Challenges associated with materials for high temperature pressure sensor designs, in excess of 1000°C, are explored here for future applications such as control of combustion processes and flow control of hypersonic vehicles. Currently, silicon based MEMS technology is primarily used for pressure sensing. However, due to the limited melting point of silicon, such sensors have a limited temperature range of approximately 600°C which is capable of being pushed towards 1000°C with active cooling. To overcome thermal limitations, the thermomechanical properties of sapphire are investigated to facilitate the design of an optical based pressure transducer which is designed to operate at temperatures approaching 1600°C. Due to sapphire's hardness and chemical inertness, traditional cutting and etching methods used in MEMS technology are not applicable. The proposed methodology for the sapphire based sensing technology is picosecond laser machining. Here we summarize the material property changes that occur from laser machining across temperatures ranging from room temperature to 1300°C. Both changes in elastic moduli and strength, as functions of laser machining and temperature, are quantified using four-point bending experiments. The results illustrate comparable or improved strength after laser machining while the modulus was reduced after laser machining at room temperature and 1300°C by a factor of 1.5 to 2.0.
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