Doctor of Philosophy (PhD)


Mechanical Engineering

Document Type



This dissertation covers the research work on two types of micropumps, one is based on magnetohydrodynamic (MHD) principle that utilizes Lorentz force for actuation, and the other is based on electrochemical actuation. The AC-type MHD micropump was designed and analyzed as a solution to the bubble formation problem encountered in DC-type MHD micropump. A UV-LIGA process using thick layer of SU-8 negative photoresist was successfully developed to microfabricate the AC MHD micropump. Preliminary studies and tests of the AC MHD micropumps demonstrate that bubble formation was significantly reduced to permit the proper function of the micropump. A continuous flow was also successfully demonstrated with no moving mechanical parts needed. To develop the mathematical model for flow of conductive fluids between the electrodes was a challenging issue. To overcome this problem, the impedance of conductive fluids between two electrodes was measured by Electrochemical Impedance Spectroscopy, which then helped to obtain a relatively accurate mathematical model for the system. The design, simulation, fabrication, and test results of the AC MHD micropump are presented in this dissertation. Electrochemical actuator was investigated for micropumping applications. In our research efforts to develop DC-type MHD micropump, bubble formation problem caused by electrolysis proved to be one of the most difficult issues. However, microactuation based on expanding bubbles from electrolysis effect has scale advantages compared with other commonly used microactuation mechanisms. It can therefore be used as a very efficient actuation source for micropumping applications. We have designed, analyzed, and fabricated a microactuator based on the electrochemical principle. Preliminary experiments have proved that the bubbles generated in electrolysis can be manipulated by carefully controlling the direction and amplitude of the input signal. This has demonstrated that efficient pumping at micro volume of fluid can be realized by addition of required valves. The microfluidic system with micropump and integrated active microvalve has been successfully demonstrated. The working principle, design, simulation, and preliminary results of the electrochemical actuator have also been presented in the dissertation.



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Committee Chair

Wanjun Wang