LAUSR

The ability to maintain a relative low temperature rise, portability and also achieve fast mixing process is major advantage for high ionic strength processing, where high conductive fluids handled by AC electrothermal (ACET) effects. In this study we examine the frequency dependency of AC electroosmotic (ACEO) and ACET effects, to generate high efficient temperature gradients and corresponding conductivity/permittivity gradients with relatively low temperature rise. We drive the electrodes by amplitude-modulated (AM) sine-wave and it generates non-uniform electric field with small temperature rise, in comparison with the simple sine-wave. The excitation parameters such as voltage amplitude A, sine-wave frequency fc, and also modulation frequency fm, were optimized to achieving both high mixing efficiency and low temperature rise. Technological details of proposed silicon/PDMS fabrication method has been discussed in details for the AC Electrothermally-driven micromixer and a set of numerical simulations were done for the microactuator. An effective ACET flow along with the low temperature rise is observed in optimal frequency range of 0.1 MHz < fc < 9 MHz. A full mixing efficiency achieved by using only three pairs of the electrodes and with the maximum temperature rise of 5.5 K. The reduction in temperature rise is very important for extending ACET mixing applications and device portability. As a proof of chaotic regime, two particles released inside the channel and particle tracing accomplished, the results showed that the particles were stretched and folded. The technological details of fabrication process and thermal effects handling has been discussed in details.