Stretchable Elastomer Strain Sensor Based on a Three-Dimensional Cross-Linked Conductive Network of Polyaniline/3-Aminobenzenesulfonic Acid-Epoxidized Natural Rubber for Human Motion Monitoring

Flexible strain sensors, as crucial components of smart wearable devices, have garnered significant attention in fields such as human health monitoring. However, developing flexible strain sensors with high strength, sensitivity, extensibility, and long-term stability remains a challenge. In this study, a straightforward method was successfully developed for fabricating a cross-linked, conductive flexible strain sensor based on polyaniline/3-aminobenzenesulfonic acid-epoxidized natural rubber (PANI/3-ABSA-ENR) with a cross-linked structure. This was achieved by grafting 3-aminobenzenesulfonic acid (3-ABSA) onto epoxidized natural rubber (ENR) nanospheres, followed by in situ polymerization of aniline (ANI) onto the rubber nanospheres to form an effective cross-linked structure. At a PANI content of 13 wt% (PANI/ENR), the conductive flexible strain sensor exhibits outstanding comprehensive performance. Consequently, this strain sensor demonstrates ultra-high tensile strength (approximately 10 MPa), a wide strain range (approximately 1200%), and long-term reliability (2500 cycles at 50% strain). Simultaneously, the PANI/3-ABSA-ENR strain sensor exhibits a high gauge factor (GF = 21.6) and short response time (230 ms). Furthermore, this strain sensor can detect and capture both subtle and large-amplitude human motion signals, such as those from limb joints, cheeks, and mouth. This demonstrates the PANI/3-ABSA-ENR strain sensor's broad application potential in smart wearable devices.