Metal-doped functional zinc oxide nanosheets as flexible piezoelectric generator for self-powered mechanical sensing

The development of self-powered active mechanical sensors, which enable tactile sensing capabilities for soft robotics, has been substantially accelerated by the invention and rapid advancement of piezoelectric nanogenerators that harness mechanical energy from the environment as electricity. However, fabrication methods and sensory output expansion of nanogenerators are still challenging to meet the stability and durability requirements during prolonged use. In this work, metal-doped zinc oxide nanomaterial-polymer composites are prepared, characterized, and fully embedded in the flexible substrates to fabricate piezoelectric sensors with enhanced output performance and sensing capabilities. The flexible device can generate an open-circuit voltage up to 13.6 V when the applied force is 8 N at 3 Hz. In addition, these lead-free composite devices exhibit remarkable elbow motion detection sensitivity, providing a tremendous potential for precise human body motion sensing. Further, based on the sensors, a biomimetic soft robotic fin with mechanosensation has been developed, which can measure both the amplitude and frequency of the flapping of the fin ray. These findings not only shed new light on the development of functionl piezoelectric nanogenerators, but also lay the framework for advanced ambient sensing capacities of underwater organisms or robots.