Stretchable and Highly Sensitive Flexible Strain Sensor Based on a Three‐Layer Core–Shell Structure of Polydopamine/Polypyrrole@Natural Rubber for Human Activity Monitoring

In recent years, flexible strain sensors with a wide detection range and high sensitivity have garnered significant attention for human health monitoring. However, fabricating strain sensors with a broad strain range while retaining high sensitivity remains a major challenge. Herein, a green and facile method is successfully developed to fabricate the polydopamine/polypyrrole@natural rubber (PDA/PPy@NR)‐based strain sensor with a three‐layer core–shell structure. PDA and PPy are coated uniformly onto the surface of the NR nanosphere by in situ polymerization. The electromechanical and strain sensing properties of the fabricated composite are investigated. The homogeneous coating of PPy and PDA layers has facilitated the formation of continuous conductive pathways within the NR matrix, even at low loading levels. Consequently, the strain sensor exhibits remarkable sensitivity over a wide strain range (≈800%) and long‐term reliability (2500 cycles at 50%). The PDA/PPy@NR strain sensor shows an exceptionally high gauge factor value (142.6) and a short response time (125 ms). Furthermore, this PDA/PPy@NR strain sensor can effectively detect and capture subtle and large human movements such as limb joints and facial movements as well as even distinguish the pronunciation of different words. The PDA/PPy@NR strain sensor holds great promise for integration into flexible wearable electronics.