In micro satellites, delicate instrumentations are compacted into a limited space. It raises concerns of active cooling and remote cooling. Silicon based micro-pump arrays are employed thanks to manufacturing simplicity, a small cryogen charge, etc., which keeps the instrumentations within a narrow cryogenic temperature range. The mechanical performance of the silicon diaphragm, the key component of the micro-pump, is critical in terms of heat balance calculation and life time evaluation. This paper examines the mechanical performance of the silicon diaphragm under cryogenic temperature for micro satellite applications. In this work, differential pressure was used for the actuation of a single-crystal silicon diaphragm. Diaphragm deflection and stress distribution were achieved using interferometry and micro Raman spectroscopy, respectively. As a result, a higher elastic modulus was associated with the diaphragm under cryogenic temperature, comparing to that under room temperature, indicating a stiffer material. From stress mapping, the edge centers were believed to be the most vulnerable to fracture, which was further validated by analyzing the fracture diaphragm. Moreover, a fatigue testing was conducted for 1.8 million cycles with no damage found, verifying thin film silicon as a viable material for long time operation in a cryogenic environment.

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