This thesis presents a vlaveless thermopneumatic micropump using surface tension. This micropump uses the surface tension and capillary attraction to control the flow for simple structure without any moving part such as a membrane or valve. In this dissertation, the influences of geometries of the micro channel and micro pillar on the performance of the micropump are compared. Commercial finite volume method (FVM) simulation software is used to simulate micropump operations.
First, theories of microfluid mechanics are presented in chapter 2. And the valveless thermopneumatic micropump with simple structure is designed, fabricated, simulated and tested in this chapter. This micropump discharges the fluid using thermopneumatic pressure and fills the fluid using negative pressure and capillary attraction. And during the refill time the micro channel works like a valve using surface tension. Therefore the flow can be controlled without any additional components. This micropump operates at 3.5V for 4 seconds to discharge and its size is 11.7 x 8.8 x 0.7 cm3. And the height of micro structure is 80 ㎛.
Second, various micropump geometries are designed to improve the micropump performance especially to reduce the backward flow loss. In the chapter 3, the influences of the micropump geometries such as the channel direction angle and the expansion angle on the micropump performance are compared with experimental tests and FVM simulations. In this chapter, six different geometries of micropumps are designed with three different channel direction angles and two different expansion angles. For more accurate comparison, three geometries with the same effective pump chamber are additionally designed. In this chapter, micropump size is 11.7 x 8.8 x 1.7 cm3 and the height of the micro structure is 100 ㎛. And these pumps discharge 120 nL for 4 - 7seconds. The channel direction angle affects to the backward flow loss and the expansion angle affects to the refill time and backward flow loss.
Third, micro pillar structures are designed to improve the efficiency of the micropump operations especially to reduce the backward flow loss and discharge time. And the influences of geometries of the micro pillars on the micropump performance are compared with experimental tests and FVM simulations. Various micro pillar structures are designed with four different locations and five different sizes. Micro pillar structures increase the surface area and the surface tension. Therefore they reduce the backward flow loss. In this chapter, micropump size is 11.7 x 8.8 x 1.7 cm3 and the height of micro structure is 100 ㎛. And these pumps discharge 100 nL for 4 seconds. And locations and sizes of the micro pillar structures affect to the backward flow loss.