Fabrication and testing of bubble powered micropumps using embedded microheater

A bubble-powered micropump which consists of a pair of nozzle-diffuser flow controller and a pumping chamber was fabricated and tested in this study. The two-parallel micro line heaters were fabricated to be embedded in the silicon dioxide layer above a silicon wafer which serves as a base plate for the micropump. A pumping chamber, a pair of nozzle-diffuser unit and microchannels including the liquid inlet and outlet port were fabricated by etching through another silicon wafer. A glass wafer having two holes of inlet and outlet ports of liquid serve as upper plate of the pump. Sequential photographs of bubble nucleation, growth and collapse were visualized by CCD camera. The liquid flow through the nozzle during the period of bubble growth and slight back flow of liquid at the collapse period can be clearly seen. The volume flow rate was found to be dependent on the duty ratio and the operation frequency. The volume flow rate decreases as the duty ratio increases in the micropump with either circular or square pumping chamber.