Mechanically Robust and Ultrasensitive Natural Rubber/PEDOT:PSS Foam for Piezoresistive Sensors and Motion Monitoring

The development of low-cost and high-performance flexible polymer-based piezoresistive sensors is of great significance in the fields of human–machine interaction, motion monitoring, and wearable technologies. However, traditional polymer-based piezoresistive sensors are generally prepared by immersion and spray-coating of conductive fillers on polymer foams, and the conductive fillers are easy to fall off from the polymer framework under external stress, which makes it difficult for the sensor to meet the long-term use requirements. In this paper, a stable and high-performance piezoresistive foam sensor was fabricated by the cofoaming of natural latex and poly(3,4-ethylenedioxythiophene) (PEDOT):poly(styrenesulfonate) (PSS) to fabricate NR/PEDOT:PSS foam. The PEDOT can be uniformly distributed in the NR latex. The PSS with emulsification feature also introduces a secondary pore in foam. This as-prepared foam with a hierarchical porous structure has the merits of easy fabrication, robust mechanical properties, excellent flexibility, good reproducibility (1000 cycles), and durability. Additionally, the foam exhibits a wide sensing range, fast response (140 ms), and recovery time (120 ms). These advantages enable the sensor to effectively differentiate between the movements of different joints and various behaviors. Furthermore, it can also provide excellent sensing capabilities for gait monitoring and fall warning. Overall, the prepared NR/PEDOT:PSS foam demonstrates significant potential applications in wearable electronics.