A self-powered three-dimensional integrated e-skin for multiple stimuli recognition

Real-time detection and differentiation of diverse external stimuli remains a huge challenge and largely restricts the development of electronic skins (e-skin). Hence, a versatile e-skin was developed by integrating a thermoelectric graphene/polydimethylsiloxane (PDMS) sponge with piezoelectric array, to minimize the coupling effect between thermal and mechanical excitations and distinguish different mechanical stimuli. Owing to the designed three-dimensional structure, the e-skin was capable of differentiating in-plane and out-of-plane force based on the corresponding induced strains. Besides, graphene/PDMS sponge was utilized as thermal tactile elements with a moderate temperature sensitivity of 0.122 mV/K. A wireless temperature sensing system was proposed for transmitting signals and “hot”/ “cold” tips to terminal devices. Importantly, the e-skin demonstrated excellent sensing performance on recognizing shear directions by 0°-180°. Therefore, a robotic gripper equipped the e-skin with detection of the “holding” and “slipping” motion exhibited promising prospects in artificial tactile feedback system with self-adjusting grip force. Moreover, the self-healing nature originated from shear stiffening elastomer matrix enabled that individual e-skin could be reassembled into an arrayed e-skin with the spatial tactile ability. This work provided a new strategy for designing functional e-skins, and paved the way for intelligent robotic technologies, including adaptive grasping, biomimetic robots, and human-machine interactions.