scholarly journals Influence of Different Solvents and High-Electric-Field Cycling on Morphology and Ferroelectric Behavior of Poly(Vinylidene Fluoride-Hexafluoropropylene) Films

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3884
Author(s):  
Till Mälzer ◽  
Lena Mathies ◽  
Tino Band ◽  
Robert Gorgas ◽  
Hartmut S. Leipner
Keyword(s):  
Phase Composition ◽  
Electric Field ◽  
Surface Structure ◽  
Electric Fields ◽  
Vinylidene Fluoride ◽  
High Electric Field ◽  
Crystal Phase ◽  
Shielding Effect ◽  
Ferroelectric Behavior ◽  
Field Cycling

P(VdF-HFP) films are fabricated via a solution casting doctor blade method using high (HVS) and low (LVS) volatile solvents, respectively. The structural properties and the ferroelectric behavior are investigated. The surface structure and crystal phase composition are found to be strongly dependent on the type of solvent. LVS leads to a rougher copolymer surface structure with large spherulites and a lower crystallinity in contrast with HVS. The crystalline phase of copolymer films fabricated with HVS consists almost exclusively of α-phase domains, whereas films from LVS solution show a large proportion of γ-phase domains, as concluded from Raman and X-ray diffraction spectra. Virgin films show no ferroelectric (FE) switching polarization at electric field amplitudes below 180 MV/m, independent of the solvent type, observed in bipolar dielectric displacement—electric field measurements. After applying electric fields of above 180 MV/m, a FE behavior emerges, which is significantly stronger for LVS films. In a repeated measurement, FE polarization switching already occurs at lower fields. A shielding effect may be related to this observation. Additionally, Raman bands of polar γ-phase increase by high-electric-field cycling for the LVS sample. The solvent used and the resulting crystal phase composition of the virgin sample is crucial for the copolymer behavior during bipolar electrical cycling.

Rotation of polar axis of β-form poly(vinylidene fluoride) under high electric field

1984 ◽  
Vol 57 (1) ◽  
pp. 139-149 ◽  
Author(s):  
Ken'ichi Nakamura ◽  
Yoshikichi Teramoto ◽  
Naohiro Murayama
Keyword(s):  
Electric Field ◽  
Vinylidene Fluoride ◽  
Polar Axis ◽  
High Electric Field ◽  
Poly Vinylidene Fluoride

scholarly journals Cell Fragmentation and Permeabilization by a 1 ns Pulse Driven Triple-Point Electrode

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Enbo Yang ◽  
Joy Li ◽  
Michael Cho ◽  
Shu Xiao
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Triple Point ◽  
Tungsten Wire ◽  
Low Voltage ◽  
Pulsed Electric Fields ◽  
High Electric Field ◽  
Bubble Collapse ◽  
Principal Mechanism ◽  
Point Electrode

Ultrashort electric pulses (ns-ps) are useful in gaining understanding as to how pulsed electric fields act upon biological cells, but the electric field intensity to induce biological responses is typically higher than longer pulses and therefore a high voltage ultrashort pulse generator is required. To deliver 1 ns pulses with sufficient electric field but at a relatively low voltage, we used a glass-encapsulated tungsten wire triple-point electrode (TPE) at the interface among glass, tungsten wire, and water when it is immersed in water. A high electric field (2 MV/cm) can be created when pulses are applied. However, such a high electric field was found to cause bubble emission and temperature rise in the water near the electrode. They can be attributed to Joule heating near the electrode. Adherent cells on a cover slip treated by the combination of these stimuli showed two major effects: (1) cells in a crater (<100 μm from electrode) were fragmented and the debris was blown away. The principal mechanism for the damage is presumed to be shear forces due to bubble collapse; and (2) cells in the periphery of the crater were permeabilized, which was due to the combination of bubble movement and microstreaming as well as pulsed electric fields. These results show that ultrashort electric fields assisted by microbubbles can cause significant cell response and therefore a triple-point electrode is a useful ablation tool for applications that require submillimeter precision.

scholarly journals Mechanism of Spontaneous Surface Modifications on Polycrystalline Cu Due to Electric Fields

Micromachines ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 1178
Author(s):  
Kristian Kuppart ◽  
Simon Vigonski ◽  
Alvo Aabloo ◽  
Ye Wang ◽  
Flyura Djurabekova ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Linear Collider ◽  
Lattice Structure ◽  
High Electric Field ◽  
Formation Mechanisms ◽  
Particle Accelerators ◽  
European Organization ◽  
Copper Surfaces ◽  
Electrostatic Stress

We present a credible mechanism of spontaneous field emitter formation in high electric field applications, such as Compact Linear Collider in CERN (The European Organization for Nuclear Research). Discovery of such phenomena opens new pathway to tame the highly destructive and performance limiting vacuum breakdown phenomena. Vacuum breakdowns in particle accelerators and other devices operating at high electric fields is a common problem in the operation of these devices. It has been proposed that the onset of vacuum breakdowns is associated with appearance of surface protrusions while the device is in operation under high electric field. Moreover, the breakdown tolerance of an electrode material was correlated with the type of lattice structure of the material. Although biased diffusion under field has been shown to cause growth of significantly field-enhancing tips starting from initial nm-size protrusions, the mechanisms and the dynamics of the growth of the latter have not been studied yet. In the current paper we conduct molecular dynamics simulations of nanocrystalline copper surfaces and show the possibility of protrusion growth under the stress exerted on the surface by an applied electrostatic field. We show the importance of grain boundaries on the protrusion formation and establish a linear relationship between the necessary electrostatic stress for protrusion formation and the temperature of the system. Finally, we show that the time for protrusion formation decreases with the applied electrostatic stress, we give the Arrhenius extrapolation to the case of lower fields, and we present a general discussion of the protrusion formation mechanisms in the case of polycrystalline copper surfaces.

scholarly journals Shielding effects of myelin sheath on axolemma depolarization under transverse electric field stimulation

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e6020 ◽  
Author(s):  
Hui Ye ◽  
Jeffrey Ng
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Myelin Sheath ◽  
Transmembrane Potential ◽  
Transverse Electric ◽  
Myelinated Axon ◽  
Transverse Electric Field ◽  
Unmyelinated Axon ◽  
Shielding Effect ◽  
Cable Equation

Axonal stimulation with electric currents is an effective method for controlling neural activity. An electric field parallel to the axon is widely accepted as the predominant component in the activation of an axon. However, recent studies indicate that the transverse component to the axolemma is also effective in depolarizing the axon. To quantitatively investigate the amount of axolemma polarization induced by a transverse electric field, we computed the transmembrane potential (Vm) for a conductive body that represents an unmyelinated axon (or the bare axon between the myelin sheath in a myelinated axon). We also computed the transmembrane potential of the sheath-covered axonal segment in a myelinated axon. We then systematically analyzed the biophysical factors that affect axonal polarization under transverse electric stimulation for both the bare and sheath-covered axons. Geometrical patterns of polarization of both axon types were dependent on field properties (magnitude and field orientation to the axon). Polarization of both axons was also dependent on their axolemma radii and electrical conductivities. The myelin provided a significant “shielding effect” against the transverse electric fields, preventing excessive axolemma depolarization. Demyelination could allow for prominent axolemma depolarization in the transverse electric field, via a significant increase in myelin conductivity. This shifts the voltage drop of the myelin sheath to the axolemma. Pathological changes at a cellular level should be considered when electric fields are used for the treatment of demyelination diseases. The calculated term for membrane polarization (Vm) could be used to modify the current cable equation that describes axon excitation by an external electric field to account for the activating effects of both parallel and transverse fields surrounding the target axon.

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