Measurement of the imaginary part of the clausius-mossotti factor of particle/cell via dual frequency electrorotation
Journal
Micromachines
Journal Volume
11
Journal Issue
3
Date Issued
2020
Author(s)
Abstract
A simple and inexpensive method using planar electrodes was proposed for the measurement of the imaginary part of the Clausius-Mossotti factor,Ki, of particle/cell for electrorotation (ER) and travelling wave dielectrophoresis (twDEP). It is based on the balance between the dielectrophoretic and viscous torques on a particle undergoing ER subject to dual frequency operation in an ER chamber. A four-phase ac voltage signal with a given frequency is applied for generating ER for measurement, and another two-phase signal is applied at a selected frequency for generating a negative dielectrophoretic force for confining the particle motion, instead of using laser tweezer or three-dimensional electrodes in the literature. Both frequencies can be applied to the same electrodes in a four-electrode ER system and to alternative different electrodes in an eight-electrode ER system, and both systems are capable for providing accurate measurement. The measurements were validated by comparing with the theoretical result using sephadex particles in KCl solution, and with the existing experimental results for various human cancer cells in medium with conductivity from 0.01-1.2 S/m, using ER with optical tweezer and dual frequency twDEP. Contrast between the ER and the twDEP methods (the current two available methods) was discussed and commented. The present method could provide measurement for wider frequency range and more accurate result near Ki = 0, in comparison with the results using the twDEP method. However, the twDEP method could perform much more rapid measurement. Detailed forces and torque were calculated inside the ER chamber for understanding the physics and assessing the characteristics of the dual frequency ER method. This study is of academic interest as the torque in ER and the force in twDEP can be calculated only when Ki is known. It also finds biomedical applications as the Ki-spectra can be served as physical phenotypes for different cells, and can be applied for deriving dielectric properties of cells. ? 2020 by the authors. Licensee MDPI, Basel, Switzerland.
Subjects
Dielectrophoresis; Dual frequency; Electrorotation; Imaginary part of the clausius-mossotti factor; Travelling wave dielectrophoresis
SDGs
Other Subjects
Chlorine compounds; Dielectric devices; Dielectric properties; Electrophoresis; Ion exchange; Medical applications; Potassium compounds; Wave transmission; Biomedical applications; Clausius-mossotti factor; Dielectrophoretic forces; Dual frequency; Dual frequency operation; Electrorotation; Three-dimensional electrode; Travelling wave dielectrophoresis; Electrodes
Type
journal article