Square Of Electric Field Strength Research Articles

Electrorheological performances of poly(o-toluidine) and p-toluenesulfonic acid doped poly(o-toluidine) suspensions

Poly(o-toluidine) (POT) and p-toluenesulfonic acid doped poly(o-toluidine) (TSA-POT) were synthesized via chemical oxidation and emulsion polymerization, respectively. The rheological measurements of the dedoped POT and TSA-POT silicone oil suspensions showed that both of the suspensions exhibited electrorheological (ER) effect under electric field. The analyses of the rheological curves of suspension indicated that POT and TSA-POT suspensions presented different flow behaviors. POT suspensions presented fast polarization under external electric field with the existence of critical shear rates (γcrit), and POT suspensions behaved well with Bingham model above γcrit TSA-POT suspension behaved very well with Cho–Choi–Jhon model in all shear rate regions. Both of static and dynamic yield stresses for POT and TSA-POT suspensions in electric field were proportional to the square of electric field strength. The different ER performances between POT and TSA-POT suspensions were explained based on the conductivity and dielectric constant of the particles. The modification of conductivity and dielectric constant by doping POT with TSA improved the ER performance of TSA-POT suspension.

Effect of Field Strength on Electrooptical Properties of Low-Molecular Weight and Polymer Liquid Crystals

The influence of a strong electric field on isotropic melts of 6-cyanobiphenyl and comb-shaped polyacrylate with side mesogenic groups was investigated. It was established that the electric field induces the isotropic—nematic phase transition in melts of these compounds. A relaxation process was discovered that destroys the nematic ordering induced in substances by electric fields. It was found that the relaxation time τ of the orientational order parameter is proportional to the square of electric field strength. For comb-shaped polymer liquid crystals, the time of transition from the nematic to the isotropic phase is several orders longer then that for low-molecular liquid crystal.

Input–output relationship in galvanotactic response of Dictyostelium cells

Under a direct current electric field, Dictyostelium cells exhibit migration towards the cathode. To determine the input–output relationship of the cell's galvanotactic response, we developed an experimental instrument in which electric signals applied to the cells are highly reproducible and the motile response are analyzed quantitatively. With no electric field, the cells moved randomly in all directions. Upon applying an electric field, cell migration speeds became about 1.3 times faster than those in the absence of an electric field. Such kinetic effects of electric fields on the migration were observed for cells stimulated between 0.25 and 10 V/cm of the field strength. The directions of cell migrations were biased toward the cathode in a positive manner with field strength, showing galvanotactic response in a dose-dependent manner. Quantitative analysis of the relationship between field strengths and directional movements revealed that the biased movements of the cells depend on the square of electric field strength, which can be described by one simple phenomenological equation. The threshold strength for the galvanotaxis was between 0.25 and 1 V/cm. Galvanotactic efficiency reached to half-maximum at 2.6 V/cm, which corresponds to an approximate 8 mV voltage difference between the cathode and anode direction of 10 μm wide, round cells. Based on these results, possible mechanisms of galvanotaxis in Dictyostelium cells were discussed. This development of experimental system, together with its good microscopic accessibility for intracellular signaling molecules, makes Dictyostelium cells attractive as a model organism for elucidating stochastic processes in the signaling systems responsible for cell motility and its regulations.

Influence of strong electric field on dielectric permittivity of polycrystalline ice at MHz frequencies

Electric permittivity of polycrystalline ice measured at 5 MHz was found to decrease proportionally to the square of electric field strength. A simple model explaining this property based on a Bjerrum-type attempt is proposed.

The in-plane switching of homogeneously aligned nematic liquid crystals

We have investigated the electro-optical effects and physical switching principle of homogeneously aligned nematic liquid crystals when applying an in-plane electric field with interdigital electrodes. By using the in-plane switching (IPS) of the liquid crystals which is achieved by the in-plane electric field, the viewing angle characteristics of the electro-optical effects were confirmed to be far superior to those of the conventional twisted nematic mode in which the electric field is applied along the direction perpendicular to the substrates. The non-reversal region of grey scales was extremely wide in which a high contrast ratio was kept, even along quite an oblique direction in the IPS mode. In order to clarify the switching principle of the liquid crystals in the IPS mode, a simplified expression describing the threshold behaviour of the device was derived with the assumption that a uniform in-plane electric field was applied along a direction perpendicular to the director and parallel to the homogeneously aligned nematic slab, and found to be sufficiently able to explain the experimental results. First, a critical field at which the liquid crystals just began to twist, was found to be proportional to the reciprocal of the cell gap. Second, it was the electric field and not the voltage that drives the liquid crystals. This relationship was due to the independence of the electric field regarding the liquid crystal layer normal direction. So the threshold voltage in the IPS mode was strongly dependent on the variation of the cell gap. For the dynamical response mechanism of the liquid crystals to the in-plane electric field, the switching on and off processes of the liquid crystals were analysed quantitatively. The relaxation time of the liquid crystals when removing the electric field could be described as proportional to the square of the cell gap. A thinner cell gap also proved to be effective in obtaining a fast response time in the IPS mode. In contrast, the switching on time when applying the in-plane electric field was found to be inversely proportional to the difference between the square of the electric field strength and the square of the critical electric field strength at which the liquid crystals began to deform.

Response mechanism of nematic liquid crystals using the in-plane switching mode

A response mechanism of nematic liquid crystals following the switching-on and off of an in-plane electric field when using the in-plane switching (IPS) mode was investigated. Simplified theoretical expressions, which were derived with an assumption that an in-plane electric field was applied to the liquid crystals, were used to explain the dynamical switching process in the IPS mode. In particular, the relaxation time of the liquid crystals when removing the electric field was described as a proportional relationship to the square of the cell gap. A thinner cell gap also proved to be effective in obtaining a fast response time in the IPS mode. By contrast, the switching-on time when applying the in-plane electric field proved to be inversely proportional to the difference between the square of the electric field strength and the square of the critical electric field strength at which the liquid crystals begin to deform.

スメクタイト粒子をシリコーン油中に分散させた流体のエレクトロレオロジー特性

Synthesized smectite particles have been dispersed in methylphenyl silicon oil. The prepared fluid is stable in a gravitational field. The viscosity of this fluid under electric field has been investigated by many parameters as follows, smectite content in silicon oil, shear rate, electric field strength, frequency of electric field or DC field, temperature of fluid, frequency on viscoelasticity, response time, stability and durability, and so on. The shear stress and current density have increased almost in proportion to a square of electric field strength. The dynamic modulus and dynamic loss change much more in the fluid dispersing lower smectite concentration by applying electric field. For the durability of fluid the viscosity is almost same for several hours under 2kV/mm. This fluid is expected to use in the damper, actuators and so on.

Dielectric Mechanism and Rheological Properties of Electro-Fluids

Dielectric behaviour of electro-fluids which show the Winslow effect, one of the electro-viscous effect, is studied experimentally. From the experimental results that water film adsorbed to the particles directly affects the surface charge density of electric double layers and makes dielectric constant of electro-fluids increase, the model of electric double layers proposed by Schwarz is able to be applied to the Winslow effect. Using Krieger-Maron's method about non-Newtonian flow, electro-fluids under an electric field are found to be approximated by the Bingham body with the yielding shear stress proportional to the square of electric field strength. Besides, electro-fluids show the negative thixotropy that the viscosity increases with time under an electric field.

Voltage Signal due to Electron-Beam-Induced Conductivity in Semiconductors

A formula for a change in the terminal voltage due to the electron-beam irradiation is proposed for a d.c. biased semiconductor bar. The change is composed of three terms; an ohmic drop due to the irradiating beam current, an induced voltage due to the bulk electron voltaic effect and a signal due to the electron-beam-induced conductivity (β-conductivity). The last term, which is called β-conductive signal, is proportional to the square of electric field strength, or to the square of resistivity if the biasing current density is constant, and this was experimentally confirmed using a p-Ge bar whose volume and mean resistivity were 0.5×1×9.5 mm3 and 3.8 \\varOmegacm, respectively. The current, energy and diameter of the irradiating electron beam were 0.1 nA, 20 KeV and about 10 µm, respectively.