Integration of slanted tether check-valves for high pressure applications

We present a new approach to assemble multiple parylene check-valves to create a new device for high pressure microfluidic applications. By assembling several residual-stress-enhanced slanted tether check-valves in series, the cracking pressure of several psi can be easily achieved. The valve is modeled by extended valve theory considering the unsteady flow effect at the beginning of ckeck-covering plate´s opening. A new equivalent diode model is also proposed to analyze and predict the check-valves´ microfluidic behavior. Check-valves with thermally pre-stressed slanted tethers are chosen due to its remarkable high cracking pressure of each single check-valve. The slanted tethers are made using linearized partial exposure lithography technique and the tensile stress of the tethers is controlled by annealed in different temperatures. The size of each packaged single check-valve can be as small as 2 mm in length and 850 μm in diameter and the final packaged device with several integrated check-valves is capable of regulating pressure up to several psi. The testing result shows a higher cracking pressure with more check-valves, proving the series additivity of this model and integration. With its small size and high pressure regulating capability, the new check-valve system can be used to perform high pressure control application where the implantation space is limited. Different kind of parylene check-valves can also be combined to reach different pressure range using this packaging approach.