Study of dielectric properties of biological cells and particles is a growing field of interest in present-day biomedical applications. Dielectric properties of cells are widely used in dielectrophoretic (DEP) based separation and manipulation of various cell types and particles. In addition, dielectric properties of the biological cells can be used to monitor changes in cells’ biophysical parameters and provides an inspection to their physical status [1,2]. Different methodologies are employed to study the dielectric properties of the biological particles, including electrorotation (ER) [3–8], dielectrophoresis [7–11], microelectrical impedance spectroscopy (µ-EIS) [12,13], and impedance flow cytometry (IFC) [14–17]. ER is a non-invasive technique used to study the electric properties of particles by investigating the frequency dependent rotational response. ER is utilized as the most accurate dielectric characterization method, capable of revealing membrane and interior dielectric properties of the cells [18]. This phenomenon is associated with rotation of polarizable particles, in the presence of an external rotating electric field [19–21]. The rotation of the particles is a result of interaction of induced dipole on the particles with the rotating electric field. Therefore, the rotational torque is proportional to effective electric field (EEF) distribution. The rotating electric field is generated by application of signals with equal amplitudes with 360º/n phase shifted apart to n electrodes [22,23]. Electrodes are arrayed symmetrically around the measurement area. In the literature, quadrupole electrodes with 90º phase shifts are extensively used for characterization. Different electrode geometries including circ...
... middle of paper ...
...µm in z-direction) were designed and fabricated using conventional MEMS techniques. Imatinib (chemotherapeutic drug) resistant human leukemia cells (K562/IMA-300) with an average radius of 7.65 µm were used to study the experimental ROT-T on ER devices. To study the variance of the ROT-T in z-direction, the measurements were performed at above (z~=100 µm) and below (z < 30 µm) the electrodes ceiling. The experimental ROT-T map of the ER devices was extracted in both planes and numerical analyses were employed to verify the results. Experimental and numerical investigations in this study prove that variances in z-component of the EEF are considerably large to lead misinterpretation of measured rotation data. However, 3D electrodes, utilized in this study, provide a uniform distribution of EEF with almost constant magnitude along the electrode height (30 µm).