Study On The Phase Changing Valve In Microfluidic Chip

Micro Total Analysis System (μ-TAS) has many advantages, such as high integration, low consumption, convenient using and so on. It has aroused a wide range of applications. Micro fluid should be controlled effectively inμ-TAS when it is under working state, which should be fulfilled by valves. And the valves should be efficient and reliable. The phase changing(PC) valve can be used to control the closing/opening of microchannel by freezing/melting the local fluid. It is suitable forμ-TAS. Therefore, the PC valve has attracted widely attention.The mathematical model of the PC valve was established; the numerical simulation of the PC valve was performed; the microfluidic chip which integrated the PC valve was fabricated; the operating characteristics of the PC valve were tested.The research object is the incompressible Newtonian fluid in electroosmotic or pressure driven. The micro fluid movement was described by N-S equation and continuity equation, the micro fluid energy transmission and the generations of the phase change were described by heat conduction equation and phase-change equation. The numerical simulation of the PC valve in the electroosmotic and pressure driven were performed respectively. Comparing to the cooling power density in pressure driven, the cooling power density in electroosmotic driven which makes the microchannel close is much bigger in the same driven flow. The reason is that joule heat is induced in electroosmotic driven.According to the chips requirements of test experiments and the characteristics of the different chip materials in the fabrication process, Polydimethylsiloxane(PDMS)-Glass-PolymethylMethacrylate(PMMA) microfluidic chip and PMMA-PMMA microfluidic chip had been designed and fabricated in the paper. The structure and fabrication process of these two chips were introduced. The driven equipment of PC valve is commercial semiconductor cooling device.Test platforms in electroosmotic and pressure driven were setted up respectively, according to the gradient of conductivity from liquid state to solid state, the time of closing the channel by the PC valve was tested. The less the driven voltage or pressure were, the more the cooling power density was, and the function of the PC valve can implement easily.