Biopolymer Composites With High Dielectric Performance: Interface Engineering
01 Jan 2017-pp 27-128
TL;DR: In this article, the preparation and dielectric behavior of various biopolymer composites is presented, including metal nanoparticles and carbon-based nanofillers such as carbon nanotubes, graphene, etc.
Abstract: In recent years, there is a growing interest in studying the dielectric behavior of biopolymer composites due to their potential application as a dielectric material in various electronic devices such as microchips, transformers, and circuit boards. Conducting electroactive polymer composites have also been investigated for various potential applications which include biological, biomedical, flexible electrodes, display devices, biosensors, and cells for tissue engineering. In this chapter, the preparation and dielectric behavior of various biopolymer composites is presented. These biopolymer composites generally consist of nanoscale metal nanoparticles and carbon-based nanofillers such as carbon nanotubes, graphene, graphene oxide (GO), etc., dispersed into the polymer matrix. The physical and chemical properties of these fillers and their interactions with polymers have a significant effect on the microstructure and the final properties of nanocomposites. The biopolymer composites with excellent dielectric properties show great promise as an energy storage dielectric layer in high-performance capacitor applications such as embedded capacitors. This chapter highlights some of the examples of such biopolymer composites; their processing and dielectric behavior will be discussed in detail.
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References
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TL;DR: The results indicate that the chemical composition, morphology, electronic transport, and bioactivity of polymer coatings on electrode surfaces on a multichannel micromachined neural probe can be adjusted by controlling electrochemical deposition conditions.
Abstract: The interface between micromachined neural microelectrodes and neural tissue plays an important role in chronic in vivo recording Electrochemical polymerization was used to optimize the surface of the metal electrode sites Electrically conductive polymers (polypyrrole) combined with biomolecules having cell adhesion functionality were deposited with great precision onto microelectrode sites of neural probes The biomolecules used were a silk-like polymer having fibronectin fragments (SLPF) and nonapeptide CDPGYIGSR The existence of protein polymers and peptides in the coatings was confirmed by reflective microfocusing Fourier transform infrared spectroscopy (FTIR) The morphology of the coating was rough and fuzzy, providing a high density of bioactive sites for interaction with neural cells This high interfacial area also helped to lower the impedance of the electrode site and, consequently, to improve the signal transport Impedance spectroscopy showed a lowered magnitude and phase of impedance around the biologically relevant frequency of 1 kHz Cyclic voltammetry demonstrated the intrinsic redox reaction of the doped polypyrrole and the increased charge capacity of the coated electrodes Rat glial cells and human neuroblastoma cells were seeded and cultured on neural probes with coated and uncoated electrodes Glial cells appeared to attach better to polypyrrole/SLPF-coated electrodes than to uncoated gold electrodes Neuroblastoma cells grew preferentially on and around the polypyrrole/CDPGYIGSR-coated electrode sites while the polypyrrole/CH(3)COO(-)-coated sites on the same probe did not show a preferential attraction to the cells These results indicate that we can adjust the chemical composition, morphology, electronic transport, and bioactivity of polymer coatings on electrode surfaces on a multichannel micromachined neural probe by controlling electrochemical deposition conditions
548 citations
TL;DR: In this article, the dielectric properties of the untreated multiwall carbon-nanotubes∕poly(vinylidene fluoride) (MWNT∕PVDF) composites are studied.
Abstract: In this letter, the dielectric properties of the untreated multiwall carbon-nanotubes∕poly(vinylidene fluoride) (MWNT∕PVDF) composites are studied. Towards low frequencies, the dielectric constant of a composite with about 2.0vol% of MWNT increases rapidly and the value of the dielectric constant is as high as 300. However, by a calculation, the percolation threshold of the MWNT∕PVDF composites is only 1.61vol% (0.0161 volume fraction) of MWNT. Both the large aspect ratio and the high conductivity of the MWNT may lead to the low percolation threshold of the MWNT∕PVDF composites. For the percolation composite, the dielectric loss value is always less than 0.4, irrespective of the frequency. Therefore, the experimental results suggest that the dielectric properties of MWNT∕PVDF composites may be improved significantly without the chemical functionalization to carbon nanotubes.
508 citations
TL;DR: In this paper, orientational polarization in polar polymers can be utilized for high energy density and low loss dielectrics, which can be used for next-generation dielectric capacitors for pulsed power and power conditioning applications.
Abstract: The state-of-the-art polymer dielectrics have been limited to nonpolar polymers with relatively low energy density but ultralow dielectric losses for the past decades. With the fast development of power electronics in pulsed power and power conditioning applications, there is a need for next-generation dielectric capacitors in areas of high energy density/low loss and/or high temperature/low loss polymer dielectrics. Given limitations in further enhancing atomic and electronic polarizations for polymers, this Perspective focuses on a fundamental question: Can orientational polarization in polar polymers be utilized for high energy density and low loss dielectrics? Existing experimental and theoretical results have suggested the following perspectives. For amorphous polar polymers, high energy density and low loss can be achieved below their glass transition temperatures. For liquid crystalline side-chain polymers, dipole mobility is so high that they saturate at relatively low electric fields, and only li...
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TL;DR: The concept of cartilage tissue engineering, common types of bio-engineered materials and future development of biomaterial scaffolds are introduced.
Abstract: Since the last decade, tissue engineering has shown a sensational promise in providing more viable alternatives to surgical procedures for harvested tissues, implants and prostheses. Due to the fast development on biomaterial technologies, it is now possible for doctors to use patients’ cells to repair orthopedic defects such as focal articular cartilage lesions. In order to support the three-dimensional tissue formation, scaffolds made by biocompatible and bioresorbable polymers and composite materials, for providing temporary support of damaged body and cell structures have been developed recently. Although ceramic and metallic materials have been widely accepted for the development of implants, its non-resorbability and necessity of second surgical operation, which induces extra for the patients, limit their wide applications. This review article aims at introducing (i) concept of cartilage tissue engineering, (ii) common types of bio-engineered materials and (iii) future development of biomaterial scaffolds.
499 citations
TL;DR: In this paper, the structure and properties of the PLLA-clay blends were investigated, and it was found that the clay existed in the form of tactoids, which consist of several stacked silicate monolayers.
Abstract: Organophilic montmorillonite was obtained by the reaction of montmorillonite (MON) and distearyldimethylammonium chloride (DSAC). The modified clay and poly(l-lactide), (PLLA), were solvent-cast blended using chloroform as cosolvent. The structure and properties of the PLLA-clay blends were investigated. Thermal measurements revealed that cold crystallization took place in the as-cast PLLA, and that the clay served as a nucleating agent. From small and wide-angle x-ray scattering measurements, it was found that silicate layers forming the clay could not be individually well dispersed in the PLLA-clay blends prepared by the solvent-cast method. In other words, the clay existed in the form of tactoids, which consist of several stacked silicate monolayers. However, these tactoids formed a remarkable geometrical structure in the blend films. That is, their surfaces lay almost parallel to the film surface, and were stacked with the insertion of PLLA crystalline lamellae in the thickness direction of the film. During the blend drawing process, fibrillation took place with the formation of plane-like voids developed on the plane parallel to the film surface. Furthermore, delamination of the silicate layers did not occur even under the application of a shearing force. Finally, Young's modulus of the blend increased with the addition of a small amount of the clay. © 1997 John Wiley & Sons, Inc.
461 citations