Ultra miniature µ-accelerometer for wearable physical activity monitoring systems

This study presents the design, fabrication and characterization of an ultra miniaturized 3-axis accelerometer with implanted piezoresistive sensing elements and read out circuits are having nano-scale dimensions. It has been developed using MEMS/NEMS machining and fabrication techniques. This sensor consists of a new sub-millimeter structure with seismic mass and combined cross-beam and surrounding beams. It can detect three components of linear acceleration simultaneously. The sensitivity could be enhanced significantly while miniaturizing the die size of sensor chip with aid of novel structure and nanoscale piezoresistors on the sensing beams. Therefore, this novel proposed sensor is showing good performance and smaller than other comparable miniaturized sensor structures reported thus far. The accelerometer is capable of measuring accelerations up to ±20 g in the frequency bandwidth of 480 Hz. Comparison of the obtained experimental results and finite element simulation shows good agreement. This accelerometer is being introduced for a wearable physical activity monitoring systems.