Design, Analysis, Simulation, and Fabrication of a Novel Linear MEMS Capacitive Inclinometer

Abstract

Design, analysis, simulation, and fabrication of a novel MEMS capacitive inclination sensor is reported. Through precise analysis, a linear relationship between output capacitance and the inclination angle of the structure is extracted which is attributed to the parallel plate structure of the capacitance sensor and tilt-dependent movement of the dielectric liquid at various angles. Our proposed inclinometer has three structures with 1, 2, and 4 parallel plate micro capacitors in each configuration. Capacitors in different structures have a common plate while other plates are separate, so different capacitors are realized. The sensor cavity is cylindrical and is half filled with silicone oil. Tilt application to the sensor leads to oil movement in the cavity and variation of different capacitors in the structure. For an analytical expression, we introduce $C_{\mathrm {out}}$ as a function of different capacitors in each structure to obtain a linear and continuous relation with tilt. Furthermore, we simulate each structure using COMSOL Multiphysics and then test the fabricated samples. Extracted results from analysis, simulation, and performance tests are in a good accordance. Obtained results reveal that the double capacitor structure has a high sensitivity of 32.2 mV/° in the range of ±90° while four-capacitor structure has a measurement range of ±180° (full turnover) with a sensitivity of 10.1 mV/°. High sensitivity, wide linear range besides simplicity of the structure, are advantages of the proposed inclination micro-sensor.