A bioinspired multi-functional wearable sensor with an integrated light-induced actuator based on an asymmetric graphene composite film

Designing smart materials which couple sensing and actuation similar to human skin is highly desirable in applications of smart wearable systems and biomimetic robots, but marginally explored. Here, we develop a smart graphene composite film with an asymmetric structure that presents both wearable sensing and actuation. This asymmetric graphene-coated paper-based composite film is fabricated by simply repeated immersion and drying, and a subsequent reduction method. It can be directly used as a resistance-type strain sensor for distinguishing the bending deformation direction with fast response (79 ms), which is mainly attributed to the asymmetric graphene distribution of the film on both sides. Diverse human body motions from large-scale motions to subtle tactile signals, including wrist bending in different directions, a pulse wave, and finger touching of objects can be detected by this sensor. Besides sensing, light-induced actuators with large deformation (0.29 cm^-1 in 8 s) and color change and complicated biomimetic devices such as artificial flowers and crawling robots are constructed based on this smart film. More importantly, combined with sensing and actuation, multi-functional wearable sensors with light-driven deformation and color-change mimicking human skin are constructed, indicating the great potential of this integrated design of sensing and actuation for next-generation smart wearable systems.