Polydimethylsiloxane (PDMS) and polymethylmethacrylate (PMMA) are commonly utilized in microfluidics due to their high optical transparency, good biocompatibility, and ease of manufacture. However, conventional bonding techniques cannot produce sufficient bonding strength, which limits their applicability. This thesis represents a method for optimizing the interfacial bonding strength between PDMS and PMMA. Using the Taguchi approach, fabrication parameters were investigated by evaluating bonding strength (i.e., burst test pressure). Under ideal bonding circumstances, the microchannel assembly withstood air pressure greater than 770 kPa, liquid pressure greater than 622 kPa, and a tensile test greater than 3000 kPa. The bonding strength was sufficient to withstand liquid entry at a rate 6800 times greater than the microchannel's volume per minute. This indicates that the interfacial bonding was permanent, as the microdevices could tolerate such severe pressure without damage. Then, the proposed manufacturing technology was utilized to manufacture microfluidic devices that could handle an extraordinarily high liquid pressure of 402 kPa, high flow rates surpassing 120 mL/min, and dense microchannels with a spacing of only 30 µm. This proposed bonding approach was used to manufacture a functioning valve system with a high-density layout that may be used in microfluidics-based assays requiring high precision, rapid response, and the efficient management of liquid transportation.
Moreover, we successfully developed a novel integrated microfluidic device to separate blood plasma from human blood without using external valves or pumps. The concept is based on using a pneumatic peristaltic micropump (PPMs) integrated with a trapezoidal cross-section for blood plasma separation. First, we proposed a fabrication process of PPM with high pumping rate by combining rigidly of PMMA and elasticity of PDMS. Following the procedure to achieve excellent bonding strength of PDMS/PMMA, the PPMs could be operated under high pressure. Then, the dynamic deflection test of PDMS membrane actuator under high pulsation frequency was performed. We proved that the PPMs have excellent actuator diaphragm dynamic behavior without any mechanical fatigue or dead volume, achieving the highest pumping rate of 3,500 µL/min. Then the micropump was integrated with a spiral microchannel with trapezoidal cross-section area and used to rapidly extract plasma from human blood within 3 minutes and with a small blood volume of 200μL, with the efficient separation up to 97%.

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