This study details the fabrication and measurements of a water-filled 5 mm wide by 10 mm long silicon microheat pipe (MHP) array consisting of 22–100 μm square channels. This study is unique in that many experimental results reported in open literature are for single channel microheat pipes. The number of channels in the array and the fluid charge used here were optimized under a separate study. A number of experiments were carried out on the specimen MHPs to determine their effective thermal conductivity and comparisons were made with previous results found in literature. The testing methodology was designed to remove systematic biases and the array thermal performance measurements are reported in terms of a silicon equivalence by identically measuring an uncharged empty silicon array as a baseline measurement. Two separate water-filled specimens were made, independently tested, and are reported to have thermal conductivities of 261 W/m K and 324 W/m K, representing a silicon equivalence of 1.8 and 2.2, respectively. All testing was performed in a horizontal orientation.

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Low–temperature bonding techniques are of great importance in fabricating MEMS devices, and especially for sealing microfluidic MEMS devices that require encapsulation of a liquid. Although fusion, thermocompression, anodic and eutectic bonding have been successfully used in fabricating MEMS devices, they require temperatures higher than the boiling point of commonly used fluids in MEMS devices such as water, alcohols and ammonia. Although adhesives and glues have been successfully used in this application, they may contaminate the fluid in the MEMS device or the fluid may prevent suitable bonding. Indium (In) possesses the unusual property of being cold weldable. At room temperature, two sufficiently clean In surfaces can be cold welded by bringing them into contact with sufficient force. The bonding technique developed here consists of coating and patterning one Si wafer with 500A Ti, 300A Ni and 1 μm In through electron beam evaporation. A second wafer is metallized and patterned with a 500A Ti and 1 μm Cu by electron beam evaporation and then electroplated with 10 μm of In. Before the In coated sections are brought into contact, the In surfaces are chemically cleaned to remove indium-oxide. Then the sections are brought into contact and held under sufficient pressure to cold weld the sections together. Using this technique, MEMS water-filled and mercury-filled microheatpipes were successfully fabricated and tested. Additionally, this microfabrication technique is useful for fabricating other types of MEMS devices that are limited to low-temperature microfabrication processes.