A Resealable, Gas-Tight Packaging Technique for Silicon Microfluidic Devices

Recent efforts have led to the development of a silicon microfluidic cooling device known as the microcolumnated loop heat pipe (μCLHP). The μCLHP, like a traditional heat pipe, utilizes phase change of a liquid to rapidly draw heat away from a concentrated hot spot. Proper gas-tight packaging of this device is critical for the reliable testing of the recirculating fluid. This work presents a novel approach to filling and sealing the μCLHP. A miniature valve (Beswick M3SV-N) is bonded to the silicon fill ports of the μCLHP. The use of a resealable valve, as opposed to a permanent sealing method, allows the device to be filled, sealed, and then evacuated for testing with different fluids and at multiple pressures. Building on earlier work, the fill ports on the μCLHP were metalized with a Cr (10 nm)/Ni (200 nm)/Au (10 nm) stack. Then a lead-based solder was used to bond the stainless steel adapter to the metalized layers. Leak testing of devices sealed using these miniature valves demonstrated average hourly percent weight losses between 0.17% and 0.82%. While this bonding method has been developed specifically for the μCLHP, it is broadly applicable to most ceramic microfluidic devices, especially those fabricated from silicon and glass. Due to the time-intensive manufacturing process of microfluidic devices made from these hard materials, a novel, robust, resealing method that allows reuse of a single silicon microfluidic device for multiple test conditions is highly desirable.