Doctor of Philosophy (PhD)


Mechanical Engineering

Document Type



The objective of this research work is to develop a centrifugal microfluidic system for general purposes based on microfabrication technologies including SU-8 photolithography, polydimethylsiloxane (PDMS) casting. The main contribution of this research is to integrate a flyball governor system into the polymer based centrifugal microfluidic platform. A series of function units are developed based on this unique mechanism. In the first part, three pinch valve systems were designed and tested. The first one is based on the magnetic force and the second one is on the basis of spring force and the last one is a membrane valve. All valving system demonstrate good control of the fluid movement. The latter two valves are capable of sequential control. It proves that the flyball governor system is very compatible with centrifugal fluidic technologies. The major advantage of this new actuation technology is that its burst frequency can be conveniently manipulated by adjusting the parameters of the mechanical system without changes in the fluidic pattern. Next, two types of inward pumping systems were designed and tested. The result shows that both the inward pumps were capable of the pumping over a radial distance of 21mm in a short time. It thus improves the usage of space on the disc and paves the way to interconnect several functional units. Then as a proof of concept, a sequential valving system capable of metering and centrifugal sediment was developed for plasma extraction from whole blood. The resulting residual cell concentration was less than 0.5%. In the last part, a micromixer was developed based on the similar principle. The results show that the flyball governor system can effectively agitate the chaotic mixing of the sample liquids by periodically deflecting the PDMS membrane of the mixing chamber. The mixing effect can thus be enhanced.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Wang, Wanjun