Experimental and computational study of optically-driven electrothermal vortex. (5th August 2019) - Pan, Xudong
Optically-driven electrothermal vortex flow is one of the most effective ways to induce convection in microscale domains. In this work, side view microscopic imaging is used for qualitative flow visualisation as well as quantitative µPIV measurements of the vortex pattern in microfluidic chips between simple parallel-plate electrodes. The uniform electric field is generated from parallel-plate, indium tin oxide (ITO) electrodes separated by 400 µm. Alternating current (AC) electric fields at a range of frequencies (9-100 kHz) and voltages (5-40 V) are applied to the electrodes to drive the flow. Simultaneously, a near-infrared (1064 nm) laser beam at various intensities is focused on the bottom electrode surface of the microchannel. Strong electrothermal vortices are observed in the flow visualisation experiments and measured by µPIV. A realistic computational model featuring a laser heat source and an applied electrical field is constructed. Computational simulations are performed under the same conditions as the experiments. The simulations and the experiments show the same qualitative behaviours and also agree quantitatively when comparing the maximum velocities.