Vacuum-assisted self-powered microfluidic pumping for lab-on-chip (LOC) application
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A simple method to enhance self-powered microfluidic devices is proposed. Powered by pre-evacuation of high-gas soluble PDMS, the microfluidic devices do not require external pressure sources during pumping process . In order to enhance the performance of such self-powered devices, different microstructures surrounding the channels and varied the sizes of outlet chambers are designed. Factors that could increase pump characteristics are also studied. In addition, the low pressure at the microstructures of the devices could be employed as temporary adhesive force for a microfluidic sticker. The equilibrium concentration of gas dissolved in PDMS is proportional to the gas' pressure around PDMS. After degassing the PDMS devices at low pressure, the PDMS bulk will re-absorb air to reach a new equilibrium after exposing to atmosphere . By loading liquid at the inlet, the relative lower pressure inside the channel will draw the liquid within, acting as a pump. Further, by adding different microstructures beside the channels, we expect enhanced air-suction in the channels, thus increasing the flow rate. The key factor affecting the flow rate is the surface area of air remaining in the chamber and the channel. The larger is the surface area, the faster the flow rate. In addition, since low pressure could be generated in microstructure cavities, we expect such patterns of microstructures will further enhance reversible bonding between PDMS and glass. Using different microstructures and variable sizes of outlet chambers, the self-powered pump could be linearly controlled. It is successfully realized that the self-powered pump by employing microstructures and varying surface ratios for enhanced self-powered pumping, as well as utilizing the devices as microfluidic stickers. By proposed method in this thesis the structures designed in this thesis will be useful to create simple self-powered point-of-care microfluidic devices.