Study On Novel Passive Micro-valve Based On SU-8

Microfluidic control system, multifunctional mobile net-work, which is composed of microscale channel, can complete injection, mixing and separation of micro fluid. Micro valve plays a very important role on microscale flow control system, its reliability, integration and processing cost have great impact on the entire micro fluidic control system. As a key executive component in micro fluid control system, micro valve is a flow control device, which realizes the fluid channel opening, c losing and fluid flow switching. Passive valve, also known as check valve., which can control liquid, gas or gas-liquid mixture along a specified direction of flow, but prevent the liquid, gas or gas-liquid mixture phase from flowing reversely. The check valve will open only in positive pressure, which is similar to light emitting diode in the integrated circuit.Since most passive valve is integrated in rec iprocating pump inlet or outlet as a control component, the performance of check valve has a great impact on micro pump. The micro pump output efficiency will be reduced because of leakage of passive valve. Previous ly, many kinds of passive microvalve were fabricated by etching of silicon, which has already been used in micro fluid control system. But micro valve made of silicon has the difficulty of package and poor biological compatibility, which limited its application. With the development of MEMS technology, the appearance of polymer micro device provides very good solution to this problem. Polymer materials have good biological compatibility, low cost and good performance, such as PDMS, Parylene C and SU-8, have been applied in micro fluid control field.To control the velocity and one-way flow of fluid in micro-fluidic system, firstly, a novel passive micro-valve is designed with valvular structure of human being used for reference. Using SU-8 as the passive micro-valve structure materials,and the deflection and stress of valve membrane under different pressure were analyzed with ANSYS, then design of the valve membrane was optimized.Then two types of micro-valves were fabricated using a non-silicon surface micro-fabrication process. The details and the key steps in fabrication process were investigated. Finally, the performance of the passive valve was tested using deionized water as media. The forward flow velocity 1.66ml/min of type A and 1.35ml/min of type B were observed under the forward pressure of 11.7Kpa. The designed passive valve has the potentiality of linear control according to the data tested. Passive micro-valve made of SU-8 has not only better performance, which could extend the application of passive micro-valve.