AgNW Treated PU Nanofiber/PDMS Composites as Wearable Strain Sensors for Joint Flexion Monitoring

In this study, wearable polyurethane (PU) nanofiber-based silver nanowires (AgNWs)/polydimethylsiloxane (PDMS) composites were fabricated and demonstrated as strain sensors to monitor human arm joint movements, investigating electrical resistance change with deformation. With varying content of AgNWs (0.5 wt%, 0.75 wt%, and 1 wt%) in ethanol, PU nanofiber nonwovens were coated with the AgNWs followed by packaging and encapsulation process with commercial snap buttons and PDMS coating. Each sample's surface morphology was characterized by scanning electron microscopy (SEM). After the curing process at 50 degrees C for 2 hours, the fabricated sensors were integrated to textile-arm sleeves for the wear-trials with a dummy and three human subjects. Given that the resistance of the sensors were the lowest when treated with 1 wt% of AgNWs, the sensors initially showed increase in resistance according to bending motion while the excessive bending resulted in decreasing trend in resistance. Regarding the varying joint flexion speed (0.125-0.5 Hz), sensors with 1 wt% of AgNWs showed the best performance as wearable strain sensors with more accurate signals and stability even under higher frequency.