Development of high sensitivity composite sensors for proprioceptive applications

Abstract

This study describes the fabrication of extremely sensitive piezoresistive composite sensors designed to detect human motion and speech. Starting out, a solution of thermoplastic polyurethane (TPU) was formed in dimethyl formamide (DMF) with a concentration of 35 % weight to volume. The solution was subsequently spun using a custom-built centrifugal spinning setup to produce TPU fibers. Following their fabrication through spinning, TPU fibers were immersed in a solution of carbon nanoparticles (CNPs) dispersed in tetra hydrofuran (THF), having a concentration of 25 %w/v, for dip coating TPU fibers with CNPs. This resulted in the formation of highly piezoresistive fibers having strain sensing capability. These fibers were then spun into the form of a yarn and tested as a strain sensor for proprioceptive applications. The composite sensors exhibited exceptional repeatability in tests involving continuous stretching and relaxing for more than 5000 cycles. The composite strain sensor demonstrated remarkable extensibility as well. The composite strain sensor was attached to different body parts such as the elbow, knees, fingers, and ankles to detect and track motion. It was found that the sensor could measure and track the angle, position, and frequency of motion in all of these scenarios. The sensor's remarkable sensitivity allowed it to detect different spoken words and letters, in addition to recognizing the action of swallowing in humans. The results show that the newly developed composite strain sensors are suitable for proprioceptive and speech recognition applications in soft robotics, wearable devices, and human-machine interactions.