A novel capacitive micro-accelerometer made of steel using micro wire electrical discharge machining method

A new method has been proposed to design and fabricate a metallic microelectromechanical capacitive accelerometer, in this paper. The conventional MEMS fabrication methods, as well as the micro wire electrical discharge machining (mu WEDM) method, have been employed to fabricate the proposed accelerometer. The mu WEDM offers several advantages including its capability for attaining a proof mass of higher thickness, as well as using dense metals, in the accelerometers, thus providing better control over noise reduction and damping. This sensor has the proof mass of 6.8 mg which leads to the low Brownian noise of 1.2 mu g/root Hz. The proof mass-beam structure of the accelerometer has been made of steel, which has higher yield strength and fracture toughness than silicon, enabling the accelerometer to withstand high-amplitude accelerations. Conducted tests showed that this sensor operates in the range of 100 g. Thanks to its low noise (due to the larger proof mass) and capability to measure high-amplitude accelerations (due to the high yield strength of steel), the dynamic range of the proposed accelerometer is improved considerably in comparison with the conventional MEMS accelerometers. The presented accelerometer is also operable in the air which facilitates its packaging