Studies On Drives For Microfluidic System

Despite the strong impetus in advancement of fluid drives for microfluidic system in the past decade, as evidenced by the multitude of micropumps developed, integration of driving systems on the microfluidic chip as well as the development of reliable microfluid driving systems still remained to be a challenge. Based on a review of existing micropumps, in the work systematic studies were conducted on PDMS pneumatic micropumps, micropumps based on evaporation and absorbion, micropumps based on capillary and evaporation, on-chip integrated micropumps based on capillary and evaporation.Fabrication processes and structural parameters of PDMS pneumatic micropumps were optimized. Major factors in the fabrication of PDMS pneumatic micropumps are the formation of arc-shaped channel profiles of the molding masters and bonding PDMS layers as well as bonding between the PDMS layer and the glass slide. Among three materials studied, AZ4620 positive photoresist demonstrated the best performance as a positive master for producing a liquid channel with an ideal cross sectional profile. Among the three bonding modes studied, bonding following plasma cleaning showed the best result and was used as the bonding means for fabricating PDMS pneumatic micropumps. For the first time, systematic studies were conducted on the factors affecting the flow rate, including control channel widths, activation frequency, activation pressure, liquid channel ratio of depth to width and liquid channel width. The optimized parameters were control channel width, 1000μm; liquid channel, 150μm; liquid channel ratio of depth to width, 0.1; activation frequency, 20-30Hz, activation pressure, 60KPa. Under such conditions, the maximum flow rate achieved was 0.55μL/min, which is about a factor of 4 higher than similar micropumps reported elsewhere, and the maximum endurable back pressure was 110cm water column.A micropump based on evaporation and absorbion works on the mechanism that the vapour evaporated from the driven flow was absorbed by a desiccant. The micropump composed of a compartment for liquid storage, a compartment for desiccant storage, and the compartment for avoiding the liquid contacting with the desiccant. The micropump could be used repeatedly by including a threaded screw in an orifice of the desiccant compartment. The micropump was characterized by simple configuration, low cost, easy...