Low-cost solar array project progress and plans

NASA Technical Reports Server (NTRS)

Callaghan, W. T.

1981-01-01

The considered project is part of the DOE Photovoltaic Technology and Market Development Program. This program is concerned with the development and the utilization of cost-competitive photovoltaic systems. The project has the objective to develop, by 1986, the national capability to manufacture low-cost, long-life photovoltaic arrays at production rates that will realize economies of scale, and at a price of less than $0.70/watt. The array performance objectives include an efficiency greater than 10% and an operating lifetime longer than 20 years. The objective of the silicon material task is to establish the practicality of processes for producing silicon suitable for terrestrial photovoltaic applications at a price of $14/kg. The large-area sheet task is concerned with the development of process technology for sheet formation. Low-cost encapsulation material systems are being developed in connection with the encapsulation task. Another project goal is related to the development of economical process sequences.

Adaptable silicon-carbon nanocables sandwiched between reduced graphene oxide sheets as lithium ion battery anodes.

PubMed

Wang, Bin; Li, Xianglong; Zhang, Xianfeng; Luo, Bin; Jin, Meihua; Liang, Minghui; Dayeh, Shadi A; Picraux, S T; Zhi, Linjie

2013-02-26

Silicon has been touted as one of the most promising anode materials for next generation lithium ion batteries. Yet, how to build energetic silicon-based electrode architectures by addressing the structural and interfacial stability issues facing silicon anodes still remains a big challenge. Here, we develop a novel kind of self-supporting binder-free silicon-based anodes via the encapsulation of silicon nanowires (SiNWs) with dual adaptable apparels (overlapped graphene (G) sheaths and reduced graphene oxide (RGO) overcoats). In the resulted architecture (namely, SiNW@G@RGO), the overlapped graphene sheets, as adaptable but sealed sheaths, prevent the direct exposure of encapsulated silicon to the electrolyte and enable the structural and interfacial stabilization of silicon nanowires. Meanwhile, the flexible and conductive RGO overcoats accommodate the volume change of embedded SiNW@G nanocables and thus maintain the structural and electrical integrity of the SiNW@G@RGO. As a result, the SiNW@G@RGO electrodes exhibit high reversible specific capacity of 1600 mAh g⁻¹ at 2.1 A g⁻¹, 80% capacity retention after 100 cycles, and superior rate capability (500 mAh g⁻¹ at 8.4 A g⁻¹) on the basis of the total electrode weight.

An accelerated stress testing program for determining the reliability sensitivity of silicon solar cells to encapsulation and metallization systems

NASA Technical Reports Server (NTRS)

Lathrop, J. W.; Davis, C. W.; Royal, E.

1982-01-01

The use of accelerated testing methods in a program to determine the reliability attributes of terrestrial silicon solar cells is discussed. Different failure modes are to be expected when cells with and without encapsulation are subjected to accelerated testing and separate test schedules for each are described. Unencapsulated test cells having slight variations in metallization are used to illustrate how accelerated testing can highlight different diffusion related failure mechanisms. The usefulness of accelerated testing when applied to encapsulated cells is illustrated by results showing that moisture related degradation may be many times worse with some forms of encapsulation than with no encapsulation at all.

High-power, ultralow-mass solar arrays: FY-77 solar arrays technology readiness assessment report, volume 2

NASA Technical Reports Server (NTRS)

Costogue, E. N.; Young, L. E.; Brandhorst, H. W., Jr.

1978-01-01

Development efforts are reported in detail for: (1) a lightweight solar array system for solar electric propulsion; (2) a high efficiency thin silicon solar cell; (3) conceptual design of 200 W/kg solar arrays; (4) fluorocarbon encapsulation for silicon solar cell array; and (5) technology assessment of concentrator solar arrays.

Investigation of test methods, material properties and processes for solar cell encapsulants

NASA Technical Reports Server (NTRS)

Willis, P. B.; Baum, B.

1977-01-01

The potentially useful encapsulating materials for Task 3 of the Low-Cost Silicon Solar Array project were studied to identify, evaluate, and recommend encapsulant materials and processes for the production of cost-effective, long-life solar cell modules. Materials for study were chosen on the basis of existing knowledge of generic chemical types having high resistance to environmental weathering. The materials varied from rubbers to thermoplastics and presented a broad range of mechanical properties and processing requirements. Basic physical and optical properties were measured on the polymers and were redetermined after exposure to indoor artificial accelerated aging conditions covering four time periods. Strengths and weaknesses of the various materials were revealed and data was accumulated for the development of predictive methodologies. To date, silicone rubbers, fluorocarbons, and acrylic polymers appear to have the most promising combination of characteristics. The fluorocarbons may be used only as films, however, because of their high cost.

The 17th Project Integration Meeting

NASA Technical Reports Server (NTRS)

Mcdonald, R. R.

1981-01-01

Progress made by the Low-Cost Solar Array Project during the period September 1980 to February 1981 is described. Included are reports on project analysis and integration; technology development in silicon material, large-area silicon sheet and encapsulation; production process and equipment development; engineering, and operations. A report on and copies of visual presentations made at the Project Integration Meeting held at Pasadena, California on February 4 and 5, 1981 are also included.

Novel Encapsulation Method for Flexible Organic Light-Emitting Diodes using Poly(dimethylsiloxane)

NASA Astrophysics Data System (ADS)

Han, Jeong-Min; Han, Jin-Woo; Chun, Ji-Yun; Ok, Chul-Ho; Seo, Dae-Shik

2008-12-01

We have developed a novel encapsulation method for flexible organic light-emitting diodes (OLEDs) using poly(dimethylsiloxane) (PDMS). The new method, which uses polycarbonate film, silicon dioxide, and PDMS, was found to enhance the lifetime of OLEDs in air. Optical measurements of the preservation of calcium films encapsulated with PDMS showed that the water and oxygen permeation rates of the PDMS encapsulation were reduced from a level of 0.57 g m-2 d-1 (bare substrate) to 1×10-7 g m-2 d-1. These results indicate that the PDMS barrier coatings have a good potential for flexible OLED applications.

Choosing a Silicone Encapsulant for Photovoltaic Applications

NASA Astrophysics Data System (ADS)

Velderrain, Michelle

2011-12-01

Growth in the solar industry has resulted in newer technologies, specifically concentrator photovoltaic (CPV) modules, to explore using new types of materials such as silicone encapsulants. CPV and LCPV module designs are to achieve the most efficient energy conversion possible however it is equally important to demonstrate long term reliability. Silicone is a material of interest due to its thermal stability and ability to absorb stresses incurred during thermal cycling. The refractive index of clear silicone adhesives is advantageous because it can be optimized using phenyl groups to match BK7 glass and other substrates to minimize light loss at the interfaces but it is relatively unknown how the optical properties change over time possibly yellowing in such a harsh environment. A 1.41 silicone encapsulant is compared to a 1.52 refractive index silicone. Optical Absorption (300 nm-1300 nm), Water Vapor Permeability, Moisture Absorption and effects of oxidation at elevated temperatures will be compared of these materials to aid the engineer in choosing a silicone for their CPV application. Non-phenyl containing 1.41 RI silicones have been used for several years for bonding solar arrays in the satellite industry. Phenyl groups on the siloxane polymer can change various properties of the silicone. Understanding how phenyl affects these properties allows the engineer to understand the benefits and risks when using a RI matching silicone to minimize light loss versus a non-phenyl containing silicone.

Spraylon fluorocarbon encapsulation for silicon solar cell arrays

NASA Technical Reports Server (NTRS)

1977-01-01

A development program was performed for evaluating, modifying, and optimizing the Lockheed formulated liquid transparent filmforming Spraylon fluorocarbon protective coating for silicon solar cells and modules. The program objectives were designed to meet the requirements of the low-cost automated solar cell array fabrication process. As part of the study, a computer program was used to establish the limits of the safe working stress in the coated silicon solar cell array system under severe thermal shock.

Recent progress in terrestrial photovoltaic collector technology

NASA Technical Reports Server (NTRS)

Ferber, R. R.

1982-01-01

The U.S. Photovoltaic Research and Development Program has the objective to develop the technology necessary to foster widespread grid-competitive electric power generation by the late 1980s. The flat-plate and the concentrator collector activities form the nucleus of the program. The project is concerned with the refining of silicon, silicon sheet production, solar cell processing and fabrication, encapsulation materials development, and collector design and production. The Large-Area Silicon Sheet Task has the objective to develop and demonstrate the feasibility of several methods for producing large area silicon sheet material suitable for fabricating low-cost, high-efficiency solar cells. It is expected that a variety of economic flat-plate and concentrator collectors will become commercially available for grid-connected applications.

Evaluation of cleaners for photovoltaic modules exposed in an outdoor environment

NASA Technical Reports Server (NTRS)

Knapp, W. D.

1979-01-01

Power recovery of silicone encapsulated and glass covered photovoltaic modules, exposed for two years to a suburban environment, was measured after washing with a variety of cleaners including detergents, abrasive soap, and hydrocarbon solvents. Silicone encapsulated modules in operating environments may experience significant power losses or require extensive periodic cleaning. Glass front-faced modules in similar situations are much less affected. Organic hydrocarbon solvents or abrasives were found to be about five times more effective than mild detergents in cleaning encapsulated modules.

Field Testing of Thermoplastic Encapsulants in High-Temperature Installations

DOE PAGES

Kempe, Michael D.; Miller, David C.; Wohlgemuth, John H.; ...

2015-11-01

Recently there has been increased interest in using thermoplastic encapsulant materials in photovoltaic modules, but concerns have been raised about whether these would be mechanically stable at high temperatures in the field. This has become a significant topic of discussion in the development of IEC 61730 and IEC 61215. We constructed eight pairs of crystalline-silicon modules and eight pairs of glass/encapsulation/glass thin-film mock modules using different encapsulant materials, of which only two were formulated to chemically crosslink. One module set was exposed outdoors with thermal insulation on the back side in Mesa, Arizona, in the summer (hot-dry), and an identicalmore » module set was exposed in environmental chambers. High-precision creep measurements (±20 μm) and electrical performance measurements indicate that despite many of these polymeric materials operating in the melt or rubbery state during outdoor deployment, no significant creep was seen because of their high viscosity, lower operating temperature at the edges, and/or the formation of chemical crosslinks in many of the encapsulants with age despite the absence of a crosslinking agent. Only an ethylene-vinyl acetate (EVA) encapsulant formulated without a peroxide crosslinking agent crept significantly. When the crystalline-silicon modules, the physical restraint of the backsheet reduced creep further and was not detectable even for the EVA without peroxide. Because of the propensity of some polymeric materials to crosslink as they age, typical thermoplastic encapsulants would be unlikely to result in creep in the vast majority of installations.« less

Silicon nanopore membrane (SNM) for islet encapsulation and immunoisolation under convective transport

NASA Astrophysics Data System (ADS)

Song, Shang; Faleo, Gaetano; Yeung, Raymond; Kant, Rishi; Posselt, Andrew M.; Desai, Tejal A.; Tang, Qizhi; Roy, Shuvo

2016-03-01

Problems associated with islet transplantation for Type 1 Diabetes (T1D) such as shortage of donor cells, use of immunosuppressive drugs remain as major challenges. Immune isolation using encapsulation may circumvent the use of immunosuppressants and prolong the longevity of transplanted islets. The encapsulating membrane must block the passage of host’s immune components while providing sufficient exchange of glucose, insulin and other small molecules. We report the development and characterization of a new generation of semipermeable ultrafiltration membrane, the silicon nanopore membrane (SNM), designed with approximately 7 nm-wide slit-pores to provide middle molecule selectivity by limiting passage of pro-inflammatory cytokines. Moreover, the use of convective transport with a pressure differential across the SNM overcomes the mass transfer limitations associated with diffusion through nanometer-scale pores. The SNM exhibited a hydraulic permeability of 130 ml/hr/m2/mmHg, which is more than 3 fold greater than existing polymer membranes. Analysis of sieving coefficients revealed 80% reduction in cytokines passage through SNM under convective transport. SNM protected encapsulated islets from infiltrating cytokines and retained islet viability over 6 hours and remained responsive to changes in glucose levels unlike non-encapsulated controls. Together, these data demonstrate the novel membrane exhibiting unprecedented hydraulic permeability and immune-protection for islet transplantation therapy.

From cells to laminate: probing and modeling residual stress evolution in thin silicon photovoltaic modules using synchrotron X-ray micro-diffraction experiments and finite element simulations

DOE PAGES

Tippabhotla, Sasi Kumar; Radchenko, Ihor; Song, W. J. R.; ...

2017-04-12

Fracture of silicon crystalline solar cells has recently been observed in increasing percentages especially in solar photovoltaic (PV) modules involving thinner silicon solar cells (<200 μm). Many failures due to fracture have been reported from the field because of environmental loading (snow, wind, etc.) as well as mishandling of the solar PV modules (during installation, maintenance, etc.). However, a significantly higher number of failures have also been reported during module encapsulation (lamination) indicating high residual stress in the modules and thus more prone to cell cracking. Here in this paper we report through the use of synchrotron X-ray submicron diffractionmore » coupled with physics-based finite element modeling, the complete residual stress evolution in mono-crystalline silicon solar cells during PV module integration process. For the first time, we unravel the reason for the high stress and cracking of silicon cells near soldered inter-connects. Our experiments revealed a significant increase of residual stress in the silicon cell near the solder joint after lamination. Moreover, our finite element simulations show that this increase of stress during lamination is a result of highly localized bending of the cell near the soldered inter-connects. Further, the synchrotron X-ray submicron diffraction has proven to be a very effective way to quantitatively probe mechanical stress in encapsulated silicon solar cells. Thus, this technique has ultimately enabled these findings leading to the enlightening of the role of soldering and encapsulation processes on the cell residual stress. This model can be further used to suggest methodologies that could lead to lower stress in encapsulated silicon solar cells, which are the subjects of our continued investigations.« less

From cells to laminate: probing and modeling residual stress evolution in thin silicon photovoltaic modules using synchrotron X-ray micro-diffraction experiments and finite element simulations

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

Tippabhotla, Sasi Kumar; Radchenko, Ihor; Song, W. J. R.

Fracture of silicon crystalline solar cells has recently been observed in increasing percentages especially in solar photovoltaic (PV) modules involving thinner silicon solar cells (<200 μm). Many failures due to fracture have been reported from the field because of environmental loading (snow, wind, etc.) as well as mishandling of the solar PV modules (during installation, maintenance, etc.). However, a significantly higher number of failures have also been reported during module encapsulation (lamination) indicating high residual stress in the modules and thus more prone to cell cracking. Here in this paper we report through the use of synchrotron X-ray submicron diffractionmore » coupled with physics-based finite element modeling, the complete residual stress evolution in mono-crystalline silicon solar cells during PV module integration process. For the first time, we unravel the reason for the high stress and cracking of silicon cells near soldered inter-connects. Our experiments revealed a significant increase of residual stress in the silicon cell near the solder joint after lamination. Moreover, our finite element simulations show that this increase of stress during lamination is a result of highly localized bending of the cell near the soldered inter-connects. Further, the synchrotron X-ray submicron diffraction has proven to be a very effective way to quantitatively probe mechanical stress in encapsulated silicon solar cells. Thus, this technique has ultimately enabled these findings leading to the enlightening of the role of soldering and encapsulation processes on the cell residual stress. This model can be further used to suggest methodologies that could lead to lower stress in encapsulated silicon solar cells, which are the subjects of our continued investigations.« less

Microfabricated biocapsules for the immunoisolation of pancreatic islets of Langerhans

NASA Astrophysics Data System (ADS)

Desai, Tejal Ashwin

1998-08-01

A silicon-based microfabricated biocapsule was developed and evaluated for use in the immunoisolation of transplanted cells, specifically pancreatic islets of Langerhans for the treatment of Type I diabetes. The transplantation of cells with specific functions is a promising therapy for a wide variety of pathologies including diabetes, Parkinson's, and hemophilia. Such transplanted cells, however, are sensitive to both cellular and humoral immune rejection as well as damage by autoimmune activity, without chronic immunosuppression. The research presented in this dissertation investigated whether microfabricated silicon-based biocapsules, with uniform membrane pore sizes in the tens of nanometer range, could provide an immunoprotective environment for pancreatic islets and other insulin-secreting cell lines, while maintaining cell viability and functionality. By utilizing fabrication techniques commonly employed in the microelectronics industry (MEMS), membranes were fabricated with precisely controlled and uniform pore sizes, allowing the optimization of biocapsule membrane parameters for the encapsulation of specific hormone-secreting cell types. The biocapsule-forming process employed bulk micromachining to define cell-containing chambers within single crystalline silicon wafers. These chambers interface with the surrounding biological environment through polycrystalline silicon filter membranes, which were surface micromachined to present a high density of uniform pores to allow sufficient permeability to oxygen, glucose, and insulin. Both in vitro and in vivo experiments established the biocompatibility of the microfabricated biocapsule, and demonstrated that encapsulated cells could live and function normally in terms of insulin-secretion within microfabricated environments for extended periods of time. This novel research shows the potential of using microfabricated biocapsules for the encapsulation of several different cell xenografts. The semipermeability of microfabricated biocapsules, their biocompatibility, along with their thermal and chemical stability, may provide an improved encapsulation device for the immunoisolation of cell xenografts in hormone-replacement and cell-based therapies.

Summary of flat-plate solar array project documentation. Abstracts of published documents, 1975 to June 1982

NASA Technical Reports Server (NTRS)

1982-01-01

Technologies that will enable the private sector to manufacture and widely use photovoltaic systems for the generation of electricity in residential, commercial, industrial, and government applications at a cost per watt that is competitive with other means is investigated. Silicon refinement processes, advanced silicon sheet growth techniques, solar cell development, encapsulation, automated fabrication process technology, advanced module/array design, and module/array test and evaluation techniques are developed.

Proceedings of the 13th Project integration meeting

NASA Technical Reports Server (NTRS)

Mcdonald, R. R.

1979-01-01

Progress made by the Low Cost Solar Array Project during the period April through August 1979 is presented. Reports are given on project analysis and integration; technology development in silicon material, large area sheet silicon, and encapsulation; production process and equipment development; engineering and operations, and a discussion of the steps taken to integrate these efforts. A report on, and copies of viewgraphs presented at the Project Integration Meeting held August 22-23, 1979 are presented.

Study of silicone-based materials for the packaging of optoelectronic devices

NASA Astrophysics Data System (ADS)

Lin, Yeong-Her

The first part of this work is to evaluate the main materials used for the packaging of high power light-emitting diodes (LEDs), i.e., the die attach materials, the encapsulant materials, and high color rendering index(CRI) sol-gel composite materials. All of these materials had been discussed the performance, reliability, and issues in high power LED packages. High power white LEDs are created either from blue or near-ultraviolet chips encapsulated with a yellow phosphor, or from red-green-blue LED light mixing systems. The phosphor excited by blue LED chip was mostly used in experiment of this dissertation. The die attach materials contains filler particles possessing a maximum particle size less than 1.5 mum in diameter blended with epoxy polymer matrix. Such compositions enable thin bond line thickness, which decreases thermal resistance that exists between thermal interface materials and the corresponding mating surfaces. The thermal conductivity of nano silver die attach materials is relatively low, the thermal resistance from the junction to board is just 1.6 KW-1 in the bond line thickness of 5.3 mum, which is much lower than the thermal resistance using conventional die attach materials. The silicone die attach adhesive made in the lab cures through the free radical reaction of epoxy-functional organopolysiloxane and through the hydrosilylation reaction between alkenyl-functional organopolysiloxane and silicone-boned hydrogen-functional organopolysiloxane. By the combination of the free radical reaction and the hydrosilylation reaction, the low-molecular-weight silicone oil will not be out-migrated and not contaminate wire bondability to the LED chip and lead frame. Hence, the silicone die attach adhesive made in the lab can pass all reliability tests, such as operating life test JEDEC 85°C/85RH and room temperature operating life test. For LED encapsulating materials, most of commercial silicone encapsulants still suffer thermal/radiation induced degradations, and thus cause reliability issues and shorten the lifetime. A new high performance silicone has been developed and its performance has been compared with other commercial silicone products in the packaging of high power white LEDs. The high performance silicone also has better results than commercial high refractive index silicone and optical grade epoxy under JEDEC reliability standard for moisture sensitivity test. In synthesis of red dye-doped particles by sol-gel method, it is a novel method to get high color rendering index (CRI) LEDs. These red dye-doped particles, with average diameter of 5 mum, can be mixed with liquid encapsulants to form a uniform distribution in polymer matrix. The red dye-doped particles can be excited by phosphor-emitted yellow light instead of blue light from LED chip. Therefore, warm white LEDs with high CRI can be gotten at high lumen efficiency. The second part of this work is silicone elastomer for biomedical applications, especially in making urological implantable devices. A cross-linked, heat curable, addition-reaction silicone material is prepared. The material may be molded or formed into one or more medical devices. One such medical device could be a catheter used in urological applications. The material is a long term indwelling material that resists encrustation like a metal stent, but is more comfortable because it is silicone-based. The material can be made relatively cheaply compared to metal stents. Furthermore, the material is biocompatible with bladder epithelial cells.

Integral glass encapsulation for solar arrays

NASA Technical Reports Server (NTRS)

Young, P. R.

1977-01-01

Electrostatic bonding has been used to join silicon solar cells to borosilicate glass without the aid of any organic binders or adhesives. The results of this investigation have been to demonstrate, without question, the feasibility of this process as an encapsulation technique. The potential of ESB for terrestrial solar arrays was clearly shown. The process is fast, reproducible, and produces a permanent bond between glass and silicon that is stronger than the silicon itself. Since this process is a glass sealing technique requiring no organics it makes moisture tight sealing of solar cells possible.

Encapsulant selection and durability testing experience

NASA Technical Reports Server (NTRS)

Cuddihy, E. F.

1985-01-01

The Flat Plate Solar Array Project (FSA) has established technically challenging cost and service life goals for photovoltaic modules. These goals are a cost of $70 sq m and an expected 30 years of service life in an outdoor weathering environment. out of the cost goal, $14 sq m is allocated for encapsulation materials, which includes the cost of a structural panel. At FSA's inception in 1975, the cumulative cost of encapsulation materials in popular use, such as room temperature vulcanized (RTV) silicones, aluminum panels, etc., greatly exceeded $14/sq m. Accordingly, it became necessary to identify and/or develop new materials and new material technologies to achieve the goals. Many of these new materials are low cost polymers that satisfy module engineering and encapsulation processing requirements but unfortunately are not intrinsically weather stable. This necessitates identifying lifetime and/or weathering deficiencies inherent in these low cost materials and developing specific approaches to enhancing weather stability.

Production development of organic nonflammable spacecraft potting encapsulating and conformal coating compounds. Volume 2: Tables

NASA Technical Reports Server (NTRS)

Lieberman, S. L.

1974-01-01

Tables are presented which include: material properties; elemental analysis; silicone RTV formulations; polyester systems and processing; epoxy preblends and processing; urethane materials and processing; epoxy-urethanes elemental analysis; flammability test results, and vacuum effects.

The use of silicone based adhesives to encapsulate manganin gauges for high stress experiments

NASA Astrophysics Data System (ADS)

Be'Ery, Ilan; Rosenberg, Zvi

2007-06-01

The use of commercial manganin stress gauges has been limited to stresses in the range of 0-20 GPa due to the short-circuiting of their encapsulating materials (epoxy, Kapton) at higher pressures. Researchers at Lawrence Livermore overcome this difficulty by embedding their gauges in Teflon sheets and measured shock pressures as high as 40 GPa. The fact that Teflon can keep its resistivity at high pressures is attributed to the lack of benzene rings in its structure. On the other hand, Teflon is difficult to work with as an encapsulating material because of its poor adhesive properties. In order to overcome this difficulty we encapsulated our foils in between two tapes of Teflon which have a silicone adhesive glued to it. These are 50 μm thick commercial tapes (manufactured by 3M, type #60) which have a 50 μm thick silicone adhesive (PSA -- pressure sensitive adhesive) on them. This adhesive is easy to work with, has no benzene rings in its structure and has a lower carbon content, compared to other adhesives. Several experiments were conducted in order to directly measure the resistivity of these tapes at high pressures, as well as using them to encapsulate our manganin foils for high pressure studies.

Comparative study of singlet oxygen production by photosensitiser dyes encapsulated in silicone: towards rational design of anti-microbial surfaces.

PubMed

Noimark, Sacha; Salvadori, Enrico; Gómez-Bombarelli, Rafael; MacRobert, Alexander J; Parkin, Ivan P; Kay, Christopher W M

2016-10-12

Surfaces with built-in antimicrobial activity have the potential to reduce hospital-acquired infections. One promising strategy is to create functionalised surfaces which, following illumination with visible light, are able to generate singlet oxygen under aerobic conditions. In contrast to antibiotics, the mechanism of bacterial kill by species derived from reactions with singlet oxygen is completely unselective, therefore offering little room for evolutionary adaptation. Here we consider five commercially available organic photosensitiser dyes encapsulated in silicone polymer that show varied antimicrobial activity. We correlate density functional theory calculations with UV-Vis spectroscopy, electron paramagnetic resonance spectroscopy and singlet oxygen production measurements in order to define and test the elements required for efficacious antimicrobial activity. Our approach forms the basis for the rational in silico design and spectroscopic screening of simple and efficient self-sterilising surfaces made from cheap, low toxicity photosensitiser dyes encapsulated in silicone.

Integral glass encapsulation for solar arrays

NASA Technical Reports Server (NTRS)

Landis, G. A.

1981-01-01

Electrostatic bonding technology, an encapsulation technique for terrestrial solar array was developed. The process produces full integral, hermetic bonds with no adhesives or pottants. Panels of six solar cells on a simple glass superstrate were produced. Electrostatic bonding for making the cell front contact was also developed. A metal mesh is trapped into contact with the cell front during the bonding process. Six cell panels using the bonded mesh as the only cell front contact were produced. The possibility of using lower cost glass, with a higher thermal expansion mismatch to silicon, by making lower temperature bonds is developed. However, this requires a planar surface cell.

Spectral perturbations from silicon diode detector encapsulation and shielding in photon fields.

PubMed

Eklund, Karin; Ahnesjö, Anders

2010-11-01

Silicon diodes are widely used as detectors for relative dose measurements in radiotherapy. The common manufacturing practice is to encapsulate the diodes in plastic for protection and to facilitate mounting in scanning devices. Diodes intended for use in photon fields commonly also have a shield of a high atomic number material (usually tungsten) integrated into the encapsulation to selectively absorb low-energy photons to which silicon diodes would otherwise over-response. However, new response models based on cavity theories and spectra calculations have been proposed for direct correction of the readout from unshielded (e.g., "electron") diodes used in photon fields. This raises the question whether it is correct to assume that the spectrum in a water phantom at the location of the detector cavity is not perturbed by the detector encapsulation materials. The aim of this work is to investigate the spectral effects of typical encapsulations, including shielding, used for clinical diodes. The effects of detector encapsulation of an unshielded and a shielded commercial diode on the spectra at the detector cavity location are studied through Monte Carlo simulations with PENELOPE-2005. Variance reduction based on correlated sampling is applied to reduce the CPU time needed for the simulations. The use of correlated sampling is found to be efficient and to not introduce any significant bias to the results. Compared to reference spectra calculated in water, the encapsulation for an unshielded diode is demonstrated to not perturb the spectrum, while a tungsten shielded diode caused not only the desired decrease in low-energy scattered photons but also a large increase of the primary electron fluence. Measurements with a shielded diode in a 6 MV photon beam proved that the shielding does not completely remove the field-size dependence of the detector response caused by the over-response from low-energy photons. Response factors of a properly corrected unshielded diode were shown to give comparable, or better, results than the traditionally used shielded diode. Spectra calculated for photon fields in water can be directly used for modeling the response of unshielded silicon diodes with plastic encapsulations. Unshielded diodes used together with appropriate corrections can replace shielded diodes in photon dose measurements.

Fiber-Optic Temperature Sensor Using a Thin-Film Fabry-Perot Interferometer

NASA Technical Reports Server (NTRS)

Beheim, Glenn

1997-01-01

A fiber-optic temperature sensor was developed that is rugged, compact, stable, and can be inexpensively fabricated. This thin-film interferometric temperature sensor was shown to be capable of providing a +/- 2 C accuracy over the range of -55 to 275 C, throughout a 5000 hr operating life. A temperature-sensitive thin-film Fabry-Perot interferometer can be deposited directly onto the end of a multimode optical fiber. This batch-fabricatable sensor can be manufactured at a much lower cost than can a presently available sensor, which requires the mechanical attachment of a Fabry-Perot interferometer to a fiber. The principal disadvantage of the thin-film sensor is its inherent instability, due to the low processing temperatures that must be used to prevent degradation of the optical fiber's buffer coating. The design of the stable thin-film temperature sensor considered the potential sources of both short and long term drifts. The temperature- sensitive Fabry-Perot interferometer was a silicon film with a thickness of approx. 2 microns. A laser-annealing process was developed which crystallized the silicon film without damaging the optical fiber. The silicon film was encapsulated with a thin layer of Si3N4 over coated with aluminum. Crystallization of the silicon and its encapsulation with a highly stable, impermeable thin-film structure were essential steps in producing a sensor with the required long-term stability.

Encapsulation methods for organic electrical devices

DOEpatents

Blum, Yigal D.; Chu, William Siu-Keung; MacQueen, David Brent; Shi, Yijian

2013-06-18

The disclosure provides methods and materials suitable for use as encapsulation barriers in electronic devices. In one embodiment, for example, there is provided an electroluminescent device or other electronic device encapsulated by alternating layers of a silicon-containing bonding material and a ceramic material. The encapsulation methods provide, for example, electronic devices with increased stability and shelf-life. The invention is useful, for example, in the field of microelectronic devices.

Solar power roof shingle

NASA Technical Reports Server (NTRS)

Forestieri, A. F.; Ratajczak, A. F.; Sidorak, L. G.

1975-01-01

Silicon solar cell module provides both all-weather protection and electrical power. Module consists of array of circular silicon solar cells bonded to fiberglass substrate roof shingle with fluorinated ethylene propylene encapsulant.

Coupled Thermo-Mechanical and Photo-Chemical Degradation Mechanisms that determine the Reliability and Operational Lifetimes for CPV Technologies

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

Dauskardt, Reinhold H.

This project sought to identify and characterize the coupled intrinsic photo-chemo-mechanical degradation mechanisms that determine the reliability and operational lifetimes for CPV technologies. Over a three year period, we have completed a highly successful program which has developed quantitative metrologies and detailed physics-based degradation models, providing new insight into the fundamental reliability physics necessary for improving materials, creating accelerated testing protocols, and producing more accurate lifetime predictions. The tasks for the program were separated into two focus areas shown in the figure below. Focus Area 1, led by Reinhold Dauskardt and Warren Cai with a primary collaboration with David Millermore » of NREL, studied the degradation mechanisms present in encapsulant materials. Focus Area 2, led by Reinhold Dauskardt and Ryan Brock with a primary collaboration with James Ermer and Peter Hebert of Spectrolab, studied stress development and degradation within internal CPV device interfaces. Each focus area was productive, leading to several publications, including findings on the degradation of silicone encapsulant under terrestrial UV, a model for photodegradation of silicone encapsulant adhesion, quantification and process tuning of antireflective layers on CPV, and discovery of a thermal cycling degradation mechanism present in metal gridline structures.« less

Structure assignment, electronic properties, and magnetism quenching of endohedrally doped neutral silicon clusters, Si(n)Co (n = 10-12).

PubMed

Li, Yejun; Tam, Nguyen Minh; Claes, Pieterjan; Woodham, Alex P; Lyon, Jonathan T; Ngan, Vu Thi; Nguyen, Minh Tho; Lievens, Peter; Fielicke, André; Janssens, Ewald

2014-09-18

The structures of neutral cobalt-doped silicon clusters have been assigned by a combined experimental and theoretical study. Size-selective infrared spectra of neutral Si(n)Co (n = 10-12) clusters are measured using a tunable IR-UV two-color ionization scheme. The experimental infrared spectra are compared with calculated spectra of low-energy structures predicted at the B3P86 level of theory. It is shown that the Si(n)Co (n = 10-12) clusters have endohedral caged structures, where the silicon frameworks prefer double-layered structures encapsulating the Co atom. Electronic structure analysis indicates that the clusters are stabilized by an ionic interaction between the Co dopant atom and the silicon cage due to the charge transfer from the silicon valence sp orbitals to the cobalt 3d orbitals. Strong hybridization between the Co dopant atom and the silicon host quenches the local magnetic moment on the encapsulated Co atom.

Silicon switching transistor with high power and low saturation voltage

NASA Technical Reports Server (NTRS)

Stonebraker, E.; Stoneburner, D.; Ferree, H.

1973-01-01

Assembly of two individually encapsulated silicon-chip transistors produces silicon power-transistor that has low electrical resistance and low thermal impedance. Electrical resistance and thermal impedance are low because of short lead lengths, and external contact surfaces are plated to reduce resistance at interfaces.

LSSA (Low-cost Silicon Solar Array) project

NASA Technical Reports Server (NTRS)

1976-01-01

The Photovoltaic Conversion Program was established to find methods of economically generating enough electrical power to meet future requirements. Activities and progress in the following areas are discussed: silicon-refinement processes; silicon-sheet-growth techniques; encapsulants; manufacturing of off-the-shelf solar arrays; and procurement of semistandardized solar arrays.

TOPICAL REVIEW: Ultra-thin film encapsulation processes for micro-electro-mechanical devices and systems

NASA Astrophysics Data System (ADS)

Stoldt, Conrad R.; Bright, Victor M.

2006-05-01

A range of physical properties can be achieved in micro-electro-mechanical systems (MEMS) through their encapsulation with solid-state, ultra-thin coatings. This paper reviews the application of single source chemical vapour deposition and atomic layer deposition (ALD) in the growth of submicron films on polycrystalline silicon microstructures for the improvement of microscale reliability and performance. In particular, microstructure encapsulation with silicon carbide, tungsten, alumina and alumina-zinc oxide alloy ultra-thin films is highlighted, and the mechanical, electrical, tribological and chemical impact of these overlayers is detailed. The potential use of solid-state, ultra-thin coatings in commercial microsystems is explored using radio frequency MEMS as a case study for the ALD alloy alumina-zinc oxide thin film.

Development of highly durable deep-ultraviolet AlGaN-based LED multichip array with hemispherical encapsulated structures using a selected resin through a detailed feasibility study

NASA Astrophysics Data System (ADS)

Nagai, Shoko; Yamada, Kiho; Hirano, Akira; Ippommatsu, Masamichi; Ito, Masahiro; Morishima, Naoki; Aosaki, Ko; Honda, Yoshio; Amano, Hiroshi; Akasaki, Isamu

2016-08-01

To replace mercury lamps with AlGaN-based deep-ultraviolet (DUV) LEDs, a simple and low-cost package with increased light extraction efficiency (LEE) is indispensable. Therefore, resin encapsulation is considered to be a key technology. However, the photochemical reactions induced by DUV light cause serious problems, and conventional resins cannot be used. In the former part of this study, a comparison of a silicone resin and fluorine polymers was carried out in terms of their suitability for encapsulation, and we concluded that only one of the fluorine polymers can be used for encapsulation. In the latter part, the endurance of encapsulation using the selected fluorine polymer was investigated, and we confirmed that the selected fluorine polymer can guarantee a lifetime of over 6,000 h at a wavelength of 265 nm. Furthermore, a 3 × 4 array module of encapsulated dies on a simple AlN submount was fabricated, demonstrating the possibility of W/cm2-class lighting.

Chemical nature of silicon nitride-indium phosphide interface and rapid thermal annealing for InP MISFETs

NASA Technical Reports Server (NTRS)

Biedenbender, M. D.; Kapoor, V. J.

1990-01-01

A rapid thermal annealing (RTA) process in pure N2 or pure H2 was developed for ion-implanted and encapsulated indium phosphide compound semiconductors, and the chemical nature at the silicon nitride-InP interface before and after RTA was examined using XPS. Results obtained from SIMS on the atomic concentration profiles of the implanted silicon in InP before and after RTA are presented, together with electrical characteristics of the annealed implants. Using the RTA process developed, InP metal-insulator semiconductor FETs (MISFETS) were fabricated. The MISFETS prepared had threshold voltages of +1 V, transconductance of 27 mS/mm, peak channel mobility of 1200 sq cm/V per sec, and drain current drift of only 7 percent.

Chemical multisensors with selective encapsulation of ion-selective membranes

NASA Astrophysics Data System (ADS)

Schwager, Felix J.; Bousse, Luc J.; Bowman, Lyn; Meindl, J. D.

Chemical sensors fabricated with simultaneous wafer scale encapsulation of ion selective electrode mambranes are described. The sensors are miniature ion selective electrodes in chambers located on a silicon substrate. These chambers are made by anodically bonding to the silicon a no. 7740 pyrex glass wafer in which cavities were drilled. Pores with dimensions selectable from 50 microns upwards are opened in the roofs of the chambers by drilling with a CO2 laser. Each sensor die contains four cavities which are filled under reduced pressure with liquid membrane material which is subsequently polymerized. The transducers on the cavity floor are Ag/AgCl electrodes. Interconnects between the sensor chambers on each die and bonding pads are made in the silicon substrate.

Full-color OLED on silicon microdisplay

NASA Astrophysics Data System (ADS)

Ghosh, Amalkumar P.

2002-02-01

eMagin has developed numerous enhancements to organic light emitting diode (OLED) technology, including a unique, up- emitting structure for OLED-on-silicon microdisplay devices. Recently, eMagin has fabricated full color SVGA+ resolution OLED microdisplays on silicon, with over 1.5 million color elements. The display is based on white light emission from OLED followed by LCD-type red, green and blue color filters. The color filters are patterned directly on OLED devices following suitable thin film encapsulation and the drive circuits are built directly on single crystal silicon. The resultant color OLED technology, with hits high efficiency, high brightness, and low power consumption, is ideally suited for near to the eye applications such as wearable PCS, wireless Internet applications and mobile phone, portable DVD viewers, digital cameras and other emerging applications.

Low-cost encapsulation materials for terrestrial solar cell modules

NASA Technical Reports Server (NTRS)

Cuddihy, E. F.; Baum, B.; Willis, P.

1979-01-01

The paper presents the findings of material surveys intended to identify low cost materials which could be functional as encapsulants (by 1986) for terrestrial solar cell modules. Economic analyses have indicated that in order to meet the low cost goal of $2.70 per sq m, some or all of the following material technologies must be developed or advanced: (1) UV screening outer covers; (2) elastomeric acrylics; (3) weatherproofing and waterproofing of structural wood and paper products; (4) transparent UV stabilizers for the UV-sensitive transparent pottants; and (5) cost-effective utilization of silicone and fluorocarbon materials.

Electric Field Distribution in High Voltage Power Modules Using Finite Element Simulations

NASA Astrophysics Data System (ADS)

Wang, Zhao; Liu, Yaoning

2018-03-01

With the development of the high voltage insulated gate bipolar transistor (IGBT) power module, it leads to serious problems concerning the electric field insulation. The electric field capabilities of the silicone gels used in the power module encapsulation directly affect the module insulation. Some solutions have been developed to optimize the electric field and reliability. In this letter, the finite element simulation was used to analyze and localize the maximum electric field position; solutions were proposed to improve the module insulation. It’s demonstrated that BaTiO3 silicone composite is a promising insulation material for high voltage power device.

Improvement in lifetime of green organic light-emitting device

NASA Astrophysics Data System (ADS)

Ki, Hyun Chul; Kim, Seon Hoon; Kim, Doo Gun; Kim, Hyun Jin; Ko, Hang Ju; Han, Myung-Soo; Kim, Hwe Jong; Hong, Kyung Jin

2010-02-01

We have proposed a novel encapsulation method with simple process in comparison with conventional encapsulation technique. Here, the encapsulation film of silicon dioxide is steady for external environment because this can be designed to cover the emitting organic material from air. Silicon dioxide of 220 nm was deposited by plasma enhanced chemical vapor deposition and etched by reactive ion etching system. Then, Alq3 was used as a material to emitting layer in the green (organic light emitting device) OLED and TPD in the hole transportation layer was used for the harmonious transportation of hole. Luminance was measured with 40 hour intervals at the air-exposed condition. After 400, 1,000, 1,600, and 2,000 hours, luminance of green OLED were 7,366, 7,200, 6,210, and 5,100 cd/m2, respectively. Luminance of green OLED doesn't decrease until 2,000 hours. As a results, proposed encapsulation technique can increase the life time of green OLED.

Quantum confinement of nanocrystals within amorphous matrices

NASA Astrophysics Data System (ADS)

Lusk, Mark T.; Collins, Reuben T.; Nourbakhsh, Zahra; Akbarzadeh, Hadi

2014-02-01

Nanocrystals encapsulated within an amorphous matrix are computationally analyzed to quantify the degree to which the matrix modifies the nature of their quantum-confinement power—i.e., the relationship between nanocrystal size and the gap between valence- and conduction-band edges. A special geometry allows exactly the same amorphous matrix to be applied to nanocrystals of increasing size to precisely quantify changes in confinement without the noise typically associated with encapsulating structures that are different for each nanocrystal. The results both explain and quantify the degree to which amorphous matrices redshift the character of quantum confinement. The character of this confinement depends on both the type of encapsulating material and the separation distance between the nanocrystals within it. Surprisingly, the analysis also identifies a critical nanocrystal threshold below which quantum confinement is not possible—a feature unique to amorphous encapsulation. Although applied to silicon nanocrystals within an amorphous silicon matrix, the methodology can be used to accurately analyze the confinement softening of other amorphous systems as well.

Photovoltaic module encapsulation design and materials selection, volume 1

NASA Technical Reports Server (NTRS)

Cuddihy, E.; Carroll, W.; Coulbert, C.; Gupta, A.; Liang, R. H.

1982-01-01

Encapsulation material system requirements, material selection criteria, and the status and properties of encapsulation materials and processes available are presented. Technical and economic goals established for photovoltaic modules and encapsulation systems and their status are described. Available encapsulation technology and data are presented to facilitate design and material selection for silicon flat plate photovoltaic modules, using the best materials available and processes optimized for specific power applications and geographic sites. The operational and environmental loads that encapsulation system functional requirements and candidate design concepts and materials that are identified to have the best potential to meet the cost and performance goals for the flat plate solar array project are described. Available data on encapsulant material properties, fabrication processing, and module life and durability characteristics are presented.

Investigation of test methods, material properties, and processes for solar cell encapsulants

NASA Technical Reports Server (NTRS)

1984-01-01

Photovoltaic (PV) modules consist of a string of electrically interconnected silicon solar cells capable of producing practical quantities of electrical power when exposed to sunlight. To insure high reliability and long term performance, the functional components of the solar cell module must be adequately protected from the environment by some encapsulation technique. The encapsulation system must provide mechanical support for the cells and corrosion protection for the electrical components. The goal of the program is to identify and develop encapsulation systems consistent with the PV module operating requirements of 30 year life and a target cost of $0.70 per peak watt ($70 per square meter) (1980 dollars). Assuming a module efficiency of ten percent, which is equivalent to a power output of 100 watts per square meter in midday sunlight, the capital cost of the modules may be calculated to be $70.00 per square meter. Out of this cost goal, only 20 percent is available for encapsulation due to the high cost of the cells, interconnects, and other related components. The encapsulation cost allocation may then be stated as $14.00 per square meter, included all coatings, pottant and mechanical supports for the cells.

The effect of sunshine testing on terrestrial solar cell system components

NASA Technical Reports Server (NTRS)

Forestieri, A. F.; Anagnostou, E.

1975-01-01

Samples of FEP encapsulated silicon solar cells and various potential encapsulation or cover materials were subjected to accelerated and real time testing. By measuring changes in solar cell output or optical transmission as a function of exposure the durability of the samples was evaluated. Results are presented.

SPS silicon reference system

NASA Technical Reports Server (NTRS)

Woodcock, G. R.

1980-01-01

The design analysis of a silicon power conversion system for the solar power satellite (SPS) is summarized. The solar array, consisting of glass encapsulated 50 micrometer silicon solar cells, is described. The general scheme for power distribution to the array/antenna interface is described. Degradation by proton irradiation is considered. The interface between the solar array and the klystron equipped power transmitter is described.

Development of a new integral solar cell protective cover

NASA Technical Reports Server (NTRS)

Naselow, A. B.; Dupont, P. S.; Scott-Monck, J.

1983-01-01

A unique polyimide polymer has been developed which shows promise as an encapsulant for interconnected solar cell modules. Such an integral cover offers important weight and cost advantages. The polymer has been characterized on silicon solar cells with respect to electrical output and spectral response. The response of the material-coated cells to electron, low-energy proton, and vacuum-ultraviolet radiation, thermal shock and humidity tests was determined.

Feasibility study of silicon nitride protection of plastic encapsulated semiconductors

NASA Technical Reports Server (NTRS)

Peters, J. W.; Hall, T. C.; Erickson, J. J.; Gebhart, F. L.

1979-01-01

The application of low temperature silicon nitride protective layers on wire bonded integrated circuits mounted on lead frame assemblies is reported. An evaluation of the mechanical and electrical compatibility of both plasma nitride and photochemical silicon nitride (photonitride) passivations (parallel evaluations) of integrated circuits which were then encapsulated in plastic is described. Photonitride passivation is compatible with all wire bonded lead frame assemblies, with or without initial chip passivation. Plasma nitride passivation of lead frame assemblies is possible only if the chip is passivated before lead frame assembly. The survival rate after the environmental test sequence of devices with a coating of plasma nitride on the chip and a coating of either plasma nitride or photonitride over the assembled device is significantly greater than that of devices assembled with no nitride protective coating over either chip or lead frame.

Thermal and optical performance of encapsulation systems for flat-plate photovoltaic modules

NASA Technical Reports Server (NTRS)

Minning, C. P.; Coakley, J. F.; Perrygo, C. M.; Garcia, A., III; Cuddihy, E. F.

1981-01-01

The electrical power output from a photovoltaic module is strongly influenced by the thermal and optical characteristics of the module encapsulation system. Described are the methodology and computer model for performing fast and accurate thermal and optical evaluations of different encapsulation systems. The computer model is used to evaluate cell temperature, solar energy transmittance through the encapsulation system, and electric power output for operation in a terrestrial environment. Extensive results are presented for both superstrate-module and substrate-module design schemes which include different types of silicon cell materials, pottants, and antireflection coatings.

Design of Stretchable Electronics Against Impact.

PubMed

Yuan, J H; Pharr, M; Feng, X; Rogers, John A; Huang, Yonggang

2016-10-01

Stretchable electronics offer soft, biocompatible mechanical properties; these same properties make them susceptible to device failure associated with physical impact. This paper studies designs for stretchable electronics that resist failure from impacts due to incorporation of a viscoelastic encapsulation layer. Results indicate that the impact resistance depends on the thickness and viscoelastic properties of the encapsulation layer, as well as the duration of impact. An analytic model for the critical thickness of the encapsulation layer is established. It is shown that a commercially available, low modulus silicone material offers viscous properties that make it a good candidate as the encapsulation layer for stretchable electronics.

Method for extracting metals from aqueous waste streams for long term storage

DOEpatents

Chaiko, D.J.

1995-03-07

A liquid-liquid extraction method for removing metals and hydrous metal colloids from waste streams is provided wherein said waste streams are contacted with a solvent system containing a water-in-oil microemulsion wherein the inverted micelles contain the extracted metal. A silicon alkoxide, either alone or in combination with other metal alkoxide compounds is added to the water-in-oil microemulsion, thereby allowing encapsulation of the extracted metal within a silicon oxide network. Lastly, the now-encapsulated metal is precipitated from the water-in-oil microemulsion phase to yield aggregates of metal-silicate particles having average individual particle sizes of approximately 40 nanometers. 2 figs.

Method for extracting metals from aqueous waste streams for long term storage

DOEpatents

Chaiko, D.J.

1993-01-01

A liquid-liquid extraction method for removing metals and hydrous metal colloids from waste streams is provided wherein said waste streams are contacted with a solvent system containing a water-in-oil microemulsion wherein the inverted micelles contain the extracted metal. A silicon alkoxide, either alone or in combination with other metal alkoxide compounds is added to the water-in-oil microemulsion, thereby allowing encapsulation of the extracted metal within a silicon oxide network. Lastly, the now-encapsulated metal is precipitated from the water-in-oil microemulsion phase to yield aggregates of metal-silicate particles having average. individual particle sizes of approximately 40 manometers.

Method for extracting metals from aqueous waste streams for long term storage

DOEpatents

Chaiko, David J.

1995-01-01

A liquid--liquid extraction method for removing metals and hydrous metal colloids from waste streams is provided wherein said waste streams are contacted with a solvent system containing a water-in-oil microemulsion wherein the inverted micelles contain the extracted metal. A silicon alkoxide, either alone or in combination with other metal alkoxide compounds is added to the water-in-oil microemulsion, thereby allowing encapsulation of the extracted metal within a silicon oxide network. Lastly, the now-encapsulated metal is precipitated from the water-in-oil microemulsion phase to yield aggregates of metal-silicate particles having average individual particle sizes of approximately 40 nanometers.

Investigation of test methods, material properties, and processes for solar cell encapsulants. Encapsulation task of the low-cost silicon solar array project

NASA Technical Reports Server (NTRS)

1977-01-01

During this quarter, flat-plate solar collector systems were considered and six basic construction elements were identified: outer coatings, superstrates, pottants, substrates, undercoats, and adhesives. Materials surveys were then initiated to discover either generic classes or/and specific products to function as each construction element. Cost data included in the surveys permit ready evaluation of each material. Silicones, fluorocarbons, glass, and acrylic polymers have the highest inherent weatherability of materials studied to date. Only acrylics, however, combine low costs, environmental resistance, and potential processability. This class will receive particular emphasis.

Vertical Graphene Growth on SiO Microparticles for Stable Lithium Ion Battery Anodes.

PubMed

Shi, Liurong; Pang, Chunlei; Chen, Shulin; Wang, Mingzhan; Wang, Kexin; Tan, Zhenjun; Gao, Peng; Ren, Jianguo; Huang, Youyuan; Peng, Hailin; Liu, Zhongfan

2017-06-14

Silicon-based materials are considered as strong candidates to next-generation lithium ion battery anodes because of their ultrahigh specific capacities. However, the pulverization and delamination of electrochemical active materials originated from the huge volume expansion (>300%) of silicon during the lithiation process results in rapid capacity fade, especially in high mass loading electrodes. Here we demonstrate that direct chemical vapor deposition (CVD) growth of vertical graphene nanosheets on commercial SiO microparticles can provide a stable conducting network via interconnected vertical graphene encapsulation during lithiation, thus remarkably improving the cycling stability in high mass loading SiO anodes. The vertical graphene encapsulated SiO (d-SiO@vG) anode exhibits a high capacity of 1600 mA h/g and a retention up to 93% after 100 cycles at a high areal mass loading of 1.5 mg/cm 2 . Furthermore, 5 wt % d-SiO@vG as additives increased the energy density of traditional graphite/NCA 18650 cell by ∼15%. We believe that the results strongly imply the important role of CVD-grown vertical graphene encapsulation in promoting the commercial application of silicon-based anodes.

Long-lifetime thin-film encapsulated organic light-emitting diodes

NASA Astrophysics Data System (ADS)

Wong, F. L.; Fung, M. K.; Tao, S. L.; Lai, S. L.; Tsang, W. M.; Kong, K. H.; Choy, W. M.; Lee, C. S.; Lee, S. T.

2008-07-01

Multiple fluorocarbon (CFx) and silicon nitride (Si3N4) bilayers were applied as encapsulation cap on glass-based organic light-emitting diodes (OLEDs). When CFx/Si3N4 bilayers were deposited onto the OLED structure, the devices showed performance worse than one without any encapsulation. The adverse effects were attributed to the damage caused by reaction species during the thin-film deposition processes. To solve this problem, a CuPc interlayer was found to provide effective protection to the OLED structure. With a structure of CuPc/(CFx/Si3N4)×5, the encapsulated device showed an operation lifetime over 8000 h (higher than 80% of that achieved with a conventional metal encapsulation).

Encapsulation and controlled release of retinol from silicone particles for topical delivery.

PubMed

Shields, C Wyatt; White, John P; Osta, Erica G; Patel, Jerishma; Rajkumar, Shashank; Kirby, Nickolas; Therrien, Jean-Philippe; Zauscher, Stefan

2018-05-28

Retinol, a derivative of vitamin A, is a ubiquitous compound used to treat acne, reduce wrinkles and protect against conditions like psoriasis and ichthyosis. While retinol is used as the primary active ingredient (AI) in many skin care formulations, its efficacy is often limited by an extreme sensitivity to degrade and toxicity at high concentrations. While microencapsulation is an appealing method to help overcome these issues, few microencapsulation strategies have made a major translational impact due to challenges with complexity, cost, limited protection of the AI and poor control of the release of the AI. We have developed a class of silicone particles that addresses these challenges for the encapsulation, protection and controlled release of retinol and other hydrophobic compounds. The particles are prepared by the sol-gel polymerization of silane monomers, which enables their rapid and facile synthesis at scale while maintaining a narrow size distribution (i.e., CV < 20%). We show that our particles can: (i) encapsulate retinol with high efficiency (>85%), (ii) protect retinol from degradation (yielding a half-life 9× greater than unencapsulated retinol) and (iii) slowly release retinol over several hours (at rates from 0.14 to 0.67 μg cm -2  s -1/2 ). To demonstrate that the controlled release of retinol from the particles can reduce irritation, we performed a double blind study on human subjects and found that formulations containing our particles were 12-23% less irritating than identical formulations containing Microsponge® particles (an industry standard by Amcol, Inc.). To show that the silicone particles can elicit a favorable biological response, similar to the Microsponge® particles, we applied both formulations to reconstructed human epidermal tissues and found an upregulation of keratin 19 (K19) and a downregulation of K10, indicating that the reduced irritation observed in the human study was not caused by reduced activity. We also found a decrease in the production of interleukin-1α (IL-1α) compared to formulations containing the Microsponge particles, suggesting lower irritation levels and supporting the findings from the human study. Finally, we show that the silicone particles can encapsulate other AIs, including betamethasone, N, N-diethyl-meta-toluamide (DEET), homosalate and ingenol mebutate, establishing these particles as a true platform technology. Copyright © 2018. Published by Elsevier B.V.

Laminated photovoltaic modules using back-contact solar cells

DOEpatents

Gee, James M.; Garrett, Stephen E.; Morgan, William P.; Worobey, Walter

1999-09-14

Photovoltaic modules which comprise back-contact solar cells, such as back-contact crystalline silicon solar cells, positioned atop electrically conductive circuit elements affixed to a planar support so that a circuit capable of generating electric power is created. The modules are encapsulated using encapsulant materials such as EVA which are commonly used in photovoltaic module manufacture. The module designs allow multiple cells to be electrically connected in a single encapsulation step rather than by sequential soldering which characterizes the currently used commercial practices.

Polyaniline-encapsulated silicon on three-dimensional carbon nanotubes foam with enhanced electrochemical performance for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Zhou, Xiaoming; Liu, Yang; Du, Chunyu; Ren, Yang; Mu, Tiansheng; Zuo, Pengjian; Yin, Geping; Ma, Yulin; Cheng, Xinqun; Gao, Yunzhi

2018-03-01

Seeking free volume around nanostructures for silicon-based anodes has been a crucial strategy to improve cycling and rate performance in the next generation Li-ion batteries. Herein, through a simple pyrolysis and in-situ polymerization approach, the low cost commercially available melamine foam as a soft template converts carbon nanotubes into highly dispersed and three-dimensionally interconnected framework with encapsulated silicon/polyaniline hierarchical nanoarchitecture. This unique core-sheath structure based on carbon nanotubes foam integrates a large number of mesoporous, thus providing well-accessible space for electrolyte wetting, whereas the carbon nanotubes matrix serves as conductive thoroughfares for electron transport. Meanwhile, the outer polyaniline coated on silicon nanoparticles provides effective space for volume expansion of silicon, further inhibiting the active material escape from the current collector. As expected, the PANI-Si@CNTs foam exhibits a high initial specific capacity of 1954 mAh g-1 and retains 727 mAh g-1 after 100 cycles at 100 mA g-1, which can be attributed to highly electrical conductivity of carbon nanotubes and protective layer of polyaniline sheath, together with three-dimensionally interconnected porous skeleton. This facile structure can pave a way for large scale synthesis of high durable silicon-based anodes or other electrode materials with huge volume expansion.

Study program for encapsulation materials interface for low cost silicon solar array

NASA Technical Reports Server (NTRS)

Kaelble, D. H.; Mansfeld, F. B.; Lunsden, J. B., III; Leung, C.

1980-01-01

An atmospheric corrosion model was developed and verified by five months of corrosion rate and climatology data acquired at the Mead, Nebraska LSA test site. Atmospheric corrosion rate monitors (ACM) show that moisture condensation probability and ionic conduction at the corroding surface or interface are controlling factors in corrosion rate. Protection of the corroding surface by encapsulant was shown by the ACM recordings to be maintained, independent of climatology, over the five months outdoor exposure period. The macroscopic corrosion processes which occur at Mead are shown to be reproduced in the climatology simulator. Controlled experiments with identical moisture and temperature aging cycles show that UV radiation causes corrosion while UV shielding inhibits LSA corrosion.

Advanced tendencies in development of photovoltaic cells for power engineering

NASA Astrophysics Data System (ADS)

Strebkov, D. S.

2015-01-01

Development of solar power engineering must be based on original innovative Russian and world technologies. It is necessary to develop promising Russian technologies of manufacturing of photovoltaic cells and semiconductor materials: chlorine-free technology for obtaining solar silicon; matrix solar cell technology with an efficiency of 25-30% upon the conversion of concentrated solar, thermal, and laser radiation; encapsulation technology for high-voltage silicon solar modules with a voltage up to 1000 V and a service life up to 50 years; new methods of concentration of solar radiation with the balancing illumination of photovoltaic cells at 50-100-fold concentration; and solar power systems with round-the-clock production of electrical energy that do not require energy storage devices and reserve sources of energy. The advanced tendency in silicon power engineering is the use of high-temperature reactions in heterogeneous modular silicate solutions for long-term (over one year) production of heat and electricity in the autonomous mode.

Encapsulation task of the low-cost silicon solar array project. Investigation of test methods, material properties, and processes for solar cell encapsulants

NASA Technical Reports Server (NTRS)

Willis, P. B.; Baum, B.; White, R. A.

1978-01-01

The results of an investigation of solar module encapsulation systems applicable to the Low-Cost Solar Array Project 1986 cost and performance goals are presented. Six basic construction elements were identified and their specific uses in module construction defined. A uniform coating basis was established for each element. The survey results were also useful in revealing price ranges for classes of materials and estimating the cost allocation for each element within the encapsulating cost goal. The six construction elements were considered to be substrates, superstrates, pottants, adhesives, outer covers and back covers.

Comparison of Six Different Silicones In Vitro for Application as Glaucoma Drainage Device

PubMed Central

Windhövel, Claudia; Harder, Lisa; Bach, Jan-Peter; Teske, Michael; Grabow, Niels; Eickner, Thomas; Chichkov, Boris; Nolte, Ingo

2018-01-01

Silicones are widely used in medical applications. In ophthalmology, glaucoma drainage devices are utilized if conservative therapies are not applicable or have failed. Long-term success of these devices is limited by failure to control intraocular pressure due to fibrous encapsulation. Therefore, different medical approved silicones were tested in vitro for cell adhesion, cell proliferation and viability of human Sclera (hSF) and human Tenon fibroblasts (hTF). The silicones were analysed also depending on the sample preparation according to the manufacturer’s instructions. The surface quality was characterized with environmental scanning electron microscope (ESEM) and water contact angle measurements. All silicones showed homogeneous smooth and hydrophobic surfaces. Cell adhesion was significantly reduced on all silicones compared to the negative control. Proliferation index and cell viability were not influenced much. For development of a new glaucoma drainage device, the silicones Silbione LSR 4330 and Silbione LSR 4350, in this study, with low cell counts for hTF and low proliferation indices for hSF, and silicone Silastic MDX4-4210, with low cell counts for hSF and low proliferation indices for hTF, have shown the best results in vitro. Due to the high cell adhesion shown on Silicone LSR 40, 40,026, this material is unsuitable. PMID:29495462

Accelerated/abbreviated test methods, study 4 of task 3 (encapsulation) of the low-cost silicon solar array project

NASA Technical Reports Server (NTRS)

Kolyer, J. M.; Mann, N. R.

1978-01-01

Inherent weatherability is controlled by the three weather factors common to all exposure sites: insolation, temperature, and humidity. Emphasis was focused on the transparent encapsulant portion of miniature solar cell arrays by eliminating weathering effects on the substrate and circuitry (which are also parts of the encapsulant system). The most extensive data were for yellowing, which were measured conveniently and precisely. Considerable data also were obtained on tensile strength. Changes in these two properties after outdoor exposure were predicted very well from accelerated exposure data.

Tissue response to silicone rubber when used as a root canal filling.

PubMed

Kasman, F G; Goldman, M

1977-04-01

To test the tissue compatibility of silicone rubber when it is used as a root canal filler, excess material was intentionally forced into the apical tissues in primates. The tissue response was one of general acceptance, with the usual response being fibrotic encapsulation. A low degree of inflammation was noted. Further studies are in progress.

Impact of terrestrial solar cell development on space applications

NASA Astrophysics Data System (ADS)

Iles, P. A.

1980-06-01

Projected space missions are outlined and the cell requirements by mission type mentioned. The techniques used to produce low cost terrestrial use cells are examined for their applicability to space needs, including silicon cell fabrication, barrier formation, contact applications, coatings, and encapsulation. The most likely area for the transfer of terrestrial cell technology is in low Earth orbit missions, based on the use of the shuttle craft.

Performance degradation and cleaning of photovoltaic arrays

NASA Technical Reports Server (NTRS)

Sheskin, T. J.; Chang, G. C.; Cull, R. C.; Knapp, W. D.

1982-01-01

NASA tests results from an 18 mo program of cleaning silicone-encapsulated and glass fronted solar cell panels in urban and desert environments to examine the effects of cleaning on module performance are reported. The panels were cleaned on weekly, monthly, quarterly, or semi-annual basis, while other panels of the same construction were not cleaned and served as controls. Commercially-available detergents and city water were employed for the tests, and the measurements were maintained of the modules' continuing short-circuit current output. The decay of the output was determined by least square regression analyses. Performance degradation was noticeably less in glass covered, rather than silicone-encapsulated modules which decayed faster in urban than in desert environments. Lower frequency cleanings are recommended where labor costs are high.

Electrical evaluation of crack generation in SiNx and SiOxNy thin-film encapsulation layers for OLED displays

NASA Astrophysics Data System (ADS)

Park, Eun Kil; Kim, Sungmin; Heo, Jaeyeong; Kim, Hyeong Joon

2016-05-01

By measuring leakage current density, we detected crack generation in silicon nitride (SiNx) and silicon oxynitride (SiOxNy) thin-film encapsulation layers, and correlated with the films' water vapor permeability characteristics. After repeated bending cycles, both the changes in water vapor transmission rate and leakage current density were directly proportional to the crack density. Thick SiNx films had better water vapor barrier characteristics in their pristine state, but cyclic loading led to fast failure. Varying the atomic concentration of the SiOxNy films affected their bending reliability. We attribute these differences to changes in the shape of the crack tip as the oxygen content varies.

Neural electrode resilience against dielectric damage may be improved by use of highly doped silicon as a conductive material.

PubMed

Caldwell, Ryan; Sharma, Rohit; Takmakov, Pavel; Street, Matthew G; Solzbacher, Florian; Tathireddy, Prashant; Rieth, Loren

2018-01-01

Dielectric damage occurring in vivo to neural electrodes, leading to conductive material exposure and impedance reduction over time, limits the functional lifetime and clinical viability of neuroprosthetics. We used silicon micromachined Utah Electrode Arrays (UEAs) with iridium oxide (IrO x ) tip metallization and parylene C dielectric encapsulation to understand the factors affecting device resilience and drive improvements. In vitro impedance measurements and finite element analyses were conducted to evaluate how exposed surface area of silicon and IrO x affect UEA properties. Through an aggressive in vitro reactive accelerated aging (RAA) protocol, in vivo parylene degradation was simulated on UEAs to explore agreement with our models. Electrochemical properties of silicon and other common electrode materials were compared to help inform material choice in future neural electrode designs. Exposure of silicon on UEAs was found to primarily affect impedance at frequencies >1kHz, while characteristics at 1 kHz and below were largely unchanged. Post-RAA impedance reduction of UEAs was mitigated in cases where dielectric damage was more likely to expose silicon instead of IrO x . Silicon was found to have a per-area electrochemical impedance >10×higher than many common electrode materials regardless of doping level and resistivity, making it best suited for use as a low-shunting conductor. Non-semiconductor electrode materials commonly used in neural electrode design are more susceptible to shunting neural interface signals through dielectric defects, compared to highly doped silicon. Strategic use of silicon and similar materials may increase neural electrode robustness against encapsulation failures. Copyright © 2017 Elsevier B.V. All rights reserved.

Silicon dendritic web material

NASA Technical Reports Server (NTRS)

Meier, D. L.; Campbell, R. B.; Sienkiewicz, L. J.; Rai-Choudhury, P.

1982-01-01

The development of a low cost and reliable contact system for solar cells and the fabrication of several solar cell modules using ultrasonic bonding for the interconnection of cells and ethylene vinyl acetate as the potting material for module encapsulation are examined. The cells in the modules were made from dendritic web silicon. To reduce cost, the electroplated layer of silver was replaced with an electroplated layer of copper. The modules that were fabricated used the evaporated Ti, Pd, Ag and electroplated Cu (TiPdAg/Cu) system. Adherence of Ni to Si is improved if a nickel silicide can be formed by heat treatment. The effectiveness of Ni as a diffusion barrier to Cu and the ease with which nickel silicide is formed is discussed. The fabrication of three modules using dendritic web silicon and employing ultrasonic bonding for interconnecting calls and ethylene vinyl acetate as the potting material is examined.

Silicon dendritic web material

NASA Astrophysics Data System (ADS)

Meier, D. L.; Campbell, R. B.; Sienkiewicz, L. J.; Rai-Choudhury, P.

1982-03-01

The development of a low cost and reliable contact system for solar cells and the fabrication of several solar cell modules using ultrasonic bonding for the interconnection of cells and ethylene vinyl acetate as the potting material for module encapsulation are examined. The cells in the modules were made from dendritic web silicon. To reduce cost, the electroplated layer of silver was replaced with an electroplated layer of copper. The modules that were fabricated used the evaporated Ti, Pd, Ag and electroplated Cu (TiPdAg/Cu) system. Adherence of Ni to Si is improved if a nickel silicide can be formed by heat treatment. The effectiveness of Ni as a diffusion barrier to Cu and the ease with which nickel silicide is formed is discussed. The fabrication of three modules using dendritic web silicon and employing ultrasonic bonding for interconnecting calls and ethylene vinyl acetate as the potting material is examined.

Evaluation available encapsulation materials for low-cost long-life silicon photovoltaic arrays

NASA Technical Reports Server (NTRS)

Carmichael, D. C.; Gaines, G. B.; Noel, G. T.; Sliemers, F. A.; Nance, G. P.; Bunk, A. R.; Brockway, M. C.

1978-01-01

Experimental evaluation of selected encapsulation designs and materials based on an earlier study which have potential for use in low cost, long-life photovoltaic arrays are reported. The performance of candidate materials and encapsulated cells were evaluated principally for three types of encapsulation designs based on their potentially low materials and processing costs: (1) polymeric coatings, transparent conformal coatings over the cell with a structural-support substrate; (2) polymeric film lamination, cells laminated between two films or sheets of polymeric materials; and (3) glass-covered systems, cells adhesively bonded to a glass cover (superstrate) with a polymeric pottant and a glass or other substrate material. Several other design types, including those utilizing polymer sheet and pottant materials, were also included in the investigation.

Summary of flat-plate solar array project documentation: Abstracts of published documents, 1975-1986, revision 1

NASA Technical Reports Server (NTRS)

Phillips, M. J.

1986-01-01

Abstracts of final reports, or the latest quarterly or annual, of the Flat-Plate Solar Array (FSA) Project Contractor of Jet Propulsion Laboratory (JPL) in-house activities are presented. Also presented is a list of proceedings and publications, by author, of work connected with the project. The aim of the program has been to stimulate the development of technology that will enable the private sector to manufacture and widely use photovoltaic systems for the generation of electricity in residential, commercial, industrial, and Government applications at a cost per watt that is competitive with utility generated power. FSA Project activities have included the sponsoring of research and development efforts in silicon refinement processes, advanced silicon sheet growth techniques, higher efficiency solar cells, solar cell/module fabrication processes, encapsulation, module/array engineering and reliability, and economic analyses.

Assessing corrosion problems in photovoltaic cells via electrochemical stress testing

NASA Technical Reports Server (NTRS)

Shalaby, H.

1985-01-01

A series of accelerated electrochemical experiments to study the degradation properties of polyvinylbutyral-encapsulated silicon solar cells has been carried out. The cells' electrical performance with silk screen-silver and nickel-solder contacts was evaluated. The degradation mechanism was shown to be electrochemical corrosion of the cell contacts; metallization elements migrate into the encapsulating material, which acts as an ionic conducting medium. The corrosion products form a conductive path which results in a gradual loss of the insulation characteristics of the encapsulant. The precipitation of corrosion products in the encapsulant also contributes to its discoloration which in turn leads to a reduction in its transparency and the consequent optical loss. Delamination of the encapsulating layers could be attributed to electrochemical gas evolution reactions. The usefulness of the testing technique in qualitatively establishing a reliability difference between metallizations and antireflection coating types is demonstrated.

Investigation of test methods, material properties, and processes for solar cell encapsulants. Fourteenth quarterly progress report, August 12, 1978-November 12, 1979. [EVA, EPDM, aliphatic urethane, PVC plastisol, and butyl acrylate

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

Willis, P. B.; Baum, B.; Schnitzer, H. S.

1979-12-01

Springborn Laboratories is engaged in a study of evaluating potentially useful encapsulating materials for Task 3 of the Low-Cost Silicon Solar Array project (LSA) funded by DOE. The goal of this program is to identify, evaluate, and recommend encapsulant materials and processes for the production of cost-effective, long-life solar cell modules. This report presents the results of a cost analysis of candidate potting compounds for long life solar module encapsulation. Additionally, the two major encapsulation processes, sheet lamination and liquid casting, are costed on the basis of a large scale production facility. Potting compounds studied include EVA, sheet, clear; EVA,more » sheet, pigmented; EPDM, sheet, clear; Aliphatic urethane, syrup; PVC Plastisol; Butyl acrylate, syrup; and Butyl acrylate, sheet.« less

Silicon nitride protective coatings for silvered glass mirrors

DOEpatents

Tracy, C. Edwin; Benson, David K.

1988-01-01

A protective diffusion barrier for metalized mirror structures is provided by a layer or coating of silicon nitride which is a very dense, transparent, dielectric material that is impervious to water, alkali, and other impurities and corrosive substances that typically attack the metal layers of mirrors and cause degradation of the mirrors' reflectivity. The silicon nitride layer can be deposited on the substrate before metal deposition to stabilize the metal/substrate interface, and it can be deposited over the metal to encapsulate it and protect the metal from corrosion or other degradation. Mirrors coated with silicon nitride according to this invention can also be used as front surface mirrors.

Silicon nitride protective coatings for silvered glass mirrors

DOEpatents

Tracy, C.E.; Benson, D.K.

1984-07-20

A protective diffusion barrier for metalized mirror structures is provided by a layer or coating of silicon nitride which is a very dense, transparent, dielectric material that is impervious to water, alkali, and other impurities and corrosive substances that typically attack the metal layers of mirrors and cause degradation of the mirrors' reflectivity. The silicon nitride layer can be deposited on the substrate prior to metal deposition thereon to stabilize the metal/substrate interface, and it can be deposited over the metal to encapsulate it and protect the metal from corrosion or other degradation. Mirrors coated with silicon nitride according to this invention can also be used as front surface mirrors.

Induction of angiogenesis and neovascularization in adjacent tissue of plasma-collagen-coated silicone implants.

PubMed

Ring, Andrej; Langer, Stefan; Tilkorn, Daniel; Goertz, Ole; Henrich, Lena; Stricker, Ingo; Steinau, Hans-Ulrich; Steinstraesser, Lars; Hauser, Joerg

2010-09-28

Formation of encapsulating, avascular fibrous tissue is deemed to decrease implant's biocompatibility and versatility. We investigated whether plasma-mediated collagen coating possesses the ability to enhance neovascularization in the vicinity of silicone implants. Plasma-treated collagen-I-coated silicone samples were placed into the dorsal skinfold chambers of female balb/c mice (n = 10). Conventional silicone served as control (n = 10). Intravital microscopy was performed within implant's surrounding tissue on days 1, 5, and 10. Functional vessel density, intervascular distance, vessel diameter, microvascular permeability, red blood cell velocity, and leukocyte-endothelium interaction were determined. Enhanced angiogenesis in the tissue surrounding plasma-pretreated collagen-coated implants was noted. Significant increase of functional vessel density due to vascular new development was observed (t test, P < .05). Analyses of microvascular permeability and red blood cell velocity displayed stable perfusion of the vascular network neighboring the surface-modified implants. Intensified vascularity due to induced angiogenesis and neovascularization in the tissue surrounding plasma-collagen-coated samples were observed. These results indicate that plasma-mediated collagen coating might be a promising technology in order to improve the biocompatibility and versatility of silicone implants.

Induction of Angiogenesis and Neovascularization in Adjacent Tissue of Plasma-Collagen–Coated Silicone Implants

PubMed Central

Ring, Andrej; Langer, Stefan; Tilkorn, Daniel; Goertz, Ole; Henrich, Lena; Stricker, Ingo; Steinau, Hans-Ulrich; Steinstraesser, Lars; Hauser, Joerg

2010-01-01

Objective: Formation of encapsulating, avascular fibrous tissue is deemed to decrease implant's biocompatibility and versatility. We investigated whether plasma-mediated collagen coating possesses the ability to enhance neovascularization in the vicinity of silicone implants. Methods: Plasma-treated collagen-I–coated silicone samples were placed into the dorsal skinfold chambers of female balb/c mice (n = 10). Conventional silicone served as control (n = 10). Intravital microscopy was performed within implant's surrounding tissue on days 1, 5, and 10. Functional vessel density, intervascular distance, vessel diameter, microvascular permeability, red blood cell velocity, and leukocyte-endothelium interaction were determined. Results: Enhanced angiogenesis in the tissue surrounding plasma-pretreated collagen-coated implants was noted. Significant increase of functional vessel density due to vascular new development was observed (t test, P < .05). Analyses of microvascular permeability and red blood cell velocity displayed stable perfusion of the vascular network neighboring the surface-modified implants. Conclusion: Intensified vascularity due to induced angiogenesis and neovascularization in the tissue surrounding plasma-collagen–coated samples were observed. These results indicate that plasma-mediated collagen coating might be a promising technology in order to improve the biocompatibility and versatility of silicone implants. PMID:20936137

Strategies to improve electrode positioning and safety in cochlear implants.

PubMed

Rebscher, S J; Heilmann, M; Bruszewski, W; Talbot, N H; Snyder, R L; Merzenich, M M

1999-03-01

An injection-molded internal supporting rib has been produced to control the flexibility of silicone rubber encapsulated electrodes designed to electrically stimulate the auditory nerve in human subjects with severe to profound hearing loss. The rib molding dies, and molds for silicone rubber encapsulation of the electrode, were designed and machined using AutoCad and MasterCam software packages in a PC environment. After molding, the prototype plastic ribs were iteratively modified based on observations of the performance of the rib/silicone composite insert in a clear plastic model of the human scala tympani cavity. The rib-based electrodes were reliably inserted farther into these models, required less insertion force and were positioned closer to the target auditory neural elements than currently available cochlear implant electrodes. With further design improvements the injection-molded rib may also function to accurately support metal stimulating contacts and wire leads during assembly to significantly increase the manufacturing efficiency of these devices. This method to reliably control the mechanical properties of miniature implantable devices with multiple electrical leads may be valuable in other areas of biomedical device design.

Encapsulation methods and dielectric layers for organic electrical devices

DOEpatents

Blum, Yigal D; Chu, William Siu-Keung; MacQueen, David Brent; Shi, Yijan

2013-07-02

The disclosure provides methods and materials suitable for use as encapsulation barriers and dielectric layers in electronic devices. In one embodiment, for example, there is provided an electroluminescent device or other electronic device with a dielectric layer comprising alternating layers of a silicon-containing bonding material and a ceramic material. The methods provide, for example, electronic devices with increased stability and shelf-life. The invention is useful, for example, in the field of microelectronic devices.

Encapsulation of Au Nanoparticles on a Silicon Wafer During Thermal Oxidation

PubMed Central

2013-01-01

We report the behavior of Au nanoparticles anchored onto a Si(111) substrate and the evolution of the combined structure with annealing and oxidation. Au nanoparticles, formed by annealing a Au film, appear to “float” upon a growing layer of SiO2 during oxidation at high temperature, yet they also tend to become partially encapsulated by the growing silica layers. It is proposed that this occurs largely because of the differential growth rates of the silica layer on the silicon substrate between the particles and below the particles due to limited access of oxygen to the latter. This in turn is due to a combination of blockage of oxygen adsorption by the Au and limited oxygen diffusion under the gold. We think that such behavior is likely to be seen for other metal–semiconductor systems. PMID:24163715

Electrical conductivity of rigid polyurethane foam at high temperature

NASA Astrophysics Data System (ADS)

Johnson, R. T., Jr.

1982-08-01

The electrical conductivity of rigid polyurethane foam, used for electronic encapsulation, was measured during thermal decomposition to 3400 C. At higher temperatures the conductance continues to increase. With pressure loaded electrical leads, sample softening results in eventual contact between electrodes which produces electrical shorting. Air and nitrogen environments show no significant dependence of the conductivity on the atmosphere over the temperature range. The insulating characteristics of polyurethane foam below approx. 2700 C are similar to those for silicone based materials used for electronic case housings and are better than those for phenolics. At higher temperatures (greater than or equal to 2700 C) the phenolics appear to be better insulators to approx. 5000 C and the silicones to approx. 6000 C. It is concluded that the Sylgard 184/GMB encapsulant is a significantly better insulator at high temperature than the rigid polyurethane foam.

Hollow Silicon Nanospheres Encapsulated with a Thin Carbon Shell: An Electrochemical Study

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

Ashuri, Maziar; He, Qianran; Liu, Yuzi

In this study we have investigated the electrochemical properties of hollow silicon nanospheres encapsulated with a thin carbon shell, HSi@C, as a potential candidate for lithium-ion battery anodes. Hollow Si nanospheres are formed using a templating method which is followed by carbon coating via carbonization of a pyrrole precursor to form HSi@C. The synthesis conditions and the resulting structure of HSi@C have been studied in detail to obtain the target design of hollow Si nanospheres encapsulated with a carbon shell. The HSi@C obtained exhibits much better electrochemical cycle stability than both micro-and nano-size silicon anodes and deliver a stable specificmore » capacity of 700 mA h g(-1) after 100 cycles at a current density of 2 A g(-1) and 800 mA h g(-1) after 120 cycles at a current density of 1 A g(-1). The superior performance of HSi@C is attributed to the synergistic combination of the nanostructured material, the enhanced conductivity, and the presence of the central void space for Si expansion with little or no change in the volume of the entire HSi@C particle. This study is the first detailed investigation of the synthesis conditions to attain the desired structure of a hollow Si core with a conductive carbon shell. This study also offers guidelines to further enhance the specific capacity of HSi@C anodes in the future.« less

Hollow Silicon Nanospheres Encapsulated with a Thin Carbon Shell: An Electrochemical Study

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

Ashuri, Maziar; He, Qianran; Liu, Yuzi

In this study we have investigated the electrochemical properties of hollow silicon nanospheres encapsulated with a thin carbon shell, HSi@C, as a potential candidate for lithium-ion battery anodes. Hollow Si nanospheres are formed using a templating method which is followed by carbon coating via carbonization of a pyrrole precursor to form HSi@C. The synthesis conditions and the resulting structure of HSi@C have been studied in detail to obtain the target design of hollow Si nanospheres encapsulated with a carbon shell. The HSi@C obtained exhibits much better electrochemical cycle stability than both micro-and nano-size silicon anodes and deliver a stable specificmore » capacity of 700 mA h g(-1) after 100 cycles at a current density of 2 A g(-1) and 800 mA h g(-1) after 120 cycles at a current density of 1 A g(-1). The superior performance of HSi@C is attributed to the synergistic combination of the nanostructured material, the enhanced conductivity, and the presence of the central void space for Si expansion with little or no change in the volume of the entire HSi@C particle. This study is the first detailed investigation of the synthesis conditions to attain the desired structure of a hollow Si core with a conductive carbon shell. This study also offers guidelines to further enhance the specific capacity of HSi@C anodes in the future. (C) 2016 Elsevier Ltd. All rights reserved.« less

Mesoporous Silica Nanoparticles-Encapsulated Agarose and Heparin as Anticoagulant and Resisting Bacterial Adhesion Coating for Biomedical Silicone.

PubMed

Wu, Fan; Xu, Tingting; Zhao, Guangyao; Meng, Shuangshuang; Wan, Mimi; Chi, Bo; Mao, Chun; Shen, Jian

2017-05-30

Silicone catheter has been widely used in peritoneal dialysis. The research missions of improving blood compatibility and the ability of resisting bacterial adhesion of silicone catheter have been implemented for the biomedical requirements. However, most of modification methods of surface modification were only able to develop the blood-contacting biomaterials with good hemocompatibility. It is difficult for the biomaterials to resist bacterial adhesion. Here, agarose was selected to resist bacterial adhesion, and heparin was chosen to improve hemocompatibility of materials. Both of them were loaded into mesoporous silica nanoparticles (MSNs), which were successfully modified on the silicone film surface via electrostatic interaction. Structures of the mesoporous coatings were characterized in detail by dynamic light scattering, transmission electron microscopy, Brunauer-Emmett-Teller surface area, thermogravimetric analysis, Fourier transform infrared spectroscopy, scanning electron microscope, and water contact angle. Platelet adhesion and aggregation, whole blood contact test, hemolysis and related morphology test of red blood cells, in vitro clotting time tests, and bacterial adhesion assay were performed to evaluate the anticoagulant effect and the ability of resisting bacterial adhesion of the modified silicone films. Results indicated that silicone films modified by MSNs had a good anticoagulant effect and could resist bacterial adhesion. The modified silicone films have potential as blood-contacting biomaterials that were attributed to their biomedical properties.

Designing Thin, Ultrastretchable Electronics with Stacked Circuits and Elastomeric Encapsulation Materials.

PubMed

Xu, Renxiao; Lee, Jung Woo; Pan, Taisong; Ma, Siyi; Wang, Jiayi; Han, June Hyun; Ma, Yinji; Rogers, John A; Huang, Yonggang

2017-01-26

Many recently developed soft, skin-like electronics with high performance circuits and low modulus encapsulation materials can accommodate large bending, stretching, and twisting deformations. Their compliant mechanics also allows for intimate, nonintrusive integration to the curvilinear surfaces of soft biological tissues. By introducing a stacked circuit construct, the functional density of these systems can be greatly improved, yet their desirable mechanics may be compromised due to the increased overall thickness. To address this issue, the results presented here establish design guidelines for optimizing the deformable properties of stretchable electronics with stacked circuit layers. The effects of three contributing factors (i.e., the silicone inter-layer, the composite encapsulation, and the deformable interconnects) on the stretchability of a multilayer system are explored in detail via combined experimental observation, finite element modeling, and theoretical analysis. Finally, an electronic module with optimized design is demonstrated. This highly deformable system can be repetitively folded, twisted, or stretched without observable influences to its electrical functionality. The ultrasoft, thin nature of the module makes it suitable for conformal biointegration.

Designing Thin, Ultrastretchable Electronics with Stacked Circuits and Elastomeric Encapsulation Materials

PubMed Central

Xu, Renxiao; Lee, Jung Woo; Pan, Taisong; Ma, Siyi; Wang, Jiayi; Han, June Hyun; Ma, Yinji

2017-01-01

Many recently developed soft, skin-like electronics with high performance circuits and low modulus encapsulation materials can accommodate large bending, stretching, and twisting deformations. Their compliant mechanics also allows for intimate, nonintrusive integration to the curvilinear surfaces of soft biological tissues. By introducing a stacked circuit construct, the functional density of these systems can be greatly improved, yet their desirable mechanics may be compromised due to the increased overall thickness. To address this issue, the results presented here establish design guidelines for optimizing the deformable properties of stretchable electronics with stacked circuit layers. The effects of three contributing factors (i.e., the silicone inter-layer, the composite encapsulation, and the deformable interconnects) on the stretchability of a multilayer system are explored in detail via combined experimental observation, finite element modeling, and theoretical analysis. Finally, an electronic module with optimized design is demonstrated. This highly deformable system can be repetitively folded, twisted, or stretched without observable influences to its electrical functionality. The ultrasoft, thin nature of the module makes it suitable for conformal biointegration. PMID:29046624

Chemical Bonding Technology: Direct Investigation of Interfacial Bonds

NASA Technical Reports Server (NTRS)

Koenig, J. L.; Boerio, F. J.; Plueddemann, E. P.; Miller, J.; Willis, P. B.; Cuddihy, E. F.

1986-01-01

This is the third Flat-Plate Solar Array (FSA) Project document reporting on chemical bonding technology for terrestrial photovoltaic (PV) modules. The impetus for this work originated in the late 1970s when PV modules employing silicone encapsulation materials were undergoing delamination during outdoor exposure. At that time, manufacturers were not employing adhesion promoters and, hence, module interfaces in common with the silicone materials were only in physical contact and therefore easily prone to separation if, for example, water were to penetrate to the interfaces. Delamination with silicone materials virtually vanished when adhesion promoters, recommended by silicone manufacturers, were used. The activities related to the direct investigation of chemically bonded interfaces are described.

Analysis and evaluation in the production process and equipment area of the low-cost solar array project

NASA Technical Reports Server (NTRS)

Goldman, H.; Wolf, M.

1979-01-01

The energy consumed in manufacturing silicon solar cell modules was calculated for the current process, as well as for 1982 and 1986 projected processes. In addition, energy payback times for the above three sequences are shown. The module manufacturing energy was partitioned two ways. In one way, the silicon reduction, silicon purification, sheet formation, cell fabrication, and encapsulation energies were found. In addition, the facility, equipment, processing material and direct material lost-in-process energies were appropriated in junction formation processes and full module manufacturing sequences. A brief methodology accounting for the energy of silicon wafers lost-in-processing during cell manufacturing is described.

A chemically stable PVD multilayer encapsulation for lithium microbatteries

NASA Astrophysics Data System (ADS)

Ribeiro, J. F.; Sousa, R.; Cunha, D. J.; Vieira, E. M. F.; Silva, M. M.; Dupont, L.; Goncalves, L. M.

2015-10-01

A multilayer physical vapour deposition (PVD) thin-film encapsulation method for lithium microbatteries is presented. Lithium microbatteries with a lithium cobalt oxide (LiCoO2) cathode, a lithium phosphorous oxynitride (LiPON) electrolyte and a metallic lithium anode are under development, using PVD deposition techniques. Metallic lithium film is still the most common anode on this battery technology; however, it presents a huge challenge in terms of material encapsulation (lithium reacts with almost any materials deposited on top and almost instantly begins oxidizing in contact with atmosphere). To prove the encapsulation concept and perform all the experiments, lithium films were deposited by thermal evaporation technique on top of a glass substrate, with previously patterned Al/Ti contacts. Three distinct materials, in a multilayer combination, were tested to prevent lithium from reacting with protection materials and atmosphere. These multilayer films were deposited by RF sputtering and were composed of lithium phosphorous oxide (LiPO), LiPON and silicon nitride (Si3N4). To complete the long-term encapsulation after breaking the vacuum, an epoxy was applied on top of the PVD multilayer. In order to evaluate oxidation state of lithium films, the lithium resistance was measured in a four probe setup (cancelling wires/contact resistances) and resistivity calculated, considering physical dimensions. A lithium resistivity of 0.16 Ω μm was maintained for more than a week. This PVD multilayer exonerates the use of chemical vapour deposition (CVD), glove-box chambers and sample manipulation between them, significantly reducing the fabrication cost, since battery and its encapsulation are fabricated in the same PVD chamber.

Department of the Navy Supporting Data for Fiscal Year 1983 Budget Estimates Descriptive Summaries Submitted to Congress February 1982. Research, Development, Test and Evaluation, Navy. Book 2 of 3. Tactical Programs.

DTIC Science & Technology

1982-02-01

control unit will detect and classify submerged submarins transiting within PJ The EnCAPsulated pedo augments air, surface and submarine anti...vidicon (date link video enhancement). Conduct Operational Test and Evaluation. Complete Large Scale Integration Receiver-Decoder improvement. Continue...analysis, and data link video enhancement focusing on application of a new silicon vidicon was continued; data link improvements such as adaptive null

Silicone Liner-Free Pressure Sensitive Adhesive Labels

NASA Astrophysics Data System (ADS)

Empereur, Johanne; Chaussy, Didier; Belgacem, Mohamed Naceur

2008-08-01

Pressure sensitive adhesives (PSA) were microencapsulated using simple and complex coacervation and aminoplaste. The microcapsules thus prepared were characterized by FTIR spectroscopy, particle size distribution, rheological behavior and peeling tests. The microcapsules were isolated and found to be out of sticky indicating that the PSAs were indeed encapsulated. The prepared suspensions were deposited at the surface of a paper sheets and the dried labels were then pressed against each other. The ensuing complex was then characterized in terms of peeling forces and showed that the encapsulation using aminoplaste technique of a commercial PSA yielded peel energy of 170 J/m2, which constitutes the recovering of about 68% of the adhesive power of the original non encapsulated PSA.

Crystalline silicon carbide nanoparticles encapsulated in branched wavelike carbon nanotubes: synthesis and optical properties.

PubMed

Xi, Guangcheng; Yu, Shijun; Zhang, Rui; Zhang, Meng; Ma, Dekun; Qian, Yitai

2005-07-14

A novel nanostructure, cubic silicon carbide (3C-SiC) nanoparticles encapsulated in branched wavelike carbon nanotubes have been prepared by a reaction of 1,2-dimenthoxyethane (CH3OCH2CH2OCH3), SiCl4, and Mg in an autoclave at 600 degrees C. According to X-ray powder diffraction, the products are composed of 3C-SiC and carbon. TEM and HRTEM images show that the as-synthesized products are composed of 3C-SiC nanoparticles encapsulated in branched carbon nanotubes with wavelike walls. The diameter of the 3C-SiC cores is approximately 20-40 nm and the thickness of the carbon shells is about 3-5 nm. In Raman scattering spectroscopy, both the TO (Gamma) phonon line and the LO (Gamma) phonon line have red shifts about 6 cm(-1) relative to that for the bulk 3C-SiC. The photoluminescence (PL) spectrum shows that there are two emission peaks: blue light emission (431 nm) and violet light emission (414 nm). A sequential deposition growth process (with cores as the templates for the shells) for the nanostructure was proposed.

Parylene-on-oil packaging for long-term implantable pressure sensors.

PubMed

Shapero, Aubrey M; Liu, Yang; Tai, Yu-Chong

2016-08-01

This paper reports and analyzes the feasibility study of a parylene-on-oil encapsulation packaging method of pressure sensors targeted for long-term implantation. Commercial barometric digital-output pressure sensors are enclosed in silicone oil and then encapsulated in situ with parylene-C or -D (PA-C, PA-D) chemical vapor deposition. Experimentally, sensors encapsulated with 30,000 cSt silicone oil and 27 μm PA-D show good performance for 6 weeks in 77 °C saline with >99 % of original sensitivity, corresponding to an extrapolated lifetime of around 21 months in 37 °C saline. This work shows that, with proper designs, such a packaging method can preserve the original pressure sensor sensitivity without offset, validated throughout accelerated lifetime tests. In experiments, wires on the prototypes are used for external electronics but it is found that they contributed to early failures, which would be absent in real wireless versions, indicating a potential for even longer lifetimes. Finally, a verified model is presented to predict the pressure sensor sensitivity of parylene-on-oil packaging with and without the presence of a bubble in the oil.

Smallest fullerene-like silicon cage stabilized by a V(2) unit.

PubMed

Xu, Hong-Guang; Kong, Xiang-Yu; Deng, Xiao-Jiao; Zhang, Zeng-Guang; Zheng, Wei-Jun

2014-01-14

We conducted a combined anion photoelectron spectroscopy and density functional theory study on V2Si20 cluster. Our results show that the V2Si20 cluster has an elongated dodecahedron cage structure with a V2 unit encapsulated inside the cage. It is the smallest fullerene-like silicon cage and can be used as building block to make cluster-assembled materials, such as pearl-chain style nanowires.

Smallest fullerene-like silicon cage stabilized by a V2 unit

NASA Astrophysics Data System (ADS)

Xu, Hong-Guang; Kong, Xiang-Yu; Deng, Xiao-Jiao; Zhang, Zeng-Guang; Zheng, Wei-Jun

2014-01-01

We conducted a combined anion photoelectron spectroscopy and density functional theory study on V2Si20 cluster. Our results show that the V2Si20 cluster has an elongated dodecahedron cage structure with a V2 unit encapsulated inside the cage. It is the smallest fullerene-like silicon cage and can be used as building block to make cluster-assembled materials, such as pearl-chain style nanowires.

A holistic view of crystalline silicon module reliability

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

Hanoka, J.I.

1995-11-01

Several aspects of module reliability are discussed, particularly with reference to the encapsulant and its interaction with the metallization and interconnection of a module. A need to look at the module as a whole single unit is stressed. Also, the issue of a slight light degradation effect in crystalline silicon cells is discussed. A model for this is mentioned and it may well be that polycrystalline cells with dislocations may have an advantage.

Monolithic amorphous silicon modules on continuous polymer substrate

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

Grimmer, D.P.

This report examines manufacturing monolithic amorphous silicon modules on a continuous polymer substrate. Module production costs can be reduced by increasing module performance, expanding production, and improving and modifying production processes. Material costs can be reduced by developing processes that use a 1-mil polyimide substrate and multilayers of low-cost material for the front encapsulant. Research to speed up a-Si and ZnO deposition rates is needed to improve throughputs. To keep throughput rates compatible with depositions, multibeam fiber optic delivery systems for laser scribing can be used. However, mechanical scribing systems promise even higher throughputs. Tandem cells and production experience canmore » increase device efficiency and stability. Two alternative manufacturing processes are described: (1) wet etching and sheet handling and (2) wet etching and roll-to-roll fabrication.« less

Combination of sorption properties of polydimethylsiloxane and solid-phase extraction sorbents in a single composite material for the passive sampling of polar and apolar pesticides in water.

PubMed

Martin, Alexis; Margoum, Christelle; Coquery, Marina; Randon, Jérôme

2016-10-01

Passive sampling techniques have been developed as an alternative method for in situ integrative monitoring of trace levels of neutral pesticides in environmental waters. The objective of this work was to develop a new receiving phase for pesticides with a wide range of polarities in a single step. We describe the development of three new composite silicone rubbers, combining polydimethylsiloxane mechanical and sorption properties with solid-phase extraction sorbents, prepared as a receiving phase for passive sampling. A composite silicone rubber composed of polydimethylsiloxane/poly(divinylbenzene-co-N-vinylpyrrolidone) was selected by batch experiments for its high sorption properties for pesticides with octanol-water partition coefficients ranging from 2.3 to 5.5. We named this composite material "Polar/Apolar Composite Silicone Rubber". A structural study by scanning electron microscopy confirmed the homogeneous dispersion of the sorbent particles and the encapsulation of particles within the polydimethylsiloxane matrix. We also demonstrate that this composite material is resistant to common solvents used for the back-extraction of analytes and has a maximal resistance temperature of 350°C. Therefore, the characteristics of the "Polar/Apolar Composite Silicone Rubber" meet most of the criteria for use as a receiving phase for the passive sampling of pesticides. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Al+Si Interface Optical Properties Obtained in the Si Solar Cell Configuration

DOE PAGES

Subedi, Indra; Silverman, Timothy J.; Deceglie, Michael G.; ...

2017-10-18

Al is a commonly used material for rear side metallization in commercial silicon (Si) wafer solar cells. In this study, through-the-silicon spectroscopic ellipsometry is used in a test sample to measure Al+Si interface optical properties like those in Si wafer solar cells. Two different spectroscopic ellipsometers are used for measurement of Al+Si interface optical properties over the 1128-2500 nm wavelength range. For validation, the measured interface optical properties are used in a ray tracing simulation over the 300-2500 nm wavelength range for an encapsulated Si solar cell having random pyramidal texture. The ray tracing model matches well with the measuredmore » total reflectance at normal incidence of a commercially available Si module. The Al+Si optical properties presented here enable quantitative assessment of major irradiance/current flux losses arising from reflection and parasitic absorption in encapsulated Si solar cells.« less

Crystalline-silicon reliability lessons for thin-film modules

NASA Technical Reports Server (NTRS)

Ross, R. G., Jr.

1985-01-01

The reliability of crystalline silicon modules has been brought to a high level with lifetimes approaching 20 years, and excellent industry credibility and user satisfaction. The transition from crystalline modules to thin film modules is comparable to the transition from discrete transistors to integrated circuits. New cell materials and monolithic structures will require new device processing techniques, but the package function and design will evolve to a lesser extent. Although there will be new encapsulants optimized to take advantage of the mechanical flexibility and low temperature processing features of thin films, the reliability and life degradation stresses and mechanisms will remain mostly unchanged. Key reliability technologies in common between crystalline and thin film modules include hot spot heating, galvanic and electrochemical corrosion, hail impact stresses, glass breakage, mechanical fatigue, photothermal degradation of encapsulants, operating temperature, moisture sorption, circuit design strategies, product safety issues, and the process required to achieve a reliable product from a laboratory prototype.

Al+Si Interface Optical Properties Obtained in the Si Solar Cell Configuration

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

Subedi, Indra; Silverman, Timothy J.; Deceglie, Michael G.

Al is a commonly used material for rear side metallization in commercial silicon (Si) wafer solar cells. In this study, through-the-silicon spectroscopic ellipsometry is used in a test sample to measure Al+Si interface optical properties like those in Si wafer solar cells. Two different spectroscopic ellipsometers are used for measurement of Al+Si interface optical properties over the 1128-2500 nm wavelength range. For validation, the measured interface optical properties are used in a ray tracing simulation over the 300-2500 nm wavelength range for an encapsulated Si solar cell having random pyramidal texture. The ray tracing model matches well with the measuredmore » total reflectance at normal incidence of a commercially available Si module. The Al+Si optical properties presented here enable quantitative assessment of major irradiance/current flux losses arising from reflection and parasitic absorption in encapsulated Si solar cells.« less

In vitro and in vivo evaluation of ultrananocrystalline diamond as an encapsulation layer for implantable microchips.

PubMed

Chen, Ying-Chieh; Tsai, Che-Yao; Lee, Chi-Young; Lin, I-Nan

2014-05-01

Thin ultrananocrystalline diamond (UNCD) films were evaluated for use as hermetic and bioinert encapsulating coatings for implantable microchips, where the reaction to UNCD in vitro and in vivo tissue was investigated. Leakage current tests showed that depositing UNCD coatings, which were conformally grown in (1% H2) Ar/CH4 plasma, on microchips rendered the surface electrochemically inactive, i.e. with a very low leakage current density (2.8×10(-5)Acm(-2) at -1V and 1.9×10(-3)Acm(-2) at ±5V) ex vivo. The impact of UNCD with different surface modifications on the growth and activation of macrophages was compared to that of standard-grade polystyrene. Macrophages attached to oxygen-terminated UNCD films down-regulated their production of cytokines and chemokines. Moreover, with UNCD-coated microchips, which were implanted subcutaneously into BALB/c mice for up to 3months, the tissue reaction and capsule formation was significantly decreased compared to the medical-grade titanium alloy Ti-6Al-4V and bare silicon. Additionally, the leakage current density, elicited by electrochemical activity, on silicon chips encapsulated in oxygen-terminated UNCD coatings remained at the low level of 2.5×10(-3)Acm(-2) at 5V for up to 3months in vivo, which is half the level of those encapsulated in hydrogen-terminated UNCD coatings. Thus, controlling the surface properties of UNCDs makes it possible to manipulate the in vivo functionality and stability of implantable devices so as to reduce the host inflammatory response following implantation. These observations suggest that oxygen-terminated UNCDs are promising candidates for use as encapsulating coatings for implantable microelectronic devices. Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Method of bonding silver to glass and mirrors produced according to this method

DOEpatents

Pitts, J.R.; Thomas, T.M.; Czanderna, A.W.

1984-07-31

A method for adhering silver to a glass substrate for producing mirrors includes attaining a silicon enriched substrate surface by reducing the oxygen therein in a vacuum and then vacuum depositing a silver layer onto the silicon enriched surface. The silicon enrichment can be attained by electron beam bombardment, ion beam bombardment, or neutral beam bombardment. It can also be attained by depositing a metal, such as aluminum, on the substrate surface, allowing the metal to oxidize by pulling oxygen from the substrate surface, thereby leaving a silicon enriched surface, and then etching or eroding the metal oxide layer away to expose the silicon enriched surface. Ultraviolet rays can be used to maintain dangling silicon bonds on the enriched surface until covalent bonding with the silver can occur. This disclosure also includes encapsulated mirrors with diffusion layers built therein. One of these mirrors is assembled on a polymer substrate.

Method of bonding silver to glass and mirrors produced according to this method

DOEpatents

Pitts, John R.; Thomas, Terence M.; Czanderna, Alvin W.

1985-01-01

A method for adhering silver to a glass substrate for producing mirrors includes attaining a silicon enriched substrate surface by reducing the oxygen therein in a vacuum and then vacuum depositing a silver layer onto the silicon enriched surface. The silicon enrichment can be attained by electron beam bombardment, ion beam bombardment, or neutral beam bombardment. It can also be attained by depositing a metal, such as aluminum, on the substrate surface, allowing the metal to oxidize by pulling oxygen from the substrate surface, thereby leaving a silicon enriched surface, and then etching or eroding the metal oxide layer away to expose the silicon enriched surface. Ultraviolet rays can be used to maintain dangling silicon bonds on the enriched surface until covalent bonding with the silver can occur. This disclosure also includes encapsulated mirrors with diffusion layers built therein. One of these mirrors is assembled on a polymer substrate.

Amorphous silicon photovoltaic manufacturing technology, phase 2A

NASA Astrophysics Data System (ADS)

Duran, G.; Mackamul, K.; Metcalf, D.

1995-01-01

Utility Power Group (UPG), and its lower-tier subcontractor, Advanced Photovoltaic Systems, Inc. (APS) have conducted efforts in developing their manufacturing lines. UPG has focused on the automation of encapsulation and termination processes developed in Phase 1. APS has focused on completion of the encapsulation and module design tasks, while continuing the process and quality control and automation projects. The goal is to produce 55 watt (stabilized) EP50 modules in a new facility. In the APS Trenton EUREKA manufacturing facility, APS has: (1) Developed high throughput lamination procedures; (2) Optimized existing module designs; (3) Developed new module designs for architectural applications; (4) Developed enhanced deposition parameter control; (5) Designed equipment required to manufacture new EUREKA modules developed during Phase II; (6) Improved uniformity of thin-film materials deposition; and (7) Improved the stabilized power output of the APS EP50 EUREKA module to 55 watts. In the APS Fairfield EUREKA manufacturing facility, APS has: (1) Introduced the new products developed under Phase 1 into the APS Fairfield EUREKA module production line; (2) Increased the extent of automation in the production line; (3) Introduced Statistical Process Control to the module production line; and (4) Transferred-progress made in the APS Trenton facility into the APS Fairfield facility.

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

Atmaram, G.H.; Ventre, G.G.; Maytrott, C.W.

This study evaluates the long-term effects of outdoor exposure and high voltage operation on the performance and reliability of flat-plate crystalline silicon photovoltaic modules. The photovoltaic modules selected for this study were employed in the arrays of grid-connected residential photovoltaic prototype systems for over ten years at the Southeast Regional Experiment Station (SE RES) in Cape Canaveral, Florida. The modules included Mobil Ra-180 EFG ribbon silicon modules, Photowatt MU-7061 and ARCO 16-2000 single-crystal silicon modules with round cells. The Mobil and Photowatt modules were Block 5 generation, while the ARCO modules were Block 4 generation type. In all three typesmore » of photovoltaic modules (Mobil, Photowatt and ARCO), no significant power loss occurred over more than ten years of outdoor operation in the warm, humid and ocean-salt environments of coastal Florida. However, the wet insulation resistance values of a majority of the modules in all three types were lower than the values recommended in IEEE Standard 1262. This indicates potential future safety, reliability and lifetime related problems. The visual defects were more pronounced in the ARCO modules, which were manufactured in 1980 than in the Mobil and Photowatt modules, both of which were fabricated in 1983. The ARCO modules showed significant damage to the back surface tedlar in the form of tearing of the tedlar. All of the Mobil and most of the ARCO modules showed significant browning of the encapsulant, while only about half of the Photowatt modules showed significant encapsulant browning. The encapsulant discoloration generally did not appear to have any effect on the modules` power generation.« less

Design and fabrication of solar cell modules

NASA Technical Reports Server (NTRS)

Shaughnessy, T. P.

1978-01-01

A program conducted for design, fabrication and evaluation of twelve silicon solar cell modules is described. The purpose of the program was to develop a module design consistent with the requirements and objectives of JPL specification and to also incorporate elements of new technologies under development to meet LSSA Project goals. Module development emphasized preparation of a technically and economically competitive design based upon utilization of ion implanted solar cells and a glass encapsulation system. The modules fabricated, tested and delivered were of nominal 2 X 2 foot dimensions and 20 watt minimum rating. Basic design, design rationale, performance and results of environmental testing are described.

Smallest fullerene-like silicon cage stabilized by a V{sub 2} unit

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

Xu, Hong-Guang, E-mail: xuhong@iccas.ac.cn, E-mail: zhengwj@iccas.ac.cn; Kong, Xiang-Yu; Deng, Xiao-Jiao

We conducted a combined anion photoelectron spectroscopy and density functional theory study on V{sub 2}Si{sub 20} cluster. Our results show that the V{sub 2}Si{sub 20} cluster has an elongated dodecahedron cage structure with a V{sub 2} unit encapsulated inside the cage. It is the smallest fullerene-like silicon cage and can be used as building block to make cluster-assembled materials, such as pearl-chain style nanowires.

In vivo biocompatibility of boron doped and nitrogen included conductive-diamond for use in medical implants.

PubMed

Garrett, David J; Saunders, Alexia L; McGowan, Ceara; Specks, Joscha; Ganesan, Kumaravelu; Meffin, Hamish; Williams, Richard A; Nayagam, David A X

2016-01-01

Recently, there has been interest in investigating diamond as a material for use in biomedical implants. Diamond can be rendered electrically conducting by doping with boron or nitrogen. This has led to inclusion of boron doped and nitrogen included diamond elements as electrodes and/or feedthroughs for medical implants. As these conductive device elements are not encapsulated, there is a need to establish their clinical safety for use in implants. This article compares the biocompatibility of electrically conducting boron doped diamond (BDD) and nitrogen included diamond films and electrically insulating poly crystalline diamond films against a silicone negative control and a BDD sample treated with stannous octoate as a positive control. Samples were surgically implanted into the back muscle of a guinea pig for a period of 4-15 weeks, excised and the implant site sectioned and submitted for histological analysis. All forms of diamond exhibited a similar or lower thickness of fibrotic tissue encapsulating compared to the silicone negative control samples. All forms of diamond exhibited similar or lower levels of acute, chronic inflammatory, and foreign body responses compared to the silicone negative control indicating that the materials are well tolerated in vivo. © 2015 Wiley Periodicals, Inc.

A pomegranate-inspired nanoscale design for large-volume-change lithium battery anodes

NASA Astrophysics Data System (ADS)

Liu, Nian; Lu, Zhenda; Zhao, Jie; McDowell, Matthew T.; Lee, Hyun-Wook; Zhao, Wenting; Cui, Yi

2014-03-01

Silicon is an attractive material for anodes in energy storage devices, because it has ten times the theoretical capacity of its state-of-the-art carbonaceous counterpart. Silicon anodes can be used both in traditional lithium-ion batteries and in more recent Li-O2 and Li-S batteries as a replacement for the dendrite-forming lithium metal anodes. The main challenges associated with silicon anodes are structural degradation and instability of the solid-electrolyte interphase caused by the large volume change (~300%) during cycling, the occurrence of side reactions with the electrolyte, and the low volumetric capacity when the material size is reduced to a nanometre scale. Here, we propose a hierarchical structured silicon anode that tackles all three of these problems. Our design is inspired by the structure of a pomegranate, where single silicon nanoparticles are encapsulated by a conductive carbon layer that leaves enough room for expansion and contraction following lithiation and delithiation. An ensemble of these hybrid nanoparticles is then encapsulated by a thicker carbon layer in micrometre-size pouches to act as an electrolyte barrier. As a result of this hierarchical arrangement, the solid-electrolyte interphase remains stable and spatially confined, resulting in superior cyclability (97% capacity retention after 1,000 cycles). In addition, the microstructures lower the electrode-electrolyte contact area, resulting in high Coulombic efficiency (99.87%) and volumetric capacity (1,270 mAh cm-3), and the cycling remains stable even when the areal capacity is increased to the level of commercial lithium-ion batteries (3.7 mAh cm-2).

The effect of material matching on the stress-induced power degradation for light-redirecting-ribbon-based silicon photovoltaic modules

NASA Astrophysics Data System (ADS)

Gou, X. F.; Zhuang, H.; Zhu, J.; Li, X. Y.

2018-01-01

Light redirecting ribbons (LRR) have recently been adopted in crystalline silicon modules in PV industry. The introduction of this LRR may bring additional stress at the boundary of the busbar/wafer contact, which may probably lead to higher power loss after aging. The thermal cycle and electroluminescence (EL) test are employed in this work to investigate this stress-induced power degradation for LRR-based crystalline silicon modules. The obtained results demonstrate that with increase in the thickness of the EVA encapsulant or the decrease in the thickness of the LRR, the power degradation induced by stress can be effectively diminished.

A Temperature-Monitoring Vaginal Ring for Measuring Adherence

PubMed Central

Boyd, Peter; Desjardins, Delphine; Kumar, Sandeep; Fetherston, Susan M.; Le-Grand, Roger; Dereuddre-Bosquet, Nathalie; Helgadóttir, Berglind; Bjarnason, Ásgeir; Narasimhan, Manjula; Malcolm, R. Karl

2015-01-01

Background Product adherence is a pivotal issue in the development of effective vaginal microbicides to reduce sexual transmission of HIV. To date, the six Phase III studies of vaginal gel products have relied primarily on self-reporting of adherence. Accurate and reliable methods for monitoring user adherence to microbicide-releasing vaginal rings have yet to be established. Methods A silicone elastomer vaginal ring prototype containing an embedded, miniature temperature logger has been developed and tested in vitro and in cynomolgus macaques for its potential to continuously monitor environmental temperature and accurately determine episodes of ring insertion and removal. Results In vitro studies demonstrated that DST nano-T temperature loggers encapsulated in medical grade silicone elastomer were able to accurately and continuously measure environmental temperature. The devices responded quickly to temperature changes despite being embedded in different thickness of silicone elastomer. Prototype vaginal rings measured higher temperatures compared with a subcutaneously implanted device, showed high sensitivity to diurnal fluctuations in vaginal temperature, and accurately detected periods of ring removal when tested in macaques. Conclusions Vaginal rings containing embedded temperature loggers may be useful in the assessment of product adherence in late-stage clinical trials. PMID:25965956

High-Performance and Omnidirectional Thin-Film Amorphous Silicon Solar Cell Modules Achieved by 3D Geometry Design.

PubMed

Yu, Dongliang; Yin, Min; Lu, Linfeng; Zhang, Hanzhong; Chen, Xiaoyuan; Zhu, Xufei; Che, Jianfei; Li, Dongdong

2015-11-01

High-performance thin-film hydrogenated amorphous silicon solar cells are achieved by combining macroscale 3D tubular substrates and nanoscaled 3D cone-like antireflective films. The tubular geometry delivers a series of advantages for large-scale deployment of photovoltaics, such as omnidirectional performance, easier encapsulation, decreased wind resistance, and easy integration with a second device inside the glass tube. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Experimental evaluation of the Battelle accelerated test design for the solar array at Mead, Nebraska

NASA Technical Reports Server (NTRS)

Frickland, P. O.; Repar, J.

1982-01-01

A previously developed test design for accelerated aging of photovoltaic modules was experimentally evaluated. The studies included a review of relevant field experience, environmental chamber cycling of full size modules, and electrical and physical evaluation of the effects of accelerated aging during and after the tests. The test results indicated that thermally induced fatigue of the interconnects was the primary mode of module failure as measured by normalized power output. No chemical change in the silicone encapsulant was detectable after 360 test cycles.

Fatigue degradation and electric recovery in Silicon solar cells embedded in photovoltaic modules

PubMed Central

Paggi, Marco; Berardone, Irene; Infuso, Andrea; Corrado, Mauro

2014-01-01

Cracking in Silicon solar cells is an important factor for the electrical power-loss of photovoltaic modules. Simple geometrical criteria identifying the amount of inactive cell areas depending on the position of cracks with respect to the main electric conductors have been proposed in the literature to predict worst case scenarios. Here we present an experimental study based on the electroluminescence (EL) technique showing that crack propagation in monocrystalline Silicon cells embedded in photovoltaic (PV) modules is a much more complex phenomenon. In spite of the very brittle nature of Silicon, due to the action of the encapsulating polymer and residual thermo-elastic stresses, cracked regions can recover the electric conductivity during mechanical unloading due to crack closure. During cyclic bending, fatigue degradation is reported. This pinpoints the importance of reducing cyclic stresses caused by vibrations due to transportation and use, in order to limit the effect of cracking in Silicon cells. PMID:24675974

Localized heating and bonding technique for MEMS packaging

NASA Astrophysics Data System (ADS)

Cheng, Yu-Ting

Localized heating and bonding techniques have been developed for hermetic and vacuum packaging of MEMS devices, including silicon-to-glass fusion, silicon-gold eutectic, and silicon-to-glass bonding using PSG, indium, aluminum, and aluminum/silicon alloy as the intermediate layer. Line shaped phosphorus-doped polysilicon or gold films are used as resistive microheaters to provide enough thermal energy for bonding. The bonding processes are conducted in the common environment of room temperature and atmospheric pressure and can achieve bonding strength comparable to the fracture toughness of bulk silicon in less than 10 minutes. About 5 watts of input power is needed for localized bonding which can seal a 500 x 500 mum2 area. The total input power is determined by the thermal properties of bonding materials, including the heat capacity and latent heat. Two important bonding results are obtained: (1) The surface step created by the electrical interconnect line can be planarized by reflowing the metal solder. (2) Small applied pressure, less than 1MPa, for intimate contact reduces mechanical damage to the device substrate. This new class of bonding technology has potential applications for MEMS fabrication and packaging that require low temperature processing at the wafer level, excellent bonding strength and hermetic sealing characteristics. A hermetic package based on localized aluminum/silicon-to-glass bonding has been successfully fabricated. Less than 0.2 MPa contact pressure with 46mA input current for two parallel 3.5mum wide polysilicon on-chip microheaters can create as high as 700°C bonding temperature and achieve a strong and reliable bond in 7.5 minutes. Accelerated testing in an autoclave shows some packages survive more than 450 hours under 3 atm, 100%RH and 128°C. Premature failure has been attributed to some unbonded regions on the failed samples. The bonding yield and reliability have been improved by increasing bonding time and applied pressure. Finally, vacuum encapsulation of folded-beam comb-drive mu-resonators used as pressure monitors has been demonstrated using localized aluminum/silicon-to-glass bonding. With 3.4 watt heating power, ˜0.2MPa applied contact pressure, and 90 minutes wait time before bonding, vacuum encapsulation can be achieved with the same vacuum level as the packaging environment which is about 25 mtorr. Metal coating used as diffusion barrier and a longer wait time before bonding are used to improve the vacuum level of the package. Long-term measurement of the Q of un-annealed vacuum-packaged mu-resonators, illustrates stable operation after 19 weeks.

Amorphous TiO2 Shells: A Vital Elastic Buffering Layer on Silicon Nanoparticles for High-Performance and Safe Lithium Storage.

PubMed

Yang, Jianping; Wang, Yunxiao; Li, Wei; Wang, Lianjun; Fan, Yuchi; Jiang, Wan; Luo, Wei; Wang, Yang; Kong, Biao; Selomulya, Cordelia; Liu, Hua Kun; Dou, Shi Xue; Zhao, Dongyuan

2017-12-01

Smart surface coatings of silicon (Si) nanoparticles are shown to be good examples for dramatically improving the cyclability of lithium-ion batteries. Most coating materials, however, face significant challenges, including a low initial Coulombic efficiency, tedious processing, and safety assessment. In this study, a facile sol-gel strategy is demonstrated to synthesize commercial Si nanoparticles encapsulated by amorphous titanium oxide (TiO 2 ), with core-shell structures, which show greatly superior electrochemical performance and high-safety lithium storage. The amorphous TiO 2 shell (≈3 nm) shows elastic behavior during lithium discharging and charging processes, maintaining high structural integrity. Interestingly, it is found that the amorphous TiO 2 shells offer superior buffering properties compared to crystalline TiO 2 layers for unprecedented cycling stability. Moreover, accelerating rate calorimetry testing reveals that the TiO 2 -encapsulated Si nanoparticles are safer than conventional carbon-coated Si-based anodes. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Digital microfluidics and delivery of molecular payloads with magnetic porous silicon chaperones.

PubMed

Dorvee, Jason R; Sailor, Michael J; Miskelly, Gordon M

2008-02-14

Digital microfluidics involves the manipulation of molecules and materials in discrete packages. This paper reviews our work using amphiphilic magnetic microparticles constructed from porous silicon. An individual porous particle can be used to carry a nanomole or smaller quantities of a reagent, and assemblies of the particles can encapsulate and transport microliter droplets of liquid containing inorganic, organic, or biological molecules. The tracking and identification of each particle can be accomplished with spectral labels that are encoded into the particles during their synthesis. When used to chaperone liquid droplets, the labels can identify the separate droplets prior to mixing and also the combined droplets after mixing. Magnetic iron oxide nanoparticles encapsulated in the porous matrix allow the manipulation of the particles or whole droplet assemblies with a magnetic field, and they also allow heating of the particle's payload by means of an externally applied RF field. Examples of organic, inorganic, and biomolecular addition reactions, catalytic reactions, and thermolysis reactions are described.

The design, fabrication and characterization of fluidic membranes for micro-engines with the aim of frequency lowering

NASA Astrophysics Data System (ADS)

Chutani, R.; Formosa, F.; de Labachelerie, M.; Badel, A.; Lanzetta, F.

2016-12-01

This paper describes the design, microfabrication and linear dynamic characterization of low frequency thick membranes as a potential technological solution for resonant micro-engines, for which classical pistons cannot be used. The proposed structure is called a hybrid fluid-membrane and consists of two thin flexible membranes that encapsulate an incompressible fluid. Lower frequency structures, compared to geometrically equivalent single layer membranes, are thus obtained. Each flexible membrane is based on a composite structure which comprises a silicon planar logarithmic spiral spring embedded in a room temperature vulcanization silicone polymer. Thus, the stiffness and sealing features are dissociated for a better design control. The developed realization and assembly process is demonstrated at the wafer level. The process involves the anodic bonding of multiple stacks of silicon/glass structures, fluid filling and sealing. Various dimensions of hybrid fluid-membranes are successfully fabricated. Their dynamic characterization underlines the agreement between experimental and theoretical results. The results provide the opportunity for the design and fabrication of low frequency membranes to match the dynamics requirements of micro-engines.

MULTI-STAGE DELIVERY NANO-PARTICLE SYSTEMS FOR THERAPEUTIC APPLICATIONS

PubMed Central

Serda, Rita E.; Godin, Biana; Blanco, Elvin; Chiappini, Ciro; Ferrari, Mauro

2010-01-01

Background The daunting task for drug molecules to reach pathological lesions has fueled rapid advances in Nanomedicine. The progressive evolution of nanovectors has led to the development of multi-stage delivery systems aimed at overcoming the numerous obstacles encountered by nanovectors on their journey to the target site. Scope of Review This review summarizes major findings with respect to silicon-based drug delivery vectors for cancer therapeutics and imaging. Based on rational design, well established silicon technologies have been adapted for the fabrication of nanovectors with specific shapes, sizes, and porosities. These vectors are part of a multi-stage delivery system that contains multiple nano-components, each designed to achieve a specific task with the common goal of site-directed delivery of therapeutics. Major Conclusions Quasi-hemispherical and discoidal silicon microparticles are superior to spherical particles with respect to margination in the blood, with particles of different shapes and sizes having unique distributions in vivo. Cellular adhesion and internalization of silicon microparticles is influenced by microparticle shape and surface charge, with the latter dictating binding of serum opsonins. Based on in vitro cell studies, the internalization of porous silicon microparticles by endothelial cells and macrophages is compatible with cellular morphology, intracellular trafficking, mitosis, cell cycle progression, cytokine release, and cell viability. In vivo studies support superior therapeutic efficacy of liposomal encapsulated siRNA when delivered in multi-stage systems compared to free nanoparticles. PMID:20493927

Large area and structured epitaxial graphene produced by confinement controlled sublimation of silicon carbide

PubMed Central

de Heer, Walt A.; Berger, Claire; Ruan, Ming; Sprinkle, Mike; Li, Xuebin; Hu, Yike; Zhang, Baiqian; Hankinson, John; Conrad, Edward

2011-01-01

After the pioneering investigations into graphene-based electronics at Georgia Tech, great strides have been made developing epitaxial graphene on silicon carbide (EG) as a new electronic material. EG has not only demonstrated its potential for large scale applications, it also has become an important material for fundamental two-dimensional electron gas physics. It was long known that graphene mono and multilayers grow on SiC crystals at high temperatures in ultrahigh vacuum. At these temperatures, silicon sublimes from the surface and the carbon rich surface layer transforms to graphene. However the quality of the graphene produced in ultrahigh vacuum is poor due to the high sublimation rates at relatively low temperatures. The Georgia Tech team developed growth methods involving encapsulating the SiC crystals in graphite enclosures, thereby sequestering the evaporated silicon and bringing growth process closer to equilibrium. In this confinement controlled sublimation (CCS) process, very high-quality graphene is grown on both polar faces of the SiC crystals. Since 2003, over 50 publications used CCS grown graphene, where it is known as the “furnace grown” graphene. Graphene multilayers grown on the carbon-terminated face of SiC, using the CCS method, were shown to consist of decoupled high mobility graphene layers. The CCS method is now applied on structured silicon carbide surfaces to produce high mobility nano-patterned graphene structures thereby demonstrating that EG is a viable contender for next-generation electronics. Here we present for the first time the CCS method that outperforms other epitaxial graphene production methods. PMID:21960446

Degradation of Silicone Encapsulants in CPV Optics

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

Cai, Can; Miller, David C.; Tappan, Ian A.

High efficiency multijunction solar cells in terrestrial concentrator photovoltaic (CPV) modules are becoming an increasingly cost effective and viable option in utility scale power generation. As with other utility scale photovoltaics, CPV modules need to guarantee operational lifetimes of at least 25 years. The reliability of optical elements in CPV modules poses a unique materials challenge due to the increased UV irradiance and enhanced temperature cycling associated with concentrated solar flux. The polymeric and thin film materials used in the optical elements are especially susceptible to UV damage, diurnal temperature cycling and active chemical species from the environment. We usedmore » fracture mechanics approaches to study the degradation modes including: the adhesion between the encapsulant and the cell or secondary optical element; and the cohesion of the encapsulant itself. Understanding the underlying mechanisms of materials degradation under elevated stress conditions is critical for commercialization of CPV technology and can offer unique insights into degradation modes in similar encapsulants used in other photovoltaic modules.« less

Degradation of Silicone Encapsulants in CPV Optics: Preprint

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

Miller, David C.; Tappan, Ian A.; Cai, Can

High efficiency multijunction solar cells in terrestrial concentrator photovoltaic (CPV) modules are becoming an increasingly cost effective and viable option in utility scale power generation. As with other utility scale photovoltaics, CPV modules need to guarantee operational lifetimes of at least 25 years. The reliability of optical elements in CPV modules poses a unique materials challenge due to the increased UV irradiance and enhanced temperature cycling associated with concentrated solar flux. The polymeric and thin film materials used in the optical elements are especially susceptible to UV damage, diurnal temperature cycling and active chemical species from the environment. We usedmore » fracture mechanics approaches to study the degradation modes including: the adhesion between the encapsulant and the cell or secondary optical element; and the cohesion of the encapsulant itself. Understanding the underlying mechanisms of materials degradation under elevated stress conditions is critical for commercialization of CPV technology and can offer unique insights into degradation modes in similar encapsulants used in other photovoltaic modules.« less

Production development of organic nonflammable spacecraft potting, encapsulating and conformal coating compounds. Volume 1: Discussion, figures, and references

NASA Technical Reports Server (NTRS)

Lieberman, S. L.

1974-01-01

Based upon extensive contacts with vendors, a broad array of non-flammable polymeric specie, and additives generally noted to have flame retarding properties, were considered. The following polymeric matrices were examined: modified silicone and fluorosilicone RTV's polyesters, epoxies, urethanes, and epoxy-urethanes. Optimization of formulations to obtain a suitable balance between the various properties and flammability resistance led to the final selection of a silicone RTV/additive-loaded compound which meets almost all program requirements. The very low valued properties found are within a realistic level of design toleration. Complete formulation, processing, and test data is provided for this compound, EPOCAST 87517-A/B, and the other formulations prepared by the project. Details of those test methods are presented along with procedures utilized in the program. In addition, a description of the special flammability facility previously designed and then modified for this program is also presented.

Encapsulated Islet Transplantation: Where Do We Stand?

PubMed

Vaithilingam, Vijayaganapathy; Bal, Sumeet; Tuch, Bernard E

2017-01-01

Transplantation of pancreatic islets encapsulated within immuno-protective microcapsules is a strategy that has the potential to overcome graft rejection without the need for toxic immunosuppressive medication. However, despite promising preclinical studies, clinical trials using encapsulated islets have lacked long-term efficacy, and although generally considered clinically safe, have not been encouraging overall. One of the major factors limiting the long-term function of encapsulated islets is the host's immunological reaction to the transplanted graft which is often manifested as pericapsular fibrotic overgrowth (PFO). PFO forms a barrier on the capsule surface that prevents the ingress of oxygen and nutrients leading to islet cell starvation, hypoxia and death. The mechanism of PFO formation is still not elucidated fully and studies using a pig model have tried to understand the host immune response to empty alginate microcapsules. In this review, the varied strategies to overcome or reduce PFO are discussed, including alginate purification, altering microcapsule geometry, modifying alginate chemical composition, co-encapsulation with immunomodulatory cells, administration of pharmacological agents, and alternative transplantation sites. Nanoencapsulation technologies, such as conformal and layer-by-layer coating technologies, as well as nanofiber, thin-film nanoporous devices, and silicone based NanoGland devices are also addressed. Finally, this review outlines recent progress in imaging technologies to track encapsulated cells, as well as promising perspectives concerning the production of insulin-producing cells from stem cells for encapsulation.

Passivation coating for flexible substrate mirrors

DOEpatents

Tracy, C. Edwin; Benson, David K.

1990-01-01

A protective diffusion barrier for metalized mirror structures is provided by a layer or coating of silicon nitride which is a very dense, transparent, dielectric material that is impervious to water, alkali, and other impurities and corrosive substances that typically attack the metal layers of mirrors and cause degradation of the mirrors' reflectivity. The silicon nitride layer can be deposited on the substrate before metal deposition thereon to stabilize the metal/substrate interface, and it can be deposited over the metal to encapsulate it and protect the metal from corrosion or other degradation. Mirrors coated with silicon nitride according to this invention can also be used as front surface mirrors. Also, the silver or other reflective metal layer on mirrors comprising thin, lightweight, flexible substrates of metal or polymer sheets coated with glassy layers can be protected with silicon nitride according to this invention.

High-resolution and Fast-response Fiber-optic Temperature Sensor Using Silicon Fabry-Perot Cavity

DTIC Science & Technology

2015-03-23

silver diaphragm,” Opt. Lett. 37(9), 1505–1507 (2012). 18. I. M. White and X. D. Fan , “On the performance quantification of resonant refractive index...to the response time, the package of a FBG with a copper tube encapsulation can greatly reduce the response time of the sensor from several seconds...head shown in Fig. 1(b) are described in Fig. 2. The fabrication started with bonding a 200-µm-thick double-side-polished silicon wafer on top of

Sol-gel method for encapsulating molecules

DOEpatents

Brinker, C. Jeffrey; Ashley, Carol S.; Bhatia, Rimple; Singh, Anup K.

2002-01-01

A method for encapsulating organic molecules, and in particular, biomolecules using sol-gel chemistry. A silica sol is prepared from an aqueous alkali metal silicate solution, such as a mixture of silicon dioxide and sodium or potassium oxide in water. The pH is adjusted to a suitably low value to stabilize the sol by minimizing the rate of siloxane condensation, thereby allowing storage stability of the sol prior to gelation. The organic molecules, generally in solution, is then added with the organic molecules being encapsulated in the sol matrix. After aging, either a thin film can be prepared or a gel can be formed with the encapsulated molecules. Depending upon the acid used, pH, and other processing conditions, the gelation time can be from one minute up to several days. In the method of the present invention, no alcohols are generated as by-products during the sol-gel and encapsulation steps. The organic molecules can be added at any desired pH value, where the pH value is generally chosen to achieve the desired reactivity of the organic molecules. The method of the present invention thereby presents a sufficiently mild encapsulation method to retain a significant portion of the activity of the biomolecules, compared with the activity of the biomolecules in free solution.

The effect of nanocrystalline silicon host on magnetic properties of encapsulated iron oxide nanoparticles.

PubMed

Granitzer, P; Rumpf, K; Gonzalez-Rodriguez, R; Coffer, J L; Reissner, M

2015-12-21

The purpose of this work is a detailed comparison of the fundamental magnetic properties of nanocomposite systems consisting of Fe3O4 nanoparticle-loaded porous silicon as well as silicon nanotubes. Such composite structures are of potential merit in the area of magnetically guided drug delivery. For magnetic systems to be utilized in biomedical applications, there are certain magnetic properties that must be fulfilled. Therefore magnetic properties of embedded Fe3O4-nanoparticles in these nanostructured silicon host matrices, porous silicon and silicon nanotubes, are investigated. Temperature-dependent magnetic investigations have been carried out for four types of iron oxide particle sizes (4, 5, 8 and 10 nm). The silicon host, in interplay with the iron oxide nanoparticle size, plays a sensitive role. It is shown that Fe3O4 loaded porous silicon and SiNTs differ significantly in their magnetic behavior, especially the transition between superparamagnetic behavior and blocked state, due to host morphology-dependent magnetic interactions. Importantly, it is found that all investigated samples meet the magnetic precondition of possible biomedical applications of exhibiting a negligible magnetic remanence at room temperature.

Plasma jet printing of electronic materials on flexible and nonconformal objects.

PubMed

Gandhiraman, Ram P; Jayan, Vivek; Han, Jin-Woo; Chen, Bin; Koehne, Jessica E; Meyyappan, M

2014-12-10

We present a novel approach for the room-temperature fabrication of conductive traces and their subsequent site-selective dielectric encapsulation for use in flexible electronics. We have developed an aerosol-assisted atmospheric pressure plasma-based deposition process for efficiently depositing materials on flexible substrates. Silver nanowire conductive traces and silicon dioxide dielectric coatings for encapsulation were deposited using this approach as a demonstration. The paper substrate with silver nanowires exhibited a very low change in resistance upon 50 cycles of systematic deformation, exhibiting high mechanical flexibility. The applicability of this process to print conductive traces on nonconformal 3D objects was also demonstrated through deposition on a 3D-printed thermoplastic object, indicating the potential to combine plasma printing with 3D printing technology. The role of plasma here includes activation of the material present in the aerosol for deposition, increasing the deposition rate, and plasma polymerization in the case of inorganic coatings. The demonstration here establishes a low-cost, high-throughput, and facile process for printing electronic components on nonconventional platforms.

Process development

NASA Technical Reports Server (NTRS)

Bickler, D. B.

1985-01-01

An overview is given of seven process development activities which were presented at this session. Pulsed excimer laser processing of photovoltaic cells was presented. A different pulsed excimer laser annealing was described using a 50 w laser. Diffusion barrier research focused on lowering the chemical reactivity of amorphous thin film on silicon. In another effort adherent and conductive films were successfully achieved. Other efforts were aimed at achieving a simultaneous front and back junction. Microwave enhanced plasma deposition experiments were performed. An updated version of the Solar Array Manufacturing Industry Costing Standards (SAMICS) was presented, along with a life cycle cost analysis of high efficiency cells. The last presentation was on the evaluation of the ethyl vinyl acetate encapsulating system.

Highly Porous Silicon Embedded in a Ceramic Matrix: A Stable High-Capacity Electrode for Li-Ion Batteries.

PubMed

Vrankovic, Dragoljub; Graczyk-Zajac, Magdalena; Kalcher, Constanze; Rohrer, Jochen; Becker, Malin; Stabler, Christina; Trykowski, Grzegorz; Albe, Karsten; Riedel, Ralf

2017-11-28

We demonstrate a cost-effective synthesis route that provides Si-based anode materials with capacities between 2000 and 3000 mAh·g Si -1 (400 and 600 mAh·g composite -1 ), Coulombic efficiencies above 99.5%, and almost 100% capacity retention over more than 100 cycles. The Si-based composite is prepared from highly porous silicon (obtained by reduction of silica) by encapsulation in an organic carbon and polymer-derived silicon oxycarbide (C/SiOC) matrix. Molecular dynamics simulations show that the highly porous silicon morphology delivers free volume for the accommodation of strain leading to no macroscopic changes during initial Li-Si alloying. In addition, a carbon layer provides an electrical contact, whereas the SiOC matrix significantly diminishes the interface between the electrolyte and the electrode material and thus suppresses the formation of a solid-electrolyte interphase on Si. Electrochemical tests of the micrometer-sized, glass-fiber-derived silicon demonstrate the up-scaling potential of the presented approach.

Development of a large area space solar cell assembly

NASA Technical Reports Server (NTRS)

Spitzer, M. B.

1982-01-01

The development of a large area high efficiency solar cell assembly is described. The assembly consists of an ion implanted silicon solar cell and glass cover. The important attributes of fabrication are the use of a back surface field which is compatible with a back surface reflector, and integration of coverglass application and cell fabrications. Cell development experiments concerned optimization of ion implantation processing of 2 ohm-cm boron-doped silicon. Process parameters were selected based on these experiments and cells with area of 34.3 sq cm wre fabricated. The average AMO efficiency of the twenty-five best cells was 13.9% and the best bell had an efficiency of 14.4%. An important innovation in cell encapsulation was also developed. In this technique, the coverglass is applied before the cell is sawed to final size. The coverglass and cell are then sawed as a unit. In this way, the cost of the coverglass is reduced, since the tolerance on glass size is relaxed, and costly coverglass/cell alignment procedures are eliminated. Adhesive investigated were EVA, FEP-Teflon sheet and DC 93-500. Details of processing and results are reported.

Monolithic translucent BaMgAl 10O 17:Eu 2+ phosphors for laser-driven solid state lighting

DOE PAGES

Cozzan, Clayton; Brady, Michael J.; O’Dea, Nicholas; ...

2016-10-11

With high power light emitting diodes and laser diodes being explored for white light generation and visible light communication, thermally robust encapsulation schemes for color-converting inorganic phosphors are essential. In the current work, the canonical blue-emitting phosphor, high purity Eu-doped BaMgAl 10O 17, has been prepared using microwave-assisted heating (25 min) and densified into translucent ceramic phosphor monoliths using spark plasma sintering (30 min). Lastly, the resulting translucent ceramic monoliths convert UV laser light to blue light with the same efficiency as the starting powder and provide superior thermal management in comparison with silicone encapsulation.

Stability of some epoxy-encapsulated diode thermometers

NASA Technical Reports Server (NTRS)

Mangum, B. W.; Evans, G. A., Jr.

1986-01-01

The stability upon thermal cycling and handling of ten small, epoxy-encapsulated silicon diode thermometers at six temperatures in the range from liquid nitrogen temperatures to about 60 C. The nominal temperatures of measurement were -196, -78, 0, 20, 40, and 60 C, as measured on the International Practical Temperature Scale of 1968. Diodes were to be thermally cycled 15 to 20 times. Since NASA anticipates that the uncertainty in their temperature measurements will be + or - 50 mK, uncertainties as large as + or - 10 mK in the measurements of the evaluaton can be accommodated without deleteriously affecting the value of the results of the investigation.

Vacuum-free laminated top electrode with conductive tapes for scalable manufacturing of efficient perovskite solar cells

DOE PAGES

Shao, Yuchuan; Wang, Qi; Dong, Qingfeng; ...

2015-06-25

The efficiency of organometal trihalide perovskites (OTP) solar cells have reached that parity of single crystal silicon, and its nature abundant raw material and solution-process capability promise a bright future for commercialization. However, the vacuum based techniques for metal electrode deposition and additional encapsulation layer increase the cost of the perovskite solar cells dramatically and impede their commercialization process. Here, we report a vacuum-free low temperature lamination technique to fabricate the top electrode by commercial conductive tapes (C-tape). The simple fabrication method yields good quality contact and high efficiency device of 12.7%. The C-tapes also encapsulated the devices effectively, resultingmore » in greatly improved device stability. As a result, the combination of lamination of electrodes and encapsulation layers into a single step significantly reduce the cost of device fabrication.« less

Crack-resistant siloxane molding compounds. [Patent application

DOEpatents

McFarland, J.W.; Swearngin, C.B.

1980-11-03

The crack resistance of phenyl silicone molding resins containing siliceous fillers is improved by incorporating therein about 0.5 to 5.5% by weight of ..beta..-eucryptite, a lithium aluminum silicate having a negative thermal expansion coefficient. These molding resins are particularly suitable for encapsulating electronic devices such as diodes, coils, resistors, and the like.

Microfluidic assisted one-step fabrication of porous silicon@acetalated dextran nanocomposites for precisely controlled combination chemotherapy.

PubMed

Liu, Dongfei; Zhang, Hongbo; Mäkilä, Ermei; Fan, Jin; Herranz-Blanco, Bárbara; Wang, Chang-Fang; Rosa, Ricardo; Ribeiro, António J; Salonen, Jarno; Hirvonen, Jouni; Santos, Hélder A

2015-01-01

An advanced nanocomposite consisting of an encapsulated porous silicon (PSi) nanoparticle and an acid-degradable acetalated dextran (AcDX) matrix (nano-in-nano), was efficiently fabricated by a one-step microfluidic self-assembly approach. The obtained nano-in-nano PSi@AcDX composites showed improved surface smoothness, homogeneous size distribution, and considerably enhanced cytocompatibility. Furthermore, multiple drugs with different physicochemical properties have been simultaneously loaded into the nanocomposites with a ratiometric control. The release kinetics of all the payloads was predominantly controlled by the decomposition rate of the outer AcDX matrix. To facilitate the intracellular drug delivery, a nona-arginine cell-penetrating peptide (CPP) was chemically conjugated onto the surface of the nanocomposites by oxime click chemistry. Taking advantage of the significantly improved cell uptake, the proliferation of two breast cancer cell lines was markedly inhibited by the CPP-functionalized multidrug-loaded nanocomposites. Overall, this nano-in-nano PSi@polymer composite prepared by the microfluidic self-assembly approach is a universal platform for nanoparticles encapsulation and precisely controlled combination chemotherapy. Copyright © 2014 Elsevier Ltd. All rights reserved.

Microfabrication of hybrid fluid membrane for microengines

NASA Astrophysics Data System (ADS)

Chutani, R.; Formosa, F.; de Labachelerie, M.; Badel, A.; Lanzetta, F.

2015-12-01

This paper describes the microfabrication and dynamic characterization of thick membranes providing a technological solution for microengines. The studied membranes are called hybrid fluid-membrane (HFM) and consist of two thin membranes that encapsulate an incompressible fluid. This work details the microelectromechanical system (MEMS) scalable fabrication and characterization of HFMs. The membranes are composite structures based on Silicon spiral springs embedded in a polymer (RTV silicone). The anodic bonding of multiple stacks of Si/glass structures, the fluid filling and the sealing have been demonstrated. Various HFMs were successfully fabricated and their dynamic characterization demonstrates the agreement between experimental and theoretical results.

Type I clathrates as novel silicon anodes: An electrochemical and structural investigation

DOE PAGES

Li, Ying; Raghavan, Rahul; Wagner, Nicholas A.; ...

2015-05-05

In this study, silicon clathrates contain cage-like structures that can encapsulate various guest atoms or molecules. Here we present an electrochemical evaluation of type I silicon clathrates based on Ba 8Al ySi 46-y for the anode material in lithium-ion batteries. Post-cycling characterization with NMR and XRD show no discernible structural or volume changes even after electrochemical insertion of 44 Li into the clathrate structure. The observed properties are in stark contrast with lithiation of other silicon anodes, which become amorphous and suffer from larger volume changes. The lithiation/delithiation processes are proposed to occur in single phase reactions at approximately 0.2more » and 0.4 V vs. Li/Li +, respectively, distinct from other diamond cubic or amorphous silicon anodes. Reversible capacities as high as 499 mAh g -1 at a 5 mA g -1 rate were observed for silicon clathrate with composition Ba 8Al 8.54S i37.46, corresponding to Li:Si of 1.18:1. The results show that silicon clathrates could be promising durable anodes for lithium-ion batteries.« less

Type I clathrates as novel silicon anodes: An electrochemical and structural investigation

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

Li, Ying; Raghavan, Rahul; Wagner, Nicholas A.

In this study, silicon clathrates contain cage-like structures that can encapsulate various guest atoms or molecules. Here we present an electrochemical evaluation of type I silicon clathrates based on Ba 8Al ySi 46-y for the anode material in lithium-ion batteries. Post-cycling characterization with NMR and XRD show no discernible structural or volume changes even after electrochemical insertion of 44 Li into the clathrate structure. The observed properties are in stark contrast with lithiation of other silicon anodes, which become amorphous and suffer from larger volume changes. The lithiation/delithiation processes are proposed to occur in single phase reactions at approximately 0.2more » and 0.4 V vs. Li/Li +, respectively, distinct from other diamond cubic or amorphous silicon anodes. Reversible capacities as high as 499 mAh g -1 at a 5 mA g -1 rate were observed for silicon clathrate with composition Ba 8Al 8.54S i37.46, corresponding to Li:Si of 1.18:1. The results show that silicon clathrates could be promising durable anodes for lithium-ion batteries.« less

Polymer dispensing and embossing technology for the lens type LED packaging

NASA Astrophysics Data System (ADS)

Chien, Chien-Lin Chang; Huang, Yu-Che; Hu, Syue-Fong; Chang, Chung-Min; Yip, Ming-Chuen; Fang, Weileun

2013-06-01

This study presents a ring-type micro-structure design on the substrate and its corresponding micro fabrication processes for a lens-type light-emitting diode (LED) package. The dome-type or crater-type silicone lenses are achieved by a dispensing and embossing process rather than a molding process. Silicone with a high viscosity and thixotropy index is used as the encapsulant material. The ring-type micro structure is adopted to confine the dispensed silicone encapsulant so as to form the packaged lens. With the architecture and process described, this LED package technology herein has three merits: (1) the flexibility of lens-type LED package designs is enhanced; (2) a dome-type package design is used to enhance the intensity; (3) a crater-type package design is used to enhance the view angle. Measurement results show the ratio between the lens height and lens radius can vary from 0.4 to 1 by changing the volume of dispensed silicone. The view angles of dome-type and crater-type packages can reach 155° ± 5° and 175° ± 5°, respectively. As compared with the commercial plastic leaded chip carrier-type package, the luminous flux of a monochromatic blue light LED is improved by 15% by the dome-type package (improved by 7% by the crater-type package) and the luminous flux of a white light LED is improved by 25% by the dome-type package (improved by 13% by the crater-type package). The luminous flux of monochromatic blue light LED and white light LED are respectively improved by 8% and 12% by the dome-type package as compare with the crater-type package.

Functionalized Silk Materials

DTIC Science & Technology

2010-06-10

properties, such as toughness, biocompatibility and biodegrability. Trends in spider silk-like block copolymer secondary structure and assembly behavior...to construct transistors on ultrathin sheets of polyimide . Briefly, the doped silicon nanomembranes were transfer printed onto a film of polyimide ...layer of polyimide was used to encapsulate the active devices. Dry etching the polymer layers completed the fabrication of an array of isolated

Integrated circuit package with lead structure and method of preparing the same

NASA Technical Reports Server (NTRS)

Kennedy, B. W. (Inventor)

1973-01-01

A beam-lead integrated circuit package assembly including a beam-lead integrated circuit chip, a lead frame array bonded to projecting fingers of the chip, a rubber potting compound disposed around the chip, and an encapsulating molded plastic is described. The lead frame array is prepared by photographically printing a lead pattern on a base metal sheet, selectively etching to remove metal between leads, and plating with gold. Joining of the chip to the lead frame array is carried out by thermocompression bonding of mating goldplated surfaces. A small amount of silicone rubber is then applied to cover the chip and bonded joints, and the package is encapsulated with epoxy resin, applied by molding.

A wearable strain sensor based on a carbonized nano-sponge/silicone composite for human motion detection.

PubMed

Yu, Xiao-Guang; Li, Yuan-Qing; Zhu, Wei-Bin; Huang, Pei; Wang, Tong-Tong; Hu, Ning; Fu, Shao-Yun

2017-05-25

Melamine sponge, also known as nano-sponge, is widely used as an abrasive cleaner in our daily life. In this work, the fabrication of a wearable strain sensor for human motion detection is first demonstrated with a commercially available nano-sponge as a starting material. The key resistance sensitive material in the wearable strain sensor is obtained by the encapsulation of a carbonized nano-sponge (CNS) with silicone resin. The as-fabricated CNS/silicone sensor is highly sensitive to strain with a maximum gauge factor of 18.42. In addition, the CNS/silicone sensor exhibits a fast and reliable response to various cyclic loading within a strain range of 0-15% and a loading frequency range of 0.01-1 Hz. Finally, the CNS/silicone sensor as a wearable device for human motion detection including joint motion, eye blinking, blood pulse and breathing is demonstrated by attaching the sensor to the corresponding parts of the human body. In consideration of the simple fabrication technique, low material cost and excellent strain sensing performance, the CNS/silicone sensor is believed to have great potential in the next-generation of wearable devices for human motion detection.

Lumen degradation and chromaticity shift in glass and silicone based high-power phosphor-converted white-emitting diodes under thermal tests

NASA Astrophysics Data System (ADS)

Cheng, Wood-Hi; Tsai, Chun-Chin; Wang, Jimmy

2011-10-01

The lumen degradation and chromaticity shift in glass and silicone based high-power phosphor-converted white-emitting diodes (PC-WLEDs) under accelerated thermal tests at 150°C, 200°C, and 250°C are presented and compared. The glass based PC-WLEDs exhibited better thermal stability than the silicone by 4.8 time reductions in lumen loss 6.8 time reductions in chromaticity shift at 250°C, respectively. The mean-time-to-failure (MTTF) evaluation of glass and silicone based high-power PC-WLEDs in accelerated thermal tests is also presented and compared. The results showed that the glass based PC-WLEDs exhibited higher MTTF than the silicone by 7.53 times in lumen loss and 14.4 times in chromaticity shift at 250°C, respectively. The thermal performance of lumen, chromaticity, and MTTF investigations demonstrated that the thermal stability of the glass based PC-WLEDs were better than the silicone. A better thermal stability phosphor layer of glass as encapsulation material may be beneficial to the many applications where the LED modules with high power and high reliability are demanded.

Flexible packaging for PV modules

NASA Astrophysics Data System (ADS)

Dhere, Neelkanth G.

2008-08-01

Economic, flexible packages that provide needed level of protection to organic and some other PV cells over >25-years have not yet been developed. However, flexible packaging is essential in niche large-scale applications. Typical configuration used in flexible photovoltaic (PV) module packaging is transparent frontsheet/encapsulant/PV cells/flexible substrate. Besides flexibility of various components, the solder bonds should also be flexible and resistant to fatigue due to cyclic loading. Flexible front sheets should provide optical transparency, mechanical protection, scratch resistance, dielectric isolation, water resistance, UV stability and adhesion to encapsulant. Examples are Tefzel, Tedlar and Silicone. Dirt can get embedded in soft layers such as silicone and obscure light. Water vapor transmittance rate (WVTR) of polymer films used in the food packaging industry as moisture barriers are ~0.05 g/(m2.day) under ambient conditions. In comparison, light emitting diodes employ packaging components that have WVTR of ~10-6 g/(m2.day). WVTR of polymer sheets can be improved by coating them with dense inorganic/organic multilayers. Ethylene vinyl acetate, an amorphous copolymer used predominantly by the PV industry has very high O2 and H2O diffusivity. Quaternary carbon chains (such as acetate) in a polymer lead to cleavage and loss of adhesional strength at relatively low exposures. Reactivity of PV module components increases in presence of O2 and H2O. Adhesional strength degrades due to the breakdown of structure of polymer by reactive, free radicals formed by high-energy radiation. Free radical formation in polymers is reduced when the aromatic rings are attached at regular intervals. This paper will review flexible packaging for PV modules.

Hybrid nanoporous silicon optical biosensor architectures for biological sample analysis

NASA Astrophysics Data System (ADS)

Bonanno, Lisa M.; Zheng, Hong; DeLouise, Lisa A.

2010-02-01

This work focuses on demonstrating proof-of-concept for a novel nanoparticle optical signal amplification scheme employing hybrid porous silicon (PSi) sensors. We are investigating the development of target responsive hydrogels integrated with PSi optical transducers. These hybrid-PSi sensors can be designed to provide a tunable material response to target concentration ranging from swelling to complete chain dissolution. The corresponding refractive index changes are significant and readily detected by the PSi transducer. However, to increase signal to noise, lower the limit of detection, and provide a visual read out capability, we are investigating the incorporation of high refractive index nanoparticles (NP) into the hydrogel for optical signal amplification. These NPs can be nonspecifically encapsulated, or functionalized with bioactive ligands to bind polymer chains or participate in cross linking. In this work, we demonstrate encapsulation of high refractive index QD nanoparticles into a 5wt% polyacrylamide hydrogel crosslinked with N,N'-methylenebisacrylamide (BIS) and N,N Bis-acryloyl cystamine (BAC). A QD loading (~0.29 wt%) produced a 2X larger optical shift compared to the control. Dissolution of disulphide crosslinks, using Tris[2-carboxyethyl] phosphine (TCEP) reducing agent, induced gel swelling and efficient QD release. We believe this hybrid sensor concept constitutes a versatile technology platform capable of detecting a wide range of bio/chemical targets provided target analogs can be linked to the polymer backbone and crosslinks can be achieved with target responsive multivalent receptors, such a antibodies. The optical signal amplification scheme will enable a lower limit of detection sensitivity not yet demonstrated with PSi technology and colorimetric readout visible to the naked eye.

Modeling and designing multilayer 2D perovskite / silicon bifacial tandem photovoltaics for high efficiencies and long-term stability.

PubMed

Chung, Haejun; Sun, Xingshu; Mohite, Aditya D; Singh, Rahul; Kumar, Lokendra; Alam, Muhammad A; Bermel, Peter

2017-04-17

A key challenge in photovoltaics today is to develop cell technologies with both higher efficiencies and lower fabrication costs than incumbent crystalline silicon (c-Si) single-junction cells. While tandem cells have higher efficiencies than c-Si alone, it is generally challenging to find a low-cost, high-performance material to pair with c-Si. However, the recent emergence of 22% efficient perovskite photovoltaics has created a tremendous opportunity for high-performance, low-cost perovskite / crystalline silicon tandem photovoltaic cells. Nonetheless, two key challenges remain. First, integrating perovskites into tandem structures has not yet been demonstrated to yield performance exceeding commercially available crystalline silicon modules. Second, the stability of perovskites is inconsistent with the needs of most end-users, who install photovoltaic modules to produce power for 25 years or more. Making these cells viable thus requires innovation in materials processing, device design, fabrication, and yield. We will address these two gaps in the photovoltaic literature by investigating new types of 2D perovskite materials with n-butylammonium spacer layers, and integrating these materials into bifacial tandem solar cells providing at least 30% normalized power production. We find that an optimized 2D perovskite ((BA)₂(MA)₃(Sn_0.6Pb_0.4)₄I₁₃)/silicon bifacial tandem cell, given a globally average albedo of 30%, yields a normalized power production of 30.31%, which should be stable for extended time periods without further change in materials or encapsulation.

High-permeability functionalized silicone magnetic microspheres with low autofluorescence for biomedical applications

PubMed Central

Evans, Benjamin A.; Ronecker, Julia C.; Han, David T.; Glass, Daniel R.; Train, Tonya L.; Deatsch, Alison E.

2017-01-01

Functionalized magnetic microspheres are widely used for cell separations, isolation of proteins and other biomolecules, in vitro diagnostics, tissue engineering, and microscale force spectroscopy. We present here the synthesis and characterization of a silicone magnetic microsphere which can be produced in diameters ranging from 0.5 to 50 μm via emulsion polymerization of a silicone ferrofluid precursor. This bottom-up approach to synthesis ensures a uniform magnetic concentration across all sizes, leading to significant advances in magnetic force generation. We demonstrate that in a size range of 5–20 μm, these spheres supply a full order of magnitude greater magnetic force than leading commercial products. In addition, the unique silicone matrix exhibits autofluorescence two orders of magnitude lower than polystyrene microspheres. Finally, we demonstrate the ability to chemically functionalize our silicone microspheres using a standard EDC reaction, and show that our folate-functionalized silicone microspheres specifically bind to targeted HeLa and Jurkat cells. These spheres show tremendous potential for replacing magnetic polystyrene spheres in applications which require either large magnetic forces or minimal autofluorescence, since they represent order-of-magnitude improvements in each. In addition, the unique silicone matrix and proven biocompatibility suggest that they may be useful for encapsulation and targeted delivery of lipophilic pharmaceuticals. PMID:26952493

Simulation analysis of a novel high efficiency silicon solar cell

NASA Technical Reports Server (NTRS)

Mokashi, Anant R.; Daud, T.; Kachare, A. H.

1985-01-01

It is recognized that crystalline silicon photovoltaic module efficiency of 15 percent or more is required for cost-effective photovoltaic energy utilization. This level of module efficiency requires large-area encapsulated production cell efficiencies in the range of 18 to 20 percent. Though the theoretical maximum of silicon solar cell efficiency for an idealized case is estimated to be around 30 percent, practical performance of cells to-date are considerably below this limit. This is understood to be largely a consequence of minority carrier losses in the bulk as well as at all surfaces including those under the metal contacts. In this paper a novel device design with special features to reduce bulk and surface recombination losses is evaluated using numerical analysis technique. Details of the numerical model, cell design, and analysis results are presented.

Corrosion of silicon integrated circuits and lifetime predictions in implantable electronic devices.

PubMed

Vanhoestenberghe, A; Donaldson, N

2013-06-01

Corrosion is a prime concern for active implantable devices. In this paper we review the principles underlying the concepts of hermetic packages and encapsulation, used to protect implanted electronics, some of which remain widely overlooked. We discuss how technological advances have created a need to update the way we evaluate the suitability of both protection methods. We demonstrate how lifetime predictability is lost for very small hermetic packages and introduce a single parameter to compare different packages, with an equation to calculate the minimum sensitivity required from a test method to guarantee a given lifetime. In the second part of this paper, we review the literature on the corrosion of encapsulated integrated circuits (ICs) and, following a new analysis of published data, we propose an equation for the pre-corrosion lifetime of implanted ICs, and discuss the influence of the temperature, relative humidity, encapsulation and field-strength. As any new protection will be tested under accelerated conditions, we demonstrate the sensitivity of acceleration factors to some inaccurately known parameters. These results are relevant for any application of electronics working in a moist environment. Our comparison of encapsulation and hermetic packages suggests that both concepts may be suitable for future implants.

The AFIT Multielectrode Array for Neural Recording and Simulation: Design, Testing, and Encapsulation

DTIC Science & Technology

1993-12-01

the Device ........................ 13 2.3.1 Silicon Nitride Passivation ................. 13 2.3.2 Polyimide Passivation ................... 14 2.4...Coating .......... ... 49 5.4 Applying the Polyimide ........................ 50 5.4.1 Application of the Polyimide ............ ... 52 5.4.2 Negative...Photo-resist Process ............... 52 5.4.3 Polyimide Etch ........................ 53 5.4.4 Final Cure ............................ 54 5.4.5

Science and Technology of Bio-Inert Thin Films as Hermetic-Encapsulating Coatings for Implantable Biomedical Devices: Application to Implantable Microchip in the Eye for the Artificial Retina

NASA Astrophysics Data System (ADS)

Auciello, Orlando; Shi, Bing

Extensive research has been devoted to the development of neuron prostheses and hybrid bionic systems to establish links between the nervous system and electronic or robotic prostheses with the main focus of restoring motor and sensory functions in blind patients. Artificial retinas, one type of neural prostheses we are currently working on, aim to restore some vision in blind patients caused by retinitis picmentosa or macular degeneration, and in the future to restore vision at the level of face recognition, if not more. Currently there is no hermetic microchip-size coating that provides a reliable, long-term (years) performance as encapsulating coating for the artificial retina Si microchip to be implanted inside the eye. This chapter focuses on the critical topics relevant to the development of a robust, long-term artificial retina device, namely the science and technology of hermetic bio-inert encapsulating coatings to protect a Si microchip implanted in the human eye from being attacked by chemicals existing in the eye's saline environment. The work discussed in this chapter is related to the development of a novel ultrananocrystalline diamond (UNCD) hermetic coating, which exhibited no degradation in rabbit eyes. The material synthesis, characterization, and electrochemical properties of these hermetic coatings are reviewed for application as encapsulating coating for the artificial retinal microchips implantable inside the human eye. Our work has shown that UNCD coatings may provide a reliable hermetic bio-inert coating technology for encapsulation of Si microchips implantable in the eye specifically and in the human body in general. Electrochemical tests of the UNCD films grown under CH4/Ar/H2 (1%) plasma exhibit the lowest leakage currents (˜7 × 10-7 A/cm2) in a saline solution simulating the eye environment. This leakage is incompatible with the functionality of the first-generation artificial retinal microchip. However, the growth of UNCD on top of the Si microchip passivated by a silicon nitride layer or the oxide layers is also under investigation in our group as introduced in this chapter. The electrochemically induced leakage will be reduced by at least one to three orders of magnitude to the range of 10-10 A/cm2, which is compatible with reliable, long-term implants.

Efficiency improvement of GaN-on-silicon thin-film light-emitting diodes with optimized via-like n-electrodes

NASA Astrophysics Data System (ADS)

Feng, Bo; Deng, Biao; Fu, Yi; Liu, Le Gong; Li, Zeng Cheng; Feng, Mei Xin; Zhao, Han Min; Sun, Qian

2017-07-01

This work reports a significant improvement in efficiency by optimizing the via-like n-electrode architecture design of a GaN-based thin-film LED grown on a 6-inch silicon substrate. The external quantum efficiency of the as-fabricated 1.1 mm × 1.1 mm via-thin-film LED chip at 350 mA was increased by 11.3% compared to that of a vertical thin-film LED chip with a conventional finger-like n-electrode. Detailed analysis of encapsulation gain and false color emission patterns illustrated that the significantly improved LED performance was due to enhanced light extraction efficiency and more uniform current spreading, both of which can be attributed to the optimized via-thin-film chip structure. Minimizing the light loss at the periphery of the Ag mirror was demonstrated to be a critical factor for improving light extraction, rather than simply replacing the finger-like n-electrodes with via-like ones. After encapsulation, the median blue lamp power and the wall-plug efficiency of the via-thin-film LED at 350 mA reached 659 mW and 63.7%, respectively.

Optical, colloidal and biological properties of up-converting nanoparticles embedded in polyester nanocarriers

NASA Astrophysics Data System (ADS)

Wawrzyńczyk, Dominika; Kulbacka, Julita; Bazylińska, Urszula

2017-08-01

We have investigated the change in optical properties and biocompatibility of up-converting NaYF4 nanoparticles (NPs) upon encapsulation inside the polyester nanocarriers (NCs) stabilized by Crempophor RH40 (CRH40), poly(D,L-lactide) (PLA), Pluronic P123 (P123). NaYF4:Er3+,Yb3+ NPs showed intense green and red emission, and upon encapsulation the increase of red band in respect to green one was observed, with no luminescence lifetime shortening. Obtained NCs showed prolonged colloidal stability and protective effect of the polymer shell simultaneously preserving the high emission efficiency of nanoparticles embedded within the silicon oil (SO) core. Based on emission spectra, kinetic measurements and cytotoxicity studies upon human malignant melanoma Me45 cell line we have shown the advantages of using polyester NCs as containers for the up-converting NPs. Due to the possibility of co-encapsulation of photosensitizers the obtained nanocarriers showed potential for application in theranostics.

On-demand Antimicrobial Treatment with Antibiotic-Loaded Porous Silicon Capped with a pH-Responsive Dual Plasma Polymer Barrier.

PubMed

Vasani, Roshan B; Szili, Endre J; Rajeev, Gayathri; Voelcker, Nicolas H

2017-07-04

Chronic wounds are a major socio-economic problem. Bacterial infections in such wounds are a major contributor to lack of wound healing. An early indicator of wound infection is an increase in pH of the wound fluid. Herein, we describe the development of a pH-responsive drug delivery device that can potentially be used for wound decontamination in situ and on-demand in response to an increase in the pH of the wound environment. The device is based on a porous silicon film that provides a reservoir for encapsulation of an antibiotic within the pores. Loaded porous silicon is capped with dual plasma polymer layers of poly(1,7-octadiene) and poly(acrylic acid), which provide a pH-responsive barrier for on-demand release of the antibiotic. We demonstrate that release of the antibiotic is inhibited in aqueous buffer at pH 5, whereas the drug is released in a sustainable manner at pH 8. Importantly, the released drug was bacteriostatic against the Pseudomonas aeruginosa wound pathogen. In the future, incorporation of the delivery device into wound dressings could potentially be utilized for non-invasive decontamination of wounds. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fast and efficient proteolysis by reusable pepsin-encapsulated magnetic sol-gel material for mass spectrometry-based proteomics applications.

PubMed

Kayili, H Mehmet; Salih, Bekir

2016-08-01

Hydrophobic silicon-based material having magnetic properties was fairly synthesized by a classical sol-gel approach. Pepsin enzyme was encapsulated in the sol-gel material and the enzyme activity was evaluated in consequence of the digestion of some common proteins such as α- and β-casein, cytochrome c, myoglobin, and bovine serum albumin (BSA) both in a single protein batch and in the protein mixture. The optimum digestion time of the studied proteins using pepsin-encapsulated magnetic sol-gel material was found to be 20min. To produce the magnetic sol-gel material for convenient and easy proteomics applications, Fe3O4 was doped inside sol-gel material during the gelation step. It was observed that the activity of encapsulated pepsin was not affected by the amount of Fe3O4. Poly(ethylene glycol) was also inserted in sol-gel bulk to obtain suitable roughness and increase the hydrophilicity of the material surface to let protein molecules reach to the sol-gel material easily. The digestion of the protein mixture and non-fat bovine milk was performed with the pepsin-encapsulated magnetic sol-gel material and the digested solutions were analyzed using SDS-PAGE, MALDI-TOF-MS and LC-MS/MS for the protein identification. Reusability of the pepsin-encapsulated sol-gel material was examined and it was determined that they could be used at least 20 times. Finally, IgG digestions with a fast incubation time period were carried out using pepsin-encapsulated sol-gel material for generation of (Fab)2 product to evaluate the kinetic performance of the material. Copyright © 2016 Elsevier B.V. All rights reserved.

Synchrotron X-Ray Topography for Encapsulation Stress/Strain and Crack Detection in Crystalline Silicon Modules

DOE PAGES

Colli, Alessandra; Attenkofer, Klaus; Raghothamachar, Balaji; ...

2016-07-14

Here in this article, we present the first experiment to prove the capabilities of X-ray topography for the direct imaging and analysis of defects, stress, and strain affecting the cell within the laminated photovoltaic (PV) module. Cracks originating from grain boundaries structures have been detected, developing along the cleavage planes of the crystal. The strain affecting the cell is clearly visualized through the bending of the metallization line images and can be easily mapped. While the recording conditions need to be optimized to maximize image contrast, this experiment demonstrates how synchrotron facilities can enable PV industry and research to characterizemore » full PV modules. Appropriate development of the technique could also lead to future use of laboratory-level X-ray sources.« less

The role of nanostructured mesoporous silicon in discriminating in vitro calcification for electrospun composite tissue engineering scaffolds

NASA Astrophysics Data System (ADS)

Fan, Dongmei; Akkaraju, Giridhar R.; Couch, Ernest F.; CanhamCurrent Address, Intrinsiq Materials Ltd, Geraldine Road, Malvern Wr14 3SZ Uk, Leigh T.; Coffer, Jeffery L.

2011-02-01

The impact of mesoporous silicon (PSi) particles-embedded either on the surface, or totally encapsulated within electrospun poly (ε-caprolactone) (PCL) fibers-on its properties as a tissue engineering scaffold is assessed. Our findings suggest that the resorbable porous silicon component can sensitively accelerate the necessary calcification process in such composites. Calcium phosphate deposition on the scaffolds was measured via in vitro calcification assays both at acellular and cellular levels. Extensive attachment of fibroblasts, human adult mesenchymal stem cells, and mouse stromal cells to the scaffold were observed. Complementary cell differentiation assays and ultrastructural measurements were also carried out; the levels of alkaline phosphatase expression, a specific biomarker for mesenchymal stem cell differentiation, show that the scaffolds have the ability to mediate such processes, and that the location of the Si plays a key role in levels of expression.

Large-area triple-junction a-Si alloy production scaleup. Annual subcontract report, 17 March 1993--18 March 1994

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

Oswald, R.; Morris, J.

1994-11-01

The objective of this subcontract over its three-year duration is to advance Solarex`s photovoltaic manufacturing technologies, reduce its a-Si:H module production costs, increase module performance and expand the Solarex commercial production capacity. Solarex shall meet these objectives by improving the deposition and quality of the transparent front contact, by optimizing the laser patterning process, scaling-up the semiconductor deposition process, improving the back contact deposition, scaling-up and improving the encapsulation and testing of its a-Si:H modules. In the Phase 2 portion of this subcontract, Solarex focused on improving deposition of the front contact, investigating alternate feed stocks for the front contact,more » maximizing throughput and area utilization for all laser scribes, optimizing a-Si:H deposition equipment to achieve uniform deposition over large-areas, optimizing the triple-junction module fabrication process, evaluating the materials to deposit the rear contact, and optimizing the combination of isolation scribe and encapsulant to pass the wet high potential test. Progress is reported on the following: Front contact development; Laser scribe process development; Amorphous silicon based semiconductor deposition; Rear contact deposition process; Frit/bus/wire/frame; Materials handling; and Environmental test, yield and performance analysis.« less

Photopolymerizable liquid encapsulants for microelectronic devices

NASA Astrophysics Data System (ADS)

Baikerikar, Kiran K.

2000-10-01

Plastic encapsulated microelectronic devices consist of a silicon chip that is physically attached to a leadframe, electrically interconnected to input-output leads, and molded in a plastic that is in direct contact with the chip, leadframe, and interconnects. The plastic is often referred to as the molding compound, and is used to protect the chip from adverse mechanical, thermal, chemical, and electrical environments. Encapsulation of microelectronic devices is typically accomplished using a transfer molding process in which the molding compound is cured by heat. Most transfer molding processes suffer from significant problems arising from the high operating temperatures and pressures required to fill the mold. These aspects of the current process can lead to thermal stresses, incomplete mold filling, and wire sweep. In this research, a new strategy for encapsulating microelectronic devices using photopolymerizable liquid encapsulants (PLEs) has been investigated. The PLEs consist of an epoxy novolac-based vinyl ester resin (˜25 wt.%), fused silica filler (70--74 wt.%), and a photoinitiator, thermal initiator, and silane coupling agent. For these encapsulants, the use of light, rather than heat, to initiate the polymerization allows precise control over when the reaction starts, and therefore completely decouples the mold filling and the cure. The low viscosity of the PLEs allows for low operating pressures and minimizes problems associated with wire sweep. In addition, the in-mold cure time for the PLEs is equivalent to the in-mold cure times of current transfer molding compounds. In this thesis, the thermal and mechanical properties, as well as the viscosity and adhesion of photopolymerizable liquid encapsulants, are reported in order to demonstrate that a UV-curable formulation can have the material properties necessary for microelectronic encapsulation. In addition, the effects of the illumination time, postcure time, fused silica loading, and the inclusion of a thermal initiator on the thermal and mechanical properties of the final cured encapsulants have been investigated. The results show that the material properties of the PLEs are the same, if not better, than those exhibited by conventional transfer molding compounds and demonstrate the potential of using PLEs for encapsulating microelectronic devices.

Flexible, FEP-Teflon covered solar cell module development

NASA Technical Reports Server (NTRS)

Rauschenbach, H. S.; Cannady, M. D.

1976-01-01

Techniques and equipment were developed for the large scale, low-cost fabrication of lightweight, roll-up and fold-up, FEP-Teflon encapsulated solar cell modules. Modules were fabricated by interconnecting solderless single-crystal silicon solar cells and heat laminating them at approximately 300 C between layers of optically clear FEP and to a loadbearing Kapton substrate sheet. Modules were fabricated from both conventional and wraparound contact solar cells. A heat seal technique was developed for mechanically interconnecting modules into an array. The electrical interconnections for both roll-up and fold-up arrays were also developed. The use of parallel-gap resistance welding, ultrasonic bonding, and thermocompression bonding processes for attaching interconnects to solar cells were investigated. Parallel-gap welding was found to be best suited for interconnecting the solderless solar cells into modules. Details of the fabrication equipment, fabrication processes, module and interconnect designs, environmental test equipment, and test results are presented.

New polyurethane/docosane microcapsules as phase-change materials for thermal energy storage.

PubMed

Felix De Castro, Paula; Shchukin, Dmitry G

2015-07-27

Polyurethane microcapsules were prepared by mini-emulsion interfacial polymerization for encapsulation of phase-change material (n-docosane) for energy storage. Three steps were followed with the aim to optimize synthesis conditions of the microcapsules. First, polyurethane microcapsules based on silicone oil core as an inert template with different silicone oil/poly(ethylene glycol)/4,4'-diphenylmethane diisocyanate wt % ratio were synthesized. The surface morphology of the capsules was analyzed by scanning electronic microscopy (SEM) and the chemical nature of the shell was monitored by Fourier transform infrared spectroscopy (FT-IR). Capsules with the silicone oil/poly(ethylene glycol)/4,4'-diphenylmethane diisocyanate 10/20/20 wt % ratio showed the best morphological features and shell stability with average particle size about 4 μm, and were selected for the microencapsulation of the n-docosane. In the second stage, half of the composition of silicone oil was replaced with n-docosane and, finally, the whole silicone oil content was replaced with docosane following the same synthetic procedure used for silicone oil containing capsules. Thermal and cycling stability of the capsules were investigated by thermal gravimetric analysis (TGA) and the phase-change behavior was evaluated by differential scanning calorimetry (DSC). © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fabrication of a Cryogenic Bias Filter for Ultrasensitive Focal Plane

NASA Technical Reports Server (NTRS)

Chervenak, James; Wollack, Edward

2012-01-01

A fabrication process has been developed for cryogenic in-line filtering for the bias and readout of ultrasensitive cryogenic bolometers for millimeter and submillimeter wavelengths. The design is a microstripline filter that cuts out, or strongly attenuates, frequencies (10 50 GHz) that can be carried by wiring staged at cryogenic temperatures. The filter must have 100-percent transmission at DC and low frequencies where the bias and readout lines will carry signal. The fabrication requires the encapsulation of superconducting wiring in a dielectric-metal envelope with precise electrical characteristics. Sufficiently thick insulation layers with high-conductivity metal layers fully surrounding a patterned superconducting wire in arrayable formats have been demonstrated. A degenerately doped silicon wafer has been chosen to provide a metallic ground plane. A metallic seed layer is patterned to enable attachment to the ground plane. Thick silicon dioxide films are deposited at low temperatures to provide tunable dielectric isolation without degrading the metallic seed layer. Superconducting wiring is deposited and patterned using microstripline filtering techniques to cut out the relevant frequencies. A low Tc superconductor is used so that it will attenuate power strongly above the gap frequency. Thick dielectric is deposited on top of the circuit, and then vias are patterned through both dielectric layers. A thick conductive film is deposited conformally over the entire circuit, except for the contact pads for the signal and bias attachments to complete the encapsulating ground plane. Filters are high-aspect- ratio rectangles, allowing close packing in one direction, while enabling the chip to feed through the wall of a copper enclosure. The chip is secured in the copper wall using a soft metal seal to make good thermal and electrical contact to the outer shield.

Conformable wearable systems comprising organic electronics on foil for well being and healthcare (presentation video)

NASA Astrophysics Data System (ADS)

de Kok, Margreet M.

2014-10-01

Integration of electronics into materials and objects that have not been functionalized with electronics before, open up extensive possibilities to support mankind. By adding intelligence and/or operating power to materials in close skin contact like clothing, furniture or bandages the health of people can be monitored or even improved. Foil based electronics are interesting components to be integrated as they are thin, large area and cost effective available components Our developed technology of printed electronic structures to which components are reliably bonded, fulfills the promise. We have integrated these components into textiles and built wearable encapsulated products with foil based electronics. Foil components with organic and inorganic LEDs are interconnected and laminated onto electronic textiles by using conductive adhesives to bond the contact pads of the component to conductive yarns in the textile. Modelling and reliability testing under dynamic circumstances provided important insights in order to optimise the technology. The design of the interconnection and choice of conductive adhesive / underfill and lamination contributed to the durability of the system. Transition zones from laminated foil to textile are engineered to withstand dynamic use. As an example of a product, we have realized an electronic wristband that is encapsulated in rubber and has a number of sensor functionalities integrated on stretchable electronic circuits based on Cu and Ag. The encapsulation with silicone or polyurethanes was performed such, that charging and sensor/skin contacts are possible while simultaneously protecting the electronics from mechanical and environmental stresses.

Antifibrotic effect of dexamethasone/alginate-coated silicone sheet in the abraded middle ear mucosa.

PubMed

Jang, Chul Ho; Ahn, Seung Hyun; Kim, Geun Hyung

2016-12-01

Silicone sheet is a material which is commonly used in middle ear surgery to prevent the formation of adhesions between the tympanic membrane and the medial bony wall of the middle ear cavity. However, silicone sheet can induce a tight and hard fibrous capsule in the region of the stapes, and this is particularly common in cases of eustachian tube dysfunction. As a result of the fibrous encapsulation around the silicone sheet, postoperative aeration of the stapes can be interrupted causing poor hearing gain. In this study, we performed an in vitro and in vivo evaluation of the antifibrotic effects of a dexamethasone and alginate (Dx/alginate) coating on silicone sheet. The Dx/alginate-coated silicone sheets were fabricated using a plasma-treatment and coating method. The Dx/alginate-coated silicone sheets effectively limited in vitro fibroblast attachment and proliferation due to the controlled release of Dx, which can be modified by manipulation of the alginate coating. For the in-vivo evaluation, guinea pigs (albino, male, weighing 250g) were divided into two groups, with the control group (n=5) implanted with silicone sheet and the test group (n=5) receiving Dx/alginate-coated silicone sheet. Animals were sacrificed 3 weeks after implantation, and histological analysis was performed using hematoxylin and eosin (H&E) and immunohistochemical staining techniques. Dx/alginate-coated silicone sheets showed marked inhibition of fibrosis in both the in vitro and in vivo studies. Silicone sheet that incorporates a Dx/alginate coating can release Dx and inhibit fibrosis in the middle ear. This material could be utilized in middle ear surgery as a means of preserving proper aeration and hearing gain following ossiculoplasty. Copyright © 2016 Elsevier B.V. All rights reserved.

Intracellular trafficking of silicon particles and logic-embedded vectors

NASA Astrophysics Data System (ADS)

Ferrati, Silvia; Mack, Aaron; Chiappini, Ciro; Liu, Xuewu; Bean, Andrew J.; Ferrari, Mauro; Serda, Rita E.

2010-08-01

Mesoporous silicon particles show great promise for use in drug delivery and imaging applications as carriers for second-stage nanoparticles and higher order particles or therapeutics. Modulation of particle geometry, surface chemistry, and porosity allows silicon particles to be optimized for specific applications such as vascular targeting and avoidance of biological barriers commonly found between the site of drug injection and the final destination. In this study, the intracellular trafficking of unloaded carrier silicon particles and carrier particles loaded with secondary iron oxide nanoparticles was investigated. Following cellular uptake, membrane-encapsulated silicon particles migrated to the perinuclear region of the cell by a microtubule-driven mechanism. Surface charge, shape (spherical and hemispherical) and size (1.6 and 3.2 μm) of the particle did not alter the rate of migration. Maturation of the phagosome was associated with an increase in acidity and acquisition of markers of late endosomes and lysosomes. Cellular uptake of iron oxide nanoparticle-loaded silicon particles resulted in sorting of the particles and trafficking to unique destinations. The silicon carriers remained localized in phagosomes, while the second stage iron oxide nanoparticles were sorted into multi-vesicular bodies that dissociated from the phagosome into novel membrane-bound compartments. Release of iron from the cells may represent exocytosis of iron oxide nanoparticle-loaded vesicles. These results reinforce the concept of multi-functional nanocarriers, in which different particles are able to perform specific tasks, in order to deliver single- or multi-component payloads to specific sub-cellular compartments.Mesoporous silicon particles show great promise for use in drug delivery and imaging applications as carriers for second-stage nanoparticles and higher order particles or therapeutics. Modulation of particle geometry, surface chemistry, and porosity allows silicon particles to be optimized for specific applications such as vascular targeting and avoidance of biological barriers commonly found between the site of drug injection and the final destination. In this study, the intracellular trafficking of unloaded carrier silicon particles and carrier particles loaded with secondary iron oxide nanoparticles was investigated. Following cellular uptake, membrane-encapsulated silicon particles migrated to the perinuclear region of the cell by a microtubule-driven mechanism. Surface charge, shape (spherical and hemispherical) and size (1.6 and 3.2 μm) of the particle did not alter the rate of migration. Maturation of the phagosome was associated with an increase in acidity and acquisition of markers of late endosomes and lysosomes. Cellular uptake of iron oxide nanoparticle-loaded silicon particles resulted in sorting of the particles and trafficking to unique destinations. The silicon carriers remained localized in phagosomes, while the second stage iron oxide nanoparticles were sorted into multi-vesicular bodies that dissociated from the phagosome into novel membrane-bound compartments. Release of iron from the cells may represent exocytosis of iron oxide nanoparticle-loaded vesicles. These results reinforce the concept of multi-functional nanocarriers, in which different particles are able to perform specific tasks, in order to deliver single- or multi-component payloads to specific sub-cellular compartments. Electronic supplementary information (ESI) available: Confocal microscopy image showing internalized negative particles, and movie of the intracellular migration of silicon particles. See DOI: 10.1039/c0nr00227e

A high-quality factor of 267 000 micromechanical silicon resonator utilizing TED-free torsional vibration mode

NASA Astrophysics Data System (ADS)

Nakamura, K.; Naito, Y.; Onishi, K.; Kawakatsu, H.

2012-12-01

In industrial applications of a micromechanical silicon resonator as a physical sensor, a high-quality factor Q and a low-temperature coefficient of Q (TCQ) are required for high sensitivity in a wide temperature range. Although the newly developed thin film encapsulation technique enables a beam to operate with low viscous damping in a vacuum cavity, the Q of a flexural vibration mode is limited by thermo-elastic damping (TED). We proposed a torsional beam resonator which features both a high Q and a low TCQ because theoretically the torsional vibration mode does not suffer from TED. From experiments, Q of 267 000 and TCQ of 1.4 for the 20 MHz torsional vibration mode were observed which were superior to those of the flexural mode. The pressure of the residual gas in the cavity of only 20 pl volume, which is one of the energy loss factors limiting the Q, was successfully estimated to be 1-14 Pa. Finally, the possibilities of improving the Q and the difference of the measured TCQ from a theoretical value were discussed.

Flexible Transient Optical Waveguides and Surface-Wave Biosensors Constructed from Monocrystalline Silicon.

PubMed

Bai, Wubin; Yang, Hongjun; Ma, Yinji; Chen, Hao; Shin, Jiho; Liu, Yonghao; Yang, Quansan; Kandela, Irawati; Liu, Zhonghe; Kang, Seung-Kyun; Wei, Chen; Haney, Chad R; Brikha, Anlil; Ge, Xiaochen; Feng, Xue; Braun, Paul V; Huang, Yonggang; Zhou, Weidong; Rogers, John A

2018-06-26

Optical technologies offer important capabilities in both biological research and clinical care. Recent interest is in implantable devices that provide intimate optical coupling to biological tissues for a finite time period and then undergo full bioresorption into benign products, thereby serving as temporary implants for diagnosis and/or therapy. The results presented here establish a silicon-based, bioresorbable photonic platform that relies on thin filaments of monocrystalline silicon encapsulated by polymers as flexible, transient optical waveguides for accurate light delivery and sensing at targeted sites in biological systems. Comprehensive studies of the mechanical and optical properties associated with bending and unfurling the waveguides from wafer-scale sources of materials establish general guidelines in fabrication and design. Monitoring biochemical species such as glucose and tracking physiological parameters such as oxygen saturation using near-infrared spectroscopic methods demonstrate modes of utility in biomedicine. These concepts provide versatile capabilities in biomedical diagnosis, therapy, deep-tissue imaging, and surgery, and suggest a broad range of opportunities for silicon photonics in bioresorbable technologies. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Control of single-electron charging of metallic nanoparticles onto amorphous silicon surface.

PubMed

Weis, Martin; Gmucová, Katarína; Nádazdy, Vojtech; Capek, Ignác; Satka, Alexander; Kopáni, Martin; Cirák, Július; Majková, Eva

2008-11-01

Sequential single-electron charging of iron oxide nanoparticles encapsulated in oleic acid/oleyl amine envelope and deposited by the Langmuir-Blodgett technique onto Pt electrode covered with undoped hydrogenated amorphous silicon film is reported. Single-electron charging (so-called quantized double-layer charging) of nanoparticles is detected by cyclic voltammetry as current peaks and the charging effect can be switched on/off by the electric field in the surface region induced by the excess of negative/positive charged defect states in the amorphous silicon layer. The particular charge states in amorphous silicon are created by the simultaneous application of a suitable bias voltage and illumination before the measurement. The influence of charged states on the electric field in the surface region is evaluated by the finite element method. The single-electron charging is analyzed by the standard quantized double layer model as well as two weak-link junctions model. Both approaches are in accordance with experiment and confirm single-electron charging by tunnelling process at room temperature. This experiment illustrates the possibility of the creation of a voltage-controlled capacitor for nanotechnology.

Focal release of neurotrophic factors by biodegradable microspheres enhance motor and sensory axonal regeneration in vitro and in vivo.

PubMed

Santos, Daniel; Giudetti, Guido; Micera, Silvestro; Navarro, Xavier; Del Valle, Jaume

2016-04-01

Neurotrophic factors (NTFs) promote nerve regeneration and neuronal survival after peripheral nerve injury. However, drawbacks related with administration and bioactivity during long periods limit their therapeutic application. In this study, PLGA microspheres (MPs) were used to locally release different NTFs and evaluate whether they accelerate axonal regeneration in comparison with free NTFs or controls. ELISA, SEM, UV/visible light microscopy, organotypic cultures of DRG explants and spinal cord slices were used to characterize MP properties and the bioactivity of the released NTFs. Results of organotypic cultures showed that encapsulated NTFs maintain longer bioactivity and enhance neurite regeneration of both sensory and motor neurons compared with free NTFs. For in vivo assays, the rat sciatic nerve was transected and repaired with a silicone tube filled with collagen gel or collagen mixed with PBS encapsulated MPs (control groups) and with free or encapsulated NGF, BDNF, GDNF or FGF-2. After 20 days, a retrotracer was applied to the regenerated nerve to quantify motor and sensory axonal regeneration. NTF encapsulation in MPs improved regeneration of both motor and sensory axons, as evidenced by increased numbers of retrolabeled neurons. Hence, our results show that slow release of NTFs with PLGA MP enhance nerve regeneration. Copyright © 2016 Elsevier B.V. All rights reserved.

Ultra-sensitive Hall sensors based on graphene encapsulated in hexagonal boron nitride

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

Dauber, Jan; Stampfer, Christoph; Peter Grünberg Institute

2015-05-11

The encapsulation of graphene in hexagonal boron nitride provides graphene on substrate with excellent material quality. Here, we present the fabrication and characterization of Hall sensor elements based on graphene boron nitride heterostructures, where we gain from high mobility and low charge carrier density at room temperature. We show a detailed device characterization including Hall effect measurements under vacuum and ambient conditions. We achieve a current- and voltage-related sensitivity of up to 5700 V/AT and 3 V/VT, respectively, outpacing state-of-the-art silicon and III/V Hall sensor devices. Finally, we extract a magnetic resolution limited by low frequency electric noise of less than 50more » nT/√(Hz) making our graphene sensors highly interesting for industrial applications.« less

Effect of diblock copolymer properties on the photophysical properties of dendrimer silicon phthalocyanine nanoconjugates

NASA Astrophysics Data System (ADS)

Chen, Kuizhi; Pan, Sujuan; Zhuang, Xuemei; Lv, Hafei; Que, Shoulin; Xie, Shusen; Yang, Hongqin; Peng, Yiru

2016-07-01

1-2 generation poly(benzyl aryl ether) dendrimer silicon phthalocyanines with axially disubstituted cyano terminal functionalities (G n -DSiPc(CN)4 n , (G n = n-generation dendrimer, n = 1-2)) were synthesized. Their structures were characterized by elemental analysis, IR, 1H NMR, and ESI-MS. Polymeric nanoparticles (G n -DSiPc(CN)4 n /m) were formed through encapsulating G n -DSiPc(CN)4 n into three monomethoxyl poly(ethylene glycol)-poly(ɛ-caprolactone) diblock copolymers (MPEG-PCL) with different hydrophilic/hydrophobic proportion, respectively. The effect of dendritic generation and the hydrophilic/hydrophobic proportion of diblock copolymers on the UV/Vis and fluorescence spectra of G n -DSiPc(CN)4 n and G n -DSiPc(CN)4 n /m were studied. The photophysical properties of polymeric nanoparticles exhibited dendritic generation and hydrophilic/hydrophobic proportion dependence. The fluorescence intensities and lifetimes of G n -DSiPc(CN)4 n /m were lower than the corresponding free dendrimer phthalocyanines. G n -DSiPc(CN)4 n encapsulated into MPEG-PCL with hydrophilic/hydrophobic molecular weight ratio 2000:4000 exhibited excellent photophysical property. The mean diameter of MPEG2000-PCL2000 micelles was about 70 nm, which decreased when loaded with G n -DSiPc(CN)4 n .

A low feed-through 3D vacuum packaging technique with silicon vias for RF MEMS resonators

NASA Astrophysics Data System (ADS)

Zhao, Jicong; Yuan, Quan; Kan, Xiao; Yang, Jinling; Yang, Fuhua

2017-01-01

This paper presents a wafer-level three-dimensional (3D) vacuum packaging technique for radio frequency microelectromechanical systems (RF MEMS) resonators. A Sn-rich Au-Sn solder bonding is employed to provide a vacuum encapsulation as well as electrical conductions. Vertical silicon vias are micro-fabricated by glass reflow process. The optimized grounding, via pitch, and all-round shielding effectively reduce feed-through capacitance. Thus the signal-to-background ratios (SBRs) of the transmission signals increase from 17 dB to 20 dB, and the quality factor (Q) values of the packaged resonators go from around 8000 up to more than 9500. The measured average leak rate and shear strength are (2.55  ±  0.9)  ×  10-8 atm-cc s-1 and 42.53  ±  4.19 MPa, respectively. Furthermore, thermal cycling test between  -40 °C and 100 °C and high temperature storage test at 150 °C show that the resonant-frequency drifts are less than  ±7 ppm. In addition, the SBRs and the Q values have no obvious change after the tests. The experimental results demonstrated that the proposed encapsulation technique is well suited for the applications of RF MEMS devices.

Lithium silicide nanocrystals: synthesis, chemical stability, thermal stability, and carbon encapsulation.

PubMed

Cloud, Jacqueline E; Wang, Yonglong; Li, Xuemin; Yoder, Tara S; Yang, Yuan; Yang, Yongan

2014-10-20

Lithium silicide (LixSi) is the lithiated form of silicon, one of the most promising anode materials for the next generation of lithium-ion batteries (LIBs). In contrast to silicon, LixSi has not been well studied. Herein we report a facile high-energy ball-milling-based synthesis of four phase-pure LixSi (x = 4.4, 3.75, 3.25, and 2.33), using hexane as the lubricant. Surprisingly, the obtained Li3.75Si phase shows significant downward shifts in all X-ray diffraction peak positions, compared with the standard. Our interpretation is that the high-energy ball-mill-synthesized Li3.75Si presents smaller internal pressures and larger lattice constants. The chemical-stability study reveals that only surface reactions occur after Li4.4Si and Li3.75Si are immersed in several battery-assembly-related chemicals. The thermal-stability study shows that Li4.4Si is stable up to 350 °C and Li3.75Si is stable up to 200 °C. This remarkable thermal stability of Li3.75Si is in stark contrast to the long-observed metastability for electrochemically synthesized Li3.75Si. The carbon encapsulation of Li4.4Si has also been studied for its potential applications in LIBs.

Encapsulation of fluorescence vegetable extracts within a templated sol-gel matrix

NASA Astrophysics Data System (ADS)

Lacatusu, Ioana; Badea, Nicoleta; Nita, Rodica; Murariu, Alina; Miculescu, Florin; Iosub, Ion; Meghea, Aurelia

2010-04-01

The sol-gel encapsulation of labile substances with specific properties and recognition functions within robust polymer matrices remains a challenging task, despite the considerable research that has been focused on this field. Numerous studies have been reported in the field of sol-gel processes regarding different physical and chemical packing of sensitive biomolecules encapsulated in silica matrix. In this paper the classical sol-gel synthesis has been used under mild conditions in order to minimize denaturizing effects on encapsulated active vegetable extracts from flavones class. The silica templated matrix was obtained by using two types of surfactants with different alkyl chain (didodecyldimethyl-ammonium bromide and trioctadecylmetilammonium bromide) as structure-directing agents for the silicon oxide framework. An organic precursor of silicic acid (triethoxymethylsilane) has been used and it was processed by competitive hydrolysis and polycondensation reactions under controlled directions assured by the presence of oriented template. Silica materials thus obtained are used for encapsulation of two flavonoid samples containing as active principles two sources: rutin and a vegetable extract from Begonia plant. The synthesis of encapsulated nanocompounds has been achieved taking into consideration the specific interaction between the colloidal gel precursors and molecular structures of selected biomolecules. The main objective was to improve the encapsulation conditions for specific biomolecules, searching for the highest stability and functionality without loosing the quality of the flavonoid properties, particularly optical properties like fluorescence. The structural properties of the encapsulated samples have been studied by FT-IR and UV-VIS spectroscopy, thermal analysis and SEM/EDX analysis. The fluorescence experiments showed that, in the case of all four encapsulated samples, the fluorescence spectra manifest a significant increase in intensity signals, with more than 10 times for individual flavonoid and 50 times for Begonia extract. This behaviour are mainly assigned to the physical interaction of flavonoid molecules with the residual hydroxyl groups of silica, excellent synergistic properties of silica and the favourable conformation arrangement of organic molecules inside the silica network. The size distribution of synthesised polymeric silica materials have been investigated by dynamic light scattering (DLS) and optical microscopy.

Efficiencies of Dye-Sensitized Solar Cells using Ferritin-Encapsulated Quantum Dots with Various Staining Methods

NASA Astrophysics Data System (ADS)

Perez, Luis

Dye-sensitized solar cells (DSSC) have the potential to replace traditional and cost-inefficient crystalline silicon or ruthenium solar cells. This can only be accomplished by optimizing DSSC's energy efficiency. One of the major components in a dye-sensitized solar cell is the porous layer of titanium dioxide. This layer is coated with a molecular dye that absorbs sunlight. The research conducted for this paper focuses on the different methods used to dye the porous TiO2 layer with ferritin-encapsulated quantum dots. Multiple anodes were dyed using a method known as SILAR which involves deposition through alternate immersion in two different solutions. The efficiencies of DSSCs with ferritin-encapsulated lead sulfide dye deposited using SILAR were subsequently compared against the efficiencies produced by cells using the traditional immersion method. It was concluded that both methods resulted in similar efficiencies (? .074%) however, the SILAR method dyed the TiO2 coating significantly faster than the immersion method. On a related note, our experiments concluded that conducting 2 SILAR cycles yields the highest possible efficiency for this particular binding method. National Science Foundation.

Approximation of effective moisture-diffusion coefficient to characterize performance of a barrier coating

NASA Astrophysics Data System (ADS)

Nagai, Shingo

2013-11-01

We report estimation of the effective diffusion coefficient of moisture through a barrier coating to develop an encapsulation technology for the thin-film electronics industry. This investigation targeted a silicon oxide (SiOx) film that was deposited on a plastic substrate by a large-process-area web coater. Using the finite difference method based on diffusion theory, our estimation of the effective diffusion coefficient of a SiOx film corresponded to that of bulk glass that was previously reported. This result suggested that the low diffusivities of barrier films can be obtained on a mass-production level in the factory. In this investigation, experimental observations and mathematical confirmation revealed the limit of the water vapor transmission rate on the single barrier coating.

Use of Glass Reinforced Concrete (GRC) as a substrate for photovoltaic modules

NASA Technical Reports Server (NTRS)

Eirls, J. L.

1980-01-01

A substrate for flat plate photovoltaic solar panel arrays using a glass fiber reinforced concrete (GRC) material was developed. The installed cost of this GRC panel is 30% less than the cost goal of the Near Term Low-Cost Flat Plate Photovoltaic Solar Array Program. The 4 ft by 8 ft panel is fabricated from readily available inexpensive materials, weighs a nominal 190 lbs., has exceptionally good strength and durability properties (rigid and resists weathering), is amenable to mass production and is easily installed on simple mountings. Solar cells are encapsulated in ethylene/vinyl acetate with Tedlar backing and Korad cover film. The laminates are attached to the GRC substrate with acrylic transfer tape and edge sealed with silicone RTV adhesive.

The Impact of Dopant Segregation on the Maximum Carrier Density in Si:P Multilayers.

PubMed

Keizer, Joris G; McKibbin, Sarah R; Simmons, Michelle Y

2015-07-28

Abrupt dopant profiles and low resistivity are highly sought after qualities in the silicon microelectronics industry and, more recently, in the development of an all epitaxial Si:P based quantum computer. If we increase the active carrier density in silicon to the point where the material becomes superconducting, while maintaining a low thermal budget, it will be possible to fabricate nanoscale superconducting devices using the highly successful technique of depassivation lithography. In this work, we investigate the dopant profile and activation in multiple high density Si:P δ-layers fabricated by stacking individual layers with intervening silicon growth. We determine that dopant activation is ultimately limited by the formation of P-P dimers due to the segregation of dopants between multilayers. By increasing the encapsulation thickness between subsequent layers, thereby minimizing the formation of these deactivating defects, we are able to achieve an active carrier density of ns = 4.5 ×10(14) cm(-2) for a triple layer. The results of electrical characterization are combined with those of secondary ion mass spectroscopy to construct a model that accurately describes the impact of P segregation on the final active carrier density in Si:P multilayers. Our model predicts that a 3D active carrier density of 8.5 × 10(20) cm(-3) (1.7 atom %) can be achieved.

Intracellular Trafficking of Silicon Particles and Logic-Embedded Vectors

PubMed Central

Ferrati, Silvia; Mack, Aaron; Chiappini, Ciro; Liu, Xuewu; Bean, Andrew J.; Ferrari, Mauro; Serda, Rita E.

2010-01-01

Mesoporous silicon particles show great promise for use in drug delivery and imaging applications as carriers for second-stage nanoparticles and higher order particles or therapeutics. Modulation of particle geometry, surface chemistry, and porosity allows silicon particles to be optimized for specific applications such as vascular targeting and avoidance of biological barriers commonly found between the site of drug injection and the final destination. In this study, the intracellular trafficking of unloaded carrier silicon particles and carrier particles loaded with secondary iron oxide nanoparticles was investigated. Following cellular uptake, membrane-encapsulated silicon particles migrated to the perinuclear region of the cell by a microtubule-driven mechanism. Surface charge, shape (spherical and hemispherical) and size (1.6 and 3.2 μm) of the particle did not alter the rate of migration. Maturation of the phagosome was associated with an increase in acidity and acquisition of markers of late endosomes and lysosomes. Cellular uptake of iron oxide nanoparticle-loaded silicon particles resulted in sorting of the particles and trafficking to unique destinations. The silicon carriers remained localized in phagosomes, while the second stage iron oxide nanoparticles were sorted into multi-vesicular bodies that dissociated from the phagosome into novel membrane-bound compartments. Release of iron from the cells may represent exocytosis of iron oxide nanoparticle-loaded vesicles. These results reinforce the concept of multi-functional nanocarriers, in which different particles are able to perform specific tasks, in order to deliver single- or multi-component payloads to specific sub-cellular compartments. PMID:20820744

Development of organic non-flammable spacecraft potting, encapsulating and conformal coating compounds

NASA Technical Reports Server (NTRS)

Lieberman, S. L.

1971-01-01

The overall program objective was to develop a flexible compound which not only functioned in a manned aerospace environment as an effective electrical insulation, but whose flammability characteristics in 16.5 psia, 60% oxygen/40% nitrogen were evidenced by rapid self-extinguishment and minimal thermal (pyrolysis) degradation. The following polymeric matrices were examined in depth: fluoroelastomers, modified fluoroelastomers, silicone RTV's, and modified silicone and fluorosilicone RTV's. Almost none of these systems burned in air, but all burned in 6.2 psia oxygen. Inorganic, organic, and inorganic/organic additives were evaluated in conjunction with these polymers in order to achieve the required survival in the 16.5 psia 60/40 environment. Depending upon formulations, it was possible to achieve nonflammable products when tested in the 1/4 in. x 1/4 in. x 1 in. configuration, even up to and including 16.5 psia oxygen. However, in order to assure this level of flame resistance, it was found necessary to heavily load the matrix with the additives. This resulted in a significant reduction in mechanical properties and large increases in viscosities. Optimization of formulations to obtain a suitable balance between these properties and flammability resistance led to the final selection of Formulation 387 as the primary system.

Graphene Caging Silicon Particles for High-Performance Lithium-Ion Batteries.

PubMed

Nie, Ping; Le, Zaiyuan; Chen, Gen; Liu, Dan; Liu, Xiaoyan; Wu, Hao Bin; Xu, Pengcheng; Li, Xinru; Liu, Fang; Chang, Limin; Zhang, Xiaogang; Lu, Yunfeng

2018-06-01

Silicon holds great promise as an anode material for lithium-ion batteries with higher energy density; its implication, however, is limited by rapid capacity fading. A catalytic growth of graphene cages on composite particles of magnesium oxide and silicon, which are made by magnesiothermic reduction reaction of silica particles, is reported herein. Catalyzed by the magnesium oxide, graphene cages can be conformally grown onto the composite particles, leading to the formation of hollow graphene-encapsulated Si particles. Such materials exhibit excellent lithium storage properties in terms of high specific capacity, remarkable rate capability (890 mAh g -1 at 5 A g -1 ), and good cycling retention over 200 cycles with consistently high coulombic efficiency at a current density of 1 A g -1 . A full battery test using LiCoO 2 as the cathode demonstrates a high energy density of 329 Wh kg -1 . © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Microchannel contacting of crystalline silicon solar cells

DOE PAGES

Bullock, James; Ota, Hiroki; Wang, Hanchen; ...

2017-08-22

There is tremendous interest in reducing losses caused by the metal contacts in silicon photovoltaics, particularly the optical and resistive losses of the front metal grid. One commonly sought-after goal is the creation of high aspect-ratio metal fingers which provide an optically narrow and low resistance pathway to the external circuit. Currently, the most widely used metal contact deposition techniques are limited to widths and aspect-ratios of ~40 μm and ~0.5, respectively. In this study, we introduce the use of a micropatterned polydimethylsiloxane encapsulation layer to form narrow (~20 μm) microchannels, with aspect-ratios up to 8, on the surface ofmore » solar cells. We demonstrate that low temperature metal pastes, electroless plating and atomic layer deposition can all be used within the microchannels. Further, we fabricate proof-of-concept structures including simple planar silicon heterojunction and homojunction solar cells. While preliminary in both design and efficiency, these results demonstrate the potential of this approach and its compatibility with current solar cell architectures.« less

Ultralow-Noise Atomic-Scale Structures for Quantum Circuitry in Silicon.

PubMed

Shamim, Saquib; Weber, Bent; Thompson, Daniel W; Simmons, Michelle Y; Ghosh, Arindam

2016-09-14

The atomically precise doping of silicon with phosphorus (Si:P) using scanning tunneling microscopy (STM) promises ultimate miniaturization of field effect transistors. The one-dimensional (1D) Si:P nanowires are of particular interest, retaining exceptional conductivity down to the atomic scale, and are predicted as interconnects for a scalable silicon-based quantum computer. Here, we show that ultrathin Si:P nanowires form one of the most-stable electrical conductors, with the phenomenological Hooge parameter of low-frequency noise being as low as ≈10(-8) at 4.2 K, nearly 3 orders of magnitude lower than even carbon-nanotube-based 1D conductors. A in-built isolation from the surface charge fluctuations due to encapsulation of the wires within the epitaxial Si matrix is the dominant cause for the observed suppression of noise. Apart from quantum information technology, our results confirm the promising prospects for precision-doped Si:P structures in atomic-scale circuitry for the 11 nm technology node and beyond.

Microchannel contacting of crystalline silicon solar cells

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

Bullock, James; Ota, Hiroki; Wang, Hanchen

There is tremendous interest in reducing losses caused by the metal contacts in silicon photovoltaics, particularly the optical and resistive losses of the front metal grid. One commonly sought-after goal is the creation of high aspect-ratio metal fingers which provide an optically narrow and low resistance pathway to the external circuit. Currently, the most widely used metal contact deposition techniques are limited to widths and aspect-ratios of ~40 μm and ~0.5, respectively. In this study, we introduce the use of a micropatterned polydimethylsiloxane encapsulation layer to form narrow (~20 μm) microchannels, with aspect-ratios up to 8, on the surface ofmore » solar cells. We demonstrate that low temperature metal pastes, electroless plating and atomic layer deposition can all be used within the microchannels. Further, we fabricate proof-of-concept structures including simple planar silicon heterojunction and homojunction solar cells. While preliminary in both design and efficiency, these results demonstrate the potential of this approach and its compatibility with current solar cell architectures.« less

Encapsulating Elastically Stretchable Neural Interfaces: Yield, Resolution, and Recording/Stimulation of Neural Activity

PubMed Central

Morrison, Barclay; Goletiani, Cezar; Yu, Zhe; Wagner, Sigurd

2013-01-01

A high resolution elastically stretchable microelectrode array (SMEA) to interface with neural tissue is described. The SMEA consists of an elastomeric substrate, such as poly(dimethylsiloxane) (PDMS), elastically stretchable gold conductors, and an electrically insulating encapsulating layer in which contact holes are opened. We demonstrate the feasibility of producing contact holes with 40 µm × 40 µm openings, show why the adhesion of the encapsulation layer to the underlying silicone substrate is weakened during contact hole fabrication, and provide remedies. These improvements result in greatly increased fabrication yield and reproducibility. An SMEA with 28 microelectrodes was fabricated. The contact holes (100 µm × 100 µm) in the encapsulation layer are only ~10% the size of the previous generation, allowing a larger number of microelectrodes per unit area, thus affording the capability to interface with a smaller neural population per electrode. This new SMEA is used to record spontaneous and evoked activity in organotypic hippocampal tissue slices at 0% strain before stretching, at 5 % and 10 % equibiaxial strain, and again at 0% strain after relaxation. The noise of the recordings increases with increasing strain. The frequency of spontaneous neural activity also increases when the SMEA is stretched. Upon relaxation, the noise returns to pre-stretch levels, while the frequency of neural activity remains elevated. Stimulus-response curves at each strain level are measured. The SMEA shows excellent biocompatibility for at least two weeks. PMID:24093006

Scanning electron microscopy of chronically implanted intracortical microelectrode arrays in non-human primates

NASA Astrophysics Data System (ADS)

Barrese, James C.; Aceros, Juan; Donoghue, John P.

2016-04-01

Objective. Signal attenuation is a major problem facing intracortical sensors for chronic neuroprosthetic applications. Many studies suggest that failure is due to gliosis around the electrode tips, however, mechanical and material causes of failure are often overlooked. The purpose of this study was to investigate the factors contributing to progressive signal decline by using scanning electron microscopy (SEM) to visualize structural changes in chronically implanted arrays and histology to examine the tissue response at corresponding implant sites. Approach. We examined eight chronically implanted intracortical microelectrode arrays (MEAs) explanted from non-human primates at times ranging from 37 to 1051 days post-implant. We used SEM, in vivo neural recordings, and histology (GFAP, Iba-1, NeuN). Three MEAs that were never implanted were also imaged as controls. Main results. SEM revealed progressive corrosion of the platinum electrode tips and changes to the underlying silicon. The parylene insulation was prone to cracking and delamination, and in some instances the silicone elastomer also delaminated from the edges of the MEA. Substantial tissue encapsulation was observed and was often seen growing into defects in the platinum and parylene. These material defects became more common as the time in vivo increased. Histology at 37 and 1051 days post-implant showed gliosis, disruption of normal cortical architecture with minimal neuronal loss, and high Iba-1 reactivity, especially within the arachnoid and dura. Electrode tracts were either absent or barely visible in the cortex at 1051 days, but were seen in the fibrotic encapsulation material suggesting that the MEAs were lifted out of the brain. Neural recordings showed a progressive drop in impedance, signal amplitude, and viable channels over time. Significance. These results provide evidence that signal loss in MEAs is truly multifactorial. Gliosis occurs in the first few months after implantation but does not prevent useful recordings for several years. Progressive meningeal fibrosis encapsulates and lifts MEAs out of the cortex while ongoing foreign body reactions lead to progressive degradation of the materials. Long-term impedance drops are due to the corrosion of platinum, cracking and delamination of parylene, and delamination of silicone elastomer. Oxygen radicals released by cells of the immune system likely mediate the degradation of these materials. Future MEA designs must address these problems through more durable insulation materials, more inert electrode alloys, and pharmacologic suppression of fibroblasts and leukocytes.

Scanning electron microscopy of chronically implanted intracortical microelectrode arrays in non-human primates

PubMed Central

Barrese, James C; Aceros, Juan; Donoghue, John P

2016-01-01

Objective Signal attenuation is a major problem facing intracortical sensors for chronic neuroprosthetic applications. Many studies suggest that failure is due to gliosis around the electrode tips, however, mechanical and material causes of failure are often overlooked. The purpose of this study was to investigate the factors contributing to progressive signal decline by using scanning electron microscopy (SEM) to visualize structural changes in chronically implanted arrays and histology to examine the tissue response at corresponding implant sites. Approach We examined eight chronically implanted intracortical microelectrode arrays (MEAs) explanted from non-human primates at times ranging from 37 to 1051 days post-implant. We used SEM, in vivo neural recordings, and histology (GFAP, Iba-1, NeuN). Three MEAs that were never implanted were also imaged as controls. Main results SEM revealed progressive corrosion of the platinum electrode tips and changes to the underlying silicon. The parylene insulation was prone to cracking and delamination, and in some instances the silicone elastomer also delaminated from the edges of the MEA. Substantial tissue encapsulation was observed and was often seen growing into defects in the platinum and parylene. These material defects became more common as the time in vivo increased. Histology at 37 and 1051 days post-implant showed gliosis, disruption of normal cortical architecture with minimal neuronal loss, and high Iba-1 reactivity, especially within the arachnoid and dura. Electrode tracts were either absent or barely visible in the cortex at 1051 days, but were seen in the fibrotic encapsulation material suggesting that the MEAs were lifted out of the brain. Neural recordings showed a progressive drop in impedance, signal amplitude, and viable channels over time. Significance These results provide evidence that signal loss in MEAs is truly multifactorial. Gliosis occurs in the first few months after implantation but does not prevent useful recordings for several years. Progressive meningeal fibrosis encapsulates and lifts MEAs out of the cortex while ongoing foreign body reactions lead to progressive degradation of the materials. Long-term impedance drops are due to the corrosion of platinum, cracking and delamination of parylene, and delamination of silicone elastomer. Oxygen radicals released by cells of the immune system likely mediate the degradation of these materials. Future MEA designs must address these problems through more durable insulation materials, more inert electrode alloys, and pharmacologic suppression of fibroblasts and leukocytes. PMID:26824680

Scanning electron microscopy of chronically implanted intracortical microelectrode arrays in non-human primates.

PubMed

Barrese, James C; Aceros, Juan; Donoghue, John P

2016-04-01

Signal attenuation is a major problem facing intracortical sensors for chronic neuroprosthetic applications. Many studies suggest that failure is due to gliosis around the electrode tips, however, mechanical and material causes of failure are often overlooked. The purpose of this study was to investigate the factors contributing to progressive signal decline by using scanning electron microscopy (SEM) to visualize structural changes in chronically implanted arrays and histology to examine the tissue response at corresponding implant sites. We examined eight chronically implanted intracortical microelectrode arrays (MEAs) explanted from non-human primates at times ranging from 37 to 1051 days post-implant. We used SEM, in vivo neural recordings, and histology (GFAP, Iba-1, NeuN). Three MEAs that were never implanted were also imaged as controls. SEM revealed progressive corrosion of the platinum electrode tips and changes to the underlying silicon. The parylene insulation was prone to cracking and delamination, and in some instances the silicone elastomer also delaminated from the edges of the MEA. Substantial tissue encapsulation was observed and was often seen growing into defects in the platinum and parylene. These material defects became more common as the time in vivo increased. Histology at 37 and 1051 days post-implant showed gliosis, disruption of normal cortical architecture with minimal neuronal loss, and high Iba-1 reactivity, especially within the arachnoid and dura. Electrode tracts were either absent or barely visible in the cortex at 1051 days, but were seen in the fibrotic encapsulation material suggesting that the MEAs were lifted out of the brain. Neural recordings showed a progressive drop in impedance, signal amplitude, and viable channels over time. These results provide evidence that signal loss in MEAs is truly multifactorial. Gliosis occurs in the first few months after implantation but does not prevent useful recordings for several years. Progressive meningeal fibrosis encapsulates and lifts MEAs out of the cortex while ongoing foreign body reactions lead to progressive degradation of the materials. Long-term impedance drops are due to the corrosion of platinum, cracking and delamination of parylene, and delamination of silicone elastomer. Oxygen radicals released by cells of the immune system likely mediate the degradation of these materials. Future MEA designs must address these problems through more durable insulation materials, more inert electrode alloys, and pharmacologic suppression of fibroblasts and leukocytes.

Fabrication and characterization of resonant SOI micromechanical silicon sensors based on DRIE micromachining, freestanding release process and silicon direct bonding

NASA Astrophysics Data System (ADS)

Gigan, Olivier; Chen, Hua; Robert, Olivier; Renard, Stephane; Marty, Frederic

2002-11-01

This paper is dedicated to the fabrication and technological aspect of a silicon microresonator sensor. The entire project includes the fabrication processes, the system modelling/simulation, and the electronic interface. The mechanical model of such resonator is presented including description of frequency stability and Hysterises behaviour of the electrostatically driven resonator. Numeric model and FEM simulations are used to simulate the system dynamic behaviour. The complete fabrication process is based on standard microelectronics technology with specific MEMS technological steps. The key steps are described: micromachining on SOI by Deep Reactive Ion Etching (DRIE), specific release processes to prevent sticking (resist and HF-vapour release process) and collective vacuum encapsulation by Silicon Direct Bonding (SDB). The complete process has been validated and prototypes have been fabricated. The ASIC was designed to interface the sensor and to control the vibration amplitude. This electronic was simulated and designed to work up to 200°C and implemented in a standard 0.6μ CMOS technology. Characterizations of sensor prototypes are done both mechanically and electrostatically. These measurements showed good agreements with theory and FEM simulations.

Ultralow-mass solar-array designs for Halley's comet rendezvous mission

NASA Technical Reports Server (NTRS)

Costogue, E. N.; Rayl, G.

1978-01-01

This paper describes the conceptual design study results of photovoltaic arrays capable of powering a Halley's comet rendezvous mission. This mission would be Shuttle-launched, employ a unique form of propulsion (ion drive) which requires high power levels for operation, and operate at distances between 0.6 and 4.5 AU. These requirements make it necessary to develop arrays with extremely high power-to-mass ratio (200 W/kg). In addition, the dual requirements of providing ion thruster power as well as housekeeping power leads to the development of unique methods for mode switching. Both planar and variable-concentrator-enhanced array concepts using ultrathin (50 micron) high-efficiency (up to 12.5%) silicon solar cells coupled with thin (75 micron) plastic encapsulants are considered. In order to satisfy the Shuttle launch environment it was necessary to provide novel methods of both storing and deploying these arrays.

A Study on Organic-Metal Halide Perovskite Film Morphology, Interfacial Layers, Tandem Applications, and Encapsulation

NASA Astrophysics Data System (ADS)

Fisher, Dallas A.

Organic-metal halide perovskites have brought about a new wave of research in the photovoltaic community due to their ideally suited optical and electronic parameters. In less than a decade, perovskite solar cell performance has skyrocketed to unprecedented efficiencies with numerous reported methodologies. Perovskites face many challenges with high-quality film morphology, interfacial layers, and long-term stability. In this work, these active areas are explored through a combination of studies. First, the importance of perovskite film precursor ratios is explored with an in-depth study of carrier lifetime and solvent-grain effects. It was found that excess lead iodide precursor greatly improves the film morphology by reducing pinholes in the solar absorber. Dimethyl sulfoxide (DMSO) solvent was found to mend grains, as well as improve carrier lifetime and device performance, possibly by passivation of grain boundary traps. Second, applications of perovskite with tandem cells is investigated, with an emphasis for silicon devices. Perovskites can easily be integrated with silicon, which already has strong market presence. Additionally, both materials' bandgaps are ideally suited for maximum tandem efficiency. The silicon/perovskite tandem device structure necessitated the optimization of inverted (p-i-n) structure devices. PEDOT:PSS, copper oxide, and nickel oxide p-type layers were explored through a combination of photoluminescent, chemical reactivity, and solar simulation results. Results were hindered due to resistive ITO and rough silicon substrates, but tandem devices displayed Voc indicative of proper monolithic performance. Third, replacement of titanium dioxide n-type layer with iron oxide (Fe 2O3, common rust) was studied. Iron oxide experiences less ultraviolet instability than that of titanium dioxide under solar illumination. It was found that current density slightly decreased due to parasitic absorption from the rust, but that open circuit voltage decreased drastically due to poor band alignment. Fe2O3 appears to be better suited to a narrower band gap material than methylammonium lead iodide perovskite. Finally, encapsulation of perovskite devices with epoxy coatings is explored as a method to improve long-term stability. Perovskites are sensitive to a variety of conditions, but most importantly water and polar molecules. Encapsulants act as a moisture/oxygen barrier, but also prevent outgassing of the organic components. Three epoxies were tested in high heat and high humidity conditions. Important factors in the curing process were uncovered such as the sensitivity of UV-epoxies to amine functional groups found in common p-type dopants and perovskite layers. Moisture ingress was the failure point for high-humidity/heat devices which was confirmed through conversion to yellow lead iodide. A revised device fabrication method is proposed to reduce moisture ingress for future experiments.

Silicon solar cells with a total power capacity of 30 kilowatts

NASA Technical Reports Server (NTRS)

1977-01-01

The bulk of the contract effort was carried out in the following two phases: Phase 1 -- module design, Pre-production module fabrication, inspection and test. Phase 2 -- Production, test and delivery. Effort during the first two months of the contract concentrated on design of a solar module to meet specification. Basic module design resulting from this effort is as follows: (1) frame design; (2) cell pan design; (3) cell interconnection; (4) encapsulation; (5) electrical performance.

Encapsulation of single cells on a microfluidic device integrating droplet generation with fluorescence-activated droplet sorting.

PubMed

Wu, Liang; Chen, Pu; Dong, Yingsong; Feng, Xiaojun; Liu, Bi-Feng

2013-06-01

Encapsulation of single cells is a challenging task in droplet microfluidics due to the random compartmentalization of cells dictated by Poisson statistics. In this paper, a microfluidic device was developed to improve the single-cell encapsulation rate by integrating droplet generation with fluorescence-activated droplet sorting. After cells were loaded into aqueous droplets by hydrodynamic focusing, an on-flight fluorescence-activated sorting process was conducted to isolate droplets containing one cell. Encapsulation of fluorescent polystyrene beads was investigated to evaluate the developed method. A single-bead encapsulation rate of more than 98 % was achieved under the optimized conditions. Application to encapsulate single HeLa cells was further demonstrated with a single-cell encapsulation rate of 94.1 %, which is about 200 % higher than those obtained by random compartmentalization. We expect this new method to provide a useful platform for encapsulating single cells, facilitating the development of high-throughput cell-based assays.

Encapsulated high frequency (235 kHz), high-Q (100 k) disk resonator gyroscope with electrostatic parametric pump

NASA Astrophysics Data System (ADS)

Ahn, C. H.; Nitzan, S.; Ng, E. J.; Hong, V. A.; Yang, Y.; Kimbrell, T.; Horsley, D. A.; Kenny, T. W.

2014-12-01

In this paper, we explore the effects of electrostatic parametric amplification on a high quality factor (Q > 100 000) encapsulated disk resonator gyroscope (DRG), fabricated in <100> silicon. The DRG was operated in the n = 2 degenerate wineglass mode at 235 kHz, and electrostatically tuned so that the frequency split between the two degenerate modes was less than 100 mHz. A parametric pump at twice the resonant frequency is applied to the sense axis of the DRG, resulting in a maximum scale factor of 156.6 μV/(°/s), an 8.8× improvement over the non-amplified performance. When operated with a parametric gain of 5.4, a minimum angle random walk of 0.034°/√h and bias instability of 1.15°/h are achieved, representing an improvement by a factor of 4.3× and 1.5×, respectively.

Encapsulated liquid sorbents for carbon dioxide capture

NASA Astrophysics Data System (ADS)

Vericella, John J.; Baker, Sarah E.; Stolaroff, Joshuah K.; Duoss, Eric B.; Hardin, James O.; Lewicki, James; Glogowski, Elizabeth; Floyd, William C.; Valdez, Carlos A.; Smith, William L.; Satcher, Joe H.; Bourcier, William L.; Spadaccini, Christopher M.; Lewis, Jennifer A.; Aines, Roger D.

2015-02-01

Drawbacks of current carbon dioxide capture methods include corrosivity, evaporative losses and fouling. Separating the capture solvent from infrastructure and effluent gases via microencapsulation provides possible solutions to these issues. Here we report carbon capture materials that may enable low-cost and energy-efficient capture of carbon dioxide from flue gas. Polymer microcapsules composed of liquid carbonate cores and highly permeable silicone shells are produced by microfluidic assembly. This motif couples the capacity and selectivity of liquid sorbents with high surface area to facilitate rapid and controlled carbon dioxide uptake and release over repeated cycles. While mass transport across the capsule shell is slightly lower relative to neat liquid sorbents, the surface area enhancement gained via encapsulation provides an order-of-magnitude increase in carbon dioxide absorption rates for a given sorbent mass. The microcapsules are stable under typical industrial operating conditions and may be used in supported packing and fluidized beds for large-scale carbon capture.

Ultra-low-mass flexible planar solar arrays using 50-micron-thick solar cells

NASA Technical Reports Server (NTRS)

Costogue, E. N.; Rayl, G.

1978-01-01

A conceptual design study has been completed which has shown the feasibility of ultra-low-mass planar solar arrays with specific power of 200 watts/kilogram. The beginning of life (BOL) power output of the array designs would be 10 kW at 1 astronomical unit (AU) and a 55C deg operating temperature. Two designs were studied: a retractable rollout design and a non-retractable fold-out. The designs employed a flexible low-mass blanket and low-mass structures. The blanket utilized 2 x 2 cm high-efficiency (13.5% at 28C deg AM0), ultra-thin (50 micron), silicon solar cells protected by thin (75 micron) plastic encapsulants. The structural design utilized the 'V'-stiffened approach which allows a lower mass boom to be used. In conjunction with the conceptual design, modules using the thin cells and plastic encapsulant were designed and fabricated.

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

Pern, F. J.; Glick, S. H.

We have conducted a series of accelerated exposure test (AET) studies for various crystalline-Si (c-Si) and amorphous-Si (a-Si) cell samples that were encapsulated with different superstrates, pottants, and substrates. Nonuniform browning patterns of ethylene vinyl acetate (EVA) pottants were observed for glass/EVA/glass-encapsulated c-Si cell samples under solar simulator exposures at elevated temperatures. The polymer/polymer-configured laminates with Tedlar or Tefzel did not discolor because of photobleaching reactions, but yellowed with polyester or nylon top films. Delamination was observed for the polyester/EVA layers on a-Si minimodules and for a polyolefin-based thermoplastic pottant at high temperatures. For all tested c-Si cell samples, irregularmore » changes in the current-voltage parameters were observed that could not be accounted for simply by the transmittance changes of the superstrate/pottant layers. Silicone-type adhesives used under UV-transmitting polymer top films were observed to cause greater cell current/efficiency loss than EVA or polyethylene pottants.« less

Optical design for reliability and efficiency in concentrating photovoltaics

NASA Astrophysics Data System (ADS)

Leutz, Ralf; Annen, Hans Philipp; Fu, Ling

2010-08-01

Complex systems like modules in concentrating photovoltaics (CPV) are designed in a systems approach. The better the components are concerted, the better the performance goals of the system can be fulfilled. Optics are central to the CPV module's reliability and efficiency. Fresnel lens optics provide the module cover, and protect the module against the environment. Fresnel lenses on glass can provide the module's structural integrity. The secondary optical element, used to increase the collection of light, the acceptance half-angle, and the uniformity on the cell, may provide encapsulation for the receiver. This encapsulation function may be provided by some optical designs in sol gel, or silicone. Both materials are unknown in their longevity in this application. We present optical designs fulfilling structural or protective functions, discuss the optical penalties to be paid, and the innovative materials and manufacturing technologies to be tested.

3D‐Bioprinted Osteoblast‐Laden Nanocomposite Hydrogel Constructs with Induced Microenvironments Promote Cell Viability, Differentiation, and Osteogenesis both In Vitro and In Vivo

PubMed Central

Zhai, Xinyun; Ma, Yufei; Cheng, Delin; Wu, Mingming; Liu, Wenguang; Zhao, Xiaoli

2017-01-01

Abstract An osteoblast‐laden nanocomposite hydrogel construct, based on polyethylene glycol diacrylate (PEGDA)/laponite XLG nanoclay ([Mg5.34Li0.66Si8O20(OH)4]Na0.66, clay)/hyaluronic acid sodium salt (HA) bio‐inks, is developed by a two‐channel 3D bioprinting method. The novel biodegradable bio‐ink A, comprised of a poly(ethylene glycol) (PEG)–clay nanocomposite crosslinked hydrogel, is used to facilitate 3D‐bioprinting and enables the efficient delivery of oxygen and nutrients to growing cells. HA with encapsulated primary rat osteoblasts (ROBs) is applied as bio‐ink B with a view to improving cell viability, distribution uniformity, and deposition efficiency. The cell‐laden PEG–clay constructs not only encapsulated osteoblasts with more than 95% viability in the short term but also exhibited excellent osteogenic ability in the long term, due to the release of bioactive ions (magnesium ions, Mg2+ and silicon ions, Si4+), which induces the suitable microenvironment to promote the differentiation of the loaded exogenous ROBs, both in vitro and in vivo. This 3D‐bioprinting method holds much promise for bone tissue regeneration in terms of cell engraftment, survival, and ultimately long‐term function. PMID:29593958

Microfluidic Assembly of a Multifunctional Tailorable Composite System Designed for Site Specific Combined Oral Delivery of Peptide Drugs.

PubMed

Araújo, Francisca; Shrestha, Neha; Shahbazi, Mohammad-Ali; Liu, Dongfei; Herranz-Blanco, Bárbara; Mäkilä, Ermei M; Salonen, Jarno J; Hirvonen, Jouni T; Granja, Pedro L; Sarmento, Bruno; Santos, Hélder A

2015-08-25

Multifunctional tailorable composite systems, specifically designed for oral dual-delivery of a peptide (glucagon-like peptide-1) and an enzymatic inhibitor (dipeptidyl peptidase 4 (DPP4)), were assembled through the microfluidics technique. Both drugs were coloaded into these systems for a synergistic therapeutic effect. The systems were composed of chitosan and cell-penetrating peptide modified poly(lactide-co-glycolide) and porous silicon nanoparticles as nanomatrices, further encapsulated in an enteric hydroxypropylmethylcellulose acetylsuccinate polymer. The developed multifunctional systems were pH-sensitive, inherited by the enteric polymer, enabling the release of the nanoparticles only in the simulated intestinal conditions. Moreover, the encapsulation into this polymer prevented the degradation of the nanoparticles' modifications. These nanoparticles showed strong and higher interactions with the intestinal cells in comparison with the nonmodified ones. The presence of DPP4 inhibitor enhanced the peptide permeability across intestinal cell monolayers. Overall, this is a promising platform for simultaneously delivering two drugs from a single formulation. Through this approach peptides are expected to increase their bioavailability and efficiency in vivo both by their specific release at the intestinal level and also by the reduced enzymatic activity. The use of this platform, specifically in combination of the two antidiabetic drugs, has clinical potential for the therapy of type 2 diabetes mellitus.

Conception, fabrication and characterization of a silicon based MEMS inertial switch with a threshold value of 5 g

NASA Astrophysics Data System (ADS)

Zhang, Fengtian; Wang, Chao; Yuan, Mingquan; Tang, Bin; Xiong, Zhuang

2017-12-01

Most of the MEMS inertial switches developed in recent years are intended for shock and impact sensing with a threshold value above 50 g. In order to follow the requirement of detecting linear acceleration signal at low-g level, a silicon based MEMS inertial switch with a threshold value of 5 g was designed, fabricated and characterized. The switch consisted of a large proof mass, supported by circular spiral springs. An analytical model of the structure stiffness of the proposed switch was derived and verified by finite-element simulation. The structure fabrication was based on a customized double-buried layer silicon-on-insulator wafer and encapsulated by glass wafers. The centrifugal experiment and nanoindentation experiment were performed to measure the threshold value as well as the structure stiffness. The actual threshold values were measured to be 0.1-0.3 g lower than the pre-designed value of 5 g due to the dimension loss during non-contact lithography processing. Concerning the reliability assessment, a series of environmental experiments were conducted and the switches remained operational without excessive errors. However, both the random vibration and the shock tests indicate that the metal particles generated during collision of contact parts might affect the contact reliability and long-time stability. According to the conclusion reached in this report, an attentive study on switch contact behavior should be included in future research.

Dendrimer-encapsulated naphthalocyanine as a single agent-based theranostic nanoplatform for near-infrared fluorescence imaging and combinatorial anticancer phototherapy

NASA Astrophysics Data System (ADS)

Taratula, Olena; Schumann, Canan; Duong, Tony; Taylor, Karmin L.; Taratula, Oleh

2015-02-01

Multifunctional theranostic platforms capable of concurrent near-infrared (NIR) fluorescence imaging and phototherapies are strongly desired for cancer diagnosis and treatment. However, the integration of separate imaging and therapeutic components into nanocarriers results in complex theranostic systems with limited translational potential. A single agent-based theranostic nanoplatform, therefore, was developed for concurrent NIR fluorescence imaging and combinatorial phototherapy with dual photodynamic (PDT) and photothermal (PTT) therapeutic mechanisms. The transformation of a substituted silicon naphthalocyanine (SiNc) into a biocompatible nanoplatform (SiNc-NP) was achieved by SiNc encapsulation into the hydrophobic interior of a generation 5 polypropylenimine dendrimer following surface modification with polyethylene glycol. Encapsulation provides aqueous solubility to SiNc and preserves its NIR fluorescence, PDT and PTT properties. Moreover, an impressive photostability in the dendrimer-encapsulated SiNc has been detected. Under NIR irradiation (785 nm, 1.3 W cm-2), SiNc-NP manifested robust heat generation capability (ΔT = 40 °C) and efficiently produced reactive oxygen species essential for PTT and PDT, respectively, without releasing SiNc from the nanopaltform. By varying the laser power density from 0.3 W cm-2 to 1.3 W cm-2 the therapeutic mechanism of SiNc-NP could be switched from PDT to combinatorial PDT-PTT treatment. In vitro and in vivo studies confirmed that phototherapy mediated by SiNc can efficiently destroy chemotherapy resistant ovarian cancer cells. Remarkably, solid tumors treated with a single dose of SiNc-NP combined with NIR irradiation were completely eradicated without cancer recurrence. Finally, the efficiency of SiNc-NP as an NIR imaging agent was confirmed by recording the strong fluorescence signal in the tumor, which was not photobleached during the phototherapeutic procedure.Multifunctional theranostic platforms capable of concurrent near-infrared (NIR) fluorescence imaging and phototherapies are strongly desired for cancer diagnosis and treatment. However, the integration of separate imaging and therapeutic components into nanocarriers results in complex theranostic systems with limited translational potential. A single agent-based theranostic nanoplatform, therefore, was developed for concurrent NIR fluorescence imaging and combinatorial phototherapy with dual photodynamic (PDT) and photothermal (PTT) therapeutic mechanisms. The transformation of a substituted silicon naphthalocyanine (SiNc) into a biocompatible nanoplatform (SiNc-NP) was achieved by SiNc encapsulation into the hydrophobic interior of a generation 5 polypropylenimine dendrimer following surface modification with polyethylene glycol. Encapsulation provides aqueous solubility to SiNc and preserves its NIR fluorescence, PDT and PTT properties. Moreover, an impressive photostability in the dendrimer-encapsulated SiNc has been detected. Under NIR irradiation (785 nm, 1.3 W cm-2), SiNc-NP manifested robust heat generation capability (ΔT = 40 °C) and efficiently produced reactive oxygen species essential for PTT and PDT, respectively, without releasing SiNc from the nanopaltform. By varying the laser power density from 0.3 W cm-2 to 1.3 W cm-2 the therapeutic mechanism of SiNc-NP could be switched from PDT to combinatorial PDT-PTT treatment. In vitro and in vivo studies confirmed that phototherapy mediated by SiNc can efficiently destroy chemotherapy resistant ovarian cancer cells. Remarkably, solid tumors treated with a single dose of SiNc-NP combined with NIR irradiation were completely eradicated without cancer recurrence. Finally, the efficiency of SiNc-NP as an NIR imaging agent was confirmed by recording the strong fluorescence signal in the tumor, which was not photobleached during the phototherapeutic procedure. Electronic supplementary information (ESI) available: Fig. S1-S5: Size distribution of SiNc-NP measured by dynamic light scattering (Fig. S1); absorption spectra of free SiNc 2 in THF before and after irradiation with the 785 nm laser diode for 30 min (Fig. S2); in vitro cytotoxicity of free DOX against A2780/AD human ovarian cancer cells (Fig. S3); the release profiles of SiNc from SiNc-NP under various conditions (Fig. S4); body weight curves of the mice with or without treatment (Fig. S5). See DOI: 10.1039/c4nr06050d

EFG solar modules

NASA Technical Reports Server (NTRS)

1978-01-01

Six photovoltaic modules using solar cells fabricated from silicon ribbons were assembled and delivered to JPL. Each module was comprised of four separate submodules which were parallel connected. The submodules contained 45 EFG cells which were series interconnected by a shingle or overlapping design. The inherent rectangular shape of the cells allowed a high packing factor to be achieved. The average efficiency of the six modules, corrected to AM1 at 28 C was 8.7%, which indicates that the average encapsulated cell efficiency was 10.0%.

Biodegradable elastomers and silicon nanomembranes/nanoribbons for stretchable, transient electronics, and biosensors.

PubMed

Hwang, Suk-Won; Lee, Chi Hwan; Cheng, Huanyu; Jeong, Jae-Woong; Kang, Seung-Kyun; Kim, Jae-Hwan; Shin, Jiho; Yang, Jian; Liu, Zhuangjian; Ameer, Guillermo A; Huang, Yonggang; Rogers, John A

2015-05-13

Transient electronics represents an emerging class of technology that exploits materials and/or device constructs that are capable of physically disappearing or disintegrating in a controlled manner at programmed rates or times. Inorganic semiconductor nanomaterials such as silicon nanomembranes/nanoribbons provide attractive choices for active elements in transistors, diodes and other essential components of overall systems that dissolve completely by hydrolysis in biofluids or groundwater. We describe here materials, mechanics, and design layouts to achieve this type of technology in stretchable configurations with biodegradable elastomers for substrate/encapsulation layers. Experimental and theoretical results illuminate the mechanical properties under large strain deformation. Circuit characterization of complementary metal-oxide-semiconductor inverters and individual transistors under various levels of applied loads validates the design strategies. Examples of biosensors demonstrate possibilities for stretchable, transient devices in biomedical applications.

Towards stable silicon nanoarray hybrid solar cells.

PubMed

He, W W; Wu, K J; Wang, K; Shi, T F; Wu, L; Li, S X; Teng, D Y; Ye, C H

2014-01-16

Silicon nanoarray hybrid solar cells benefit from the ease of fabrication and the cost-effectiveness of the hybrid structure, and represent a new research focus towards the utilization of solar energy. However, hybrid solar cells composed of both inorganic and organic components suffer from the notorious stability issue, which has to be tackled before the hybrid solar cells could become a viable alternative for harvesting solar energy. Here we show that Si nanoarray/PEDOT:PSS hybrid solar cells with improved stability can be fabricated via eliminating the water inclusion in the initial formation of the heterojunction between Si nanoarray and PEDOT:PSS. The Si nanoarray hybrid solar cells are stable against rapid degradation in the atmosphere environment for several months without encapsulation. This finding paves the way towards the real-world applications of Si nanoarray hybrid solar cells.

Nondestructive X-ray diffraction measurement of warpage in silicon dies embedded in integrated circuit packages.

PubMed

Tanner, B K; Danilewsky, A N; Vijayaraghavan, R K; Cowley, A; McNally, P J

2017-04-01

Transmission X-ray diffraction imaging in both monochromatic and white beam section mode has been used to measure quantitatively the displacement and warpage stress in encapsulated silicon devices. The displacement dependence with position on the die was found to agree well with that predicted from a simple model of warpage stress. For uQFN microcontrollers, glued only at the corners, the measured misorientation contours are consistent with those predicted using finite element analysis. The absolute displacement, measured along a line through the die centre, was comparable to that reported independently by high-resolution X-ray diffraction and optical interferometry of similar samples. It is demonstrated that the precision is greater than the spread of values found in randomly selected batches of commercial devices, making the techniques viable for industrial inspection purposes.

Engineering empty space between Si nanoparticles for lithium-ion battery anodes.

PubMed

Wu, Hui; Zheng, Guangyuan; Liu, Nian; Carney, Thomas J; Yang, Yuan; Cui, Yi

2012-02-08

Silicon is a promising high-capacity anode material for lithium-ion batteries yet attaining long cycle life remains a significant challenge due to pulverization of the silicon and unstable solid-electrolyte interphase (SEI) formation during the electrochemical cycles. Despite significant advances in nanostructured Si electrodes, challenges including short cycle life and scalability hinder its widespread implementation. To address these challenges, we engineered an empty space between Si nanoparticles by encapsulating them in hollow carbon tubes. The synthesis process used low-cost Si nanoparticles and electrospinning methods, both of which can be easily scaled. The empty space around the Si nanoparticles allowed the electrode to successfully overcome these problems Our anode demonstrated a high gravimetric capacity (~1000 mAh/g based on the total mass) and long cycle life (200 cycles with 90% capacity retention). © 2012 American Chemical Society

Towards stable silicon nanoarray hybrid solar cells

PubMed Central

He, W. W.; Wu, K. J.; Wang, K.; Shi, T. F.; Wu, L.; Li, S. X.; Teng, D. Y.; Ye, C. H.

2014-01-01

Silicon nanoarray hybrid solar cells benefit from the ease of fabrication and the cost-effectiveness of the hybrid structure, and represent a new research focus towards the utilization of solar energy. However, hybrid solar cells composed of both inorganic and organic components suffer from the notorious stability issue, which has to be tackled before the hybrid solar cells could become a viable alternative for harvesting solar energy. Here we show that Si nanoarray/PEDOT:PSS hybrid solar cells with improved stability can be fabricated via eliminating the water inclusion in the initial formation of the heterojunction between Si nanoarray and PEDOT:PSS. The Si nanoarray hybrid solar cells are stable against rapid degradation in the atmosphere environment for several months without encapsulation. This finding paves the way towards the real-world applications of Si nanoarray hybrid solar cells. PMID:24430057

Bending cyclic load test for crystalline silicon photovoltaic modules

NASA Astrophysics Data System (ADS)

Suzuki, Soh; Doi, Takuya; Masuda, Atsushi; Tanahashi, Tadanori

2018-02-01

The failures induced by thermomechanical fatigue within crystalline silicon photovoltaic modules are a common issue that can occur in any climate. In order to understand these failures, we confirmed the effects of compressive or tensile stresses (which were cyclically loaded on photovoltaic cells and cell interconnect ribbons) at subzero, moderate, and high temperatures. We found that cell cracks were induced predominantly at low temperatures, irrespective of the compression or tension applied to the cells, although the orientation of cell cracks was dependent on the stress applied. The fracture of cell interconnect ribbons was caused by cyclical compressive stress at moderate and high temperatures, and this failure was promoted by the elevation of temperature. On the basis of these results, the causes of these failures are comprehensively discussed in relation to the viscoelasticity of the encapsulant.

Anhydrous polymer-based coating with sustainable controlled release functionality for facile, efficacious impregnation, and delivery of antimicrobial peptides.

PubMed

Lim, Kaiyang; Saravanan, Rathi; Chong, Kelvin K L; Goh, Sharon H M; Chua, Ray R Y; Tambyah, Paul A; Chang, Matthew W; Kline, Kimberly A; Leong, Susanna S J

2018-04-17

Anhydrous polymers are actively explored as alternative materials to overcome limitations of conventional hydrogel-based antibacterial coating. However, the requirement for strong organic solvent in polymerization reactions often necessitates extra protection steps for encapsulation of target biomolecules, lowering encapsulation efficiency, and increasing process complexity. This study reports a novel coating strategy that allows direct solvation and encapsulation of antimicrobial peptides (HHC36) into anhydrous polycaprolactone (PCL) polymer-based dual layer coating. A thin 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) film is layered onto the peptide-impregnated PCL as a diffusion barrier, to modulate and enhance release kinetics. The impregnated peptides are eventually released in a controlled fashion. The use of 2,2,2-trifluoroethanol (TFE), as polymerization and solvation medium, induces the impregnated peptides to adopt highly stable turned conformation, conserving peptide integrity, and functionality during both encapsulation and subsequent release processes. The dual layer coating showed sustained antibacterial functionality, lasting for 14 days. In vivo assessment using an experimental mouse wounding model demonstrated good biocompatibility and significant antimicrobial efficacy of the coating under physiological conditions. The coating was translated onto silicone urinary catheters and showed promising antibacterial efficacy, even outperforming commercial silver-based Dover cather. This anhydrous polymer-based platform holds immense potential as an effective antibacterial coating to prevent clinical device-associated infections. The simplicity of the coating process enhances its industrial viability. © 2018 Wiley Periodicals, Inc.

Deployable aerospace PV array based on amorphous silicon alloys

NASA Technical Reports Server (NTRS)

Hanak, Joseph J.; Walter, Lee; Dobias, David; Flaisher, Harvey

1989-01-01

The development of the first commercial, ultralight, flexible, deployable, PV array for aerospace applications is discussed. It is based on thin-film, amorphous silicon alloy, multijunction, solar cells deposited on a thin metal or polymer by a proprietary, roll-to-roll process. The array generates over 200 W at AM0 and is made of 20 giant cells, each 54 cm x 29 cm (1566 sq cm in area). Each cell is protected with bypass diodes. Fully encapsulated array blanket and the deployment mechanism weigh about 800 and 500 g, respectively. These data yield power per area ratio of over 60 W/sq m specific power of over 250 W/kg (4 kg/kW) for the blanket and 154 W/kg (6.5 kg/kW) for the power system. When stowed, the array is rolled up to a diameter of 7 cm and a length of 1.11 m. It is deployed quickly to its full area of 2.92 m x 1.11 m, for instant power. Potential applications include power for lightweight space vehicles, high altitude balloons, remotely piloted and tethered vehicles. These developments signal the dawning of a new age of lightweight, deployable, low-cost space arrays in the range from tens to tens of thousands of watts for near-term applications and the feasibility of multi-100 kW to MW arrays for future needs.

Deployable aerospace PV array based on amorphous silicon alloys

NASA Astrophysics Data System (ADS)

Hanak, Joseph J.; Walter, Lee; Dobias, David; Flaisher, Harvey

1989-04-01

The development of the first commercial, ultralight, flexible, deployable, PV array for aerospace applications is discussed. It is based on thin-film, amorphous silicon alloy, multijunction, solar cells deposited on a thin metal or polymer by a proprietary, roll-to-roll process. The array generates over 200 W at AM0 and is made of 20 giant cells, each 54 cm x 29 cm (1566 sq cm in area). Each cell is protected with bypass diodes. Fully encapsulated array blanket and the deployment mechanism weigh about 800 and 500 g, respectively. These data yield power per area ratio of over 60 W/sq m specific power of over 250 W/kg (4 kg/kW) for the blanket and 154 W/kg (6.5 kg/kW) for the power system. When stowed, the array is rolled up to a diameter of 7 cm and a length of 1.11 m. It is deployed quickly to its full area of 2.92 m x 1.11 m, for instant power. Potential applications include power for lightweight space vehicles, high altitude balloons, remotely piloted and tethered vehicles. These developments signal the dawning of a new age of lightweight, deployable, low-cost space arrays in the range from tens to tens of thousands of watts for near-term applications and the feasibility of multi-100 kW to MW arrays for future needs.

Long-Term Stability of Mold Compounds and the Influence on Semiconductor Device Reliability

NASA Astrophysics Data System (ADS)

Mahler, Joachim; Mengel, Manfred

2012-07-01

Lifetimes of semiconductor devices are specified according to the products and their applications to ensure safe operation, for instance as part of an automobile product. The long-term stability of the device is strongly dependent on the chip encapsulation and its adhesion to the chip and substrate. Molded silicon strips that act as a model system for molded chips inside semiconductor devices were investigated. Four commercially available mold compounds were applied on silicon strips and stored over 5 years at room temperature (RT), and changes in the thermomechanical behavior were analyzed. After storage, all molded strips exhibited warpage reduction in the range of 11% to 14% at RT with respect to the initial warpage. The temperatures for the stress-free state also changed during storage and were located between 228°C and 235°C for each mold. Additional stress applied to the stored modules, by temperature cycling as well as high-temperature storage, increased the warpage of the molded silicon samples. For further interpretation of measured results, finite-element method calculations were performed.

Design and fabrication of a foldable 3D silicon based package for solid state lighting applications

NASA Astrophysics Data System (ADS)

Sokolovskij, R.; Liu, P.; van Zeijl, H. W.; Mimoun, B.; Zhang, G. Q.

2015-05-01

Miniaturization of solid state lighting (SSL) luminaires as well as reduction of packaging and assembly costs are of prime interest for the SSL lighting industry. A novel silicon based LED package for lighting applications is presented in this paper. The proposed design consists of 5 rigid Si tiles connected by flexible polyimide hinges with embedded interconnects (ICs). Electrical, optical and thermal characteristics were taken into consideration during design. The fabrication process involved polyimide (PI) application and patterning, aluminium interconnect integration in the flexible hinge, LED reflector cavity formation and metalization followed by through wafer DRIE etching for chip formation and release. A method to connect chip front to backside without TSVs was also integrated into the process. Post-fabrication wafer level assembly included LED mounting and wirebond, phosphor-based colour conversion and silicone encapsulation. The package formation was finalized by vacuum assisted wrapping around an assembly structure to form a 3D geometry, which is beneficial for omnidirectional lighting. Bending tests were performed on the flexible ICs and optical performance at different temperatures was evaluated. It is suggested that 3D packages can be expanded to platforms for miniaturized luminaire applications by combining monolithic silicon integration and system-in-package (SiP) technologies.

Issues deserve attention in encapsulating probiotics: Critical review of existing literature.

PubMed

Chen, Jun; Wang, Qi; Liu, Cheng-Mei; Gong, Joshua

2017-04-13

Probiotic bacteria are being increasingly added to food for developing products with health-promoting properties. However, the efficacy of probiotics in commercial products is often questioned due to the loss of their viability during shelf storage and in human gastrointestinal tracts. Encapsulation of probiotics has been expected to provide protection to probiotics, but not many commercial products contain encapsulated and viable probiotic cells owing to various reasons. To promote the development and application of encapsulation technologies, this paper has critically reviewed previous publications with a focus on the areas where studies have fallen short, including insufficient consideration of structural effects of encapsulating material, general defects in encapsulating methods and issues in evaluation methodologies and risk assessments for application. Corresponding key issues that require further studies are highlighted. Some emerging trends in the field, such as current treads in encapsulating material and recently advanced encapsulation techniques, have also been discussed.

Flat-plate solar array project. Volume 7: Module encapsulation

NASA Astrophysics Data System (ADS)

Cuddihy, E.; Coulbert, C.; Gupta, A.; Liang, R.

1986-10-01

The objective of the Encapsulation Task was to develop, demonstrate, and qualify photovoltaic (PV) module encapsulation systems that would provide 20 year (later decreased to 30 year) life expectancies in terrestrial environments, and which would be compatible with the cost and performance goals of the Flat-Plate Solar Array (FSA) Project. The scope of the Encapsulation Task included the identification, development, and evaluation of material systems and configurations required to support and protect the optically and electrically active solar cell circuit components in the PV module operating environment. Encapsulation material technologies summarized include the development of low cost ultraviolet protection techniques, stable low cost pottants, soiling resistant coatings, electrical isolation criteria, processes for optimum interface bonding, and analytical and experimental tools for evaluating the long term durability and structural adequacy of encapsulated modules. Field testing, accelerated stress testing, and design studies have demonstrated that encapsulation materials, processes, and configurations are available that meet the FSA cost and performance goals.

Flat-plate solar array project. Volume 7: Module encapsulation

NASA Technical Reports Server (NTRS)

Cuddihy, E.; Coulbert, C.; Gupta, A.; Liang, R.

1986-01-01

The objective of the Encapsulation Task was to develop, demonstrate, and qualify photovoltaic (PV) module encapsulation systems that would provide 20 year (later decreased to 30 year) life expectancies in terrestrial environments, and which would be compatible with the cost and performance goals of the Flat-Plate Solar Array (FSA) Project. The scope of the Encapsulation Task included the identification, development, and evaluation of material systems and configurations required to support and protect the optically and electrically active solar cell circuit components in the PV module operating environment. Encapsulation material technologies summarized include the development of low cost ultraviolet protection techniques, stable low cost pottants, soiling resistant coatings, electrical isolation criteria, processes for optimum interface bonding, and analytical and experimental tools for evaluating the long term durability and structural adequacy of encapsulated modules. Field testing, accelerated stress testing, and design studies have demonstrated that encapsulation materials, processes, and configurations are available that meet the FSA cost and performance goals.

Potential-Induced Degradation-Delamination Mode in Crystalline Silicon Modules: Preprint

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

Hacke, Peter L; Kempe, Michael D; Wohlgemuth, John

A test sequence producing potential-induced degradation-delamination (PID-d) in crystalline silicon modules has been tested and found comparable under visual inspection to cell/encapsulant delamination seen in some fielded modules. Four commercial modules were put through this sequence, 85 degrees C, 85%, 1000 h damp heat, followed by an intensive PID stress sequence of 72 degrees C, 95% RH, and -1000 V, with the module face grounded using a metal foil. The 60 cell c-Si modules exhibiting the highest current transfer (4.4 center dot 10-4 A) exhibited PID-d at the first inspection after 156 h of PID stress. Effects promoting PID-d aremore » reduced adhesion caused by damp heat, sodium migration further reducing adhesion to the cells, and gaseous products of electrochemical reactions driven by the applied system voltage. A new work item proposal for an IEC test standard to evaluate for PID-d is anticipated.« less

3D calcite heterostructures for dynamic and deformable mineralized matrices

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

Yi, Jaeseok; Wang, Yucai; Jiang, Yuanwen

Scales are rooted in soft tissues, and are regenerated by specialized cells. The realization of dynamic synthetic analogues with inorganic materials has been a significant challenge, because the abiological regeneration sites that could yield deterministic growth behavior are hard to form. Here we overcome this fundamental hurdle by constructing a mutable and deformable array of three-dimensional calcite heterostructures that are partially locked in silicone. Individual calcite crystals exhibit asymmetrical dumbbell shapes and are prepared by a parallel tectonic approach under ambient conditions. Furthermore, the silicone matrix immobilizes the epitaxial nucleation sites through self-templated cavities, which enables symmetry breaking in reactionmore » dynamics and scalable manipulation of the mineral ensembles. With this platform, we devise several mineral-enabled dynamic surfaces and interfaces. For example, we show that the induced growth of minerals yields localized inorganic adhesion for biological tissue and reversible focal encapsulation for sensitive components in flexible electronics.« less

Synchrotron X-ray topography of electronic materials.

PubMed

Tuomi, T

2002-05-01

Large-area transmission, transmission section, large-area back-reflection, back-reflection section and grazing-incidence topography are the geometries used when recording high-resolution X-ray diffraction images with synchrotron radiation from a bending magnet, a wiggler or an undulator of an electron or a positron storage ring. Defect contrast can be kinematical, dynamical or orientational even in the topographs recorded on the same film at the same time. In this review article limited to static topography experiments, examples of defect studies on electronic materials cover the range from voids and precipitates in almost perfect float-zone and Czochralski silicon, dislocations in gallium arsenide grown by the liquid-encapsulated Czochralski technique, the vapour-pressure controlled Czochralski technique and the vertical-gradient freeze technique, stacking faults and micropipes in silicon carbide to misfit dislocations in epitaxic heterostructures. It is shown how synchrotron X-ray topographs of epitaxic laterally overgrown gallium arsenide layer structures are successfully explained by orientational contrast.

EPR investigations of silicon carbide nanoparticles functionalized by acid doped polyaniline

NASA Astrophysics Data System (ADS)

Karray, Fekri; Kassiba, Abdelhadi

2012-06-01

Nanocomposites (SiC-PANI) based on silicon carbide nanoparticles (SiC) encapsulated in conducting polyaniline (PANI) are synthesized by direct polymerization of PANI on the nanoparticle surfaces. The conductivity of PANI and the nanocomposites was modulated by several doping levels of camphor sulfonic acid (CSA). Electron paramagnetic resonance (EPR) investigations were carried out on representative SiC-PANI samples over the temperature range [100-300 K]. The features of the EPR spectra were analyzed taking into account the paramagnetic species such as polarons with spin S=1/2 involved in two main environments realized in the composites as well as their thermal activation. A critical temperature range 200-225 K was revealed through crossover changes in the thermal behavior of the EPR spectral parameters. Insights on the electronic transport properties and their thermal evolutions were inferred from polarons species probed by EPR and the electrical conductivity in doped nanocomposites.

3D calcite heterostructures for dynamic and deformable mineralized matrices

DOE PAGES

Yi, Jaeseok; Wang, Yucai; Jiang, Yuanwen; ...

2017-09-11

Scales are rooted in soft tissues, and are regenerated by specialized cells. The realization of dynamic synthetic analogues with inorganic materials has been a significant challenge, because the abiological regeneration sites that could yield deterministic growth behavior are hard to form. Here we overcome this fundamental hurdle by constructing a mutable and deformable array of three-dimensional calcite heterostructures that are partially locked in silicone. Individual calcite crystals exhibit asymmetrical dumbbell shapes and are prepared by a parallel tectonic approach under ambient conditions. Furthermore, the silicone matrix immobilizes the epitaxial nucleation sites through self-templated cavities, which enables symmetry breaking in reactionmore » dynamics and scalable manipulation of the mineral ensembles. With this platform, we devise several mineral-enabled dynamic surfaces and interfaces. For example, we show that the induced growth of minerals yields localized inorganic adhesion for biological tissue and reversible focal encapsulation for sensitive components in flexible electronics.« less

Two-way communication for programming and measurement in a miniature implantable stimulator.

PubMed

Thil, M A; Gérard, B; Jarvis, J C; Delbeke, J

2005-07-01

Implantable stimulators are needed for chronic electrical stimulation of nerves and muscles in experimental studies. The device described exploits the versatility of current microcontrollers for stimulation and communication in a miniature implant. Their standard outputs can provide the required selectable constant-current sources. In this device, pre-programmed stimulation paradigms were selected by transcutaneous light pulses. The potential of a programmable integrated circuit (PIC) was thus exploited. Implantable devices must be biocompatible. A novel encapsulation method that require no specialised equipment and that used two classical encapsulants, silicone and Teflon was developed. It was tested for implantation periods of up to four weeks. A novel way to estimate electrode impedance in awake animals is also presented. It was thus possible to follow the evolution of the nerve-electrode interface and, if necessary, to adjust the stimulation parameters. In practice, the electrode voltage at the end of a known constant-current pulse was measured by the PIC. The binary coded value was then indicated to the user as a series of muscle twitches that represented the binary value of the impedance measurement. This neurostimulator has been successfully tested in vitro and in vivo. Thresholds and impedance values were chronically monitored following implantation of a self-sizing spiral cuff electrode. Impedance variations in the first weeks could reflect morphological changes usually observed after the implantation of such electrodes.

Degradation of phosphor-in-glass encapsulants with various phosphor types for high power LEDs

NASA Astrophysics Data System (ADS)

Iqbal, Fauzia; Kim, Sunil; Kim, Hyungsun

2017-10-01

In order to replace conventional silicone-based phosphor light emitting diodes (LEDs), inorganic color converters with high thermal stabilities and transparencies, i.e., phosphors-in-glass (PiGs), have been investigated as encapsulants for high-power LEDs. In this paper, the effect of various types of phosphors, i.e., LuAG (green, Lu3Al5O12:Ce3+), silicate (yellow, Sr2SiO4:Eu2+), CASN (red, CaAlSiN3:Eu2+), and oxynitride (yellow, (Sr,Ba) Si2O2N2:Eu2+), on the reliability/degradation of the remote PiG encapsulants is explored for high power LEDs. For this purpose, a glass composition (SiO2-B2O3-ZnO-Na2O) was separately mixed with each type of phosphor and then sintered at appropriate temperatures to make the corresponding PiG. The reliabilities of the formed PiGs were evaluated by standard accelerated-aging tests (85 °C/85% RH) for 1000 h. Luminosity losses and shifts in the Commission Internationale de l'Eclairage (CIE) coordinates of the PiGs were measured before and after aging. Thermal, and moisture-induced quenching behavior was also analyzed. The surface of PiGs with different phosphors degraded differently, possibly because of structural incompatibilities between the glass matrix and phosphor type. Determining the compatibility of the glass composition with the type of phosphor used is therefore important in order to ensure the long-term stabilities of encapsulants for use in commercial LEDs.

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

Pern, F.J.; Glick, S.H.

We have conducted a series of accelerated exposure test (AET) studies for various crystalline-Si (c-Si) and amorphous-Si (a-Si) cell samples that were encapsulated with different superstrates, pottants, and substrates. Nonuniform browning patterns of ethylene vinyl acetate (EVA) pottants were observed for glass/EVA/glass-encapsulated c-Si cell samples under solar simulator exposures at elevated temperatures. The polymer/polymer-configured laminates with Tedlar or Tefzel did not discolor because of photobleaching reactions, but yellowed with polyester or nylon top films. Delamination was observed for the polyester/EVE layers on a-Si minimodules and for a polyolefin-based thermoplastic pottant at high temperatures. For all tested c-Si cell samples, irregularmore » changes in the current-voltage parameters were observed that could not be accounted for simply by the transmittance changes of the superstrate/pottant layers. Silicone-type adhesives used under UV-transmitting polymer top films were observed to cause greater cell current/efficiency loss than EVA or polyethylene pottants. {copyright} {ital 1999 American Institute of Physics.}« less

Effectiveness of X-ray grating interferometry for non-destructive inspection of packaged devices

NASA Astrophysics Data System (ADS)

Uehara, Masato; Yashiro, Wataru; Momose, Atsushi

2013-10-01

It is difficult to inspect packaged devices such as IC packages and power modules because the devices contain various components, such as semiconductors, metals, ceramics, and resin. In this paper, we demonstrated the effectiveness of X-ray grating interferometry (XGI) using a laboratory X-ray tube for the industrial inspection of packaged devices. The obtained conventional absorption image showed heavy-elemental components such as metal wires and electrodes, but the image did not reveal the defects in the light-elemental components. On the other hand, the differential phase-contrast image obtained by XGI revealed microvoids and scars in the encapsulant of the samples. The visibility contrast image also obtained by XGI showed some cracks in the ceramic insulator of power module sample. In addition, the image showed the silicon plate surrounded by the encapsulant having the same X-ray absorption coefficient. While these defects and components are invisible in the conventional industrial X-ray imaging, XGI thus has an attractive potential for the industrial inspection of the packaged devices.

Studies of encapsulant materials for terrestrial solar-cell arrays

NASA Technical Reports Server (NTRS)

Carmichael, D. C. (Compiler)

1975-01-01

Study 1 of this contract is entitled ""Evaluation of World Experience and Properties of Materials for Encapsulation of Terrestrial Solar-Cell Arrays.'' The approach of this study is to review and analyze world experience and to compile data on properties of encapsulants for photovoltaic cells and for related applications. The objective of the effort is to recommend candidate materials and processes for encapsulating terrestrial photovoltaic arrays at low cost for a service life greater than 20 years. The objectives of Study 2, ""Definition of Encapsulant Service Environments and Test Conditions,'' are to develop the climatic/environmental data required to define the frequency and duration of detrimental environmental conditions in a 20-year array lifetime and to develop a corresponding test schedule for encapsulant systems.

A microcomputer-based data acquisition system for ECG, body and ambient temperatures measurement during bathing.

PubMed

Uokawa, Y; Yonezawa, Y; Caldwell, W M; Hahn, A W

2000-01-01

A data acquisition system employing a low power 8 bit microcomputer has been developed for heart rate variability monitoring before, during and after bathing. The system consists of three integral chest electrodes, two temperature sensors, an instrumentation amplifier, a low power 8-bit single chip microcomputer (SMC) and a 4 MB compact flash memory (CFM). The ECG from the electrodes is converted to an 8-bit digital format at a 1 ms rate by an A/D converter in the SMC. Both signals from the body and ambient temperature sensors are converted to an 8-bit digital format every 1 second. These data are stored by the CFM. The system is powered by a rechargeable 3.6 V lithium battery. The 4 x 11 x 1 cm system is encapsulated in epoxy and silicone, yielding a total volume of 44 cc. The weight is 100 g.

Multifunctional hydrogel nano-probes for atomic force microscopy

PubMed Central

Lee, Jae Seol; Song, Jungki; Kim, Seong Oh; Kim, Seokbeom; Lee, Wooju; Jackman, Joshua A.; Kim, Dongchoul; Cho, Nam-Joon; Lee, Jungchul

2016-01-01

Since the invention of the atomic force microscope (AFM) three decades ago, there have been numerous advances in its measurement capabilities. Curiously, throughout these developments, the fundamental nature of the force-sensing probe—the key actuating element—has remained largely unchanged. It is produced by long-established microfabrication etching strategies and typically composed of silicon-based materials. Here, we report a new class of photopolymerizable hydrogel nano-probes that are produced by bottom-up fabrication with compressible replica moulding. The hydrogel probes demonstrate excellent capabilities for AFM imaging and force measurement applications while enabling programmable, multifunctional capabilities based on compositionally adjustable mechanical properties and facile encapsulation of various nanomaterials. Taken together, the simple, fast and affordable manufacturing route and multifunctional capabilities of hydrogel AFM nano-probes highlight the potential of soft matter mechanical transducers in nanotechnology applications. The fabrication scheme can also be readily utilized to prepare hydrogel cantilevers, including in parallel arrays, for nanomechanical sensor devices. PMID:27199165

Cutaneous and inflammatory response to long-term percutaneous implants of sphere-templated porous/solid poly(HEMA) and silicone in Mice

PubMed Central

Fleckman, Philip; Usui, Marcia; Zhao, Ge; Underwood, Robert; Maginness, Max; Marshall, Andrew; Glaister, Christine; Ratner, Buddy; Olerud, John

2012-01-01

This study investigates mouse cutaneous responses to long-term percutaneously implanted rods surrounded by sphere-templated porous biomaterials engineered to mimic medical devices surrounded by a porous cuff. We hypothesized that keratinocytes would migrate through the pores and stop, permigrate, or marsupialize along the porous/solid interface. Porous/solid-core poly(2-hydroxyethyl methacrylate) [poly(HEMA)] and silicone rods were implanted in mice for 14 days, 1 month, 3 months, and 6 months. Implants with surrounding tissue were analyzed (immuno)histochemically by light microscopy. Poly(HEMA)/skin implants yielded better morphologic data than silicone implants. Keratinocytes at the poly(HEMA) interface migrated in two different directions. “Ventral” keratinocytes contiguous with the dermal-epidermal junction migrated into the outermost pores, forming an integrated collar surrounding the rods. ”Dorsal” keratinocytes appearing to emanate from the differentiated epithelial layer, extended upward along and into the exterior portion of the rod, forming an integrated sheath. Leukocytes persisted in poly(HEMA) and silicone pores for the duration of the study. Vascular and collagen networks within the poly(HEMA) pores matured as a function of time up to 3 months implantation. Nerves were not observed within the pores. Poly(HEMA) underwent morphological changes by 6 months of implantation. Marsupialization, foreign body encapsulation and infection were not observed in any implants. PMID:22359383

A Highly Stretchable and Robust Non-fluorinated Superhydrophobic Surface.

PubMed

Ju, Jie; Yao, Xi; Hou, Xu; Liu, Qihan; Zhang, Yu Shrike; Khademhosseini, Ali

2017-08-21

Superhydrophobic surface simultaneously possessing exceptional stretchability, robustness, and non-fluorination is highly desirable in applications ranging from wearable devices to artificial skins. While conventional superhydrophobic surfaces typically feature stretchability, robustness, or non-fluorination individually, co-existence of all these features still remains a great challenge. Here we report a multi-performance superhydrophobic surface achieved through incorporating hydrophilic micro-sized particles with pre-stretched silicone elastomer. The commercial silicone elastomer (Ecoflex) endowed the resulting surface with high stretchability; the densely packed micro-sized particles in multi-layers contributed to the preservation of the large surface roughness even under large strains; and the physical encapsulation of the microparticles by silicone elastomer due to the capillary dragging effect and the chemical interaction between the hydrophilic silica and the elastomer gave rise to the robust and non-fluorinated superhydrophobicity. It was demonstrated that the as-prepared fluorine-free surface could preserve the superhydrophobicity under repeated stretching-relaxing cycles. Most importantly, the surface's superhydrophobicity can be well maintained after severe rubbing process, indicating wear-resistance. Our novel superhydrophobic surface integrating multiple key properties, i.e. stretchability, robustness, and non-fluorination, is expected to provide unique advantages for a wide range of applications in biomedicine, energy, and electronics.

Performance of MEMS Silicon Oscillator, ASFLM1, under Wide Operating Temperature Range

NASA Technical Reports Server (NTRS)

Patterson, Richard L.; Hammoud, Ahmad

2008-01-01

Over the last few years, MEMS (Micro-Electro-Mechanical Systems) resonator-based oscillators began to be offered as commercial-off-the-shelf (COTS) parts by a few companies [1-2]. These quartz-free, miniature silicon devices could compete with the traditional crystal oscillators in providing the timing (clock function) for many digital and analog electronic circuits. They provide stable output frequency, offer great tolerance to shock and vibration, and are immune to electro-static discharge [1-2]. In addition, they are encapsulated in compact lead-free packages, cover a wide frequency range (1 MHz to 125 MHz), and are specified, depending on the grade, for extended temperature operation from -40 C to +85 C. The small size of the MEMS oscillators along with their reliability and thermal stability make them candidates for use in space exploration missions. Limited data, however, exist on the performance and reliability of these devices under operation in applications where extreme temperatures or thermal cycling swings, which are typical of space missions, are encountered. This report presents the results of the work obtained on the evaluation of an ABRACON Corporation MEMS silicon oscillator chip, type ASFLM1, under extreme temperatures.

Design, manufacturing and measurement of a PV miniconcentrator for front point-contact silicon solar cells

NASA Astrophysics Data System (ADS)

Pérez, D.; Miñano, J. C.; Benítez, P.; Muñoz, F.; Mohedano, R.

2005-08-01

A novel photovoltaic concentrator has been developed in the framework of the European project "High efficiency silicon solar cells concentrator". In this project, front-contacted silicon solar cell have also been designed and manufactured by the project leader (the French LETI). This silicon cell concept is potentially capable to perform well (24% efficiency has been predicted) for much higher concentration levels than the back-contacted cells (and, of course, than the two-side contacted cells). The concentrator is formed by one lens of squared contour with flat entry surface and large-facet Fresnel exit surface, and a secondary that encapsulates the solar cell. On the contrary to the conventional Fresnel lens plus nonimaging secondary concentrators, the primary and secondary are designed simultaneously, leading to better concentration-acceptance angle product without compromise with the compactness. The grid lines in the front-contacted cells are aluminium prisms (which contact the p+ and n+ emitters, alternatively), acting as a linear cone concentrator that concentrates Cg =1.52× in the cross sectional dimension of the prisms. The secondary concentrator has a refractive rotational symmetric top surface that is crossed with two linear flow-line TIR mirror. Then, in the cross section normal to the aluminium prisms, the secondary provides a 2D concentration of Cg =12×, while in the cross section parallel to the prisms it provides a 2D concentration of Cg =24.16× as the grid lines in this dimension. Therefore, the cell is rectangular (1:2.08 aspect ratio), being the grid lines parallel to the shorter rectangle side. The total 3D geometrical concentration is 24.16×(12×1.52) = 455× for the square aperture and rectangular cell, and gets a design acceptance angle α=+/-1.8 degrees. Injection moulded prototypes are have been manufactured and measured, proving an optical efficiency of 79%. Computer modelling of the concentrator performance will also be presented.

Module encapsulation technology

NASA Technical Reports Server (NTRS)

Willis, P.

1986-01-01

The identification and development techniques for low-cost module encapsulation materials were reviewed. Test results were displayed for a variety of materials. The improved prospects for modeling encapsulation systems for life prediction were reported.

Design, analysis and test verification of advanced encapsulation systems

NASA Technical Reports Server (NTRS)

Garcia, A., III; Kallis, J. M.; Trucker, D. C.

1983-01-01

Analytical models were developed to perform optical, thermal, electrical and structural analyses on candidate encapsulation systems. From these analyses several candidate encapsulation systems were selected for qualification testing.

Epoxy and Silicone Optical Nanocomposites Filled with Grafted Nanoparticles

NASA Astrophysics Data System (ADS)

Tao, Peng

Polymer nanocomposites, as a technologically important class of materials, exhibit diverse functional properties, and are used for applications ranging from structural and biomedical to electronic and optical. The properties of polymer nanocomposites are determined, in part, by the chemical composition of the polymer matrix and the nanofillers. Their properties are also sensitive to the geometry and size of the nanofillers, and to spatial distribution of the fillers. Control of the nanoparticle size and dispersion within a given polymer provides opportunities to tailor and optimize the properties of nanocomposites for specific application. For optical applications such as encapsulation of light emitting diodes (LEDs), polymer nanocomposites filled with homogeneously dispersed nanoparticles would endow the polymer encapsulant with new functionality without sacrificing optical transparency. To this end, this thesis focuses on developing a simple and versatile approach towards the fabrication of epoxy and silicone transparent nanocomposites using matrix compatible chain-grafted nanoparticles as fillers, and studying the optical properties of the nanocomposites. The surface chemistry and grafted polymer chain design have been shown to play an important role in determining the dispersion state of the grafted nanoparticles and hence the final optical properties of the nanocomposites. To prepare transparent epoxy nanocomposites, poly (glycidyl methacrylate) (PGMA) chains were grafted onto the optical nanoparticle surfaces via a combined phosphate ligand exchange process and azide-alkyne "click" chemistry. The dispersion behavior of PGMA-grafted nanoparticles within the epoxy matrix was investigated by systematically varying the grafting density and grafted chain length. It was found that within the small molecular weight epoxy resins, the dispersion states are more sensitive to the grafting density than the molecular weight of grafted chains. With high grafting densities, the grafted PGMA brushes effectively screen the van der Waals attraction between the particles, and homogenous nanoparticle dispersions of grafted nanoparticles were obtained. Transparent high refractive index TiO2/epoxy thin film and bulk nancomposites were obtained by dispersing PGMA brushes-grafted TiO2 nanoparticles into a commercial epoxy matrix. The refractive index of the nanocomposites showed a linear dependence on the volume fraction of TiO2 nanoparticles and the optical transparency could be generally described by the Rayleigh scattering model. This powerful dispersing technique was further employed to make visibly transparent, UV/IR blocking ITO/epoxy nanocomposites which can be easily applied onto glass and plastic substrates as energy saving optical coating materials. To produce transparent silicone nanocomposites, we directly coupled phosphate-terminated PDMS chains onto the optical nanoparticle surface. It was observed that the mono-modal PDMS-grafted particles usually formed agglomerates within silicone matrices, whereas the bimodal PDMS-grafted particles were able to be individually dispersed even within high molecular weight matrices. Transparent high refractive index bulk TiO2/silicone nanocomposites were successfully prepared by filling with bimodal PDMS-grafted TiO2 nanoparticles. Furthermore, we used the PDMS-grafted TiO2/silicone nanocomposite as a model system to create a methodology to predict and control the dispersion behavior of grafted nanoparticles. The good agreement between experimental observation of dispersion of mono-modal and bimodal grafted particles and theoretical prediction would better guide future experiments and lead to predictability in polymer composite design. Finally, the bimodal grafted chain design was implemented in the preparation of transparent and luminescent CdSe/silicone nanocomposites with potential application as non-scattering light conversion materials for LEDs. The homogeneous dispersion of bimodal PDMS-grafted CdSe quantum dots not only minimizes the transparency loss due to scattering, but also benefits the uniformity and long-term stability of photoluminescence of the nanocomposites.

Ultrasensitive competitive method-based electrochemiluminescence immunosensor for diethylstilbestrol detection based on Ru(bpy)32+ as luminophor encapsulated in metal-organic frameworks UiO-67.

PubMed

Dong, Xue; Zhao, Guanhui; Liu, Li; Li, Xuan; Wei, Qin; Cao, Wei

2018-07-01

In this work, Ru(bpy) 3 2+ encapsulated in metal-organic frameworks (MOFs) UiO-67 (Ru(bpy) 3 2+ /UiO-67) as luminophor was easily prepared and firstly applied in constructing an electrochemiluminescence (ECL) immunosensor to efficiently estimate diethylstilbestrol (DES). The competitive method-based ECL immunosensor platform was fabricated by amino-silicon dioxide which possesses large surface area. The poriness of UiO-67 was splendid so that Ru(bpy) 3 2+ could be easily encapsulated. Ru(bpy) 3 2+ /UiO-67 with excellent ECL luminescence signal existed large specific surface area for easily labeled with antibodies. DES competed with bovine serum albumin-diethylstilbestrol (BSA-DES) for binding to antibody-specific sites in the constructed immunosensor. However DES was micromolecule, which was easier to bond to antibodies than BSA-DES. The ECL signal was gradually decreases with the increase of the concentration of DES. Under optimal conditions, the proposed immunosensor exhibited a wide linear range from 0.01 pg mL -1 to 50 ng mL -1 with a low detetion limit of 3.27 fg mL -1 (S/N = 3). The novel fabricated immunosensor with interference immunity and high stability may cause an attractive approach for the other targets determination. Copyright © 2018 Elsevier B.V. All rights reserved.

Recent progress on the scalable fabrication of hybrid polymer/SiO2 nanophotonic cavity arrays with an encapsulated MoS2 film

NASA Astrophysics Data System (ADS)

Hammer, Sebastian; Mangold, Hans-Moritz; Nguyen, Ariana E.; Martinez-Ta, Dominic; Naghibi Alvillar, Sahar; Bartels, Ludwig; Krenner, Hubert J.

2018-02-01

We review1 the fully-scalable fabrication of a large array of hybrid molybdenum disulfide (MoS2) - silicon dioxide (SiO2) one-dimensional (1D), freestanding photonic-crystal cavities (PCCs) capable of enhancement of the MoS2 photoluminescence (PL) at the narrow cavity resonance. As demonstrated in our prior work [S. Hammer et al., Sci. Rep. 7, 7251 (2017)]1, geometric mode tuning over the wide spectral range of MoS2 PL can be achieved by changing the PC period. In this contribution, we provide a step-by-step description of the fabrication process and give additional detailed information on the degradation of MoS2 by XeF2 vapor. We avoid potential damage of the MoS2 monolayer during the crucial XeF2 etch by refraining from stripping the electron beam (e-beam) resist after dry etching of the photonic crystal pattern. The remaining resist on top of the samples encapsulates and protects the MoS2 film during the entire fabrication process. Albeit the thickness of the remaining resists strongly depends on the fabrication process, the resulting encapsulation of the MoS2 layer improves the confinement to the optical modes and gives rise to a potential enhancement of the light-matter interaction.

Amorphous silicon carbide ultramicroelectrode arrays for neural stimulation and recording

NASA Astrophysics Data System (ADS)

Deku, Felix; Cohen, Yarden; Joshi-Imre, Alexandra; Kanneganti, Aswini; Gardner, Timothy J.; Cogan, Stuart F.

2018-02-01

Objective. Foreign body response to indwelling cortical microelectrodes limits the reliability of neural stimulation and recording, particularly for extended chronic applications in behaving animals. The extent to which this response compromises the chronic stability of neural devices depends on many factors including the materials used in the electrode construction, the size, and geometry of the indwelling structure. Here, we report on the development of microelectrode arrays (MEAs) based on amorphous silicon carbide (a-SiC). Approach. This technology utilizes a-SiC for its chronic stability and employs semiconductor manufacturing processes to create MEAs with small shank dimensions. The a-SiC films were deposited by plasma enhanced chemical vapor deposition and patterned by thin-film photolithographic techniques. To improve stimulation and recording capabilities with small contact areas, we investigated low impedance coatings on the electrode sites. The assembled devices were characterized in phosphate buffered saline for their electrochemical properties. Main results. MEAs utilizing a-SiC as both the primary structural element and encapsulation were fabricated successfully. These a-SiC MEAs had 16 penetrating shanks. Each shank has a cross-sectional area less than 60 µm2 and electrode sites with a geometric surface area varying from 20 to 200 µm2. Electrode coatings of TiN and SIROF reduced 1 kHz electrode impedance to less than 100 kΩ from ~2.8 MΩ for 100 µm2 Au electrode sites and increased the charge injection capacities to values greater than 3 mC cm‑2. Finally, we demonstrated functionality by recording neural activity from basal ganglia nucleus of Zebra Finches and motor cortex of rat. Significance. The a-SiC MEAs provide a significant advancement in the development of microelectrodes that over the years has relied on silicon platforms for device manufacture. These flexible a-SiC MEAs have the potential for decreased tissue damage and reduced foreign body response. The technique is promising and has potential for clinical translation and large scale manufacturing.

Graphene-bonded and -encapsulated si nanoparticles for lithium ion battery anodes.

PubMed

Wen, Yang; Zhu, Yujie; Langrock, Alex; Manivannan, Ayyakkannu; Ehrman, Sheryl H; Wang, Chunsheng

2013-08-26

Silicon (Si) has been considered a very promising anode material for lithium ion batteries due to its high theoretical capacity. However, high-capacity Si nanoparticles usually suffer from low electronic conductivity, large volume change, and severe aggregation problems during lithiation and delithiation. In this paper, a unique nanostructured anode with Si nanoparticles bonded and wrapped by graphene is synthesized by a one-step aerosol spraying of surface-modified Si nanoparticles and graphene oxide suspension. The functional groups on the surface of Si nanoparticles (50-100 nm) not only react with graphene oxide and bind Si nanoparticles to the graphene oxide shell, but also prevent Si nanoparticles from aggregation, thus contributing to a uniform Si suspension. A homogeneous graphene-encapsulated Si nanoparticle morphology forms during the aerosol spraying process. The open-ended graphene shell with defects allows fast electrochemical lithiation/delithiation, and the void space inside the graphene shell accompanied by its strong mechanical strength can effectively accommodate the volume expansion of Si upon lithiation. The graphene shell provides good electronic conductivity for Si nanoparticles and prevents them from aggregating during charge/discharge cycles. The functionalized Si encapsulated by graphene sample exhibits a capacity of 2250 mAh g⁻¹ (based on the total mass of graphene and Si) at 0.1C and 1000 mAh g⁻¹ at 10C, and retains 85% of its initial capacity even after 120 charge/discharge cycles. The exceptional performance of graphene-encapsulated Si anodes combined with the scalable and one-step aerosol synthesis technique makes this material very promising for lithium ion batteries. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Advanced Materials and Devices for Bioresorbable Electronics.

PubMed

Kang, Seung-Kyun; Koo, Jahyun; Lee, Yoon Kyeung; Rogers, John A

2018-05-15

Recent advances in materials chemistry establish the foundations for unusual classes of electronic systems, characterized by their ability to fully or partially dissolve, disintegrate, or otherwise physically or chemically decompose in a controlled fashion after some defined period of stable operation. Such types of "transient" technologies may enable consumer gadgets that minimize waste streams associated with disposal, implantable sensors that disappear harmlessly in the body, and hardware-secure platforms that prevent unwanted recovery of sensitive data. This second area of opportunity, sometimes referred to as bioresorbable electronics, is of particular interest due to its ability to provide diagnostic or therapeutic function in a manner that can enhance or monitor transient biological processes, such as wound healing, while bypassing risks associated with extended device load on the body or with secondary surgical procedures for removal. Early chemistry research established sets of bioresorbable materials for substrates, encapsulation layers, and dielectrics, along with several options in organic and bio-organic semiconductors. The subsequent realization that nanoscale forms of device-grade monocrystalline silicon, such as silicon nanomembranes (m-Si NMs, or Si NMs) undergo hydrolysis in biofluids to yield biocompatible byproducts over biologically relevant time scales advanced the field by providing immediate routes to high performance operation and versatile, sophisticated levels of function. When combined with bioresorbable conductors, dielectrics, substrates, and encapsulation layers, Si NMs provide the basis for a broad, general class of bioresorbable electronics. Other properties of Si, such as its piezoresistivity and photovoltaic properties, allow other types of bioresorbable devices such as solar cells, strain gauges, pH sensors, and photodetectors. The most advanced bioresorbable devices now exist as complete systems with successful demonstrations of clinically relevant modes of operation in animal models. This Account highlights the foundational materials concepts for this area of technology, starting with the dissolution chemistry and reaction kinetics associated with hydrolysis of Si NMs as a function of temperature, pH, and ion and protein concentration. A following discussion focuses on key supporting materials, including a range of dielectrics, metals, and substrates. As comparatively low performance alternatives to Si NMs, bioresorbable organic semiconductors are also presented, where interest derives from their intrinsic flexibility, low-temperature processability, and ease of chemical modification. Representative examples of encapsulation materials and strategies in passive and active control of device lifetime are then discussed, with various device illustrations. A final section outlines bioresorbable electronics for sensing of various biophysical parameters, monitoring electrophysiological activity, and delivering drugs in a programmed manner. Fundamental research in chemistry remains essential to the development of this emerging field, where continued advances will increase the range of possibilities in sensing, actuation, and power harvesting. Materials for encapsulation layers that can delay water-diffusion and dissolution of active electronics in passively or actively triggered modes are particularly important in addressing areas of opportunity in clinical medicine, and in secure systems for envisioned military and industrial uses. The deep scientific content and the broad range of application opportunities suggest that research in transient electronic materials will remain a growing area of interest to the chemistry community.

Fabricating porous silicon carbide

NASA Technical Reports Server (NTRS)

Shor, Joseph S. (Inventor); Kurtz, Anthony D. (Inventor)

1994-01-01

The formation of porous SiC occurs under electrochemical anodization. A sample of SiC is contacted electrically with nickel and placed into an electrochemical cell which cell includes a counter electrode and a reference electrode. The sample is encapsulated so that only a bare semiconductor surface is exposed. The electrochemical cell is filled with an HF electrolyte which dissolves the SiC electrochemically. A potential is applied to the semiconductor and UV light illuminates the surface of the semiconductor. By controlling the light intensity, the potential and the doping level, a porous layer is formed in the semiconductor and thus one produces porous SiC.

A facile single-step synthesis of ternary multicore magneto-plasmonic nanoparticles.

PubMed

Benelmekki, Maria; Bohra, Murtaza; Kim, Jeong-Hwan; Diaz, Rosa E; Vernieres, Jerome; Grammatikopoulos, Panagiotis; Sowwan, Mukhles

2014-04-07

We report a facile single-step synthesis of ternary hybrid nanoparticles (NPs) composed of multiple dumbbell-like iron-silver (FeAg) cores encapsulated by a silicon (Si) shell using a versatile co-sputter gas-condensation technique. In comparison to previously reported binary magneto-plasmonic NPs, the advantage conferred by a Si shell is to bind the multiple magneto-plasmonic (FeAg) cores together and prevent them from aggregation at the same time. Further, we demonstrate that the size of the NPs and number of cores in each NP can be modulated over a wide range by tuning the experimental parameters.

Creating homogenous strain distribution within 3D cell-encapsulated constructs using a simple and cost-effective uniaxial tensile bioreactor: Design and validation study.

PubMed

Subramanian, Gayathri; Elsaadany, Mostafa; Bialorucki, Callan; Yildirim-Ayan, Eda

2017-08-01

Mechanical loading bioreactors capable of applying uniaxial tensile strains are emerging to be a valuable tool to investigate physiologically relevant cellular signaling pathways and biochemical expression. In this study, we have introduced a simple and cost-effective uniaxial tensile strain bioreactor for the application of precise and homogenous uniaxial strains to 3D cell-encapsulated collagen constructs at physiological loading strains (0-12%) and frequencies (0.01-1 Hz). The bioreactor employs silicone-based loading chambers specifically designed to stretch constructs without direct gripping to minimize stress concentration at the ends of the construct and preserve its integrity. The loading chambers are driven by a versatile stepper motor ball-screw actuation system to produce stretching of the constructs. Mechanical characterization of the bioreactor performed through Finite Element Analysis demonstrated that the constructs experienced predominantly uniaxial tensile strain in the longitudinal direction. The strains produced were found to be homogenous over a 15 × 4 × 2 mm region of the construct equivalent to around 60% of the effective region of characterization. The strain values were also shown to be consistent and reproducible during cyclic loading regimes. Biological characterization confirmed the ability of the bioreactor to promote cell viability, proliferation, and matrix organization of cell-encapsulated collagen constructs. This easy-to-use uniaxial tensile strain bioreactor can be employed for studying morphological, structural, and functional responses of cell-embedded matrix systems in response to physiological loading of musculoskeletal tissues. It also holds promise for tissue-engineered strategies that involve delivery of mechanically stimulated cells at the site of injury through a biological carrier to develop a clinically useful therapy for tissue healing. Biotechnol. Bioeng. 2017;114: 1878-1887. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Analysis of an anti-reflecting nanowire transparent electrode for solar cells

NASA Astrophysics Data System (ADS)

Zhao, Zhexin; Wang, Ken Xingze; Fan, Shanhui

2017-03-01

Transparent electrodes are an important component in many optoelectronic devices, especially solar cells. In this paper, we investigate a nanowire transparent electrode that also functions as an anti-reflection coating for silicon solar cells, taking into account the practical constraints that the electrode is typically encapsulated and needs to be in electric contact with the semiconductor. Numerical simulations show that the electrode can provide near-perfect broadband anti-reflection over much of the frequency range above the silicon band gap for both polarizations while keeping the sheet resistance sufficiently low. To provide insights into the physics mechanism of this broadband anti-reflection, we introduce a generalized Fabry-Perot model, which captures the effects of the higher order diffraction channels as well as the modification of the reflection coefficient of the interface introduced by the nanowires. This model is validated using frequency-domain electromagnetic simulations. Our work here provides design guidelines for nanowire transparent electrode in a device configuration that is relevant for solar cell applications.

Micro Solar Cells with Concentration and Light Trapping Optics

NASA Astrophysics Data System (ADS)

Li, Lanfang; Breuckner, Eric; Corcoran, Christopher; Yao, Yuan; Xu, Lu; Nuzzo, Ralph

2013-03-01

Compared with conventional bulk plate semiconductor solar cells, micro solar cells provide opportunity for novel design geometry and provide test bed for light trapping at the device level as well as module level. Surface recombination, however, will have to be addressed properly as the much increased surface area due to the reduced dimension is more prominent in these devices than conventional solar cells. In this poster, we present experimental demonstration of silicon micro solar cells with concentration and light trapping optics. Silicon micro solar cell with optimized surface passivation and doping profile that exhibit high efficiency is demonstrated. Effective incorporation of high quantum yield fluorescent centers in the polymer matrix into which micro solar cell was encapsulated was investigated for luminescent solar concentration application. Micro-cell on a semi-transparent, nanopatterned reflector formed by soft-imprint lithography was investigated for near field effect related solar conversion performance enhancement. This work is supported by the DOE `Light-Material Interactions in Energy Conversion' Energy Frontier Research Center under grant DE-SC0001293

High-Responsivity Graphene-Boron Nitride Photodetector and Autocorrelator in a Silicon Photonic Integrated Circuit.

PubMed

Shiue, Ren-Jye; Gao, Yuanda; Wang, Yifei; Peng, Cheng; Robertson, Alexander D; Efetov, Dmitri K; Assefa, Solomon; Koppens, Frank H L; Hone, James; Englund, Dirk

2015-11-11

Graphene and other two-dimensional (2D) materials have emerged as promising materials for broadband and ultrafast photodetection and optical modulation. These optoelectronic capabilities can augment complementary metal-oxide-semiconductor (CMOS) devices for high-speed and low-power optical interconnects. Here, we demonstrate an on-chip ultrafast photodetector based on a two-dimensional heterostructure consisting of high-quality graphene encapsulated in hexagonal boron nitride. Coupled to the optical mode of a silicon waveguide, this 2D heterostructure-based photodetector exhibits a maximum responsivity of 0.36 A/W and high-speed operation with a 3 dB cutoff at 42 GHz. From photocurrent measurements as a function of the top-gate and source-drain voltages, we conclude that the photoresponse is consistent with hot electron mediated effects. At moderate peak powers above 50 mW, we observe a saturating photocurrent consistent with the mechanisms of electron-phonon supercollision cooling. This nonlinear photoresponse enables optical on-chip autocorrelation measurements with picosecond-scale timing resolution and exceptionally low peak powers.

Photolithography and Fluorescence Correlation Spectroscopy used to examine the rates of exchange in reverse micelle systems

NASA Astrophysics Data System (ADS)

Norris, Zach; Mawson, Cara; Johnson, Kyron; Kessler, Sarah; Rebecca, Anne; Wolf, Nathan; Lim, Michael; Nucci, Nathaniel

Reverse micelles are molecular complexes that encapsulate a nanoscale pool of water in a surfactant shell dissolved in non-polar solvent. These complexes have a wide range of applications, and in all cases, the degree to which reverse micelles (RM) exchange their contents is relevant for their use. Despite its importance, this aspect of RM behavior is poorly understood. Photolithography is employed here to create micro and nano scale fluidic systems in which mixing rates can be precisely measured using fluorescence correlation spectroscopy (FCS). Micro-channel patterns are etched using reactive ion etching process into a layer of silicon dioxide on crystalline silicon substrates. Solutions containing mixtures of reverse micelles, proteins, and fluorophores are placed into reservoirs in the patterns, while diffusion and exchange between RMs is monitored using a FCS system built from a modified confocal Raman spectrometer. Using this approach, the diffusion and exchange rates for RM systems are measured as a function of the components of the RM mixture. Funding provided by Rowan University.

Hardness assurance testing and radiation hardening by design techniques for silicon-germanium heterojunction bipolar transistors and digital logic circuits

NASA Astrophysics Data System (ADS)

Sutton, Akil K.

Hydrocarbon exploration, global navigation satellite systems, computed tomography, and aircraft avionics are just a few examples of applications that require system operation at an ambient temperature, pressure, or radiation level outside the range covered by military specifications. The electronics employed in these applications are known as "extreme environment electronics." On account of the increased cost resulting from both process modifications and the use of exotic substrate materials, only a handful of semiconductor foundries have specialized in the production of extreme environment electronics. Protection of these electronic systems in an extreme environment may be attained by encapsulating sensitive circuits in a controlled environment, which provides isolation from the hostile ambient, often at a significant cost and performance penalty. In a significant departure from this traditional approach, system designers have begun to use commercial off-the-shelf technology platforms with built in mitigation techniques for extreme environment applications. Such an approach simultaneously leverages the state of the art in technology performance with significant savings in project cost. Silicon-germanium is one such commercial technology platform that demonstrates potential for deployment into extreme environment applications as a result of its excellent performance at cryogenic temperatures, remarkable tolerance to radiation-induced degradation, and monolithic integration with silicon-based manufacturing. In this dissertation the radiation response of silicon-germanium technology is investigated, and novel transistor-level layout-based techniques are implemented to improve the radiation tolerance of HBT digital logic.

Excellent c-Si surface passivation by low-temperature atomic layer deposited titanium oxide

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

Liao, Baochen, E-mail: liaobaochen@nus.edu.sg; Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117576; A*STAR Institute of Materials Research and Engineering

2014-06-23

In this work, we demonstrate that thermal atomic layer deposited (ALD) titanium oxide (TiO{sub x}) films are able to provide a—up to now unprecedented—level of surface passivation on undiffused low-resistivity crystalline silicon (c-Si). The surface passivation provided by the ALD TiO{sub x} films is activated by a post-deposition anneal and subsequent light soaking treatment. Ultralow effective surface recombination velocities down to 2.8 cm/s and 8.3 cm/s, respectively, are achieved on n-type and p-type float-zone c-Si wafers. Detailed analysis confirms that the TiO{sub x} films are nearly stoichiometric, have no significant level of contaminants, and are of amorphous nature. The passivation is foundmore » to be stable after storage in the dark for eight months. These results demonstrate that TiO{sub x} films are also capable of providing excellent passivation of undiffused c-Si surfaces on a comparable level to thermal silicon oxide, silicon nitride, and aluminum oxide. In addition, it is well known that TiO{sub x} has an optimal refractive index of 2.4 in the visible range for glass encapsulated solar cells, as well as a low extinction coefficient. Thus, the results presented in this work could facilitate the re-emergence of TiO{sub x} in the field of high-efficiency silicon wafer solar cells.« less

The effect of adsorbates on the electrical stability of graphene studied by transient photocurrent spectroscopy

NASA Astrophysics Data System (ADS)

Kalkan, S. B.; Aydın, H.; Özkendir, D.; ćelebi, C.

2018-01-01

Adsorbate induced variations in the electrical conductivity of graphene layers with two different types of charge carriers are investigated by using the Transient Photocurrent Spectroscopy (TPS) measurement technique. In-vacuum TPS measurements taken for a duration of 5 ks revealed that the adsorption/desorption of atmospheric adsorbates leads to more than a 110% increment and a 45% decrement in the conductivity of epitaxial graphene (n-type) and chemical vapor deposition graphene (p-type) layers on semi-insulating silicon carbide (SiC) substrates, respectively. The graphene layers on SiC are encapsulated and passivated with a thin SiO2 film grown by the Pulsed Electron Deposition method. The measurements conducted for short periods and a few cycles showed that the encapsulation process completely suppresses the time dependent conductivity instability of graphene independent of its charge carrier type. The obtained results are used to construct an experimental model for identifying adsorbate related conductivity variations in graphene and also in other 2D materials with an inherently high surface-to-volume ratio.

Binary particle separation in droplet microfluidics using acoustophoresis

NASA Astrophysics Data System (ADS)

Fornell, Anna; Cushing, Kevin; Nilsson, Johan; Tenje, Maria

2018-02-01

We show a method for separation of two particle species with different acoustic contrasts originally encapsulated in the same droplet in a continuous two-phase system. This was realized by using bulk acoustic standing waves in a 380 μm wide silicon-glass microfluidic channel. Polystyrene particles (positive acoustic contrast particles) and in-house synthesized polydimethylsiloxane (PDMS) particles (negative acoustic contrast particles) were encapsulated inside water-in-oil droplets either individually or in a mixture. At acoustic actuation of the system at the fundamental resonance frequency, the polystyrene particles were moved to the center of the droplet (pressure node), while the PDMS particles were moved to the sides of the droplet (pressure anti-nodes). The acoustic particle manipulation step was combined in series with a trifurcation droplet splitter, and as the original droplet passed through the splitter and was divided into three daughter droplets, the polystyrene particles were directed into the center daughter droplet, while the PDMS particles were directed into the two side daughter droplets. The presented method expands the droplet microfluidics tool-box and offers new possibilities to perform binary particle separation in droplet microfluidic systems.

Method for integrating microelectromechanical devices with electronic circuitry

DOEpatents

Barron, Carole C.; Fleming, James G.; Montague, Stephen

1999-01-01

A method is disclosed for integrating one or more microelectromechanical (MEM) devices with electronic circuitry on a common substrate. The MEM device can be fabricated within a substrate cavity and encapsulated with a sacrificial material. This allows the MEM device to be annealed and the substrate planarized prior to forming electronic circuitry on the substrate using a series of standard processing steps. After fabrication of the electronic circuitry, the electronic circuitry can be protected by a two-ply protection layer of titanium nitride (TiN) and tungsten (W) during an etch release process whereby the MEM device is released for operation by etching away a portion of a sacrificial material (e.g. silicon dioxide or a silicate glass) that encapsulates the MEM device. The etch release process is preferably performed using a mixture of hydrofluoric acid (HF) and hydrochloric acid (HCI) which reduces the time for releasing the MEM device compared to use of a buffered oxide etchant. After release of the MEM device, the TiN:W protection layer can be removed with a peroxide-based etchant without damaging the electronic circuitry.

ASIC or PIC? Implantable stimulators based on semi-custom CMOS technology or low-power microcontroller architecture.

PubMed

Salmons, S; Gunning, G T; Taylor, I; Grainger, S R; Hitchings, D J; Blackhurst, J; Jarvis, J C

2001-01-01

To gain a better understanding of the effects of chronic stimulation on mammalian muscles we needed to generate patterns of greater variety and complexity than simple constant-frequency or burst patterns. We describe here two approaches to the design of implantable neuromuscular stimulators that can satisfy these requirements. Devices of both types were developed and used in long-term experiments. The first device was based on a semi-custom Application Specific Integrated Circuit (ASIC). This approach has the advantage that the circuit can be completely tested at every stage of development and production, assuring a high degree of reliability. It has the drawback of inflexibility: the patterns are produced by state machines implemented in silicon, so each new set of patterns requires a fresh production run, which is costly and time-consuming. The second device was based on a commercial microcontroller (Microchip PIC16C84). The functionality of this type of circuit is specified in software rather than in silicon hardware, allowing a single device to be programmed for different functions. With the use of features designed to improve fault-tolerance we found this approach to be as reliable as that based on ASICs. The encapsulated devices can easily be accommodated subcutaneously on the flank of a rabbit and a recent version is small enough to implant into the peritoneal cavity of rats. The current devices are programmed with a predetermined set of 12 patterns before assembly; the desired pattern is selected after implantation with an electronic flash gun. The operating current drain is less than 40 microA.

Encapsulating micro-nano Si/SiO x into conjugated nitrogen-doped carbon as binder-free monolithic anodes for advanced lithium ion batteries

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

Wang, Jing; Zhou, Meijuan; Tan, Guoqiang

2015-01-01

Silicon monoxide, a promising silicon-based anode candidate for lithium-ion batteries, has recently attracted much attention for its high theoretical capacity, good cycle stability, low cost, and environmental benignity. Currently, the most critical challenge is to improve its low initial coulombic efficiency and significant volume changes during the charge–discharge processes. Herein, we report a binder-free monolithic electrode structure based on directly encapsulating micro-nano Si/SiOx particles into conjugated nitrogen-doped carbon frameworks to form monolithic, multi-core, cross-linking composite matrices. We utilize micro-nano Si/SiOx reduced by high-energy ball-milling SiO as active materials, and conjugated nitrogen-doped carbon formed by the pyrolysis of polyacrylonitrile both asmore » binders and conductive agents. Owing to the high electrochemical activity of Si/SiOx and the good mechanical resiliency of conjugated nitrogen-doped carbon backbones, this specific composite structure enhances the utilization efficiency of SiO and accommodates its large volume expansion, as well as its good ionic and electronic conductivity. The annealed Si/SiOx/polyacrylonitrile composite electrode exhibits excellent electrochemical properties, including a high initial reversible capacity (2734 mA h g-1 with 75% coulombic efficiency), stable cycle performance (988 mA h g-1 after 100 cycles), and good rate capability (800 mA h g-1 at 1 A g-1 rate). Because the composite is naturally abundant and shows such excellent electrochemical performance, it is a promising anode candidate material for lithium-ion batteries. The binder-free monolithic architectural design also provides an effective way to prepare other monolithic electrode materials for advanced lithium-ion batteries.« less

Assessment of Operation of EMK21 MEMS Silicon Oscillator Over Wide Temperature Range

NASA Technical Reports Server (NTRS)

Patterson, Richard L.; Hammoud, Ahmad

2009-01-01

Electronic control systems, data-acquisition instrumentation, and microprocessors require accurate timing signals for proper operation. Traditionally, ceramic resonators and crystal oscillators provided this clock function for the majority of these systems. Over the last few years, MEMS (Micro-Electro-Mechanical Systems) resonator-based oscillators began to surface as commercial-off-the-shelf (COTS) parts by a few companies. These quartz-free, miniature silicon devices could easily replace the traditional crystal oscillators in providing the timing/clock function for many digital and analog circuits. They are reported to provide stable output frequency, offer great tolerance to shock and vibration, and are immune to electro-static discharge [ 1-2]. In addition, they are encapsulated in compact lead-free packages and cover a wide frequency range (1 MHz to 125 MHz). The small size of the MEMS oscillators along with their thermal stability make them ideal candidates for use in space exploration missions. Limited data, however, exist on the performance and reliability of these devices under operation in applications where extreme temperatures or thermal cycling swings, which are typical of space missions, are encountered. This report presents the results of the work obtained on the evaluation of an Ecliptek Corporation MEMS silicon oscillator chip under extreme temperatures.

Preserving viability of Lactobacillus rhamnosus GG in vitro and in vivo by a new encapsulation system

PubMed Central

Li, Ran; Zhang, Yufeng; Polk, D. Brent; Tomasula, Peggy M.; Yan, Fang; Liu, LinShu

2016-01-01

Probiotics have shown beneficial effects on health and prevention of diseases in humans. However, a concern for application of probiotics is the loss of viability during storage and gastrointestinal transit. The aim of this study was to develop an encapsulation system to preserve viability of probiotics when they are administrated orally and apply Lactobacillus rhamnosus GG (LGG) as a probiotic model to evaluate the effectiveness of this approach using in vitro and in vivo experiments. LGG was encapsulated in hydrogel beads prepared using pectin, a food grade polysaccharide, glucose, and calcium chloride, and lyophilized by freeze-drying. Encapsulated LGG was cultured in vitro under the condition that mimicked the physiological environment of the human gastrointestinal tract. Compared to non-encapsulated LGG, encapsulation increased tolerance of LGG in the acid condition, protected LGG from protease digestion, and improved shelf time when stored at the ambient condition, in regard of survivability and production of p40, a known LGG-derived protein involved in LGG’s beneficial effects on intestinal homeostasis. To evaluate the effects of encapsulation on p40 production in vivo and prevention of intestinal inflammation by LGG, mice were gavaged with LGG containing beads and treated with dextran sulphate sodium (DSS) to induce intestinal injury and colitis. Compared to non-encapsulated LGG, encapsulated LGG enhanced more p40 production in mice, and exerted higher levels of effects on prevention of DSS-induced colonic injury and colitis and suppression of pro-inflammatory cytokine production. These data indicated that the encapsulation system developed in this study preserves viability of LGG in vitro and in vivo, leading to longer shelf time and enhancing the functions of LGG in the gastrointestinal tract. Thus, this encapsulation approach may have the potential application for improving efficacy of probiotics. PMID:27063422

Adhesion and debonding kinetics of photovoltaic encapsulation in moist environments: Adhesion and debonding kinetics of photovoltaic encapsulation

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

Novoa, Fernando D.; Miller, David C.; Dauskardt, Reinhold H.

Debonding of photovoltaic (PV) encapsulation in moist environments is frequently reported but presently not well understood or quantified. Temperature cycling, moisture, and mechanical loads often cause loss of encapsulation adhesion and interfacial debonding, initially facilitating back-reflectance and reduced electrical current, but ultimately leading to internal corrosion and loss of module functionality. To investigate the effects of temperature (T) and relative humidity (RH) on the kinetics of encapsulation debonding, we developed a mechanics-based technique to measure encapsulation debond energy and debond growth rates in a chamber of controlled environment. The debond energy decreased from 2.15 to 1.75 kJ m-2 in poly(ethylene-co-vinylmore » acetate) (EVA) and from 0.67 to 0.52 kJ m-2 in polyvinyl butyral when T increased from 25 to 50 degrees C and 20 to 40 degrees C, respectively. The debond growth rates of EVA increased up to 1000-fold with small increases of T (10 degrees C) and RH (15%). To elucidate the mechanisms of environmental debonding, we developed a fracture-kinetics model, where the viscoelastic relaxation processes at the debonding-tip are used to predict debond growth. The model and techniques constitute the fundamental basis for developing accelerated aging tests and long-term reliability predictions for PV encapsulation.« less

Restoring visual perception using microsystem technologies: engineering and manufacturing perspectives.

PubMed

Krisch, I; Hosticka, B J

2007-01-01

Microsystem technologies offer significant advantages in the development of neural prostheses. In the last two decades, it has become feasible to develop intelligent prostheses that are fully implantable into the human body with respect to functionality, complexity, size, weight, and compactness. Design and development enforce collaboration of various disciplines including physicians, engineers, and scientists. The retina implant system can be taken as one sophisticated example of a prosthesis which bypasses neural defects and enables direct electrical stimulation of nerve cells. This micro implantable visual prosthesis assists blind patients to return to the normal course of life. The retina implant is intended for patients suffering from retinitis pigmentosa or macular degeneration. In this contribution, we focus on the epiretinal prosthesis and discuss topics like system design, data and power transfer, fabrication, packaging and testing. In detail, the system is based upon an implantable micro electro stimulator which is powered and controlled via a wireless inductive link. Microelectronic circuits for data encoding and stimulation are assembled on flexible substrates with an integrated electrode array. The implant system is encapsulated using parylene C and silicone rubber. Results extracted from experiments in vivo demonstrate the retinotopic activation of the visual cortex.

Encapsulating Non-Human Primate Multipotent Stromal Cells in Alginate via High Voltage for Cell-Based Therapies and Cryopreservation

PubMed Central

Gryshkov, Oleksandr; Pogozhykh, Denys; Hofmann, Nicola; Pogozhykh, Olena; Mueller, Thomas; Glasmacher, Birgit

2014-01-01

Alginate cell-based therapy requires further development focused on clinical application. To assess engraftment, risk of mutations and therapeutic benefit studies should be performed in an appropriate non-human primate model, such as the common marmoset (Callithrix jacchus). In this work we encapsulated amnion derived multipotent stromal cells (MSCs) from Callithrix jacchus in defined size alginate beads using a high voltage technique. Our results indicate that i) alginate-cell mixing procedure and cell concentration do not affect the diameter of alginate beads, ii) encapsulation of high cell numbers (up to 10×106 cells/ml) can be performed in alginate beads utilizing high voltage and iii) high voltage (15–30 kV) does not alter the viability, proliferation and differentiation capacity of MSCs post-encapsulation compared with alginate encapsulated cells produced by the traditional air-flow method. The consistent results were obtained over the period of 7 days of encapsulated MSCs culture and after cryopreservation utilizing a slow cooling procedure (1 K/min). The results of this work show that high voltage encapsulation can further be maximized to develop cell-based therapies with alginate beads in a non-human primate model towards human application. PMID:25259731

Self-Cleaning Microcavity Array for Photovoltaic Modules.

PubMed

Vüllers, Felix; Fritz, Benjamin; Roslizar, Aiman; Striegel, Andreas; Guttmann, Markus; Richards, Bryce S; Hölscher, Hendrik; Gomard, Guillaume; Klampaftis, Efthymios; Kavalenka, Maryna N

2018-01-24

Development of self-cleaning coatings is of great interest for the photovoltaic (PV) industry, as soiling of the modules can significantly reduce their electrical output and increase operational costs. We fabricated flexible polymeric films with novel disordered microcavity array (MCA) topography from fluorinated ethylene propylene (FEP) by hot embossing. Because of their superhydrophobicity with water contact angles above 150° and roll-off angles below 5°, the films possess self-cleaning properties over a wide range of tilt angles, starting at 10°, and contaminant sizes (30-900 μm). Droplets that impact the FEP MCA surface with velocities of the same order of magnitude as that of rain bounce off the surface without impairing its wetting properties. Additionally, the disordered MCA topography of the films enhances the performance of PV devices by improving light incoupling. Optical coupling of the FEP MCA films to a glass-encapsulated multicrystalline silicon solar cell results in 4.6% enhancement of the electrical output compared to that of an uncoated device.

Converting ceria polyhedral nanoparticles into single-crystal nanospheres.

PubMed

Feng, Xiangdong; Sayle, Dean C; Wang, Zhong Lin; Paras, M Sharon; Santora, Brian; Sutorik, Anthony C; Sayle, Thi X T; Yang, Yi; Ding, Yong; Wang, Xudong; Her, Yie-Shein

2006-06-09

Ceria nanoparticles are one of the key abrasive materials for chemical-mechanical planarization of advanced integrated circuits. However, ceria nanoparticles synthesized by existing techniques are irregularly faceted, and they scratch the silicon wafers and increase defect concentrations. We developed an approach for large-scale synthesis of single-crystal ceria nanospheres that can reduce the polishing defects by 80% and increase the silica removal rate by 50%, facilitating precise and reliable mass-manufacturing of chips for nanoelectronics. We doped the ceria system with titanium, using flame temperatures that facilitate crystallization of the ceria yet retain the titania in a molten state. In conjunction with molecular dynamics simulation, we show that under these conditions, the inner ceria core evolves in a single-crystal spherical shape without faceting, because throughout the crystallization it is completely encapsulated by a molten 1- to 2-nanometer shell of titania that, in liquid state, minimizes the surface energy. The principle demonstrated here could be applied to other oxide systems.

Pseudomonas aeruginosa biofilm growth inhibition on medical plastic materials by immobilized esterases and acylase.

PubMed

Kisch, Johannes Martin; Utpatel, Christian; Hilterhaus, Lutz; Streit, Wolfgang R; Liese, Andreas

2014-09-05

Biofilms are matrix-encapsulated cell aggregates that cause problems in technical and health-related areas; for example, 65 % of all human infections are biofilm associated. This is mainly due to their ameliorated resistance against antimicrobials and immune systems. Pseudomonas aeruginosa, a biofilm-forming organism, is commonly responsible for nosocomial infections. Biofilm development is partly mediated by signal molecules, such as acyl-homoserine lactones (AHLs) in Gram-negative bacteria. We applied horse liver esterase, porcine kidney acylase, and porcine liver esterase; these can hydrolyze AHLs, thereby inhibiting biofilm formation. As biofilm infections are often related to foreign material introduced into the human body, we immobilized the enzymes on medical plastic materials. Biofilm formation was quantified by Crystal Violet staining and confocal laser scanning microscopy, revealing up to 97 % (on silicone), 54 % (on polyvinyl chloride), and 77 % (on polyurethane) reduced biomass after 68 h growth. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Biocompatible Pressure Sensing Skins for Minimally Invasive Surgical Instruments

PubMed Central

Arabagi, Veaceslav; Felfoul, Ouajdi; Gosline, Andrew H.; Wood, Robert J.; Dupont, Pierre E.

2016-01-01

This paper presents 800-μm thick, biocompatible sensing skins composed of arrays of pressure sensors. The arrays can be configured to conform to the surface of medical instruments so as to act as disposable sensing skins. In particular, the fabrication of cylindrical geometries is considered here for use on endoscopes. The sensing technology is based on polydimethylsiloxane synthetic silicone encapsulated microchannels filled with a biocompatible salt-saturated glycerol solution, functioning as the conductive medium. A multi-layer manufacturing approach is introduced that enables stacking sensing microchannels, mechanical stress concentration features, and electrical routing via flexcircuits in a thickness of less than 1 mm. The proposed approach is inexpensive and does not require clean room tools or techniques. The mechanical stress concentration features are implemented using a patterned copper layer that serves to improve sensing range and sensitivity. Sensor performance is demonstrated experimentally using a sensing skin mounted on a neuroendoscope insertion cannula and is shown to outperform previously developed non-biocompatible sensors. PMID:27642266

A life prediction methodology for encapsulated solar cells

NASA Technical Reports Server (NTRS)

Coulbert, C. D.

1978-01-01

This paper presents an approach to the development of a life prediction methodology for encapsulated solar cells which are intended to operate for twenty years or more in a terrestrial environment. Such a methodology, or solar cell life prediction model, requires the development of quantitative intermediate relationships between local environmental stress parameters and the basic chemical mechanisms of encapsulant aging leading to solar cell failures. The use of accelerated/abbreviated testing to develop these intermediate relationships and in revealing failure modes is discussed. Current field and demonstration tests of solar cell arrays and the present laboratory tests to qualify solar module designs provide very little data applicable to predicting the long-term performance of encapsulated solar cells. An approach to enhancing the value of such field tests to provide data for life prediction is described.

High-Temperature High-Power Packaging Techniques for HEV Traction Applications

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

Elshabini, Aicha; Barlow, Fred D.

A key issue associated with the wider adoption of hybrid-electric vehicles (HEV) and plug in hybrid-electric vehicles (PHEV) is the implementation of the power electronic systems that are required in these products. One of the primary industry goals is the reduction in the price of these vehicles relative to the cost of traditional gasoline powered vehicles. Today these systems, such as the Prius, utilize one coolant loop for the engine at approximately 100 C coolant temperatures, and a second coolant loop for the inverter at 65 C. One way in which significant cost reduction of these systems could be achievedmore » is through the use of a single coolant loop for both the power electronics as well as the internal combustion engine (ICE). This change in coolant temperature significantly increases the junction temperatures of the devices and creates a number of challenges for both device fabrication and the assembly of these devices into inverters and converters for HEV and PHEV applications. Traditional power modules and the state-of-the-art inverters in the current HEV products, are based on chip and wire assembly and direct bond copper (DBC) on ceramic substrates. While a shift to silicon carbide (SiC) devices from silicon (Si) devices would allow the higher operating temperatures required for a single coolant loop, it also creates a number of challenges for the assembly of these devices into power inverters. While this traditional packaging technology can be extended to higher temperatures, the key issues are the substrate material and conductor stability, die bonding material, wire bonds, and bond metallurgy reliability as well as encapsulation materials that are stable at high operating temperatures. The larger temperature differential during power cycling, which would be created by higher coolant temperatures, places tremendous stress on traditional aluminum wire bonds that are used to interconnect power devices. Selection of the bond metallurgy and wire bond geometry can play a key role in mitigating this stress. An alternative solution would be to eliminate the wire bonds completely through a fundamentally different method of forming a reliable top side interconnect. Similarly, the solders used in most power modules exhibit too low of a liquidus to be viable solutions for maximum junction temperatures of 200 C. Commonly used encapsulation materials, such as silicone gels, also suffer from an inability to operate at 200 C for extended periods of time. Possible solutions to these problems exist in most cases but require changes to the traditional manufacturing process used in these modules. In addition, a number of emerging technologies such as Si nitride, flip-chip assembly methods, and the elimination of base-plates would allow reliable module development for operation of HEV and PHEV inverters at elevated junction temperatures.« less

Development of a Tumor Histologic-Specific, Nano-Encapsulated Contrast for Enhancing Magnetic Resonance Imaging of Prostate Cancer

DTIC Science & Technology

2008-04-01

Nano-Encapsulated Contrast for Enhancing Magnetic Resonance Imaging of Prostate Cancer PRINCIPAL INVESTIGATOR: Joel W. Slaton, M.D...2008 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Development of a Tumor Histologic-Specific, Nano-Encapsulated Contrast for Enhancing Magnetic...carry a contrast agent to human CaP cells growing in mice to enhance MR detection of cancer. Our work in the first year has focused on in vitro

Encapsulation of adenovirus serotype 5 in anionic lecithin liposomes using a bead-based immunoprecipitation technique enhances transfection efficiency.

PubMed

Mendez, Natalie; Herrera, Vanessa; Zhang, Lingzhi; Hedjran, Farah; Feuer, Ralph; Blair, Sarah L; Trogler, William C; Reid, Tony R; Kummel, Andrew C

2014-11-01

Oncolytic viruses (OVs) constitute a promising class of cancer therapeutics which exploit validated genetic pathways known to be deregulated in many cancers. To overcome an immune response and to enhance its potential use to treat primary and metastatic tumors, a method for liposomal encapsulation of adenovirus has been developed. The encapsulation of adenovirus in non-toxic anionic lecithin-cholesterol-PEG liposomes ranging from 140 to 180 nm in diameter have been prepared by self-assembly around the viral capsid. The encapsulated viruses retain their ability to infect cancer cells. Furthermore, an immunoprecipitation (IP) technique has shown to be a fast and effective method to extract non-encapsulated viruses and homogenize the liposomes remaining in solution. 78% of adenovirus plaque forming units were encapsulated and retained infectivity after IP processing. Additionally, encapsulated viruses have shown enhanced transfection efficiency up to 4 × higher compared to non-encapsulated Ads. Extracting non-encapsulated viruses from solution may prevent an adverse in vivo immune response and may enhance treatment for multiple administrations. Copyright © 2014 Elsevier Ltd. All rights reserved.

Encapsulation of Adenovirus Serotype 5 in Anionic Lecithin Liposomes using a Bead-Based Immunoprecipitation Technique Enhances Transfection Efficiency

PubMed Central

Mendez, N.; Herrera, V.; Zhang, L.; Hedjran, F.; Feuer, R.; Blair, S.; Trogler, W.; Reid, T.

2014-01-01

Oncolytic viruses (OVs) constitute a promising class of cancer therapeutics which exploit validated genetic pathways known to be deregulated in many cancers. To overcome an immune response and to enhance its potential use to treat primary and metastatic tumors, a method for liposomal encapsulation of adenovirus has been developed. The encapsulation of adenovirus in non-toxic anionic lecithin-cholesterol-PEG liposomes ranging from 140–180nm in diameter have been prepared by self-assembly around the viral capsid. The encapsulated viruses retain their ability to infect cancer cells. Furthermore, an immunoprecipitation (IP) technique has shown to be a fast and effective method to extract non-encapsulated viruses and homogenize the liposomes remaining in solution. 78% of adenovirus plaque forming units were encapsulated and retained infectivity after IP processing. Additionally, encapsulated viruses have shown enhanced transfection efficiency up to 4× higher compared to non-encapsulated Ads. Extracting non-encapsulated viruses from solution may prevent an adverse in vivo immune response and may enhance treatment for multiple administrations. PMID:25154663

Three-Dimensional Encapsulation of Saccharomyces cerevisiae in Silicate Matrices Creates Distinct Metabolic States as Revealed by Gene Chip Analysis.

PubMed

Fazal, Zeeshan; Pelowitz, Jennifer; Johnson, Patrick E; Harper, Jason C; Brinker, C Jeffrey; Jakobsson, Eric

2017-04-25

In order to design hybrid cellular/synthetic devices such as sensors and vaccines, it is important to understand how the metabolic state of living cells changes upon physical confinement within three-dimensional (3D) matrices. We analyze the gene expression patterns of stationary phase Saccharomyces cerevisiae (S. cerevisiae) cells encapsulated within three distinct nanostructured silica matrices and relate those patterns to known naturally occurring metabolic states. Silica encapsulation methods employed were lipid-templated mesophase silica thin films formed by cell-directed assembly (CDA), lipid-templated mesophase silica particles formed by spray drying (SD), and glycerol-doped silica gel monoliths prepared from an aqueous silicate (AqS+g) precursor solution. It was found that the cells for all three-encapsulated methods enter quiescent states characteristic of response to stress, albeit to different degrees and with differences in detail. By the measure of enrichment of stress-related gene ontology categories, we find that the AqS+g encapsulation is more amenable to the cells than CDA and SD encapsulation. We hypothesize that this differential response in the AqS+g encapsulation is related to four properties of the encapsulating gel: (1) oxygen permeability, (2) relative softness of the material, (3) development of a protective sheath around individual cells (visible in TEM micrographs vide infra), and (4) the presence of glycerol in the gel, which has been previously noted to serve as a protectant for encapsulated cells and can serve as the sole carbon source for S. cerevisiae under aerobic conditions. This work represents a combination of experiment and analysis aimed at the design and development of 3D encapsulation procedures to induce, and perhaps control, well-defined physiological behaviors.

Cell-penetrating peptides meditated encapsulation of protein therapeutics into intact red blood cells and its application

PubMed Central

Wang, Yinsong; Liu, Quan; Chung, Hee Sun; Kwon, Young Min; Shin, Meong Cheol; Lee, Kyuri; Yang, Victor C

2014-01-01

Red blood cells (RBCs) based drug carrier appears to be the most appealing for protein drugs due to their unmatched biocompatability, biodegradability, and long lifespan in the circulation. Numerous methods for encapsulating protein drugs into RBCs were developed, however, most of them induce partial disruption of the cell membrane, resulting in irreversible alterations in both physical and chemical properties of RBCs. Herein, we introduce a novel method for encapsulating proteins into intact RBCs, which was meditated by a cell penetrating peptide (CPP) developed in our lab—low molecular weight protamine (LMWP). L-asparaginase, one of the primary drugs used in treatment of acute lymphoblastic leukemia (ALL), was chosen as a model protein to illustrate the encapsulation into erythrocytes mediated by CPPs. In addition current treatment of ALL using different L-asparaginase delivery and encapsulation methods as well as their associated problems were also reviewed. PMID:24374002

Development of Hollow Steel Ball Macro-Encapsulated PCM for Thermal Energy Storage Concrete

PubMed Central

Dong, Zhijun; Cui, Hongzhi; Tang, Waiching; Chen, Dazhu; Wen, Haibo

2016-01-01

The application of thermal energy storage with phase change materials (PCMs) for energy efficiency of buildings grew rapidly in the last few years. In this research, octadecane paraffin was served as a PCM, and a structural concrete with the function of indoor temperature control was developed by using a macro-encapsulated PCM hollow steel ball (HSB). The macro-encapsulated PCM-HSB was prepared by incorporation of octadecane into HSBs through vacuum impregnation. Test results showed that the maximum percentage of octadecane carried by HSBs was 80.3% by mass. The macro-encapsulated PCM-HSB has a latent heat storage capacity as high as 200.5 J/g. The compressive strength of concrete with macro-encapsulated PCM-HSB at 28 days ranged from 22 to 40 MPa. The indoor thermal performance test revealed that concrete with macro-encapsulated octadecane-HSB was capable of reducing the peak indoor air temperature and the fluctuation of indoor temperature. It can be very effective in transferring the heating and cooling loads away from the peak demand times. PMID:28787859

Development of Hollow Steel Ball Macro-Encapsulated PCM for Thermal Energy Storage Concrete.

PubMed

Dong, Zhijun; Cui, Hongzhi; Tang, Waiching; Chen, Dazhu; Wen, Haibo

2016-01-19

The application of thermal energy storage with phase change materials (PCMs) for energy efficiency of buildings grew rapidly in the last few years. In this research, octadecane paraffin was served as a PCM, and a structural concrete with the function of indoor temperature control was developed by using a macro-encapsulated PCM hollow steel ball (HSB). The macro-encapsulated PCM-HSB was prepared by incorporation of octadecane into HSBs through vacuum impregnation. Test results showed that the maximum percentage of octadecane carried by HSBs was 80.3% by mass. The macro-encapsulated PCM-HSB has a latent heat storage capacity as high as 200.5 J/g. The compressive strength of concrete with macro-encapsulated PCM-HSB at 28 days ranged from 22 to 40 MPa. The indoor thermal performance test revealed that concrete with macro-encapsulated octadecane-HSB was capable of reducing the peak indoor air temperature and the fluctuation of indoor temperature. It can be very effective in transferring the heating and cooling loads away from the peak demand times.

Silk sericin-alginate-chitosan microcapsules: hepatocytes encapsulation for enhanced cellular functions.

PubMed

Nayak, Sunita; Dey, Sanchareeka; Kundu, Subhas C

2014-04-01

The encapsulation based technology permits long-term delivery of desired therapeutic products in local regions of body without the need of immunosuppressant drugs. In this study microcapsules composed of sericin and alginate micro bead as inner core and with an outer chitosan shell are prepared. This work is proposed for live cell encapsulation for potential therapeutic applications. The sericin protein is obtained from cocoons of non-mulberry silkworm Antheraea mylitta. The sericin-alginate micro beads are prepared via ionotropic gelation under high applied voltage. The beads further coated with chitosan and crosslinked with genipin. The microcapsules developed are nearly spherical in shape with smooth surface morphology. Alamar blue assay and confocal microscopy indicate high cell viability and uniform encapsulated cell distribution within the sericin-alginate-chitosan microcapsules indicating that the microcapsules maintain favourable microenvironment for the cells. The functional analysis of encapsulated cells demonstrates that the glucose consumption, urea secretion rate and intracellular albumin content increased in the microcapsules. The study suggests that the developed sericin-alginate-chitosan microcapsule contributes towards the development of cell encapsulation model. It also offers to generate enriched population of metabolically and functionally active cells for the future therapeutics especially for hepatocytes transplantation in acute liver failure. Copyright © 2014 Elsevier B.V. All rights reserved.

Encapsulation in the food industry: a review.

PubMed

Gibbs, B F; Kermasha, S; Alli, I; Mulligan, C N

1999-05-01

Encapsulation involves the incorporation of food ingredients, enzymes, cells or other materials in small capsules. Applications for this technique have increased in the food industry since the encapsulated materials can be protected from moisture, heat or other extreme conditions, thus enhancing their stability and maintaining viability. Encapsulation in foods is also utilized to mask odours or tastes. Various techniques are employed to form the capsules, including spray drying, spray chilling or spray cooling, extrusion coating, fluidized bed coating, liposome entrapment, coacervation, inclusion complexation, centrifugal extrusion and rotational suspension separation. Each of these techniques is discussed in this review. A wide variety of foods is encapsulated--flavouring agents, acids bases, artificial sweeteners, colourants, preservatives, leavening agents, antioxidants, agents with undesirable flavours, odours and nutrients, among others. The use of encapsulation for sweeteners such as aspartame and flavours in chewing gum is well known. Fats, starches, dextrins, alginates, protein and lipid materials can be employed as encapsulating materials. Various methods exist to release the ingredients from the capsules. Release can be site-specific, stage-specific or signalled by changes in pH, temperature, irradiation or osmotic shock. In the food industry, the most common method is by solvent-activated release. The addition of water to dry beverages or cake mixes is an example. Liposomes have been applied in cheese-making, and its use in the preparation of food emulsions such as spreads, margarine and mayonnaise is a developing area. Most recent developments include the encapsulation of foods in the areas of controlled release, carrier materials, preparation methods and sweetener immobilization. New markets are being developed and current research is underway to reduce the high production costs and lack of food-grade materials.

Dose verification of eye plaque brachytherapy using spectroscopic dosimetry.

PubMed

Jarema, T; Cutajar, D; Weaver, M; Petasecca, M; Lerch, M; Kejda, A; Rosenfeld, A

2016-09-01

Eye plaque brachytherapy has been developed and refined for the last 80 years, demonstrating effective results in the treatment of ocular malignancies. Current dosimetry techniques for eye plaque brachytherapy (such as TLD- and film-based techniques) are time consuming and cannot be used prior to treatment in a sterile environment. The measurement of the expected dose distribution within the eye, prior to insertion within the clinical setting, would be advantageous, as any errors in source loading will lead to an erroneous dose distribution and inferior treatment outcomes. This study investigated the use of spectroscopic dosimetry techniques for real-time quality assurance of I-125 based eye plaques, immediately prior to insertion. A silicon detector based probe, operating in spectroscopy mode was constructed, containing a small (1 mm(3)) silicon detector, mounted within a ceramic holder, all encapsulated within a rubber sheath to prevent water infiltration of the electronics. Preliminary tests of the prototype demonstrated that the depth dose distribution through the central axis of an I-125 based eye plaque may be determined from AAPM Task Group 43 recommendations to a deviation of 6 % at 3 mm depth, 7 % at 5 mm depth, 1 % at 10 mm depth and 13 % at 20 mm depth, with the deviations attributed to the construction of the probe. A new probe design aims to reduce these discrepancies, however the concept of spectroscopic dosimetry shows great promise for use in eye plaque quality assurance in the clinical setting.

Highly-compliant, microcable neuroelectrodes fabricated from thin-film gold and PDMS.

PubMed

McClain, Maxine A; Clements, Isaac P; Shafer, Richard H; Bellamkonda, Ravi V; LaPlaca, Michelle C; Allen, Mark G

2011-04-01

Bio-electrodes have traditionally been made of materials such as metal and silicon that are much stiffer than the tissue from which they record or stimulate. This difference in mechanical compliance can cause incomplete or ineffective contact with the tissue. The electrode stiffness has also been hypothesized to cause chronic low-grade injury and scar-tissue encapsulation, reducing stimulation and recording efficiency. As an initial step to resolve these issues with electrode performance, we have developed and characterized electrically-functional, low-Young's modulus, microcable-shaped neuroelectrodes and demonstrated electrophysiological recording functionality. The microcable geometry gives the electrodes a similar footprint to traditional wire and microwire neuroelectrodes, while reducing the difference in Young's modulus from nervous tissue by orders of magnitude. The electrodes are composed of PDMS and thin-film gold, affording them a high-level of compliance that is well suited for in vivo applications. The composite Young's modulus of the electrode was experimentally determined to be 1.81 ± 0.01 MPa. By incorporating a high-tear-strength silicone, Sylgard 186, the load at failure was increased by 92%, relative to that of the commonly used Sylgard 184. The microcable electrodes were also electromechanically tested, with measurable conductivity (220 kΩ) at an average 8% strain (n = 2) after the application of 200% strain. Electrophysiological recording is demonstrated by wrapping the electrode around a peripheral nerve, utilizing the compliance and string-like profile of the electrode for effective recording in nerve tissue.

Black silicon: fabrication methods, properties and solar energy applications

DOE PAGES

Liu, Xiaogang; Coxon, Paul R.; Peters, Marius; ...

2014-08-04

Black silicon (BSi) represents a very active research area in renewable energy materials. The rise of BSi as a focus of study for its fundamental properties and potentially lucrative practical applications is shown by several recent results ranging from solar cells and light-emitting devices to antibacterial coatings and gas-sensors. Here in this article, the common BSi fabrication techniques are first reviewed, including electrochemical HF etching, stain etching, metal-assisted chemical etching, reactive ion etching, laser irradiation and the molten salt Fray-Farthing-Chen-Cambridge (FFC-Cambridge) process. The utilization of BSi as an anti-reflection coating in solar cells is then critically examined and appraised, basedmore » upon strategies towards higher efficiency renewable solar energy modules. Methods of incorporating BSi in advanced solar cell architectures and the production of ultra-thin and flexible BSi wafers are also surveyed. Particular attention is given to routes leading to passivated BSi surfaces, which are essential for improving the electrical properties of any devices incorporating BSi, with a special focus on atomic layer deposition of Al 2O 3. Finally, three potential research directions worth exploring for practical solar cell applications are highlighted, namely, encapsulation effects, the development of micro-nano dual-scale BSi, and the incorporation of BSi into thin solar cells. It is intended that this paper will serve as a useful introduction to this novel material and its properties, and provide a general overview of recent progress in research currently being undertaken for renewable energy applications.« less

Development of antimicrobial coating by later-by-layer dip coating of chlorhexidine-loaded micelles.

PubMed

Tambunlertchai, Supreeda; Srisang, Siriwan; Nasongkla, Norased

2017-06-01

Layer-by-layer (LbL) dip coating, accompanying with the use of micelle structure, allows hydrophobic molecules to be coated on medical devices' surface via hydrogen bonding interaction. In addition, micelle structure also allows control release of encapsulated compound. In this research, we investigated methods to coat and maximize the amount of chlorhexidine (CHX) on silicone surface through LbL dip coating method utilizing hydrogen bonding interaction between PEG on micelle corona and PAA. The number of coated cycles was varied in the process and 90 coating cycles provided the maximum amount of CHX loaded onto the surface. In addition, pre-coating the surface with PAA enhanced the amount of coated CHX by 20%. Scanning electron microscope (SEM) and Fourier Transform Infrared Spectroscopy (FTIR) were used to validate and characterize the coating. For control release aspect, the coated film tended to disrupt at physiological condition; hence chemical crosslinking was performed to minimize the disruption and maximize the release time. Chemical crosslinking at pH 2.5 and 4.5 were performed in the process. It was found that chemical crosslinking could help extend the release period up to 18 days. This was significantly longer when compared to the non-crosslinking silicone tube that could only prolong the release for 5 days. In addition, chemical crosslinking at pH 2.5 gave higher and better initial burst release, release period and antimicrobial properties than that of pH 4.5 or the normal used pH for chemical crosslinking process.

Direct-write liquid phase transformations with a scanning transmission electron microscope

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

Unocic, Raymond R.; Lupini, Andrew R.; Borisevich, Albina Y.

The highly energetic electron beam from a scanning transmission electron microscope (STEM) can induce local changes in the state of matter, ranging from local knock-out and atomic movement, to amorphization/crystallization, and chemical/electrochemical reactions occuring at localized liquid-solid and gas-solid interfaces. To date, fundamental studies of e-beam induced phenomena and practical applications have been limited by conventional e-beam rastering modes that allow only for uniform e-beam exposures. Here we develop an automated liquid phase nanolithography method that is capable of directly writing nanometer scaled features within silicon nitride encapsulated liquid cells. An external beam control system, connected to the scan coilsmore » of an aberration-corrected STEM, is used to precisely control the position, dwell time, and scan velocity of a sub-nanometer STEM probe. Site-specific locations in a sealed liquid cell containing an aqueous solution of H 2PdCl 4 are irradiated to controllably deposit palladium onto silicon nitride membranes. We determine the threshold electron dose required for the radiolytic deposition of metallic palladium, explore the influence of electron dose on the feature size and morphology of nanolithographically patterned nanostructures, and propose a feedback-controlled monitoring method for active control of the nanofabricated structures through STEM detector signal monitoring. As a result, this approach enables both fundamental studies of electron beam induced interactions with matter, as well as opens a pathway to fabricate nanostructures with tailored architectures and chemistries via shape-controlled nanolithographic patterning from liquid phase precursors.« less

Direct-write liquid phase transformations with a scanning transmission electron microscope

DOE PAGES

Unocic, Raymond R.; Lupini, Andrew R.; Borisevich, Albina Y.; ...

2016-08-03

The highly energetic electron beam from a scanning transmission electron microscope (STEM) can induce local changes in the state of matter, ranging from local knock-out and atomic movement, to amorphization/crystallization, and chemical/electrochemical reactions occuring at localized liquid-solid and gas-solid interfaces. To date, fundamental studies of e-beam induced phenomena and practical applications have been limited by conventional e-beam rastering modes that allow only for uniform e-beam exposures. Here we develop an automated liquid phase nanolithography method that is capable of directly writing nanometer scaled features within silicon nitride encapsulated liquid cells. An external beam control system, connected to the scan coilsmore » of an aberration-corrected STEM, is used to precisely control the position, dwell time, and scan velocity of a sub-nanometer STEM probe. Site-specific locations in a sealed liquid cell containing an aqueous solution of H 2PdCl 4 are irradiated to controllably deposit palladium onto silicon nitride membranes. We determine the threshold electron dose required for the radiolytic deposition of metallic palladium, explore the influence of electron dose on the feature size and morphology of nanolithographically patterned nanostructures, and propose a feedback-controlled monitoring method for active control of the nanofabricated structures through STEM detector signal monitoring. As a result, this approach enables both fundamental studies of electron beam induced interactions with matter, as well as opens a pathway to fabricate nanostructures with tailored architectures and chemistries via shape-controlled nanolithographic patterning from liquid phase precursors.« less

Encapsulation materials research

NASA Technical Reports Server (NTRS)

Willis, P. B.

1984-01-01

Encapsulation materials for solar cells were investigated. The different phases consisted of: (1) identification and development of low cost module encapsulation materials; (2) materials reliability examination; and (3) process sensitivity and process development. It is found that outdoor photothermal aging devices (OPT) are the best accelerated aging methods, simulate worst case field conditions, evaluate formulation and module performance and have a possibility for life assessment. Outdoor metallic copper exposure should be avoided, self priming formulations have good storage stability, stabilizers enhance performance, and soil resistance treatment is still effective.

Preserving viability of Lactobacillus rhamnosus GG in vitro and in vivo by a new encapsulation system.

PubMed

Li, Ran; Zhang, Yufeng; Polk, D Brent; Tomasula, Peggy M; Yan, Fang; Liu, LinShu

2016-05-28

Probiotics have shown beneficial effects on health and prevention of diseases in humans. However, a concern for application of probiotics is the loss of viability during storage and gastrointestinal transit. The aim of this study was to develop an encapsulation system to preserve viability of probiotics when they are administrated orally and apply Lactobacillus rhamnosus GG (LGG) as a probiotic model to evaluate the effectiveness of this approach using in vitro and in vivo experiments. LGG was encapsulated in hydrogel beads prepared using pectin, a food grade polysaccharide, glucose, and calcium chloride, and lyophilized by freeze-drying. Encapsulated LGG was cultured in vitro under the condition that mimicked the physiological environment of the human gastrointestinal tract. Compared to non-encapsulated LGG, encapsulation increased tolerance of LGG in the acid condition, protected LGG from protease digestion, and improved shelf time when stored at the ambient condition, in regard of survivability and production of p40, a known LGG-derived protein involved in LGG's beneficial effects on intestinal homeostasis. To evaluate the effects of encapsulation on p40 production in vivo and prevention of intestinal inflammation by LGG, mice were gavaged with LGG containing beads and treated with dextran sulphate sodium (DSS) to induce intestinal injury and colitis. Compared to non-encapsulated LGG, encapsulated LGG enhanced more p40 production in mice, and exerted higher levels of effects on prevention of DSS-induced colonic injury and colitis and suppression of pro-inflammatory cytokine production. These data indicated that the encapsulation system developed in this study preserves viability of LGG in vitro and in vivo, leading to longer shelf time and enhancing the functions of LGG in the gastrointestinal tract. Thus, this encapsulation approach may have the potential application for improving efficacy of probiotics. Copyright © 2016 Elsevier B.V. All rights reserved.

The Poisson distribution and beyond: methods for microfluidic droplet production and single cell encapsulation.

PubMed

Collins, David J; Neild, Adrian; deMello, Andrew; Liu, Ai-Qun; Ai, Ye

2015-09-07

There is a recognized and growing need for rapid and efficient cell assays, where the size of microfluidic devices lend themselves to the manipulation of cellular populations down to the single cell level. An exceptional way to analyze cells independently is to encapsulate them within aqueous droplets surrounded by an immiscible fluid, so that reagents and reaction products are contained within a controlled microenvironment. Most cell encapsulation work has focused on the development and use of passive methods, where droplets are produced continuously at high rates by pumping fluids from external pressure-driven reservoirs through defined microfluidic geometries. With limited exceptions, the number of cells encapsulated per droplet in these systems is dictated by Poisson statistics, reducing the proportion of droplets that contain the desired number of cells and thus the effective rate at which single cells can be encapsulated. Nevertheless, a number of recently developed actively-controlled droplet production methods present an alternative route to the production of droplets at similar rates and with the potential to improve the efficiency of single-cell encapsulation. In this critical review, we examine both passive and active methods for droplet production and explore how these can be used to deterministically and non-deterministically encapsulate cells.

The status of lightweight photovoltaic space array technology based on amorphous silicon solar cells

NASA Technical Reports Server (NTRS)

Hanak, Joseph J.; Kaschmitter, Jim

1991-01-01

Ultralight, flexible photovoltaic (PV) array of amorphous silicon (a-Si) was identified as a potential low cost power source for small satellites. A survey was conducted of the status of the a-Si PV array technology with respect to present and future performance, availability, cost, and risks. For existing, experimental array blankets made of commercial cell material, utilizing metal foil substrates, the Beginning of Life (BOL) performance at Air Mass Zero (AM0) and 35 C includes total power up to 200 W, power per area of 64 W/sq m and power per weight of 258 W/kg. Doubling of power per weight occurs when polyimide substrates are used. Estimated End of Life (EOL) power output after 10 years in a nominal low earth orbit would be 80 pct. of BOL, the degradation being due to largely light induced effects (-10 to -15 pct.) and in part (-5 pct.) to space radiation. Predictions for the year 1995 for flexible PV arrays, made on the basis of published results for rigid a-Si modules, indicate EOL power output per area and per weight of 105 W/sq m and 400 W/kg, respectively, while predictions for the late 1990s based on existing U.S. national PV program goals indicate EOL values of 157 W/sq m and 600 W/kg. Cost estimates by vendors for 200 W ultralight arrays in volume of over 1000 units range from $100/watt to $125/watt. Identified risks include the lack of flexible, space compatible encapsulant, the lack of space qualification effort, recent partial or full acquisitions of US manufacturers of a-Si cells by foreign firms, and the absence of a national commitment for a long range development program toward developing of this important power source for space.

High-Responsivity Graphene–Boron Nitride Photodetector and Autocorrelator in a Silicon Photonic Integrated Circuit

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

Shiue, Ren-Jye; Gao, Yuanda; Wang, Yifei

2015-11-11

Graphene and other two-dimensional (2D) materials have emerged as promising materials for broadband and ultrafast photodetection and optical modulation. These optoelectronic capabilities can augment complementary metal–oxide–semiconductor (CMOS) devices for high-speed and low-power optical interconnects. Here, we demonstrate an on-chip ultrafast photodetector based on a two-dimensional heterostructure consisting of high-quality graphene encapsulated in hexagonal boron nitride. Coupled to the optical mode of a silicon waveguide, this 2D heterostructure-based photodetector exhibits a maximum responsivity of 0.36 A/W and high-speed operation with a 3 dB cutoff at 42 GHz. From photocurrent measurements as a function of the top-gate and source-drain voltages, we concludemore » that the photoresponse is consistent with hot electron mediated effects. At moderate peak powers above 50 mW, we observe a saturating photocurrent consistent with the mechanisms of electron–phonon supercollision cooling. This nonlinear photoresponse enables optical on-chip autocorrelation measurements with picosecond-scale timing resolution and exceptionally low peak powers.« less

Confining metal-halide perovskites in nanoporous thin films

PubMed Central

Demchyshyn, Stepan; Roemer, Janina Melanie; Groiß, Heiko; Heilbrunner, Herwig; Ulbricht, Christoph; Apaydin, Dogukan; Böhm, Anton; Rütt, Uta; Bertram, Florian; Hesser, Günter; Scharber, Markus Clark; Sariciftci, Niyazi Serdar; Nickel, Bert; Bauer, Siegfried; Głowacki, Eric Daniel; Kaltenbrunner, Martin

2017-01-01

Controlling the size and shape of semiconducting nanocrystals advances nanoelectronics and photonics. Quantum-confined, inexpensive, solution-derived metal halide perovskites offer narrowband, color-pure emitters as integral parts of next-generation displays and optoelectronic devices. We use nanoporous silicon and alumina thin films as templates for the growth of perovskite nanocrystallites directly within device-relevant architectures without the use of colloidal stabilization. We find significantly blue-shifted photoluminescence emission by reducing the pore size; normally infrared-emitting materials become visibly red, and green-emitting materials become cyan and blue. Confining perovskite nanocrystals within porous oxide thin films drastically increases photoluminescence stability because the templates auspiciously serve as encapsulation. We quantify the template-induced size of the perovskite crystals in nanoporous silicon with microfocus high-energy x-ray depth profiling in transmission geometry, verifying the growth of perovskite nanocrystals throughout the entire thickness of the nanoporous films. Low-voltage electroluminescent diodes with narrow, blue-shifted emission fabricated from nanocrystalline perovskites grown in embedded nanoporous alumina thin films substantiate our general concept for next-generation photonic devices. PMID:28798959

A molecular method to assess bioburden embedded within silicon-based resins used on modern spacecraft materials

NASA Astrophysics Data System (ADS)

Stam, Christina N.; Bruckner, James; Spry, J. Andy; Venkateswaran, Kasthuri; La Duc, Myron T.

2012-07-01

Current assessments of bioburden embedded in spacecraft materials are based on work performed in the Viking era (1970s), and the ability to culture organisms extracted from such materials. To circumvent the limitations of such approaches, DNA-based techniques were evaluated alongside established culturing techniques to determine the recovery and survival of bacterial spores encapsulated in spacecraft-qualified polymer materials. Varying concentrations of Bacillus pumilus SAFR-032 spores were completely embedded in silicone epoxy. An organic dimethylacetamide-based solvent was used to digest the epoxy and spore recovery was evaluated via gyrB-targeted qPCR, direct agar plating, most probably number analysis, and microscopy. Although full-strength solvent was shown to inhibit the germination and/or outgrowth of spores, dilution in excess of 100-fold allowed recovery with no significant decrease in cultivability. Similarly, qPCR (quantitative PCR) detection sensitivities as low as ~103 CFU ml-1 were achieved upon removal of inhibitory substances associated with the epoxy and/or solvent. These detection and enumeration methods show promise for use in assessing the embedded bioburden of spacecraft hardware.

Lattice Dynamics Study of Phonon Instability and Thermal Properties of Type-I Clathrate K8Si46 under High Pressure

PubMed Central

Zhang, Wei; Zeng, Zhao Yi; Ge, Ni Na; Li, Zhi Guo

2016-01-01

For a further understanding of the phase transitions mechanism in type-I silicon clathrates K8Si46, ab initio self-consistent electronic calculations combined with linear-response method have been performed to investigate the vibrational properties of alkali metal K atoms encapsulated type-I silicon-clathrate under pressure within the framework of density functional perturbation theory. Our lattice dynamics simulation results showed that the pressure induced phase transition of K8Si46 was believed to be driven by the phonon instability of the calthrate lattice. Analysis of the evolution of the partial phonon density of state with pressure, a legible dynamic picture for both guest K atoms and host lattice, was given. In addition, based on phonon calculations and combined with quasi-harmonic approximation, the specific heat of K8Si46 was derived, which agreed very well with experimental results. Also, other important thermal properties including the thermal expansion coefficients and Grüneisen parameters of K8Si46 under different temperature and pressure were also predicted. PMID:28773736

Enhanced cellular uptake of size-separated lipophilic silicon nanoparticles

NASA Astrophysics Data System (ADS)

Kusi-Appiah, Aubrey E.; Mastronardi, Melanie L.; Qian, Chenxi; Chen, Kenneth K.; Ghazanfari, Lida; Prommapan, Plengchart; Kübel, Christian; Ozin, Geoffrey A.; Lenhert, Steven

2017-03-01

Specific size, shape and surface chemistry influence the biological activity of nanoparticles. In the case of lipophilic nanoparticles, which are widely used in consumer products, there is evidence that particle size and formulation influences skin permeability and that lipophilic particles smaller than 6 nm can embed in lipid bilayers. Since most nanoparticle synthetic procedures result in mixtures of different particles, post-synthetic purification promises to provide insights into nanostructure-function relationships. Here we used size-selective precipitation to separate lipophilic allyl-benzyl-capped silicon nanoparticles into monodisperse fractions within the range of 1 nm to 5 nm. We measured liposomal encapsulation and cellular uptake of the monodisperse particles and found them to have generally low cytotoxicities in Hela cells. However, specific fractions showed reproducibly higher cytotoxicity than other fractions as well as the unseparated ensemble. Measurements indicate that the cytotoxicity mechanism involves oxidative stress and the differential cytotoxicity is due to enhanced cellular uptake by specific fractions. The results indicate that specific particles, with enhanced suitability for incorporation into lipophilic regions of liposomes and subsequent in vitro delivery to cells, are enriched in certain fractions.

A Comparative Cytotoxic Evaluation of Disulfiram Encapsulated PLGA Nanoparticles on MCF-7 Cells.

PubMed

Fasehee, Hamidreza; Ghavamzadeh, Ardeshir; Alimoghaddam, Kamran; Ghaffari, Seyed-Hamidollah; Faghihi, Shahab

2017-04-01

Background: Disulfiram is oral aldehyde dehydrogenase (ALDH) inhibitor that has been used in the treatment of alcoholism. Recent studies show that this drug has anticancer properties; however, its rapid degradation has limited its clinical application. Encapsulation of disulfiram polymeric nanoparticles (NPs) may improve its anticancer activities and protect rapid degradation of the drug. Materials and Methods: A poly (lactide-co-Glycolide) (PLGA) was developed for encapsulation of disulfiram and its delivery into breast cancer cells. Disulfiram encapsulated PLGA NPs were prepared by nanoprecipitation method and were characterized by Scanning Electron Microscopy (SEM). The loading and encapsulation efficiency of NPs were determined using UV-Visible spectroscopy. Cell cytotoxicity of free and encapsulated form of disulfiram is also determined using MTT assay. Results: Disulfiram encapsulated PLGA NPs had uniform size with 165 nm. Drug loading and entrapment efficiency were 5.35 ±0.03% and 58.85±1.01%. The results of MTT assay showed that disulfiram encapsulated PLGA NPs were more potent in induction of apoptosis compare to free disulfiram. Conclusion: Based on the results obtained in the present study it can be concluded that encapsulation of disulfiram with PLGA can protect its degradation in improve its cytotoxicity on breast cancer cells.

Hermetic diamond capsules for biomedical implants enabled by gold active braze alloys.

PubMed

Lichter, Samantha G; Escudié, Mathilde C; Stacey, Alastair D; Ganesan, Kumaravelu; Fox, Kate; Ahnood, Arman; Apollo, Nicholas V; Kua, Dunstan C; Lee, Aaron Z; McGowan, Ceara; Saunders, Alexia L; Burns, Owen; Nayagam, David A X; Williams, Richard A; Garrett, David J; Meffin, Hamish; Prawer, Steven

2015-01-01

As the field of biomedical implants matures the functionality of implants is rapidly increasing. In the field of neural prostheses this is particularly apparent as researchers strive to build devices that interact with highly complex neural systems such as vision, hearing, touch and movement. A retinal implant, for example, is a highly complex device and the surgery, training and rehabilitation requirements involved in deploying such devices are extensive. Ideally, such devices will be implanted only once and will continue to function effectively for the lifetime of the patient. The first and most pivotal factor that determines device longevity is the encapsulation that separates the sensitive electronics of the device from the biological environment. This paper describes the realisation of a free standing device encapsulation made from diamond, the most impervious, long lasting and biochemically inert material known. A process of laser micro-machining and brazing is described detailing the fabrication of hermetic electrical feedthroughs and laser weldable seams using a 96.4% gold active braze alloy, another material renowned for biochemical longevity. Accelerated ageing of the braze alloy, feedthroughs and hermetic capsules yielded no evidence of corrosion and no loss of hermeticity. Samples of the gold braze implanted for 15 weeks, in vivo, caused minimal histopathological reaction and results were comparable to those obtained from medical grade silicone controls. The work described represents a first account of a free standing, fully functional hermetic diamond encapsulation for biomedical implants, enabled by gold active alloy brazing and laser micro-machining. Copyright © 2015 Elsevier Ltd. All rights reserved.

Corrosion Issues for Ceramics in Gas Turbines

NASA Technical Reports Server (NTRS)

Jacobson, Nathan S.; Fox, Dennis S.; Smialek, James L.; Opila, Elizabeth J.; Tortorelli, Peter F.; More, Karren L.; Nickel, Klaus G.; Hirata, Takehiko; Yoshida, Makoto; Yuri, Isao

2000-01-01

The requirements for hot-gas-path materials in gas turbine engines are demanding. These materials must maintain high strength and creep resistance in a particularly aggressive environment. A typical gas turbine environment involves high temperatures, rapid gas flow rates, high pressures, and a complex mixture of aggressive gases. Figure 26.1 illustrates the requirements for components of an aircraft engine and critical issues [1]. Currently, heat engines are constructed of metal alloys, which meet these requirements within strict temperature limits. In order to extend these temperature limits, ceramic materials have been considered as potential engine materials, due to their high melting points and stability at high temperatures. These materials include oxides, carbides, borides, and nitrides. Interest in using these materials in engines appears to have begun in the 1940s with BeO-based porcelains [2]. During the 1950s, the efforts shifted to cermets. These were carbide-based materials intended to exploit the best properties of metals and ceramics. During the 1960s and 1970s, the silicon-based ceramics silicon carbide (SiC) and silicon nitride (Si3N4) were extensively developed. Although the desirable high-temperature properties of SiC and Si3N4 had long been known, consolidation of powders into component-sized bodies required the development of a series of specialized processing routes [3]. For SiC, the major consolidation routes are reaction bonding, hot-pressing, and sintering. The use of boron and carbon as additives which enable sintering was a particularly noteworthy advance [4]. For Si3N4 the major consolidation routes are reaction bonding and hot pressing [5]. Reaction-bonding involves nitridation of silicon powder. Hot pressing involves addition of various refractory oxides, such as magnesia (MgO), alumina (Al2O3), and yttria (y2O3). Variations on these processes include a number of routes including Hot Isostatic Pressing (HIP), gas-pressure sintering, sinter-HIPing, and Encapsulation-HIPing. It is important to note that each process involves the addition of secondary elements, which later were shown to dramatically influence oxidation and corrosion behavior. As dense bodies of silicon-based ceramics became more readily available, their desirable high temperature properties were confirmed. These materials retained strength to very high temperatures (i.e. 1300-1400 C). Further, they were lightweight and made from abundant materials. SiC and Si3N4 therefore emerged as leading ceramic candidates for components in heat engines, designed to operate at higher temperatures for better performance and fuel efficiency. The first US programs for ceramics in heat engines have been reviewed [6]. Selected programs on ceramic engine parts are summarized here in regard to their contributions to understanding the corrosion behavior of a heat engine environment.

Cell-penetrating peptides meditated encapsulation of protein therapeutics into intact red blood cells and its application.

PubMed

He, Huining; Ye, Junxiao; Wang, Yinsong; Liu, Quan; Chung, Hee Sun; Kwon, Young Min; Shin, Meong Cheol; Lee, Kyuri; Yang, Victor C

2014-02-28

Red blood cells (RBCs) based drug carrier appears to be the most appealing for protein drugs due to their unmatched biocompatability, biodegradability, and long lifespan in the circulation. Numerous methods for encapsulating protein drugs into RBCs were developed, however, most of them induce partial disruption of the cell membrane, resulting in irreversible alterations in both physical and chemical properties of RBCs. Herein, we introduce a novel method for encapsulating proteins into intact RBCs, which was meditated by a cell penetrating peptide (CPP) developed in our lab-low molecular weight protamine (LMWP). l-asparaginase, one of the primary drugs used in treatment of acute lymphoblastic leukemia (ALL), was chosen as a model protein to illustrate the encapsulation into erythrocytes mediated by CPPs. In addition current treatment of ALL using different l-asparaginase delivery and encapsulation methods as well as their associated problems were also reviewed. Copyright © 2013 Elsevier B.V. All rights reserved.

Amidase encapsulated O-carboxymethyl chitosan nanoparticles for vaccine delivery.

PubMed

Smitha, K T; Sreelakshmi, M; Nisha, N; Jayakumar, R; Biswas, Raja

2014-02-01

This work reports the development of amidase encapsulated O-carboxymethyl chitosan nanoparticles (Ami-O-CMC NPs) of 300±50 nm size by ionic cross-linking method. The prepared Ami-O-CMC NPs had an encapsulation efficiency of 55.39%. Haemolysis assay and cytotoxicity studies proved the hemocompatibility and cytocompatibility of the prepared NPs. The sustained release of Ami from the NPs is expected to prolong its immunogenicity and in turn lead to development of better protective immunity against Staphylococcus aureus infections. Copyright © 2013 Elsevier B.V. All rights reserved.

Development of Damp-Heat Resistant Self-Primed EVA and Non-EVA Encapsulant Formulations at NREL

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

Pern, F. J.; Jorgensen, G. J.

2005-11-01

Self-primed ethylene-vinyl acetate (EVA) and non-EVA (PMG) encapsulant formulations were developed that have greater resistance to damp heat exposure at 85 deg C and 85% relative humidity (RH) (in terms of adhesion strength to glass substrates) than a commonly used commercial EVA product. The self-primed EVA formulations were developed on the basis of high-performing glass priming formulations that have previously proven to significantly enhance the adhesion strength of unprimed and primed EVA films on glass substrates during damp heat exposure. The PMG encapsulant formulations were based on an ethylene-methylacrylate copolymer containing glycidyl methacrylate.

Low-temperature crack-free Si3N4 nonlinear photonic circuits for CMOS-compatible optoelectronic co-integration

NASA Astrophysics Data System (ADS)

Casale, Marco; Kerdiles, Sebastien; Brianceau, Pierre; Hugues, Vincent; El Dirani, Houssein; Sciancalepore, Corrado

2017-02-01

In this communication, authors report for the first time on the fabrication and testing of Si3N4 non-linear photonic circuits for CMOS-compatible monolithic co-integration with silicon-based optoelectronics. In particular, a novel process has been developed to fabricate low-loss crack-free Si3N4 750-nm-thick films for Kerr-based nonlinear functions featuring full thermal budget compatibility with existing Silicon photonics and front-end Si optoelectronics. Briefly, differently from previous and state-of-the-art works, our nonlinear nitride-based platform has been realized without resorting to commonly-used high-temperature annealing ( 1200°C) of the film and its silica upper-cladding used to break N-H bonds otherwise causing absorption in the C-band and destroying its nonlinear functionality. Furthermore, no complex and fabrication-intolerant Damascene process - as recently reported earlier this year - aimed at controlling cracks generated in thick tensile-strained Si3N4 films has been used as well. Instead, a tailored Si3N4 multiple-step film deposition in 200-mm LPCVD-based reactor and subsequent low-temperature (400°C) PECVD oxide encapsulation have been used to fabricate the nonlinear micro-resonant circuits aiming at generating optical frequency combs via optical parametric oscillators (OPOs), thus allowing the monolithic co-integration of such nonlinear functions on existing CMOS-compatible optoelectronics, for both active and passive components such as, for instance, silicon modulators and wavelength (de-)multiplexers. Experimental evidence based on wafer-level statistics show nitride-based 112-μm-radius ring resonators using such low-temperature crack-free nitride film exhibiting quality factors exceeding Q >3 x 105, thus paving the way to low-threshold power-efficient Kerr-based comb sources and dissipative temporal solitons in the C-band featuring full thermal processing compatibility with Si photonic integrated circuits (Si-PICs).

Design of a High Voltage Power Supply Providing a Force Field for a Fluid Experiment

NASA Astrophysics Data System (ADS)

Herty, Frank

2005-05-01

As part of the GeoFlow fluid experiment an ac high voltage power supply (HVPS) is used to establish high electrical fields on fluids based on silicon oil. The non- conductive fluid is encapsulated between two spherical electrodes. This experiment cell assembly acts essentially as a capacitive load.The GeoFlow HVPS is an integrated ac high voltage source capable to provide up to 10kVRMS on capacitive loads up to 100pF.This paper presents major design challenges and solutions regarding the high voltage transformer and its driver electronics. Particular high voltage problems like corona effects and dielectric losses are discussed and countermeasures are presented.

Solar power satellite system definition study. Part 3: Preferred concept system definition

NASA Technical Reports Server (NTRS)

1978-01-01

A concise but complete system description for the preferred concept of the Solar Power Satellite System is presented. Significant selection decisions included the following: (1) single crystal silicon solar cells; (2) glass encapsulated solar cell blankets; (3) concentration ratio 1; (4) graphite composite materials for primary structure; (5) electric propulsion for attitude control; (6) klystron RF amplifier tubes for the transmitter; (7) one kilometer diameter transmitter with a design trans mission link output power of 5,000 megawatts; (8) construction in low earth orbit with self-powered transfer of satellite modules to geosynchronous orbit; and (9) two-stage winged fully reusable rocket vehicle for transportation to low earth orbit.

Near-infrared fluorescence amplified organic nanoparticles with aggregation-induced emission characteristics for in vivo imaging

NASA Astrophysics Data System (ADS)

Geng, Junlong; Zhu, Zhenshu; Qin, Wei; Ma, Lin; Hu, Yong; Gurzadyan, Gagik G.; Tang, Ben Zhong; Liu, Bin

2013-12-01

Near-infrared (NIR) fluorescence signals are highly desirable to achieve high resolution in biological imaging. To obtain NIR emission with high brightness, fluorescent nanoparticles (NPs) are synthesized by co-encapsulation of 2,3-bis(4-(phenyl(4-(1,2,2-triphenylvinyl)phenylamino)phenyl)fumaronitrile (TPETPAFN), a luminogen with aggregation-induced emission (AIE) characteristics, and a NIR fluorogen of silicon 2,3-naphthalocyanine bis(trihexylsilyloxide) (NIR775) using 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] as the encapsulation matrix. The good spectral overlap between the emission of TPETPAFN and the absorption of NIR775 leads to efficient energy transfer, resulting in a 47-fold enhancement of the NIR775 emission intensity upon excitation of TPETPAFN at 510 nm as compared to that upon direct excitation of NIR775 at 760 nm. The obtained fluorescent NPs show sharp NIR emission with a band width of 20 nm, a large Stokes shift of 275 nm, good photostability and low cytotoxicity. In vivo imaging study reveals that the synthesized NPs are able to provide high fluorescence contrast in live animals. The Förster resonance energy transfer strategy overcomes the intrinsic limitation of broad emission spectra for AIE NPs, which opens new opportunities to synthesize organic NPs with high brightness and narrow emission for potential applications in multiplex sensing and imaging.Near-infrared (NIR) fluorescence signals are highly desirable to achieve high resolution in biological imaging. To obtain NIR emission with high brightness, fluorescent nanoparticles (NPs) are synthesized by co-encapsulation of 2,3-bis(4-(phenyl(4-(1,2,2-triphenylvinyl)phenylamino)phenyl)fumaronitrile (TPETPAFN), a luminogen with aggregation-induced emission (AIE) characteristics, and a NIR fluorogen of silicon 2,3-naphthalocyanine bis(trihexylsilyloxide) (NIR775) using 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] as the encapsulation matrix. The good spectral overlap between the emission of TPETPAFN and the absorption of NIR775 leads to efficient energy transfer, resulting in a 47-fold enhancement of the NIR775 emission intensity upon excitation of TPETPAFN at 510 nm as compared to that upon direct excitation of NIR775 at 760 nm. The obtained fluorescent NPs show sharp NIR emission with a band width of 20 nm, a large Stokes shift of 275 nm, good photostability and low cytotoxicity. In vivo imaging study reveals that the synthesized NPs are able to provide high fluorescence contrast in live animals. The Förster resonance energy transfer strategy overcomes the intrinsic limitation of broad emission spectra for AIE NPs, which opens new opportunities to synthesize organic NPs with high brightness and narrow emission for potential applications in multiplex sensing and imaging. Electronic supplementary information (ESI) available: Characterization of AIE properties of TPETPAFN, UV-vis spectra of NPs, PL spectra comparison upon excitation at the donor and receptor absorbance maxima, ex vivo fluorescence imaging of mice organs. See DOI: 10.1039/c3nr04243j

Thin-film amorphous silicon alloy research partnership. Phase 2, Annual technical progress report, 2 February 1996--1 February 1997

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

Guha, S

This is Phase II of a 3-phase, 3-year program. It is intended to expand, enhance, and accelerate knowledge and capabilities for developing high-performance, two-terminal multijunction amorphous Si alloy modules. We discuss investigations on back reflectors to improve cell performance and investigate uniformity in performance over a 1-sq.-ft. area. We present results on component cell performance, both in the initial and in the light-degraded states, deposited over a 1-sq.-ft. area. The uniformity in deposited is investigated by studying the performance of subcells deposited over the entire area. We also present results on the performance of triple- junction cells and modules. Themore » modules use grid-lines and encapsulants compatible with our production technology. We discuss the novel laser-processing technique that has bee developed at United Solar to improve energy-conversion efficiency and reduce manufacturing costs. We discuss in detail the optimization of the processing steps, and the performance of a laser-processed, triple- junction device of 12.6 cm{sup 2} area is presented. We also present experimental results on investigations of module reliability.« less

Toward Environmentally Robust Organic Electronics: Approaches and Applications.

PubMed

Lee, Eun Kwang; Lee, Moo Yeol; Park, Cheol Hee; Lee, Hae Rang; Oh, Joon Hak

2017-11-01

Recent interest in flexible electronics has led to a paradigm shift in consumer electronics, and the emergent development of stretchable and wearable electronics is opening a new spectrum of ubiquitous applications for electronics. Organic electronic materials, such as π-conjugated small molecules and polymers, are highly suitable for use in low-cost wearable electronic devices, and their charge-carrier mobilities have now exceeded that of amorphous silicon. However, their commercialization is minimal, mainly because of weaknesses in terms of operational stability, long-term stability under ambient conditions, and chemical stability related to fabrication processes. Recently, however, many attempts have been made to overcome such instabilities of organic electronic materials. Here, an overview is provided of the strategies developed for environmentally robust organic electronics to overcome the detrimental effects of various critical factors such as oxygen, water, chemicals, heat, and light. Additionally, molecular design approaches to π-conjugated small molecules and polymers that are highly stable under ambient and harsh conditions are explored; such materials will circumvent the need for encapsulation and provide a greater degree of freedom using simple solution-based device-fabrication techniques. Applications that are made possible through these strategies are highlighted. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dual-coating of liposomes as encapsulating matrix of antimicrobial peptides: Development and characterization

NASA Astrophysics Data System (ADS)

Gomaa, Ahmed I.; Martinent, Cynthia; Hammami, Riadh; Fliss, Ismail; Subirade, Muriel

2017-11-01

Abstract Antimicrobial peptides have been proposed as a potential biopreservatives in pharmaceutical research and agribusiness. However, many limitations hinder their utilization, such as their vulnerability to proteolytic digestion and their potential interaction with other food ingredients in complex food systems. One approach to overcome such problems is developing formulations entrapping and thereby protecting the antimicrobial peptides. Liposome encapsulation is a strategy that could be implemented to combine protection of the antimicrobial activity of the peptides from proteolytic enzymes and the controlled release of the encapsulated active ingredients. The objective of this study was to develop dual-coated food grade liposome formulations for oral administration of bacteriocins. The formulations were developed from anionic and cationic phospholipids as models of negatively and positively charged liposomes, respectively. Liposomes were prepared by the hydration of lipid films. Subsequently, the liposomes were coated with two layers comprising a biopolymer network (pectin) and whey proteins (WPI) in order to further improve their stability and enable the gradual release of the developed liposomes. Liposomes were characterized for their size, charge, molecular structure, morphology, encapsulation efficiency and release. The results of FTIR, zeta potential, size distribution and transmission electron microscopy confirmed that the liposomes were efficiently coated. Ionic interactions were involved in the stabilization of the positively charged liposome formulations. Negatively charge liposome formulations were stabilized through weak interactions. The release study proved the efficiency of dual coating on the protection of liposomes against gastrointestinal digestion. This work is the first to study the encapsulation of antimicrobial peptides in dual-coated liposomes. Furthermore, the work successfully encapsulated MccJ25 in both negative and positive liposome models.

The Advanced Glaucoma Intervention Study (AGIS): 5. Encapsulated bleb after initial trabeculectomy.

PubMed

Schwartz, A L; Van Veldhuisen, P C; Gaasterland, D E; Ederer, F; Sullivan, E K; Cyrlin, M N

1999-01-01

To compare the incidence of encapsulated bleb after trabeculectomy in eyes with and without previous argon laser trabeculoplasty and to assess other risk factors for encapsulated bleb development. After medical treatment failure, eyes enrolled in the Advanced Glaucoma Intervention Study (AGIS) were randomly assigned to sequences of interventions starting with either argon laser trabeculoplasty or trabeculectomy. In the present study we compared the clinical course for 1 year after trabeculectomy in 119 eyes with failed argon laser trabeculoplasty with that of 379 eyes without previous argon laser trabeculoplasty. Data on bleb encapsulation were collected at the time that the encapsulation was diagnosed, and 3 and 6 months later. Of multiple factors examined in the AGIS data for the risk of developing encapsulated bleb, only male gender and high school graduation without further formal education were statistically significant. Encapsulation occurred in 18.5% of eyes with previous argon laser trabeculoplasty failure and 14.5% of eyes without previous argon laser trabeculoplasty (unadjusted relative risk, 1.27; 95% confidence limits = 0.81, 2.00; P = .23). After adjusting for age, gender, educational achievement, prescribed systemic beta-blockers, diabetes, visual field score, and years since glaucoma diagnosis, this difference remains statistically not significant. Four weeks after trabeculectomy, mean intraocular pressure was 7.5 mm Hg higher in eyes with (22.5 mm Hg) than without (15.0 mm Hg) encapsulated bleb; at 1 year after trabeculectomy and the resumption of medical therapy when needed, this excess was reduced to 1.4 mm Hg. This study, as did two previous studies, found male gender to be a risk factor for bleb encapsulation. Four studies, including the present study, have reported a higher rate of encapsulation in eyes with previous argon laser trabeculoplasty; in two of the studies, one of which was the present study, the rate was not statistically significantly higher; in the other two studies the rate was significantly higher. The 4-week postoperative mean intraocular pressure was higher in eyes with than without encapsulated bleb; with the resumption of medical treatment the two means converged after 1 year.

A Comparative Cytotoxic Evaluation of Disulfiram Encapsulated PLGA Nanoparticles on MCF-7 Cells

PubMed Central

Fasehee, Hamidreza; Ghavamzadeh, Ardeshir; Alimoghaddam, Kamran; Ghaffari, Seyed-Hamidollah; Faghihi, Shahab

2017-01-01

Background: Disulfiram is oral aldehyde dehydrogenase (ALDH) inhibitor that has been used in the treatment of alcoholism. Recent studies show that this drug has anticancer properties; however, its rapid degradation has limited its clinical application. Encapsulation of disulfiram polymeric nanoparticles (NPs) may improve its anticancer activities and protect rapid degradation of the drug. Materials and Methods: A poly (lactide-co-Glycolide) (PLGA) was developed for encapsulation of disulfiram and its delivery into breast cancer cells. Disulfiram encapsulated PLGA NPs were prepared by nanoprecipitation method and were characterized by Scanning Electron Microscopy (SEM). The loading and encapsulation efficiency of NPs were determined using UV-Visible spectroscopy. Cell cytotoxicity of free and encapsulated form of disulfiram is also determined using MTT assay. Results: Disulfiram encapsulated PLGA NPs had uniform size with 165 nm. Drug loading and entrapment efficiency were 5.35 ±0.03% and 58.85±1.01%. The results of MTT assay showed that disulfiram encapsulated PLGA NPs were more potent in induction of apoptosis compare to free disulfiram. Conclusion: Based on the results obtained in the present study it can be concluded that encapsulation of disulfiram with PLGA can protect its degradation in improve its cytotoxicity on breast cancer cells. PMID:28875004

Comparison of polypropylene and silicone Ahmed® glaucoma valves in the treatment of neovascular glaucoma: A 2-year follow-up.

PubMed

Lubiński, Wojciech; Krzystolik, Karol; Gosławski, Wojciech; Kuprjanowicz, Leszek; Mularczyk, Maciej

2018-01-01

Inflammation associated with biomaterials of Ahmed® glaucoma drainage devices may cause the formation of a capsule around the device and can thus have a significant influence on the level of intraocular pressure reduction. The objective of this study was to compare the clinical outcomes after the implantation of a polypropylene or silicone Ahmed® glaucoma valve in patients with neovascular glaucoma. In the study, 27 eyes with neovascular glaucoma (group 1) received silicon Ahmed® valves and 23 eyes (group 2) received polypropylene valves. The best corrected distance visual acuity (BCDVA), intraocular pressure (IOP) and number of anti-glaucomatous drugs were recorded preoperatively and during a follow-up period of 24 months after surgery. Success was defined by the following criteria: 1) intraocular pressure in the rage of 6-21 mm Hg; 2) IOP reduction of at least 30% relative to preoperative values. All complications were registered. One month postoperatively, the mean BCDVA increased significantly in both groups compared to preoperative values (p < 0.001). These values did not change during the 24 months of follow-up examinations. The probability of success defined by criterion 1 at 24 months of observation was 66.7% for silicone and 27.3% for propylene valves group (p < 0.007). According to criterion 2, the difference in success between the groups was not statistically significant. The total number of complications that occurred in both groups during the 24 months of follow-up examinations was similar, except for a higher occurrence of Tenon's cyst formation in the group with a polypropylene valve (18% vs 35%; p < 0.04). In patients with neovascular glaucoma, the implantation of a silicone valve is associated with a significantly higher probability of long-term reduction of IOP below 21 mm Hg and with a lower risk of valve encapsulation in comparison to polypropylene valves. The obtained results suggest that silicone Ahmed® valves are more effective in the treatment of patients with neovascular glaucoma.

Design, analysis and test verification of advanced encapsulation systems

NASA Technical Reports Server (NTRS)

Garcia, A.; Minning, C.

1982-01-01

Analytical models were developed to perform optical, thermal, electrical and structural analyses on candidate encapsulation systems. Qualification testing, specimens of various types, and a finalized optimum design are projected.

Methodology for Evaluating Encapsulated Beneficial Uses of Coal Combustion Residuals

EPA Pesticide Factsheets

The primary purpose of this document is to present an evaluation methodology developed by the EPA for making determinations about environmental releases from encapsulated products containing coal combustion residuals.

Comparative studies on osmosis based encapsulation of sodium diclofenac in porcine and outdated human erythrocyte ghosts.

PubMed

Bukara, Katarina; Drvenica, Ivana; Ilić, Vesna; Stančić, Ana; Mišić, Danijela; Vasić, Borislav; Gajić, Radoš; Vučetić, Dušan; Kiekens, Filip; Bugarski, Branko

2016-12-20

The objective of our study was to develop controlled drug delivery system based on erythrocyte ghosts for amphiphilic compound sodium diclofenac considering the differences between erythrocytes derived from two readily available materials - porcine slaughterhouse and outdated transfusion human blood. Starting erythrocytes, empty erythrocyte ghosts and diclofenac loaded ghosts were compared in terms of the encapsulation efficiency, drug releasing profiles, size distribution, surface charge, conductivity, surface roughness and morphology. The encapsulation of sodium diclofenac was performed by an osmosis based process - gradual hemolysis. During this process sodium diclofenac exerted mild and delayed antihemolytic effect and increased potassium efflux in porcine but not in outdated human erythrocytes. FTIR spectra revealed lack of any membrane lipid disorder and chemical reaction with sodium diclofenac in encapsulated ghosts. Outdated human erythrocyte ghosts with detected nanoscale damages and reduced ability to shrink had encapsulation efficiency of only 8%. On the other hand, porcine erythrocyte ghosts had encapsulation efficiency of 37% and relatively slow drug release rate. More preserved structure and functional properties of porcine erythrocytes related to their superior encapsulation and release performances, define them as more appropriate for the usage in sodium diclofenac encapsulation process. Copyright © 2016 Elsevier B.V. All rights reserved.

Status of FEP encapsulated solar cell modules used in terrestrial applications

NASA Technical Reports Server (NTRS)

Ratajczak, A. F.; Forestieri, A. F.

1974-01-01

The Lewis Research Center has been engaged in transferring the FEP encapsulated solar cell technology developed for the space program to terrestrial applications. FEP encapsulated solar cell modules and arrays were designed and built expressly for terrestrial applications. Solar cell power systems were installed at three different land sites, while individual modules are undergoing marine environment tests. Four additional power systems are being completed for installation during the summer of 1974. These tests have revealed some minor problems which have been corrected. The results confirm the inherent utility of FEP encapsulated terrestrial solar cell systems.

Essential oils: from extraction to encapsulation.

PubMed

El Asbahani, A; Miladi, K; Badri, W; Sala, M; Aït Addi, E H; Casabianca, H; El Mousadik, A; Hartmann, D; Jilale, A; Renaud, F N R; Elaissari, A

2015-04-10

Essential oils are natural products which have many interesting applications. Extraction of essential oils from plants is performed by classical and innovative methods. Numerous encapsulation processes have been developed and reported in the literature in order to encapsulate biomolecules, active molecules, nanocrystals, oils and also essential oils for various applications such as in vitro diagnosis, therapy, cosmetic, textile, food etc. Essential oils encapsulation led to numerous new formulations with new applications. This insures the protection of the fragile oil and controlled release. The most commonly prepared carriers are polymer particles, liposomes and solid lipid nanoparticles. Copyright © 2015 Elsevier B.V. All rights reserved.

Controlled graphene encapsulation: a nanoscale shield for characterising single bacterial cells in liquid.

PubMed

Li, Jiayao; Zheng, Changxi; Liu, Boyin; Chou, Tsengming; Kim, Yeonuk; Qiu, Shi; Li, Jian; Yan, Wenyi; Fu, Jing

2018-06-11

High-resolution single-cell imaging in their native or near-native state has received considerable interest for decades. In this research, we present an innovative approach that can be employed to study both morphological and nano-mechanical properties of hydrated single bacterial cells. The proposed strategy is to encapsulate wet cells with monolayer graphene with a newly developed water membrane approach, followed by imaging with both electron microscopy (EM) and atomic force microscopy (AFM). A computational framework was developed to provide additional insights, with the detailed nanoindentation process on graphene modeled based on finite element method. The model was first validated by calibration with polymer materials of known properties, and the contribution of graphene was then studied and corrected to determine the actual moduli of the encapsulated hydrated sample. Aapplication of the proposed approach was performed on hydrated bacterial cells (Klebsiella pneumoniae) to correlate the structural and mechanical information. EM and EDS (energy-dispersive X-ray spectroscopy) imaging confirmed that the cells in their near-native stage can be studied inside the miniatured environment enabled with graphene encapsulation. The actual moduli of the encapsulated hydrated cells were determined based on the developed computational model in parallel, with results comparable with those acquired with Wet-AFM. It is expected that the successful establishment of controlled graphene encapsulation offers a new route for probing liquid/live cells with scanning probe microscopy, as well as correlative imaging of hydrated samples for both biological and material sciences. © 2018 IOP Publishing Ltd.

Atmospheric Electron-induced X-Ray Spectrometer (AEXS) Instrument Development

NASA Technical Reports Server (NTRS)

Wilcox, J. Z.; Urgiles, E.; Toda, R.; George, T.; Crisp, J.

2005-01-01

Instrument Development: The membrane properties were investigated in detail due to its critical role. A series of experiments determined that our designed membranes have high electron transmission, yet are capable of isolating high vacuum, are able to withstand differential pressure in excess of one atmosphere, survive vibrational shocks of a magnitude to be expected during a planetary mission. Our initial work has been with a 10 keV source and a 200 nm thick Silicon Nitride (SiN) encapsulation membrane micro-fabricated within a Si support frame (1.5 mm x 1.5 mm window openings. Fig 2 compares the spectra taken with the 10 keV source with spectra taken within SEM. Introduction: This paper describes the progress in the development of the AEXS instrument in our laboratory at JPL. The AEXS is a novel miniature instrument[1-3] based on the excitation of characteristic X-Ray Fluorescence (XRF) and luminescence spectra using a focused electron beam, for non-destructive evaluation of surfaces of samples in planetary ambient atmosphere. In situ operation is obtained through the use of a thin electron transmissive membrane to isolate the vacuum within the AEXS electron source from the outside ambient atmosphere. The impinging electrons excite XRF spectra from the irradiated spots on samples in external atmosphere with high-to-medium (sub-mm to cm-scale) spatial resolution at Mars atmospheric pressure. The XRF spectra are analyzed using an energy-dispersive detector to determine surface elemental composition, or in the case of electron-induced luminescence to identify unusual formations on surface that cathodo-luminescence (CL). The AEXS system (Fig 1) consists of a high-energy (>10keV) electron gun encapsulated by the isolation membrane, an EDX detection and analyzer system to determine the elemental abundance, an optional CL detection system, and a high voltage power supply. The approach to demonstrating a proof of concept of the AEXS has been through 1) demonstrating the viability of micro-fabricated membranes, 2) assembling AEXS setups with increasingly integrated functional components, and 3) simulating the AEXS observational capabilities. This paper will focus on description of the development of the instrument.

DNA hydrogel microspheres and their potential applications for protein delivery and live cell monitoring

PubMed Central

Kim, Taeyoung; Park, Seongmin; Baek, Solhee; Lee, Jong Bum; Park, Nokyoung

2016-01-01

Microfluidic devices have been extensively developed as methods for microscale materials fabrication. It has also been adopted for polymeric microsphere fabrication and in situ drug encapsulation. Here, we employed multi-inlet microfluidic channels for DNA hydrogel microsphere formation and in situ protein encapsulation. The release of encapsulated proteins from DNA hydrogels showed different profiles accordingly with the size of microspheres. PMID:27279936

Development of Encapsulated Dye for Surface Impact Damage Indicator System.

DTIC Science & Technology

1987-09-01

GROUP SUB-GROUP Composites Ultrasonics Dye Impact Microcapsules 11 04 NDE polyurethane 11 1 0Encapsulation Paint 19. ABSTRACT (Continue on reverse if...encapsulation, microencapsule incorporation into the USAF polyurethane paint, dnd initial correlation study of impact damage to impact coating indication. It is...project were to: 1. Refine the microcapsule formulation to be compatible with MIL-C-83286 paint. 2. Fabricate composite panels from isotropic graphite

Development of pre-implantation porcine blastocysts cultured within alginate hydrogel systems either supplemented with secreted phosphoprotein 1 or conjugated with Arg-Gly-Asp Peptide.

PubMed

Laughlin, Taylor D; Miles, Jeremy R; Wright-Johnson, Elane C; Rempel, Lea A; Lents, Clay A; Pannier, Angela K

2017-11-01

Although deficiencies in porcine blastocyst elongation play a significant role in early embryonic mortality and establishment of within-litter developmental variation, the exact mechanisms of elongation are poorly understood. Secreted phosphoprotein 1 (SPP1) is increased within the uterine milieu during early porcine pregnancy and contains an Arg-Gly-Asp (RGD) peptide sequence that binds to cell surface integrins on the uterine endometrium and trophectoderm, promoting cell adhesion and migration. The aim of the present study was to evaluate the development of preimplantation porcine blastocysts encapsulated and cultured within alginate hydrogels either supplemented with SPP1 or conjugated with RGD. Blastocysts encapsulated within alginate hydrogels supplemented with SPP1 or conjugated with RGD had increased survival compared with non-encapsulated control blastocysts. In addition, the percentage of blastocysts encapsulated within RGD hydrogels that underwent morphological changes was greater than that of blastocysts encapsulated within standard alginate hydrogels or SPP1-supplemented hydrogels. Finally, only blastocysts encapsulated within RGD hydrogels had both increased expression of steroidogenic and immune responsiveness transcripts and increased 17β-oestradiol production, consistent with blastocysts undergoing elongation in vivo. These results illustrate the importance of the integrin-binding RGD peptide sequence for stimulating the initiation of blastocyst elongation.

Hypolipidaemic and anti-oxidative potential of encapsulated herb (Terminalia arjuna) added vanilla chocolate milk in high cholesterol fed rats.

PubMed

Sawale, Pravin Digambar; Pothuraju, Ramesh; Abdul Hussain, Shaik; Kumar, Anuj; Kapila, Suman; Patil, Girdhari Ramdas

2016-03-15

Atherosclerosis is associated with coronary artery disease and occurs in developing as well as developed countries. In the present investigation, hypolipidaemic and anti-oxidative properties of encapsulated herb (Terminalia arjuna, 1.8%) added vanilla chocolate dairy drink was evaluated in high cholesterol fed Wistar rats for 60 days. At the end of the experimental period, a significant decrease in the body weight gain by rats receiving the encapsulated herb extract was noted as compared to high cholesterol fed rats. Administration of microencapsulated herb showed a statistically significant decrease in organ weights (epididymal fat and liver). Moreover, a significant decrease in serum lipids such as triglycerides, total cholesterol, low-density lipoprotein cholesterol, very-low-density lipoprotein cholesterol and atherogenic index was observed with encapsulated Terminalia arjuna extract in high cholesterol fed group. Increases in reduced glutathione and decreases in TBARS levels were also reported in both liver and red blood cell lysates with encapsulated herb supplementation. The results demonstrated that the bioactive components (phytosterols, flavanoids, saponins and tannins etc.) which are present in the encapsulated T. arjuna not only withstand the processing conditions but also are effectively released in the intestine and show their effects, such as hypolipidaemic and antioxidant activities, for better treating cardiovascular disease. © 2015 Society of Chemical Industry.

Development of DBD plasma actuators: The double encapsulated electrode

NASA Astrophysics Data System (ADS)

Erfani, Rasool; Zare-Behtash, Hossein; Hale, Craig; Kontis, Konstantinos

2015-04-01

Plasma actuators are electrical devices that generate a wall bounded jet without the use of any moving parts. For aerodynamic applications they can be used as flow control devices to delay separation and augment lift on a wing. The standard plasma actuator consists of a single encapsulated (ground) electrode. The aim of this project is to investigate the effect of varying the number and distribution of encapsulated electrodes in the dielectric layer. Utilising a transformer cascade, a variety of input voltages are studied for their effect. In the quiescent environment of a Faraday cage the velocity flow field is recorded using particle image velocimetry. Through understanding of the mechanisms involved in producing the wall jet and the importance of the encapsulated electrode a novel actuator design is proposed. The actuator design distributes the encapsulated electrode throughout the dielectric layer. The experiments have shown that actuators with a shallow initial encapsulated electrode induce velocities greater than the baseline case at the same voltage. Actuators with a deep initial encapsulated electrode are able to induce the highest velocities as they can operate at higher voltages without breakdown of the dielectric.

Low Hysteresis Carbon Nanotube Transistors Constructed via a General Dry-Laminating Encapsulation Method on Diverse Surfaces.

PubMed

Yang, Yi; Wang, Zhongwu; Xu, Zeyang; Wu, Kunjie; Yu, Xiaoqin; Chen, Xiaosong; Meng, Yancheng; Li, Hongwei; Qiu, Song; Jin, Hehua; Li, Liqiang; Li, Qingwen

2017-04-26

Electrical hysteresis in carbon nanotube thin-film transistor (CNTTFT) due to surface adsorption of H 2 O/O 2 is a severe obstacle for practical applications. The conventional encapsulation methods based on vacuum-deposited inorganic materials or wet-coated organic materials have some limitations. In this work, we develop a general and highly efficient dry-laminating encapsulation method to reduce the hysteresis of CNTTFTs, which may simultaneously realize the construction and encapsulation of CNTTFT. Furthermore, by virtue of dry procedure and wide compatibility of PMMA, this method is suitable for the construction of CNTTFT on diverse surface including both inorganic and organic dielectric materials. Significantly, the dry-encapsulated CNTTFT exhibits very low or even negligible hysteresis with good repeatability and air stability, which is greatly superior to the nonencapsulated and wet-encapsulated CNTTFT with spin-coated PMMA. The dry-laminating encapsulation strategy, a kind of technological innovation, resolves a significant problem of CNTTFT and therefore will be promising in facile transferring and packaging the CNT films for high-performance optoelectronic devices.

The status of lightweight photovoltaic space array technology based on amorphous silicon solar cells

NASA Astrophysics Data System (ADS)

Hanak, J. J.; Kaschmitter, J. L.

1991-05-01

An ultralight, flexible photovoltaic (PV) array of amorphous silicon (a-Si) has been identified as a potential low-cost power source for small satellites. We have conducted a survey of the status of the a-Si PV array technology with respect to present and future performance, availability, cost and risks. For existing, experimental array 'blankets' made of commercial cell material, utilizing metal foil substrates, the BOL performance at AM0 and 35 C includes total power up to 200 W, power per area of 64 W/sq m and power per weight of 258 W/kg. Doubling of power per weight occurs when polyimide substrates are used. Estimated EOL power output after 10 years in a nominal low-earth orbit would be 80 percent of BOL, the degradation being due to largely light-induced effects (minus 10 to minus 15 percent) and in part (minus 5 percent) to space radiation. Predictions for the year 1995 for flexible PV arrays, made on the basis of published results for rigid a-Si modules, indicate EOL power output per area and per weight of 105 W/sq m and 400 W/kg, respectively, while predictions for the late 1990s based on existing US national PV program goals indicate EOL values of 157 W/sq m and 600 W/kg. cost estimates by vendors for 200 W ultralight arrays in volume of over 1000 units range from $100/watt to $125/watt. Identified risks include the lack of flexible, space compatible encapsulant, the lack of space qualification effort, recent partial or full acquisitions of US manufacturers of a-Si cells by foreign firms, and the absence of a national commitment for a long-range development program toward developing of this important power source for space. One new US developer has emerged as a future potential supplier of a-Si PV devices on thin, polyimide substrates.

Starch Applications for Delivery Systems

NASA Astrophysics Data System (ADS)

Li, Jason

2013-03-01

Starch is one of the most abundant and economical renewable biopolymers in nature. Starch molecules are high molecular weight polymers of D-glucose linked by α-(1,4) and α-(1,6) glycosidic bonds, forming linear (amylose) and branched (amylopectin) structures. Octenyl succinic anhydride modified starches (OSA-starch) are designed by carefully choosing a proper starch source, path and degree of modification. This enables emulsion and micro-encapsulation delivery systems for oil based flavors, micronutrients, fragrance, and pharmaceutical actives. A large percentage of flavors are encapsulated by spray drying in today's industry due to its high throughput. However, spray drying encapsulation faces constant challenges with retention of volatile compounds, oxidation of sensitive compound, and manufacturing yield. Specialty OSA-starches were developed suitable for the complex dynamics in spray drying and to provide high encapsulation efficiency and high microcapsule quality. The OSA starch surface activity, low viscosity and film forming capability contribute to high volatile retention and low active oxidation. OSA starches exhibit superior performance, especially in high solids and high oil load encapsulations compared with other hydrocolloids. The submission is based on research and development of Ingredion

The Array Automated Assembly Task for the Low Cost Solar Array Project, Phase 2

NASA Technical Reports Server (NTRS)

Campbell, R. B. (Editor); Farukhi, S. (Editor)

1978-01-01

During the program a process sequence was proposed and tested for the fabrication of dendritic welb silicon into solar modules. This sequence was analyzed as to yield and cost and these data suggest that the price goals of 1986 are attainable. Specifically, it was shown that a low cost POCL3 is a suitable replacement for the semiconductor grade, and that a suitable CVD oxide can be deposited from a silane/air mixture using a Silox reactor. A dip coating method was developed for depositing an antireflection coating from a metalorganic precursor. Application of photoresist to define contact grids was made cost effective through use of a dip coating technique. Electroplating of both Ag and Cu was shown feasible and cost effective for producing the conductive metal grids on the solar cells. Laser scribing was used to separate the cells from the dendrites without degradation. Ultrasonic welding methods were shown to be feasible for interconnecting the cells. A study of suitable low cost materials for encapsulation suggest that soda lime glass and phenolic filled board are preferred.

High resolution thickness measurements of ultrathin Si:P monolayers using weak localization

NASA Astrophysics Data System (ADS)

Hagmann, Joseph A.; Wang, Xiqiao; Namboodiri, Pradeep; Wyrick, Jonathan; Murray, Roy; Stewart, M. D.; Silver, Richard M.; Richter, Curt A.

2018-01-01

The key building blocks for the fabrication of devices based on the deterministic placement of dopants in silicon using scanning tunneling microscopy (STM) hydrogen lithography are the formation of well-defined dopant delta-layers and the overgrowth of high quality crystalline Si. To develop these capabilities, it is of critical importance to quantify dopant movement in the sub-nanometer regime. To this end, we investigate Si:P delta-layer samples produced by fully exposing a Si surface to PH3 prior to Si encapsulation with dramatically different levels of dopant confinement. We examine the effect of delta layer confinement on the weak localization signal in parallel and perpendicular magnetic fields and extract the delta-layer thickness from fits to the Hikami-Larkin-Nagaoka equation. We find good agreement with secondary ion mass spectroscopy measurements and demonstrate the applicability of this method in the sub-nanometer thickness regime. Our analysis serves as detailed instruction for the determination of the conducting layer thickness of a Si:P delta-layer by means of a high-throughput, nondestructive electrical transport measurement.

Producing thin film photovoltaic modules with high integrity interconnects and dual layer contacts

DOEpatents

Jansen, Kai W.; Maley, Nagi

2000-01-01

High performance photovoltaic modules are produced with improved interconnects by a special process. Advantageously, the photovoltaic modules have a dual layer back (rear) contact and a front contact with at least one layer. The front contact and the inner layer of the back contact can comprise a transparent conductive oxide. The outer layer of the back contact can comprise a metal or metal oxide. The front contact can also have a dielectric layer. In one form, the dual layer back contact comprises a zinc oxide inner layer and an aluminum outer layer and the front contact comprises a tin oxide inner layer and a silicon dioxide dielectric outer layer. One or more amorphous silicon-containing thin film semiconductors can be deposited between the front and back contacts. The contacts can be positioned between a substrate and an optional superstrate. During production, the transparent conductive oxide layer of the front contact is scribed by a laser, then the amorphous silicon-containing semiconductors and inner layer of the dual layer back contact are simultaneously scribed and trenched (drilled) by the laser and the trench is subsequently filled with the same metal as the outer layer of the dual layer back contact to provide a superb mechanical and electrical interconnect between the front contact and the outer layer of the dual layer back contact. The outer layer of the dual layer back contact can then be scribed by the laser. For enhanced environmental protection, the photovoltaic modules can be encapsulated.

Producing thin film photovoltaic modules with high integrity interconnects and dual layer contacts

DOEpatents

Jansen, Kai W.; Maley, Nagi

2001-01-01

High performance photovoltaic modules are produced with improved interconnects by a special process. Advantageously, the photovoltaic modules have a dual layer back (rear) contact and a front contact with at least one layer. The front contact and the inner layer of the back contact can comprise a transparent conductive oxide. The outer layer of the back contact can comprise a metal or metal oxide. The front contact can also have a dielectric layer. In one form, the dual layer back contact comprises a zinc oxide inner layer and an aluminum outer layer and the front contact comprises a tin oxide inner layer and a silicon dioxide dielectric outer layer. One or more amorphous silicon-containing thin film semiconductors can be deposited between the front and back contacts. The contacts can be positioned between a substrate and an optional superstrate. During production, the transparent conductive oxide layer of the front contact is scribed by a laser, then the amorphous silicon-containing semiconductors and inner layer of the dual layer back contact are simultaneously scribed and trenched (drilled) by the laser and the trench is subsequently filled with the same metal as the outer layer of the dual layer back contact to provide a superb mechanical and electrical interconnect between the front contact and the outer layer of the dual layer back contact. The outer layer of the dual layer back contact can then be scribed by the laser. For enhanced environmental protection, the photovoltaic modules can be encapsulated.

Steel Bar corrosion monitoring based on encapsulated piezoelectric sensors

NASA Astrophysics Data System (ADS)

Xu, Ying; Tang, Tianyou

2018-05-01

The durability of reinforced concrete has a great impact on the structural bearing capacity, while the corrosion of steel bars is the main reason for the degradation of structural durability. In this paper, a new type of encapsulated cement based piezoelectric sensor is developed and its working performance is verified. The consistency of the finite element simulation and the experimental results shows the feasibility of monitoring the corrosion of steel bars using encapsulated piezoelectric sensors. The research results show that the corrosion conditions of the steel bars can be determined by the relative amplitude of the measured signal through the encapsulated piezoelectric sensor.

Development of alginate microspheres containing thyme essential oil using ionic gelation.

PubMed

Benavides, Sergio; Cortés, Pablo; Parada, Javier; Franco, Wendy

2016-08-01

Essential oils are a good antimicrobial and antioxidant agent alternative in human or animal feed. However, their direct use has several disadvantages such as volatilization or oxidation. The development of essential oil microspheres may help to avoid these problems. The objective of the present research was to microencapsulate thyme essential oil by generating emulsions with different dispersion degrees. The emulsions were encapsulated in calcium-alginate microspheres by ionic gelation. The microspheres were evaluated regarding size, shape, encapsulation efficiency, loading capacity and antimicrobial properties. The results indicate that encapsulation efficiency and loading capacity are dependent on concentration and degree of dispersion. The best encapsulation conditions were obtained at 2% v/v of thyme essential oil with a high dispersion degree (18,000rpm/5min), which was achieved with an efficiency of 85%. Finally, the microspheres obtained showed significant antimicrobial effect, especially in gram-positive bacteria. Copyright © 2016 Elsevier Ltd. All rights reserved.

Transferrin-Conjugated SNALPs Encapsulating 2′-O-Methylated miR-34a for the Treatment of Multiple Myeloma

PubMed Central

Scognamiglio, Immacolata; Di Martino, Maria Teresa; Campani, Virginia; Virgilio, Antonella; Galeone, Aldo; Gullà, Annamaria; Gallo Cantafio, Maria Eugenia; Tagliaferri, Pierosandro; Tassone, Pierfrancesco; Caraglia, Michele

2014-01-01

Stable nucleic acid lipid vesicles (SNALPs) encapsulating miR-34a to treat multiple myeloma (MM) were developed. Wild type or completely 2′-O-methylated (OMet) MiR-34a was used in this study. Moreover, SNALPs were conjugated with transferrin (Tf) in order to target MM cells overexpressing transferrin receptors (TfRs). The type of miR-34a chemical backbone did not significantly affect the characteristics of SNALPs in terms of mean size, polydispersity index, and zeta potential, while the encapsulation of an OMet miR-34a resulted in a significant increase of miRNA encapsulation into the SNALPs. On the other hand, the chemical conjugation of SNALPs with Tf resulted in a significant decrease of the zeta potential, while size characteristics and miR-34a encapsulation into SNALPs were not significantly affected. In an experimental model of MM, all the animals treated with SNALPs encapsulating miR-34a showed a significant inhibition of the tumor growth. However, the use of SNALPs conjugated with Tf and encapsulating OMet miR-34a resulted in the highest increase of mice survival. These results may represent the proof of concept for the use of SNALPs encapsulating miR-34a for the treatment of MM. PMID:24683542

Encapsulation of lycopene in Chlorella pyrenoidosa: Loading properties and stability improvement.

PubMed

Pu, Chuanfen; Tang, Wenting

2017-11-15

Aiming to improve the stability of lycopene and incorporate it into a complex nutraceutical, exogenous lycopene-loaded Chlorella pyrenoidosa cells (CPCs) were developed. The complex had an encapsulation yield of 13.06±0.89% and an encapsulation efficiency of 96.31±3.10%. Fluorescence analyses indicated that lycopene was encapsulated in the CPCs. X-ray diffraction, thermogravimetric and differential scanning calorimetric analyses were conducted and compared to those of the non-loaded CPCs, lycopene and their physical mixture. These studies demonstrated that lycopene was amorphous in the complex. The degradation kinetics indicated that encapsulation increased the stability of lycopene. The antioxidant activity of lycopene loaded CPCs against DPPH free radicals was higher than that of the unencapsulated lycopene after storage at 25°C for 25d. This study proved the feasibility of encapsulation of lycopene in the CPCs and combined the activities of both materials, which could be employed in the production of novel nutraceuticals to reduce oxidative stress. Copyright © 2017 Elsevier Ltd. All rights reserved.

Fabrication and modeling of stretchable conductors for traumatic brain injury research

NASA Astrophysics Data System (ADS)

Cao, Wenzhe

Stretchable electronics are an emergent class of electronics that can retain their electric functionality under large mechanical deformation, such as stretching, bending and compression. Like traditional electric circuits, stretchable electronics rely on electrical conductors, but in this specific instance the conductors must also be stretchable. This thesis research had three goals: (1) fabricate elastically stretchable conductors that retain their electrical conductance when stretched by tens of percent of strain; (2) understand the underlying stretching mechanism of gold conductors on polydimethylsiloxane (PDMS) substrates; (3) produce a special device---a stretchable microelectrode array, which contains a matrix of stretchable conductors that enables a new approach to studying traumatic brain injury. We first developed and optimized the micro-fabrication process to make elastically stretchable thin gold film conductors on PDMS substrates. The conductors can retain electrical conduction while being stretched reversibly to 140% uniaxially and 16% radially. We further developed a fabrication process to encapsulate the conductors with either a commercially available photopatternable silicone (PPS) or with PDMS. 100 microm by 100 microm vias were patterned in the encapsulation layer to expose electrical contacts. PPS encapsulated conductors can be stretched uniaxially to 80%, and the PDMS encapsulated conductor can be stretched to ˜15%, without losing electrical conduction. We also introduced acrylate-based shape memory polymers (SMPs) as a new type of substrate for stretchable conductors. Their stiffness can be tuned by varying the monomer composition or by changing the ambient temperature. Thin gold film conductors deposited on pre-strained SMPs remain conductive when first stretched and then relaxed to their pre-strain value. Moreover, an SMP can also serve as a stretchable carrier to make pre-strained conductors on an overlying PDMS membrane. The resistance of gold conductors made on pre-strained PDMS changes less during stretching than that made on non-pre-strained PDMS substrate. We built a model of the electrical resistance in function of strain. The model is based on the topography of the thin gold film on PDMS. This model is a first attempt at predicting electrical resistance of stretchable thin gold film conductors. Lastly, we fabricated stretchable microelectrode arrays (SMEAs). They were utilized at Columbia University to study traumatic brain injury (TBI). Tissues cultured on SMEA remained viable for 19 days, and the electrodes were able to both stimulate and record neural tissue activity before, during and after stretching. Therefore SMEAs are able to bring together mechanical injury, electrophysiological recording and pharmacological studies. The SMEAs could serve as in vitro platforms for high throughput therapeutic screening and discovery for traumatic injury. The ability to reproducibly fabricate stretchable conductors using micro-fabrication technology will facilitate adoption by industry. The ability to understand the stretching mechanism will enable us to design more robust material systems. The SMEA prototypes demonstrate that stretchable conductors are practical, and their mechanical compatibility with biological systems also makes them candidates for use in biomedical devices.

Investigation of Proposed Process Sequence for the Array Automated Assembly Task, Phase 2. [low cost silicon solar array fabrication

NASA Technical Reports Server (NTRS)

Mardesich, N.; Garcia, A.; Bunyan, S.; Pepe, A.

1979-01-01

The technological readiness of the proposed process sequence was reviewed. Process steps evaluated include: (1) plasma etching to establish a standard surface; (2) forming junctions by diffusion from an N-type polymeric spray-on source; (3) forming a p+ back contact by firing a screen printed aluminum paste; (4) forming screen printed front contacts after cleaning the back aluminum and removing the diffusion oxide; (5) cleaning the junction by a laser scribe operation; (6) forming an antireflection coating by baking a polymeric spray-on film; (7) ultrasonically tin padding the cells; and (8) assembling cell strings into solar circuits using ethylene vinyl acetate as an encapsulant and laminating medium.

Hybrid Encapsulated Ionic Liquids for Post-Combustion Carbon Dioxide (CO 2) Capture

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

Brennecke, Joan F; Degnan, Jr, Thomas Francis; McCready, Mark J.

Ionic liquids (ILs) and Phase Change Ionic Liquids (PCILs) are excellent materials for selective removal of carbon dioxide from dilute post-combustion streams. However, they are typically characterized as having high viscosities, which impairs their effectiveness due to mass transfer limitations, caused by the high viscosities. In this project, we are examining the benefits of encapsulating ILs and PCILs in thin polymeric shells to produce particles of approximately 100 to 600 µm in diameter that can be used in a fluidized bed absorber. The particles are produced by microencapsulation of the ILs and PCILs in CO 2-permeable polymer shells. Here wemore » report on the encapsulation of the IL and PCIL materials, thermodynamic testing of the encapsulated materials, mass transfer measurements in both a fluidized bed and a packed bed, determination of the effect of impurities (SO 2, NO x and water) on the free and encapsulated IL and PCIL, recyclability of the CO 2 uptake, selection and synthesis of kg quantities of the IL and PCIL, identification of scale-up methods for encapsulation and production of a kg quantity of the PCIL, construction and shakedown of the laboratory scale unit to test the encapsulated particles for CO 2 capture ability and efficiency, use of our mass transfer model to predict mass transfer and identify optimal properties of the encapsulated particles, and initial testing of the encapsulated particles in the laboratory scale unit. We also show our attempts at developing shell materials that are resistant to water permeation. Overall, we have shown that the selected IL and PCIL can be successfully encapsulated in polymer shells and the methods scaled up to production levels. The IL/PCIL and encapsulated IL/PCIL react irreversibly with SO 2 and NO x so the CO 2 capture unit would need to be placed after the flue gas desulfurization and NO x reduction units. However, the reaction with CO 2 in the presence of water is completely reversible. Therefore, it is not necessary to exclude water from the capsules. Mass transfer in the fluidized and packed beds confirm that the fluidized bed arrangement is preferred and that the mass transfer can be predicted accurately by the rate based model that we have developed. Absorption and desorption experiments in the laboratory scale unit show good uptake and recyclability.« less

A method for encapsulating high voltage power transformers

NASA Astrophysics Data System (ADS)

Sanchez, Robert O.

Voltage breakdowns become a major concern in reducing the size of high-voltage power converter transformers. Even the smallest of voids can provide a path for corona discharge which can cause a dielectric breakdown leading to a transformer failure. A method of encapsulating small high voltage transformers has been developed. The method virtually eliminates voids in the impregnation material, provides an exceptional dielectric between windings and provides a mechanically rugged package. The encapsulation material is a carboxyl terminated butadiene nitril (CTBN) modified mica filled epoxy. The method requires heat/vacuum to impregnate the coil and heat/pressure to cure the encapsulant. The transformer package utilizes a diallyl phthalate (DAP) contact assembly in which a coated core/coil assembly is mounted and soldered. This assembly is then loaded into an RTV mold and the encapsulation process begins.

Performance degradation of grid-tied photovoltaic modules in a hot-dry climatic condition

NASA Astrophysics Data System (ADS)

Suleske, Adam; Singh, Jaspreet; Kuitche, Joseph; Tamizh-Mani, Govindasamy

2011-09-01

The crystalline silicon photovoltaic (PV) modules under open circuit conditions typically degrade at a rate of about 0.5% per year. However, it is suspected that the modules in an array level may degrade, depending on equipment/frame grounding and array grounding, at higher rates because of higher string voltage and increased module mismatch over the years of operation in the field. This paper compares and analyzes the degradation rates of grid-tied photovoltaic modules operating over 10-17 years in a desert climatic condition of Arizona. The nameplate open-circuit voltages of the arrays ranged between 400 and 450 V. Six different types/models of crystalline silicon modules with glass/glass and glass/polymer constructions were evaluated. About 1865 modules were inspected using an extended visual inspection checklist and infrared (IR) scanning. The visual inspection checklist included encapsulant discoloration, cell/interconnect cracks, delamination and corrosion. Based on the visual inspection and IR studies, a large fraction of these modules were identified as allegedly healthy and unhealthy modules and they were electrically isolated from the system for currentvoltage (I-V) measurements of individual modules. The annual degradation rate for each module type is determined based on the I-V measurements.

In vivo Characterization of Amorphous Silicon Carbide As a Biomaterial for Chronic Neural Interfaces

PubMed Central

Knaack, Gretchen L.; McHail, Daniel G.; Borda, German; Koo, Beomseo; Peixoto, Nathalia; Cogan, Stuart F.; Dumas, Theodore C.; Pancrazio, Joseph J.

2016-01-01

Implantable microelectrode arrays (MEAs) offer clinical promise for prosthetic devices by enabling restoration of communication and control of artificial limbs. While proof-of-concept recordings from MEAs have been promising, work in animal models demonstrates that the obtained signals degrade over time. Both material robustness and tissue response are acknowledged to have a role in device lifetime. Amorphous Silicon carbide (a-SiC), a robust material that is corrosion resistant, has emerged as an alternative encapsulation layer for implantable devices. We systematically examined the impact of a-SiC coating on Si probes by immunohistochemical characterization of key markers implicated in tissue-device response. After implantation, we performed device capture immunohistochemical labeling of neurons, astrocytes, and activated microglia/macrophages after 4 and 8 weeks of implantation. Neuron loss and microglia activation were similar between Si and a-SiC coated probes, while tissue implanted with a-SiC displayed a reduction in astrocytes adjacent to the probe. These results suggest that a-SiC has a similar biocompatibility profile as Si, and may be suitable for implantable MEA applications as a hermetic coating to prevent material degradation. PMID:27445672

Measurement of insulation integrity of IUE camera tube facsimiles by partial discharges method and diffusion of gases through various silicone rubbers

NASA Technical Reports Server (NTRS)

Bever, R. S.

1977-01-01

Several dummy tubes imitating the IUE Camera System design were encapsulated with Solithane 2, Conathane EN-11, Green and Black Hysols and SMRD 432. Various flaws were purposefully placed in some of these. Partial discharge testing in vacuum under direct voltage conditions was carried once a week for 12 weeks, 15 kv dc being applied during normal working hours for 40 hours duration per week. None of the units showed much damage during this time judging by the P.D. energy histograms. A more complete mathematical presentation is given on diffusion and permeation than previously. Measurements of diffusion constants for various silicone rubbers are carried out by the Time-Lag method and compared to other determinations in the literature. Calculations of the time required for diffusion through a thick wall are demonstrated in the long time approximation and for dimensions pertaining to void and wall sizes of a delamination problem in the LANDSAT-C vidicon tubes. An actual delaminated LANDSAT-C tube and some facsimiles are immersed in vacuum for long periods and tested for catastrophic breakdown due to diffusion of gas, by application of high voltage.

In vivo Characterization of Amorphous Silicon Carbide As a Biomaterial for Chronic Neural Interfaces.

PubMed

Knaack, Gretchen L; McHail, Daniel G; Borda, German; Koo, Beomseo; Peixoto, Nathalia; Cogan, Stuart F; Dumas, Theodore C; Pancrazio, Joseph J

2016-01-01

Implantable microelectrode arrays (MEAs) offer clinical promise for prosthetic devices by enabling restoration of communication and control of artificial limbs. While proof-of-concept recordings from MEAs have been promising, work in animal models demonstrates that the obtained signals degrade over time. Both material robustness and tissue response are acknowledged to have a role in device lifetime. Amorphous Silicon carbide (a-SiC), a robust material that is corrosion resistant, has emerged as an alternative encapsulation layer for implantable devices. We systematically examined the impact of a-SiC coating on Si probes by immunohistochemical characterization of key markers implicated in tissue-device response. After implantation, we performed device capture immunohistochemical labeling of neurons, astrocytes, and activated microglia/macrophages after 4 and 8 weeks of implantation. Neuron loss and microglia activation were similar between Si and a-SiC coated probes, while tissue implanted with a-SiC displayed a reduction in astrocytes adjacent to the probe. These results suggest that a-SiC has a similar biocompatibility profile as Si, and may be suitable for implantable MEA applications as a hermetic coating to prevent material degradation.

Cobalt silicide nanocables grown on Co films: synthesis and physical properties.

PubMed

Hsin, Cheng-Lun; Yu, Shih-Ying; Wu, Wen-Wei

2010-12-03

Single-crystalline cobalt silicide/SiO(x) nanocables have been grown on Co thin films on an SiO(2) layer by a self-catalysis process via vapor-liquid-solid mechanism. The nanocables consist of a core of CoSi nanowires and a silicon oxide shell with a length of several tens of micrometers. In the confined space in the oxide shell, the CoSi phase is stable and free from agglomeration in samples annealed in air ambient at 900 °C for 1 h. The nanocable structure came to a clear conclusion that the thermal stability of the silicide nanowires can be resolved by the shell encapsulation. Cobalt silicide nanowires were obtained from the nanocable structure. The electrical properties of the CoSi nanowires have been found to be compatible with their thin film counterpart and a high maximum current density of the nanowires has been measured. One way to obtain silicate nanowires has been demonstrated. The silicate compound, which is composed of cobalt, silicon and oxygen, was achieved. The Co silicide/oxide nanocables are potentially useful as a key component of silicate nanowires, interconnects and magnetic units in nanoelectronics.

HfSe2 and ZrSe2: Two-dimensional semiconductors with native high-κ oxides

PubMed Central

Mleczko, Michal J.; Zhang, Chaofan; Lee, Hye Ryoung; Kuo, Hsueh-Hui; Magyari-Köpe, Blanka; Moore, Robert G.; Shen, Zhi-Xun; Fisher, Ian R.; Nishi, Yoshio; Pop, Eric

2017-01-01

The success of silicon as a dominant semiconductor technology has been enabled by its moderate band gap (1.1 eV), permitting low-voltage operation at reduced leakage current, and the existence of SiO2 as a high-quality “native” insulator. In contrast, other mainstream semiconductors lack stable oxides and must rely on deposited insulators, presenting numerous compatibility challenges. We demonstrate that layered two-dimensional (2D) semiconductors HfSe2 and ZrSe2 have band gaps of 0.9 to 1.2 eV (bulk to monolayer) and technologically desirable “high-κ” native dielectrics HfO2 and ZrO2, respectively. We use spectroscopic and computational studies to elucidate their electronic band structure and then fabricate air-stable transistors down to three-layer thickness with careful processing and dielectric encapsulation. Electronic measurements reveal promising performance (on/off ratio > 106; on current, ~30 μA/μm), with native oxides reducing the effects of interfacial traps. These are the first 2D materials to demonstrate technologically relevant properties of silicon, in addition to unique compatibility with high-κ dielectrics, and scaling benefits from their atomically thin nature. PMID:28819644

Highly efficient enzyme encapsulation in a protein nanocage: towards enzyme catalysis in a cellular nanocompartment mimic

NASA Astrophysics Data System (ADS)

Schoonen, Lise; Nolte, Roeland J. M.; van Hest, Jan C. M.

2016-07-01

The study of enzyme behavior in small nanocompartments is crucial for the understanding of biocatalytic processes in the cellular environment. We have developed an enzymatic conjugation strategy to attach a model enzyme to the interior of a cowpea chlorotic mottle virus capsid. It is shown that with this methodology high encapsulation efficiencies can be achieved. Additionally, we demonstrate that the encapsulation does not affect the enzyme performance in terms of a decreased activity or a hampered substrate diffusion. Finally, it is shown that the encapsulated enzymes are protected against proteases. We believe that our strategy can be used to study enzyme kinetics in an environment that approaches physiological conditions.The study of enzyme behavior in small nanocompartments is crucial for the understanding of biocatalytic processes in the cellular environment. We have developed an enzymatic conjugation strategy to attach a model enzyme to the interior of a cowpea chlorotic mottle virus capsid. It is shown that with this methodology high encapsulation efficiencies can be achieved. Additionally, we demonstrate that the encapsulation does not affect the enzyme performance in terms of a decreased activity or a hampered substrate diffusion. Finally, it is shown that the encapsulated enzymes are protected against proteases. We believe that our strategy can be used to study enzyme kinetics in an environment that approaches physiological conditions. Electronic supplementary information (ESI) available: Experimental procedures for the cloning, expression, and purification of all proteins, as well as supplementary figures and calculations. See DOI: 10.1039/c6nr04181g

Development of a statistically proven injection molding method for reaction bonded silicon nitride, sintering reaction bonded silicon nitride, and sintered silicon nitride

NASA Astrophysics Data System (ADS)

Steiner, Matthias

A statistically proven, series injection molding technique for ceramic components was developed for the construction of engines and gas turbines. The flow behavior of silicon injection-molding materials was characterized and improved. Hot-isostatic-pressing reaction bonded silicon nitride (HIPRBSN) was developed. A nondestructive component evaluation method was developed. An injection molding line for HIPRBSN engine components precombustion chamber, flame spreader, and valve guide was developed. This line allows the production of small series for engine tests.

Novel high refractive index, thermally conductive additives for high brightness white LEDs

NASA Astrophysics Data System (ADS)

Hutchison, Richard Stephen

In prior works the inclusion of nanoparticle fillers has typically been shown to increase the thermal conductivity or refractive index of polymer nanocomposites separately. High refractive index zirconia nanoparticles have already proved their merit in increasing the optical efficiency of encapsulated light emitting diodes. However, the thermal properties of zirconia-silicone nanocomposites have yet to be investigated. While phosphor-converted light emitting diodes are at the forefront of solid-state lighting technologies for producing white light, they are plagued by efficiency losses due to excessive heating at the semiconductor die and in and around the phosphor particles, as well as photon scattering losses in the phosphor layer. It would then be of great interest if the high refractive index nanoparticles were found to both be capable of increasing the refractive index, thus reducing the optical scattering, and also the thermal conductivity, channeling more heat away from the LED die and phosphors, mitigating efficiency losses from heat. Thermal conductance measurements on unfilled and nanoparticle loaded silicone samples were conducted to quantify the effect of the zirconia nanoparticle loading on silicone nanocomposite thermal conductivity. An increase in thermal conductivity from 0.27 W/mK to 0.49 W/mK from base silicone to silicone with 33.5 wt% zirconia nanoparticles was observed. This trend closely mirrored a basic rule of mixtures prediction, implying a further enhancement in thermal conductivity could be achieved at higher nanoparticle loadings. The optical properties of transparency and light extraction efficiency of these composites were also investigated. While overall the zirconia nanocomposite showed good transparency, there was a slight decrease at the shorter wavelengths with increasing zirconia content. For longer wavelength LEDs, such as green or red, this might not matter, but phosphor-converted white LEDs use a blue LED as the photon source making this decrease in transparency important to note. This decrease in transparency may be partially or wholly why a decrease in light extraction efficiency is observed at the 33.5 wt% zirconia loading fraction used for the LED samples. Preliminary aging studies under full and enhanced power conditions were conducted over 500 and 1000 hours to observe any changes in the spectral output power and phosphor conversion efficiency of the LEDs due to inclusion of the zirconia nanoparticles. It was found that the nanoparticles have no negative effect on the aging properties but also show no enhancement in relative output power over a preliminary aging study. However, their inclusion did result in increased phosphor conversion efficiency over the use of an unfilled silicone. This increase was seen as around a 10% or greater enhancement for the nanocomposite over that for the base Sylgard silicone. These experiments were originally conducted on the commercially available methylated Sylgard 184 silicone and then again on a higher refractive index methyl-phenyl silicone from Momentive. While some of the results from the Momentive silicone were perplexing, it was seen that, even without the inclusion of nanoparticles, the Momentive silicone had a higher refractive index, better aging properties, and a higher phosphor conversion efficiency over 500 hours under enhanced power conditions, warranting further studies into methyl-phenyl silicone nanocomposites.

Workshop summary: New silicon cells

NASA Technical Reports Server (NTRS)

Meulenberg, A.; Iles, P. A.

1993-01-01

The workshop on new silicon cells held during SPRAT12 is summarized. A smaller than average group attended this workshop reflecting the reduction in research dollars available to this portion of the photovoltaics community. Despite the maturity of the silicon technology, a core of the group maintained an excitement about new developments and potential opportunities. The group addressed both the implications and the applications of recent developments. Topics discussed include: light trapping and ultrathin silicon cells; different uses for silicon cells; new silicon cell developments; and radiation tolerant high efficiency cells.

[Study of purity tests for silicone resins].

PubMed

Sato, Kyoko; Otsuki, Noriko; Ohori, Akio; Chinda, Mitsuru; Furusho, Noriko; Osako, Tsutomu; Akiyama, Hiroshi; Kawamura, Yoko

2012-01-01

In the 8th edition of Japan's Specifications and Standards for Food Additives, the purity test for silicone resins requires the determination of the refractive index and kinetic viscosity of the extracted silicone oil, and allows for only a limited amount of silicon dioxide. In the purity test, carbon tetrachloride is used to separate the silicone oil and silicon dioxide. To exclude carbon tetrachloride, methods were developed for separating the silicone oil and silicon dioxide from silicone resin, which use hexane and 10% n-dodecylbenzenesulfonic acid in hexane. For silicone oil, the measured refractive index and kinetic viscosity of the silicone oil obtained from the hexane extract were shown to be equivalent to those of the intact silicone oil. In regard to silicon dioxide, it was confirmed that, following the separation with 10% n-dodecylbenzenesulfonic acid in hexane, the level of silicon dioxide in silicone resin can be accurately determined. Therefore, in this study, we developed a method for testing the purity of silicone resins without the use of carbon tetrachloride, which is a harmful reagent.

Simultaneous quantification of tumor uptake for targeted and non-targeted liposomes and their encapsulated contents by ICP-MS

PubMed Central

Cheng, Zhiliang; Zaki, Ajlan Al; Hui, James Z; Tsourkas, Andrew

2012-01-01

Liposomes are intensively being developed for biomedical applications including drug and gene delivery. However, targeted liposomal delivery in cancer treatment is a very complicated multi-step process. Unfavorable liposome biodistribution upon intravenous administration and membrane destabilization in blood circulation could result in only a very small fraction of cargo reaching the tumors. It would therefore be desirable to develop new quantitative strategies to track liposomal delivery systems to improve the therapeutic index and decrease systemic toxicity. Here, we developed a simple and non-radiative method to quantify the tumor uptake of targeted and non-targeted control liposomes as well as their encapsulated contents simultaneously. Specifically, four different chelated lanthanide metals were encapsulated or surface-conjugated onto tumor-targeted and non-targeted liposomes, respectively. The two liposome formulations were then injected into tumor-bearing mice simultaneously and their tumor delivery was determined quantitatively via inductively coupled plasma-mass spectroscopy (ICP-MS), allowing for direct comparisons. Tumor uptake of the liposomes themselves and their encapsulated contents were consistent with targeted and non-targeted liposome formulations that were injected individually. PMID:22882145

Polymer-encapsulated organic nanoparticles for fluorescence and photoacoustic imaging.

PubMed

Li, Kai; Liu, Bin

2014-09-21

Polymer encapsulated organic nanoparticles have recently attracted increasing attention in the biomedical field because of their unique optical properties, easy fabrication and outstanding performance as imaging and therapeutic agents. Of particular importance is the polymer encapsulated nanoparticles containing conjugated polymers (CP) or fluorogens with aggregation induced emission (AIE) characteristics as the core, which have shown significant advantages in terms of tunable brightness, superb photo- and physical stability, good biocompatibility, potential biodegradability and facile surface functionalization. In this review, we summarize the latest advances in the development of polymer encapsulated CP and AIE fluorogen nanoparticles, including preparation methods, material design and matrix selection, nanoparticle fabrication and surface functionalization for fluorescence and photoacoustic imaging. We also discuss their specific applications in cell labeling, targeted in vitro and in vivo imaging, blood vessel imaging, cell tracing, inflammation monitoring and molecular imaging. We specially focus on strategies to fine-tune the nanoparticle property (e.g. size and fluorescence quantum yield) through precise engineering of the organic cores and careful selection of polymer matrices. The review also highlights the merits and limitations of these nanoparticles as well as strategies used to overcome the limitations. The challenges and perspectives for the future development of polymer encapsulated organic nanoparticles are also discussed.

The influence of intraperitoneal transplantation of free and encapsulated Langerhans islets on the second set phenomenon.

PubMed

Orłowski, Tadeusz; Godlewska, Ewa; Mościcka, Maria; Sitarek, Elzbieta

2003-12-01

To protect the allografts or xenografts against transplant rejection special semipermeable membranes are applied. So far, there are only a few studies on the influence of an immunoisolated graft on the recipient immune system. Therefore, the possibility that an intraperitoneally grafted alginate/poly L-lysine/alginate (APA) coated pancreatic islets graft can effectively sensitize the recipient and provoke second set phenomenon was studied. C3H male mice and male WAG rats were used as donors of full-thickness skin and of free or encapsulated islet intraperitoneal grafts. Male BALB/c mice served as recipients. Skin grafts were performed following the method of Billingham and Medawar. The length of the second skin graft survival time served as the criterion for the sensitizing capacity of the primary graft. APA encapsulation of islets delayed but has not prevented the development of the second set phenomenon. However, the second skin graft rejection time was significantly longer after grafting of encapsulated islets than after free islets transplantation. APA microencapsulation of intraperitoneally transplanted islets delayed but did not prevent the development of the second set phenomenon. Encapsulation does not ensure complete immunoisolation, but only creates "an artificially immunoprivileged site of transplantation."

An Improved Thermal Conductivity Polyurethane Composite for a Space Borne 20KV Power Supply

NASA Technical Reports Server (NTRS)

Shapiro, Andrew A.; Haque, Inam

2005-01-01

This effort was designed to find a way to reduce the temperature rise of critical components of a 20KV High Voltage Power Supply (HVPS) by improving the overall thermal conductivity of the encapsulated modules. Three strategies were evaluated by developing complete procedures, preparing samples, and performing tests. The three strategies were: 1. Improve the thermal conductivity of the polyurethane encapsulant through the addition of thermally conductive powder while minimizing impact on other characteristics of the encapsulant. 2. Improve the thermal conductivity of the polyurethane encapsulated assembly by the addition of a slab of thermally conductive, electrically insulating material, which is to act as a heat spreader. 3. Employ a more thermally conductive substrate (Al203) with the existing encapsulation scheme. The materials were chosen based on the following criteria: high dielectric breakdown strength; high thermal conductivity, ease of manufacturing, high compliance, and other standard space qualified materials properties (low out-gassing, etc.). An optimized cure was determined by a statistical design of experiments for both filled and unfilled materials. The materials were characterized for the desired properties and a complete process was developed and tested. The thermal performance was substantially improved and the strategies may be used for space flight.

Encapsulated Three-Dimensional Culture Supports Development of Nonhuman Primate Secondary Follicles1

PubMed Central

Xu, Min; West-Farrell, Erin R.; Stouffer, Richard L.; Shea, Lonnie D.; Woodruff, Teresa K.; Zelinski, Mary B.

2009-01-01

In vitro ovarian follicle cultures may provide fertility-preserving options to women facing premature infertility due to cancer therapies. An encapsulated three-dimensional (3-D) culture system utilizing biomaterials to maintain cell-cell communication and support follicle development to produce a mature oocyte has been developed for the mouse. We tested whether this encapsulated 3-D system would also support development of nonhuman primate preantral follicles, for which in vitro growth has not been reported. Three questions were investigated: Does the cycle stage at which the follicles are isolated affect follicle development? Does the rigidity of the hydrogel influence follicle survival and growth? Do follicles require luteinizing hormone (LH), in addition to follicle-stimulating hormone (FSH), for steroidogenesis? Secondary follicles were isolated from adult rhesus monkeys, encapsulated within alginate hydrogels, and cultured individually for ≤30 days. Follicles isolated from the follicular phase of the menstrual cycle had a higher survival rate (P < 0.05) than those isolated from the luteal phase; however, this difference may also be attributed to differing sizes of follicles isolated during the different stages. Follicles survived and grew in two hydrogel conditions (0.5% and 0.25% alginate). Follicle diameters increased to a greater extent (P < 0.05) in the presence of FSH alone than in FSH plus LH. Regardless of gonadotropin treatment, follicles produced estradiol, androstenedione, and progesterone by 14–30 days in vitro. Thus, an alginate hydrogel maintains the 3-D structure of individual secondary macaque follicles, permits follicle growth, and supports steroidogenesis for ≤30 days in vitro. This study documents the first use of the alginate system to maintain primate tissue architecture, and findings suggest that encapsulated 3-D culture will be successful in supporting the in vitro development of human follicles. PMID:19474063

Micro-Encapsulation of non-aqueous solvents for energy-efficient carbon capture

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

Stolaroff, Joshua K; Ye, Congwang; Oakdale, James

Here, we demonstrate micro-encapsulation of several promising designer solvents: an IL, PCIL, and CO2BOL. We develop custom polymers that cure by UV light in the presence of each solvent while maintaining high CO2 permeability. We use several new process strategies to accommodate the viscosity and phase changes. We then measure and compare the CO2 absorption rate and capacity as well as the multi-cycle performance of the encapsulated solvents. These results are compared with previous work on encapsulated sodium carbonate solution. The prospects for designer solvents to reduce the cost of post-combustion capture and the implications for process design with encapsulatedmore » solvents are discussed.« less

Properties of probiotics and encapsulated probiotics in food.

PubMed

Ozyurt, V Hazal; Ötles, Semih

2014-01-01

Probiotics are microorganisms which confer health benefits upon application in sufficiently-high viable cell amounts. Probiotics are typically members of Lactobacillus and Bifidobacterium species commonly associated with human gastrointestinal tracts. In the recent past, there has been a rising interest in producing functional foods containing encapsulated probiotic bacteria. Recent studies have been reported using dairy products like cheese, yogurt and ice cream as food carrier, and non-dairy products like meat, fruits, cereals, chocolate, etc. However, the industrial sector contains only few encapsulated probiotic products. Probiotics have been developed by several companies in a capsule or a tablet form. The review compiles probiotics, encapsulation technology and cell life in the food matrices.

Defining Threshold Values of Encapsulant and Backsheet Adhesion for PV Module Reliability

DOE PAGES

Bosco, Nick; Eafanti, Joshua; Kurtz, Sarah; ...

2017-10-04

The width-tapered cantilever beam method is used to quantify the debond energy (adhesion) of encapsulant and backsheet structures of 32 modules collected from the field. The collected population of modules contains both those that have remained intact and those with instances of either or both encapsulant and backsheet delamination. From this survey, initial threshold values (an adhesion value above which a module should remain intact throughout its lifetime) for encapsulant and backsheet interfaces are proposed. For encapsulants this value is ~ 160J/m 2 and for backsheets ~ 10J/m 2. Here, it is expected that these values will continue to bemore » refined and evolve as the width-tapered cantilever beam method gets adopted by the PV industry, and that they may aid in the future improvement of accelerated lifetime tests and the development of new, low-cost materials.« less

Boar sperm encapsulation reduces in vitro polyspermy.

PubMed

Faustini, M; Bucco, M; Galeati, G; Spinaci, M; Villani, S; Chlapanidas, T; Ghidoni, I; Vigo, D; Torre, M L

2010-04-01

A boar sperm encapsulation technology in barium alginate has been developed to enhance reproductive performances and spermatozoa preservation time; aim of this work was to evaluate the effect of in vitro sperm encapsulation on polyspermy as a function of storage time at 18 degrees C. A total number of 40 in vitro fertilization (IVF) tests were performed using encapsulated or diluted spermatozoa (20 IVF each treatment). Overall, 1288 in vitro matured oocytes were fertilized with spermatozoa stored at 24, 48 or 72 h at 18 degrees C for both treatments polyspermy and normospermy, and the non-penetration rates were assessed by optical microscopy. Results indicate a significant reduction in risk of polyspermic oocytes when spermatozoa are preserved in barium alginate membranes (incidence risk ratio: 0.766 with respect to diluted); such enhancement could be explained by lesser damage of sperm membranes achieved by encapsulation technology.

Defining Threshold Values of Encapsulant and Backsheet Adhesion for PV Module Reliability: Preprint

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

Bosco, Nicholas S; Kurtz, Sarah; Eafanti, Joshua

2017-08-28

The width-tapered cantilever beam method is used to quantify the debond energy (adhesion) of encapsulant and backsheet structures of 27 modules collected from the field. The collected population of modules contains both those that have remained in-tact and those with instances of either or both encapsulant and backsheet delamination. From this survey, initial threshold values (an adhesion value above which a module should remain intact throughout its lifetime) for encapsulant and backsheet interfaces are proposed. For encapsulants this value is about 60 J/m2 and for backsheets about 20 J/m2. It is expected that these values will continue to be refinedmore » and evolve as the width-tapered cantilever beam method becomes adopted by the PV industry, and that they may aid in the future improvement of accelerated lifetime tests and the development of new, low-cost materials.« less

Chapter 10.2: Encapsulant Materials for PV Modules

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

Kempe, Michael D

2017-01-07

Encapsulant materials used in photovoltaic (PV) modules serve multiple purposes; it provides optical coupling of PV cells and protection against environmental stress. Polymers must perform these functions under prolonged periods of high temperature, humidity, and UV radiation. When PV panels were first developed in the 1960s and the 1970s, the dominant encapsulants were based on polydimethyl siloxane (PDMS). Ethylene-co-vinyl acetate (EVA) is currently the dominant encapsulant chosen for PV applications, not because it has the best combination of properties, but because it is an economical option with an established history of acceptable durability. Getting new products onto the market ismore » challenging because there is no room for dramatic improvements, and one must balance the initial cost and performance with the unknowns of long-term service life. Recently, there has been renewed interest in using alternative encapsulant materials with some significant manufacturers switching from EVA to polyolefin elastomer-based (POE) alternatives.« less

Stable metal-organic frameworks containing single-molecule traps for enzyme encapsulation.

PubMed

Feng, Dawei; Liu, Tian-Fu; Su, Jie; Bosch, Mathieu; Wei, Zhangwen; Wan, Wei; Yuan, Daqiang; Chen, Ying-Pin; Wang, Xuan; Wang, Kecheng; Lian, Xizhen; Gu, Zhi-Yuan; Park, Jihye; Zou, Xiaodong; Zhou, Hong-Cai

2015-01-19

Enzymatic catalytic processes possess great potential in chemical manufacturing, including pharmaceuticals, fuel production and food processing. However, the engineering of enzymes is severely hampered due to their low operational stability and difficulty of reuse. Here, we develop a series of stable metal-organic frameworks with rationally designed ultra-large mesoporous cages as single-molecule traps (SMTs) for enzyme encapsulation. With a high concentration of mesoporous cages as SMTs, PCN-333(Al) encapsulates three enzymes with record-high loadings and recyclability. Immobilized enzymes that most likely undergo single-enzyme encapsulation (SEE) show smaller Km than free enzymes while maintaining comparable catalytic efficiency. Under harsh conditions, the enzyme in SEE exhibits better performance than free enzyme, showing the effectiveness of SEE in preventing enzyme aggregation or denaturation. With extraordinarily large pore size and excellent chemical stability, PCN-333 may be of interest not only for enzyme encapsulation, but also for entrapment of other nanoscaled functional moieties.

Stable metal-organic frameworks containing single-molecule traps for enzyme encapsulation

NASA Astrophysics Data System (ADS)

Feng, Dawei; Liu, Tian-Fu; Su, Jie; Bosch, Mathieu; Wei, Zhangwen; Wan, Wei; Yuan, Daqiang; Chen, Ying-Pin; Wang, Xuan; Wang, Kecheng; Lian, Xizhen; Gu, Zhi-Yuan; Park, Jihye; Zou, Xiaodong; Zhou, Hong-Cai

2015-01-01

Enzymatic catalytic processes possess great potential in chemical manufacturing, including pharmaceuticals, fuel production and food processing. However, the engineering of enzymes is severely hampered due to their low operational stability and difficulty of reuse. Here, we develop a series of stable metal-organic frameworks with rationally designed ultra-large mesoporous cages as single-molecule traps (SMTs) for enzyme encapsulation. With a high concentration of mesoporous cages as SMTs, PCN-333(Al) encapsulates three enzymes with record-high loadings and recyclability. Immobilized enzymes that most likely undergo single-enzyme encapsulation (SEE) show smaller Km than free enzymes while maintaining comparable catalytic efficiency. Under harsh conditions, the enzyme in SEE exhibits better performance than free enzyme, showing the effectiveness of SEE in preventing enzyme aggregation or denaturation. With extraordinarily large pore size and excellent chemical stability, PCN-333 may be of interest not only for enzyme encapsulation, but also for entrapment of other nanoscaled functional moieties.

Functional assessment of encapsulated citral for controlling necrotic enteritis in broiler chickens.

PubMed

Yang, Yuexi; Wang, Qi; Diarra, Moussa S; Yu, Hai; Hua, Yufei; Gong, Joshua

2016-04-01

Development of viable alternatives to antibiotics to control necrotic enteritis (NE) caused by Clostridium perfringensis becoming urgent for chicken production due to pessures on poultry producers to limit or stop the use of antibiotics in feed. We have previously identified citral as a potential alternative to antibiotics. Citral has strong antimicrobial activity and can be encasupsulated in a powder form for protection from loss during feed processing, storage, and intestinal delivery. In the present study, encapsulated citral was evaluated both in vitro and in vivo for its antimicrobial activity against C. perfringens Encapsulation did not adversely affect the antimicrobial activity of citral. In addition, encapsulated citral was superior to the unencapsulated form in retaining its antimicrobial activity after treatment with simulated gastrointestinal fluids and in the presence of chicken intestinal digesta. In addition, the higher antimicrobial activity of encapsulated citral was confirmed in digesta samples from broilers that had been gavaged with encapsulated or unencapsulated citral. In broilers infected with C. perfringens, the diets supplemented with encapsualted citral at both 250 and 650 μg/g significantly reduced intestinal NE lesions, which was comparable to the effect of bacitracin- and salinomycin-containing diets. However, supplementation with the encapsulated citral appeared to have no significant impact on the intestinal burden of Lactobacillus These data indicate that citral can be used to control NE in chickens after proper protection by encapsulation. © Crown copyright 2016.

Preparation and Evaluation of Multiple Nanoemulsions Containing Gadolinium (III) Chelate as a Potential Magnetic Resonance Imaging (MRI) Contrast Agent.

PubMed

Sigward, Estelle; Corvis, Yohann; Doan, Bich-Thuy; Kindsiko, Kadri; Seguin, Johanne; Scherman, Daniel; Brossard, Denis; Mignet, Nathalie; Espeau, Philippe; Crauste-Manciet, Sylvie

2015-09-01

The objective was to develop, characterize and assess the potentiality of W1/O/W2 self-emulsifying multiple nanoemulsions to enhance signal/noise ratio for Magnetic Resonance Imaging (MRI). For this purpose, a new formulation, was designed for encapsulation efficiency and stability. Various methods were used to characterize encapsulation efficiency ,in particular calorimetric methods (Differential Scanning Calorimetry (DSC), thermogravimetry analysis) and ultrafiltration. MRI in vitro relaxivities were assessed on loaded DTPA-Gd multiple nanoemulsions. Characterization of the formulation, in particular of encapsulation efficiency was a challenge due to interactions found with ultrafiltration method. Thanks to the specifically developed DSC protocol, we were able to confirm the formation of multiple nanoemulsions, differentiate loaded from unloaded nanoemulsions and measure the encapsulation efficiency which was found to be quite high with a 68% of drug loaded. Relaxivity studies showed that the self-emulsifying W/O/W nanoemulsions were positive contrast agents, exhibiting higher relaxivities than those of the DTPA-Gd solution taken as a reference. New self-emulsifying multiple nanoemulsions that were able to load satisfactory amounts of contrasting agent were successfully developed as potential MRI contrasting agents. A specific DSC protocol was needed to be developed to characterize these complex systems as it would be useful to develop these self-formation formulations.

High Efficiency, Low Cost Solar Cells Manufactured Using 'Silicon Ink' on Thin Crystalline Silicon Wafers

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

Antoniadis, H.

Reported are the development and demonstration of a 17% efficient 25mm x 25mm crystalline Silicon solar cell and a 16% efficient 125mm x 125mm crystalline Silicon solar cell, both produced by Ink-jet printing Silicon Ink on a thin crystalline Silicon wafer. To achieve these objectives, processing approaches were developed to print the Silicon Ink in a predetermined pattern to form a high efficiency selective emitter, remove the solvents in the Silicon Ink and fuse the deposited particle Silicon films. Additionally, standard solar cell manufacturing equipment with slightly modified processes were used to complete the fabrication of the Silicon Ink highmore » efficiency solar cells. Also reported are the development and demonstration of a 18.5% efficient 125mm x 125mm monocrystalline Silicon cell, and a 17% efficient 125mm x 125mm multicrystalline Silicon cell, by utilizing high throughput Ink-jet and screen printing technologies. To achieve these objectives, Innovalight developed new high throughput processing tools to print and fuse both p and n type particle Silicon Inks in a predetermined pat-tern applied either on the front or the back of the cell. Additionally, a customized Ink-jet and screen printing systems, coupled with customized substrate handling solution, customized printing algorithms, and a customized ink drying process, in combination with a purchased turn-key line, were used to complete the high efficiency solar cells. This development work delivered a process capable of high volume producing 18.5% efficient crystalline Silicon solar cells and enabled the Innovalight to commercialize its technology by the summer of 2010.« less

Characterization of Encapsulated Corrosion Inhibitors Containing Microparticles for Environmentally Friendly Smart Coatings

NASA Technical Reports Server (NTRS)

Pearman, Benjamin Pieter; Calle, Luz M.

2015-01-01

This poster presents the results obtained from experiments designed to evaluate the release properties, as well as the corrosion inhibition effectiveness, of several encapsulated corrosion inhibitors. Microencapsulation has been used in the development of environmentally friendly multifunctional smart coatings. This technique enables the incorporation of autonomous corrosion detection, inhibition and self-healing functionalities into many commercially available coating systems. Select environmentally friendly corrosion inhibitors were encapsulated in organic and inorganic pH-sensitive microparticles and their release in basic solutions was studied. The release rate results showed that the encapsulation can be tailored from fast, for immediate corrosion protection, to slow, which will provide continued long-term corrosion protection. The incorporation of several corrosion inhibitor release profiles into a coating provides effective corrosion protection properties. To investigate the corrosion inhibition efficiency of the encapsulated inhibitors, electrochemical techniques were used to obtain corrosion potential, polarization curve and polarization resistance data. These measurements were performed using the free as well as the encapsulated inhibitors singly or in combinations. Results from these electrochemical tests will be compared to those obtained from weight loss and other accelerated corrosion experiments.

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

Murugaiah, Anand

The objective of this program is to generate novel LED package designs that would provide 30% improvement in lumen/$ output. This was to be achieved by improving thermal management in encapsulants/ phosphors to reduce their temperatures. Currently, the heat that is generated during down conversion of blue light to longer wavelengths by the phosphors dispersed in the encapsulant does not have optimum thermal pathways for dissipation due to poor thermal conductivity of the encapsulant material. Additionally, high temperature in the encapsulant during operation is one of the primary failure modes in LED luminaires resulting in much shorter than expected life.more » The thermal issues manifest in color instability (yellowing, browning), cracking and hot spots in the encapsulant leading to failures. This work explored boron nitride (hBN) as thermal fillers in encapsulants to improve thermal conductivity while minimally impacting optical properties. Various approaches to Boron Nitride (BN) were evaluated and over 380 samples were generated to down select appropriate BN morphologies. We developed a range or BN materials for enabling thermal properties while attempting to minimally impact to optical properties.« less

Impact of a compound droplet on a flat surface: A model for single cell epitaxy.

PubMed

Tasoglu, Savas; Kaynak, Gozde; Szeri, Andrew J; Demirci, Utkan; Muradoglu, Metin

2010-08-01

The impact and spreading of a compound viscous droplet on a flat surface are studied computationally using a front-tracking method as a model for the single cell epitaxy. This is a technology developed to create two-dimensional and three-dimensional tissue constructs cell by cell by printing cell-encapsulating droplets precisely on a substrate using an existing ink-jet printing method. The success of cell printing mainly depends on the cell viability during the printing process, which requires a deeper understanding of the impact dynamics of encapsulated cells onto a solid surface. The present study is a first step in developing a model for deposition of cell-encapsulating droplets. The inner droplet representing the cell, the encapsulating droplet, and the ambient fluid are all assumed to be Newtonian. Simulations are performed for a range of dimensionless parameters to probe the deformation and rate of deformation of the encapsulated cell, which are both hypothesized to be related to cell damage. The deformation of the inner droplet consistently increases: as the Reynolds number increases; as the diameter ratio of the encapsulating droplet to the cell decreases; as the ratio of surface tensions of the air-solution interface to the solution-cell interface increases; as the viscosity ratio of the cell to encapsulating droplet decreases; or as the equilibrium contact angle decreases. It is observed that maximum deformation for a range of Weber numbers has (at least) one local minimum at We=2. Thereafter, the effects of cell deformation on viability are estimated by employing a correlation based on the experimental data of compression of cells between parallel plates. These results provide insight into achieving optimal parameter ranges for maximal cell viability during cell printing.

Sol-Generating Chemical Vapor into Liquid (SG-CViL) deposition – A facile method for encapsulation of diverse cell types in silica matrices

DOE PAGES

Johnston, Robert; Rogelj, Snezna; Harper, Jason C.; ...

2014-12-12

In nature, cells perform a variety of complex functions such as sensing, catalysis, and energy conversion which hold great potential for biotechnological device construction. However, cellular sensitivity to ex vivo environments necessitates development of bio–nano interfaces which allow integration of cells into devices and maintain their desired functionality. In order to develop such an interface, the use of a novel Sol-Generating Chemical Vapor into Liquid (SG-CViL) deposition process for whole cell encapsulation in silica was explored. In SG-CViL, the high vapor pressure of tetramethyl orthosilicate (TMOS) is utilized to deliver silica into an aqueous medium, creating a silica sol. Cellsmore » are then mixed with the resulting silica sol, facilitating encapsulation of cells in silica while minimizing cell contact with the cytotoxic products of silica generating reactions (i.e. methanol), and reduce exposure of cells to compressive stresses induced from silica condensation reactions. Using SG-CVIL, Saccharomyces cerevisiae (S. cerevisiae) engineered with an inducible beta galactosidase system were encapsulated in silica solids and remained both viable and responsive 29 days post encapsulation. By tuning SG-CViL parameters, thin layer silica deposition on mammalian HeLa and U87 human cancer cells was also achieved. Thus, the ability to encapsulate various cell types in either a multi cell (S. cerevisiae) or a thin layer (HeLa and U87 cells) fashion shows the promise of SG-CViL as an encapsulation strategy for generating cell–silica constructs with diverse functions for incorporation into devices for sensing, bioelectronics, biocatalysis, and biofuel applications.« less

Human beta-cell precursors mature into functional insulin-producing cells in an immunoisolation device: implications for diabetes cell therapies.

PubMed

Lee, Seung-Hee; Hao, Ergeng; Savinov, Alexei Y; Geron, Ifat; Strongin, Alex Y; Itkin-Ansari, Pamela

2009-04-15

Islet transplantation is limited by the need for chronic immunosuppression and the paucity of donor tissue. As new sources of human beta-cells are developed (e.g., stem cell-derived tissue), transplanting them in a durable device could obviate the need for immunosuppression, while also protecting the patient from any risk of tumorigenicity. Here, we studied (1) the survival and function of encapsulated human beta-cells and their progenitors and (2) the engraftment of encapsulated murine beta-cells in allo- and autoimmune settings. Human islets and human fetal pancreatic islet-like cell clusters were encapsulated in polytetrafluorethylene devices (TheraCyte) and transplanted into immunodeficient mice. Graft survival and function was measured by immunohistochemistry, circulating human C-peptide levels, and blood glucose levels. Bioluminescent imaging was used to monitor encapsulated neonatal murine islets. Encapsulated human islet-like cell clusters survived, replicated, and acquired a level of glucose responsive insulin secretion sufficient to ameliorate hyperglycemia in diabetic mice. Bioluminescent imaging of encapsulated murine neonatal islets revealed a dynamic process of cell death followed by regrowth, resulting in robust long-term allograft survival. Further, in the non-obese diabetic (NOD) mouse model of type I diabetes, encapsulated primary beta-cells ameliorated diabetes without stimulating a detectable T-cell response. We demonstrate for the first time that human beta-cells function is compatible with encapsulation in a durable, immunoprotective device. Moreover, our study suggests that encapsulation of beta-cells before terminal differentiation will be a successful approach for new cell-based therapies for diabetes, such as those derived from stem cells.

Insight into the epitaxial encapsulation of Pd catalysts in an oriented metalloporphyrin network thin film for tandem catalysis.

PubMed

Vohra, M Ismail; Li, De-Jing; Gu, Zhi-Gang; Zhang, Jian

2017-06-14

A palladium catalyst (Pd-Cs) encapsulated metalloporphyrin network PIZA-1 thin film with bifunctional properties has been developed through a modified epitaxial layer-by-layer encapsulation approach. Combining the oxidation activity of Pd-Cs and the acetalization activity of the Lewis acidic sites in the PIZA-1 thin film, this bifunctional catalyst of the Pd-Cs@PIZA-1 thin film exhibits a good catalytic activity in a one-pot tandem oxidation-acetalization reaction. Furthermore, the surface components can be controlled by ending the top layer with different precursors in the thin film preparation procedures. The catalytic performances of these thin films with different surface composites were studied under the same conditions, which showed different reaction conversions. The result revealed that the surface component can influence the catalytic performance of the thin films. This epitaxial encapsulation offers a good understanding of the tandem catalysis for thin film materials and provides useful guidance to develop new thin film materials with catalytic properties.

Hydroxypropyl-β-cyclodextrin for Delivery of Baicalin via Inclusion Complexation by Supercritical Fluid Encapsulation.

PubMed

Li, Ying; He, Zhen-Dan; Zheng, Qian-En; Hu, Chengshen; Lai, Wing-Fu

2018-05-14

Over the years, various methods have been developed to enhance the solubility of insoluble drugs; however, most of these methods are time-consuming and labor intensive or involve the use of toxic materials. A method that can safely and effectively enhance the solubility of insoluble drugs is lacking. This study adopted baicalin as an insoluble drug model, and used hydroxypropyl-β-cyclodextrin for the delivery of baicalin via the inclusion complexation by supercritical fluid encapsulation. Different parameters for the complex preparation as well as the physicochemical properties of the complex have been investigated. Our results showed that when compared to the conventional solution mixing approach, supercritical fluid encapsulation enables a more precise control of the properties of the complex, and gives higher loading and encapsulation efficiency. It is anticipated that our reported method can be useful in enhancing the preparation efficiency of inclusion complexes, and can expand the application potential of insoluble herbal ingredients in treatment development and pharmaceutical formulation.

Tumor homing indocyanine green encapsulated micelles for near infrared and photoacoustic imaging of tumors.

PubMed

Uthaman, Saji; Bom, Joon-suk; Kim, Hyeon Sik; John, Johnson V; Bom, Hee-Seung; Kim, Seon-Jong; Min, Jung-Joon; Kim, Il; Park, In-Kyu

2016-05-01

Photoacoustic imaging (PAI) is an emerging analytical modality that is under intense preclinical development for the early diagnosis of various medical conditions, including cancer. However, the lack of specific tumor targeting by various contrast agents used in PAI obstructs its clinical applications. In this study, we developed indocyanine green (ICG)-encapsulated micelles specific for the CD 44 receptor and used in near infrared and photoacoustic imaging of tumors. ICG was hydrophobically modified prior to loading into hyaluronic acid (HA)-based micelles utilized for CD 44 based-targeting. We investigated the physicochemical characteristics of prepared HA only and ICG-encapsulated HA micelles (HA-ICG micelles). After intravenous injection of tumor-bearing mice, the bio-distribution and in vivo photoacoustic images of ICG-encapsulated HA micelles accumulating in tumors were also investigated. Our study further encourages the application of this HA-ICG-based nano-platform as a tumor-specific contrast agent for PAI. © 2016 Wiley Periodicals, Inc.

Development of double emulsion nanoparticles for the encapsulation of bovine serum albumin.

PubMed

Martinez, Nelida Y; Andrade, Patricia F; Durán, Nelson; Cavalitto, Sebastian

2017-10-01

In the present work, a double emulsion was developed for the encapsulation of Bovine Serum Albumin (BSA) as a model protein for the future encapsulation of viral proteins. The first emulsion polydispersity index (PDI) was studied with increasing concentrations of poly (ε-caprolactone) (PCL) as stabilizer (from 16% w/v to 5% w/v) and polyvinyl alcohol (PVA) as the surfactant in the second emulsion at 1.5% w/v. Results suggest that at decreasing concentrations of PCL the PDI of the emulsion also decrease, indicating that viscosity of the emulsion is crucial in the homogeneity of the resultant size distribution of the nanoparticles. When PVA concentration in the second emulsion was increased from 1.5% w/v to 2.5% w/v the PDI also increased. To study the relationship between the structure of the surfactant in the second emulsion and the resultant BSA encapsulation, emulsions were prepared with Pluronic F68 and PVA both at 1.5% w/v and PCL in the first emulsion at 5% w/v. Results indicated that Pluronic F68 was a better stabilizer because at the same experimental conditions encapsulation of BSA was 1.5 higher than PVA. FTIR studies confirmed the presence of BSA in the nanoparticles. SEM and TEM microscopies showed a size distribution of 300nm-500nm size of nanoparticles. Circular dichroism studies demonstrated that the secondary structure of the protein was conserved after the encapsulation into the nanoparticles. Copyright © 2017 Elsevier B.V. All rights reserved.

Islet and Stem Cell Encapsulation for Clinical Transplantation

PubMed Central

Krishnan, Rahul; Alexander, Michael; Robles, Lourdes; Foster 3rd, Clarence E.; Lakey, Jonathan R.T.

2014-01-01

Over the last decade, improvements in islet isolation techniques have made islet transplantation an option for a certain subset of patients with long-standing diabetes. Although islet transplants have shown improved graft function, adequate function beyond the second year has not yet been demonstrated, and patients still require immunosuppression to prevent rejection. Since allogeneic islet transplants have experienced some success, the next step is to improve graft function while eliminating the need for systemic immunosuppressive therapy. Biomaterial encapsulation offers a strategy to avoid the need for toxic immunosuppression while increasing the chances of graft function and survival. Encapsulation entails coating cells or tissue in a semipermeable biocompatible material that allows for the passage of nutrients, oxygen, and hormones while blocking immune cells and regulatory substances from recognizing and destroying the cell, thus avoiding the need for systemic immunosuppressive therapy. Despite advances in encapsulation technology, these developments have not yet been meaningfully translated into clinical islet transplantation, for which several factors are to blame, including graft hypoxia, host inflammatory response, fibrosis, improper choice of biomaterial type, lack of standard guidelines, and post-transplantation device failure. Several new approaches, such as the use of porcine islets, stem cells, development of prevascularized implants, islet nanocoating, and multilayer encapsulation, continue to generate intense scientific interest in this rapidly expanding field. This review provides a comprehensive update on islet and stem cell encapsulation as a treatment modality in type 1 diabetes, including a historical outlook as well as current and future research avenues. PMID:25148368

Encapsulation of Autoinducer Sensing Reporter Bacteria in Reinforced Alginate-Based Microbeads.

PubMed

Li, Ping; Müller, Mareike; Chang, Matthew Wook; Frettlöh, Martin; Schönherr, Holger

2017-07-12

Quorum sensing, in which bacteria communities use signaling molecules for inter- and intracellular communication, has been intensively studied in recent decades. In order to fabricate highly sensitive easy-to-handle point of care biosensors that detect quorum sensing molecules, we have developed, as is reported here, reporter bacteria loaded alginate-methacrylate (alginate-MA) hydrogel beads. The alginate-MA beads, which were obtained by electrostatic extrusion, were reinforced by photo-cross-linking to increase stability and thereby to reduce bacteria leaching. In these beads the genetically engineered fluorescent reporter bacterium Escherichia coli pTetR-LasR-pLuxR-GFP (E. coli pLuxR-GFP) was encapsulated, which responds to the autoinducer N-(3-oxododecanoyl)homoserine lactone secreted by Pseudomonas aeruginosa. After encapsulation in alginate-MA hydrogel beads with diameters in the range of 100-300 μm that were produced by an electrostatic extrusion method and rapid photo-cross-linking, the E. coli pLuxR-GFP were found to possess a high degree of viability and sensing activity. The encapsulated bacteria could proliferate inside the hydrogel beads, when exposed to bacteria culture medium. In media containing the autoinducer N-(3-oxododecanoyl)homoserine lactone, the encapsulated reporter bacteria responded with a strong fluorescence signal due to an increased green fluorescent protein (GFP) expression. A prototype dipstick type sensor developed here underlines the potential of encapsulation of viable and functional reporter bacteria inside reinforced alginate-methacrylate hydrogel beads for whole cell sensors for bacteria detection.

RGD peptide-modified multifunctional dendrimer platform for drug encapsulation and targeted inhibition of cancer cells.

PubMed

He, Xuedan; Alves, Carla S; Oliveira, Nilsa; Rodrigues, João; Zhu, Jingyi; Bányai, István; Tomás, Helena; Shi, Xiangyang

2015-01-01

Development of multifunctional nanoscale drug-delivery systems for targeted cancer therapy still remains a great challenge. Here, we report the synthesis of cyclic arginine-glycine-aspartic acid (RGD) peptide-conjugated generation 5 (G5) poly(amidoamine) dendrimers for anticancer drug encapsulation and targeted therapy of cancer cells overexpressing αvβ3 integrins. In this study, amine-terminated G5 dendrimers were used as a platform to be sequentially modified with fluorescein isothiocyanate (FI) via a thiourea linkage and RGD peptide via a polyethylene glycol (PEG) spacer, followed by acetylation of the remaining dendrimer terminal amines. The developed multifunctional dendrimer platform (G5.NHAc-FI-PEG-RGD) was then used to encapsulate an anticancer drug doxorubicin (DOX). We show that approximately six DOX molecules are able to be encapsulated within each dendrimer platform. The formed complexes are water-soluble, stable, and able to release DOX in a sustained manner. One- and two-dimensional NMR techniques were applied to investigate the interaction between dendrimers and DOX, and the impact of the environmental pH on the release rate of DOX from the dendrimer/DOX complexes was also explored. Furthermore, cell biological studies demonstrate that the encapsulation of DOX within the G5.NHAc-FI-PEG-RGD dendrimers does not compromise the anticancer activity of DOX and that the therapeutic efficacy of the dendrimer/DOX complexes is solely related to the encapsulated DOX drug. Importantly, thanks to the role played by RGD-mediated targeting, the developed dendrimer/drug complexes are able to specifically target αvβ3 integrin-overexpressing cancer cells and display specific therapeutic efficacy to the target cells. The developed RGD peptide-targeted multifunctional dendrimers may thus be used as a versatile platform for targeted therapy of different types of αvβ3 integrin-overexpressing cancer cells. Copyright © 2014 Elsevier B.V. All rights reserved.

Asymmetric bioreduction of acetophenones by Baker's yeast and its cell-free extract encapsulated in sol-gel silica materials

NASA Astrophysics Data System (ADS)

Kato, Katsuya; Nakamura, Hitomi; Nakanishi, Kazuma

2014-02-01

Baker's yeast (BY) encapsulated in silica materials was synthesized using a yeast cell suspension and its cell-free extract during a sol-gel reaction of tetramethoxysilane with nitric acid as a catalyst. The synthesized samples were fully characterized using various methods, such as scanning electron microscopy, nitrogen adsorption-desorption, Fourier transform infrared spectroscopy, thermogravimetry, and differential thermal analysis. The BY cells were easily encapsulated inside silica-gel networks, and the ratio of the cells in the silica gel was approximately 75 wt%, which indicated that a large volume of BY was trapped with a small amount of silica. The enzyme activity (asymmetric reduction of prochiral ketones) of BY and its cell-free extract encapsulated in silica gel was investigated in detail. The activities and enantioselectivities of free and encapsulated BY were similar to those of acetophenone and its fluorine derivatives, which indicated that the conformation structure of BY enzymes inside silica-gel networks did not change. In addition, the encapsulated BY exhibited considerably better solvent (methanol) stability and recyclability compared to free BY solution. We expect that the development of BY encapsulated in sol-gel silica materials will significantly impact the industrial-scale advancement of high-efficiency and low-cost biocatalysts for the synthesis of valuable chiral alcohols.

Droplet sorting based on the number of encapsulated particles using a solenoid valve.

PubMed

Cao, Zhenning; Chen, Fangyuan; Bao, Ning; He, Huacheng; Xu, Peisheng; Jana, Saikat; Jung, Sunghwan; Lian, Hongzhen; Lu, Chang

2013-01-07

Droplet microfluidics provides a high-throughput platform for screening subjects and conditions involved in biology. Droplets with encapsulated beads and cells have been increasingly used for studying molecular and cellular biology. Droplet sorting is needed to isolate and analyze the subject of interest during such screening. The vast majority of current sorting techniques use fluorescence intensity emitted by each droplet as the only criterion. However, due to the randomness and imperfections in the encapsulation process, typically a mixed population of droplets with an uneven number of encapsulated particles results and is used for screening. Thus droplet sorting based on the number of encapsulated particles becomes necessary for isolating or enriching droplets with a specific occupancy. In this work, we developed a fluorescence-activated microfluidic droplet sorter that integrated a simple deflection mechanism based on the use of a solenoid valve and a sophisticated signal processing system with a microcontroller as the core. By passing droplets through a narrow interrogation channel, the encapsulated particles were detected individually. The microcontroller conducted the computation to determine the number of encapsulated particles in each droplet and made the sorting decision accordingly that led to actuation of the solenoid valve. We tested both fluorescent beads and stained cells and our results showed high efficiency and accuracy for sorting and enrichment.

Effect of Coating Method on the Survival Rate of L. plantarum for Chicken Feed

PubMed Central

Lee, Sang-Yoon; Jo, Yeon-Ji; Choi, Mi-Jung; Lee, Boo-Yong; Han, Jong-Kwon; Lim, Jae Kag

2014-01-01

This study was designed to find the most suitable method and wall material for microencapsulation of the Lactobacillus plantarum to maintain cell viability in different environmental conditions. To improve the stability of L. plantarum, we developed an encapsulation system of L. plantarum, using water-in-oil emulsion system. For the encapsulation of L. plantarum, corn starch and glyceryl monostearate were selected to form gel beads. Then 10% (w/v) of starch was gelatinized by autoclaving to transit gel state, and cooled down at 60ºC and mixed with L. plantarum to encapsulate it. The encapsulated L. plantarum was tested for the tolerance of acidic conditions at different temperatures to investigate the encapsulation ability. The study indicated that the survival rate of the microencapsulated cells in starch matrix was significantly higher than that of free cells in low pH conditions with relatively higher temperature. The results showed that corn starch as a wall material and glycerol monostearate as a gelling agent in encapsulation could play a role in the viability of lactic acid bacteria in extreme conditions. Using the current study, it would be possible to formulate a new water-in-oil system as applied in the protection of L. plantarum from the gastric conditions for the encapsulation system used in chicken feed industry. PMID:26760943

Do encapsulated heat storage materials really retain their original thermal properties?

PubMed

Chaiyasat, Preeyaporn; Noppalit, Sayrung; Okubo, Masayoshi; Chaiyasat, Amorn

2015-01-14

The encapsulation of Rubitherm®27 (RT27), which is one of the most common commercially supplied heat storage materials, by polystyrene (PS), polydivinyl benzene (PDVB) and polymethyl methacrylate (PMMA) was carried out using conventional radical microsuspension polymerization. The products were purified to remove free RT27 and free polymer particles without RT27. In the cases of PS and PDVB microcapsules, the latent heats of melting and crystallization for RT27 ( and , J/g-RT27) were clearly decreased by the encapsulation. On the other hand, those of the PMMA microcapsules were the same as pure RT27. A supercooling phenomenon was observed not only for PS and PDVB but also for the PMMA microcapsules. These results indicate that the thermal properties of the heat storage materials encapsulated depend on the type of polymer shells, i.e., encapsulation by polymer shell changes the thermal properties of RT27. This is quite different from the idea of other groups in the world, in which they discussed the thermal properties based on the ΔHm and ΔHc values expressed in J/g-capsule, assuming that the thermal properties of the heat storage materials are not changed by the encapsulation. Hereafter, this report should raise an alarm concerning the "wrong" common knowledge behind developing the encapsulation technology of heat storage materials.

Fixed distance photoinduced electron transfer between Fe and Zn porphyrins encapsulated within the Zn HKUST-1 metal organic framework.

PubMed

Larsen, Randy W; Wojtas, Lukasz

2015-02-21

An attractive strategy for the development of photocatalytic metal organic framework (MOF) materials is to co-encapsulate a photoactive electron donor with a catalytic electron acceptor within the MOF. Here we report the co-encapsulation of both Zn(ii) tetrakis(tetra 4-sulphonatophenyl)porphyrin (Zn4SP) and Fe(iii) tetrakis(tetra 4-sulphonatophenyl)porphyrin (Fe4SP) into an HKUST-1 (Zn) MOF and demonstrate photoinduced electron transfer (ET) between the co-encapsulated guest. Photo-excitation of the Zn4SP results in fixed-distance inter-molecular ET between the encapsulated (3)Zn4SP and the Fe(iii)4SP as evident by the reduction in the encapsulated (3)Zn4SP lifetime from 890 μs (kobs = 1.1 × 10(3) s(-1)) to 83 μs (kobs = 1.2 × 10(4) s(-1)) in the presence of Fe4SP giving a kET ∼ 1.1 × 10(4) s(-1). The data are consistent with ET taking place between encapsulated porphyrins that are two cages apart in distance with a reorganizational energy of ∼1.65 eV, β = 1.25 and ΔG° = -0.97 eV (within a semi-classical Marcus theory framework).

Silica sol-gel encapsulation of cyanobacteria: lessons for academic and applied research.

PubMed

Dickson, David J; Ely, Roger L

2013-03-01

Cyanobacteria inhabit nearly every ecosystem on earth, play a vital role in nutrient cycling, and are useful as model organisms for fundamental research in photosynthesis and carbon and nitrogen fixation. In addition, they are important for several established biotechnologies for producing food additives, nutritional and pharmaceutical compounds, and pigments, as well as emerging biotechnologies for biofuels and other products. Encapsulation of living cyanobacteria into a porous silica gel matrix is a recent approach that may dramatically improve the efficiency of certain production processes by retaining the biomass within the reactor and modifying cellular metabolism in helpful ways. Although encapsulation has been explored empirically in the last two decades for a variety of cell types, many challenges remain to achieving optimal encapsulation of cyanobacteria in silica gel. Recent evidence with Synechocystis sp. PCC 6803, for example, suggests that several unknown or uncharacterized proteins are dramatically upregulated as a result of encapsulation. Also, additives commonly used to ease stresses of encapsulating living cells, such as glycerol, have detrimental impacts on photosynthesis in cyanobacteria. This mini-review is intended to address the current status of research on silica sol-gel encapsulation of cyanobacteria and research areas that may further the development of this approach for biotechnology applications.

Silicon in broiler drinking water promotes bone development in broiler chickens.

PubMed

Sgavioli, S; de Faria Domingues, C H; Castiblanco, D M C; Praes, M F F M; Andrade-Garcia, Giuliana M; Santos, E T; Baraldi-Artoni, S M; Garcia, R G; Junqueira, O M

2016-10-01

Skeletal abnormalities, bone deformities and fractures cause significant losses in broiler production during both rearing and processing. Silicon is an essential mineral for bone and connective tissue synthesis and for calcium absorption during the early stages of bone formation. Performance was not affected by the addition of silicon. However, broilers receiving silicon showed a significant increase of phosphorus, zinc, copper, manganese and ash in the tibia. In conclusion, broiler performance was not impaired by adding the tested silicon product to the drinking water. In addition, bone development improved, as demonstrated by higher mineral and ash content. Further studies are required to determine the optimal concentration of silicon, including heat stress simulations, to better understand the effects of silicon on bone development.

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

Holley, W A

This report describes work performed under a subcontract to the National Renewable Energy Laboratory under the Photovoltaic Manufacturing Technology Project. The objectives of this subcontract are to (1) define the problem of yellowing/browning of EVA-based encapsulants; (2) determine probable mechanisms and the role of various parameters such as heat, UV exposure, module construction, EVA interfaces, and EVA thickness, in the browning of EVA-based encapsulants; (3) develop stabilization strategies for various module constructions to protect the encapsulant from degradative failure; (4) conduct laboratory, accelerated outdoor, and field testing of encapsulant, laminated test coupons, and full modules to demonstrate the functional adequacymore » of the stabilization strategies; and (5) implement these strategies. This report summarizes the accomplishments related to the above goals for the reporting period.« less

The U.S. and Japanese amorphous silicon technology programs A comparison

NASA Technical Reports Server (NTRS)

Shimada, K.

1984-01-01

The U.S. Department of Energy/Solar Energy Research Institute Amorphous Silicon (a-Si) Solar Cell Program performs R&D on thin-film hydrogenated amorphous silicon for eventual development of stable amorphous silicon cells with 12 percent efficiency by 1988. The Amorphous Silicon Solar Cell Program in Japan is sponsored by the Sunshine Project to develop an alternate energy technology. While the objectives of both programs are to eventually develop a-Si photovoltaic modules and arrays that would produce electricity to compete with utility electricity cost, the U.S. program approach is research oriented and the Japanese is development oriented.

Waste management technology development and demonstration programs at Brookhaven National Laboratory

NASA Technical Reports Server (NTRS)

Kalb, Paul D.; Colombo, Peter

1991-01-01

Two thermoplastic processes for improved treatment of radioactive, hazardous, and mixed wastes were developed from bench scale through technology demonstration: polyethylene encapsulation and modified sulfur cement encapsulation. The steps required to bring technologies from the research and development stage through full scale implementation are described. Both systems result in durable waste forms that meet current Nuclear Regulatory Commission and Environmental Protection Agency regulatory criteria and provide significant improvements over conventional solidification systems such as hydraulic cement. For example, the polyethylene process can encapsulate up to 70 wt pct. nitrate salt, compared with a maximum of about 20 wt pct. for the best hydraulic cement formulation. Modified sulfur cement waste forms containing as much as 43 wt pct. incinerator fly ash were formulated, whereas the maximum quantity of this waste in hydraulic cement is 16 wt pct.

Mn@Si14+: a singlet fullerene-like endohedrally doped silicon cluster.

PubMed

Ngan, Vu Thi; Pierloot, Kristine; Nguyen, Minh Tho

2013-04-21

The electronic structure of Mn@Si14(+) is determined using DFT and CASPT2/CASSCF(14,15) computations with large basis sets. The endohedrally Mn-doped Si cationic cluster has a D3h fullerene-like structure featuring a closed-shell singlet ground state with a singlet-triplet gap of ~1 eV. A strong stabilizing interaction occurs between the 3d(Mn) and the 2D-shell(Si14) orbitals, and a large amount of charge is transferred from the Si14 cage to the Mn dopant. The 3d(Mn) orbitals are filled by encapsulation, and the magnetic moment of Mn is completely quenched. Full occupation of [2S, 2P, 2D] shell orbitals by 18 delocalized electrons confers the doped Mn@Si14(+) cluster a spherically aromatic character.

Injection molding of high precision optics for LED applications made of liquid silicone rubber

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

Hopmann, Christian; Röbig, Malte

Light Emitting Diodes (LED) conquer the growing global market of lighting technologies. Due to their advantages, they are increasingly used in consumer products, in lighting applications in the home and in the mobility sector as well as in industrial applications. Particularly, with regard to the increasing use of high-power LED (HP-LED) the materials in the surrounding area of the light emitting semiconductor chip are of utmost importance. While the materials behind the semiconductor chip are optimized for maximum heat dissipation, the materials currently used for the encapsulation of the semiconductor chip (primary optics) and the secondary optics encounter their limitsmore » due to the high temperatures. In addition certain amounts of blue UV radiation degrade the currently used materials such as epoxy resins or polyurethanes for primary optics. In the context of an ongoing joint research project with various partners from the industry, an innovative manufacturing method for high precision optics for LED applications made of liquid silicone rubber (LSR) is analyzed at the Institut of Plastics Processing (IKV), Aachen. The aim of this project is to utilize the material-specific advantages of high transparent LSR, especially the excellent high temperature resistance and the great freedom in design. Therefore, a high integrated injection molding process is developed. For the production of combined LED primary and secondary optics a LED board is placed in an injection mold and overmolded with LSR. Due to the integrated process and the reduction of subcomponents like the secondary optics the economics of the production process can be improved significantly. Furthermore combined LED optics offer an improved effectiveness, because there are no losses of the light power at the transition of the primary and secondary optics.« less

Aerosolized liposomes with dipalmitoyl phosphatidylcholine enhance pulmonary absorption of encapsulated insulin compared with co-administered insulin.

PubMed

Chono, Sumio; Togami, Kohei; Itagaki, Shirou

2017-11-01

We have previously shown that aerosolized liposomes with dipalmitoyl phosphatidylcholine (DPPC) enhance the pulmonary absorption of encapsulated insulin. In this study, we aimed to compare insulin encapsulated into the liposomes versus co-administration of empty liposomes and unencapsulated free insulin, where the DPCC liposomes would serve as absorption enhancer. The present study provides the useful information for development of noninvasive treatment of diabetes. Co-administration of empty DPPC liposomes and unencapsulated free insulin was investigated in vivo to assess the potential enhancement in protein pulmonary absorption. Co-administration was compared to DPPC liposomes encapsulating insulin, and free insulin. DPPC liposomes enhanced the pulmonary absorption of unencapsulated free insulin; however, the enhancing effect was lower than that of the DPPC liposomes encapsulating insulin. The mechanism of the pulmonary absorption of unencapsulated free insulin by DPPC liposomes involved the opening of epithelial cell space in alveolar mucosa, and not mucosal cell damage, similar to that of the DPPC liposomes encapsulating insulin. In an in vitro stability test, insulin in the alveolar mucus layer that covers epithelial cells was stable. These findings suggest that, although unencapsulated free insulin spreads throughout the alveolar mucus layer, the concentration of insulin released near the absorption surface is increased by the encapsulation of insulin into DPPC liposomes and the absorption efficiency is also increased. We revealed that the encapsulation of insulin into DPPC liposomes is more effective for pulmonary insulin absorption than co-administration of DPPC liposomes and unencapsulated free insulin.

Optimization of NMR spectroscopy of encapsulated proteins dissolved in low viscosity fluids

PubMed Central

Nucci, Nathaniel V.; Marques, Bryan S.; Bédard, Sabrina; Dogan, Jakob; Gledhill, John M.; Moorman, Veronica R.; Peterson, Ronald W.; Valentine, Kathleen G.; Wand, Alison L.; Wand, A. Joshua

2014-01-01

Comprehensive application of solution NMR spectroscopy to studies of macromolecules remains fundamentally limited by the molecular rotational correlation time. For proteins, molecules larger than 30 kDa require complex experimental methods, such as TROSY in conjunction with isotopic labeling schemes that are often expensive and generally reduce the potential information available. We have developed the reverse micelle encapsulation strategy as an alternative approach. Encapsulation of proteins within the protective nano-scale water pool of a reverse micelle dissolved in ultra-low viscosity nonpolar solvents overcomes the slow tumbling problem presented by large proteins. Here, we characterize the contributions from the various components of the protein-containing reverse micelle system to the rotational correlation time of the encapsulated protein. Importantly, we demonstrate that the protein encapsulated in the reverse micelle maintains a hydration shell comparable in size to that seen in bulk solution. Using moderate pressures, encapsulation in ultra-low viscosity propane or ethane can be used to magnify this advantage. We show that encapsulation in liquid ethane can be used to reduce the tumbling time of the 43 kDa maltose binding protein from ~23 ns to ~10 ns. These conditions enable, for example, acquisition of TOCSY-type data resolved on the adjacent amide NH for the 42 kDa encapsulated maltose binding protein dissolved in liquid ethane, which is typically impossible for proteins of such size without use of extensive deuteration or the TROSY effect. PMID:21748265

Near-Infrared Squaraine Dye Encapsulated Micelles for in Vivo Fluorescence and Photoacoustic Bimodal Imaging.

PubMed

Sreejith, Sivaramapanicker; Joseph, James; Lin, Manjing; Menon, Nishanth Venugopal; Borah, Parijat; Ng, Hao Jun; Loong, Yun Xian; Kang, Yuejun; Yu, Sidney Wing-Kwong; Zhao, Yanli

2015-06-23

Combined near-infrared (NIR) fluorescence and photoacoustic imaging techniques present promising capabilities for noninvasive visualization of biological structures. Development of bimodal noninvasive optical imaging approaches by combining NIR fluorescence and photoacoustic tomography demands suitable NIR-active exogenous contrast agents. If the aggregation and photobleaching are prevented, squaraine dyes are ideal candidates for fluorescence and photoacoustic imaging. Herein, we report rational selection, preparation, and micelle encapsulation of an NIR-absorbing squaraine dye (D1) for in vivo fluorescence and photoacoustic bimodal imaging. D1 was encapsulated inside micelles constructed from a biocompatible nonionic surfactant (Pluoronic F-127) to obtain D1-encapsulated micelles (D1(micelle)) in aqueous conditions. The micelle encapsulation retains both the photophysical features and chemical stability of D1. D1(micelle) exhibits high photostability and low cytotoxicity in biological conditions. Unique properties of D1(micelle) in the NIR window of 800-900 nm enable the development of a squaraine-based exogenous contrast agent for fluorescence and photoacoustic bimodal imaging above 820 nm. In vivo imaging using D1(micelle), as demonstrated by fluorescence and photoacoustic tomography experiments in live mice, shows contrast-enhanced deep tissue imaging capability. The usage of D1(micelle) proven by preclinical experiments in rodents reveals its excellent applicability for NIR fluorescence and photoacoustic bimodal imaging.

Nano spray drying for encapsulation of pharmaceuticals.

PubMed

Arpagaus, Cordin; Collenberg, Andreas; Rütti, David; Assadpour, Elham; Jafari, Seid Mahdi

2018-05-17

Many pharmaceuticals such as pills, capsules, or tablets are prepared in a dried and powdered form. In this field, spray drying plays a critical role to convert liquid pharmaceutical formulations into powders. In addition, in many cases it is necessary to encapsulate bioactive drugs into wall materials to protect them against harsh process and environmental conditions, as well as to deliver the drug to the right place and at the correct time within the body. Thus, spray drying is a common process used for encapsulation of pharmaceuticals. In view of the rapid progress of nanoencapsulation techniques in pharmaceutics, nano spray drying is used to improve drug formulation and delivery. The nano spray dryer developed in the recent years provides ultrafine powders at nanoscale and high product yields. In this paper, after explaining the concept of nano spray drying and understanding the key elements of the equipment, the influence of the process parameters on the final powders properties, like particle size, morphology, encapsulation efficiency, drug loading and release, will be discussed. Then, numerous application examples are reviewed for nano spray drying and encapsulation of various drugs in the early stages of product development along with a brief overview of the obtained results and characterization techniques. Copyright © 2018 Elsevier B.V. All rights reserved.

Development and physico-chemical characterization of cyclodextrin DNA complexes loaded liposomes

NASA Astrophysics Data System (ADS)

Tavares, Guilherme D.; Viana, Cristiane M.; Araújo, José G. V. C.; Ramaldes, Gilson A.; Carvalho, Wânia S.; Pesquero, Jorge L.; Vilela, José M. C.; Andrade, Margareth S.; de Oliveira, Mônica C.

2006-10-01

In the present study, anionic and pH-sensitive liposomes containing DNA were developed and characterized. These liposomes were obtained by binding the DNA with 6-monodeoxy-6-monoamine-β-cyclodextrin (Am-β-CD). This complex was encapsulated into the liposomes, which were characterized by encapsulation rate, diameter, zeta potential, and atomic force microscopy. The binding between Am-β-CD and the DNA was higher as of the +/- charge ratio. The amount of DNA encapsulated was approximately 10-14 μg/mL. The mean diameter and zeta potential were 186.0 nm and -56 mV, respectively. Liposomes which did not contain the complex were more prone to collapse over the mica surface. The vesicles containing the complex presented a narrower size distribution.

Design and evaluation of an oral multiparticulate system for dual delivery of amoxicillin and Lactobacillus acidophilus.

PubMed

Govender, Mershen; Choonara, Yahya E; van Vuuren, Sandy; Kumar, Pradeep; du Toit, Lisa C; Pillay, Viness

2016-09-01

A delayed-release dual delivery system for amoxicillin and the probiotic Lactobacillus acidophilus was developed and evaluated. Statistical optimization of a cross-linked denatured ovalbumin protective matrix was first synthesized using a Box-Behnken experimental design prior to encapsulation with glyceryl monostereate. The encapsulated ovalbumin matrix was thereafter incorporated with amoxicillin in a gastro-resistant capsule. In vitro characterization and stability analysis of the ovalbumin and encapsulated components were also performed Results: Protection of L. acidophilus probiotic against the bactericidal effects of amoxicillin within the dual formulation was determined. The dual formulation in this study proved effective and provides insight into current microbiome research to identify, classify and use functional healthy bacteria to develop novel probiotic delivery technologies.

Silicon coupled with plasmon nanocavities generates bright visible hot luminescence

NASA Astrophysics Data System (ADS)

Cho, Chang-Hee; Aspetti, Carlos O.; Park, Joohee; Agarwal, Ritesh

2013-04-01

To address the limitations in device speed and performance in silicon-based electronics, there have been extensive studies on silicon optoelectronics with a view to achieving ultrafast optical data processing. The biggest challenge has been to develop an efficient silicon-based light source, because the indirect bandgap of silicon gives rise to extremely low emission efficiencies. Although light emission in quantum-confined silicon at sub-10 nm length scales has been demonstrated, there are difficulties in integrating quantum structures with conventional electronics. It is desirable to develop new concepts to obtain emission from silicon at length scales compatible with current electronic devices (20-100 nm), which therefore do not utilize quantum-confinement effects. Here, we demonstrate an entirely new method to achieve bright visible light emission in `bulk-sized' silicon coupled with plasmon nanocavities at room temperature, from non-thermalized carrier recombination. The highly enhanced emission (internal quantum efficiency of >1%) in plasmonic silicon, together with its size compatibility with current silicon electronics, provides new avenues for developing monolithically integrated light sources on conventional microchips.

Aerospace Sensor Component and Subsystem Investigation and Innovation-2 Component Exploration and Development (ASCSII-2 CED) Delivery Order 0003: Hermetically Sealed Cavities in 3-D GaAs-Silicon and Silicon-Silicon Packages for Microelectromechanical System (MEMS) Devices Using Selective and Large-Scale Bonding

DTIC Science & Technology

2003-03-01

and silicon-to-silicon to produce cavities for 3-D assembly of MEMS devices has been demonstrated using SnAgCu and eutectic SnPb solders. Laser and...of GaAs-to-silicon and silicon-to-silicon to produce cavities for 3-D assembly of MEMS devices has been demonstrated using SnAgCu and euctectic...research_images/ 3.2 Solder Reflow The reflow profile for SnAgCu solder was developed on the Sikama convection/ conduction reflow oven using a continuous

A novel approach to fabricate dye-encapsulated polymeric micro- and nanoparticles by thin film dewetting technique.

PubMed

Chatterjee, Manosree; Hens, Abhiram; Mahato, Kuldeep; Jaiswal, Namita; Mahato, Nivedita; Nagahanumaiah; Chanda, Nripen

2017-11-15

A new method is reported for fabrication of polymeric micro- and nanoparticles from an intermediate patterned surface originated by dewetting of a polymeric thin film. Poly (d, l-lactide-co-glycolide) or PLGA, a biocompatible polymer is used to develop a thin film over a clean glass substrate which dewets spontaneously in the micro-/nano-patterned surface of size range 50nm to 3.5µm. Since another water-soluble polymer, poly vinyl alcohol (PVA) is coated on the same glass substrate before PLGA thin film formation, developed micro-/nano-patterns are easily extracted in water in the form of micro- and nanoparticle mixture of size range 50nm to 3.0µm. This simplified method is also used to effectively encapsulate a dye molecule, rhodamine B inside the PLGA micro-/nanoparticles. The developed dye-encapsulated nanoparticles, PLGA-rhodamine are separated from the mixture and tested for in-vitro delivery application of external molecules inside human lung cancer cells. For the first time, the use of thin film dewetting technique is reported as a potential route for the synthesis of polymeric micro-/nanoparticles and effective encapsulation of external species therein. Copyright © 2017 Elsevier Inc. All rights reserved.

Flat-plate solar array project: Experimental process system development unit for producing semiconductor-grade silicon using the silane-to-silicon process

NASA Technical Reports Server (NTRS)

1981-01-01

The engineering design, fabrication, assembly, operation, economic analysis, and process support research and development for an Experimental Process System Development Unit for producing semiconductor-grade silicon using the slane-to-silicon process are reported. The design activity was completed. About 95% of purchased equipment was received. The draft of the operations manual was about 50% complete and the design of the free-space system continued. The system using silicon power transfer, melting, and shotting on a psuedocontinuous basis was demonstrated.

Encapsulation Processing and Manufacturing Yield Analysis

NASA Technical Reports Server (NTRS)

Willis, P. B.

1984-01-01

The development of encapsulation processing and a manufacturing productivity analysis for photovoltaic cells are discussed. The goals were: (1) to understand the relationships between both formulation variables and process variables; (2) to define conditions required for optimum performance; (3) to predict manufacturing yield; and (4) to provide documentation to industry.

Encapsulation processing and manufacturing yield analysis

NASA Astrophysics Data System (ADS)

Willis, P. B.

1984-10-01

The development of encapsulation processing and a manufacturing productivity analysis for photovoltaic cells are discussed. The goals were: (1) to understand the relationships between both formulation variables and process variables; (2) to define conditions required for optimum performance; (3) to predict manufacturing yield; and (4) to provide documentation to industry.

Human β-cell Precursors Mature Into Functional Insulin-producing Cells in an Immunoisolation Device: Implications for Diabetes Cell Therapies

PubMed Central

Lee, Seung-Hee; Hao, Ergeng; Savinov, Alexei Y.; Geron, Ifat; Strongin, Alex Y.; Itkin-Ansari, Pamela

2009-01-01

Background Islet transplantation is limited by the need for chronic immunosuppression and the paucity of donor tissue. As new sources of human β-cells are developed (e.g., stem cell-derived tissue), transplanting them in a durable device could obviate the need for immunosuppression, while also protecting the patient from any risk of tumorigenicity. Here, we studied (1) the survival and function of encapsulated human β-cells and their progenitors and (2) the engraftment of encapsulated murine β-cells in allo- and autoimmune settings. Methods Human islets and human fetal pancreatic islet-like cell clusters were encapsulated in polytetrafluorethylene devices (TheraCyte) and transplanted into immunodeficient mice. Graft survival and function was measured by immunohistochemistry, circulating human C-peptide levels, and blood glucose levels. Bioluminescent imaging was used to monitor encapsulated neonatal murine islets. Results Encapsulated human islet-like cell clusters survived, replicated, and acquired a level of glucose responsive insulin secretion sufficient to ameliorate hyperglycemia in diabetic mice. Bioluminescent imaging of encapsulated murine neonatal islets revealed a dynamic process of cell death followed by regrowth, resulting in robust long-term allograft survival. Further, in the non-obese diabetic (NOD) mouse model of type I diabetes, encapsulated primary β-cells ameliorated diabetes without stimulating a detectable T-cell response. Conclusions We demonstrate for the first time that human β-cells function is compatible with encapsulation in a durable, immunoprotective device. Moreover, our study suggests that encapsulation of β-cells before terminal differentiation will be a successful approach for new cell-based therapies for diabetes, such as those derived from stem cells. PMID:19352116

Dynamics of encapsulated microbubbles for contrast ultrasound imaging and drug delivery: from pressure dependent subharmonic to collapsing jet and acoustic streaming

NASA Astrophysics Data System (ADS)

Sarkar, Kausik

2016-11-01

Intravenously injected microbubbles used as ultrasound contrast enhancing agents are encapsulated by a nanometer-thick layer of lipids, proteins or polymers to stabilize them against premature dissolution. Over the years, we have developed interfacial rheological models for the encapsulation and used them to characterize several contrast agents by acoustic means. We will present an overview of our research emphasizing recent efforts in two directions. The first is on using subharmonic signals from the contrast microbubbles for non-invasive pressure estimation. Experimental measurement and modeling show that the subharmonic signal can both increase or decrease with pressure depending on frequency. Secondly, we will discuss boundary element (BEM) simulation of the collapse of an encapsulated microbubbles forming a jet near a blood vessel wall. Different rheology models of the encapsulation have been rigorously implemented in the BEM formulation. We will discuss the resulting stresses and the acoustic streaming near the wall leading to sonoporation and other bioeffects. Partially supported by Natinal Science Foundation.

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

Lutwack, R.

The goal of the Silicon Material Task, a part of the FSA Project, was to develop and demonstrate the technology for the low-cost production of silicon of suitable purity to be used as the basic material for the manufacture of terrestrial photovoltaic solar cells. To be compatible with the price goals of the FSA Project, the price of the produced silicon was to be less than $10/kg (in 1975 dollars). Summarized in this document are 11 different processes for the production of silicon that were investigated and developed to varying extent by industrial, university, and government researchers. The silane-production sectionmore » of the Union Carbide Corp. (UCC) silane process was developed completely in this program. Coupled with Siemens-type chemical vapor deposition reactors, the process was carried through the pilot plant stage. The overall UCC process involves the conversion of metallurgical-grade silicon to silane followed by decomposition of the silane to purified silicon. Production of very high-purity silane and silicon was demonstrated. Although it has as yet not achieved commercial application, the development of fluidized-bed technology for the low-cost, high-throughput conversion of silane-to-silicon has been demonstrated in the research laboratory and now is in engineering development.« less

Encapsulation of Natural Polyphenolic Compounds; a Review

PubMed Central

Munin, Aude; Edwards-Lévy, Florence

2011-01-01

Natural polyphenols are valuable compounds possessing scavenging properties towards radical oxygen species, and complexing properties towards proteins. These abilities make polyphenols interesting for the treatment of various diseases like inflammation or cancer, but also for anti-ageing purposes in cosmetic formulations, or for nutraceutical applications. Unfortunately, these properties are also responsible for a lack in long-term stability, making these natural compounds very sensitive to light and heat. Moreover, polyphenols often present a poor biodisponibility mainly due to low water solubility. Lastly, many of these molecules possess a very astringent and bitter taste, which limits their use in food or in oral medications. To circumvent these drawbacks, delivery systems have been developed, and among them, encapsulation would appear to be a promising approach. Many encapsulation methods are described in the literature, among which some have been successfully applied to plant polyphenols. In this review, after a general presentation of the large chemical family of plant polyphenols and of their main chemical and biological properties, encapsulation processes applied to polyphenols are classified into physical, physico-chemical, chemical methods, and other connected stabilization methods. After a brief description of each encapsulation process, their applications to polyphenol encapsulation for pharmaceutical, food or cosmetological purposes are presented. PMID:24309309

Encapsulation of ferulic acid ethyl ester in caseinate to suppress off-flavor formation in UHT milk.

PubMed

Guan, Yongguang; Zhong, Qixin

2017-12-15

Phenolic compounds can principally suppress the off-flavor development in ultrahigh temperature (UHT) treated milk, but little has been studied for lipophilic phenolic compounds that are to be encapsulated for even distribution in milk. The objective of this work was to study physicochemical properties of ferulic acid ethyl ester (FAEE) encapsulated in sodium caseinate and the inhibition of volatile formation after UHT processing. The capsules had an average hydrodynamic diameter of 246.2±10.9nm, a polydispersity index of 0.26±0.01, and a zeta-potential of -31.72±0.74mV. The capsules and the encapsulated FAEE were stable after heating at 138°C for 16min and UV radiation at 365nm for 32h. The encapsulated FAEE at a level of 0.18-1.42mg/mL suppressed the formation of 2-acetyl-2-thiazoline in model UHT milk by 32.8-63.2% after 30-day storage at 30°C. Therefore, FAEE encapsulated in caseinate can be potentially used to improve the quality of UHT milk. Copyright © 2017 Elsevier Ltd. All rights reserved.

Flat-plate solar array project. Volume 2: Silicon material

NASA Technical Reports Server (NTRS)

Lutwack, R.

1986-01-01

The goal of the Silicon Material Task, a part of the Flat Plate Solar Array (FSA) Project, was to develop and demonstate the technology for the low cost production of silicon of suitable purity to be used as the basic material for the manufacture of terrestrial photovoltaic solar cells. Summarized are 11 different processes for the production of silicon that were investigated and developed to varying extent by industrial, university, and Government researchers. The silane production section of the Union Carbide Corp. (UCC) silane process was developed completely in this program. Coupled with Siemens-type chemical vapor deposition reactors, the process was carried through the pilot stage. The overall UCC process involves the conversion of metallurgical-grade silicon to silane followed by decomposition of the silane to purified silicon. The other process developments are described to varying extents. Studies are reported on the effects of impurities in silicon on both silicon-material properties and on solar cell performance. These studies on the effects of impurities yielded extensive information and models for relating specific elemental concentrations to levels of deleterious effects.

Flat-plate solar array project. Volume 2: Silicon material

NASA Astrophysics Data System (ADS)

Lutwack, R.

1986-10-01

The goal of the Silicon Material Task, a part of the Flat Plate Solar Array (FSA) Project, was to develop and demonstate the technology for the low cost production of silicon of suitable purity to be used as the basic material for the manufacture of terrestrial photovoltaic solar cells. Summarized are 11 different processes for the production of silicon that were investigated and developed to varying extent by industrial, university, and Government researchers. The silane production section of the Union Carbide Corp. (UCC) silane process was developed completely in this program. Coupled with Siemens-type chemical vapor deposition reactors, the process was carried through the pilot stage. The overall UCC process involves the conversion of metallurgical-grade silicon to silane followed by decomposition of the silane to purified silicon. The other process developments are described to varying extents. Studies are reported on the effects of impurities in silicon on both silicon-material properties and on solar cell performance. These studies on the effects of impurities yielded extensive information and models for relating specific elemental concentrations to levels of deleterious effects.

Treatment of diabetes with encapsulated pig islets: an update on current developments*

PubMed Central

Zhu, Hai-tao; Lu, Lu; Liu, Xing-yu; Yu, Liang; Lyu, Yi; Wang, Bo

2015-01-01

The potential use of allogeneic islet transplantation in curing type 1 diabetes mellitus has been adequately demonstrated, but its large-scale application is limited by the short supply of donor islets and the need for sustained and heavy immunosuppressive therapy. Encapsulation of pig islets was therefore suggested with a view to providing a possible alternative source of islet grafts and avoiding chronic immunosuppression and associated adverse or toxic effects. Nevertheless, several vital elements should be taken into account before this therapy becomes a clinical reality, including cell sources, encapsulation approaches, and implantation sites. This paper provides a comprehensive review of xenotransplantation of encapsulated pig islets for the treatment of type 1 diabetes mellitus, including current research findings and suggestions for future studies. PMID:25990050

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

Sanchez, R.O.

Voltage breakdowns become a major concern in reducing the size of high-voltage power converter transformers. Even the smallest of voids can provide a path for corona discharge which can cause a dielectric breakdown leading to a transformer failure. A method of encapsulating small high voltage transformers has been developed. The method virtually eliminates voids in the impregnation material, provides an exceptional dielectric between windings and provides a mechanically rugged package. The encapsulation material is a CTBN modified mica filled epoxy. The method requires heat/vacuum to impregnate the coil and heat/pressure to cure the encapsulant. The transformer package utilizes a Diallylmore » Phthalate (DAP) contact assembly in which a coated core/coil assembly is mounted and soldered. This assembly is then loaded into an RTV mold and the encapsulation process begins.« less

Evaluation of Encapsulated Inhibitor for Autonomous Corrosion Protection

NASA Technical Reports Server (NTRS)

Johnsey, M. N.; Li, W.; Buhrow, J. W.; Calle, L. M.; Pearman, B. P.; Zhang, X.

2015-01-01

This work concerns the development of smart coating technologies based on microencapsulation for the autonomous control of corrosion. Microencapsulation allows the incorporation of corrosion inhibitors into coating which provides protection through corrosion-controlled release of these inhibitors.One critical aspect of a corrosion protective smart coating is the selection of corrosion inhibitor for encapsulation and comparison of the inhibitor function before and after encapsulation. For this purpose, a systematic approach is being used to evaluate free and encapsulated corrosion inhibitors by salt immersion. Visual, optical microscope, and Scanning Electron Microscope (with low-angle backscatter electron detector) are used to evaluate these inhibitors. It has been found that the combination of different characterization tools provide an effective method for evaluation of early stage localized corrosion and the effectiveness of corrosion inhibitors.

Elastin-like polypeptides: the power of design for smart cell encapsulation.

PubMed

Bandiera, Antonella

2017-01-01

Cell encapsulation technology is still a challenging issue. Innovative methodologies such as additive manufacturing, and alternative bioprocesses, such as cell therapeutic delivery, where cell encapsulation is a key tool are rapidly gaining importance for their potential in regenerative medicine. Responsive materials such as elastin-based recombinant expression products have features that are particularly attractive for cell encapsulation. They can be designed and tailored to meet desired requirements. Thus, they represent promising candidates for the development of new concept-based materials that can be employed in this field. Areas covered: An overview of the design and employment of elastin-like polypeptides for cell encapsulation is given to outline the state of the art. Special attention is paid to the design of the macromolecule employed as well as to the method of matrix formation and the biological system involved. Expert opinion: As a result of recent progress in regenerative medicine there is a compelling need for materials that provide specific properties and demonstrate defined functional features. Rationally designed materials that may adapt according to applied external stimuli and that are responsive to biological systems, such as elastin-like polypeptides, belong to this class of smart material. A run through the components described to date represents a good starting point for further advancement in this area. Employment of these components in cell encapsulation application will promote its advance toward 'smart cell encapsulation technology'.

Human embryonic stem cell derived islet progenitors mature inside an encapsulation device without evidence of increased biomass or cell escape.

PubMed

Kirk, Kaitlyn; Hao, Ergeng; Lahmy, Reyhaneh; Itkin-Ansari, Pamela

2014-05-01

There are several challenges to successful implementation of a cell therapy for insulin dependent diabetes derived from human embryonic stem cells (hESC). Among these are development of functional insulin producing cells, a clinical delivery method that eliminates the need for chronic immunosuppression, and assurance that hESC derived tumors do not form in the patient. We and others have shown that encapsulation of cells in a bilaminar device (TheraCyte) provides immunoprotection in rodents and primates. Here we monitored human insulin secretion and employed bioluminescent imaging (BLI) to evaluate the maturation, growth, and containment of encapsulated islet progenitors derived from CyT49 hESC, transplanted into mice. Human insulin was detectable by 7 weeks post-transplant and increased 17-fold over the course of 8 weeks, yet during this period the biomass of encapsulated cells remained constant. Remarkably, by 20 weeks post-transplant encapsulated cells secreted sufficient levels of human insulin to ameliorate alloxan induced diabetes. Further, bioluminescent imaging revealed for the first time that hESCs remained fully contained in encapsulation devices for up to 150 days, the longest period tested. Collectively, the data suggest that encapsulated hESC derived islet progenitors hold great promise as an effective and safe cell replacement therapy for insulin dependent diabetes. Copyright © 2014. Published by Elsevier B.V.

Induction by TNF-α of IL-6 and IL-8 in cystic fibrosis bronchial IB3-1 epithelial cells encapsulated in alginate microbeads.

PubMed

Borgatti, Monica; Mazzitelli, Stefania; Breveglieri, Giulia; Gambari, Roberto; Nastruzzi, Claudio

2010-01-01

We have developed a microencapsulation procedure for the entrapment and manipulation of IB3-1 cystic fibrosis cells. The applied method is based on generation of monodisperse droplets by a vibrational nozzle. Different experimental parameters were analyzed, including frequency and amplitude of vibration, polymer pumping rate and distance between the nozzle and the gelling bath. We have found that the microencapsulation procedure does not alter the viability of the encapsulated IB3-1 cells. The encapsulated IB3-1 cells were characterized in term of secretomic profile, analyzing the culture medium by Bio-Plex strategy. The experiments demonstrated that most of the analyzed proteins, were secreted both by the free and encapsulated cells, even if in a different extent. In order to determine the biotechnological applications of this procedure, we determined whether encapsulated IB3-1 cells could be induced to pro-inflammatory responses, after treatment with TNF-α. In this experimental set-up, encapsulated and free IB3-1 cells were treated with TNF-α, thereafter the culture media from both cell populations were collected. As expected, TNF-α induced a sharp increase in the secretion of interleukins, chemokines and growth factors. Of great interest was the evidence that induction of interleukin-6 and interleukin-8 occurs also by encapsulated IB3-1 cells.

Carbon dioxide as a green carbon source for the synthesis of carbon cages encapsulating porous silicon as high performance lithium-ion battery anodes.

PubMed

Zhang, Yaguang; Du, Ning; Chen, Yifan; Lin, Yangfan; Jiang, Jinwei; He, Yuanhong; Lei, Yu; Yang, Deren

2018-03-28

Si/C composite is one of the most promising candidate materials for next-generation lithium-ion battery anodes. Herein, we demonstrate the novel structure of carbon cages encapsulating porous Si synthesized by the reaction between magnesium silicide (Mg 2 Si) and carbon dioxide (CO 2 ) and subsequent acid washing. Benefitting from the in situ deposition through magnesiothermic reduction of CO 2 , the carbon cage seals the inner Si completely and shows higher graphitization than that obtained from the decomposition of acetylene. After removing MgO, pores are created, which can accommodate the volume change of the Si anode during the charge/discharge process. As the anode material for lithium-ion batteries, the porous Si/C electrode shows a charge capacity of ∼1124 mA h g -1 after 100 cycles with 86.4% capacity retention at the current density of 0.4 A g -1 . When the current density increases to 1.6 and 3.2 A g -1 , the capacity can still be maintained at ∼860 and ∼460 mA h g -1 , respectively. The prominent cycling and rate performance is contributed by the built-in space for Si expansion, static carbon cages that prevent penetration of electrolyte and stabilize the solid electrolyte interface (SEI) outside, and fast charge transport by the novel structure.

Center for the development of commercial crystal growth in space

NASA Technical Reports Server (NTRS)

Wilcox, William R.

1989-01-01

The second year of operation of the Center for Commercial Crystal Growth in Space is described. This center is a consortium of businesses, universities and national laboratories. The primary goal of the Center's research is the development of commercial crystal growth in space. A secondary goal is to develop scientific understanding and technology which will improve commercial crystal growth on earth. In order to achieve these goals the Center's research is organized into teams by growth technique; melt growth, solution growth, and vapor growth. The melt growth team is working on solidification and characterization of bulk crystals of gallium arsenide and cadmium telluride. They used high resolution X-ray topography performed at the National Synchrotron Light Source at Brookhaven National Laboratory. Streak-like features were found in the diffraction images of semi-insulating undoped LEC GaAs. These were shown to be (110) antiphase boundaries, which have not been reported before but appear to be pervasive and responsible for features seen via less-sensitive characterization methods. The results on CdTe were not as definitive, but indicate that antiphase boundaries may also be responsible for the double peaks often seen in X-ray rocking curves of this material. A liquid encapsulated melt zone system for GaAs has been assembled and techniques for casting feed rods developed. It was found that scratching the inside of the quartz ampoules with silicon carbide abrasive minimized sticking of the GaAs to the quartz. Twelve floating zone experiments were done.

Effect of PdO on TiO(sub2) Loading on Chemochromic Detection of Hydrogen

NASA Technical Reports Server (NTRS)

Mohajeri, Nahid; T-Rassisi, Ali; Bokerman, Gary; Captain, Janine E.; Peterson, Barbara V.; Whitten, Mary; Berger, Cristina

2007-01-01

Safety is always a concern in all applications that utilize hydrogen (H(sub2)) in one form or the other. Hydrogen leaks are invisible and odorless. In addition, blending odorants or additives into hydrogen in a manner similar to natural gas is generally undesirable for certain applications including proton exchange membrane fuel cells. To facilitate detection of the location of hydrogen leaks, a special chemochromic H(sub2) sensing material that employs titania (Ti0(sub2)) supported palladium oxide (PdO) pigments encapsulated within a special silicone matrix has been developed at the Florida Solar Energy Center (FSEC). Several batches of PdO H(sub2) sensing pigments were synthesized using various Ti0(sub2) supports and their hydrogen detection activity determined. TEM and Particle size distribution analysis showed that smaller particles with hemispherical crystalline structure produced faster coloration kinetics when exposed to H(sub2) gas. However, uniformly distributed PdO particles on the Ti0(sub2) surface displayed greater color contrast, quantified by delta epsilon measurements. XRD analysis indicated that the crystalline phase of Ti0(sub2) had no effect on the chemochromic performance of the pigments in laboratory environment.

Design of a portable near infrared system for topographic imaging of the brain in babies

NASA Astrophysics Data System (ADS)

Vaithianathan, Tharshan; Tullis, Iain D. C.; Everdell, Nicholas; Leung, Terence; Gibson, Adam; Meek, Judith; Delpy, David T.

2004-10-01

A portable topographic near-infrared spectroscopic (NIRS) imaging system has been developed to provide real-time temporal and spatial information about the cortical response to stimulation in unrestrained infants. The optical sensing array is lightweight, flexible, and easy to apply to infants ranging from premature babies in intensive care to children in a normal environment. The sensor pad consists of a flexible double-sided circuit board onto which are mounted multiple sources (light-emitting diodes) and multiple detectors (p-i-n photodiodes), all electrically encapsulated in silicone rubber. The control electronics are housed in a box with a medical grade isolated power supply and linked to a PC fitted with a data acquisition card, the signal acquisition and analysis being performed using LABVIEW™. The signal output is displayed as an image of oxy- and deoxyhemoglobin concentration ([HbO2], [Hb]) changes at a frame rate of 3 Hz. Experiments have been conducted on phantoms to determine the sensitivity of the system, and the results have been compared to theoretical simulations. The system has been tested in volunteers by imaging changes in forearm muscle oxygenation, following blood pressure cuff occlusion to obtain typical [Hb] and [HbO2] plots.

A cell-laden microfluidic hydrogel.

PubMed

Ling, Yibo; Rubin, Jamie; Deng, Yuting; Huang, Catherine; Demirci, Utkan; Karp, Jeffrey M; Khademhosseini, Ali

2007-06-01

The encapsulation of mammalian cells within the bulk material of microfluidic channels may be beneficial for applications ranging from tissue engineering to cell-based diagnostic assays. In this work, we present a technique for fabricating microfluidic channels from cell-laden agarose hydrogels. Using standard soft lithographic techniques, molten agarose was molded against a SU-8 patterned silicon wafer. To generate sealed and water-tight microfluidic channels, the surface of the molded agarose was heated at 71 degrees C for 3 s and sealed to another surface-heated slab of agarose. Channels of different dimensions were generated and it was shown that agarose, though highly porous, is a suitable material for performing microfluidics. Cells embedded within the microfluidic molds were well distributed and media pumped through the channels allowed the exchange of nutrients and waste products. While most cells were found to be viable upon initial device fabrication, only those cells near the microfluidic channels remained viable after 3 days, demonstrating the importance of a perfused network of microchannels for delivering nutrients and oxygen to maintain cell viability in large hydrogels. Further development of this technique may lead to the generation of biomimetic synthetic vasculature for tissue engineering, diagnostics, and drug screening applications.

Influence of barrier absorption properties on laser patterning thin organic films

NASA Astrophysics Data System (ADS)

Naithani, Sanjeev; Mandamparambil, Rajesh; van Assche, Ferdie; Schaubroeck, David; Fledderus, Henri; Prenen, An; Van Steenberge, Geert; Vanfleteren, Jan

2012-06-01

This paper presents a study of selective ablation of thin organic films (LEP- Light Emitting Polymer, PEDOT:PSS- Poly 3,4-ethylenedioxythiophene: polystyrene sulfonate) by using 248 nm Excimer laser, on various kinds of multilayered SiN barrier foils for the development of Organic Light Emitting Diodes (OLED). Different Silicon Nitride (SiN) barrier foils with dedicated absorption spectra are taken into account for this purpose. The drive for looking into different types of SiN originates from the fact that the laser selective removal of a polymer without damage to the barrier layer underneath is challenging in the dynamic laser processing of thin films. The barrier is solely responsible for the proper encapsulation of the OLED stack. The main limitation of current OLED design is its shorter life span, which is directly related to the moisture or water permeation into the stack, leading to black spots. An optimization of laser parameters like fluence and number of shots has been carried out for the various types of SiN barrier foils. We are able to obtain a wider working process window for the selective removal of LEP and PEDOT:PSS from SiN barrier, by variation of the different types of SiN.

Sustained release of adipose-derived stem cells by thermosensitive chitosan/gelatin hydrogel for therapeutic angiogenesis.

PubMed

Cheng, Nai-Chen; Lin, Wei-Jhih; Ling, Thai-Yen; Young, Tai-Horng

2017-03-15

Adipose-derived stem cells (ASCs) secrete several angiogenic growth factors and can be applied to treat ischemic tissue. However, transplantation of dissociated ASCs has frequently resulted in rapid cell death. Therefore, we aimed to develop a thermosensitive chitosan/gelatin hydrogel that is capable of ASC sustained release for therapeutic angiogenesis. By blending gelatin in the chitosan thermosensitive hydrogel, we significantly enhanced the viability of the encapsulated ASCs. During in vitro culturing, the gradual degradation of gelatin led to sustained release of ASCs from the chitosan/gelatin hydrogel. In vitro wound healing assays revealed significantly faster cell migration by co-culturing fibroblasts with ASCs encapsulated in chitosan/gelatin hydrogel compared to pure chitosan hydrogels. Additionally, significantly higher concentrations of vascular endothelial growth factor were found in the supernatant of ASC-encapsulated chitosan/gelatin hydrogels. Co-culturing SVEC4-10 endothelial cells with ASC-encapsulated chitosan/gelatin hydrogels resulted in significantly more tube-like structures, indicating the hydrogel's potential in promoting angiogenesis. Chick embryo chorioallantoic membrane assay and mice wound healing model showed significantly higher capillary density after applying ASC-encapsulated chitosan/gelatin hydrogel. Relative to ASC alone or ASC-encapsulated chitosan hydrogel, more ASCs were also found in the wound tissue on post-wounding day 5 after applying ASC-encapsulated chitosan/gelatin hydrogel. Therefore, chitosan/gelatin thermosensitive hydrogels not only maintain ASC survival, they also enable sustained release of ASCs for therapeutic angiogenesis applications, thereby exhibiting great clinical potential in treating ischemic diseases. Adipose-derived stem cells (ASCs) exhibit great potential to treat ischemic diseases. However, poor delivery methods lead to low cellular survival or dispersal of cells from target sites. In this study, we developed a thermosensitive chitosan/gelatin hydrogel that not only enhances the viability of the encapsulated ASCs, the gradual degradation of gelatin also result in a more porous architecture, leading to sustained release of ASCs from the hydrogel. ASC-encapsulated hydrogel enhanced in vitro wound healing of fibroblasts and tube formation of endothelial cells. It also promoted in vivo angiogenesis in a chick embryo chorioallantoic membrane assay and a mice wound model. Therefore, chitosan/gelatin hydrogel represents an effective delivery system that allows for controlled release of viable ASCs for therapeutic angiogenesis. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Anti-Inflammatory Peptide Functionalized Hydrogels for Insulin-Secreting Cell Encapsulation

PubMed Central

Su, Jing; Hu, Bi-Huang; Lowe, William L.; Kaufman, Dixon B.; Messersmith, Phillip B.

2009-01-01

Pancreatic islet encapsulation within semi-permeable materials has been proposed for transplantation therapy of Type I diabetes mellitus. Polymer hydrogel networks used for this purpose have been shown to provide protection from islet destruction by immunoreactive cells and antibodies. However, one of the fundamental deficiencies with current encapsulation methods is that the permselective barriers cannot protect islets from cytotoxic molecules of low molecular weight that are diffusible into the capsule material, which subsequently results in β-cell destruction. Use of materials that can locally inhibit the interaction between the permeable small cytotoxic factors and islet cells may prolong the viability and function of encapsulated islet grafts. Here we report the design of anti-inflammatory hydrogels supporting islet cell survival in the presence of diffusible pro-inflammatory cytokines. We demonstrated that a poly(ethylene glycol)-containing hydrogel network, formed by native chemical ligation and presenting an inhibitory peptide for islet cell surface IL-1 receptor, was able to maintain the viability of encapsulated islet cells in the presence of a combination of cytokines including IL-1β, TNF-α, and INF-γ. In stark contrast, cells encapsulated in unmodified hydrogels were mostly destroyed by cytokines which diffused into the capsules. At the same time, these peptide-modified hydrogels were able to efficiently protect encapsulated cells against β-cell specific T-lymphocytes and maintain glucose-stimulated insulin release by islet cells. With further development, the approach of encapsulating cells and tissues within hydrogels presenting anti-inflammatory agents may represent a new strategy to improve cell and tissue graft function in transplantation and tissue engineering applications. PMID:19782393

Controlled-release of tea polyphenol from gelatin films incorporated with different ratios of free/nanoencapsulated tea polyphenols into fatty food simulants

USDA-ARS?s Scientific Manuscript database

Gelatin films having controlled-release properties were developed by incorporation of different free/encapsulated tea polyphenol (TP) ratios through modifying the encapsulation efficiency (EE) of TP-loaded chitosan nanoparticles. Different EEs were obtained by adjusting the chitosan hydrochloride (C...

Developing planetary protection technology- microbial diversity of the Mars Orbiter Odyssey and the spacecraft assembly and encapsulation facility II

NASA Technical Reports Server (NTRS)

Duc, M. La; Chen, F.; Kern, R.; Koukol, R.; Baker, A.; Venkateswaran, K.

2001-01-01

A study in which several surface samples, retrieved from both the Mars Odyssey Spacecraft and the Kennedy Space Center (KSC) Spacecraft Assembly and Encapsulation Facility II (SAEF-II), were prcesed and evaluated by both molecular and traditional culture-based methods for the microbial diversity.

Development of Intra-Articular Drug Delivery to Alter Progression of Arthritis Following Joint Injury

DTIC Science & Technology

2013-04-01

sTNFRII in combination. The treatments were encapsulated in elastin -like polypeptide (ELP) drug depots that have been associated with a 25-fold...or both IL-1Ra and sTNFRII. The drugs were encapsulated in elastin -like polypeptide (ELP) drug depots that slowly disaggregate for prolonged IA

Encapsulated Optically Responsive Cell Systems: Toward Smart Implants in Biomedicine.

PubMed

Boss, Christophe; Bouche, Nicolas; De Marchi, Umberto

2018-04-01

Managing increasingly prevalent chronic diseases will require close continuous monitoring of patients. Cell-based biosensors may be used for implantable diagnostic systems to monitor health status. Cells are indeed natural sensors in the body. Functional cellular systems can be maintained in the body for long-term implantation using cell encapsulation technology. By taking advantage of recent progress in miniaturized optoelectronic systems, the genetic engineering of optically responsive cells may be combined with cell encapsulation to generate smart implantable cell-based sensing systems. In biomedical research, cell-based biosensors may be used to study cell signaling, therapeutic effects, and dosing of bioactive molecules in preclinical models. Today, a wide variety of genetically encoded fluorescent sensors have been developed for real-time imaging of living cells. Here, recent developments in genetically encoded sensors, cell encapsulation, and ultrasmall optical systems are highlighted. The integration of these components in a new generation of biosensors is creating innovative smart in vivo cell-based systems, bringing novel perspectives for biomedical research and ultimately allowing unique health monitoring applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Development and characterization of phosphatidylcholine nanovesicles, containing garlic extract, with antilisterial activity in milk.

PubMed

Pinilla, Cristian Mauricio Barreto; Noreña, Caciano Pelayo Zapata; Brandelli, Adriano

2017-04-01

Phospholipid nanovesicles were developed to improve the stability of garlic (Allium sativum L.) extract. Electron microscopy of liposomes revealed nanometric and spherical-shaped vesicles with a mean particle size of 174.6±17.3nm and polydispersity index of 0.26±0.02. The entrapment efficiency was 47.5±7.3% and the nanoliposomes had a zeta potential of -16.2±5.5mV. The antimicrobial activity of free and encapsulated garlic extract was evaluated against different strains of Listeria spp. in milk at 37°C for 24h. For free and encapsulated garlic extracts at 5% concentration, a decrease of 4log cycles in viable cell counts was observed at 10h, against four of the five strains of Listeria spp. tested. The results indicate that liposomes constitute a suitable system for encapsulation of unstable garlic active compounds and the encapsulation of garlic extract proves to be a promising technology for multiple applications, including antimicrobial agents. Copyright © 2016 Elsevier Ltd. All rights reserved.

Development and characterization of a novel drug nanocarrier for oral delivery, based on self-assembled β-casein micelles.

PubMed

Bachar, Michal; Mandelbaum, Amitai; Portnaya, Irina; Perlstein, Hadas; Even-Chen, Simcha; Barenholz, Yechezkel; Danino, Dganit

2012-06-10

β-casein is an amphiphilic protein that self-organizes into well-defined core-shell micelles. We developed these micelles as efficient nanocarriers for oral drug delivery. Our model drug is celecoxib, an anti-inflammatory hydrophobic drug utilized for treatment of rheumatoid arthritis and osteoarthritis, now also evaluated as a potent anticancer drug. This system is unique as it enables encapsulation loads >100-fold higher than other β-casein/drug formulations, and does not require additives as do other formulations that have high loadings. This is combined with the ability to lyophilize the formulation without a cryoprotectant, long-term physical and chemical stability of the resulting powder, and fully reversible reconstitution of the structures by rehydration. The dry dosage form, in which >95% of the drug is encapsulated, meets the daily dose. Cryo-TEM and DLS prove that drug encapsulation results in micelle swelling, and X-ray diffraction shows that the encapsulated drug is amorphous. Altogether, our novel dosage form is highly advantageous for oral administration. Copyright © 2012 Elsevier B.V. All rights reserved.

A "ship in a bottle" strategy to load a hydrophilic anticancer drug in porous metal organic framework nanoparticles: efficient encapsulation, matrix stabilization, and photodelivery.

PubMed

di Nunzio, Maria Rosaria; Agostoni, Valentina; Cohen, Boiko; Gref, Ruxandra; Douhal, Abderrazzak

2014-01-23

An essential challenge in the development of nanosized metal organic framework (nanoMOF) materials in biomedicine is to develop a strategy to stabilize their supramolecular structure in biological media while being able to control drug encapsulation and release. We have developed a method to efficiently encapsulate topotecan (TPT, 1), an important cytotoxic drug, in biodegradable nanoMOFs. Once inside the pores, 1 monomers aggregate in a "ship in a bottle" fashion, thus filling practically all of the nanoMOFs' available free volume and stabilizing their crystalline supramolecular structures. Highly efficient results have been found with the human pancreatic cell line PANC1, in contrast with free 1. We also demonstrate that one- and two-photon light irradiation emerges as a highly promising strategy to promote stimuli-dependent 1 release from the nanoMOFs, hence opening new standpoints for further developments in triggered drug delivery.

Negative-tone development of photoresists in environmentally friendly silicone fluids

NASA Astrophysics Data System (ADS)

Ouyang, Christine Y.; Lee, Jin-Kyun; Ober, Christopher K.

2012-03-01

The large amount of organic solvents and chemicals that are used in today's microelectronic fabrication process can lead to environmental, health and safety hazards. It is therefore necessary to design new materials and new processes to reduce the environmental impact of the lithographic process. In addition, as the feature sizes decrease, other issues such as pattern collapse, which is related to the undesirable high surface tension of the developers and rinse liquids, can occur and limit the resolution. In order to solve these issues, silicone fluids are chosen as alternative developing solvents in this paper. Silicone fluids, also known as linear methyl siloxanes, are a class of mild, non-polar solvents that are non-toxic, not ozone-depleting, and contribute little to global warming. They are considered as promising developers because of their environmental-friendliness and their unique physical properties such as low viscosity and low surface tension. Recently, there have been emerging interests in negative-tone development (NTD) due to its better ability in printing contact holes and trenches. It is also found that the performance of negative-tone development is closely related to the developing solvents. Silicone fluids are thus promising developers for NTD because of their non-polar nature and high contrast negative-tone images are expected with chemical amplification photoresists due to the high chemical contrast of chemical amplification. We have previously shown some successful NTD with conventional photoresists such as ESCAP in silicone fluids. In this paper, another commercially available TOK resist was utilized to study the NTD process in silicone fluids. Because small and non-polar molecules are intrinsically soluble in silicone fluids, we have designed a molecular glass resist for silicone fluids. Due to the low surface tension of silicone fluids, we are able achieve high aspect-ratio, high-resolution patterns without pattern collapse.

Multifunctional microbubbles and nanobubbles for photoacoustic and ultrasound imaging

PubMed Central

Kim, Chulhong; Qin, Ruogu; Xu, Jeff S.; Wang, Lihong V.; Xu, Ronald

2010-01-01

We develop a novel dual-modal contrast agent—encapsulated-ink poly(lactic-co-glycolic acid) (PLGA) microbubbles and nanobubbles—for photoacoustic and ultrasound imaging. Soft gelatin phantoms with embedded tumor simulators of encapsulated-ink PLGA microbubbles and nanobubbles in various concentrations are clearly shown in both photoacoustic and ultrasound images. In addition, using photoacoustic imaging, we successfully image the samples positioned below 1.8-cm-thick chicken breast tissues. Potentially, simultaneous photoacoustic and ultrasound imaging enhanced by encapsulated-dye PLGA microbubbles or nanobubbles can be a valuable tool for intraoperative assessment of tumor boundaries and therapeutic margins. PMID:20210423

Development of a process for high capacity-arc heater production of silicon

NASA Technical Reports Server (NTRS)

Reed, W. H.; Meyer, T. N.; Fey, M. G.; Harvey, F. J.; Arcella, F. G.

1978-01-01

The realization of low cost, electric power from large-area silicon, photovoltaic arrays will depend on the development of new methods for large capacity production of solar grade (SG) silicon with a cost of less than $10 per kilogram by 1986 (established Department of Energy goal). The objective of the program is to develop a method to produce SG silicon in large quantities based on the high temperature-sodium reduction of silicon tetrachloride (SiCl4) to yield molten silicon and the coproduct salt vapor (NaCl). Commercial ac electric arc heaters will be utilized to provide a hyper-heated mixture of argon and hydrogen which will furnish the required process energy. The reactor is designed for a nominal silicon flow rate of 45 kg/hr. Analyses and designs have been conducted to evaluate the process and complete the initial design of the experimental verification unit.

Study program to develop and evaluate die and container materials for the growth of silicon ribbons. [for development of low cost solar cells

NASA Technical Reports Server (NTRS)

Addington, L. A.; Ownby, P. D.; Yu, B. B.; Barsoum, M. W.; Romero, H. V.; Zealer, B. G.

1979-01-01

The development and evaluation of proprietary coatings of pure silicon carbide, silicon nitride, and aluminum nitride on less pure hot pressed substrates of the respective ceramic materials, is described. Silicon sessile drop experiments were performed on coated test specimens under controlled oxygen partial pressure. Prior to testing, X-ray diffraction and SEM characterization was performed. The reaction interfaces were characterized after testing with optical and scanning electron microscopy and Auger electron spectroscopy. Increasing the oxygen partial pressure was found to increase the molten silicon contact angle, apparently because adsorbed oxygen lowers the solid-vapor interfacial free energy. It was also found that adsorbed oxygen increased the degree of attack of molten silicon upon the chemical vapor deposited coatings. Cost projections show that reasonably priced, coated, molten silicon resistant refractory material shapes are obtainable.

Development of an attract-and-kill co-formulation containing Saccharomyces cerevisiae and neem extract attractive towards wireworms.

PubMed

Humbert, Pascal; Vemmer, Marina; Mävers, Frauke; Schumann, Mario; Vidal, Stefan; Patel, Anant V

2018-07-01

Wireworms (Coleoptera: Elateridae) are major insect pests of worldwide relevance. Owing to the progressive phasing-out of chemical insecticides, there is great demand for innovative control options. This study reports on the development of an attract-and-kill co-formulation based on Ca-alginate beads, which release CO 2 and contain neem extract as a bioinsecticidal compound. The objectives of this study were to discover: (1) whether neem extract can be immobilized efficiently, (2) whether CO 2 -releasing Saccharomyces cerevisiae and neem extract are suitable for co-encapsulation, and (3) whether co-encapsulated neem extract affects the attractiveness of CO 2 -releasing beads towards wireworms. Neem extract was co-encapsulated together with S. cerevisiae, starch and amyloglucosidase with a high encapsulation efficiency of 98.6% (based on measurement of azadirachtin A as the main active ingredient). Even at enhanced concentrations, neem extract allowed growth of S. cerevisiae, and beads containing neem extract exhibited CO 2 -emission comparable with beads without neem extract. When applied to the soil, the beads established a CO 2 gradient of >15 cm. The co-formulation containing neem extract showed no repellent effects and was attractive for wireworms within the first 24 h after exposure. Co-encapsulation of S. cerevisiae and neem extract is a promising approach for the development of attract-and-kill formulations for the control of wireworms. This study offers new options for the application of neem extracts in soil. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Preparation of mesoporous silica microparticles by sol-gel/emulsion route for protein release.

PubMed

Vlasenkova, Mariya I; Dolinina, Ekaterina S; Parfenyuk, Elena V

2018-04-06

Encapsulation of therapeutic proteins into particles from appropriate material can improve both stability and delivery of the drugs, and the obtained particles can serve as a platform for development of their new oral formulations. The main goal of this work was development of sol-gel/emulsion method for preparation of silica microcapsules capable of controlled release of encapsulated protein without loss of its native structure. For this purpose, the reported in literature direct sol-gel/W/O/W emulsion method of protein encapsulation was used with some modifications, because the original method did not allow to prepare silica microcapsules capable for protein release. The particles were synthesized using sodium silicate and tetraethoxysilane as silica precursors and different compositions of oil phase. In vitro kinetics of bovine serum albumin (BSA) release in buffer (pH 7.4) was studied by Fourier transform infrared (FTIR) and fluorescence spectrometry, respectively. Structural state of encapsulated BSA and after release was evaluated. It was found that the synthesis conditions influenced substantially the porous structure of the unloaded silica particles, release properties of the BSA-loaded silica particles and structural state of the encapsulated and released protein. The modified synthesis conditions made it possible to obtain the silica particles capable of controlled release of the protein during a week without loss of the protein native structure.

Disruption of Cell-Cell Contact-mediated Notch Signaling via Hydrogel Encapsulation Reduces Mesenchymal Stem Cell Chondrogenic Potential

PubMed Central

Chen, Amanda X.; Hoffman, Michael D.; Chen, Caressa S.; Shubin, Andrew D.; Reynolds, Daniel S.; Benoit, Danielle S. W.

2015-01-01

Cell-cell contact-mediated Notch signaling is essential for mesenchymal stem cell (MSC) chondrogenesis during development. However, subsequent deactivation of Notch signaling is also required to allow for stem cell chondrogenic progression. Recent literature has shown that Notch signaling can also influence Wnt/β-catenin signaling, critical for MSC differentiation, through perturbations in cell-cell contacts. Traditionally, abundant cell-cell contacts, consistent with development, are emulated in vitro using pellet cultures for chondrogenesis. However, cells are often encapsulated within biomaterials-based scaffolds, such as hydrogels, to improve therapeutic cell localization in vivo. To explore the role of Notch and Wnt/β-catenin signaling in the context of hydrogel-encapsulated MSC chondrogenesis, we compared signaling and differentiation capacity of MSCs in both hydrogels and traditional pellet cultures. We demonstrate that encapsulation within poly(ethylene glycol) (PEG) hydrogels reduces cell-cell contacts, and both Notch (7.5-fold) and Wnt/β-catenin (84.7-fold) pathway activation. Finally, we demonstrate that following establishment of cell-cell contacts and transient Notch signaling in pellet cultures, followed by Notch signaling deactivation, resulted in a 1.5-fold increase in MSC chondrogenesis. Taken together, these findings support that cellular condensation, and the establishment of initial cell-cell contacts is critical for MSC chondrogenesis, and this process is inhibited by hydrogel encapsulation. PMID:25504509

Low cost solar array project. Experimental process system development unit for producing semiconductor-grade silicon using the silane-to-silicon process

NASA Technical Reports Server (NTRS)

1980-01-01

Technical activities are reported in the design of process, facilities, and equipment for producing silicon at a rate and price comensurate with production goals for low cost solar cell modules. The silane-silicone process has potential for providing high purity poly-silicon on a commercial scale at a price of fourteen dollars per kilogram by 1986, (1980 dollars). Commercial process, economic analysis, process support research and development, and quality control are discussed.

Validation of a cage implant system for assessing in vivo performance of long-acting release microspheres.

PubMed

Doty, Amy C; Hirota, Keiji; Olsen, Karl F; Sakamoto, Naoya; Ackermann, Rose; Feng, Meihua R; Wang, Yan; Choi, Stephanie; Qu, Wen; Schwendeman, Anna; Schwendeman, Steven P

2016-12-01

Here we describe development of a silicone rubber/stainless steel mesh cage implant system, much like that used to assess biocompatibility of biomaterials [1], for easy removal of injectable polymer microspheres in vivo. The sterile cage has a type 316 stainless steel mesh size (38 μm) large enough for cell penetration and free fluid flow in vivo but small enough for microsphere retention, and a silicone rubber shell for injection of the microspheres. Two model drugs, the poorly soluble steroid, triamcinolone acetonide, and the highly water-soluble luteinizing hormone-releasing hormone (LHRH) peptide superagonist, leuprolide, were encapsulated in PLGA microspheres large enough (63-90 μm) to be restrained by the cage implant in vivo. The in vitro release from both formulations was followed by ultra-performance liquid chromatography (UPLC) with and without the cage in a standard release media, PBS pH 7.4 + 0.02% Tween 80 + 0.05% sodium azide, at 37 °C. Pharmacokinetics (PK) in rats was assessed after SC injection or SC in-cage implantation of microspheres with plasma analysis by LC-MS/MS or EIA. Tr-A and leuprolide in vitro release was largely unaffected after the initial burst irrespective of the cage or test tube incubation vessel and release was much slower than observed in vivo for both drugs. Moreover, Tr-A and leuprolide pharmacokinetics with and without the cage were highly similar during the 2-3 week release duration before a significant inflammatory response was caused by the cage implant. Hence, the PK-validated cage implant provides a simple means to recover and evaluate the microsphere drug carriers in vivo during a time window of at least a few weeks in order to characterize the polymer microsphere release and erosion behavior in vivo. This approach may facilitate development of mechanism-based in vitro/in vivo correlations and enable development of more accurate and useful in vitro release tests. Copyright © 2016 Elsevier Ltd. All rights reserved.

Alginate/cashew gum nanoparticles for essential oil encapsulation.

PubMed

de Oliveira, Erick F; Paula, Haroldo C B; de Paula, Regina C M

2014-01-01

Alginate/cashew gum nanoparticles were prepared via spray-drying, aiming at the development of a biopolymer blend for encapsulation of an essential oil. Nanoparticles were characterized regarding to their hydrodynamic volume, surface charge, Lippia sidoides essential oil content and release profile, in addition to being analyzed by infrared spectroscopy (FT-IR), thermal analysis (TGA/DSC) and X-ray diffractometry. Nanoparticles in solution were found to have averaged sizes in the range 223-399 nm, and zeta potential values ranging from -30 to -36 mV. Encapsulated oil levels varied from 1.9 to 4.4% with an encapsulation efficiency of up to 55%. The in vitro release profile showed that between 45 and 95% of oil was released within 30-50h. Kinetic studies revealed that release pattern follow a Korsmeyer-Peppas mechanism. Copyright © 2013 Elsevier B.V. All rights reserved.

A comprehensive overview on the micro- and nano-technological encapsulation advances for enhancing the chemical stability and bioavailability of carotenoids.

PubMed

Soukoulis, Christos; Bohn, Torsten

2018-01-02

Carotenoids are lipophilic secondary plant compounds, and their consumption within fruits and vegetables has been positively correlated with a decreased risk of developing several chronic diseases. However, their bioavailability is often compromised due to incomplete release from the food matrix, poor solubility and potential degradation during digestion. In addition, carotenoids in food products are prone to oxidative degradation, not only lowering the nutritional value of the product but also triggering other quality deteriorative changes, such as formation of lipid pro-oxidants (free radicals), development of discolorations or off-flavor defects. Encapsulation refers to a physicochemical process, aiming to entrap an active substance in structurally engineered micro- or nano-systems, in order to develop an effective thermodynamical and physical barrier against deteriorative environmental conditions, such as water vapor, oxygen, light, enzymes or pH. In this context, encapsulation of carotenoids has shown to be a very effective strategy to improve their chemical stability under common processing conditions including storage. In addition, encapsulation may also enhance bioavailability (via influencing bioaccessibility and absorption) of lipophilic bioactives, via modulating their release kinetics from the carrier system, solubility and interfacial properties. In the present paper, it is aimed to present the state of the art of carotenoid microencapsulation in order to enhance storability and bioavailability alike.

Silicon-on-ceramic process: Silicon sheet growth and device development for the large-area silicon sheet task of the low-cost solar array project

NASA Technical Reports Server (NTRS)

Whitehead, A. B.; Zook, J. D.; Grung, B. L.; Heaps, J. D.; Schmit, F.; Schuldt, S. B.; Chapman, P. W.

1981-01-01

The technical feasibility of producing solar cell quality sheet silicon to meet the DOE 1986 cost goal of 70 cents/watt was investigated. The silicon on ceramic approach is to coat a low cost ceramic substrate with large grain polycrystalline silicon by unidirectional solidification of molten silicon. Results and accomplishments are summarized.

MEMS sensing and control: an aerospace perspective

NASA Astrophysics Data System (ADS)

Schoess, Jeffrey N.; Arch, David K.; Yang, Wei; Cabuz, Cleopatra; Hocker, Ben; Johnson, Burgess R.; Wilson, Mark L.

2000-06-01

Future advanced fixed- and rotary-wing aircraft, launch vehicles, and spacecraft will incorporate smart microsensors to monitor flight integrity and provide flight control inputs. This paper provides an overview of Honeywell's MEMS technologies for aerospace applications of sensing and control. A unique second-generation polysilicon resonant microbeam sensor design is described. It incorporates a micron-level vacuum-encapsulated microbeam to optically sense aerodynamic parameters and to optically excite the sensor pick off: optically excited self-resonant microbeams form the basis for a new class of versatile, high- performance, low-cost MEMS sensors that uniquely combine silicon microfabrication technology with optoelectronic technology that can sense dynamic pressure, acceleration forces, acoustic emission, and many other aerospace parameters of interest. Honeywell's recent work in MEMS tuning fork gyros for inertial sensing and a MEMS free- piston engine are also described.

Analysis and experimental study on the strain transfer mechanism of an embedded basalt fiber-encapsulated fiber Bragg grating sensor

NASA Astrophysics Data System (ADS)

Zhang, Zhenglin; Wang, Yuan; Sun, Yangyang; Zhang, Qinghua; You, Zewei; Huang, Xiaodi

2017-01-01

The precision of the encapsulated fiber optic sensor embedded into a host suffers from the influences of encapsulating materials. Furthermore, an interface transfer effect of strain sensing exists. This study uses an embedded basalt fiber-encapsulated fiber Bragg grating (FBG) sensor as the research object to derive an expression in a multilayer interface strain transfer coefficient by considering the mechanical properties of the host material. The direct impact of the host material on the strain transfer at an embedded multipoint continuous FBG (i.e., multiple gratings written on a single optical fiber) monitoring strain sensor, which was self-developed and encapsulated with basalt fiber, is studied to present the strain transfer coefficients corresponding to the positions of various gratings. The strain transfer coefficients of the sensor are analyzed based on the experiments designed for this study. The error of the experimental results is ˜2 μɛ when the strain is at 60 μɛ and below. Moreover, the measured curves almost completely coincide with the theoretical curves. The changes in the internal strain field inside the embedded structure of the basalt fiber-encapsulated FBG strain sensor could be easily monitored. Hence, important references are provided to measure the internal stress strain of the sensor.

Hybrid Encapsulated Ionic Liquids for Post-Combustion Carbon Dioxide (CO 2) Capture

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

Brennecke, Joan; Degnan, Thomas; McCready, Mark

Ionic liquids (ILs) and Phase Change Ionic Liquids (PCILs) are excellent materials for selective removal of carbon dioxide from dilute post-combustion streams. However, they are typically characterized as having high viscosities, which impairs their effectiveness due to mass transfer limitations, caused by the high viscosities. In this project, we are examining the benefits of encapsulating ILs and PCILs in thin polymeric shells to produce particles of approximately 100 to 600 μm in diameter that can be used in a fluidized bed absorber. The particles are produced by microencapsulation of the ILs and PCILs in CO 2-permeable polymer shells. Here wemore » report on the synthesis of the IL and PCIL materials, measurements of thermophysical properties including CO 2 capacity and reprotonation equilibrium and kinetics, encapsulation of the ILs and PCILs, mechanical and thermodynamic testing of the encapsulated materials, development of a rate based model of the absorber, and the design of a laboratory scale unit to test the encapsulated particles for CO 2 capture ability and efficiency. We show that the IL/PCIL materials can be successfully encapsulated, that they retain CO 2 uptake capacity, and that the uptake rates are increased relative to a stagnant sample of IL liquid or PCIL powder.« less

Encapsulating Cytochrome c in Silica Aerogel Nanoarchitectures without Metal Nanoparticles while Retaining Gas-phase Bioactivity

PubMed Central

Harper-Leatherman, Amanda S.; Pacer, Elizabeth R.; Kosciuszek, Nina D.

2016-01-01

Applications such as sensors, batteries, and fuel cells have been improved through the use of highly porous aerogels when functional compounds are encapsulated within the aerogels. However, few reports on encapsulating proteins within sol–gels that are processed to form aerogels exist. A procedure for encapsulating cytochrome c (cyt. c) in silica (SiO2) sol-gels that are supercritically processed to form bioaerogels with gas-phase activity for nitric oxide (NO) is presented. Cyt. c is added to a mixed silica sol under controlled protein concentration and buffer strength conditions. The sol mixture is then gelled and the liquid filling the gel pores is replaced through a series of solvent exchanges with liquid carbon dioxide. The carbon dioxide is brought to its critical point and vented off to form dry aerogels with cyt. c encapsulated inside. These bioaerogels are characterized with UV-visible spectroscopy and circular dichroism spectroscopy and can be used to detect the presence of gas-phase nitric oxide. The success of this procedure depends on regulating the cyt. c concentration and the buffer concentration and does not require other components such as metal nanoparticles. It may be possible to encapsulate other proteins using a similar approach making this procedure important for potential future bioanalytical device development. PMID:26967257

Encapsulating Cytochrome c in Silica Aerogel Nanoarchitectures without Metal Nanoparticles while Retaining Gas-phase Bioactivity.

PubMed

Harper-Leatherman, Amanda S; Pacer, Elizabeth R; Kosciuszek, Nina D

2016-03-01

Applications such as sensors, batteries, and fuel cells have been improved through the use of highly porous aerogels when functional compounds are encapsulated within the aerogels. However, few reports on encapsulating proteins within sol-gels that are processed to form aerogels exist. A procedure for encapsulating cytochrome c (cyt. c) in silica (SiO2) sol-gels that are supercritically processed to form bioaerogels with gas-phase activity for nitric oxide (NO) is presented. Cyt. c is added to a mixed silica sol under controlled protein concentration and buffer strength conditions. The sol mixture is then gelled and the liquid filling the gel pores is replaced through a series of solvent exchanges with liquid carbon dioxide. The carbon dioxide is brought to its critical point and vented off to form dry aerogels with cyt. c encapsulated inside. These bioaerogels are characterized with UV-visible spectroscopy and circular dichroism spectroscopy and can be used to detect the presence of gas-phase nitric oxide. The success of this procedure depends on regulating the cyt. c concentration and the buffer concentration and does not require other components such as metal nanoparticles. It may be possible to encapsulate other proteins using a similar approach making this procedure important for potential future bioanalytical device development.

Assessing the Causes of Encapsulant Delamination in PV Modules

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

Wohlgemuth, John H.; Hacke, Peter; Bosco, Nick

Delamination of the encapsulant is one of the most prevalent PV module field failures. This paper will present examples of various types of delaminations that have been observed in the field. It will then discuss the development of accelerated stress tests designed to duplicate those field failures and thus provide tools for avoiding them in the future.

How Do Physicians Become Medical Experts? A Test of Three Competing Theories: Distinct Domains, Independent Influence and Encapsulation Models

ERIC Educational Resources Information Center

Violato, Claudio; Gao, Hong; O'Brien, Mary Claire; Grier, David; Shen, E.

2018-01-01

The distinction between basic sciences and clinical knowledge which has led to a theoretical debate on how medical expertise is developed has implications for medical school and lifelong medical education. This longitudinal, population based observational study was conducted to test the fit of three theories--knowledge encapsulation, independent…

Development of Poly(Ethylene Glycol) Hydrogels for Salivary Gland Tissue Engineering Applications

PubMed Central

Shubin, Andrew D.; Felong, Timothy J.; Graunke, Dean; Ovitt, Catherine E.

2015-01-01

More than 40,000 patients are diagnosed with head and neck cancers annually in the United States with the vast majority receiving radiation therapy. Salivary glands are irreparably damaged by radiation therapy resulting in xerostomia, which severely affects patient quality of life. Cell-based therapies have shown some promise in mouse models of radiation-induced xerostomia, but they suffer from insufficient and inconsistent gland regeneration and accompanying secretory function. To aid in the development of regenerative therapies, poly(ethylene glycol) hydrogels were investigated for the encapsulation of primary submandibular gland (SMG) cells for tissue engineering applications. Different methods of hydrogel formation and cell preparation were examined to identify cytocompatible encapsulation conditions for SMG cells. Cell viability was much higher after thiol-ene polymerizations compared with conventional methacrylate polymerizations due to reduced membrane peroxidation and intracellular reactive oxygen species formation. In addition, the formation of multicellular microspheres before encapsulation maximized cell–cell contacts and increased viability of SMG cells over 14-day culture periods. Thiol-ene hydrogel-encapsulated microspheres also promoted SMG proliferation. Lineage tracing was employed to determine the cellular composition of hydrogel-encapsulated microspheres using markers for acinar (Mist1) and duct (Keratin5) cells. Our findings indicate that both acinar and duct cell phenotypes are present throughout the 14 day culture period. However, the acinar:duct cell ratios are reduced over time, likely due to duct cell proliferation. Altogether, permissive encapsulation methods for primary SMG cells have been identified that promote cell viability, proliferation, and maintenance of differentiated salivary gland cell phenotypes, which allows for translation of this approach for salivary gland tissue engineering applications. PMID:25762214

Successful Resolution of Recurrent Clostridium difficile Infection using Freeze-Dried, Encapsulated Fecal Microbiota; Pragmatic Cohort Study

PubMed Central

Staley, Christopher; Hamilton, Matthew J.; Vaughn, Byron P.; Graiziger, Carolyn T.; Newman, Krista M.; Kabage, Amanda J.; Sadowsky, Michael J.; Khoruts, Alexander

2017-01-01

OBJECTIVES Fecal microbiota transplantation (FMT) is increasingly being used for treatment of recurrent Clostridium difficile infection (R-CDI) that cannot be cured with antibiotics alone. In addition, FMT is being investigated for a variety of indications where restoration or restructuring of the gut microbial community is hypothesized to be beneficial. We sought to develop a stable, freeze-dried encapsulated preparation of standardized fecal microbiota that can be used for FMT with ease and convenience in clinical practice and research. METHODS We systematically developed a lyophilization protocol that preserved the viability of bacteria across the taxonomic spectrum found in fecal microbiota and yielded physicochemical properties that enabled consistent encapsulation. We also treated a cohort of R-CDI patients with a range of doses of encapsulated microbiota and analyzed the associated changes in the fecal microbiome of the recipients. RESULTS The optimized lyophilized preparation satisfied all our preset goals for physicochemical properties, encapsulation ease, stability at different temperatures, and microbiota viability in vitro and in vivo (germ-free mice). The capsule treatment was administered to 49 patients. Overall, 43/49 (88%) of patients achieved a clinical success, defined as no recurrence of CDI over 2 months. Analysis of the fecal microbiome demonstrated near normalization of the fecal microbial community by 1 month following FMT treatment. The simplest protocol using the lowest dose (2.1–2.5×1011 bacteria in 2–3 capsules) without any colon purgative performed equally well in terms of clinical outcomes and microbiota engraftment. CONCLUSIONS A single administration of encapsulated, freeze-dried fecal microbiota from a healthy donor was highly successful in treating antibiotic-refractory R-CDI syndrome. PMID:28195180

Physico-chemical state influences in vitro release profile of curcumin from pectin beads.

PubMed

Nguyen, An Thi-Binh; Winckler, Pascale; Loison, Pauline; Wache, Yves; Chambin, Odile

2014-09-01

Curcumin is a polyphenolic compound with diverse effects interesting to develop health benefit products but its formulation in functional foods or in food supplement is hampered by its poor water solubility and susceptibility to alkaline conditions, light, oxidation and heat. Encapsulation of curcumin could be a mean to overcome these difficulties. In this paper, curcumin was encapsulated by ionotropic gelation method in low methoxyl pectin beads associated with different surfactants: Solutol(®), Transcutol(®) and sodium caseinate. After encapsulation, physico-chemical properties of encapsulated curcumin such as its solubility, physical state, tautomeric forms and encapsulation efficiency as well as encapsulation yield were characterized. In vitro dissolution of curcumin from beads displayed different kinetic profiles according to bead composition due to different matrix network. As Solutol(®) was a good solvent for curcumin, the drug was present into amorphous form in these beads inducing a rapid release of curcumin in the simulated digestive fluids. In contrast, drug release was slower from sodium caseinate beads since curcumin was not totally dissolved during the manufacturing process. Moreover, the FLIM studies showed that a part of curcumin was encapsulated in caseinate micelles and that 34% of this drug was in keto form which may delay the curcumin release. The Transcutol beads showed also a slow drug release because of the low curcumin solubility and the high density of the matrix. Copyright © 2014 Elsevier B.V. All rights reserved.

Facile Preparation of Drug-Loaded Tristearin Encapsulated Superparamagnetic Iron Oxide Nanoparticles Using Coaxial Electrospray Processing.

PubMed

Rasekh, Manoochehr; Ahmad, Zeeshan; Cross, Richard; Hernández-Gil, Javier; Wilton-Ely, James D E T; Miller, Philip W

2017-06-05

Naturally occurring polymers are promising biocompatible materials that have many applications for emerging therapies, drug delivery systems, and diagnostic agents. The handling and processing of such materials still constitutes a major challenge, which can limit the full exploitation of their properties. This study explores an ambient environment processing technique: coaxial electrospray (CO-ES) to encapsulate genistein (an isoflavonoid and model drug), superparamagnetic iron oxide nanoparticles (SPIONs, 10-15 nm), and a fluorophore (BODIPY) into a layered (triglyceride tristearin shell) particulate system, with a view to constructing a theranostic agent. Mode mapping of CO-ES led to an optimized atomization engineering window for stable jetting, leading to encapsulation of SPIONs within particles of diameter 0.65-1.2 μm and drug encapsulation efficiencies of around 92%. Electron microscopy was used to image the encapsulated SPIONs and confirm core-shell triglyceride encapsulation in addition to further physicochemical characterization (AFM, FTIR, DSC, and TGA). Cell viability assays (MTT, HeLa cells) were used to determine optimal SPION loaded particles (∼1 mg/mL), while in vitro release profile experiments (PBS, pH = 7.4) demonstrate a triphasic release profile. Further cell studies confirmed cell uptake and internalization at selected time points (t = 1, 2, and 4 h). The results suggest potential for using the CO-ES technique as an efficient way to encapsulate SPIONs together with sensitive drugs for the development of multimodal particles that have potential application for combined imaging and therapy.

3D packaging of a microfluidic system with sensory applications

NASA Astrophysics Data System (ADS)

Morrissey, Anthony; Kelly, Gerard; Alderman, John C.

1997-09-01

Among the main benefits of microsystem technology are its contributions to cost reductio, reliability and improved performance. however, the packaging of microsystems, and particularly microsensor, has proven to be one of the biggest limitations to their commercialization and the packaging of silicon sensor devices can be the most costly part of their fabrication. This paper describes the integration of 3D packaging of a microsystem. Central to the operation of the 3D demonstrator is a micromachined silicon membrane pump to supply fluids to a sensing chamber constructed about the active area of a sensor chip. This chip carries ISFET based chemical sensors, pressure sensors and thermal sensors. The electronics required for controlling and regulating the activity of the various sensors ar also available on this chip and as other chips in the 3D assembly. The demonstrator also contains a power supply module with optical fiber interconnections. All of these modules are integrated into a single plastic- encapsulated 3D vertical multichip module. The reliability of such a structure, initially proposed by Val was demonstrated by Barrett et al. An additional module available for inclusion in some of our assemblies is a test chip capable of measuring the packaging-induced stress experienced during and after assembly. The packaging process described produces a module with very high density and utilizes standard off-the-shelf components to minimize costs. As the sensor chip and micropump include micromachined silicon membranes and microvalves, the packaging of such structures has to allow consideration for the minimization of the packaging-induced stresses. With this in mind, low stress techniques, including the use of soft glob-top materials, were employed.

On Field-Effect Photovoltaics: Gate Enhancement of the Power Conversion Efficiency in a Nanotube/Silicon-Nanowire Solar Cell.

PubMed

Petterson, Maureen K; Lemaitre, Maxime G; Shen, Yu; Wadhwa, Pooja; Hou, Jie; Vasilyeva, Svetlana V; Kravchenko, Ivan I; Rinzler, Andrew G

2015-09-30

Recent years have seen a resurgence of interest in crystalline silicon Schottky junction solar cells distinguished by the use of low density of electronic states (DOS) nanocarbons (nanotubes, graphene) as the metal contacting the Si. Recently, unprecedented modulation of the power conversion efficiency in a single material system has been demonstrated in such cells by the use of electronic gating. The gate field induced Fermi level shift in the low-DOS carbon serves to enhance the junction built-in potential, while a gate field induced inversion layer at the Si surface, in regions remote from the junction, keeps the photocarriers well separated there, avoiding recombination at surface traps and defects (a key loss mechanism). Here, we extend these results into the third dimension of a vertical Si nanowire array solar cell. A single wall carbon nanotube layer engineered to contact virtually each n-Si nanowire tip extracts the minority carriers, while an ionic liquid electrolytic gate drives the nanowire body into inversion. The enhanced light absorption of the vertical forest cell, at 100 mW/cm(2) AM1.5G illumination, results in a short-circuit current density of 35 mA/cm(2) and associated power conversion efficiency of 15%. These results highlight the use of local fields as opposed to surface passivation as a means of avoiding front surface recombination. A deleterious electrochemical reaction of the silicon due to the electrolyte gating is shown to be caused by oxygen/water entrained in the ionic liquid electrolyte. While encapsulation can avoid the issue, a nonencapsulation-based approach is also implemented.

Temperature responsive porous silicon nanoparticles for cancer therapy - spatiotemporal triggering through infrared and radiofrequency electromagnetic heating.

PubMed

Tamarov, Konstantin; Xu, Wujun; Osminkina, Liubov; Zinovyev, Sergey; Soininen, Pasi; Kudryavtsev, Andrey; Gongalsky, Maxim; Gaydarova, Azha; Närvänen, Ale; Timoshenko, Victor; Lehto, Vesa-Pekka

2016-11-10

One critical functionality of the carrier system utilized in targeted drug delivery is its ability to trigger the release of the therapeutic cargo once the carrier has reached its target. External triggering is an alluring approach as it can be applied in a precise spatiotemporal manner. In the present study, we achieved external triggering through the porous silicon (PSi) nanoparticles (NPs) by providing a pulse of infrared or radiofrequency radiation. The NPs were grafted with a temperature responsive polymer whose critical temperature was tailored to be slightly above 37°C. The polymer coating improved the biocompatibility of the NPs significantly in comparison with their uncoated counterparts. Radiation induced a rapid temperature rise, which resulted in the collapse of the polymer chains facilitating the cargo release. Both infrared and radiofrequency radiation were able to efficiently trigger the release of the encapsulated drug in vitro and induce significant cell death in comparison to the control groups. Radiofrequency radiation was found to be more efficient in vitro, and the treatment efficacy was verified in vivo in a lung carcinoma (3LL) mice model. After a single intratumoral administration of the carrier system combined with radiofrequency radiation, there was clear suppression of the growth of the carcinoma and a prolongation of the survival time of the animals. The temperature responsive (TR) polymer grafted on the surface of porous silicon nanoparticles (PSi NPs) changes its conformation in response to the heating induced by infrared or radiofrequency radiation. The conformation change allows the loaded doxorubicin to escape from the pores, achieving controlled drug release from TR PSi NPs, which displayed efficacy against malignant cells both in vitro and in vivo. Copyright © 2016 Elsevier B.V. All rights reserved.

On Field-Effect Photovoltaics: Gate Enhancement of the Power Conversion Efficiency in a Nanotube/Silicon-Nanowire Solar Cell

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

Petterson, Maureen K.; Lemaitre, Maxime G.; Shen, Yu

Recent years have seen a resurgence of interest in crystalline silicon Schottky junction solar cells distinguished by the use of low density of electronic states (DOS) nanocarbons (nanotubes, graphene) as the metal contacting the Si. Recently, unprecedented modulation of the power conversion efficiency in a single material system has been demonstrated in such cells by the use of electronic gating. The gate field induced Fermi level shift in the low-DOS carbon serves to enhance the junction built-in potential, while a gate field induced inversion layer at the Si surface, in regions remote from the junction, keeps the photocarriers well separatedmore » there, avoiding recombination at surface traps and defects (a key loss mechanism). Here, we extend these results into the third dimension of a vertical Si nanowire array solar cell. A single wall carbon nanotube layer engineered to contact virtually each n-Si nanowire tip extracts the minority carriers, while an ionic liquid electrolytic gate drives the nanowire body into inversion. The enhanced light absorption of the vertical forest cell, at 100 mW/cm 2 AM1.5G illumination, results in a short-circuit current density of 35 mA/cm 2 and associated power conversion efficiency of 15%. These results highlight the use of local fields as opposed to surface passivation as a means of avoiding front surface recombination. Finally, a deleterious electrochemical reaction of the silicon due to the electrolyte gating is shown to be caused by oxygen/water entrained in the ionic liquid electrolyte. While encapsulation can avoid the issue, a nonencapsulation-based approach is also implemented.« less

On Field-Effect Photovoltaics: Gate Enhancement of the Power Conversion Efficiency in a Nanotube/Silicon-Nanowire Solar Cell

DOE PAGES

Petterson, Maureen K.; Lemaitre, Maxime G.; Shen, Yu; ...

2015-09-09

Recent years have seen a resurgence of interest in crystalline silicon Schottky junction solar cells distinguished by the use of low density of electronic states (DOS) nanocarbons (nanotubes, graphene) as the metal contacting the Si. Recently, unprecedented modulation of the power conversion efficiency in a single material system has been demonstrated in such cells by the use of electronic gating. The gate field induced Fermi level shift in the low-DOS carbon serves to enhance the junction built-in potential, while a gate field induced inversion layer at the Si surface, in regions remote from the junction, keeps the photocarriers well separatedmore » there, avoiding recombination at surface traps and defects (a key loss mechanism). Here, we extend these results into the third dimension of a vertical Si nanowire array solar cell. A single wall carbon nanotube layer engineered to contact virtually each n-Si nanowire tip extracts the minority carriers, while an ionic liquid electrolytic gate drives the nanowire body into inversion. The enhanced light absorption of the vertical forest cell, at 100 mW/cm 2 AM1.5G illumination, results in a short-circuit current density of 35 mA/cm 2 and associated power conversion efficiency of 15%. These results highlight the use of local fields as opposed to surface passivation as a means of avoiding front surface recombination. Finally, a deleterious electrochemical reaction of the silicon due to the electrolyte gating is shown to be caused by oxygen/water entrained in the ionic liquid electrolyte. While encapsulation can avoid the issue, a nonencapsulation-based approach is also implemented.« less

Silicon-on Ceramic Process: Silicon Sheet Growth and Device Development for the Large-area Silicon Sheet and Cell Development Tasks of the Low-cost Solar Array Project

NASA Technical Reports Server (NTRS)

Chapman, P. W.; Zook, J. D.; Heaps, J. D.; Grung, B. L.; Koepke, B.; Schuldt, S. B.

1979-01-01

The technical and economic feasibility of producing solar cell-quality silicon was investigated. This was done by coating one surface of carbonized ceramic substrates with a thin layer of large-grain polycrystalline silicon from the melt. Significant progress in the following areas was demonstrated: (1) fabricating a 10 sq cm cell having 9.9 percent conversion efficiency; (2) producing a 225 sq cm layer of sheet silicon; and (3) obtaining 100 microns thick coatings at pull speed of 0.15 cm/sec, although approximately 50 percent of the layer exhibited dendritic growth.

Improved fibronectin-immobilized fibrinogen microthreads for the attachment and proliferation of fibroblasts

PubMed Central

Rajangam, Thanavel; An, Seong Soo A

2013-01-01

The aim of this study was to fabricate fibrinogen (Fbg) microfibers with different structural characteristics for the development of 3-D tissue-engineering scaffolds. Fabricated Fbg microfibers were investigated for their biomolecule encapsulation, cell adhesion, and proliferations. Microfibers with three different concentrations of Fbg (5, 10, and 15 wt%) were prepared by a gel solvent-extraction method using a silicone rubber tube. Fbg microfibers were covalently modified with fibronectin (FN) by using water-soluble 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide as the cross-linking agent. Fbg microfibers were characterized by their FN cross-linking properties, structural morphology, and in vitro degradation. Furthermore, FN/Fbg microfibers were evaluated for cell attachment and proliferation. The bio-compatibility and cell proliferation of the microfibers were assessed by measuring adenosine triphosphate activity in C2C12 fibroblast cells. Cell attachment and proliferation on microfibers were further examined using fluorescence and scanning electron microscopic images. FN loading on the microfibers was confirmed by fluorescence and infrared spectroscopy. Surface morphology was characterized by scanning electron microscopy, and showed highly aligned nanostructures for fibers made with 15 wt% Fbg, a more porous structure for fibers made with 10 wt% Fbg, and a less porous structure for those made with 5 wt% Fbg. Controlled biodegradation of the fiber was observed for 8 weeks by using an in vitro proteolytic degradation assay. Fbg microfibers with highly aligned nanostructures (15 wt%) showed enhanced biomolecule encapsulation, as well as higher cell adhesion and proliferation than another two types of FN/Fbg fibers (5 and 10 wt%) and unmodified Fbg fibers. The promising results obtained from the present study reveal that optimal structure of Fbg microfibers could be used as a potential substratum for growth factors or drug release, especially in wound healing and vascular tissue engineering, in which fibers could be applied to promote and orient cell adhesion and proliferation. PMID:23515334

Oil encapsulation in core-shell alginate capsules by inverse gelation II: comparison between dripping techniques using W/O or O/W emulsions.

PubMed

Martins, Evandro; Poncelet, Denis; Rodrigues, Ramila Cristiane; Renard, Denis

2017-09-01

In the first part of this article, it was described an innovative method of oil encapsulation from dripping-inverse gelation using water-in-oil (W/O) emulsions. It was noticed that the method of oil encapsulation was quite different depending on the emulsion type (W/O or oil-in-water (O/W)) used and that the emulsion structure (W/O or O/W) had a high impact on the dripping technique and the capsules characteristics. The objective of this article was to elucidate the differences between the dripping techniques using both emulsions and compare the capsule properties (mechanical resistance and release of actives). The oil encapsulation using O/W emulsions was easier to perform and did not require the use of emulsion destabilisers. However, capsules produced from W/O emulsions were more resistant to compression and showed the slower release of actives over time. The findings detailed here widened the knowledge of the inverse gelation and gave opportunities to develop new techniques of oil encapsulation.

Diffusion-Limited Cargo Loading of an Engineered Protein Container.

PubMed

Zschoche, Reinhard; Hilvert, Donald

2015-12-30

The engineered bacterial nanocompartment AaLS-13 is a promising artificial encapsulation system that exploits electrostatic interactions for cargo loading. In order to study its ability to take up and retain guests, a pair of fluorescent proteins was developed which allows spectroscopic determination of the extent of encapsulation by Förster resonance energy transfer (FRET). The encapsulation process is generally complete within a second, suggesting low energetic barriers for proteins to cross the capsid shell. Formation of intermediate aggregates upon mixing host and guest in vitro complicates capsid loading at low ionic strength, but can be sidestepped by increasing salt concentrations or diluting the components. Encapsulation of guests is completely reversible, and the position of the equilibrium is easily tuned by varying the ionic strength. These results, which challenge the notion that AaLS-13 is a continuous rigid shell, provide valuable information about cargo loading that will guide ongoing efforts to engineer functional host-guest complexes. Moreover, it should be possible to adapt the protein FRET pair described in this report to characterize functional capsid-cargo complexes generated by other encapsulation systems.

Silicon on ceramic process. Silicon sheet growth development for the large-area silicon sheet task of the low-cost silicon solar array project

NASA Technical Reports Server (NTRS)

Zook, J. D.; Heaps, J. D.; Maciolek, R. B.; Koepke, B. G.; Butter, C. D.; Schuldt, S. B.

1977-01-01

The technical and economic feasibility of producing solar-cell-quality sheet silicon was investigated. The sheets were made by coating one surface of carbonized ceramic substrates with a thin layer of large-grain polycrystalline silicon from the melt. Significant progress was made in all areas of the program.

Development of standardized specifications for silicon solar cells

NASA Technical Reports Server (NTRS)

Scott-Monck, J. A.

1977-01-01

A space silicon solar cell assembly (cell and coverglass) specification aimed at standardizing the diverse requirements of current cell or assembly specifications was developed. This specification was designed to minimize both the procurement and manufacturing costs for space qualified silicon solar cell assembilies. In addition, an impact analysis estimating the technological and economic effects of employing a standardized space silicon solar cell assembly was performed.

Fabrication of hemispherical liquid encapsulated structures based on droplet molding

NASA Astrophysics Data System (ADS)

Ishizuka, Hiroki; Miki, Norihisa

2015-12-01

We have developed and demonstrated a method for forming spherical structures of a thin polydimethylsiloxane (PDMS) membrane encapsulating a liquid. Liquid encapsulation can enhance the performance of microelectromechanical systems (MEMS) devices by providing deformability and improved dielectric properties. Parylene deposition and wafer bonding are applied to encapsulate liquid into a MEMS device. In parylene deposition, a parylene membrane is directly formed onto a liquid droplet. However, since the parylene membrane is stiff, the membrane is fragile. Although wafer bonding can encapsulate liquid between two substrates, the surface of the fabricated structure is normally flat. We propose a new liquid encapsulation method by dispensing liquid droplets. At first, a 20 μl PDMS droplet is dispensed on ethylene glycol. A 70 μl glycerin droplet is dispensed into a PDMS casting solution layer. The droplet forms a layer on heated ethylene glycol. Glycerin and ethylene glycol are chosen for their high boiling points. Additionally, a glycerin droplet is dispensed on the layer and surrounded by a thin PDMS casting solution film. The film is baked for 1 h at 75 °C. As the result, a structure encapsulating a liquid in a flexible PDMS membrane is obtained. We investigate the effects of the volume, surface tension, and guide thickness on the shape of the formed structures. We also evaluated the effect of the structure diameter on miniaturization. The structure can be adapted for various functions by changing the encapsulated liquid. We fabricated a stiffness-tunable structure by dispensing a magnetorheoligical fluid droplet with a stiffness that can be changed by an external magnetic field. We also confirmed that the proposed structure can produce stiffness differences that are distinguishable by humans.

Characterization of Encapsulated and Noncapsulated Haemophilus influenzae and Determination of Phylogenetic Relationships by Multilocus Sequence Typing

PubMed Central

Meats, Emma; Feil, Edward J.; Stringer, Suzanna; Cody, Alison J.; Goldstein, Richard; Kroll, J. Simon; Popovic, Tanja; Spratt, Brian G.

2003-01-01

A multilocus sequence typing (MLST) scheme has been developed for the unambiguous characterization of encapsulated and noncapsulated Haemophilus influenzae isolates. The sequences of internal fragments of seven housekeeping genes were determined for 131 isolates, comprising a diverse set of 104 serotype a, b, c, d, e, and f isolates and 27 noncapsulated isolates. Many of the encapsulated isolates had previously been characterized by multilocus enzyme electrophoresis (MLEE), and the validity of the MLST scheme was established by the very similar clustering of isolates obtained by these methods. Isolates of serotypes c, d, e, and f formed monophyletic groups on a dendrogram constructed from the differences in the allelic profiles of the isolates, whereas there were highly divergent lineages of both serotype a and b isolates. Noncapsulated isolates were distinct from encapsulated isolates and, with one exception, were within two highly divergent clusters. The relationships between the major lineages of encapsulated H. influenzae inferred from MLEE data could not be discerned on a dendrogram constructed from differences in the allelic profiles, but were apparent on a tree reconstructed from the concatenated nucleotide sequences. Recombination has not therefore completely eliminated phylogenetic signal, and in support of this, for encapsulated isolates, there was significant congruence between many of the trees reconstructed from the sequences of the seven individual loci. Congruence was less apparent for noncapsulated isolates, suggesting that the impact of recombination is greater among noncapsulated than encapsulated isolates. The H. influenzae MLST scheme is available at www.mlst.net, it allows any isolate to be compared with those in the MLST database, and (for encapsulated isolates) it assigns isolates to their phylogenetic lineage, via the Internet. PMID:12682154

Influence of charge on encapsulation and release behavior of small molecules in self-assembled layer-by-layer microcapsules.

PubMed

Mandapalli, Praveen K; Labala, Suman; Vanamala, Deekshith; Koranglekar, Manali P; Sakimalla, Lakshmi A; Venuganti, Venkata Vamsi K

2014-12-01

The objective of this study is to investigate the influence of charge of model small molecules on their encapsulation and release behavior in layer-by-layer microcapsules (LbL-MC). Poly(styrene sulfonate) and poly(ethylene imine) were sequentially adsorbed on calcium carbonate sacrificial templates to prepare LbL-MC. Model molecules with varying charge, anionic - ascorbic acid, cationic - imatinib mesylate (IM) and neutral - 5-fluorouracil were encapsulated in LbL-MC. Free and encapsulated LbL-MC were characterized using zetasizer, FTIR spectroscope and differential scanning calorimeter. The influence of IM-loaded LbL-MC on cell viability was studied in B16F10 murine melanoma cells. Furthermore, biodistribution of IM-loaded LbL-MC with and without PEGylation was studied in BALB/c mice. Results showed spherical LbL-MC of 3.0 ± 0.4 μm diameter. Encapsulation efficiency of LbL-MC increased linearly (R(2 )= 0.89-0.99) with the increase in solute concentration. Increase in pH from 2 to 6 increased the encapsulation of charged molecules in LbL-MC. Charged molecules showed greater encapsulation efficiency in LbL-MC compared with neutral molecule. In vitro release kinetics showed Fickian and non-Fickian diffusion of small molecules, depending on the nature of molecular interactions with LbL-MC. At 50 μM concentration, free IM showed significantly (p < 0.05) more cytotoxicity compared with IM-loaded LbL-MC. Biodistribution studies showed that PEGylation of LbL-MC decreased the liver and spleen uptake of IM-encapsulated LbL-MC. In conclusion, LbL-MC can be developed as a potential carrier for small molecules depending on their physical and chemical properties.

Proton Mediated Chemistry and Catalysis in a Self-Assembled Supramolecular Host

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

Pluth, Michael; Bergman, Robert; Raymond, Kenneth

2009-04-10

Synthetic supramolecular host assemblies can impart unique reactivity to encapsulated guest molecules. Synthetic host molecules have been developed to carry out complex reactions within their cavities, despite the fact that they lack the type of specifically tailored functional groups normally located in the analogous active sites of enzymes. Over the past decade, the Raymond group has developed a series of self-assembled supramolecules and the Bergman group has developed and studied a number of catalytic transformations. In this Account, we detail recent collaborative work between these two groups, focusing on chemical catalysis stemming from the encapsulation of protonated guests and expandingmore » to acid catalysis in basic solution. We initially investigated the ability of a water-soluble, self-assembled supramolecular host molecule to encapsulate protonated guests in its hydrophobic core. Our study of encapsulated protonated amines revealed rich host-guest chemistry. We established that self-exchange (that is, in-out guest movement) rates of protonated amines were dependent on the steric bulk of the amine rather than its basicity. The host molecule has purely rotational tetrahedral (T) symmetry, so guests with geminal N-methyl groups (and their attendant mirror plane) were effectively desymmetrized; this allowed for the observation and quantification of the barriers for nitrogen inversion followed by bond rotation. Furthermore, small nitrogen heterocycles, such as N-alkylaziridines, N-alkylazetidines, and N-alkylpyrrolidines, were found to be encapsulated as proton-bound homodimers or homotrimers. We further investigated the thermodynamic stabilization of protonated amines, showing that encapsulation makes the amines more basic in the cavity. Encapsulation raises the effective basicity of protonated amines by up to 4.5 pK{sub a} units, a difference almost as large as that between the moderate and strong bases carbonate and hydroxide. The thermodynamic stabilization of protonated guests was translated into chemical catalysis by taking advantage of the potential for accelerating reactions that take place via positively charged transition states, which could be potentially stabilized by encapsulation. Orthoformates, generally stable in neutral or basic solution, were found to be suitable substrates for catalytic hydrolysis by the assembly. Orthoformates small enough to undergo encapsulation were readily hydrolyzed by the assembly in basic solution, with rate acceleration factors up to 3900 compared with those of the corresponding uncatalyzed reactions. Furthering the analogy to enzymes that obey Michaelis-Menten kinetics, we observed competitive inhibition with the inhibitor NPr{sub 4}{sup +}, thereby confirming that the interior cavity of the assembly was the active site for catalysis. Mechanistic studies revealed that the assembly is required for catalysis and that the rate-limiting step of the reaction involves proton transfer from hydronium to the encapsulated substrate. Encapsulation in the assembly changes the orthoformate hydrolysis from an A-1 mechanism (in which decomposition of the protonated substrate is the rate-limiting step) to an A-S{sub E}2 mechanism (in which proton transfer is the rate-limiting step). The study of hydrolysis in the assembly was next extended to acetals, which were also catalytically hydrolyzed by the assembly in basic solution. Acetal hydrolysis changed from the A-1 mechanism in solution to an A-2 mechanism inside the assembly, where attack of water on the protonated substrate is rate limiting. This work provides rare examples of assembly-catalyzed reactions that proceed with substantial rate accelerations despite the absence of functional groups in the cavity and with mechanisms fully elucidated by quantitative kinetic studies.« less

Lifetime Improvement of Organic Light Emitting Diodes using LiF Thin Film and UV Glue Encapsulation

NASA Astrophysics Data System (ADS)

Huang, Jian-Ji; Su, Yan-Kuin; Chang, Ming-Hua; Hsieh, Tsung-Eong; Huang, Bohr-Ran; Wang, Shun-Hsi; Chen, Wen-Ray; Tsai, Yu-Sheng; Hsieh, Huai-En; Liu, Mark O.; Juang, Fuh-Shyang

2008-07-01

This work demonstrates the use of lithium fluoride (LiF) as a passivation layer and a newly developed UV glue for encapsulation on the LiF passivation layer to enhance the stability of organic light-emitting devices (OLEDs). Devices with double protective layers showed a 25-fold increase in operational lifetime compared to those without any packaging layers. LiF has a low melting point and insulating characteristics and it can be adapted as both a protective layer and pre-encapsulation film. The newly developed UV glue has a fast curing time of only 6 s and can be directly spin-coated onto the surface of the LiF passivation layer. The LiF thin film plus spin-coated UV glue is a simple packaging method that reduces the fabrication costs of OLEDs.

Tracer-Encapsulated Solid Pellet (TESPEL) Injection System for the TJ-II Stellarator

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

Tamura, N.; McCarthy, K. J.; Hayashi, H.

2016-01-01

A tracer-encapsulated solid pellet (TESPEL) injection system for the TJ-II stellarator was recently developed. In order to reduce the time and cost for the development, we combined a TESPEL injector provided by National Institute for Fusion Science with an existing TJ-II cryogenic pellet injection system. Consequently, the TESPEL injection into the TJ-II plasma was successfully achieved, which was confirmed by several pellet diagnostics including a normal-incidence spectrometer for monitoring a tracer impurity behavior.

Development of Octyl Methoxy Cinnamates (OMC)/Silicon Dioxide (SiO₂) Nanoparticles by Sol-Gel Emulsion Method.

PubMed

Wu, Pey-Shiuan; Lee, Yi-Ching; Kuo, Yi-Ching; Lin, Chih-Chien

2017-12-07

Although octyl methoxy cinnamates (OMC) is the most used Ultraviolet B (UVB) filter in sunscreen, it has poor light stability in emulsion system. In this study, OMC/SiO₂ nanoparticles were prepared via sol-gel emulsion method. Tetraethoxy silane (TEOS) was used as the silica source to encapsulate OMC. Modification of experimental parameters such as stirring speed of condensation reaction and emulsion condition, pH value of acid-catalyzed, surfactant and different percentage of TEOS and OMC, adding of OMC and surfactant to different phase may affect the particle size, and yield and entrapment efficiency in preparation process of OMC/SiO₂ nanoparticles. Concluding all the parameter, we found that when condensation reaction and emulsion conditions are at 1000 rpm, pH 1.5, Span 80/Tween 20, TEOS/OMC ratios 1:1, OMC and surfactants added in oil phase, resulting in smaller particle sizes 476.5 nm, higher yield 95.8%, and higher entrapment efficiency 61.09%. Fourier transform infrared (FTIR) analysis demonstrated that OMC/SiO₂ nanoparticles were successfully prepared. In vitro release profile supposed that OMC/SiO₂ nanoparticles can delay OMC releasing and had 60.83% decreasing of cumulative amount. Therefore, the OMC/SiO₂ nanoparticles have the potential to develop as new sunscreen materials in the use for cosmetics field in the future.

Glass breaking strength: The role of surface flaws and treatments

NASA Technical Reports Server (NTRS)

Moore, D.

1985-01-01

Although the intrinsic strength of silicon dioxide glass is of the order of 10 to the 6th power lb/sq in, the practical strength is roughly two orders of magnitude below this theoretical limit, and depends almost entirely on the surface condition of the glass, that is, the number and size of flaws and the residual surface compression (temper) in the glass. Glass parts always fail in tension when these flaws grow under sustained loading to some critical size. Research associated with glass encapsulated crystalline-Si photovoltaic (PV) modules has greatly expanded our knowledge of glass breaking strength and developed sizeable data base for commercially available glass types. A detailed design algorithm is developed for thickness sizing of rectangular glass plates subject to pressure loads. Additional studies examine the strength of glass under impact loading conditions such as that caused by hail. Although the fundamentals of glass breakage are directly applicable to thin film modules, the fracture strength of typical numerical glass must be replaced with data that reflect the high temperature tin oxide processing, laser scribing, and edge processing peculiar to thin film modules. The fundamentals of glass breakage applicable to thin film modules and preliminary fracture strength data for a variety of 1 ft square glass specimens representing preprocessed and post processed sheets from current amorphous-Si module manufacturers are presented.

Applications of the silicon wafer direct-bonding technique to electron devices

NASA Astrophysics Data System (ADS)

Furukawa, K.; Nakagawa, A.

1990-01-01

A silicon wafer direct-bonding (SDB) technique has been developed. A pair of bare silicon wafers, as well as an oxidized wafer pair, are bonded throughout the wafer surfaces without any bonding material. Conventional semiconductor device processes can be used for the bonded wafers, since the bonded interface is stable thermally, chemically, mechanically and electrically. Therefore, the SDB technique is very attractive, and has been applied to several kinds of electron devices. Bare silicon to bare silicon bonding is an alternative for epitaxial growth. A thick, high quality and high resistivity layer on a low resistivity substrate was obtained without autodoping. 1800 V insulated gate bipolar transistors were developed using these SDB wafers. No electrical resistance was observed at the bonded bare silicon interfaces. If oxidized wafers are bonded, the two wafers are electrically isolated, providing silicon on insulator (SOI) wafers. Dielectrically isolated photodiode arrays were fabricated on the SOI wafers and 500 V power IC's are now being developed.

Transplantation of Encapsulated Pancreatic Islets as a Treatment for Patients with Type 1 Diabetes Mellitus

PubMed Central

Qi, Meirigeng

2014-01-01

Encapsulation of pancreatic islets has been proposed and investigated for over three decades to improve islet transplantation outcomes and to eliminate the side effects of immunosuppressive medications. Of the numerous encapsulation systems developed in the past, microencapsulation have been studied most extensively so far. A wide variety of materials has been tested for microencapsulation in various animal models (including nonhuman primates or NHPs) and some materials were shown to induce immunoprotection to islet grafts without the need for chronic immunosuppression. Despite the initial success of microcapsules in NHP models, the combined use of islet transplantation (allograft) and microencapsulation has not yet been successful in clinical trials. This review consists of three sections: introduction to islet transplantation, transplantation of encapsulated pancreatic islets as a treatment for patients with type 1 diabetes mellitus (T1DM), and present challenges and future perspectives. PMID:26556410

Development of native and modified banana starch nanoparticles as vehicles for curcumin.

PubMed

Acevedo-Guevara, Leonardo; Nieto-Suaza, Leonardo; Sanchez, Leidy T; Pinzon, Magda I; Villa, Cristian C

2018-05-01

In recent years, starch nanoparticles have been of great interest for drug delivery due to their relatively easy synthesis, biocompatibility, and vast amount of botanical sources. Native and acetylated starch obtained from green bananas were used for synthesis of curcumin-loaded starch nanoparticles. Mean particle size, encapsulation efficiency, and curcumin release in simulated gastric and intestinal fluids were studied. Both nanosystems showed sizes lower than 250 nm and encapsulation efficiency above 80%, with acetylated banana starch nanoparticles having the capacity to encapsulate more curcumin molecules. Both FTIR and XRD analyses showed that starch acetylation allows stronger hydrogen bond interaction between curcumin and the starch matrix, thus, higher encapsulation efficiency. Finally, curcumin release studies showed that acetylated banana starch nanoparticles allowed more controlled release, probably due to their stronger hydrogen bond interaction with curcumin. Copyright © 2018. Published by Elsevier B.V.

Nano-encapsulations liberated from barley protein microparticles for oral delivery of bioactive compounds.

PubMed

Wang, Ruoxi; Tian, Zhigang; Chen, Lingyun

2011-03-15

Novel microparticles (3-5 μm) were created by pre-emulsifying barley proteins with a homogenizer followed a microfluidizer system. These microparticles exhibited a high oil carrying capacity (encapsulation efficiency, 93-97%; loading efficiency, 46-49%). Microparticle degradation and bioactive compound release behaviours were studied in the simulated gastro-intestinal (GI) tract. The data revealed that nano-encapsulations (20-30 nm) were formed as a result of enzymatic degradation of barley protein microparticle bulk matrix in the simulated gastric tract. These nano-encapsulations delivered β-carotene to a simulated human intestinal tract intact, where they were degraded by pancreatic enzymes and steadily released the β-carotene. These uniquely structured microparticles may provide a new strategy for the nutraceutical and pharmaceutical industries to develop targeted delivery systems for lipophilic bioactive compounds. Copyright © 2011 Elsevier B.V. All rights reserved.

Low cost silicon solar array project silicon materials task

NASA Technical Reports Server (NTRS)

1977-01-01

A program was established to develop a high temperature silicon production process using existing electric arc heater technology. Silicon tetrachloride and a reductant will be injected into an arc heated mixture of hydrogen and argon. Under these high temperature conditions, a very rapid reaction is expected to occur and proceed essentially to completion, yielding silicon and gaseous sodium chloride. Techniques for high temperature separation and collection of the molten silicon will be developed using standard engineering approaches, and the salt vapor will later be electrolytically separated into its elemental constituents for recycle. Preliminary technical evaluations and economic projections indicate not only that this process appears to be feasible, but that it also has the advantages of rapid, high capacity production of good quality molten silicon at a nominal cost.

Encapsulation of single cells into monodisperse droplets by fluorescence-activated droplet formation on a microfluidic chip.

PubMed

Hu, Rui; Liu, Pian; Chen, Pu; Wu, Liang; Wang, Yao; Feng, Xiaojun; Liu, Bi-Feng

2016-06-01

Random compartmentalization of cells by common droplet formation methods, i.e., T-junction and flow-focusing, results in low occupancy of droplets by single cells. To resolve this issue, a fluorescence-activated droplet formation method was developed for the on-command generation of droplets and encapsulation of single cells. In this method, droplets containing one cell were generated by switching on/off a two-phase hydrodynamic gating valve upon optical detection of single cells. To evaluate the developed method, flow visualization experiments were conducted with fluorescein. Results indicated that picoliter droplets of uniform sizes (RSD<4.9%) could be generated. Encapsulation of single fluorescent polystyrene beads demonstrated an average of 94.3% droplets contained one bead. Further application of the developed methods to the compartmentalization of individual HeLa cells indicated 82.5% occupancy of droplets by single cells, representing a 3 fold increase in comparison to random compartmentalization. Copyright © 2016 Elsevier B.V. All rights reserved.

Photovoltaic module encapsulation design and materials section, volume 2

NASA Technical Reports Server (NTRS)

Cuddihy, E. F.

1984-01-01

Tests for chemical structure, material properties, water absorption, aging and curing agent of Ethylene Vinyl Acetate (EVA) and UV absorption studies are carried out. A computer model was developed for thermal optical modeling, to investigate dependence between module operating temperature and solar insolation, and heat dissapation behavior. Structural analyses were performed in order to determine the stress distribution under wind and heat conditions. Curves are shown for thermal loading conditions. An electrical isolation was carried out to investigate electrical stress aging of non-metallic encapsulation materials and limiting material flaws, and to develop a computer model of electrical fields and stresses in encapsulation materials. In addition, a mathematical model was developed and tests were conducted to predict hygroscopic and thermal expansion and contraction on a plastic coated wooden substrate. Thermal cycle and humidity freezing cycle tests, partial discharge tests, and hail impact tests were also carried out. Finally, the effects of soiling on the surface of photovoltaic modules were investigated. Two antisoiling coatings, a fluorinated silane and perflourodecanoic acid were considered.

Soft x ray window encapsulant for HgI2 detectors

NASA Technical Reports Server (NTRS)

Entine, G.; Shah, K.; Squillante, M.

1987-01-01

HgI2 is an excellent semiconductor material for a low energy, room temperature x-ray spectrometer. The high values of the atomic numbers for its constituent elements gives high x-ray and gamma ray stopping power. The band gap of HgI2 is significantly higher than other commonly used semiconductors. Owing to the large value band gap, the leakage current for HgI2 devices is smaller, thus allowing low noise performance. Devices fabricated from HgI2 crystals have demonstrated energy resolution sufficient to distinguish the x-ray emission from the neighboring elements on the periodic table. Also the power requirements of HgI2 are very low. These characteristics make a HgI2 spectrometer an ideal component in a satellite based detection system. Unfortunately, HgI2 crystals tend to deteriorate with time, even if protected by standard semiconductor encapsulants. This degradation ruins the performance of the device in terms of its energy resolution and pulse amplitude. The degrading mechanism is believed to be material loss occurring from below the electrodes, due to high vapor pressure of HgI2 at room temperature. To address this major obstacle to rapid expansion of HgI2 technology, a research program aimed at improving device stability by encapsulation with inert polymeric materials was carried out. The program focused specifically on optimizing the encapsulant materials and their deposition techniques. The principal objectives for this program were device encapsulation, device testing, and accelerated testing to ensure very long term stability of these high resolution sensors. A variety of encapsulants were investigated with the selection criteria based on their chemical diffusion barrier properties, mechanical stability, reactivity, and morphology of encapsulant films. The investigation covered different classes of encapsulants including solvent based encapsulants, vapor deposited encapsulants, and plasma polymerized encapsulants. A variety of characterization techniques were employed to examine their effectiveness in stabilizing HgI2 devices; these included permeability evaluation, vacuum and heat testing, scanning electron microscopy (SEM) as well as studying the detector performance of coated detectors. The plasma polymerized films appear to have entirely solved the HgI2 degradation problem. Another achievement of this program was the development of an accelerated testing technique which correlates extremely well with long term tesing.

The electronic encapsulation of knowledge in hydraulics, hydrology and water resources

NASA Astrophysics Data System (ADS)

Abbott, Michael B.

The rapidly developing practice of encapsulating knowledge in electronic media is shown to lead necessarily to the restructuring of the knowledge itself. The consequences of this for hydraulics, hydrology and more general water-resources management are investigated in particular relation to current process-simulation, real-time control and advice-serving systems. The generic properties of the electronic knowledge encapsulator are described, and attention is drawn to the manner in which knowledge 'goes into hiding' through encapsulation. This property is traced in the simple situations of pure mathesis and in the more complex situations of taxinomia using one example each from hydraulics and hydrology. The consequences for systems architectures are explained, pointing to the need for multi-agent architectures for ecological modelling and for more general hydroinformatics systems also. The relevance of these developments is indicated by reference to ongoing projects in which they are currently being realised. In conclusion, some more general epistemological aspects are considered within the same context. As this contribution is so much concerned with the processes of signification and communication, it has been partly shaped by the theory of semiotics, as popularised by Eco ( A Theory of Semiotics, Indiana University, Bloomington, 1977).