Piezoresistive Elastomer Composites Used for Pressure Sensing

Abstract

Pressure sensors with capability to detect small physical movements and mechanical deformations have been widely used in wearable and medical applications. However, devices that are commercially available currently require complex designs and fabrication and present only a limited force-range sensitivity. To simplify the design, a thermoplastic polyurethane (TPU)/carbon nanotubes (CNTs) composite film has been developed using a melt extrusion technique followed by compression molding. Pressure sensors were made from these films, whose piezoresistive response has been analyzed as a function of the concentrations of CNTs, around the percolation threshold. The changes in the voltage of the device with applied pressure were continuously measured using a voltage divider system coupled with an electromechanical test machine that dynamically loaded the sensors under compression. The voltage divider system was tuned to obtain the best sensitivity and signal/noise (S /N) ratio for each device tested. The results showed that sensors containing a target of 2.5 wt% CNTs had market leading sensitivity and repeatability during long-term stability testing and showed high durability during underwater testing, indicating that such devices can be used as a promising robust pressure-sensitive sensor in wearable devices.