Design and Optimization of an Ultra-Sensitive Piezoresistive Accelerometer for Continuous Respiratory Sound Monitoring
Abstract:This paper reports the design and optimization of a novel piezoresistive accelerometer for continuous respiratory sound monitoring. Unlike the traditional piezoresistive accelerometer where the piezoresistor directly lies on the surface of the suspension beam, this new design employs a decoupled piezoresistive layer. Such an innovative design makes it possible for the majority of the strain energy to be stored in the piezoresistive layer and therefore increases the signal to noise ratio significantly. An analytical model is developed based on the mechanics of materials method and is later verified using finite element simulation. The specifications of the device such as sensitivity, natural frequency, and minimum detectable acceleration are theoretically calculated. The optimization of the new accelerometer by choosing appropriate dimensions for the proof-mass and cantilevers, and doping concentration is discussed in this paper as well. Simultaneously, some issues that are unique to this new design, such as buckling, are addressed. Compared with the traditional design, this new design shows great advantages in both sensitivity and minimum detectable acceleration. A specific design for continuous respiratory sound monitoring with a bandwidth of 6 kHz, a 5 mm3 proof mass (0.0117 gram), a sensitivity ((ΔR/R)/a) of 4.7 × 10−4 s2/m and a resolution of 3.4 × 10−6 ms−2/Hz1/2 is presented.
Document Type: Research Article
Publication date: 2007-06-01
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