Joule heating effects on two-phase flows in dielectrophoresis microchips

Abstract

Joule heating is a significant phenomenon in dielectrophoresis-based microfluidic devices due to the local amplification of the electric field around electrodes. This leads to the temperature rising in microchannel which would influence the bioactivity of samples in the microchannel. In this paper, a numerical simulation model considering joule heating effect, electric field, and flow field is proposed to describe dynamic behaviors of two-phase flows of the dielectrophoresis microchip. The experimental methods are applied to verify the rationality of model and joule heating effects on microchips under both AC (Alternating current) and DC (Direct current) electric fields are investigated in detail. In numerical simulation part, the difference between AC and DC electric fields is compared. According to the results, it is found that with the same effective voltage, DC electric field can generate more joule heat and flow in the microchannel obtained higher temperature. This is caused by that the electric field strength around the electrodes in the DC electric field is stronger than that of the AC electric field. Secondly, effects of dispersed phase and continuous phase flow velocity are investigated and temperature will decrease with the increasing of flow velocity. Also, it is found that the Joule heating effects improve the droplet velocity based on the results. Finally, an infrared camera is applied to monitor the thermal characteristics of the microchannel to ensure that the numerical simulation is reasonable. These results are expected to provide useful guidance for future designs of dielectrophoresis-based microdevices that will avoid joule heating effects or take advantage of joule heating effects.