A parametric study of AC electrothermal flow in microchannels with asymmetrical interdigitated electrodes

In this study, the AC electrothermal (ACET) flow in a microchannel with asymmetrical planar electrode pairs, in the same configuration as an AC electroosmosis (ACEO) pump, is studied numerically. The electrical, temperature and velocity fields in the microchannel are obtained by solving the coupled electrical, momentum and energy equations. The effects of electrode size, gap and length ratios, electrical conductivity of electrolyte solution, thermal conductivity of microchannel base material, as well as voltage and the frequency of AC on ACET flow are investigated in details. It is found that in the operating frequency range of the ACEO pump, i.e. 100 Hz–100 kHz, the velocity of the ACET flow is frequency-independent and moves in the same direction as the ACEO flow, and effects of electrode size, gap and length ratios on flow velocity have the same trend as the ACEO flow. Because the ACET flow velocity is proportional to electrical conductivities of electrolyte solution linearly and to the fourth power of the applied voltage, while the ACEO flow velocity decreases with the increase of electrical conductivity of the electrolyte solution and is only proportional to the square of applied voltage, therefore the ACET flow should not be neglected in an ACEO pump for the cases of high conductivity of electrolyte solution and relatively high AC voltage where ACEO and ACET effects are comparable.