Highly–flexible, High–Performance and Stretchable Piezoelectric Sensor based on a Hierarchical Droplet–Shaped Ceramics with Enhanced Damage Tolerance

Stretchable self–powered sensors are of significant interest in next–generation wearable electronics. However, current strategies for creating stretchable piezoelectric sensors based on piezoelectric polymers or 0–3 piezoelectric composites face several challenges such as low piezoelectric activity, low sensitivity and poor durability. In this paper, we use a biomimetic soft–rigid hybrid strategy to construct a new form of highly flexible, high–performance, and stretchable piezoelectric sensor. Inspired by the hinged bivalve Cristaria plicata, hierarchical droplet–shaped ceramics were manufactured and used as rigid components, where computational models indicated that the unique arched curved surface and rounded corners of this bionic structure can effectively alleviate stress concentrations. To ensure electrical connectivity of the piezoelectric phase during stretching, a patterned liquid metal acted as a soft circuit and a silicone polymer with optimized wettability and stretchability served as a soft component that formed a strong mechanical interlock with the hierarchical ceramics. The novel sensor design exhibited excellent sensitivity and durability, where the open circuit voltage was shown to remain stable after 5,000 stretching cycles at 60% strain and 5,000 twisting cycles at 180°. To demonstrate its potential in healthcare applications, this new stretchable sensor was successfully used for wireless gesture recognition and the assessment of the progression of knee osteoarthritis.