Three-dimensional analyses of cells’ positioning on the quadrupole-electrode microfluid chip considering the coupling effect of nDEP, ACEO, and ETF

Microfluidic chips integrated with negative dielectrophoresis (nDEP) and electrochemical impedance spectroscopy have wide applications in cell sensing. Accurate analysis of the kinematics and dynamics of cells in the nDEP process is crucial to improve the positioning accuracy and electric cell-substrate impedance sensing (ECIS) performance. This paper reports employing the three-dimensional (3D) finite element model to analyze the coupling effects of electrokinetic flows (EF) such as alternating current electroosmosis (ACEO) and the electrothermal flow (ETF) on the nDEP positionings. On the quadrupole ECIS microfluid chip, three typical nDEP results are observed in the frequency range of 100 Hz-25 MHz and the amplitude range of 1-20 V_p-p. Simulations Based on the 3D hybrid model provide abundant kinematic information and show clear dynamic processes. Based on the discussion, the mechanisms of nDEP localizations and phase-tuning manipulations are proposed. It is found that the drag force could affect the particle's movement through the vortex of the flow field induced by ACEO and ETF, while the nDEP forces dominate the particles' locations on the substrate. Thus, the 3D dynamic-coupling analyses could help design the quadrupole-electrode microfluid chip and optimize the manipulation parameters in the experiment.