciprofloxacin (Cipro), and magnetic fields were systematically evaluated in vitro for their relative anti-biofilm contributions. Twenty-four-hour biofilms exposed to aerosolized MNPs, Cipro, or a combination of both, were assessed in the presence or absence of magnetic fields (Static one-sided, Static switched, Oscillating, Static + oscillating) using changes in bacterial metabolism, biofilm biomass, and biofilm imaging. The biofilms exposed to magnetic fields alone exhibited significant metabolic and biomass reductions (p < 0.05). When biofilms were treated with a MNP/Cipro combination, the most significant metabolic and biomass reductions were observed when exposed to static switched magnetic fields (p < 0.05). The exposure of P. aeruginosa biofilms to a static switched magnetic field alone, or co-administration with MNP/Cipro/MNP + Cipro appears to be a promising approach to eradicate biofilms of this bacterium.

  1. Electric field enhanced conductivity in strongly coupled dense metal plasma

    SciTech Connect

    Stephens, J.; Neuber, A.

    2012-06-15

    Experimentation with dense metal plasma has shown that non-negligible increases in plasma conductivity are induced when a relatively low electric field ({approx}6 kV/cm) is applied. Existing conductivity models assume that atoms, electrons, and ions all exist in thermal equilibrium. This assumption is invalidated by the application of an appreciable electric field, where electrons are accelerated to energies comparable to the ionization potential of the surrounding atoms. Experimental data obtained from electrically exploded silver wire is compared with a finite difference hydrodynamic model that makes use of the SESAME equation-of-state database. Free electron generation through both thermal and electric field excitations, and their effect on plasma conductivity are applied and discussed.

  2. Electric field enhanced conductivity in strongly coupled dense metal plasma

    NASA Astrophysics Data System (ADS)

    Stephens, J.; Neuber, A.

    2012-06-01

    Experimentation with dense metal plasma has shown that non-negligible increases in plasma conductivity are induced when a relatively low electric field (˜6 kV/cm) is applied. Existing conductivity models assume that atoms, electrons, and ions all exist in thermal equilibrium. This assumption is invalidated by the application of an appreciable electric field, where electrons are accelerated to energies comparable to the ionization potential of the surrounding atoms. Experimental data obtained from electrically exploded silver wire is compared with a finite difference hydrodynamic model that makes use of the SESAME equation-of-state database. Free electron generation through both thermal and electric field excitations, and their effect on plasma conductivity are applied and discussed.

  3. Field trial of the enhanced data authentication system (EDAS)

    SciTech Connect

    Thomas, Maikael A.; Hymel, Ross W.; Baldwin, George; Smejkal, Andreas; Linnebach, Ralf

    2016-11-01

    The Enhanced Data Authentication System (EDAS) is means to securely branch information from an existing measurement system or data stream to a secondary observer. In an international nuclear safeguards context, the EDAS connects to operator instrumentation, and provides a cryptographically secure copy of the information for a safeguards inspectorate. However, this novel capability could be a valuable complement to inspector-owned safeguards instrumentation, offering context that is valuable for anomaly resolution and contingency.

  4. Flexible piezoelectric PMN-PT nanowire-based nanocomposite and device.

    PubMed

    Xu, Shiyou; Yeh, Yao-wen; Poirier, Gerald; McAlpine, Michael C; Register, Richard A; Yao, Nan

    2013-06-12

    Piezoelectric nanocomposites represent a unique class of materials that synergize the advantageous features of polymers and piezoelectric nanostructures and have attracted extensive attention for the applications of energy harvesting and self-powered sensing recently. Currently, most of the piezoelectric nanocomposites were synthesized using piezoelectric nanostructures with relatively low piezoelectric constants, resulting in lower output currents and lower output voltages. Here, we report a synthesis of piezoelectric (1 - x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) nanowire-based nanocomposite with significantly improved performances for energy harvesting and self-powered sensing. With the high piezoelectric constant (d33) and the unique hierarchical structure of the PMN-PT nanowires, the PMN-PT nanowire-based nanocomposite demonstrated an output voltage up to 7.8 V and an output current up to 2.29 μA (current density of 4.58 μA/cm(2)); this output voltage is more than double that of other reported piezoelectric nanocomposites, and the output current is at least 6 times greater. The PMN-PT nanowire-based nanocomposite also showed a linear relationship of output voltage versus strain with a high sensitivity. The enhanced performance and the flexibility of the PMN-PT nanowire-based nanocomposite make it a promising building block for energy harvesting and self-powered sensing applications.

  5. Effect of local field enhancement on the nonlinear terahertz response of a silicon-based metamaterial

    NASA Astrophysics Data System (ADS)

    Al-Naib, Ibraheem; Sharma, Gargi; Dignam, Marc M.; Hafez, Hassan; Ibrahim, Akram; Cooke, David G.; Ozaki, Tsuneyuki; Morandotti, Roberto

    2013-11-01

    We demonstrate the strong effect of the local field enhancement on the nonlinear terahertz response of a hybrid photoexcited silicon/double concentric ring metamaterial structure. The ring resonators enhance the local terahertz electric field by more than a factor of ten, pushing the terahertz-semiconductor interaction into the high-field regime even for moderate-strength incident terahertz pulses. In this regime, terahertz field-induced intervalley scattering in the photoexcited silicon substrate dynamically alters the substrate conductivity, which in turn strongly modifies the pulse transmission. The spatial distribution of the local field enhancement within the resonator structure results in a modified bandwidth, amplitude, and central frequency of the transmission resonance occurring on a subcycle time scale. These results demonstrate an enhancement of the nonlinear terahertz response of silicon-based metamaterials that must be accounted for in the design of terahertz nonlinear devices.

  6. Multicaloric effect in a piezoelectric layer

    NASA Astrophysics Data System (ADS)

    Starkov, A. S.; Starkov, I. A.

    2016-09-01

    Changes in the temperatures and entropy of a piezoelectric layer under the electric field and stresses applied to its boundaries (a multicaloric effect) have been investigated. It has been shown that these changes are composed of three terms, which describe the electrocaloric, elastocaloric, and piezoelectrocaloric effects, respectively. If the influence of the strain gradient on the polarization is taken into account, one more term associated with the flexoelectrocaloric effect arises in the entropy change. The influence of the multicaloric effect on losses and motion of domain walls in ferroelectrics has been discussed.

  7. F-centers mechanism of long-term relaxation in lead zirconate-titanate based piezoelectric ceramics. 2. After-field relaxation

    NASA Astrophysics Data System (ADS)

    Ishchuk, V. M.; Kuzenko, D. V.

    2016-08-01

    The paper presents results of experimental study of the dielectric constant relaxation during aging process in Pb(Zr,Ti)O3 based solid solutions (PZT) after action of external DC electric field. The said process is a long-term one and is described by the logarithmic function of time. Reversible and nonreversible relaxation process takes place depending on the field intensity. The relaxation rate depends on the field strength also, and the said dependence has nonlinear and nonmonotonic form, if external field leads to domain disordering. The oxygen vacancies-based model for description of the long-term relaxation processes is suggested. The model takes into account the oxygen vacancies on the sample's surface ends, their conversion into F+- and F0-centers under external effects and subsequent relaxation of these centers into the simple oxygen vacancies after the action termination. F-centers formation leads to the violation of the original sample's electroneutrality, and generate intrinsic DC electric field into the sample. Relaxation of F-centers is accompanied by the reduction of the electric field, induced by them, and relaxation of the dielectric constant, as consequent effect.

  8. Implementation of a piezoelectric energy harvester in railway health monitoring

    NASA Astrophysics Data System (ADS)

    Li, Jingcheng; Jang, Shinae; Tang, Jiong

    2014-03-01

    With development of wireless sensor technology, wireless sensor network has shown a great potential for railway health monitoring. However, how to supply continuous power to the wireless sensor nodes is one of the critical issues in long-term full-scale deployment of the wireless smart sensors. Some energy harvesting methodologies have been available including solar, vibration, wind, etc; among them, vibration-based energy harvester using piezoelectric material showed the potential for converting ambient vibration energy to electric energy in railway health monitoring even for underground subway systems. However, the piezoelectric energy harvester has two major problems including that it could only generate small amount of energy, and that it should match the exact narrow band natural frequency with the excitation frequency. To overcome these problems, a wide band piezoelectric energy harvester, which could generate more power on various frequencies regions, has been designed and validated with experimental test. Then it was applied to a full-scale field test using actual railway train. The power generation of the wide band piezoelectric array has been compared to a narrow-band, resonant-based, piezoelectric energy harvester.

  9. In Situ Poling and Imidization of Amorphous Piezoelectric Polyimides

    NASA Technical Reports Server (NTRS)

    Park, Cheol; Ounaies, Zoubeida; Wise, Kristopher E.; Harrison, Joycelyn S.; Bushnell, Dennis M. (Technical Monitor)

    2002-01-01

    An amorphous piezoelectric polyimide containing polar functional groups has been developed using a combination of experimental and molecular modeling for potential use in high temperature applications. This amorphous polyimide, (Beta-CN)APB/ODPA, has exhibited good thermal stability and piezoelectric response at temperatures up to 150C. Density functional calculations predicted that a partially cured amic acid (open imide ring) possesses a dipole moment four times larger than the fully imidized closed ring. In situ poling and imidization of the partially cured (Beta-CN)APB/ODPA, was studied in an attempt to maximize the degree of dipolar orientation and the resultant piezoelectric response. A positive corona poling was used to minimize localized arcing during poling and to allow use of higher poling fields without dielectric breakdown. The dielectric relaxation strength, remanent polarization, and piezoelectric response were evaluated as a function of the poling profile. The partially cured, corona poled polymers exhibited higher dielectric relaxation strength (delta varepsilon), remanent polarization (Pr) and piezoelectric strain coefficient (d33) than the fully cured, conventionally poled ones.

  10. Ultrasonic resonant piezoelectric actuator with intrinsic torque measurement.

    PubMed

    Pott, Peter P; Matich, Sebastian; Schlaak, Helmut F

    2012-11-01

    Piezoelectric ultrasonic actuators are widely used in small-scale actuation systems, in which a closed-loop position control is usually utilized. To save an additional torque sensor, the intrinsic measurement capabilities of the piezoelectric material can be employed. To prove feasibility, a motor setup with clearly separated actuation for the friction and driving forces is chosen. The motor concept is based on resonant ultrasonic vibrations. To assess the effects of the direct piezoelectric effect, a capacitance bridge-type circuit has been selected. Signal processing is done by a measurement card with an integrated field-programmable gate array. The motor is used to drive a winch, and different torques are applied by means of weights to be lifted. Assessing the bridge voltage, a good proportionality to the applied torque of 1.47 mV/mN·m is shown. A hysteresis of 1% has been determined. The chosen motor concept is useful for intrinsic torque measurement. However, it provides drawbacks in terms of limited mechanical performance, wear, and thermal losses because of the soft piezoelectric material. Future work will comprise the application of the method to commercially available piezoelectric actuators as well as the implementation of the measurement circuit in an embedded system.

  11. Cellulose Nanofibril Film as a Piezoelectric Sensor Material.

    PubMed

    Rajala, Satu; Siponkoski, Tuomo; Sarlin, Essi; Mettänen, Marja; Vuoriluoto, Maija; Pammo, Arno; Juuti, Jari; Rojas, Orlando J; Franssila, Sami; Tuukkanen, Sampo

    2016-06-22

    Self-standing films (45 μm thick) of native cellulose nanofibrils (CNFs) were synthesized and characterized for their piezoelectric response. The surface and the microstructure of the films were evaluated with image-based analysis and scanning electron microscopy (SEM). The measured dielectric properties of the films at 1 kHz and 9.97 GHz indicated a relative permittivity of 3.47 and 3.38 and loss tangent tan δ of 0.011 and 0.071, respectively. The films were used as functional sensing layers in piezoelectric sensors with corresponding sensitivities of 4.7-6.4 pC/N in ambient conditions. This piezoelectric response is expected to increase remarkably upon film polarization resulting from the alignment of the cellulose crystalline regions in the film. The CNF sensor characteristics were compared with those of polyvinylidene fluoride (PVDF) as reference piezoelectric polymer. Overall, the results suggest that CNF is a suitable precursor material for disposable piezoelectric sensors, actuators, or energy generators with potential applications in the fields of electronics, sensors, and biomedical diagnostics.

  12. Piezoelectric rubber films for highly sensitive impact measurement

    NASA Astrophysics Data System (ADS)

    Wang, Jhih-Jhe; Tsai, Jui-Wei; Su, Yu-Chuan

    2013-07-01

    We have successfully demonstrated the microfabrication of piezoelectric rubber films and their application in impact measurement. To realize the desired piezoelectricity and stretchability, cellular polydimethylsiloxane (PDMS) structures with micrometer-sized voids are internally implanted with bipolar charges, which function as dipoles and respond promptly to electromechanical stimuli. In the prototype demonstration, 300 µm thick cellular PDMS films are fabricated and internally coated with a thin polytetrafluoroethylene (PTFE) layer to secure the implanted charges. Meanwhile, the top and bottom surfaces of the cellular PDMS films are deposited with stretchable gold electrodes. An electric field up to 35 MV m-1 is applied across the gold electrodes to ionize the air in the voids and to implant charges on the inner surfaces. The resulting composite structures behave like rubber (with an elastic modulus of about 300 kPa) and show strong piezoelectricity (with a piezoelectric coefficient d33 higher than 1000 pC N-1). While integrated with a wide bandwidth and large dynamic-range charge amplifier, highly sensitive impact measurement (with a stress sensitivity of about 10 mV Pa-1) is demonstrated. As such, the demonstrated piezoelectric rubber films could potentially serve as a sensitive electromechanical material for low-frequency stimuli, and fulfill the needs of a variety of physiological monitoring and wearable electronics applications.

  13. Field Trial of the Enhanced Data Authentication System (EDAS)

    SciTech Connect

    Thomas, Maikael A.; Baldwin, George T.; Hymel, Ross W.

    2016-05-01

    The goal of the field trial of EDAS was to demonstrate the utility of secure branching of operator instrumentation for nuclear safeguards, identify any unforeseen implementation and application issues with EDAS, and confirm whether the approach is compatible with operator concerns and constraints.

  14. Magnetostrictive-piezoelectric composite structures for energy harvesting

    NASA Astrophysics Data System (ADS)

    Lafont, Thomas; Gimeno, L.; Delamare, J.; Lebedev, G. A.; Zakharov, D. I.; Viala, B.; Cugat, O.; Galopin, N.; Garbuio, L.; Geoffroy, O.

    2012-09-01

    In this paper, harvesters coupling magnetostrictive and piezoelectric materials are investigated. The energy conversion of quasi-static magnetic field variations into electricity is detailed. Experimental results are exposed for two macroscopic demonstrators based on the rotation of a permanent magnet. These composite/hybrid devices use both piezoelectric and magnetostrictive (amorphous FeSiB ribbon or bulk Terfenol-D) materials. A quasi-static (or ultra-low frequency) harvester is constructed with exploitable output voltage, even in quasi-static mode. Integrated micro-harvesters using sub-micron multilayers of active materials on Si have been built and are currently being characterized.

  15. Polymer functionalized piezoelectric-FET as humidity/chemical nanosensors

    NASA Astrophysics Data System (ADS)

    Lao, Chang Shi; Kuang, Qin; Wang, Zhong L.; Park, Myung-Chul; Deng, Yulin

    2007-06-01

    By coating one side of the surface of a ZnO nanobelt (NB) with multilayer polymers using an electrostatic self-assembling process, a humidity/chemical nanosensor based on piezoelectric field effect transistor (PE-FET) is demonstrated. The working principle of the PE-FET relies on the self-contraction/expansion of the polymer, which builds up a strain in the piezoelectric NB and induces a potential drop across the NB that serves as the gate voltage for controlling the current flowing through the NB. The response of PE-FET to the phase transition of the coating polymer was also demonstrated. The device is a component for nanopiezotronics.

  16. Fractal diabolo antenna for enhancing and confining the optical magnetic field

    NASA Astrophysics Data System (ADS)

    Yang, Y.; Dai, H. T.; Sun, X. W.

    2014-01-01

    We introduce fractal geometry to diabolo nanoantenna for higher magnetic field intensity enhancement, i.e. the Sierpiński triangle diabolo antenna (STDA). Numerical results show that higher iteration of the STDA is responsible for the higher enhancement and the red shift of the resonant wavelength. Further investigation demonstrates the enhancement can be improved by increasing the length of the antenna or its central strip. By designing diabolo antennas with fractal geometry, improving the magnetic field intensity enhancement and varying the resonance conditions can be achieved while keeping the constant antenna dimensions.

  17. Fractal diabolo antenna for enhancing and confining the optical magnetic field

    SciTech Connect

    Yang, Y.; Dai, H. T.; Sun, X. W.

    2014-01-15

    We introduce fractal geometry to diabolo nanoantenna for higher magnetic field intensity enhancement, i.e. the Sierpiński triangle diabolo antenna (STDA). Numerical results show that higher iteration of the STDA is responsible for the higher enhancement and the red shift of the resonant wavelength. Further investigation demonstrates the enhancement can be improved by increasing the length of the antenna or its central strip. By designing diabolo antennas with fractal geometry, improving the magnetic field intensity enhancement and varying the resonance conditions can be achieved while keeping the constant antenna dimensions.

  18. Enhancement of electric field and Raman scattering by Ag coated Ni nanotips

    NASA Astrophysics Data System (ADS)

    Ye, Dexian; Mutisya, Stephen; Bertino, Massimo

    2011-08-01

    Localization and enhancement of electric field by Ag-coated vertical Ni nanotip arrays were studied by using finite-different time domain calculations. With the 30 nm thick Ag coating, the nanotips can localize and enhance the electric field to more than 103 times under the excitation of TE-polarized light with a 532 nm wavelength. Nanotip-enhanced Raman scattering of cytochrome-c protein was demonstrated in a confocal Raman microscope. Significant enhancement of Raman spectrum was achieved at 1 × 10-9 mol/l concentration of the proteins.

  19. Efficiency enhancement of anomalous-Doppler electron cyclotron masers with tapered magnetic field

    SciTech Connect

    Xie, Chao-Ran; Hou, Zhi-Ling; Kong, Ling-Bao E-mail: pkliu@pku.edu.cn; Liu, Pu-Kun E-mail: pkliu@pku.edu.cn; Du, Chao-Hai; Jin, Hai-Bo

    2014-02-15

    The efficiency of slow-wave electron cyclotron masers (ECM) is usually low, thus limiting the practical applications. Here, a method of tapered magnetic field is introduced for the efficiency enhancement of the slow-wave ECM. The numerical calculations show that the tapered magnetic-field method can enhance the efficiency of slow-wave ECM significantly. The effect of beam electron velocity spread on the efficiency has also been studied. Although the velocity spread reduces the efficiency, a great enhancement of efficiency can still be obtained by the tapered magnetic field method.

  20. Improving field enhancement of 2D hollow tapered waveguides via dielectric microcylinder coupling

    NASA Astrophysics Data System (ADS)

    Chen, Yongzhu; Xie, Xiangsheng; Li, Li; Chen, Gengyan; Guo, Lina; Lin, Xusheng

    2015-02-01

    We numerically study a novel scheme to improve the field enhancement of 2D hollow tapered waveguides (HTWs). A dielectric microcylinder is embedded into a metal-insulator-metal (MIM) HTW for resonant exciting gap surface plasmons (GSPs), which is different from the lowest propagating mode (TM0) excitation via the conventional fire-end coupling method. The physical mechanism of the field enhancement and the influence of critical parameters such as numerical aperture (NA) of the lens, permittivity of the microcylinder and the incident wavelength are discussed. The substantial improvement of the GSP excitation efficiency via dielectric microcylinder coupling shows potential in designing tapered MIM waveguides for nanofocusing and field enhancement.

  1. Helmholtz resonator for electric field enhancement from visible to far-infrared

    NASA Astrophysics Data System (ADS)

    Chevalier, Paul; Bouchon, Patrick; Greffet, Jean-Jacques; Pelouard, Jean-Luc; Haidar, Riad; Pardo, Fabrice

    2015-01-01

    Here we present a 2D slit-box electromagnetic nanoantenna inspired by the acoustic Helmholtz resonator. It is able to concentrate the energy into tiny volumes, and a giant field intensity enhancement is observed throughout the slit. Noteworthily, we have shown that this field intensity enhancement can also be obtained in three dimensional structures that are polarization independent. In the Helmholtz nanoantenna, the field is enhanced in a hot volume and not a hot point, which is of great interest for applications requiring extreme light concentration, such as SEIRA, non-linear optics and biophotonics.

  2. Determination of dynamic surface forces using piezoelectric arrays

    NASA Astrophysics Data System (ADS)

    Nitsche, W.; Mirow, P.

    The experimental determination of static and dynamic surface forces on flow bodies using piezoelectric arrays is outlined. The fundamentals of the piezo-array sensor technique (sensor construction, signal separation, and signal transmission) are presented. Practical applications of piezo-arrays in the fields of airfoil aerodynamics and general flow investigations are explained. The obtained measuring results are purely qualitative.

  3. Piezoelectric Actuator Modeling Using MSC/NASTRAN and MATLAB

    NASA Technical Reports Server (NTRS)

    Reaves, Mercedes C.; Horta, Lucas G.

    2003-01-01

    This paper presents a procedure for modeling structures containing piezoelectric actuators using MSCMASTRAN and MATLAB. The paper describes the utility and functionality of one set of validated modeling tools. The tools described herein use MSCMASTRAN to model the structure with piezoelectric actuators and a thermally induced strain to model straining of the actuators due to an applied voltage field. MATLAB scripts are used to assemble the dynamic equations and to generate frequency response functions. The application of these tools is discussed using a cantilever aluminum beam with a surface mounted piezoelectric actuator as a sample problem. Software in the form of MSCINASTRAN DMAP input commands, MATLAB scripts, and a step-by-step procedure to solve the example problem are provided. Analysis results are generated in terms of frequency response functions from deflection and strain data as a function of input voltage to the actuator.

  4. Impedance-based damage assessment using piezoelectric sensors

    NASA Astrophysics Data System (ADS)

    Rim, Mi-Sun; Yoo, Seung-Jae; Lee, In; Song, Jae-Hoon; Yang, Jae-Won

    2011-04-01

    Recently structural health monitoring (SHM) systems are being focused because they make it possible to assess the health of structures at real-time in many application fields such as aircraft, aerospace, civil and so on. Piezoelectric materials are widely used for sensors of SHM system to monitor damage of critical parts such as bolted joints. Bolted joints could be loosened by vibration, thermal cycling, shock, corrosion, and they cause serious mechanical failures. In this paper, impedance-based method using piezoelectric sensors was applied for real-time SHM. A steel beam specimen fastened by bolts was tested, and polymer type piezoelectric materials, PVDFs were used for sensors to monitor the condition of bolted joint connections. When structure has some damage, for example loose bolts, the impedance of PVDF sensors showed different tendency with normal structure which has no loose bolts. In the case of loose bolts, impedance values are decreased and admittance values are increased.

  5. A database to enable discovery and design of piezoelectric materials.

    PubMed

    de Jong, Maarten; Chen, Wei; Geerlings, Henry; Asta, Mark; Persson, Kristin Aslaug

    2015-01-01

    Piezoelectric materials are used in numerous applications requiring a coupling between electrical fields and mechanical strain. Despite the technological importance of this class of materials, for only a small fraction of all inorganic compounds which display compatible crystallographic symmetry, has piezoelectricity been characterized experimentally or computationally. In this work we employ first-principles calculations based on density functional perturbation theory to compute the piezoelectric tensors for nearly a thousand compounds, thereby increasing the available data for this property by more than an order of magnitude. The results are compared to select experimental data to establish the accuracy of the calculated properties. The details of the calculations are also presented, along with a description of the format of the database developed to make these computational results publicly available. In addition, the ways in which the database can be accessed and applied in materials development efforts are described.

  6. A database to enable discovery and design of piezoelectric materials

    PubMed Central

    de Jong, Maarten; Chen, Wei; Geerlings, Henry; Asta, Mark; Persson, Kristin Aslaug

    2015-01-01

    Piezoelectric materials are used in numerous applications requiring a coupling between electrical fields and mechanical strain. Despite the technological importance of this class of materials, for only a small fraction of all inorganic compounds which display compatible crystallographic symmetry, has piezoelectricity been characterized experimentally or computationally. In this work we employ first-principles calculations based on density functional perturbation theory to compute the piezoelectric tensors for nearly a thousand compounds, thereby increasing the available data for this property by more than an order of magnitude. The results are compared to select experimental data to establish the accuracy of the calculated properties. The details of the calculations are also presented, along with a description of the format of the database developed to make these computational results publicly available. In addition, the ways in which the database can be accessed and applied in materials development efforts are described. PMID:26451252

  7. Switchable static friction of piezoelectric composite—silicon wafer contacts

    NASA Astrophysics Data System (ADS)

    van den Ende, D. A.; Fischer, H. R.; Groen, W. A.; van der Zwaag, S.

    2013-04-01

    The meso-scale surface roughness of piezoelectric fiber composites can be manipulated by applying an electric field to a piezocomposite with a polished surface. In the absence of an applied voltage, the tips of the embedded piezoelectric ceramic fibers are below the surface of the piezocomposite and a silicon wafer counter surface rests solely on the matrix region of the piezocomposite surface. When actuated, the piezoelectric ceramic fibers protrude from the surface and the wafer rests solely on these protrusions. A threefold decrease in engineering static friction coefficient upon actuation of the piezocomposite was observed: from μ* = 1.65 to μ* = 0.50. These experimental results could be linked to the change in contact surface area and roughness using capillary adhesion theory, which relates the adhesive force to the number and size of the contacting asperities for the different surface states.

  8. Pyro- and piezo-electric nanotubes

    NASA Astrophysics Data System (ADS)

    Buongiorno Nardelli, Marco; Bernholc, J.

    2001-03-01

    Using large-scale ab-initio computer simulations we have shown that nanotube structures based on boron, nitrogen and carbon are pyro- and piezo-electric, due to the intrinsic polar nature of the B-N bond and the particular symmetry of the BN hexagonal ring. Strong polarization fields are present in BN/C nanotube superlattices, which makes them true pyro- and piezo-electric systems. Similar effects are also present in conjugate organic copolymers, where the BN hexagonal ring is part of the monomeric unit. Polarization fields in BN/C nanotubes are of the order of a few tenths of kV/cm and they are additive, so that large tubular systems (multiwalled nanotubes or ropes) will exhibit fields comparable and eventually larger than those observed in common piezo- and pyro-electric materials. This opens a broad avenue for applications of these structures as basic components of nano electro-mechanical systems (NEMS) such as switches, resonators, actuators, and transducers.

  9. Electromechanical simulation and test of rotating systems with magnetic bearing or piezoelectric actuator active vibration control

    NASA Technical Reports Server (NTRS)

    Palazzolo, Alan B.; Tang, Punan; Kim, Chaesil; Manchala, Daniel; Barrett, Tim; Kascak, Albert F.; Brown, Gerald; Montague, Gerald; Dirusso, Eliseo; Klusman, Steve

    1994-01-01

    This paper contains a summary of the experience of the authors in the field of electromechanical modeling for rotating machinery - active vibration control. Piezoelectric and magnetic bearing actuator based control are discussed.

  10. Piezoelectric Templates – New Views on Biomineralization and Biomimetics

    PubMed Central

    Stitz, Nina; Eiben, Sabine; Atanasova, Petia; Domingo, Neus; Leineweber, Andreas; Burghard, Zaklina; Bill, Joachim

    2016-01-01

    Biomineralization in general is based on electrostatic interactions and molecular recognition of organic and inorganic phases. These principles of biomineralization have also been utilized and transferred to bio-inspired synthesis of functional materials during the past decades. Proteins involved in both, biomineralization and bio-inspired processes, are often piezoelectric due to their dipolar character hinting to the impact of a template’s piezoelectricity on mineralization processes. However, the piezoelectric contribution on the mineralization process and especially the interaction of organic and inorganic phases is hardly considered so far. We herein report the successful use of the intrinsic piezoelectric properties of tobacco mosaic virus (TMV) to synthesize piezoelectric ZnO. Such films show a two-fold increase of the piezoelectric coefficient up to 7.2 pm V−1 compared to films synthesized on non-piezoelectric templates. By utilizing the intrinsic piezoelectricity of a biotemplate, we thus established a novel synthesis pathway towards functional materials, which sheds light on the whole field of biomimetics. The obtained results are of even broader and general interest since they are providing a new, more comprehensive insight into the mechanisms involved into biomineralization in living nature. PMID:27212583

  11. Piezoelectric Templates – New Views on Biomineralization and Biomimetics

    NASA Astrophysics Data System (ADS)

    Stitz, Nina; Eiben, Sabine; Atanasova, Petia; Domingo, Neus; Leineweber, Andreas; Burghard, Zaklina; Bill, Joachim

    2016-05-01

    Biomineralization in general is based on electrostatic interactions and molecular recognition of organic and inorganic phases. These principles of biomineralization have also been utilized and transferred to bio-inspired synthesis of functional materials during the past decades. Proteins involved in both, biomineralization and bio-inspired processes, are often piezoelectric due to their dipolar character hinting to the impact of a template’s piezoelectricity on mineralization processes. However, the piezoelectric contribution on the mineralization process and especially the interaction of organic and inorganic phases is hardly considered so far. We herein report the successful use of the intrinsic piezoelectric properties of tobacco mosaic virus (TMV) to synthesize piezoelectric ZnO. Such films show a two-fold increase of the piezoelectric coefficient up to 7.2 pm V‑1 compared to films synthesized on non-piezoelectric templates. By utilizing the intrinsic piezoelectricity of a biotemplate, we thus established a novel synthesis pathway towards functional materials, which sheds light on the whole field of biomimetics. The obtained results are of even broader and general interest since they are providing a new, more comprehensive insight into the mechanisms involved into biomineralization in living nature.

  12. Fundamental understanding of wave generation and reception using d(36) type piezoelectric transducers.

    PubMed

    Zhou, Wensong; Li, Hui; Yuan, Fuh-Gwo

    2015-03-01

    A new piezoelectric wafer made from a PMN-PT single crystal with dominant piezoelectric coefficient d36 is proposed to generate and detect guided waves on isotropic plates. The in-plane shear coupled with electric field arising from the piezoelectric coefficient is not usually present for conventional piezoelectric wafers, such as lead zirconate titanate (PZT). The direct piezoelectric effect of coefficient d36 indicates that under external in-plane shear stress the charge is induced on a face perpendicular to the poled z-direction. On thin plates, this type of piezoelectric wafer will generate shear horizontal (SH) waves in two orthogonal wave propagation directions as well as two Lamb wave modes in other wave propagation directions. Finite element analyses are employed to explore the wave disturbance in terms of time-varying displacements excited by the d36 wafer in different directions of wave propagation to understand all the guided wave modes accurately. Experiments are conducted to examine the voltage responses received by this type of wafer, and also investigate results of tuning frequency and effects of d31 piezoelectric coefficient, which is intentionally ignored in the finite element analysis. All results demonstrate the main features and utility of proposed d36 piezoelectric wafer for guided wave generation and detection in structural health monitoring.

  13. HDR Pathological Image Enhancement Based on Improved Bias Field Correction and Guided Image Filter

    PubMed Central

    Zhu, Ganzheng; Li, Siqi; Gong, Shang; Yang, Benqiang; Zhang, Libo

    2016-01-01

    Pathological image enhancement is a significant topic in the field of pathological image processing. This paper proposes a high dynamic range (HDR) pathological image enhancement method based on improved bias field correction and guided image filter (GIF). Firstly, a preprocessing including stain normalization and wavelet denoising is performed for Haematoxylin and Eosin (H and E) stained pathological image. Then, an improved bias field correction model is developed to enhance the influence of light for high-frequency part in image and correct the intensity inhomogeneity and detail discontinuity of image. Next, HDR pathological image is generated based on least square method using low dynamic range (LDR) image, H and E channel images. Finally, the fine enhanced image is acquired after the detail enhancement process. Experiments with 140 pathological images demonstrate the performance advantages of our proposed method as compared with related work. PMID:28116303

  14. Image dipoles approach to the local field enhancement in nanostructured Ag-Au hybrid devices.

    PubMed

    David, Christin; Richter, Marten; Knorr, Andreas; Weidinger, Inez M; Hildebrandt, Peter

    2010-01-14

    We have investigated the plasmonic enhancement in the radiation field at various nanostructured multilayer devices that may be applied in surface enhanced Raman spectroscopy. We apply an image dipole method to describe the effect of surface morphology on the field enhancement in a quasistatic limit. In particular, we compare the performance of a nanostructured silver surface and a layered silver-gold hybrid device. It is found that localized surface plasmon states provide a high field enhancement in silver-gold hybrid devices, where symmetry breaking due to surface defects is a supporting factor. These results are compared to those obtained for multishell nanoparticles of spherical symmetry. Calculated enhancement factors are discussed on the background of recent experimental data.

  15. Older women track and field athletes have enhanced calcaneal stiffness.

    PubMed

    Welch, J M; Rosen, C J

    2005-08-01

    Vigorous weight-bearing exercise is recommended to women as a method of osteoporosis prevention. This study examined older women athletes to see if they indeed were less likely to develop osteoporosis than those in the general population, and to investigate which factors could have contributed to these results. One hundred and thirty-nine women 40-88 years old, all competitors in a USA National Masters Track and Field Championships, volunteered for the study. Masters refers to competitors > or =40 years old. Their calcaneal stiffness (SI) was measured by a Lunar Achilles+ ultrasonometer. Subjects were also measured for height and weight, and completed a questionnaire on exercise history, diet, lifestyle factors, medical and menopausal issues, and use of hormone replacement therapy (HRT). The women, mean age 57.3 years, had an overall average SI of 99.5 (T-score = 0.04) which is equivalent to that of a 20-year-old woman and 20.8% higher than expected for women of their age. Their median SI remained not different from expected peak bone SI until the age of 70. For analysis, this cohort of women was divided into two groups: premenopausal and postmenopausal athletes. The SI of both groups was correlated with the earliest age at which they had first participated in sports or exercises that impart moderate to high strain rates to the lower limbs and with current participation in high impact track and field events. Variables correlated with SI in the general population, such as weight, HRT, previous fracture, hysterectomy, and current menopausal status, did not predict SI in this cohort. In conclusion, women competing in Masters track and field at the national level had calcaneal stiffness substantially higher than expected for women of their age in the general population, and their participation in vigorous sports and activities, either currently or at a younger age, was predictive of this association.

  16. Restricted Field IMRT Dramatically Enhances IMRT Planning for Mesothelioma

    SciTech Connect

    Allen, Aaron M. Schofield, Deborah; Hacker, Fred; Court, Laurence E.; Czerminska, Maria M.S.

    2007-12-01

    Purpose: To improve the target coverage and normal tissue sparing of intensity-modulated radiotherapy (IMRT) for mesothelioma after extrapleural pneumonectomy. Methods and Materials: Thirteen plans from patients previously treated with IMRT for mesothelioma were replanned using a restricted field technique. This technique was novel in two ways. It limited the entrance beams to 200{sup o} around the target and three to four beams per case had their field apertures restricted down to the level of the heart or liver to further limit the contralateral lung dose. New constraints were added that included a mean lung dose of <9.5 Gy and volume receiving {>=}5 Gy of <55%. Results: In all cases, the planning target volume coverage was excellent, with an average of 97% coverage of the planning target volume by the target dose. No change was seen in the target coverage with the new technique. The heart, kidneys, and esophagus were all kept under tolerance in all cases. The average mean lung dose, volume receiving {>=}20 Gy, and volume receiving {>=}5 Gy with the new technique was 6.6 Gy, 3.0%, and 50.8%, respectively, compared with 13.8 Gy, 15%, and 90% with the previous technique (p < 0.0001 for all three comparisons). The maximal value for any case in the cohort was 8.0 Gy, 7.3%, and 57.5% for the mean lung dose, volume receiving {>=}20 Gy, and volume receiving {>=}5 Gy, respectively. Conclusion: Restricted field IMRT provides an improved method to deliver IMRT to a complex target after extrapleural pneumonectomy. An upcoming Phase I trial will provide validation of these results.

  17. Development of an Enhanced Two-Phase Production System at the Geysers Geothermal Field

    SciTech Connect

    Steven Enedy

    2001-12-14

    A method was developed to enhance geothermal steam production from two-phase wells at THE Geysers Geothermal Field. The beneficial result was increased geothermal production that was easily and economically delivered to the power plant.

  18. Parainfluenza virus isolation enhancement utilizing a portable cell culture system in the field.

    PubMed Central

    Parkinson, A J; Muchmore, H G; Scott, L V; Miles, J A

    1980-01-01

    Using a portable minaturized cell culture system, enhanced recoveries of parainfluenza virus types 1 and 3 were made in the field from symptomatic human adult subjects working at remote Antarctic stations. PMID:6247369

  19. Field enhancement factor dependence on electric field and implications on microscale gas breakdown: Theory and experimental interpretation

    NASA Astrophysics Data System (ADS)

    Alejandro Buendia, Jose; Venkattraman, Ayyaswamy

    2015-12-01

    In this letter, we obtain a better understanding of effective field enhancement factors (β eff) in the context of microscale gas breakdown with specific emphasis on its dependence on applied electric field. The theoretical dependence of β eff on electric field for various hemi-ellipsoidal asperities indicates that the value of β eff decreases with increasing electric field. The interpretation of experimental data using a typical one-dimensional modified Paschen law indicates a qualitatively similar electric field dependence even though the data could not be completely explained using a single effective asperity size. The values of β eff extracted from seven independent experimental datasets for microscale breakdown of argon and air are shown to be consistent and an empirical dependence on electric field is determined.

  20. Giant Piezoelectricity and High Curie Temperature in Nanostructured Alkali Niobate Lead-Free Piezoceramics through Phase Coexistence.

    PubMed

    Wu, Bo; Wu, Haijun; Wu, Jiagang; Xiao, Dingquan; Zhu, Jianguo; Pennycook, Stephen J

    2016-11-30

    Because of growing environmental concerns, the development of lead-free piezoelectric materials with enhanced properties has become of great interest. Here, we report a giant piezoelectric coefficient (d33) of 550 pC/N and a high Curie temperature (TC) of 237 °C in (1-x-y)K1-wNawNb1-zSbzO3-xBiFeO3-yBi0.5Na0.5ZrO3 (KNwNSz-xBF-yBNZ) ceramics by optimizing x, y, z, and w. Atomic-resolution polarization mapping by Z-contrast imaging reveals the intimate coexistence of rhombohedral (R) and tetragonal (T) phases inside nanodomains, that is, a structural origin for the R-T phase boundary in the present KNN system. Hence, the physical origin of high piezoelectric performance can be attributed to a nearly vanishing polarization anisotropy and thus low domain wall energy, facilitating easy polarization rotation between different states under an external field.

  1. Externally imposed electric field enhances plant root tip regeneration.

    PubMed

    Kral, Nicolas; Hanna Ougolnikova, Alexandra; Sena, Giovanni

    2016-06-01

    In plants, shoot and root regeneration can be induced in the distinctive conditions of tissue culture (in vitro) but is also observed in intact individuals (in planta) recovering from tissue damage. Roots, for example, can regenerate their fully excised meristems in planta, even in mutants with impaired apical stem cell niches. Unfortunately, to date a comprehensive understanding of regeneration in plants is still missing. Here, we provide evidence that an imposed electric field can perturb apical root regeneration in Arabidopsis. Crucially, we explored both spatial and temporal competences of the stump to respond to electrical stimulation, by varying respectively the position of the cut and the time interval between excision and stimulation. Our data indicate that a brief pulse of an electric field parallel to the root is sufficient to increase by up to two-fold the probability of its regeneration, and to perturb the local distribution of the hormone auxin, as well as cell division regulation. Remarkably, the orientation of the root towards the anode or the cathode is shown to play a role.

  2. Externally imposed electric field enhances plant root tip regeneration

    PubMed Central

    Kral, Nicolas; Hanna Ougolnikova, Alexandra

    2016-01-01

    Abstract In plants, shoot and root regeneration can be induced in the distinctive conditions of tissue culture (in vitro) but is also observed in intact individuals (in planta) recovering from tissue damage. Roots, for example, can regenerate their fully excised meristems in planta, even in mutants with impaired apical stem cell niches. Unfortunately, to date a comprehensive understanding of regeneration in plants is still missing. Here, we provide evidence that an imposed electric field can perturb apical root regeneration in Arabidopsis. Crucially, we explored both spatial and temporal competences of the stump to respond to electrical stimulation, by varying respectively the position of the cut and the time interval between excision and stimulation. Our data indicate that a brief pulse of an electric field parallel to the root is sufficient to increase by up to two‐fold the probability of its regeneration, and to perturb the local distribution of the hormone auxin, as well as cell division regulation. Remarkably, the orientation of the root towards the anode or the cathode is shown to play a role. PMID:27606066

  3. Cryogenic Piezoelectric Actuator

    NASA Technical Reports Server (NTRS)

    Jiang, Xiaoning; Cook, William B.; Hackenberger, Wesley S.

    2009-01-01

    In this paper, PMN-PT single crystal piezoelectric stack actuators and flextensional actuators were designed, prototyped and characterized for space optics applications. Single crystal stack actuators with footprint of 10 mm x10 mm and the height of 50 mm were assembled using 10 mm x10mm x0.15mm PMN-PT plates. These actuators showed stroke > 65 - 85 microns at 150 V at room temperature, and > 30 microns stroke at 77 K. Flextensional actuators with dimension of 10mm x 5 mm x 7.6 mm showed stroke of >50 microns at room temperature at driving voltage of 150 V. A flextensional stack actuator with dimension of 10 mm x 5 mm x 47 mm showed stroke of approx. 285 microns at 150 V at room temperature and > 100 microns at 77K under driving of 150 V should be expected. The large cryogenic stroke and high precision of these actuators are promising for cryogenic optics applications.

  4. Electric field confinement and enhancement in a silver film Fabry-Pérot interferometer.

    PubMed

    Yu, Feng; Wang, Haining; Zou, Shengli

    2009-04-23

    Using the discrete dipole approximation method and exact analytical solutions, we demonstrate that an incident electromagnetic wave can be confined and enhanced between two silver layers due to the Fabry-Pérot effect. The enhanced electric field between the two layers depends on the distance between the two layers and each layer's thickness. An enhanced electric field, |E|(2), with an enhancement factor of 50 was obtained at distances 100 nm above the surface. The resonance wavelength increases linearly with the distance between the two layers and varies with their thicknesses. Reduced scattering and enhanced absorption efficiencies of the interferometer at resonance wavelength were observed. The effect demonstrated here could be applied for studying both enhanced fluorescence and nanolasers.

  5. Enhanced trapped field performance of bulk high-temperature superconductors using split coil, pulsed field magnetization with an iron yoke

    NASA Astrophysics Data System (ADS)

    Ainslie, M. D.; Fujishiro, H.; Mochizuki, H.; Takahashi, K.; Shi, Y.-H.; Namburi, D. K.; Zou, J.; Zhou, D.; Dennis, A. R.; Cardwell, D. A.

    2016-07-01

    Investigating and predicting the magnetization of bulk superconducting materials and developing practical magnetizing techniques is crucial to using them as trapped field magnets in engineering applications. The pulsed field magnetization (PFM) technique is considered to be a compact, mobile and relative inexpensive way to magnetize bulk samples, requiring shorter magnetization times (on the order of milliseconds) and a smaller and less complicated magnetization fixture; however, the trapped field produced by PFM is generally much smaller than that of slower zero field cooling or field cooling techniques, particularly at lower operating temperatures. In this paper, the PFM of two, standard Ag-containing Gd-Ba-Cu-O samples is carried out using two types of magnetizing coils: (1) a solenoid coil, and (2) a split coil, both of which make use of an iron yoke to enhance the trapped magnetic field. It is shown that a significantly higher trapped field can be achieved using a split coil with an iron yoke, and in order to explain these how this arrangement works in detail, numerical simulations using a 2D axisymmetric finite element method based on the H -formulation are carried to qualitatively reproduce and analyze the magnetization process from both electromagnetic and thermal points of view. It is observed that after the pulse peak significantly less flux exits the bulk when the iron core is present, resulting in a higher peak trapped field, as well as more overall trapped flux, after the magnetization process is complete. The results have important implications for practical applications of bulk superconductors as such a split coil arrangement with an iron yoke could be incorporated into the design of a portable, high magnetic field source/magnet to enhance the available magnetic field or in an axial gap-type bulk superconducting electric machine, where iron can be incorporated into the stator windings to (1) improve the trapped field from the magnetization process

  6. Electric Field Stimulation Enhances Healing of Post-Traumatic Osteoarthritic Cartilage

    DTIC Science & Technology

    2015-10-01

    AWARD NUMBER: W81XWH-14-1-0591 TITLE: Electric Field Stimulation Enhances Healing of Post-Traumatic Osteoarthritic Cartilage PRINCIPAL...DATES COVERED 30 Sep 2014 – 29 Sep 2015 4. TITLE AND SUBTITLE Electric Field Stimulation Enhances Healing of Post-Traumatic Osteoarthritic Cartilage...instability, among other traumatic affections of joints, and occupations or sports that subject joints to high levels of impact and torsional loading

  7. Effect of grain size on actuator properties of piezoelectric ceramics

    NASA Astrophysics Data System (ADS)

    Hackenberger, Wesley S.; Pan, Ming-Jen; Vedula, Venkata; Pertsch, Patrick; Cao, Wenwu; Randall, Clive A.; Shrout, Thomas R.

    1998-07-01

    Properties of piezoelectric ceramics important for actuator applications have been measured as a function of grain size. Fine grain piezoelectrics (<=1 μm) have been found to exhibit improved machinability and increased mechanical strength over conventional materials. Actuators made from fine grain ceramic are, therefore, expected to have improved reliability, higher driving fields, and lower driving voltages (from thinner layers in stacked or co-fired actuators) over devices fabricated from conventional materials. TRS Ceramics in collaboration with the Pennsylvania State University's Materials Research Laboratory, has developed fine grain piezoelectric ceramics with minimal or no reduction in piezoactivity. New chemical doping strategies designed to compensate ferroelectric domain clamping effects from grain boundaries have been successful in yielding submicron grain sized ceramics with both low and high field properties equivalent to conventional materials. In the case of Type II ceramics, reduced grain size results in a very stable domain state with respect to both electric field and compressive prestress. Work is in progress to develop both epoxy bonded stack and co-fired actuators from fine grain piezoelectrics.

  8. Radially sandwiched cylindrical piezoelectric transducer

    NASA Astrophysics Data System (ADS)

    Lin, Shuyu; Fu, Zhiqiang; Zhang, Xiaoli; Wang, Yong; Hu, Jing

    2013-01-01

    A new type of radially sandwiched piezoelectric short cylindrical transducer is developed and its radial vibration is studied. The transducer is composed of a solid metal disk, a radially polarized piezoelectric ceramic short tube and a metal tube. The radial vibrations of the solid metal disk, the radially polarized piezoelectric tube and the metal tube are analyzed and their electromechanical equivalent circuits are introduced. Based on the mechanical boundary conditions among the metal disk, the piezoelectric tube and the metal tube, a three-port electromechanical equivalent circuit for the radially sandwiched transducer is obtained and the frequency equation is given. The theoretical relationship of the resonance and anti-resonance frequencies and the effective electromechanical coupling coefficient with the geometrical dimensions is analyzed. The radial vibration of the sandwiched transducer is simulated by using two different numerical methods. It is shown that the analytical resonance and anti-resonance frequencies are in good agreement with the numerically simulated results. The transducer is expected to be used in piezoelectric resonators, actuators and ultrasonic radiators in ultrasonic and underwater sound applications.

  9. Narrow band perfect absorber for maximum localized magnetic and electric field enhancement and sensing applications

    NASA Astrophysics Data System (ADS)

    Yong, Zhengdong; Zhang, Senlin; Gong, Chensheng; He, Sailing

    2016-04-01

    Plasmonics offer an exciting way to mediate the interaction between light and matter, allowing strong field enhancement and confinement, large absorption and scattering at resonance. However, simultaneous realization of ultra-narrow band perfect absorption and electromagnetic field enhancement is challenging due to the intrinsic high optical losses and radiative damping in metals. Here, we propose an all-metal plasmonic absorber with an absorption bandwidth less than 8 nm and polarization insensitive absorptivity exceeding 99%. Unlike traditional Metal-Dielectric-Metal configurations, we demonstrate that the narrowband perfect absorption and field enhancement are ascribed to the vertical gap plasmonic mode in the deep subwavelength scale, which has a high quality factor of 120 and mode volume of about 10-4 × (λres/n)3. Based on the coupled mode theory, we verify that the diluted field enhancement is proportional to the absorption, and thus perfect absorption is critical to maximum field enhancement. In addition, the proposed perfect absorber can be operated as a refractive index sensor with a sensitivity of 885 nm/RIU and figure of merit as high as 110. It provides a new design strategy for narrow band perfect absorption and local field enhancement, and has potential applications in biosensors, filters and nonlinear optics.

  10. Narrow band perfect absorber for maximum localized magnetic and electric field enhancement and sensing applications

    PubMed Central

    Yong, Zhengdong; Zhang, Senlin; Gong, Chensheng; He, Sailing

    2016-01-01

    Plasmonics offer an exciting way to mediate the interaction between light and matter, allowing strong field enhancement and confinement, large absorption and scattering at resonance. However, simultaneous realization of ultra-narrow band perfect absorption and electromagnetic field enhancement is challenging due to the intrinsic high optical losses and radiative damping in metals. Here, we propose an all-metal plasmonic absorber with an absorption bandwidth less than 8 nm and polarization insensitive absorptivity exceeding 99%. Unlike traditional Metal-Dielectric-Metal configurations, we demonstrate that the narrowband perfect absorption and field enhancement are ascribed to the vertical gap plasmonic mode in the deep subwavelength scale, which has a high quality factor of 120 and mode volume of about 10−4 × (λres/n)3. Based on the coupled mode theory, we verify that the diluted field enhancement is proportional to the absorption, and thus perfect absorption is critical to maximum field enhancement. In addition, the proposed perfect absorber can be operated as a refractive index sensor with a sensitivity of 885 nm/RIU and figure of merit as high as 110. It provides a new design strategy for narrow band perfect absorption and local field enhancement, and has potential applications in biosensors, filters and nonlinear optics. PMID:27046540

  11. Observation of piezoelectricity in free-standing monolayer MoS2

    NASA Astrophysics Data System (ADS)

    Zhu, Hanyu; Wang, Yuan; Xiao, Jun; Liu, Ming; Xiong, Shaomin; Wong, Zi Jing; Ye, Ziliang; Ye, Yu; Yin, Xiaobo; Zhang, Xiang

    2015-02-01

    Piezoelectricity allows precise and robust conversion between electricity and mechanical force, and arises from the broken inversion symmetry in the atomic structure. Reducing the dimensionality of bulk materials has been suggested to enhance piezoelectricity. However, when the thickness of a material approaches a single molecular layer, the large surface energy can cause piezoelectric structures to be thermodynamically unstable. Transition-metal dichalcogenides can retain their atomic structures down to the single-layer limit without lattice reconstruction, even under ambient conditions. Recent calculations have predicted the existence of piezoelectricity in these two-dimensional crystals due to their broken inversion symmetry. Here, we report experimental evidence of piezoelectricity in a free-standing single layer of molybdenum disulphide (MoS2) and a measured piezoelectric coefficient of e11 = 2.9 × 10-10 C m-1. The measurement of the intrinsic piezoelectricity in such free-standing crystals is free from substrate effects such as doping and parasitic charges. We observed a finite and zero piezoelectric response in MoS2 in odd and even number of layers, respectively, in sharp contrast to bulk piezoelectric materials. This oscillation is due to the breaking and recovery of the inversion symmetry of the two-dimensional crystal. Through the angular dependence of electromechanical coupling, we determined the two-dimensional crystal orientation. The piezoelectricity discovered in this single molecular membrane promises new applications in low-power logic switches for computing and ultrasensitive biological sensors scaled down to a single atomic unit cell.

  12. Matter-enhanced transition probabilities in quantum field theory

    SciTech Connect

    Ishikawa, Kenzo Tobita, Yutaka

    2014-05-15

    The relativistic quantum field theory is the unique theory that combines the relativity and quantum theory and is invariant under the Poincaré transformation. The ground state, vacuum, is singlet and one particle states are transformed as elements of irreducible representation of the group. The covariant one particles are momentum eigenstates expressed by plane waves and extended in space. Although the S-matrix defined with initial and final states of these states hold the symmetries and are applied to isolated states, out-going states for the amplitude of the event that they are detected at a finite-time interval T in experiments are expressed by microscopic states that they interact with, and are surrounded by matters in detectors and are not plane waves. These matter-induced effects modify the probabilities observed in realistic situations. The transition amplitudes and probabilities of the events are studied with the S-matrix, S[T], that satisfies the boundary condition at T. Using S[T], the finite-size corrections of the form of 1/T are found. The corrections to Fermi’s golden rule become larger than the original values in some situations for light particles. They break Lorentz invariance even in high energy region of short de Broglie wave lengths. -- Highlights: •S-matrix S[T] for the finite-time interval in relativistic field theory. •S[T] satisfies the boundary condition and gives correction of 1/T . •The large corrections for light particles breaks Lorentz invariance. •The corrections have implications to neutrino experiments.

  13. Polymer Piezoelectric Transducers for Ultrasonic NDE

    NASA Technical Reports Server (NTRS)

    Bar-Cohen, Yoseph; Xue, Tianji; Lih, Shyh-Shiuh

    1996-01-01

    Piezoelectric polymers are associated with a low noise and inherent damping that makes them very effective receivers as well as broadband transmitters for high frequencies tasks. This paper reviews polymer piezoelectric materials, the origin of their piezoelectric behavior and their applications to ultrasonic NDE.

  14. High Voltage Piezoelectric System for Generating Neutrons

    DTIC Science & Technology

    2013-06-01

    Piezoelectric transformer structural modeling - a review,” Ultrasonics , Ferroelectrics and Frequency Control, IEEE Transactions on, vol. 54, pp...1 High Voltage Piezoelectric System for Generating Neutrons Brady Gall, Student Member, IEEE, Scott D. Kovaleski, Senior Member, IEEE, James A...Compact electrical neutron generators are a desir- able alternative to radioisotope neutron sources. A piezoelectric transformer system is presented

  15. Piezoelectric and electrostrictive materials for transducer applications

    NASA Astrophysics Data System (ADS)

    Cross, L. E.; Newnham, R. E.; Barsch, G. R.; Biggers, J. V.

    1986-07-01

    On the topic of piezoelectric composites, work over the year has focused primarily upon materials with 0:3 phase connectivity. Using chemically co-precipitated powders with high purity and surface perfection, it has been possible to raise the poling field substantially and realize markedly improved properties in lead titanate based materials. X-ray measurements confirm excellent poling and the dhgh figure of merit of 4200x10 to the minus 15th power sq m/N is comparable to the best NGK materials. Work on fired composites which use a low temperature pre-firing yield materials with high d33 and gh values which pole at low fields. New studies of piezoelectrics generated using paint technology permit surprisingly high powder loading and show promising properties for large area receptors. Modelling studies of Safari type 3:1 and 3:2 composites using finite element methods show excellent agreement with measured properties and provide new insights into complex stress distributions in Holey composites. To explore the possibility of patterning ceramics by semiconductor type techniques, etches have been explored for PZT family materials and photo resist defined structures have been produced. In electrostriction, the basic theoretical work has continued upon CaF2, SrF2 and BaF2. Good agreement is found for calculations of third order elastic constants, and for hydrostatic electrostriction, but Q11 and Q12 show large discrepancies with both theoretical models tried.

  16. Piezoelectric Micro- and Nanostructured Fibers Fabricated from Thermoplastic Nanocomposites Using a Fiber Drawing Technique: Comparative Study and Potential Applications.

    PubMed

    Lu, Xin; Qu, Hang; Skorobogatiy, Maksim

    2017-02-28

    We report an all-polymer flexible piezoelectric fiber that uses both judiciously chosen geometry and advanced materials in order to enhance fiber piezoelectric response. The microstructured/nanostructured fiber features a soft hollow polycarbonate core surrounded by a spiral multilayer cladding consisting of alternating layers of piezoelectric nanocomposites (polyvinylidene enhanced with BaTiO3, PZT, or CNT) and conductive polymer (carbon-filled polyethylene). The conductive polymer layers serve as two electrodes, and they also form two spatially offset electric connectors on the fiber surface designed for the ease of connectorization. Kilometer-long piezoelectric fibers of sub-millimeter diameters are thermally drawn from a macroscopic preform. The fibers exhibit high output voltage of up to 6 V under moderate bending, and they show excellent mechanical and electrical durability in a cyclic bend-release test. The micron/nanosize multilayer structure enhances in-fiber poling efficiency due to the small distance between the conducting electrodes sandwiching the piezoelectric composite layers. Additionally, the spiral structure greatly increases the active area of the piezoelectric composite, thus promoting higher voltage generation and resulting in 10-100 higher power generation efficiency over the existing piezoelectric cables. Finally, we weave the fabricated piezoelectric fibers into technical textiles and demonstrate their potential applications in power generation when used as a sound detector, smart car seat upholstery, or wearable materials.

  17. Ferroelectric, piezoelectric, and dielectric properties of BiScO{sub 3}-PbTiO{sub 3}-Pb(Cd{sub 1/3}Nb{sub 2/3})O{sub 3} ternary high temperature piezoelectric ceramics

    SciTech Connect

    Zhao Tianlong; Chen Jianguo; Dong Shuxiang; Wang Chunming; Yu Yang

    2013-07-14

    (0.95-x)BiScO{sub 3}-xPbTiO{sub 3}-0.05Pb(Cd{sub 1/3}Nb{sub 2/3})O{sub 3} (BS-xPT-PCN) high temperature piezoelectric ceramics near the morphotropic phase boundary (MPB) have been synthesized by traditional solid-state reaction methods. The microstructural morphology, phase structure, and electrical properties of BS-xPT-PCN ceramics were investigated in detail. X-ray diffraction analysis indicated BS-xPT-PCN ceramics have a pure perovskite structure. The coexistence of rhombohedral and tetragonal phases at MPB composition enhanced the polarizability by the coupling between two dynamically equivalent energy states, resulting in the improved piezoelectric and ferroelectric properties at MPB vicinity. The BS-xPT-PCN (x = 0.60) ceramics possess the optimal piezoelectric and ferroelectric properties with d{sub 33} = 505pC/N, k{sub p} = 55.9%, k{sub t} = 36.5%, strain = 0.23% (under the electric field 37.5 kV/cm), and P{sub r} = 39.7 {mu}C/cm{sup 2}. High temperature dielectric behaviors showed diffuse phase transition in BS-xPT-PCN ceramics. The Curie temperature T{sub c} was found to increase from 371 Degree-Sign C to 414 Degree-Sign C with x increasing from 0.58 to 0.62. All these results together with the good thermal stabilities make the BS-xPT-PCN ceramics promising candidates for high temperature piezoelectric applications.

  18. Flexible nano-ZnO/polyvinylidene difluoride piezoelectric composite films as energy harvester

    NASA Astrophysics Data System (ADS)

    Bhunia, Ritamay; Das, Shirsendu; Dalui, Saikat; Hussain, Shamima; Paul, Rajib; Bhar, Radhaballav; Pal, Arun Kumar

    2016-07-01

    Nanogenerators (NGs) which harvest energy from mechanical vibration have attracted more attention in the past decade. Piezoelectric materials are the most promising candidates for developing NGs. Flexible free-standing nano-ZnO/PVDF composite films are prepared by incorporating different amounts of nano-ZnO fillers in PVDF matrix using sol-gel technique. Poled films show enhanced dielectric constant. The above free-standing films, with appropriate contacts, are subjected to energy harvesting studies. The output voltage increases with nano-ZnO loading in the PVDF matrix and shows enhanced effect for the poled films. Piezoelectric properties are investigated by measuring the piezoelectric charge constant ( d 33) and piezoelectric voltage constant ( g 33). A maximum AC output voltage ~4 V and output power of the order of few nanowatts are recorded for the nanogenerator which is used to light a red LED using a rectifying circuit through the discharging of a capacitor.

  19. Optimization of energy harvesting based on the uniform deformation of piezoelectric ceramic

    NASA Astrophysics Data System (ADS)

    Liu, Yaoze; Yang, Tongqing; Shu, Fangming

    2016-09-01

    Since the piezoelectric properties were used for energy harvesting, almost all forms of energy harvester needs to be bonded with a mass block to achieve pre-stress. In this article, disc type piezoelectric energy harvester is chosen as the research object and the relationship between mass bonding area and power output is studied. It is found that if the bonding area is changed as curved, which is usually complanate in previous studies, the deformation of the circular piezoelectric ceramic is more uniform and the power output is enhanced. In order to test the change of the deformation, we spray several homocentric annular electrodes on the surface of a piece of bare piezoelectric ceramic and the output of each electrode is tested. Through this optimization method, the power output is enhanced to more than 11mW for a matching load about 24kΩ and a tip mass of 30g at its resonant frequency of 139Hz.

  20. Giant field enhancement in anisotropic epsilon-near-zero films (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Kamandi, Mohammad; Guclu, Caner; Capolino, Filippo

    2016-09-01

    We investigated anisotropic epsilon-near-zero (AENZ) films under TM-polarized plane wave incidence and found they possess peculiar properties. In particular we studied uniaxially anisotropic films where either the permittivity along the surface normal or along the transverse plane tends to zero while the other one does not. Previously, numerous applications of isotropic epsilon-near-zero (ENZ) films including radiation pattern tailoring, enhanced harmonic generation, optical bistability and energy squeezing have been studied. A notable property of these materials is the capability of enhancing electric field. In this paper the capability of AENZ films in local electric field enhancement has been quantified and several AENZ conditions are reported with superior performance in comparison to (isotropic) ENZ films. Specifically, sensitivity to film thickness and losses, and the range of angles of incidence have been elaborated with the aim of achieving large electric field enhancement in the film. It has been proved that in comparison to the (isotropic) ENZ case the AENZ film's field enhancement is not only much larger but it also occurs for a wider range of angles of incidence. Furthermore the field enhancement in AENZ does not exhibit significant dependence on the film thickness unlike the isotropic case. The effect of loss on the value of the field enhancement is also investigated emphasizing the advantages of AENZ versus ENZ. Realization of AENZ materials can be done by a multilayered media made of a stack of conductive and insulator layers or by stacking semiconductor layers. This giant field enhancement is an important target in nonlinear optics for applications like second harmonic generation and other applications like light generation

  1. Note: Enhanced energy harvesting from low-frequency magnetic fields utilizing magneto-mechano-electric composite tuning-fork.

    PubMed

    Yang, Aichao; Li, Ping; Wen, Yumei; Yang, Chao; Wang, Decai; Zhang, Feng; Zhang, Jiajia

    2015-06-01

    A magnetic-field energy harvester using a low-frequency magneto-mechano-electric (MME) composite tuning-fork is proposed. This MME composite tuning-fork consists of a copper tuning fork with piezoelectric Pb(Zr(1-x)Ti(x))O3 (PZT) plates bonded near its fixed end and with NdFeB magnets attached at its free ends. Due to the resonance coupling between fork prongs, the MME composite tuning-fork owns strong vibration and high Q value. Experimental results show that the proposed magnetic-field energy harvester using the MME composite tuning-fork exhibits approximately 4 times larger maximum output voltage and 7.2 times higher maximum power than the conventional magnetic-field energy harvester using the MME composite cantilever.

  2. Theoretical analysis of 1D resonant tunneling behavior in ion-enhanced cold field and thermo-field emission

    NASA Astrophysics Data System (ADS)

    Tan, Xi; Rumbach, Paul; Griggs, Nathaniel; Jensen, Kevin L.; Go, David B.

    2016-12-01

    In cold field and thermo-field emission, positive ions or adsorbates very close to the cathode surface can enhance emission current by both resonant and non-resonant processes. In this paper, resonant tunneling behavior is investigated by solving the one-dimensional Schrödinger equation in the presence of an ion, and the enhancement due to resonant processes is evaluated. Results shows that as the applied electric field increases, the resonant states move from higher to lower energies as the ion energy levels are shifted down. Conversely, as the ion position moves closer to the cathode, the resonant states shift up in energy. Further, through a simplified perturbation analysis, the general scaling of these trends can be predicted. These shifts of resonant states directly impact the emission current density, and they are especially relevant when the applied field is on the order of a few volts per nanometer (˜0.5-3 V/nm) and the ion is a few nanometers (˜0.5-3 nm) away from the cathode. Further, when the energy level for resonant emission coincides with the Fermi level of a metallic cathode, the current density is particularly enhanced. The results of this study suggest that it may be possible to control (augment/inhibit) the resonant emission current by manipulating the supply function of a cathode relative to the operating conditions of the emitter in either ion-enhanced or adsorbate-enhanced field emission, which can be applied to various plasma and electron emission technologies.

  3. Moving through Moodle: Using E-Technology to Enhance Social Work Field Education

    ERIC Educational Resources Information Center

    Hay, Kathryn; Dale, Michael

    2014-01-01

    At Massey University, New Zealand, the Moodle program was introduced as an institutional innovation to support and enhance teaching and learning. Within the social work field education program Moodle has been embraced as an opportunity to creatively advance current educational practices. The development of a meta-site for field education enables…

  4. Geometrical parameters effects on local electric field enhancement of silver-dielectric-silver multilayer nanoshell

    SciTech Connect

    Shirzaditabar, Farzad; Saliminasab, Maryam

    2013-05-15

    The local electric field enhancement at different points of silver-dielectric-silver nanoshell is investigated using quasi-static theory. Because of the symmetric and anti-symmetric coupling between surface plasmon of inner silver core and outer silver shell, the local electric field spectrum of silver-dielectric-silver has two distinct peaks at resonance wavelengths. The silver core size and middle dielectric thickness affect the local electric field enhancement at different points of silver-dielectric-silver nanoshell. Increasing the silver core radius always leads to blue shift of shorter resonance wavelength and red shift of longer resonance wavelength. We observed two distinct local electric field peaks, which are corresponded to the symmetric and anti-symmetric coupling between inner and outer surface plasmons. In a system with thick silver shell, local electric field enhancement is greater than a system with thin silver shell. However, the local electric field variations as a function of silver core radius in both systems are different at different points of nanoshell. The effects of the dielectric thickness variations on local electric field are different from those from silver core size variations. As the dielectric thickness is about 3 nm, the highest local electric field enhancement occurs at the surface of the inner silver core, where the symmetric and anti-symmetric modes are mixed together.

  5. Evaluation of enhanced recovery operations in Smackover fields of southwest Alabama. Draft topical report on Subtasks 5 and 6

    SciTech Connect

    Hall, D.R.

    1992-06-01

    This report contains detailed geologic and engineering information on enhanced-recovery techniques used in unitized Smackover fields in Alabama. The report also makes recommendations on the applicability of these enhanced-recovery techniques to fields that are not now undergoing enhanced recovery. Eleven Smackover fields in Alabama have been unitized. Three fields were unitized specifically to allow the drilling of a strategically placed well to recover uncontacted oil. Two fields in Alabama are undergoing waterflood projects. Five fields are undergoing gas-injection programs to increase the ultimate recovery of hydrocarbons. Silas and Choctaw Ridge fields were unitized but no enhanced-recovery operations have been implemented.

  6. Microstructure and electrical properties in W/Nb co-doped Aurivillius phase Bi{sub 4}Ti{sub 3}O{sub 12} piezoelectric ceramics

    SciTech Connect

    Peng, Zhihang; Chen, Qiang; Chen, Yu; Xiao, Dingquan; Zhu, Jianguo

    2014-11-15

    Highlights: • W/Nb codoped BIT ceramics were prepared by the mixed oxides route. • High nd{sup 0} electronic configuration of W/Nb reduces the lattice distortion and T{sub C}. • Oxygen vacancy is responsible for dielectric relaxation and DC conduction process. • W/Nb additives significantly enhanced the piezoelectric coefficient d{sub 33} value. • BWNb-10 ceramics possessed large remnant polarization and a wide sintering window. - Abstract: Aurivillius-type Bi{sub 4}Ti{sub 3-x}W{sub x/2}Nb{sub x/2}O{sub 12} ceramics were prepared by a conventional solid-state sintering method. The XRD patterns demonstrated that all compositions were a single three layered crystalline structure, involving a reduction of lattice distortion with an increase in W/Nb doping level. The electrical properties including dielectric, electrical conduction and piezoelectric properties were tailored by W/Nb additives. The Curie-temperature decreased, whereas the electrical resistivity drastically increased with introduction of W/Nb donor dopants. As a result, a high electric field can be applied during the poling process. The Bi{sub 4}Ti{sub 2.9}W{sub 0.05}Nb{sub 0.05}O{sub 12} ceramics exhibited optimum piezoelectric coefficient (d{sub 33} ∼22.8 pC/N), large remnant polarization (2P{sub r} ∼26.8 μC/cm{sup 2} @ 200 °C) together with a high Curie temperature (T{sub C} ∼635 °C). Furthermore, this composition possessed a wide sintering window with outstanding piezoelectric properties. These parameters indicate that Bi{sub 4}Ti{sub 2.9}W{sub 0.05}Nb{sub 0.05}O{sub 12}-based ceramic is a promising candidate for high temperature piezoelectric applications.

  7. Enhancing the electric fields around the nanorods by using metal grooves

    NASA Astrophysics Data System (ADS)

    Zhao, YaNan; Qin, Yan; Cao, Wei; Zhang, ZhongYue

    2012-10-01

    To enhance electric fields around nanorods, a Ag nanorod-groove system is presented and its electric field distribution is studied using the finite difference time domain method. Since the superposition of the electric fields of the split multi-beam of light works as excitation for electron oscillations in the nanorods, enhanced electric fields occur around the nanorods. In addition, the effects of topological parameters of the nanorod-groove system, such as the oblique angle of the groove, displacement of the nanorod to the bottom of the groove, and separation between the nanorods on electric field distributions are also studied. These results may be helpful for designing substrates to obtain larger electric fields around nanorods.

  8. Highly Sensitive and Robust Damage Detection of Periodic Structures with Piezoelectric Networking

    DTIC Science & Technology

    2008-05-01

    REPORT TYPE Final 3. DATES COVERED (From - To) December 15. 2006 to May 3 1. 2008 4. TITLE AND SUBTITLE Highly Sensitive and Robust Damage...localization characteristics of such periodic structures to enhance damage detection sensitivity and robustness through piezoelectric circuitry...ANSI Sid Z39 18 Adobe Professional 7.0 Highly Sensitive and Robust Damage Detection of Periodic Structures with Piezoelectric Networking GRANT

  9. The effects of polymer morphology and single-wall carbon nanotubes on biopolymer shear piezoelectricity

    NASA Astrophysics Data System (ADS)

    Lovell, Conrad

    Discovered over fifty years ago, the shear piezoelectric effect occurs in biopolymers that possess chirality due to asymmetric backbone carbon atoms. This dissertation focuses on the mechanisms responsible for shear piezoelectricity, as well as methods to improve the multifunctionality of these materials without degrading their shear piezoelectricity. Previous research has determined that shear piezoelectricity is a function of polymer crystallinity and orientation. At the present time, investigations concerning the effects of these parameters are incomplete since previous studies have relied exclusively on using orientation to alter crystallinity. In this research, polylactic acid (PLA) samples were fabricated by a twofold drawing/annealing process to investigate further the relationship between crystallinity, orientation, and shear piezoelectricity. The results of this study reveal that the product of crystallinity and orientation determines shear piezoelectricity regardless of either parameter's individual magnitude. Methods to prepare these typically weak biopolymers for potential applications were also examined. Single-wall carbon nanotubes (SWCNTs) have previously been incorporated into polymers to introduce multifunctionality, but their effects on shear piezoelectricity are unknown. In order to achieve thorough dispersion in these materials, the copolypeptide poly (leucine-ran-phenylalanine) (polyLF) was engineered to exhibit favorable interactions with SWCNTs. The enthalpic and entropic penalties of mixing between these molecules were reduced due to the copolypeptide's aromatic sidechains and their similar size/shape, respectively. This study is the first to demonstrate the dual enthalpic/entropic approach in mixtures of SWCNTs and a high molecular weight polypeptide. The enhanced interactions result in a well-dispersed SWCNT/polyLF nanocomposite with improved multifunctionality. A third polymer, poly (gamma-benzyl-L-glutamate) (PBLG), which exhibits

  10. Droplet condensation on superhydrophobic surfaces with enhanced dewetting under a tangential AC electric field

    NASA Astrophysics Data System (ADS)

    Yan, Xinzhu; Li, Jian; Li, Licheng; Huang, Zhengyong; Wang, Feipeng; Wei, Yuan

    2016-10-01

    In this Letter, the dewetting behavior of superhydrophobic condensing surfaces under a tangential AC electric field is reported. The surface coverage of condensed droplets only exhibits a negligible increase with time. The jumping frequency of droplets is enhanced. The AC electric field motivates the dynamic transition of droplets from stretch to recoil, resulting in the counterforce propelling droplet jumping. The considerable horizontal component of jumping velocity facilitates droplet departure from superhydrophobic surfaces. Both the amplitude and frequency of AC voltage are important factors for droplet departure and dewetting effect. Thereby, the tangential electric field provides a unique and easily implementable approach to enhance droplet removal from superhydrophobic condensing surfaces.

  11. Electrostatic-field-enhanced photoexfoliation of bilayer benzene: A first-principles study

    NASA Astrophysics Data System (ADS)

    Uchida, Kazuki; Silaeva, Elena P.; Watanabe, Kazuyuki

    2016-06-01

    Photoexfoliation of bilayer benzene in an external electrostatic (dc) field is studied using time-dependent density functional theory combined with molecular dynamics. We find that the dc-field-induced force on the upper benzene in addition to the repulsive interaction between the positively charged benzene molecules induced by the laser field leads to fast athermal exfoliation. Thus, we conclude that the dc field enhances the photoexfoliation due to dc-field emission in addition to laser-assisted photoemission. The athermal exfoliation process is shown to depend crucially on the charge state of benzene molecules rather than on the excitation energy supplied by the laser.

  12. Electric-field enhanced performance in catalysis and solid-state devices involving gases

    DOEpatents

    Blackburn, Bryan M.; Wachsman, Eric D.; Van Assche, IV, Frederick Martin

    2015-05-19

    Electrode configurations for electric-field enhanced performance in catalysis and solid-state devices involving gases are provided. According to an embodiment, electric-field electrodes can be incorporated in devices such as gas sensors and fuel cells to shape an electric field provided with respect to sensing electrodes for the gas sensors and surfaces of the fuel cells. The shaped electric fields can alter surface dynamics, system thermodynamics, reaction kinetics, and adsorption/desorption processes. In one embodiment, ring-shaped electric-field electrodes can be provided around sensing electrodes of a planar gas sensor.

  13. Fast Ignition Thermonuclear Fusion: Enhancement of the Pellet Gain by the Colossal-Magnetic-Field Shells

    NASA Astrophysics Data System (ADS)

    Stefan, V. Alexander

    2013-10-01

    The fast ignition fusion pellet gain can be enhanced by a laser generated B-field shell. The B-field shell, (similar to Earth's B-field, but with the alternating B-poles), follows the pellet compression in a frozen-in B-field regime. A properly designed laser-pellet coupling can lead to the generation of a B-field shell, (up to 100 MG), which inhibits electron thermal transport and confines the alpha-particles. In principle, a pellet gain of few-100s can be achieved in this manner. Supported in part by Nikola Tesla Labs, Stefan University, 1010 Pearl, La Jolla, CA 92038-1007.

  14. Plasmonic tooth-multilayer structure with high enhancement field for surface enhanced Raman spectroscopy.

    PubMed

    Huang, Li-Chung; Wang, Zhiyu; Clark, J Kenji; Ho, Ya-Lun; Delaunay, Jean-Jacques

    2017-03-24

    The significant enhancement seen in surface-enhanced Raman scattering (SERS) heavily relies on the ability of plasmonic structures to strongly confine light. Current techniques used to fabricate plasmonic nanostructures have been limited in their reproducibility for bottom-up techniques or their feature size for top-down techniques. Here, we propose a tooth multilayer structure that can be fabricated by using physical vapor deposition and selective wet etching, achieving extremely small feature sizes and high reproducibility. A multilayer structure composed of two alternating materials whose thicknesses can be controlled accurately in the nanometer range is deposited on a flat substrate using ion-beam sputtering. Subsequent selective wet etching is used to form nanogaps in one of the materials constituting the multilayer, with the depth of the nanogaps being controlled by the wet etching time. Combining both techniques can allow the nanogap dimensions to be controlled at sub 10 nm length scale, thus achieving a tooth multilayer structure with high enhancement and tunability of the resonance mode over a broad range, ideal for SERS applications.

  15. Resonant enhancement for amplitude-modulated laser filament induced magnetic field in an inhomogeneous plasma

    NASA Astrophysics Data System (ADS)

    Annou, R.; Tripathi, V. K.; Srivastava, M. P.

    1996-09-01

    The Tripathi-Liu [Phys. Plasmas 1, 990 (1994)] model of magnetic-field generation due to an amplitude-modulated laser in a plasma is revisited. At plasma resonance, where modulation frequency equals the plasma frequency, significant enhancement in the magnetic field is seen. The magnetic field is found to scale directly with laser intensity and plasma frequency, while scaling inversely with laser spot size.

  16. Bias-enhanced post-treatment process for enhancing the electron field emission properties of ultrananocrystalline diamond films

    SciTech Connect

    Saravanan, A.; Huang, B. R.; Sankaran, K. J.; Tai, N. H.; Dong, C. L.; Lin, I. N.

    2015-03-16

    The electron field emission (EFE) properties of ultrananocrystalline diamond films were markedly improved via the bias-enhanced plasma post-treatment (bep) process. The bep-process induced the formation of hybrid-granular structure of the diamond (bep-HiD) films with abundant nano-graphitic phase along the grain boundaries that increased the conductivity of the films. Moreover, the utilization of Au-interlayer can effectively suppress the formation of resistive amorphous-carbon (a-C) layer, thereby enhancing the transport of electrons crossing the diamond-to-Si interface. Therefore, bep-HiD/Au/Si films exhibit superior EFE properties with low turn-on field of E{sub 0} = 2.6 V/μm and large EFE current density of J{sub e} = 3.2 mA/cm{sup 2} (at 5.3 V/μm)

  17. Piezoelectric and electrostrictive sensors and actuators for adaptive structures and smart materials

    NASA Astrophysics Data System (ADS)

    Cross, L. E.

    Developments in composite materials for piezoelectric sensors are briefly reviewed, and new systems using bias field control of the piezoelectric response in relaxor ferroelectric compositions in the PMN:PT and in the PLZT family materials are discussed. For actuator applications, multilayer actuator materials are evaluated, and possibilities for ultrahigh-strain materials are explored. Attention is also given to the composite systems incorporating both a sensor and a responder in the same material together with active solid state electronics. It is shown that a piezoelectric sensor/actuator system mimics an ultrasoft material for weak AC stress, maintaining the load-bearing capability of a stiff ceramic.

  18. Torsion analysis of cracked circular bars actuated by a piezoelectric coating

    NASA Astrophysics Data System (ADS)

    Hassani, A. R.; Faal, R. T.

    2016-12-01

    This study presents a formulation for a bar with circular cross-section, coated by a piezoelectric layer and subjected to Saint-Venant torsion loading. The bar is weakened by a Volterra-type screw dislocation. First, with aid of the finite Fourier transform, the stress fields in the circular bar and the piezoelectric layer are obtained. The problem is then reduced to a set of singular integral equations with a Cauchy-type singularity. Unknown dislocation density is achieved by numerical solution of these integral equations. Numerical results are discussed, to reveal the effect of the piezoelectric layer on the reduction of the mechanical stress intensity factor in the bar.

  19. Electric near-field enhancing properties of a finite-size metal conical nano-tip.

    PubMed

    Goncharenko, A V; Chang, Hung-Chih; Wang, Juen-Kai

    2007-01-01

    Finite-difference time-domain (FDTD) technique simulations are performed to study the near-field resonance properties of a silver conical nano-tip with a rounded end. Varying the tip geometry, we have computed the electric field distribution, as well as the electric field enhancement factor in the immediate vicinity of the tip apex. The aim of this study is to find optimal geometric parameters of the conical tip, such as its angle and length, in order to maximize the electric field enhancement factor. The increase of the tip length is shown to result in a redshift of the tip resonance wavelength. In addition, some subsidiary (non-dipole) peaks appear for relatively long tips. The peak enhancement values for the small-angle tips increase with the tip length while those for the large-angle ones decrease with it. At the same time, the dependencies of the field enhancement on the cone angle exhibit non-monotonic behavior. In other words, an optimal angle exists allowing one to maximize the electric near field. Finally, the effect of the supporting dielectric medium on the electric field near the tip apex is discussed. In the approximation used, the effect is shown to leave the main conclusions unchanged.

  20. Giant strain with ultra-low hysteresis and high temperature stability in grain oriented lead-free K0.5Bi0.5TiO3-BaTiO3-Na0.5Bi0.5TiO3 piezoelectric materials

    PubMed Central

    Maurya, Deepam; Zhou, Yuan; Wang, Yaojin; Yan, Yongke; Li, Jiefang; Viehland, Dwight; Priya, Shashank

    2015-01-01

    We synthesized grain-oriented lead-free piezoelectric materials in (K0.5Bi0.5TiO3-BaTiO3-xNa0.5Bi0.5TiO3 (KBT-BT-NBT) system with high degree of texturing along the [001]c (c-cubic) crystallographic orientation. We demonstrate giant field induced strain (~0.48%) with an ultra-low hysteresis along with enhanced piezoelectric response (d33 ~ 190pC/N) and high temperature stability (~160°C). Transmission electron microscopy (TEM) and piezoresponse force microscopy (PFM) results demonstrate smaller size highly ordered domain structure in grain-oriented specimen relative to the conventional polycrystalline ceramics. The grain oriented specimens exhibited a high degree of non-180° domain switching, in comparison to the randomly axed ones. These results indicate the effective solution to the lead-free piezoelectric materials. PMID:25716551

  1. Giant strain with ultra-low hysteresis and high temperature stability in grain oriented lead-free K₀̣₅Bi₀̣₅TiO₃-BaTiO₃-Na₀̣₅Bi₀̣₅TiO₃ piezoelectric materials

    SciTech Connect

    Maurya, Deepam; Zhou, Yuan; Wang, Yaojin; Yan, Yongke; Li, Jiefang; Viehland, Dwight; Priya, Shashank

    2015-02-26

    We synthesized grain-oriented lead-free piezoelectric materials in (K₀̣₅Bi₀̣₅TiO₃-BaTiO₃-xNa₀̣₅Bi₀̣₅TiO₃ (KBT-BT-NBT) system with high degree of texturing along the [001]c (c-cubic) crystallographic orientation. We demonstrate giant field induced strain (~0.48%) with an ultra-low hysteresis along with enhanced piezoelectric response (d₃₃ ~ 190pC/N) and high temperature stability (~160°C). Transmission electron microscopy (TEM) and piezoresponse force microscopy (PFM) results demonstrate smaller size highly ordered domain structure in grain-oriented specimen relative to the conventional polycrystalline ceramics. The grain oriented specimens exhibited a high degree of non-180° domain switching, in comparison to the randomly axed ones. These results indicate the effective solution to the lead-free piezoelectric materials.

  2. Method of Fabricating a Piezoelectric Composite Apparatus

    NASA Technical Reports Server (NTRS)

    Wilkie, W. Keats (Inventor); Bryant, Robert (Inventor); Fox, Robert L. (Inventor); Hellbaum, Richard F. (Inventor); High, James W. (Inventor); Jalink, Antony, Jr. (Inventor); Little, Bruce D. (Inventor); Mirick, Paul H. (Inventor)

    2003-01-01

    A method for fabricating a piezoelectric macro-fiber composite actuator comprises providing a piezoelectric material that has two sides and attaching one side upon an adhesive backing sheet. The method further comprises slicing the piezoelectric material to provide a plurality of piezoelectric fibers in juxtaposition. A conductive film is then adhesively bonded to the other side of the piezoelectric material, and the adhesive backing sheet is removed. The conductive film has first and second conductive patterns formed thereon which are electrically isolated from one another and in electrical contact with the piezoelectric material. The first and second conductive patterns of the conductive film each have a plurality of electrodes to form a pattern of interdigitated electrodes. A second film is then bonded to the other side of the piezoelectric material. The second film may have a pair of conductive patterns similar to the conductive patterns of the first film.

  3. Piezoelectric materials used in underwater acoustic transducers

    SciTech Connect

    Li, Huidong; Deng, Zhiqun; Carlson, Thomas J.

    2012-07-07

    Piezoelectric materials have been used in underwater acoustic transducers for nearly a century. In this paper, we reviewed four different types of piezoelectric materials: piezoelectric ceramics, single crystals, composites, and polymers, which are widely used in underwater acoustic transducers nowadays. Piezoelectric ceramics are the most dominant material type and are used as a single-phase material or one of the end members in composites. Piezoelectric single crystals offer outstanding electromechanical response but are limited by their manufacturing cost. Piezoelectric polymers provide excellent acoustic impedance matching and transducer fabrication flexibility although their piezoelectric properties are not as good as ceramics and single crystals. Composites combined the merits of ceramics and polymers and are receiving increased attention. The typical structure and electromechanical properties of each type of materials are introduced and discussed with respect to underwater acoustic transducer applications. Their advantages and disadvantages are summarized. Some of the critical design considerations when developing underwater acoustic transducers with these materials are also touched upon.

  4. Heat transfer enhancement with mixing vane spacers using the field synergy principle

    NASA Astrophysics Data System (ADS)

    Yang, Lixin; Zhou, Mengjun; Tian, Zihao

    2017-01-01

    The single-phase heat transfer characteristics in a PWR fuel assembly are important. Many investigations attempt to obtain the heat transfer characteristics by studying the flow features in a 5 × 5 rod bundle with a spacer grid. The field synergy principle is used to discuss the mechanism of heat transfer enhancement using mixing vanes according to computational fluid dynamics results, including a spacer grid without mixing vanes, one with a split mixing vane, and one with a separate mixing vane. The results show that the field synergy principle is feasible to explain the mechanism of heat transfer enhancement in a fuel assembly. The enhancement in subchannels is more effective than on the rod's surface. If the pressure loss is ignored, the performance of the split mixing vane is superior to the separate mixing vane based on the enhanced heat transfer. Increasing the blending angle of the split mixing vane improves heat transfer enhancement, the maximum of which is 7.1%. Increasing the blending angle of the separate mixing vane did not significantly enhance heat transfer in the rod bundle, and even prevented heat transfer at a blending angle of 50°. This finding testifies to the feasibility of predicting heat transfer in a rod bundle with a spacer grid by field synergy, and upon comparison with analyzed flow features only, the field synergy method may provide more accurate guidance for optimizing the use of mixing vanes.

  5. Consideration of impedance matching techniques for efficient piezoelectric energy harvesting.

    PubMed

    Kim, Hyeoungwoo; Priya, Shashank; Stephanou, Harry; Uchino, Kenji

    2007-09-01

    This study investigates multiple levels of impedance-matching methods for piezoelectric energy harvesting in order to enhance the conversion of mechanical to electrical energy. First, the transduction rate was improved by using a high piezoelectric voltage constant (g) ceramic material having a magnitude of g33 = 40 x 10(-3) V m/N. Second, a transducer structure, cymbal, was optimized and fabricated to match the mechanical impedance of vibration source to that of the piezoelectric transducer. The cymbal transducer was found to exhibit approximately 40 times higher effective strain coefficient than the piezoelectric ceramics. Third, the electrical impedance matching for the energy harvesting circuit was considered to allow the transfer of generated power to a storage media. It was found that, by using the 10-layer ceramics instead of the single layer, the output current can be increased by 10 times, and the output load can be reduced by 40 times. Furthermore, by using the multilayer ceramics the output power was found to increase by 100%. A direct current (DC)-DC buck converter was fabricated to transfer the accumulated electrical energy in a capacitor to a lower output load. The converter was optimized such that it required less than 5 mW for operation.

  6. Communication: Multiple atomistic force fields in a single enhanced sampling simulation

    SciTech Connect

    Hoang Viet, Man; Derreumaux, Philippe; Nguyen, Phuong H.

    2015-07-14

    The main concerns of biomolecular dynamics simulations are the convergence of the conformational sampling and the dependence of the results on the force fields. While the first issue can be addressed by employing enhanced sampling techniques such as simulated tempering or replica exchange molecular dynamics, repeating these simulations with different force fields is very time consuming. Here, we propose an automatic method that includes different force fields into a single advanced sampling simulation. Conformational sampling using three all-atom force fields is enhanced by simulated tempering and by formulating the weight parameters of the simulated tempering method in terms of the energy fluctuations, the system is able to perform random walk in both temperature and force field spaces. The method is first demonstrated on a 1D system and then validated by the folding of the 10-residue chignolin peptide in explicit water.

  7. Effect of the magnetic field direction on forced convection heat transfer enhancements in ferrofluids

    NASA Astrophysics Data System (ADS)

    Cherief, Wahid; Avenas, Yvan; Ferrouillat, Sébastien; Kedous-Lebouc, Afef; Jossic, Laurent; Berard, Jean; Petit, Mickael

    2015-07-01

    Applying a magnetic field on a ferrofluid flow induces a large increase of the convective heat transfer coefficient. In this paper, the thermal-hydraulic behaviors of two commercial ferrofluids are compared. The variations of both the pressure drop and the heat transfer coefficient due to the magnetic field are measured in the following conditions: square duct, laminar flow and uniform wall heat flux. The square section with two insulated walls allows for the characterization of the effect of the magnetic field direction. The experimental results show that the heat transfer is better enhanced when the magnetic field is perpendicular to the heat flux. In the best case, the local heat transfer coefficient increase is about 75%. On the contrary, another experimental setup shows no enhancement of thermal conductivity when the magnetic field is perpendicular to the heat flux. Contribution to the topical issue "Electrical Engineering Symposium (SGE 2014) - Elected submissions", edited by Adel Razek

  8. Graphene as a Massless Electrode for Ultrahigh-Frequency Piezoelectric Nanoelectromechanical Systems.

    PubMed

    Qian, Zhenyun; Liu, Fangze; Hui, Yu; Kar, Swastik; Rinaldi, Matteo

    2015-07-08

    Designing "ideal electrodes" that simultaneously guarantee low mechanical damping and electrical loss as well as high electromechanical coupling in ultralow-volume piezoelectric nanomechanical structures can be considered to be a key challenge in the NEMS field. We show that mechanically transferred graphene, floating at van der Waals proximity, closely mimics "ideal electrodes" for ultrahigh frequency (0.2 GHz < f0 < 2.6 GHz) piezoelectric nanoelectromechanical resonators with negligible mechanical mass and interfacial strain and perfect radio frequency electric field confinement. These unique attributes enable graphene-electrode-based piezoelectric nanoelectromechanical resonators to operate at their theoretically "unloaded" frequency-limits with significantly improved electromechanical performance compared to metal-electrode counterparts, despite their reduced volumes. This represents a spectacular trend inversion in the scaling of piezoelectric electromechanical resonators, opening up new possibilities for the implementation of nanoelectromechanical systems with unprecedented performance.

  9. Piezoelectric measurement of laser power

    DOEpatents

    Deason, Vance A.; Johnson, John A.; Telschow, Kenneth L.

    1991-01-01

    A method for measuring the energy of individual laser pulses or a series of laser pulses by reading the output of a piezoelectric (PZ) transducer which has received a known fraction of the total laser pulse beam. An apparatus is disclosed that reduces the incident energy on the PZ transducer by means of a beam splitter placed in the beam of the laser pulses.

  10. Cylindrical Piezoelectric Fiber Composite Actuators

    NASA Technical Reports Server (NTRS)

    Allison, Sidney G.; Shams, Qamar A.; Fox, Robert L.

    2008-01-01

    The use of piezoelectric devices has become widespread since Pierre and Jacques Curie discovered the piezoelectric effect in 1880. Examples of current applications of piezoelectric devices include ultrasonic transducers, micro-positioning devices, buzzers, strain sensors, and clocks. The invention of such lightweight, relatively inexpensive piezoceramic-fiber-composite actuators as macro fiber composite (MFC) actuators has made it possible to obtain strains and displacements greater than those that could be generated by prior actuators based on monolithic piezoceramic sheet materials. MFC actuators are flat, flexible actuators designed for bonding to structures to apply or detect strains. Bonding multiple layers of MFC actuators together could increase force capability, but not strain or displacement capability. Cylindrical piezoelectric fiber composite (CPFC) actuators have been invented as alternatives to MFC actuators for applications in which greater forces and/or strains or displacements may be required. In essence, a CPFC actuator is an MFC or other piezoceramic fiber composite actuator fabricated in a cylindrical instead of its conventional flat shape. Cylindrical is used here in the general sense, encompassing shapes that can have circular, elliptical, rectangular or other cross-sectional shapes in the planes perpendicular to their longitudinal axes.

  11. An efficient route to fabricate fatigue-free P(VDF-TrFE) capacitors with enhanced piezoelectric and ferroelectric properties and excellent thermal stability for sensing and memory applications.

    PubMed

    Singh, Deepa; Deepak; Garg, Ashish

    2017-03-15

    P(VDF-TrFE), the best known ferroelectric polymer, suffers from a rather low piezoelectric response as well as poor electrical fatigue life, hampering its application potential. Herein, we report the fabrication of fatigue free poly(vinylidenedifluoride-trifluoroethylene) P(VDF-TrFE)-based capacitors with record piezoelectric coefficients and excellent thermal stability. We proposed a cost-effective and simple solution-based process to fabricate P(VDF-TrFE)-based memory capacitors with large polarization (8.9 μC cm(-2)), low voltage operation (15 V), and excellent fatigue endurance with 100% polarization retention up to 10(8) electrical switching cycles. The thin film capacitors fabricated using methyl ethyl ketone (MEK) and dimethyl sulfoxide (DMSO) as co-solvents also show a much higher piezoelectric coefficient (d33 = -60 pm V(-1)) than the previously reported capacitors and are also thermally stable up to 380 K, making them ideal candidates for ferro-, piezo-, and pyro-electric applications, even in devices operating above room temperature. The observed results are well supported by first principles calculations, FTIR, XPS, and evaluation of cohesion energy for crystallization by DSC.

  12. Amplification of resonant field enhancement by plasmonic lattice coupling in metallic slit arrays

    NASA Astrophysics Data System (ADS)

    Klarskov, Pernille; Tarekegne, Abebe T.; Iwaszczuk, Krzysztof; Zhang, X.-C.; Jepsen, Peter Uhd

    2016-11-01

    Nonlinear spectroscopic investigation in the terahertz (THz) range requires significant field strength of the light fields. It is still a challenge to obtain the required field strengths in free space from table-top laser systems at sufficiently high repetition rates to enable quantitative nonlinear spectroscopy. It is well known that local enhancement of the THz field can be obtained for instance in narrow apertures in metallic films. Here we show by simulation, analytical modelling and experiment that the achievable field enhancement in a two-dimensional array of slits with micrometer dimensions in a metallic film can be increased by at least 60% compared to the enhancement in an isolated slit. The additional enhancement is obtained by optimized plasmonic coupling between the lattice modes and the resonance of the individual slits. Our results indicate a viable route to sensitive schemes for THz spectroscopy with slit arrays manufactured by standard UV photolithography, with local field strengths in the multi-ten-MV/cm range at kHz repetition rates, and tens of kV/cm at oscillator repetition rates.

  13. Amplification of resonant field enhancement by plasmonic lattice coupling in metallic slit arrays

    PubMed Central

    Klarskov, Pernille; Tarekegne, Abebe T.; Iwaszczuk, Krzysztof; Zhang, X.-C.; Jepsen, Peter Uhd

    2016-01-01

    Nonlinear spectroscopic investigation in the terahertz (THz) range requires significant field strength of the light fields. It is still a challenge to obtain the required field strengths in free space from table-top laser systems at sufficiently high repetition rates to enable quantitative nonlinear spectroscopy. It is well known that local enhancement of the THz field can be obtained for instance in narrow apertures in metallic films. Here we show by simulation, analytical modelling and experiment that the achievable field enhancement in a two-dimensional array of slits with micrometer dimensions in a metallic film can be increased by at least 60% compared to the enhancement in an isolated slit. The additional enhancement is obtained by optimized plasmonic coupling between the lattice modes and the resonance of the individual slits. Our results indicate a viable route to sensitive schemes for THz spectroscopy with slit arrays manufactured by standard UV photolithography, with local field strengths in the multi-ten-MV/cm range at kHz repetition rates, and tens of kV/cm at oscillator repetition rates. PMID:27886232

  14. Parity-selective enhancement of field-free molecular orientation in an intense two-color laser field

    SciTech Connect

    Yun, Hyeok; Nam, Chang Hee; Kim, Hyung Taek; Kim, Chul Min; Lee, Jongmin

    2011-12-15

    We investigated the characteristics of molecular orientation induced by a nonresonant two-color femtosecond laser field. By analyzing the rotational dynamics of asymmetric linear molecules, we revealed that the critical parameter in characterizing the molecular orientation was the hyperpolarizability of molecules that selected the excitation paths of rotational states between parity-changing and parity-conserving transitions. Especially, in the case of molecules with small hyperpolarizability, a significant enhancement of orientation was achieved at the half-rotational period, instead of the full-rotational period. This deeper understanding of the hyperpolarizability-dependent characteristics of molecular orientation in a two-color scheme can provide an effective method to achieve significantly enhanced field-free orientation for various polar molecules.

  15. Enhancement of electron field emission property with silver incorporation into diamondlike carbon matrix

    SciTech Connect

    Ahmed, Sk. Faruque; Moon, Myoung-Woon; Lee, Kwang-Ryeol

    2008-05-12

    Effects of silver doping on the electron field emission properties of diamondlike carbon films deposited on silicon substrates by the rf reactive sputtering technique were studied in detail. It was found that the threshold field and effective emission barrier were reduced by Ag doping and the emission current strongly depends on the Ag doping percentage. The threshold field was found to decrease from 6.8 to 2.6 V/{mu}m with a variation of Ag at. % from 0 to 12.5. The field enhancement factor was calculated and we have explained the emission mechanism.

  16. From single III-nitride nanowires to piezoelectric generators: New route for powering nomad electronics

    NASA Astrophysics Data System (ADS)

    Gogneau, N.; Jamond, N.; Chrétien, P.; Houzé, F.; Lefeuvre, E.; Tchernycheva, M.

    2016-10-01

    Ambient energy harvesting using piezoelectric nanomaterials is today considered as a promising way to supply microelectronic devices. Since the first demonstration of electrical energy generation from piezoelectric semiconductor nanowires in 2006, the piezoelectric response of 1D-nanostructures and the development of nanowire-based piezogenerators have become a hot topic in nanoscience. After several years of intense research on ZnO nanowires, III-nitride nanomaterials have started to be explored thanks to their high piezoelectric coefficients and their strong piezogeneration response. This review describes the present status of the field of piezoelectric energy generation with nitride nanowires. After presenting the main motivation and a general overview of the domain, a short description of the main properties of III-nitride nanomaterials is given. Then we review the piezoelectric responses of III-N nanowires and the specificities of the piezogeneration mechanism in these nanostructures. Finally, the design and performance of the macroscopic piezogenerators based on nitride nanowire arrays are described, showing the promise of III-nitride nanowires for ultra-compact and efficient piezoelectric generators.

  17. Finite Size Effects on the Electromagnetic Field Enhancement from Low-dimensional Silver Nanoshell Dimer Arrays

    NASA Astrophysics Data System (ADS)

    Song, Youlin; Zhao, Ke; Jia, Yu; Hu, Xing; Zhang, Zhenyu

    2009-03-01

    Finite size effects on the optical properties of one-dimensional (1D) and 2D nanoshell dimer arrays are investigated using generalized Mie theory and coupled dipole approximation within the context of surface-enhanced Raman spectroscopy (SERS). It is shown that the huge enhancement in the electromagnetic (EM) field at the center of a given dimer oscillates with the length of the 1D array. For an array of fixed length, the EM enhancement also oscillates along the array, but with a different period. Both types of oscillations can be attributed to the interference of the dynamic dipole fields from different dimers in the array. When generalized to 2D arrays, EM enhancement higher than that of the 1D arrays can be gained with a constant magnitude, a salient feature advantageous to experimental realization of single-molecule SERS. [K. Zhao et al, J. Chem. Phys. 125, 081102 (2005); Y. L. Song et al, accepted by J. Chem. Phys.

  18. Finite size effects on the electromagnetic field enhancement from low-dimensional silver nanoshell dimer arrays

    NASA Astrophysics Data System (ADS)

    Song, Youlin; Zhao, Ke; Jia, Yu; Hu, Xing; Zhang, Zhenyu

    2008-11-01

    Finite size effects on the optical properties of one-dimensional (1D) and two-dimensional (2D) nanoshell dimer arrays are investigated using generalized Mie theory and coupled dipole approximation within the context of surface-enhanced Raman spectroscopy (SERS). It is shown that the huge enhancement in the electromagnetic (EM) field at the center of a given dimer oscillates with the length of the 1D array. For an array of fixed length, the EM enhancement also oscillates along the array, but with a different period. Both types of oscillations can be attributed to the interference of the dynamic dipole fields from different dimers in the array. When generalized to 2D arrays, EM enhancement higher than that of the 1D arrays can be gained with a constant magnitude, a salient feature advantageous to experimental realization of single-molecule SERS.

  19. Piezoelectricity and pyroelectricity in polyvinylidene fluoride - Influence of the lattice structure

    NASA Technical Reports Server (NTRS)

    Purvis, C. K.; Taylor, P. L.

    1983-01-01

    Piezoelectric and pyroelectric responses of beta-phase (Phase I) polyvinylidene fluoride are predicted for a model system of polarizable point dipoles. The model incorporates the influence of the orthorhombic crystal structure by including the dependence of the internal electric field on the lattice parameters. Strong anisotropy in the piezoelectric response under uniaxial stress is predicted as a consequence of the orthorhombic lattice structure. Predictions are found to be in reasonable agreement with room-temperature experimental data.

  20. Measurement of piezoelectric constants of lanthanum-gallium tantalate crystal by X-ray diffraction methods

    SciTech Connect

    Blagov, A. E.; Marchenkov, N. V. Pisarevsky, Yu. V.; Prosekov, P. A.; Kovalchuk, M. V.

    2013-01-15

    A method for measuring piezoelectric constants of crystals of intermediate systems by X-ray quasi-multiple-wave diffraction is proposed and implemented. This technique makes it possible to determine the piezoelectric coefficient by measuring variations in the lattice parameter under an external electric field. This method has been approved, its potential is evaluated, and a comparison with high-resolution X-ray diffraction data is performed.

  1. Development of Polymeric Films with Piezoelectrical Properties from Polypeptides; Low, Odd Nylons; or Polyureas.

    DTIC Science & Technology

    1987-09-01

    PIEZOELECTRICAL PROPERTIES FROM POLYPETIDES; LOW, ODD NYLONS; OR POLYUREAS James P. English -LEC"r David P. Vanderbilt Gerald W. McNeely FEBo0 8 SOUTHERN...Nylons; or Polyureas English, James P.; Vanderbilt, David P.; McNeely, Gerald W. 13a. TYPE OF REPORT 13b TIME COVERED 14. DATE OF REPORT (Year, Month...reverSe if necessary and identify by block number) FIELD GROUP SUB-GROUP ,Piezoelectricity, polyamides, polypeptides, poly (amino acids), polyureas , nylon

  2. Attosecond x-ray source generation from two-color polarized gating plasmonic field enhancement

    SciTech Connect

    Feng, Liqiang; Yuan, Minghu; Chu, Tianshu

    2013-12-15

    The plasmonic field enhancement from the vicinity of metallic nanostructures as well as the polarization gating technique has been utilized to the generation of the high order harmonic and the single attosecond x-ray source. Through numerical solution of the time-dependent Schrödinger equation, for moderate the inhomogeneity and the polarized angle of the two fields, we find that not only the harmonic plateau has been extended and enhanced but also the single short quantum path has been selected to contribute to the harmonic. As a result, a series of 50 as pulses around the extreme ultraviolet and the x-ray regions have been obtained. Furthermore, by investigating the other parameters effects on the harmonic emission, we find that this two-color polarized gating plasmonic field enhancement scheme can also be achieved by the multi-cycle pulses, which is much better for experimental realization.

  3. Graphene enhanced evanescent field in microfiber multimode interferometer for highly sensitive gas sensing.

    PubMed

    Yao, B C; Wu, Y; Zhang, A Q; Rao, Y J; Wang, Z G; Cheng, Y; Gong, Y; Zhang, W L; Chen, Y F; Chiang, K S

    2014-11-17

    Graphene based new physics phenomena are leading to a variety of stimulating graphene-based photonic devices. In this study, the enhancement of surface evanescent field by graphene cylindrical cladding is observed, for the first time, by using a graphene-coated microfiber multi-mode interferometer (GMMI). It is found theoretically and experimentally that the light transmitting in the fiber core is efficiently dragged by the graphene, hence significantly enhancing the evanescent fields, and subsequently improving the sensitivity of the hybrid waveguide. The experimental results for gas sensing verified the theoretical prediction, and ultra-high sensitivities of ~0.1 ppm for NH(3) gas detection and ~0.2 ppm for H(2)O vapor detection are achieved, which could be used for trace analysis. The enhancement of surface evanescent field induced by graphene may pave a new way for developing novel graphene-based all-fiber devices with compactness, low cost, and temperature immunity.

  4. Enhancement and inversion of an alternating-current electric field in a finely dispersed dielectric

    NASA Astrophysics Data System (ADS)

    Kharlamov, V. F.

    2017-01-01

    It has been found that a sinusoidal electric field is enhanced by a factor of more than 103 in two plane-parallel layers of different dielectrics placed between plates of a parallel-plate capacitor. The implementation of the enhancement of the electric field requires that the following two conditions should be satisfied: (1) one of the two layers should consist of finely dispersed dielectric particles with ionized donor centers formed on their surface and free electrons in their bulk, and (2) the dielectric permittivity of the powder should have a negative value. It has also been found that, in the powder layer, the enhancement of the electric field occurs simultaneously with its inversion.

  5. Enhanced Membrane Treatment for Hollow-Fiber Microfiltration in Ultrasonic Reflection Field

    NASA Astrophysics Data System (ADS)

    Kobayashi, Takaomi; Hosaka, Yoho

    2003-05-01

    The effect of ultrasound on the enhanced membrane treatment process was controlled by the reflection of 28 kHz ultrasound onto the vicinity of a hollow-fiber microfiltration membrane. When a stainless reflection plate was placed behind the membrane module, the resultant permeation flux of the membrane was changed in the ultrasonic reflection field. We found that a semicylindrical reflection plate could highly enhance the membrane cleaning process.

  6. Water-processed carbon nanotube/graphene hybrids with enhanced field emission properties

    SciTech Connect

    Song, Meng; Xu, Peng; Wang, Xu; Wu, Huizhen; Wang, Miao E-mail: miaowang@css.zju.edu.cn; Song, Yenan; Li, Zhenhua; Zhao, Pei E-mail: miaowang@css.zju.edu.cn; Shang, Xuefu

    2015-09-15

    Integrating carbon nanotubes (CNTs) and graphene into hybrid structures provides a novel approach to three dimensional (3D) materials with advantageous properties. Here we present a water-processing method to create integrated CNT/graphene hybrids and test their field emission properties. With an optimized mass ratio of CNTs to graphene, the hybrid shows a significantly enhanced field emission performance, such as turn-on electric field of 0.79 V/μm, threshold electric field of 1.05 V/μm, maximum current density of 0.1 mA/cm{sup 2}, and field enhancement factor of ∼1.3 × 10{sup 4}. The optimized mass ratio for field emission emphasizes the importance of both CNTs and graphene in the hybrid. We also hypothesize a possible mechanism for this enhanced field emission performance from the CNT/graphene hybrid. During the solution treatment, graphene oxide behaves as surfactant sheets for CNTs to form a well dispersed solution, which leads to a better organized 3D structure with more conducting channels for electron transport.

  7. A finite crack with arbitrarily varied surface piezoelectricity

    NASA Astrophysics Data System (ADS)

    Xu, Yang; Wang, Xu

    2017-01-01

    We study the contribution of arbitrarily varied surface piezoelectricity to the anti-plane deformation and in-plane electric fields of a hexagonal piezoelectric material containing a finite crack. The varied surface piezoelectricity is incorporated by using an extended version of the continuum-based surface/interface model of Gurtin and Murdoch. In our discussion, the surface properties, including the surface elastic stiffness, the surface piezoelectric modulus and the surface dielectric permittivity, are assumed to be varied arbitrarily along the crack surfaces. By using the Green’s function method, the original boundary value problem is reduced to a system of two coupled first-order Cauchy singular integro-differential equations. Through a diagonalization strategy, the coupled system is transformed into two independent singular integro-differential equations, each of which can be numerically solved by using the collocation method. Our results indicate that the variation of the surface electroelastic moduli exerts a significant influence on the crack opening displacement, the electric potential jump across the crack faces and on the strengths of the logarithmic singularity in stresses and electric displacements at the crack tips.

  8. Vibration control for precision manufacturing using piezoelectric actuators

    SciTech Connect

    Martinez, D.R.; Hinnerichs, T.D.; Redmond, J.M.

    1995-12-31

    Piezoelectric actuators provide high frequency, force, and stiffness capabilities along with reasonable Stroke limits, all of which can be used to increase performance levels in precision manufacturing systems. This paper describes two examples of embedding piezoelectric actuators in structural components for vibration control. One example involves suppressing the self excited chatter phenomenon in the metal cutting process of a milling machine and the other involves damping vibrations induced by rigid body stepping of a photolithography platen. Finite element modeling and analyses are essential for locating and sizing the actuators and permit further simulation studies of the response of the dynamic system. Experimental results are given for embedding piezoelectric actuators in a cantilevered bar configuration, which was used as a surrogate machine tool structure. These results are incorporated into a previously developed milling process simulation and the effect of the control on the cutting process stability diagram is quantified. Experimental results are also given for embedding three piezoelectric actuators in a surrogate photolithography platen to suppress vibrations. These results demonstrate the potential benefit that can be realized by applying advances from the field of adaptive structures to problems in precision manufacturing.

  9. Piezoelectric Size Effects in a Zinc Oxide Micropillar.

    PubMed

    Li, Tao; Li, Yu Tong; Qin, Wei Wei; Zhang, Ping Ping; Chen, Xiao Qiang; Hu, Xue Feng; Zhang, Wei

    2015-12-01

    In this work, the dependence of piezoelectric coefficients (PE) on the size of artificial fabricated ZnO micropillars on Si substrate is investigated. ZnO full film is grown with c-axis orientation and an average grain size of 20 nm at a substrate temperature of 500 °C by pulsed laser ablation. The micropillars with the size range of 1.5 to 7 μm are formed by top-down semiconductor device processing. The PE, characterized by piezoelectric force microscopy (PFM), is found to increase from 18.2 to 46.9 pm/V, when the ZnO pillar size is reduced from 7 to 1.5 μm. The strong PE dependence on ZnO pillar size can be explained by local changes in polarization and reduction of unit cell volume with respect to bulk values. These results have strong implications in the field of energy harvesting, as piezoelectric voltage output scales with the piezoelectric coefficient.

  10. Means and method for nonuniform poling of piezoelectric transducers

    DOEpatents

    Hsu, D.K.; Margetan, F.J.; Hasselbusch, M.D.; Wormley, S.J.; Hughes, M.S.; Thompson, D.O.

    1990-10-09

    An apparatus and method are disclosed for nonuniform poling of piezoelectric transducers includes machining one or more indentation into an end of a piezoelectric rod and cutting the rod to present a thickened disk shape. Highly electrically conductive material is deposited on at least the indentations in the one end and on at least portions of the opposite face of the member. One or more electrodes are configured to matingly fit within the indentations on the one face of the disk, with a like number of electrodes being positionable on the opposite face of the material. Electrical power is then applied to the electrodes in desired amounts, polarity, and duration. The indentations vary the electrical field produced within the piezoelectric material to produce nonuniform poling in the material. The thick disk is then cut to remove the indentations and to present a thin, flat two sided disk for installation in a conventional piezoelectric transducer probe. The indentations are selected to produce poling in accordance with desired transducer response profiles such as Gaussian or Bessel functions. 14 figs.

  11. Means and method for nonuniform poling of piezoelectric transducers

    DOEpatents

    Hsu, David K.; Margetan, Frank J.; Hasselbusch, Michael D.; Wormley, Samuel J.; Hughes, Michael S.; Thompson, Donald O.

    1990-10-09

    An apparatus and method for nonuniform poling of piezoelectric transducers includes machining one or more indentation into an end of a piezoelectric rod and cutting the rod to present a thickened disk shape. Highly electrically conductive material is deposited on at least the indentations in the one end and on at least portions of the opposite face of the member. One or more electrodes are configured to matingly fit within the indentations on the one face of the disk, with a like number of electrodes being positionable on the opposite face of the material. Electrical power is then applied to the electrodes in desired amounts, polarity, and duration. The indentations vary the electrical field produced within the piezoelectric material to produce nonuniform poling in the material. The thick disk is then cut to remove the indentations and to present a thin, flat two sided disk for installation in a conventional piezoelectric transducer probe. The indentations are selected to produce poling in accordance with desired transducer response profiles such as Gaussian or Bessel functions.

  12. Capacitance-Based Frequency Adjustment of Micro Piezoelectric Vibration Generator

    PubMed Central

    Mao, Xinhua; He, Qing; Li, Hong; Chu, Dongliang

    2014-01-01

    Micro piezoelectric vibration generator has a wide application in the field of microelectronics. Its natural frequency is unchanged after being manufactured. However, resonance cannot occur when the natural frequencies of a piezoelectric generator and the source of vibration frequency are not consistent. Output voltage of the piezoelectric generator will sharply decline. It cannot normally supply power for electronic devices. In order to make the natural frequency of the generator approach the frequency of vibration source, the capacitance FM technology is adopted in this paper. Different capacitance FM schemes are designed by different locations of the adjustment layer. The corresponding capacitance FM models have been established. Characteristic and effect of the capacitance FM have been simulated by the FM model. Experimental results show that the natural frequency of the generator could vary from 46.5 Hz to 42.4 Hz when the bypass capacitance value increases from 0 nF to 30 nF. The natural frequency of a piezoelectric vibration generator could be continuously adjusted by this method. PMID:25133237

  13. Capacitance-based frequency adjustment of micro piezoelectric vibration generator.

    PubMed

    Mao, Xinhua; He, Qing; Li, Hong; Chu, Dongliang

    2014-01-01

    Micro piezoelectric vibration generator has a wide application in the field of microelectronics. Its natural frequency is unchanged after being manufactured. However, resonance cannot occur when the natural frequencies of a piezoelectric generator and the source of vibration frequency are not consistent. Output voltage of the piezoelectric generator will sharply decline. It cannot normally supply power for electronic devices. In order to make the natural frequency of the generator approach the frequency of vibration source, the capacitance FM technology is adopted in this paper. Different capacitance FM schemes are designed by different locations of the adjustment layer. The corresponding capacitance FM models have been established. Characteristic and effect of the capacitance FM have been simulated by the FM model. Experimental results show that the natural frequency of the generator could vary from 46.5 Hz to 42.4 Hz when the bypass capacitance value increases from 0 nF to 30 nF. The natural frequency of a piezoelectric vibration generator could be continuously adjusted by this method.

  14. Modified field enhancement and extinction by plasmonic nanowire dimers due to nonlocal response.

    PubMed

    Toscano, Giuseppe; Raza, Søren; Jauho, Antti-Pekka; Mortensen, N Asger; Wubs, Martijn

    2012-02-13

    We study the effect of nonlocal optical response on the optical properties of metallic nanowires, by numerically implementing the hydrodynamical Drude model for arbitrary nanowire geometries. We first demonstrate the accuracy of our frequency-domain finite-element implementation by benchmarking it in a wide frequency range against analytical results for the extinction cross section of a cylindrical plasmonic nanowire. Our main results concern more complex geometries, namely cylindrical and bow-tie nanowire dimers that can strongly enhance optical fields. For both types of dimers we find that nonlocal response can strongly affect both the field enhancement in between the dimers and their respective extinction cross sections. In particular, we give examples of blueshifted maximal field enhancements near hybridized plasmonic dimer resonances that are still large but nearly two times smaller than in the usual local-response description. For the same geometry at a fixed frequency, the field enhancement and cross section can also be significantly more enhanced in the nonlocal-response model.

  15. All-dielectric nanostructures for low-loss field enhanced spectroscopy and imaging (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Yano, Taka-aki; Tsuchimoto, Yuta; Hayashi, Tomohiro; Hara, Masahiko

    2016-09-01

    Dielectric nanostructures with high refractive index and low optical loss have attracted considerable attention as an alternative to plasmonic nanostructures. We experimentally demonstrated to control the visible electromagnetic resonances of Si-based core-shell nanostructures by thermally varying the core-shell ratio. We also found a Fano resonance which was generated by the interference between the electric and magnetic dipole moments excited in the core-shell nanostructures. The all-dielectric nanostructures realized low energy loss and high electromagnetic field enhancement comparable with that exhibited by plasmonic nanostructures. These unique optical properties would enable us to demonstrate effective field-enhanced spectroscopy and imaging with low heat generation.

  16. Near-field enhanced ultraviolet resonance Raman spectroscopy using aluminum bow-tie nano-antenna

    PubMed Central

    Li, Ling; Fang Lim, Shuang; Puretzky, Alexander A.; Riehn, Robert; Hallen, H. D.

    2012-01-01

    An aluminum bow-tie nano-antenna is combined with the resonance Raman effect in the deep ultraviolet to dramatically increase the sensitivity of Raman spectra to a small volume of material, such as benzene used here. We further demonstrate gradient-field Raman peaks for several strong infrared modes. We achieve a gain of ∼105 in signal intensity from the near field enhancement due to the surface plasmon resonance in the aluminum nanostructure. The on-line resonance enhancement contributes another factor of several thousands, limited by the laser line width. Thus, an overall gain of hundreds of million is achieved. PMID:23066168

  17. A photonic-crystal optical antenna for extremely large local-field enhancement.

    PubMed

    Chang, Hyun-Joo; Kim, Se-Heon; Lee, Yong-Hee; Kartalov, Emil P; Scherer, Axel

    2010-11-08

    We propose a novel design of an all-dielectric optical antenna based on photonic-band-gap confinement. Specifically, we have engineered the photonic-crystal dipole mode to have broad spectral response (Q~70) and well-directed vertical-radiation by introducing a plane mirror below the cavity. Considerably large local electric-field intensity enhancement~4,500 is expected from the proposed design for a normally incident planewave. Furthermore, an analytic model developed based on coupled-mode theory predicts that the electric-field intensity enhancement can easily be over 100,000 by employing reasonably high-Q (~10,000) resonators.

  18. Enhancing the tumor discrimination using antibody-activated magnetic nanoparticles in ultra-low magnetic fields

    NASA Astrophysics Data System (ADS)

    Yang, H. C.; Huang, K. W.; Liao, S. H.; Horng, H. E.; Chieh, J. J.; Chen, H. H.; Chen, M. J.; Chen, K. L.; Wang, L. M.

    2013-01-01

    In this paper, we report an enhanced liver tumor discrimination for rats using antibody-activated magnetic nanoparticles (MNs) and ultra-low-field magnetic resonance imaging ex vivo. It was found that the intensity ratio between the magnetic resonance image of tumor and normal liver tissues is 2-3 absence of antibody-activated MNs in rats. The intensity ratio rises to ˜100 when antibody-activated MNs are expressed in liver tumors through vein injection. Enhancing tumor discrimination using antibody-activated MNs is demonstrated using T1-weighted contrast imaging in ultra-low magnetic fields.

  19. Controlling the electric field enhancement factor of photonic nanojets by using the magneto-optical effect

    NASA Astrophysics Data System (ADS)

    Khaleque, Abdul; Li, Ziyuan; Hattori, Haroldo T.

    2013-12-01

    In recent years, many researchers have studied photonic nanojets. These nanojets are created when an incident plane wave is focused into a narrow and high intensity emerging optical beam leaving a micro-object (e.g. microcylinder). These narrow beams may find applications in particle imaging and detection, optical sensors, enhanced Raman scattering, and particle manipulation. They also allow the projection of a particle to the far-field where it can be easily visualized. In this paper, it is shown that the electric field enhancement factor can be dynamically controlled by the application of an external intense magnetic flux density.

  20. Note: High-efficiency energy harvester using double-clamped piezoelectric beams

    SciTech Connect

    Zheng, Yingmei; Wu, Xuan; Parmar, Mitesh; Lee, Dong-weon

    2014-02-15

    In this study, an improvement in energy conversion efficiency has been reported, which is realized by using a double-clamped piezoelectric beam, based on uniaxial stretching strain. The buckling mechanism is applied to maximize axial stress in the double-clamped beam. The voltage generated by using the double-clamped piezoelectric beam is higher than that generated by using other conventional structures, such as bending cantilevers coated/sandwiched with piezoelectric film, which is proven both theoretically and experimentally. The power generation efficiency is enhanced by further optimizing the double-clamped structure. The optimized high-efficiency energy harvester utilizing double-clamped piezoelectric beams generates a peak output power of 80 μW, under an acceleration of 0.1g.

  1. Note: high-efficiency energy harvester using double-clamped piezoelectric beams.

    PubMed

    Zheng, Yingmei; Wu, Xuan; Parmar, Mitesh; Lee, Dong-weon

    2014-02-01

    In this study, an improvement in energy conversion efficiency has been reported, which is realized by using a double-clamped piezoelectric beam, based on uniaxial stretching strain. The buckling mechanism is applied to maximize axial stress in the double-clamped beam. The voltage generated by using the double-clamped piezoelectric beam is higher than that generated by using other conventional structures, such as bending cantilevers coated/sandwiched with piezoelectric film, which is proven both theoretically and experimentally. The power generation efficiency is enhanced by further optimizing the double-clamped structure. The optimized high-efficiency energy harvester utilizing double-clamped piezoelectric beams generates a peak output power of 80 μW, under an acceleration of 0.1g.

  2. Note: High-efficiency energy harvester using double-clamped piezoelectric beams

    NASA Astrophysics Data System (ADS)

    Zheng, Yingmei; Wu, Xuan; Parmar, Mitesh; Lee, Dong-weon

    2014-02-01

    In this study, an improvement in energy conversion efficiency has been reported, which is realized by using a double-clamped piezoelectric beam, based on uniaxial stretching strain. The buckling mechanism is applied to maximize axial stress in the double-clamped beam. The voltage generated by using the double-clamped piezoelectric beam is higher than that generated by using other conventional structures, such as bending cantilevers coated/sandwiched with piezoelectric film, which is proven both theoretically and experimentally. The power generation efficiency is enhanced by further optimizing the double-clamped structure. The optimized high-efficiency energy harvester utilizing double-clamped piezoelectric beams generates a peak output power of 80 μW, under an acceleration of 0.1g.

  3. Virus-based piezoelectric energy generation.

    PubMed

    Lee, Byung Yang; Zhang, Jinxing; Zueger, Chris; Chung, Woo-Jae; Yoo, So Young; Wang, Eddie; Meyer, Joel; Ramesh, Ramamoorthy; Lee, Seung-Wuk

    2012-05-13

    Piezoelectric materials can convert mechanical energy into electrical energy, and piezoelectric devices made of a variety of inorganic materials and organic polymers have been demonstrated. However, synthesizing such materials often requires toxic starting compounds, harsh conditions and/or complex procedures. Previously, it was shown that hierarchically organized natural materials such as bones, collagen fibrils and peptide nanotubes can display piezoelectric properties. Here, we demonstrate that the piezoelectric and liquid-crystalline properties of M13 bacteriophage (phage) can be used to generate electrical energy. Using piezoresponse force microscopy, we characterize the structure-dependent piezoelectric properties of the phage at the molecular level. We then show that self-assembled thin films of phage can exhibit piezoelectric strengths of up to 7.8 pm V(-1). We also demonstrate that it is possible to modulate the dipole strength of the phage, hence tuning the piezoelectric response, by genetically engineering the major coat proteins of the phage. Finally, we develop a phage-based piezoelectric generator that produces up to 6 nA of current and 400 mV of potential and use it to operate a liquid-crystal display. Because biotechnology techniques enable large-scale production of genetically modified phages, phage-based piezoelectric materials potentially offer a simple and environmentally friendly approach to piezoelectric energy generation.

  4. Virus-based piezoelectric energy generation

    NASA Astrophysics Data System (ADS)

    Lee, Byung Yang; Zhang, Jinxing; Zueger, Chris; Chung, Woo-Jae; Yoo, So Young; Wang, Eddie; Meyer, Joel; Ramesh, Ramamoorthy; Lee, Seung-Wuk

    2012-06-01

    Piezoelectric materials can convert mechanical energy into electrical energy, and piezoelectric devices made of a variety of inorganic materials and organic polymers have been demonstrated. However, synthesizing such materials often requires toxic starting compounds, harsh conditions and/or complex procedures. Previously, it was shown that hierarchically organized natural materials such as bones, collagen fibrils and peptide nanotubes can display piezoelectric properties. Here, we demonstrate that the piezoelectric and liquid-crystalline properties of M13 bacteriophage (phage) can be used to generate electrical energy. Using piezoresponse force microscopy, we characterize the structure-dependent piezoelectric properties of the phage at the molecular level. We then show that self-assembled thin films of phage can exhibit piezoelectric strengths of up to 7.8 pm V-1. We also demonstrate that it is possible to modulate the dipole strength of the phage, hence tuning the piezoelectric response, by genetically engineering the major coat proteins of the phage. Finally, we develop a phage-based piezoelectric generator that produces up to 6 nA of current and 400 mV of potential and use it to operate a liquid-crystal display. Because biotechnology techniques enable large-scale production of genetically modified phages, phage-based piezoelectric materials potentially offer a simple and environmentally friendly approach to piezoelectric energy generation.

  5. Field enhancement factors and self-focus functions manifesting in field emission resonances in scanning tunneling microscopy.

    PubMed

    Su, Wei-Bin; Lin, Chun-Liang; Chan, Wen-Yuan; Lu, Shin-Ming; Chang, Chia-Seng

    2016-04-29

    Field emission (FE) resonance (or Gundlach oscillation) in scanning tunneling microscopy (STM) is a phenomenon in which the FE electrons emitted from the microscope tip couple into the quantized standing-wave states within the STM tunneling gap. Although the occurrence of FE resonance peaks can be semi-quantitatively described using the triangular potential well model, it cannot explain the experimental observation that the number of resonance peaks may change under the same emission current. This study demonstrates that the aforementioned variation can be adequately explained by introducing a field enhancement factor that is related to the local electric field at the tip apex. The peak number of FE resonances increases with the field enhancement factor. The peak intensity of the FE resonance on the reconstructed Au(111) surface varies in the face-center cubic, hexagonal-close-packed, and ridge regions, thus providing the contrast in the mapping through FE resonances. The mapping contrast is demonstrated to be nearly independent of the tip-sample distance, implying that the FE electron beam is not divergent because of a self-focus function intrinsically involved in the STM configuration.

  6. Local field enhanced second-harmonic response of organic nanofibers deposited on encapsulated plasmonic substrates

    NASA Astrophysics Data System (ADS)

    Kostiučenko, Oksana; Leißner, Till; Brewer, Jonathan R.; Tamulevičius, Tomas; Tamulevičius, Sigitas; Fiutowski, Jacek; Rubahn, Horst-Günter

    2015-08-01

    In this work, enhancement of the second harmonic response of organic nanofibers deposited on encapsulated and robust plasmonic active substrate is experimentally demonstrated. Organic nanofibers grown from functionalized paraquaterphenylene (CNHP4) molecules have been transferred on lithographically defined regular arrays of gold nanostructures, which subsequently have been coated with thin films of diamond-like carbon with 25, 55 and 100 nm thickness. Femtosecond laser scanning microscopy enables us to identify enhancement of the second harmonic response of the fibers. This is facilitated by a preservation of the field enhancement effects, which appear on the nanostructures and remain significant on top of the coating layer.

  7. Surfactant-like compounds enhance the bioavailability of organic contaminants: Treatability results for a field demonstration

    SciTech Connect

    Gillespie, M.T.; Strong-Gunderson, J.M.; Palumbo, A.V.

    1995-12-31

    Methods to enhance rates of trichloroethylene (TCE) biodegradation were investigated during laboratory treatability studies in support of a field demonstration. Several commercially available nutrients with surfactant-like properties were assayed for their effect on enhancing TCE bioavailability and rates of degradation in soils with high clay content. The bacteria assayed were Methylosinus trichosporium OB3b (a methanotroph) and a heterotrophic consortium isolated from TCE saturated water. Several surfactants were added to 1 gram of site soil with the bacteria. Laboratory results showed that samples containing even low concentrations of surfactant compounds exhibited increased TCE partitionining into the liquid phase from the headspace, which correlated with an enhanced degradation rate.

  8. Finite Element Method Simulations of the Near-Field Enhancement at the Vicinity of Fractal Rough Metallic Surfaces

    SciTech Connect

    Micic, Miodrag; Klymyshyn, Nicholas A.; Lu, H PETER.

    2004-03-04

    Near-field optical enhancement at metal surfaces and methods such as surface plasmon resonance (SPR), surface-enhanced Raman scattering (SERS), fluorescent quenching and enhancement, and various near-field scanning microscopies (NSOM) all depend on a metals surface properties, mainly on its morphology and SPR resonant frequency. We report on simulations of the influence of different surface morphologies on electromagnetic field enhancements at the rough surfaces of noble metals and also evaluate the optimal conditions for the generation of a surface-enhanced Raman signal of absorbed species on a metallic substrate. All simulations were performed with a classical electrodynamics approach using the full set of Maxwells equations, which were solved with the three-dimensional finite element method (FEM). Two different classes of surfaces where modeled using fractals, representing diffusion limited aggregation growth dendritic structures, such as one on the surface of electrodes, and second one representing the sponge-like structure used to model surfaces of particles with high porosity, such as metal coated catalyst supports. The simulations depict the high inhomogeneity of an enhanced electromagnetic field as both a field enhancement and field attenuation near the surface. While the diffusion limited aggregation dendritical fractals enhanced the near-field electromagnetic field, the sponge fractals significantly reduced the local electromagnetic field intensity. Moreover, the fractal orders of the fractal objects did not significantly alter the total enhancement, and the distribution of a near-field enhancement was essentially invariant to the changes in the angle of an incoming laser beam.

  9. Field Effect Enhanced Hydrogen Evolution Reaction of MoS2 Nanosheets.

    PubMed

    Wang, Junhui; Yan, Mengyu; Zhao, Kangning; Liao, Xiaobin; Wang, Peiyao; Pan, Xuelei; Yang, Wei; Mai, Liqiang

    2017-02-01

    Hydrogen evolution reaction performance of MoS2 can be enhanced through electric-field-facilitated electron transport. The best catalytic performance of a MoS2 nanosheet can achieve an overpotential of 38 mV (100 mA cm(-2) ) at gate voltage of 5 V, the strategy of utilizing the electric field can be used in other semiconductor materials to improve their electrochemical catalysis for future relevant research.

  10. Depth enhancement of multi-layer light field display using polarization dependent internal reflection.

    PubMed

    Jo, Na-Young; Lim, Hong-Gi; Lee, Sung-Keun; Kim, Yong-Soo; Park, Jae-Hyeung

    2013-12-02

    A technique to enhance the depth range of the multi-layer light field three-dimensional display is proposed. A set of the optical plates are stacked in front of the conventional multi-layer light field display, creating additional internal reflection for one polarization state. By switching between two orthogonal polarization states in synchronization with the displayed three-dimensional images, the depth range of the display can be doubled. The proposed method is verified experimentally, confirming its feasibility.

  11. Numerical MLPG Analysis of Piezoelectric Sensor in Structures

    NASA Astrophysics Data System (ADS)

    Staňák, Peter; Sládek, Ján; Sládek, Vladimír; Krahulec, Slavomír

    2014-07-01

    The paper deals with a numerical analysis of the electro-mechanical response of piezoelectric sensors subjected to an external non-uniform displacement field. The meshless method based on the local Petrov-Galerkin (MLPG) approach is utilized for the numerical solution of a boundary value problem for the coupled electro-mechanical fields that characterize the piezoelectric material. The sensor is modeled as a 3-D piezoelectric solid. The transient effects are not considered. Using the present MLPG approach, the assumed solid of the cylindrical shape is discretized with nodal points only, and a small spherical subdomain is introduced around each nodal point. Local integral equations constructed from the weak form of governing PDEs are defined over these local subdomains. A moving least-squares (MLS) approximation scheme is used to approximate the spatial variations of the unknown field variables, and the Heaviside unit step function is used as a test function. The electric field induced on the sensor is studied in a numerical example for two loading scenarios.

  12. Fiber-optic raster scanning two-photon endomicroscope using a tubular piezoelectric actuator

    NASA Astrophysics Data System (ADS)

    Do, Dukho; Yoo, Hongki; Gweon, Dae-Gab

    2014-06-01

    A nonresonant, fiber-optic raster scanning endomicroscope was developed using a quarter-tubular piezoelectric (PZT) actuator. A fiber lever mechanism was utilized to enhance the small actuation range of the tubular PZT actuator and to increase its field-of-view. Finite element method simulation of the endoscopic probe was conducted for various conditions to maximize its scanning range. After fabricating the probe using a double clad fiber, we obtained two-photon fluorescence images using raster beam scanning of the fiber. The outer diameter of the probe was 3.5 mm and its rigid distal length was 30 mm including a high numerical aperture gradient index lens. These features are sufficient for input into the instrumental channel of a commercial colonoscope or gastroscope to obtain high resolution images in vivo.

  13. Pulsed Direct Current Electric Fields Enhance Osteogenesis in Adipose-Derived Stromal Cells

    PubMed Central

    Hammerick, Kyle E.; James, Aaron W.; Huang, Zubin; Prinz, Fritz B.

    2010-01-01

    Adipose-derived stromal cells (ASCs) constitute a promising source of cells for regenerative medicine applications. Previous studies of osteogenic potential in ASCs have focused on chemicals, growth factors, and mechanical stimuli. Citing the demonstrated role electric fields play in enhancing healing in bone fractures and defects, we investigated the ability of pulsed direct current electric fields to drive osteogenic differentiation in mouse ASCs. Employing 50 Hz direct current electric fields in concert with and without osteogenic factors, we demonstrated increased early osteoblast-specific markers. We were also able to establish that commonly reported artifacts of electric field stimulation are not the primary mediators of the observed effects. The electric fields caused marked changes in the cytoskeleton. We used atomic force microscopy–based force spectroscopy to record an increase in the cytoskeletal tension after treatment with electric fields. We abolished the increased cytoskeletal stresses with the rho-associated protein kinase inhibitor, Y27632, and did not see any decrease in osteogenic gene expression, suggesting that the pro-osteogenic effects of the electric fields are not transduced via cytoskeletal tension. Electric fields may show promise as candidate enhancers of osteogenesis of ASCs and may be incorporated into cell-based strategies for skeletal regeneration. PMID:19824802

  14. Pulsed direct current electric fields enhance osteogenesis in adipose-derived stromal cells.

    PubMed

    Hammerick, Kyle E; James, Aaron W; Huang, Zubin; Prinz, Fritz B; Longaker, Michael T

    2010-03-01

    Adipose-derived stromal cells (ASCs) constitute a promising source of cells for regenerative medicine applications. Previous studies of osteogenic potential in ASCs have focused on chemicals, growth factors, and mechanical stimuli. Citing the demonstrated role electric fields play in enhancing healing in bone fractures and defects, we investigated the ability of pulsed direct current electric fields to drive osteogenic differentiation in mouse ASCs. Employing 50 Hz direct current electric fields in concert with and without osteogenic factors, we demonstrated increased early osteoblast-specific markers. We were also able to establish that commonly reported artifacts of electric field stimulation are not the primary mediators of the observed effects. The electric fields caused marked changes in the cytoskeleton. We used atomic force microscopy-based force spectroscopy to record an increase in the cytoskeletal tension after treatment with electric fields. We abolished the increased cytoskeletal stresses with the rho-associated protein kinase inhibitor, Y27632, and did not see any decrease in osteogenic gene expression, suggesting that the pro-osteogenic effects of the electric fields are not transduced via cytoskeletal tension. Electric fields may show promise as candidate enhancers of osteogenesis of ASCs and may be incorporated into cell-based strategies for skeletal regeneration.

  15. Piezoelectric control of structures prone to instabilities

    NASA Astrophysics Data System (ADS)

    Kim, Sunjung

    vibration, viz. local and overall modes and by a classification of the local modes into two distinct categories, viz., symmetric and anti-symmetric modes respectively. The symmetric local modes interact with overall modes from the outset, i.e. in the linear flutter problem whereas both the sets of local modes interact with overall modes in the post-critical range via cubic terms in the elastic potential. However the effects of interaction in the flutter problem are far less dramatic in comparison to the interactive buckling problem unless the overall modes are activated, say by dynamic pressure on the plate. Control of the panel is exercised by piezo-electric patches placed on the plate at regions of maximum curvature as well as on the stiffener. Two types of control strategies were investigated for the panel subject to fluttering instability. The first is the direct negative velocity feedback control using a single gain factor for each of the sets of plate patches and stiffener patches respectively. A systematic method of determining the gains for the patches has been developed. This is based on the application of LQR algorithm in conjunction with a linearized stiffness matrix of the uncontrolled structure computed at a set of pre-selected times. This type of control was successful till the aerodynamic pressure coefficient reaches up to about six times its critical value, where after it simply failed. The second type of control is the multi-input and multi-output full state feedback control. The LQR algorithm and the linearized stiffness matrix are invoked again, but the gain matrix is computed at the beginning of every time step in the analysis and immediately implemented to control the structure. This type of control proved very effective the only limitation stemming from the maximum field strength that can be sustained by the piezo-electric material employed.

  16. Larger-Stroke Piezoelectrically Actuated Microvalve

    NASA Technical Reports Server (NTRS)

    Yang, Eui-Hyeok

    2003-01-01

    sufficient to enable the valve to handle a fluid pressurized up to about 50 psi (approximately equal to 0.35 MPa). The overall dimensions of the unimorph version would be 2 by 2 by 0.5 mm. In this version, an electric field across the piezoelectric film on a diaphragm would cause the film to pull on, and thereby bend, the diaphragm. At an applied potential of 20 V, the actuator in this version would generate a stroke of 10 micrometers and a force of 0.01 N. This force level would be too low to enable handling of fluids at pressures comparable to those of the bimorph version. This version would be useful primarily in microfluidic and nanofluidic applications that involve extremely low differential pressures and in which there are requirements for extreme miniaturization of valves. Examples of such applications include liquid chromatography and sequencing of deoxyribonucleic acid.

  17. Electric poling-assisted additive manufacturing process for PVDF polymer-based piezoelectric device applications

    NASA Astrophysics Data System (ADS)

    Lee, ChaBum; Tarbutton, Joshua A.

    2014-09-01

    This paper presents a new additive manufacturing (AM) process to directly and continuously print piezoelectric devices from polyvinylidene fluoride (PVDF) polymeric filament rods under a strong electric field. This process, called ‘electric poling-assisted additive manufacturing or EPAM, combines AM and electric poling processes and is able to fabricate free-form shape piezoelectric devices continuously. In this process, the PVDF polymer dipoles remain well-aligned and uniform over a large area in a single design, production and fabrication step. During EPAM process, molten PVDF polymer is simultaneously mechanically stresses in-situ by the leading nozzle and electrically poled by applying high electric field under high temperature. The EPAM system was constructed to directly print piezoelectric structures from PVDF polymeric filament while applying high electric field between nozzle tip and printing bed in AM machine. Piezoelectric devices were successfully fabricated using the EPAM process. The crystalline phase transitions that occurred from the process were identified by using the Fourier transform infrared spectroscope. The results indicate that devices printed under a strong electric field become piezoelectric during the EPAM process and that stronger electric fields result in greater piezoelectricity as marked by the electrical response and the formation of sharper peaks at the polar β crystalline wavenumber of the PVDF polymer. Performing this process in the absence of an electric field does not result in dipole alignment of PVDF polymer. The EPAM process is expected to lead to the widespread use of AM to fabricate a variety of piezoelectric PVDF polymer-based devices for sensing, actuation and energy harvesting applications with simple, low cost, single processing and fabrication step.

  18. Numerical analysis of a quasistatic piezoelectric problem with damage*

    NASA Astrophysics Data System (ADS)

    Fernández, José R.; Martínez, Rebeca; Stavroulakis, Georgios E.

    2008-07-01

    The quasistatic evolution of the mechanical state of a piezoelectric body with damage is numerically studied in this paper. Both damage and piezoelectric effects are included into the model. The variational formulation leads to a coupled system composed of two linear variational equations for the displacement field and the electric potential, and a nonlinear parabolic variational equation for the damage field. The existence of a unique weak solution is stated. Then, a fully discrete scheme is introduced by using a finite element method to approximate the spatial variable and an Euler scheme to discretize the time derivatives. Error estimates are derived on the approximate solutions, from which the linear convergence of the algorithm is deduced under suitable regularity conditions. Finally, a two-dimensional example is presented to demonstrate the behaviour of the solution. To cite this article: J.R. Fernández et al., C. R. Mecanique 336 (2008).

  19. Piezoelectric Power Requirements for Active Vibration Control

    NASA Technical Reports Server (NTRS)

    Brennan, Matthew C.; McGowan, Anna-Maria Rivas

    1997-01-01

    This paper presents a method for predicting the power consumption of piezoelectric actuators utilized for active vibration control. Analytical developments and experimental tests show that the maximum power required to control a structure using surface-bonded piezoelectric actuators is independent of the dynamics between the piezoelectric actuator and the host structure. The results demonstrate that for a perfectly-controlled system, the power consumption is a function of the quantity and type of piezoelectric actuators and the voltage and frequency of the control law output signal. Furthermore, as control effectiveness decreases, the power consumption of the piezoelectric actuators decreases. In addition, experimental results revealed a non-linear behavior in the material properties of piezoelectric actuators. The material non- linearity displayed a significant increase in capacitance with an increase in excitation voltage. Tests show that if the non-linearity of the capacitance was accounted for, a conservative estimate of the power can easily be determined.

  20. Coupled improvement between thermoelectric and piezoelectric materials

    NASA Astrophysics Data System (ADS)

    Montgomery, David; Hewitt, Corey; Dun, Chaochao; Carroll, David

    A novel coupling effect in a thermoelectric and piezoelectric meta-structure is discussed. Thermo-piezoelectric generators (TPEGs) exhibit a synergistic effect that amplifies output voltage, and has been observed to increase piezoelectric voltages over 500% of initial values a time dependent thermoelectric/pyroelectric effect. The resulting improvement in voltage has been observed in carbon nanotubes as well as inorganics such as two-dimensional Bismuth Selenide platelets and Telluride nanorods thin-film thermoelectrics. TPEGs are built by integrating insulating layers of polyvinylidene fluoride (PVDF) piezoelectric films between flexible thin film p-type and n-type thermoelectrics. The physical phenomena arising in the interaction between thermoelectric and piezoelectrics is discussed and a model is presented to quantify the expected coupling voltage as a function of stress, thermal gradient, and different thermoelectric materials. TPEG are ideal to capture waste heat and vibrational energy while creating larger voltages and minimizing space when compared with similar thermoelectric or piezoelectric generators.

  1. SERDP AND NRMRL SPONSOR FIELD TEST OF COSOLVENT-ENHANCED DNAPL REMOVAL

    EPA Science Inventory

    A field test of multicomponent cosolvent flooding for in-situ remediation of DNAPL source zones was conducted at the Dover National Test Site (DNTS) at Dover Air Force Base, Delaware, in July, 2001. The test was part of an Enhanced Source Removal (ESR) demonstration project fund...

  2. COMMENT: Comment on 'Model calculation of the scanned field enhancement factor of CNTs'

    NASA Astrophysics Data System (ADS)

    Zhbanov, A. I.; Lee, Yong-Gu; Pogorelov, E. G.; Chang, Yia-Chung

    2010-09-01

    The model proposed by Ahmad and Tripathi (2006 Nanotechnology 17 3798) demonstrates that the field enhancement factor of carbon nanotubes (CNTs) reaches a maximum at a certain length. Here, we show that this behavior should not occur and suggest our correction to this model.

  3. Interband π plasmon of graphene: strong small-size and field-enhancement effects.

    PubMed

    Hu, Jinlian; Zeng, Haibo; Wang, Cong; Li, Zhigang; Kan, Caixia; Liu, Youwen

    2014-11-14

    The interband π plasmon of graphene has energy corresponding to the ultraviolet (UV) wave band, and hence is promising for UV nanophotonics and nanooptoelectronics. However, its special size effect and electric field-enhancement effect have not been well understood. Here, we have investigated the far-field optical extinction and near-field enhancement features of the interband π plasmon in a graphene nanodisk using discrete dipole approximation and finite-difference time-domain methods. Very interestingly, it has been found that the in-plane (transverse mode) optical extinction peak of monolayer graphene firstly significantly red shifts with increasing diameter, but then tends to a saturation value when the diameter is above 20 nm, showing a strong small-size-sensitive effect. Furthermore, the transverse mode optical extinction peak obviously blue shifts with increasing thickness when the thickness is relatively small. Significantly, the corresponding local electric field enhancement factor produced by the plasmon, which can be found to be as large as several tens, firstly increases with the increase of the size and then reaches a maximum value at only several nanometers in size. Such an ultrasmall-size-sensitive plasmon in the UV region endows graphene dots with new promising potential uses in ultrasmall photo-electric devices and nanoantennas, and in UV enhancers.

  4. Evidence for Adsorbate-Enhanced Field Emission from Carbon Nanotube Fibers (Postprint)

    DTIC Science & Technology

    2013-07-31

    microscopy from single wall nanotube ( SWNT ) caps,9 and by current satura- tion measurements10 from adsorbate-covered SWNTs , were consistent with this...assertion. Comparison of the FE electron energy distributions acquired from clean and adsorbate- covered SWNTs led11 to the conclusion that enhancement...Residual Gas Analysis FE Field Emission CNT Carbon Nanotube SWNT Single Wall Nanotube CSA Chlorosulfonic Acid

  5. Conophthorin enhances the electroantennogram and field behavioral response of Xylosandrus germanus (Coleoptera: Curculionidae) to ethanol

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ethanol acts as a long range cue that aids Xylosandrus germanus (Blandford) in locating living, but weakened trees. Conophthorin is associated with a variety of deciduous trees and enhances X. germanus’ attraction to vulnerable trees. Electroantennogram (EAG) and field trapping experiments were cond...

  6. Enhanced Near-Field Heat Flow of a Monolayer Dielectric Island

    NASA Astrophysics Data System (ADS)

    Worbes, Ludwig; Hellmann, David; Kittel, Achim

    2013-03-01

    We have investigated the influence of thin films of a dielectric material on the near-field mediated heat transfer at the fundamental limit of single monolayer islands on a metallic substrate. We present spatially resolved measurements by near-field scanning thermal microscopy showing a distinct enhancement in heat transfer above NaCl islands compared to the bare Au(111) film. Experiments at this subnanometer scale call for a microscopic theory beyond the macroscopic fluctuational electrodynamics used to describe near-field heat transfer today. The method facilitates the possibility of developing designs of nanostructured surfaces with respect to specific requirements in heat transfer down to a single atomic layer.

  7. Shunted piezoelectrics for passive control of turbomachine blading flow-induced vibrations

    NASA Astrophysics Data System (ADS)

    Cross, Charles J.; Fleeter, Sanford

    2002-04-01

    The application of shunted piezoelectric elements to provide passive structural damping is investigated by means of a series of experiments performed in the Purdue Annular Cascade Research Facility. An array of piezoelectric elements is bonded to an airfoil in the stator row. This airfoil is excited in a chordwise bending mode by the wakes generated by an upstream rotor. As the wakes drive the airfoil vibrations, the piezoelectrics experience a strain and in response produce an electric field. Tuned electrical circuits connected to the piezoelectrics as shunts dissipate this electrical energy, with multiple shunting techniques utilized. This electrical energy dissipation and the corresponding reduction in the airfoil mechanical energy result in a reduction in the magnitude of the resonant vibrations.

  8. Heartbeat detection system using piezoelectric transducer

    NASA Astrophysics Data System (ADS)

    Hamonangan, Yosua; Purnamaningsih, Wigajatri

    2017-02-01

    This paper presents a simple piezoelectric based heartbeat detection system. The signal produced by the piezoelectric will undergo signal conditioning and then converted into digital data by Arduino Nano. Using serial communication, the data will be sent to a computer for display and further analysis. The detection of heartbeat is carried out on three locations; wrist, chest, and diaphragm. From the measurement results, it is shown that the system work best when the piezoelectric is placed on wrist.

  9. Vastly enhancing the chemical stability of phosphorene by employing an electric field.

    PubMed

    Gao, Junfeng; Zhang, Gang; Zhang, Yong-Wei

    2017-03-23

    Currently, a major hurdle preventing phosphorene from various electronic applications is its rapid oxidation under ambient conditions. Thus how to enhance its chemical stability by suppressing oxidation becomes an urgent task. Here, we reveal a highly effective procedure to suppress the oxidation of phosphorene by employing a suitable van der Waals (vdW) substrate and a vertical electric field. Our first-principles study shows that the phosphorene-MoSe2 vdW heterostructure is able to reverse the stability of physisorption and chemisorption of molecular O2 on phosphorene. With further application of a vertical electric field of -0.6 V Å(-1), the energy barrier for oxidation is able to further increase to 0.91 eV, leading to a 10(5) times enhancement in its lifetime compared with that without using the procedure at room temperature. Our work presents a viable strategy to vastly enhance the chemical stability of phosphorene in air.

  10. Near field intensity enhancement and localization in noble metal nanoparticle ensembles

    NASA Astrophysics Data System (ADS)

    Nedyalkov, N. N.; Nikov, Ru G.; Atanasov, P. A.

    2013-03-01

    Theoretical analysis on the electromagnetic field properties in vicinity of noble metal nanostructures is presented. The study is done on the basis of numerical simulation using Finite Difference Time Domain approach. The systems under consideration are two- and three-dimensional arrays composed of gold or silver nanoparticles. The near field intensity distribution and its enhancement are calculated for structures with different characteristics - particle size, inter-particle distance, and at different conditions related to the incident irradiation - polarization, and geometry of excitation. This analysis is used for definition of some optimal parameters for such structures from the viewpoint of application in Surface Enhancement Raman Spectroscopy (SERS). It is shown that the manipulation of the geometry of excitation of the nanoparticle system could be used as a crucial parameter for improving the efficiency of the classical configuration in SERS. The predicted influences of the nanoparticle system properties on the Raman signal enhancement are confirmed experimentally.

  11. Circular piezoelectric bender laser tuners

    NASA Technical Reports Server (NTRS)

    Mcelroy, J. H.; Thompson, P. E.; Walker, H. E.; Johnson, E. H.; Radecki, D. J.; Reynolds, R. S.

    1972-01-01

    The circular piezoelectric bender laser tuner to replace conventional laser tuners when mirror diameters up to 0.50 inch are sufficient is described. The circular piezoelectric bender laser tuner offers much higher displacements per applied volt and permits laser control circuits to be fabricated using standard operational amplifiers, rather than the expensive high-voltage amplifiers required by conventional tuners. The cost of the device is more than one order of magnitude lower than conventional tuners and the device is very rugged with all mechanical resonances easily designed to be greater than 3kHz. In addition to its use as a laser frequency tuner, the circular bender tuner should find many applications in interferometers and similar devices.

  12. Piezoelectric Measurement Of Bulk Modulus

    NASA Technical Reports Server (NTRS)

    Butler, Barry L.

    1992-01-01

    In method of measuring bulk modulus of elasticity of elastomeric material, piezoelectric crystals of various sizes and energized by alternating voltage embedded in material. Concept demonstrated in test cell in which piezoelectric crystal mounted either unconstrained or between two rubber pads and connected as actuator in loud-speaker. The 1-in. diameter crystal excited with 24 Vac at 60 Hz. When crystal was unconstrained, it drew current of 0.8 mA. When crystal was constrained between rubber pads, current fell to 0.65 mA. Low current, minimal heating, and absence of arcing makes technique suitable for measurement of bulk moduli of elasticity of flammable or explosive rubbery materials.

  13. Improved Controller for a Three-Axis Piezoelectric Stage

    NASA Technical Reports Server (NTRS)

    Rao, Shanti; Palmer, Dean

    2009-01-01

    An improved closed-loop controller has been built for a three-axis piezoelectric positioning stage. The stage can be any of a number of commercially available or custom-made units that are used for precise three-axis positioning of optics in astronomical instruments and could be used for precise positioning in diverse fields of endeavor that include adaptive optics, fabrication of semiconductors, and nanotechnology.

  14. Subterahertz excitations and magnetoelectric effects in hexaferrite-piezoelectric bilayers

    SciTech Connect

    Ustinov, Alexey B.; Srinivasan, G.

    2008-10-06

    A frequency-agile hexaferrite-piezoelectric composite for potential device applications at subterahertz frequencies is studied. The bilayer is composed of aluminum substituted barium hexagonal ferrite (BaAl{sub 2}Fe{sub 10}O{sub 19}) and lead zirconate titanate (PZT). A dc electric field applied to PZT results in mechanical deformation of the ferrite, leading to a frequency shift in ferromagnetic resonance. The bilayer demonstrates magnetoelectric interaction coefficient of about 0.37 Oe cm/kV.

  15. Enhancement of X-ray Production in Z-Pinch Plasmas Using Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Edison, N. S.; Etlicher, B.; Attelan, S.; Rouillé, C.; Chuvatin, A. S.; Aliaga, R.

    1994-03-01

    We are investigating the effects of an axial magnetic field to stabilize an aluminum vapor z-pinch. An aluminum plasma jet is created from an exploding foil in a DC magnetic field (Bz0 ≤ 300 G). The applied field is small compared to the azimuthal field, Bz0 ≫ Bϑ, and is intended to reduce the growth of instabilities during the compression phase. The pinch is driven by a 2 Ω, 0.1 TW generator (250 kA in 80 ns). Additionally, a micron sized wire may be placed on the pinch axis leading to the plasma-on-wire (POW) configuration. Qualitatively, increasing the axial magnetic field improves the pinch with the m=1 instabilities becoming negligible for fields higher than 150 G. We find that the externally applied fields can enhance x-ray production up to a critical field. Above this critical field x-ray emission decreases even though the pulse length of the radiation may still be increasing. As the applied field increases, the period of x-ray emission increases with the harder spectrum affected the least. The x-ray yield peaks for the POW and Al jet alone configurations at 150 G and 50 G respectively. Diagnostics include filtered PIN x-ray diodes, time-resolved schlieren photography, and time-integrated multiple filtered pinholes. We will present the results comparing the POW and aluminum jet configurations described above.

  16. Neurotrophins enhance electric field-directed growth cone guidance and directed nerve branching.

    PubMed

    McCaig, C D; Sangster, L; Stewart, R

    2000-03-01

    Neurotrophins play major roles in the developing nervous system in controlling neuronal differentiation, neurite outgrowth, guidance and branching, synapse formation and maturation, and neuronal survival or death. There is increasing evidence that nervous system construction takes place in the presence of dc electric fields, which fluctuate dynamically in space and time during embryonic development. These have their origins in the neural tube itself, as well as in surrounding skin and gut. Early disruption of these endogenous electric fields causes failure of the nervous system to form, or else it forms aberrantly. Nerve growth, guidance, and branching are controlled tightly during pathway construction and in vitro dc electric fields have profound effects on each of these behaviours. We have used cultured neurones to ask whether neurotrophins and dc electric fields might interact in shaping neuronal growth, given their coexistence in vivo. Electric field-directed nerve growth generally was enhanced by the simultaneous presentation of several neurotrophins to the growth cone. Under certain circumstances, more nerves turned cathodally, they turned faster, further, and in lower field strengths. Intriguingly, other combinations of dc electric field and neurotrophins (low field strength and neurotrophin 3 (NT-3) switched the direction of growth cone turning. Additionally, cathodally directed nerve growth was faster and directed branching was much more common when electric fields and neurotrophins interacted with neuronal growth cones. Given such profound changes in growth cone behaviour in vitro, neurotrophins and endogenous electric fields are likely to interact in vivo.

  17. A Piezoelectric Cryogenic Heat Switch

    NASA Technical Reports Server (NTRS)

    Jahromi, Amir E.; Sullivan, Dan F.

    2014-01-01

    We have measured the thermal conductance of a mechanical heat switch actuated by a piezoelectric positioner, the PZHS (PieZo electric Heat Switch), at cryogenic temperatures. The thermal conductance of the PZHS was measured between 4 K and 10 K, and on/off conductance ratios greater than 100 were achieved when the positioner applied its maximum force of 8 N. We discuss the advantages of using this system in cryogenic applications, and estimate the ultimate performance of an optimized PZHS.

  18. Elastodynamic Impact into Piezoelectric Media

    DTIC Science & Technology

    2014-09-01

    code, COMSOL Multiphysics. Numerical inverse Laplace transform; modified Dubner-Abate-Crump algorithm; impact boundary condition; FDTD; COMSOL ...code, COMSOL Multiphysics.13 The FDTD code was developed by Raymond A 1 Wildman and the COMSOL simulations were performed by David A Hopkins to compare...jump given by the expression sjump. Figs. 2, 3, and 4 also illustrate solutions to the piezoelectric impact problem using a FDTD method and COMSOL

  19. Enhanced electron field emission from NiCo2O4 nanosheet arrays

    NASA Astrophysics Data System (ADS)

    Naik, Kusha Kumar; Khare, Ruchita T.; Gelamo, Rogerio V.; More, Mahendra A.; Thapa, Ranjit; Late, Dattatray J.; Sekhar Rout, Chandra

    2015-09-01

    Electron emission properties of electrodeposited spinel NiCo2O4 nanosheet arrays grown on Ni foam have been studied. The work function of NiCo2O4 was calculated by density functional theory using the plane-wave basis set and used to estimate the field enhancement factor. The NiCo2O4 nanosheet arrays exhibited a low turn-on field of 1.86 V μm-1 at 1 μA cm-2 and current density of 686 μA cm-2 at 3.2 V μm-1, with field enhancement factor β = 1460 and good field emission current stability. The field emission properties of the NiCo2O4 nanosheet arrays showed enhanced performance compared to chemically prepared NiCo2O4 nanosheets. Hence, the nanosheet arrays have great potential as robust high performance vertical structure electron emitters for future flat panel displays and vacuum electronic device applications.

  20. Enhancing isolation of antenna arrays by simultaneously blocking and guiding magnetic field lines using magnetic metamaterials

    NASA Astrophysics Data System (ADS)

    Liu, Zhaotang; Wang, Jiafu; Qu, Shaobo; Zhang, Jieqiu; Ma, Hua; Xu, Zhuo; Zhang, Anxue

    2016-10-01

    In this article, we propose to enhance the isolation of antenna arrays by manipulating the near-field magnetic coupling between adjacent antennas using magnetic metamaterials (MMs). Due to the artificially designed negative or large permeability, MMs can concentrate or block the magnetic field lines where they are located, which allows us to tune the near-field magnetic coupling strengths between antennas. MMs can play a two-fold role in enhancing antenna isolation. On one hand, the magnetic fields can be blocked in gaps between adjacent antennas using MMs with negative permeability; on the other hand, the magnetic fields can be pulled towards the borders of the antenna array using MMs with large permeability. As an example, we demonstrated a four-element patch antenna array with split-ring resonators (SRR) integrated in the substrate. The measured results show that the isolation can be enhanced by more than 10 dB with the integration of SRRs, even if the gap between antennas is only about 0.082λ. This work provides an effective alternative to the design of high-isolation antenna arrays.

  1. Polarization and Characterization of Piezoelectric Polymers

    NASA Technical Reports Server (NTRS)

    Bodiford, Hollie N.

    1995-01-01

    Piezoelectric materials exhibit an electrical response, such as voltage or charge, in reaction to a mechanical stimuli. The mechanical stimuli can be force, pressure, light, or heat. Therefore, these materials are excellent sensors for various properties. The major disadvantage of state of the art piezoelectric polymers is their lack of utility at elevated temperatures. The objective of this research is to study the feasibility of inducing piezoelectricity in high performance polymer systems. The three aspects of the research include experimental poling, characterization of the capacitance, and demonstration of the use of a piezoelectric polymer as a speaker.

  2. Nanoparticle-on-mirror cavity modes for huge and/or tunable plasmonic field enhancement

    NASA Astrophysics Data System (ADS)

    Huang, Yu; Ma, Lingwei; Li, Jianghao; Zhang, Zhengjun

    2017-03-01

    We present a careful numerical study of nanoparticle (NP) faceting, highlighting the great influence of small morphological changes of NP-mirror cavities on near-field enhancement in the nanoparticle-on-mirror (NPOM) system. Using a 3D finite element method (FEM) plasmon mapping method, the active transverse cavity modes can be confirmed. For the dominant mode, we have found that, by increasing the facet width, the resonance can be tuned linearly to the red with little decrease of the peak near-field intensity. It is further demonstrated that by increasing the NP size, the near-field intensity can be strongly enhanced. Understanding of such extreme optics benefits significantly both the optimized design of potential plasmonic devices and the fundamental understanding of nano-optics. Collaborative experimental considerations are expected with the rapid development of nanotechnology.

  3. Broadband field enhancement of THz electromagnetic wave by surface-textured micron PVDF cylinders

    NASA Astrophysics Data System (ADS)

    Li, Xinxin; Liu, Xuan; Zhang, Luoning; Zhou, Jing; Liu, Dahe

    2015-07-01

    A cylindrical dimmer system is proposed to realize broadband field enhancement for terahertz (THz) electromagnetic wave. A surface-textured crescent-shaped cylinder is proposed to red-shift the absorption spectrum comparing to the traditional crescent-shaped cylinder based on the concept of spoof surface plasmons. Such cylinders made of ferroelectric polyvinylidene fluoride can realize the electromagnetic wave harvesting at terahertz frequencies with a broadband and huge absorption cross section. Two such cylinders in close proximity could achieve considerable electromagnetic field enhancement and field confinement in the gap, which could be applied in THz molecules detection, toxic chemical sensing, and safety screening and could break the detection binding that limits the molecules <100 nm.

  4. Electric field-induced emission enhancement and modulation in individual CdSe nanowires.

    PubMed

    Vietmeyer, Felix; Tchelidze, Tamar; Tsou, Veronica; Janko, Boldizsar; Kuno, Masaru

    2012-10-23

    CdSe nanowires show reversible emission intensity enhancements when subjected to electric field strengths ranging from 5 to 22 MV/m. Under alternating positive and negative biases, emission intensity modulation depths of 14 ± 7% are observed. Individual wires are studied by placing them in parallel plate capacitor-like structures and monitoring their emission intensities via single nanostructure microscopy. Observed emission sensitivities are rationalized by the field-induced modulation of carrier detrapping rates from NW defect sites responsible for nonradiative relaxation processes. The exclusion of these states from subsequent photophysics leads to observed photoluminescence quantum yield enhancements. We quantitatively explain the phenomenon by developing a kinetic model to account for field-induced variations of carrier detrapping rates. The observed phenomenon allows direct visualization of trap state behavior in individual CdSe nanowires and represents a first step toward developing new optical techniques that can probe defects in low-dimensional materials.

  5. Electrospun MgO-loaded carbon nanofibers: Enhanced field electron emission from the fibers in vacuum

    NASA Astrophysics Data System (ADS)

    Aykut, Yakup

    2013-02-01

    MgO-loaded electrospun carbon nanofibers (MgO/CNFs) were prepared by electrospinning a magnesium acetate containing polyacrylonitrile composite followed by stabilization under an air atmosphere at 280 °C and carbonization under a nitrogen atmosphere at 800 °C. In addition to investigating the morphological and material features of the nanofibers, the field emission (FE) characteristics of the carbonized NFs (CNFs), performed in an ultra-high vacuum chamber utilizing scanning electron microscopy (SEM), were determined. The results of the investigation show that the MgO/CNFs (195.5% enhancement) display enhanced field electron emission as compared to that of pure CNFs as a result of the existence of a MgO phase. Consequently, it appears that the graphitic structures of CNFs can be tuned, a finding that has significance in studies aimed at developing new field electron emission devices.

  6. Nanoparticle-on-mirror cavity modes for huge and/or tunable plasmonic field enhancement.

    PubMed

    Huang, Yu; Ma, Lingwei; Li, Jianghao; Zhang, Zhengjun

    2017-03-10

    We present a careful numerical study of nanoparticle (NP) faceting, highlighting the great influence of small morphological changes of NP-mirror cavities on near-field enhancement in the nanoparticle-on-mirror (NPOM) system. Using a 3D finite element method (FEM) plasmon mapping method, the active transverse cavity modes can be confirmed. For the dominant mode, we have found that, by increasing the facet width, the resonance can be tuned linearly to the red with little decrease of the peak near-field intensity. It is further demonstrated that by increasing the NP size, the near-field intensity can be strongly enhanced. Understanding of such extreme optics benefits significantly both the optimized design of potential plasmonic devices and the fundamental understanding of nano-optics. Collaborative experimental considerations are expected with the rapid development of nanotechnology.

  7. Suppression of tunneling rate fluctuations in tunnel field-effect transistors by enhancing tunneling probability

    NASA Astrophysics Data System (ADS)

    Mori, Takahiro; Migita, Shinji; Fukuda, Koichi; Asai, Hidehiro; Morita, Yukinori; Mizubayashi, Wataru; Liu, Yongxun; O’uchi, Shin-ichi; Fuketa, Hiroshi; Otsuka, Shintaro; Yasuda, Tetsuji; Masahara, Meishoku; Ota, Hiroyuki; Matsukawa, Takashi

    2017-04-01

    This paper discusses the impact of the tunneling probability on the variability of tunnel field-effect transistors (TFETs). Isoelectronic trap (IET) technology, which enhances the tunneling current in TFETs, is used to suppress the variability of the ON current and threshold voltage. The simulation results show that suppressing the tunneling rate fluctuations results in suppression of the variability. In addition, a formula describing the relationship between the tunneling rate fluctuations and the electric field strength is derived based on Kane’s band-to-band tunneling model. This formula indicates that the magnitude of the tunneling rate fluctuations is proportional to the magnitude of the fluctuations in the electric field strength and a higher tunneling probability results in a lower variability. The derived relationship is universally valid for any technologies that exploit enhancement of the tunneling probability, including IET technology, channel material engineering, heterojunctions, strain engineering, etc.

  8. Quantum plasmonics: nonlinear effects in the field enhancement of a plasmonic nanoparticle dimer.

    PubMed

    Marinica, D C; Kazansky, A K; Nordlander, P; Aizpurua, J; Borisov, A G

    2012-03-14

    A fully quantum mechanical investigation using time-dependent density functional theory reveals that the field enhancement in a coupled nanoparticle dimer can be strongly affected by nonlinear effects. We show that both classical as well as linear quantum mechanical descriptions of the system fail even for moderate incident light intensities. An interparticle current resulting from the strong field photoemission tends to neutralize the plasmon-induced surface charge densities on the opposite sides of the nanoparticle junction. Thus, the coupling between the two nanoparticles and the field enhancement is reduced as compared to linear theory. A substantial nonlinear effect is revealed already at incident powers of 10(9) W/cm(2) for interparticle separation distances as large as 1 nm and down to the touching limit.

  9. Enhanced electrocaloric cooling in ferroelectric single crystals by electric field reversal

    NASA Astrophysics Data System (ADS)

    Ma, Yang-Bin; Novak, Nikola; Koruza, Jurij; Yang, Tongqing; Albe, Karsten; Xu, Bai-Xiang

    2016-09-01

    An improved thermodynamic cycle is validated in ferroelectric single crystals, where the cooling effect of an electrocaloric refrigerant is enhanced by applying a reversed electric field. In contrast to the conventional adiabatic heating or cooling by on-off cycles of the external electric field, applying a reversed field is significantly improving the cooling efficiency, since the variation in configurational entropy is increased. By comparing results from computer simulations using Monte Carlo algorithms and experiments using direct electrocaloric measurements, we show that the electrocaloric cooling efficiency can be enhanced by more than 20% in standard ferroelectrics and also relaxor ferroelectrics, like Pb (Mg1 /3 /Nb2 /3)0.71Ti0.29O3 .

  10. Preferential acceleration and magnetic field enhancement in plasmas with e+/e- beam injection

    NASA Astrophysics Data System (ADS)

    Huynh, Cong Tuan; Ryu, Chang-Mo

    2016-03-01

    A theoretical model of current filaments predicting preferential acceleration/deceleration and magnetic field enhancement in a plasma with e+/e- beam injection is presented. When the e+/e- beams are injected into a plasma, current filaments are formed. The beam particles are accelerated or decelerated depending on the types of current filaments in which they are trapped. It is found that in the electron/ion ambient plasma, the e+ beam particles are preferentially accelerated, while the e- beam particles are preferentially decelerated. The preferential particle acceleration/deceleration is absent when the ambient plasma is the e+/e- plasma. We also find that the particle momentum decrease can explain the magnetic field increase during the development of Weibel/filamentation instability. Supporting simulation results of particle acceleration/deceleration and magnetic field enhancement are presented. Our findings can be applied to a wide range of astrophysical plasmas with the e+/e- beam injection.

  11. Two degrees of freedom piezoelectric vibration energy harvester

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Liu, Shengsheng; Cao, Junyi; Zhou, Shengxi; Lin, Jing

    2016-04-01

    Recently, vibration energy harvesting from surrounding environments to power wearable devices and wireless sensors in structure health monitoring has received considerable interest. Piezoelectric conversion mechanism has been employed to develop many successful energy harvesting devices due to its simple structure, long life span, high harvesting efficiency and so on. However, there are many difficulties of microscale cantilever configurations in energy harvesting from low frequency ambient. In order to improve the adaptability of energy harvesting from ambient vibrations, a two degrees of freedom (2-DOF) magnetic-coupled piezoelectric energy harvester is proposed in this paper. The electromechanical governing models of the cantilever and clamped hybrid energy harvester are derived to describe the dynamic characteristics for 2-DOF magnetic-coupled piezoelectric vibration energy harvester. Numerical simulations based on Matlab and ANSYS software show that the proposed magnetically coupled energy harvester can enhance the effective operating frequency bandwidth and increase the energy density. The experimental voltage responses of 2-DOF harvester under different structure parameters are acquired to demonstrate the effectiveness of the lumped parameter model for low frequency excitations. Moreover, the proposed energy harvester can enhance the energy harvesting performance over a wider bandwidth of low frequencies and has a great potential for broadband vibration energy harvesting.

  12. Enhancement of Cd phytoextraction by hyperaccumulator Sedum alfredii using electrical field and organic amendments.

    PubMed

    Xiao, Wendan; Li, Dan; Ye, Xuezhu; Xu, Haizhou; Yao, Guihua; Wang, Jingwen; Zhang, Qi; Hu, Jing; Gao, Na

    2017-02-01

    The combined use of organic amendment-assisted phytoextraction and electrokinetic remediation to decontaminate Cd-polluted soil was demonstrated in a laboratory-scale experiment. The plant species selected was the hyperaccumulator Sedum alfredii. Prior to the pot experiment, the loamy soil was treated with 15 g kg(-1) of pig manure compost, 10 g kg(-1) of humic acid, or 5 mmol kg(-1) of EDTA, and untreated soil without application of any amendment was the control. Two conditions were applied to each treatment: no voltage (without an electrical field) and a direct current (DC) electrical field (1 V cm(-1) with switching polarity every day). Results indicated that Cd concentrations in S. alfredii were significantly (p < 0.05) increased by application of the electrical field and soil amendments (pig manure compost, humic acid, and EDTA). By switching the polarity of the DC electrical field, significant pH variation from anode to cathode can be avoided, and no significant impact was observed on shoot biomass production. Electrical field application increased DTPA-extractable Cd in soils and the Cd accumulation in shoots by 6.06-15.64 and 24.53-52.31%, respectively. The addition of pig manure compost and humic acid enhanced shoot Cd accumulation by 1.54- to 1.92- and 1.38- to 1.64-fold because of their simultaneous enhancement of Cd concentration in shoots and biomass production. However, no enhancement of Cd accumulation was found in the EDTA treatment, which can be ascribed to the inhibition of plant growth caused by EDTA. In conclusion, pig manure compost or humic acid addition in combination with the application of a switched-polarity DC electrical field could significantly enhance Cd phytoextraction by hyperaccumulator S. alfredii.

  13. Piezoelectric and dielectric properties of nanoporous polyvinylidence fluoride (PVDF) films

    NASA Astrophysics Data System (ADS)

    Zhao, Ping; Wang, Shifa; Kadlec, Alec

    2016-04-01

    A nanoporous polyvinylidene Fluoride (PVDF) thin film was developed for applications in energy harvesting, medical surgeries, and industrial robotics. This sponge-like nanoporous PVDF structure dramatically enhanced the piezoelectric effect because it yielded considerably large deformation under a small force. A casting-etching method was adopted to make films, which is effective to control the porosity, flexibility, and thickness of the film. The films with various Zinc Oxide (ZnO) mass fractions ranging from 10 to 50% were fabricated to investigate the porosity effect. The piezoelectric coefficient d33 as well as dielectric constant and loss of the films were characterized. The results were analyzed and the optimal design of the film with the right amount of ZnO nanoparticles was determined.

  14. Enhanced magnetic-field-induced optical properties of nanostructured magnetic fluids by doping nematic liquid crystals

    NASA Astrophysics Data System (ADS)

    Wang, Xiang; Pu, Shengli; Ji, Hongzhu; Yu, Guojun

    2012-05-01

    Ferronematic materials composed of 4-cyano-4'-pentylbiphenyl nematic liquid crystal and oil-based Fe3O4 magnetic fluid were prepared using ultrasonic agitation. The birefringence (Δ n) and figure of merit of optical properties ( Q = Δ n/α, where α is the extinction coefficient) of pure magnetic fluids and the as-prepared ferronematic materials were examined and compared. The figure of merit of optical properties weighs the birefringence and extinction of the materials and is more appropriate to evaluate their optical properties. Similar magnetic-field- and magnetic-particle-concentration-dependent properties of birefringence and figure of merit of optical properties were obtained for the pure magnetic fluids and the ferronematic materials. For the ferronematic materials, the values of Q increase with the volume fractions of nematic liquid crystal under certain fixed field strength and are larger than those of their corresponding pure magnetic fluids at high field region. In addition, the enhancement of Q value increases monotonously with the magnetic field and becomes remarkable when the applied magnetic field is beyond 50 mT. The maximum relative enhanced value of Q R exceeds 6.8% in our experiments. The results of this work may conduce to extend the pragmatic applications of nanostructured magnetic fluids in optical field.

  15. Magnetic-Field-Assisted Assembly of Anisotropic Superstructures by Iron Oxide Nanoparticles and Their Enhanced Magnetism.

    PubMed

    Jiang, Chengpeng; Leung, Chi Wah; Pong, Philip W T

    2016-12-01

    Magnetic nanoparticle superstructures with controlled magnetic alignment and desired structural anisotropy hold promise for applications in data storage and energy storage. Assembly of monodisperse magnetic nanoparticles under a magnetic field could lead to highly ordered superstructures, providing distinctive magnetic properties. In this work, a low-cost fabrication technique was demonstrated to assemble sub-20-nm iron oxide nanoparticles into crystalline superstructures under an in-plane magnetic field. The gradient of the applied magnetic field contributes to the anisotropic formation of micron-sized superstructures. The magnitude of the applied magnetic field promotes the alignment of magnetic moments of the nanoparticles. The strong dipole-dipole interactions between the neighboring nanoparticles lead to a close-packed pattern as an energetically favorable configuration. Rod-shaped and spindle-shaped superstructures with uniform size and controlled spacing were obtained using spherical and polyhedral nanoparticles, respectively. The arrangement and alignment of the superstructures can be tuned by changing the experimental conditions. The two types of superstructures both show enhancement of coercivity and saturation magnetization along the applied field direction, which is presumably associated with the magnetic anisotropy and magnetic dipole interactions of the constituent nanoparticles and the increased shape anisotropy of the superstructures. Our results show that the magnetic-field-assisted assembly technique could be used for fabricating nanomaterial-based structures with controlled geometric dimensions and enhanced magnetic properties for magnetic and energy storage applications.

  16. Enhancement of the Initial Growth Rate of Agricultural Plants by Using Static Magnetic Fields.

    PubMed

    Kim, Seung C; Mason, Alex; Im, Wooseok

    2016-07-08

    Electronic devices and high-voltage wires induce magnetic fields. A magnetic field of 1,300-2,500 Gauss (0.2 Tesla) was applied to Petri dishes containing seeds of Garden Balsam (Impatiens balsamina), Mizuna (Brassica rapa var. japonica), Komatsuna (Brassica rapa var. perviridis), and Mescluns (Lepidium sativum). We applied magnets under the culture dish. During the 4 days of application, we observed that the stem and root length increased. The group subjected to magnetic field treatment (n = 10) showed a 1.4 times faster rate of growth compared with the control group (n = 11) in a total of 8 days (p <0.0005). This rate is 20% higher than that reported in previous studies. The tubulin complex lines did not have connecting points, but connecting points occur upon the application of magnets. This shows complete difference from the control, which means abnormal arrangements. However, the exact cause remains unclear. These results of growth enhancement of applying magnets suggest that it is possible to enhance the growth rate, increase productivity, or control the speed of germination of plants by applying static magnetic fields. Also, magnetic fields can cause physiological changes in plant cells and can induce growth. Therefore, stimulation with a magnetic field can have possible effects that are similar to those of chemical fertilizers, which means that the use of fertilizers can be avoided.

  17. Plasmon-Induced Optical Field Enhancement studied by Correlated Scanning and Photoemission Electron Microscopy

    SciTech Connect

    Peppernick, Samuel J.; Joly, Alan G.; Beck, Kenneth M.; Hess, Wayne P.

    2013-04-21

    We use multi-photon photoemission electron microscopy (PEEM) to image the enhanced electric fields of silver nanoparticles supported on a silver thin film substrate. Electromagnetic field enhancement is measured by comparing the photoelectron yield of the nanoparticles with respect to the photoelectron yield of the surrounding silver thin film. We investigate the dependence of the photoelectron yield of the nanoparticle as a function of size and shape. Multi-photon PEEM results are presented for three average nanoparticle diameters: 122 ± 6, 75 ± 6, and 34 ± 2 nm. The enhancement in photoelectron yield of single nanoparticles illuminated with femtosecond laser pulses (400 nm, ~3.1 eV) is found to be a factor of 102 to 103 times greater than that produced by the flat silver thin film. High-resolution, multi-photon PEEM images of single silver nanoparticles reveal that the greatest enhancement in photoelectron yield is localized at distinct regions on the surface of the nanoparticle whose magnitude and spatial extent is dependent on the incident electric field polarization. In conjunction with correlated scanning electron microscopy (SEM), nanoparticles that deviate from nominally spherical shapes are found to exhibit irregular spatial distributions in the multi-photon PEEM images that are correlated with the unique shape and topology of the nanoparticle.

  18. Impact of enhanced ultraviolet-B irradiance on maize yield formation and structure: a field evaluation

    NASA Astrophysics Data System (ADS)

    Gao, Wei; Zheng, Youfei; Slusser, James R.; He, Yuhong; Zhang, Ronggang

    2003-11-01

    Stratospheric ozone depletion and enhanced solar ultraviolet-B (UV-B) irradiance may have adverse impacts on the productivity of agricultural crops. Though only a small portion of the total solar electromagnetic spectrum, UV-B irradiance has a disproportionately large photobiological effect, largely because it is readily absorbed by important macromolecules such as proteins and nucleic acids. Numerous investigations have demonstrated that the effect of UV-B enhancements on plants includes a reduction in grain yield, alteration in species competition, susceptibility to disease, and changes in plant structure and pigmentation. Many experiments examining UV-B radiation effects on plants were conducted in growth chambers or greenhouses. It has been questioned if the effect of UV-B radiation on plants can be extrapolated to field responses from indoor studies because of the unnaturally high ratios of UV-B/UV-A and UV-B/PAR in many indoor studies. Field studies on UV-B radiation effect on plants have been recommended in order to use the UV and PAR irradiance provided by natural light. This study found the maize yield formation and yield structural elements responded to enhanced UV-B radiation under field conditions. Enhanced UV-B radiation caused a significant reduction of the dry matter accumulation and the maize grain yield in turn was affected. Analysis of yield structure indicates that the maize yield decreased with increased UV-B radiation and was evidently related to the decreased kernel weight and kernel number per ear.

  19. Molecular harmonic extension and enhancement from H2 + ions in the presence of spatially inhomogeneous fields

    NASA Astrophysics Data System (ADS)

    Feng, Liqiang

    2015-11-01

    Molecular high-order harmonic generation from the H2 + ion driven by spatial inhomogeneous fields consisting of the chirped pulse and a terahertz pulse has been theoretically investigated by numerically solving the non-Born-Oppenheimer time-dependent Schrödinger equation. It shows that with the introduction of the chirp as well as the spatial inhomogeneity of the pulse, not only the harmonic cutoff is remarkably extended, but also the single short quantum path is selected to contribute to the harmonic spectra. Moreover, through investigation the effects of the laser and the molecular parameters on the inhomogeneous harmonic generation, we found 1.92- and 3.3-dB enhanced fields for the chirp-free and chirped inhomogeneous pulses, respectively. Isotopic effect shows that intense harmonics can be generated from the lighter molecule. Furthermore, with the enhancement of the initial vibrational state and by properly adding a terahertz controlling pulse, the harmonic yield is enhanced by almost five orders of magnitude compared with the initial single chirped case. As a result, a 362-eV supercontinuum (which corresponds to a 4.0-dB laser field enhancement) with five orders of magnitude improvement is obtained. Finally, by properly superposing the harmonics, a series of intense extreme ultraviolet pulses with durations from 22 to 52 as can be produced.

  20. Field enhancement with plasmonic nano-antennas on silicon-based waveguides

    NASA Astrophysics Data System (ADS)

    Darvishzadeh-Varcheie, M.; Guclu, C.; Ragan, R.; Boyraz, O.; Capolino, F.

    2015-09-01

    Plasmonic nano antennas like dimers, have been investigated for their capability to provide a strong near-field enhancement when illuminated by external light. Traditionally these nano antennas, isolated or arrayed, are placed on a substrate and used in spectroscopy techniques. Surfaces made of such plasmonic nano antennas have been very useful for applications like surface enhanced Raman scattering in which it provides various orders of magnitude of enhanced sensitivity. These instruments however are not economic and are often not mobile since surfaces require an external beam illumination and the Raman scattering is detected by a large aperture microscope. The goal of this paper is to combine nano antennas made of gold dimers with integrated waveguide to make a spectrometer which has low cost and volume in comparison with the structure mentioned above. A technique in which optical plasmonic nano antennas are located in proximity of silicon nitride waveguide is proposed that is useful both for illumination and detection channels. The waveguide evanescent field, which is decaying outside of the waveguide, excites the dimer and causes it to resonate which results in a very strong electric field enhancement of approximately 25 times in the antenna gap. Also the coupling effect of dimer resonance on waveguide modes is investigated. To show the efficiency of the proposed structure, full wave analysis has been done and its results are compared with the multilayer structure case. The simulation results demonstrate that this structure can be designed and fabricated for the purpose of spectroscopy application.