Thermomechanical MEMS membranes for fiber optic temperature sensing

Abstract

In this study, the design, fabrication, and characterization results of square and circular cross-sectioned, bimaterial microelectromechanical system (MEMS) membranes are presented. The MEMS structures, having width of 250 µm to 1.5 mm and 1 4 mm2 die area, were designed towards integration on a single-mode fiber tip for temperature-sensing. Embedded diffraction grating underneath each membrane allows for interferometric detection of thermomechanical response through backside laser illumination. The displacement of MEMS membranes was monitored under direct heating, revealing 50 1800 nm/ ◦ C thermomechanical sensitivity range. Furthermore, atomic force microscopy-based stiffness measurement on the MEMS membranes revealed a spring constant within 2 30 N/m range. Temperature measurement range and speed of the MEMS sensors were thoroughly tabulated based on experimental findings, as well as finite-element simulations and analytical calculations. Finally, proof-of-concept testing of a selected device was accomplished through air-coupling of the MEMS structure with a gradient index-collimated fiber, revealing