Highly Stretchable, Responsive Flexible Dual‐Mode Magnetic Strain Sensor

Abstract Stretchable strain sensors with high stability, high responsiveness, and low detection limit provide the broad potential for intelligent robots and electronic skin. However, developing low‐cost strain sensors with contact and non‐contact sensing modes remains a significant challenge. In this study, a flexible magnetic strain sensor based on a sandwich structure is proposed to address this challenge. The proposed structure utilizes the coordination between carbon black and Fe₃O₄ microparticles in the silicone rubber matrix to enhance the sensor's sensitivity to external strain and magnetic stimuli. The sensor exhibits excellent tensile properties with a strain range of up to 180%, fast response/recovery time (78 ms/65 ms), high stability, and durability after 9000 cycles. Moreover, the flexible magnetic strain sensors can detect micro‐vibration and micro‐strain signals. It can also be performed as electronic skin to precisely sense human movements. Furthermore, the newly developed sensor can accurately sense oncoming objects and bicycle riding speed/distance, and a flexible magnetic keyboard is conceived. Consequently, the dual‐modal magnetic strain sensor exhibits an excellent ability to identify contact and non‐contact states and has broad application prospects in next‐generation intelligent products.