Design Rules for a Wearable Micro-Fabricated Piezoresistive Pressure Sensor

Abstract Wearable flexible piezoresistive pressure sensors hold wide-ranging potential in human health monitoring, electronic skin, robotic limbs and other human-machine interfaces. Out of the most successful recent efforts for arterial pulse monitoring are sensors with micro-patterned conductive elastomers. However, low current output signal (typically in the range of nanoamperes), bulky and expensive measurement equipment for useful signal acquisition inhibits their wearability. Herein, through finite element analysis we establish the design rules for a highly sensitive piezoresistive pressure sensor with output that is high enough to be detectable by simple and inexpensive circuits to ensure wearability. We also show that out of four frequently reported micro-feature shapes in micro-patterned piezoresistive sensors, micro-dome and micro-pyramid yield the highest sensitivity. Furthermore, investigations of different conductivity values of micro-patterned elastomers found that coating the elastomer with a conductive material (usually metallic) leads to higher current response when compared to composited conductive elastomers. Finally, geometric parameters and spatial configurations of micro-pyramid design of piezoresistive sensor were optimized. The results show that an enhanced sensitivity and higher current output is achieved by lower spatial density configuration of 3 micro-feature per millimeter length, smaller feature size of around 100 µm, and 60-50 degrees pyramid angle.