On Chip Micropumping for Biofluids by Temperature Biased AC Electrothermal Effect

For biofluids, very limited voltage can be applied without causing reactions, even with AC voltages, so conventional electrokinetic pumps cannot function effectively. Here two innovative ACEK micropump designs are proposed, which are expected to solve the long-standing problem of on-chip pumping for biofluids. This work focuses on exploiting external heat flux or temperature bias to enhance micropumping by AC electrothermal effect. AC electrothermal effect is ubiquitous as long as electric current flows through fluid. Investigating the interplay between electric field and temperature field will be useful for the research area of electrokinetics as a whole. New methods to enhance on chip micorpumping have been presented in this paper. Inhomogenous electric fields can cause uneven Joule heating of the fluid, which generates thermal gradients and leads to mobile charges in fluid bulk. The two pumping schemes circumvent the voltage problem by introducing extra thermal gradient to generate mobile charges. The free charges then move under the electric field and induce microflows due to viscosity. Numerical simulation and preliminary experiments have successfully demonstrated the improvement in flow velocity. It enriches the repertoire for the design of ACEK micropump, and affords us more flexibility when dealing with micropumping tasks. The micropumping mechanisms proposed here are simple, robust, of small form factor, can be readily integrated into microsystems at low cost. The proposed fabrication and micropump integration process is highly manufacturable with various materials and can be easily incorporated into a fully integrated biochip. The added design flexibility from this project will lend the pump design well towards many lab-on-a-chip applications.