Flexible Strain Sensor With High Sensitivity Based on β‐Alanine‐Modified Epoxidized Natural Rubber Grafted Polypyrrole Conductive Composite

ABSTRACT Recent advancements have brought significant focus on wearable flexible strain sensors, primarily owing to their extensive applicability across various technological domains. Nonetheless, the development of flexible strain sensors with high sensitivity, high strength, and extensive strain range persists as a significant challenge in the field. In this study, polypyrrole (PPy) was uniformly coated on the surface of β‐alanine (Ala)‐modified epoxidized natural rubber (ENR) by in situ polymerization to prepare an A‐ENR‐g‐PPy composite with a core‐shell structure. The covalent bonding link between the polypyrrole and the epoxidized natural rubber helps to establish an effective conductive network within the epoxidized natural rubber matrix. As a result, the strain sensor has a fast response (153 ms) and excellent cycling stability (over 2000 cycles at 40% strain). The gauge factor (GF) is 5.4 for strain below 100%, reaching 6845.6 for strain above 550%. In addition, A‐ENR‐g‐PPy‐based flexible strain sensors can accurately monitor and differentiate between small and large body movements such as finger, wrist, elbow, and knee bending as well as mouth opening and blinking. This sensor shows great potential for applications in wearable flexible electronics.