Computer-aided analyses of electric fields used in electrorotation studies

Abstract

The spatial variations of the magnitude and phase of the electric field produced by electrodes used in electrorotation studies have been computed, using the charge density method at 10 degrees intervals for one complete AC cycle of the applied voltages. These results, together with the development of a more general theoretical treatment than has hitherto been applied to this problem, enable the time-averaged rotational torque and dielectrophoretic force acting on a particle to be determined as a function of its location within the inter-electrode space. Correction factors that can be applied to electrorotation spectra to take account of the relative position, or change in position, of the test particle are provided for electrodes of polynomial and circular geometry.

Mapping the electrorotational torque in planar microelectrodes

“…Here we examine the rotation rate of uniform elliptical latex beads occupying 203 positions across a polynomial electrode array. This data, coupled with data processing to determine the underlying trends, exhibits striking similarities to the model predicted by Hughes et al (1994), implying that differences in the phase relationships play a significant role in determining the distribution of torque about the electrode array.…”

“…Various studies have been performed using numerical simulation and field-mapping using large-scale electrodes (Gimsa et al 1987, Hölzel 1993, Hughes et al 1994 to determine the induced torque as a function of particle position within the chamber. The previous two studies were based on the principle that torque varies as a function of the square of the electric field; Hughes et al (1994) introduced the concept that torque is also related to phase differences across the rotation area.…”

“…The previous two studies were based on the principle that torque varies as a function of the square of the electric field; Hughes et al (1994) introduced the concept that torque is also related to phase differences across the rotation area. However, this model was never demonstrated to be correct in practical experimentation.…”

Electromechanical effects on multilayered cells in nonuniform rotating fields

“…We study the frequency range from 10 kHz to 300 MHz and assume that the electrode response is linear, i.e., that no frequency components other than those applied to the electrodes can evolve in the chamber and that electrode polarization effects are negligibly small. In addition, we do not consider in our calculations the influence of the gradient of the phase of the electric field on the force and torque, which could produce traveling wave effects [11].…”

“…Since at this order the induced dipole is itself proportional to the applied field, controlling the square and the gradient of the square of the electric field are critical issues in the design of the electrodes that generate the rotating fields in an ER chamber [1,[11][12][13][14][15][16][17].…”