Modern electrets

Bauer, Siegfried; Bauer‐Gogonea, S.; Dansachmüller, M.; Graz, Ingrid; Leonhartsberger, H.; Salhofer, H.; Schwödiauer, Reinhard

doi:10.1109/ultsym.2003.1293425

Cited by 13 publications

(12 citation statements)

References 8 publications

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“…26 Upon heating of a chargestoring material, transient charges are released, and can be characterized, according to the temperature dependence of current generation. For example, charges can be injected into macroscopic voids in porous polymers to create oriented, "quasi-dipoles", known as electrets.…”

Section: B Internal Charge Testingmentioning

confidence: 99%

“…For example, charges can be injected into macroscopic voids in porous polymers to create oriented, "quasi-dipoles", known as electrets. 26 Through TSC, it has been shown that internal charge of a porous polymer can be increased by 50 times through the creation of space charge through charge injection. 27 Likewise, charge also can be trapped at dielectric boundaries such as adjoining crystalline/ amorphous regions, called interfacial polarization.…”

Section: B Internal Charge Testingmentioning

confidence: 99%

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Enhanced piezoelectric performance from carbon fluoropolymer nanocomposites

Baur

DiMaio

McAllister

et al. 2012

Journal of Applied Physics

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The piezoelectric performance of polyvinylidene fluoride (PVDF) is shown to double through the controlled incorporation of carbon nanomaterial. Specifically, PVDF composites containing carbon fullerenes (C 60 ) and single-walled carbon nanotubes (SWNT) are fabricated over a range of compositions and optimized for their Young's modulus, dielectric constant, and d 31 piezoelectric coefficient. Thermally stimulated current measurements show a large increase in internal charge and polarization in the composites over pure PVDF. The electromechanical coupling coefficients (k 31 ) at optimal loading levels are found to be 1.84 and 2 times greater than pure PVDF for the PVDF-C 60 and PVDF-SWNT composites, respectively. Such property-enhanced nanocomposites could have significant benefit to electromechanical systems employed for structural sensing, energy scavenging, sonar, and biomedical imaging. V C 2012 American Institute of Physics.

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Section: B Internal Charge Testingmentioning

confidence: 99%

Section: B Internal Charge Testingmentioning

confidence: 99%

Enhanced piezoelectric performance from carbon fluoropolymer nanocomposites

Baur

DiMaio

McAllister

et al. 2012

Journal of Applied Physics

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“…1 Similar to the role of magnetic field in magnetization of ferromagnetic materials, achieving the ordered orientation of electric dipoles for electret materials requires strong external electric fields. 3 Alternatively, folding into secondary and tertiary conformation, as well as self assembly, allows biological macromolecules to achieve similar ordered orientation of electric dipoles under mild conditions: e.g., the ordered arrangement of amide-bond dipoles in protein helices form through the backbone folding into that conformation (Scheme 1).…”

Section: Narrow-bandgap Dipolar Electretsmentioning

confidence: 99%

Theoretical design of bioinspired macromolecular electrets based on anthranilamide derivatives

Ashraf

Millare

Gerasimenko

et al. 2009

Biotechnology Progress

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Polypeptide helices possess considerable intrinsic dipole moments oriented along their axes. While for proline helices the dipoles originate solely from the ordered orientation of the amide bonds, for 3(10-) and alpha-helices the polarization resultant from the formation of hydrogen-bond network further increases the magnitude of the macromolecular dipoles. The enormous electric-field gradients, generated by the dipoles of alpha-helices (which amount to about 5 D per residue with 0.15 nm residue increments along the helix), play a crucial role in the selectivity and the transport properties of ion channels. The demonstration of dipole-induced rectification of vectorial charge transfer mediated by alpha-helices has opened a range of possibilities for applications of these macromolecules in molecular and biomolecular electronics. These biopolymers, however, possess relatively large bandgaps. As an alternative, we examined a series of synthetic macromolecules, aromatic oligo-ortho-amides, which form extended structures with amide bonds in ordered orientation, supported by a hydrogen-bond network. Unlike their biomolecular counterparts, the extended pi-conjugation of these macromolecules will produce bandgaps significantly smaller than the polypeptide bandgaps. Using ab initio density functional theory calculations, we modeled anthranilamide derivatives that are representative oligo-ortho-amide conjugates. Our calculations, indeed, showed intrinsic dipole moments oriented along the polymer axes and increasing with the increase in the length of the oligomers. Each anthranilamide residue contributed about 3 D to the vectorial macromolecular dipole. When we added electron donating (diethylamine) and electron withdrawing (nitro and trifluoromethyl) groups for n- and p-doping, respectively, we observed that: (1) proper positioning of the electron donating and withdrawing groups further polarized the aromatic residues, increasing the intrinsic dipole to about 4.5 D per residue; and (2) extension of the pi-conjugation over some of the doping groups narrowed the band gaps with as much as 1 eV. The investigated bioinspired systems offer alternatives for the development of broad range of organic electronic materials with nonlinear properties.

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“…However, one should be extremely careful in judging ferroelectret behavior only from hysteresis measurements. [36] "False" hysteresis in displacement and electromechanical strain versus field may be observed from charge injection (which is not related to microdischarges) and elastic nonlinearities, respectively. [36] Nevertheless, there are hysteresis loops that are definitely caused by the switching of the engineered macroscopic dipoles within the voids of the cellular polymer.…”

Section: Analogies To Ferroelectric Materialsmentioning

confidence: 99%

Microstorms in Cellular Polymers: A Route to Soft Piezoelectric Transducer Materials with Engineered Macroscopic Dipoles

2005

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Cellular polymers can be internally charged by "microstorms" (silent or partial discharges) within the voids of the polymer foam. The resulting material, which carries positive and negative charges on the internal void surfaces, is called a ferroelectret. Ferroelectrets behave like typical ferroelectrics, hence they provide a novel class of ferroic materials. The soft foams are strongly piezoelectric and can be used, in a wide range of applications, as transducers for interconverting mechanical and electrical signals. Herein, an overview is provided on the preparation of cellular polymers by physical foaming (extrusion, biaxial stretching, and controlled inflation by pressure treatments), on their charging by "microstorms", on their piezo- and pyroelectricity, and on analogies to ferroelectrics. Finally, a survey of selected applications is presented.

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Modern electrets

Cited by 13 publications

References 8 publications

Enhanced piezoelectric performance from carbon fluoropolymer nanocomposites

Enhanced piezoelectric performance from carbon fluoropolymer nanocomposites

Theoretical design of bioinspired macromolecular electrets based on anthranilamide derivatives

Microstorms in Cellular Polymers: A Route to Soft Piezoelectric Transducer Materials with Engineered Macroscopic Dipoles

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