The implementation of a thermal bubble actuated microfluidic chip with microvalve, micropump and micromixer

This paper presents the implementation of a thermal bubble actuated microfluidic chip with microvalve, micropump and micromixer, based on a simple process with SOI wafer. Only two photolithography processes were required to provide an effective means of manufacturing the vertical bulk microheater and high-aspect-ratio microchannel for microfluidic applications. The static and dynamic electro-thermal coupling behaviors of the proposed resistive silicon-based microheater were evaluated by finite element analysis to provide an applicable design. The feasibility of each actuation element has also been verified by experiments. Experimental results show that the sizes of thermal bubbles, at flow rates less than 4.5 μl/s, can be controlled steadily by applying the magnitude of direct current that meets the requirement of a microvalve to modulate flow rate. When applying an alternating current with high frequency to the microheater, thermal bubbles could grow cyclically and collapse rapidly, so the liquid stream could be regulated by the repeated volume change of thermal bubbles. A maximum volume flow rate of 4.5 μl/s was obtained, under the driving voltage with a frequency of 60 Hz and 30% duty ratio. The mixing test of the multi-layer fluidics with laminar flow also was successfully implemented by using the volume of thermal bubble to create turbulent flow in the fluids. With no moving parts, the proposed microfluidic chip is well designed with high performance and reliability.