Mechanochromic suction cups for local stress detection in soft robotics

Advancements in smart soft materials are enhancing the capabilities of robotic manipulators in object interactions and complex tasks. Mechanochromic materials, acting as lightweight sensors, offer easily interpretable visual feedback for localized stress detection, structural health monitoring, and energy-efficient robotic skins. Herein, an innovative mechanochromic soft end-effector capable of discerning local contact stresses during mechanical interactions with objects is presented and their relative position is ascertained. This system utilizes a reversible force-induced color switch in a thin layer of spiropyran-functionalized polydimethylsiloxane, which coats a silicone-made suction cup. The mechanochromic suction cup is integrated with a 3D-printed compact load-transferring system and electronic color-changing detection elements. The assembly may serve as a synthetic receptor for robotic actuators, discerning localized interaction forces down to 3 N. The system's resilience to varying environmental factors, including illumination, tilting, and interaction with objects of various shapes is verified. The results indicate potential for exteroceptive solutions in reconfigurable manipulation tasks without compromising the overall softness of the manipulator.