Flexible three-dimensional interconnected piezoelectric ceramic foam based composites for highly efficient concurrent mechanical and thermal energy harvesting

Flexible piezoelectric materials are pivotal to a variety of emerging applications ranging from wearable electronic devices, sensors to biomedical devices. Current ceramic-polymer composites with embedded low-dimensional ceramic fillers, though mechanically flexible, suffer from low piezoelectricity owing to the poor load-transfer efficiency that typically scales with the stiffness ratio of the polymer matrix to the ceramic fillers. Herein we introduce the scalable ceramic-polymer composites based on three-dimensional (3-D) interconnected piezoelectric microfoams. Comprehensive mechanics analyses reveal that the 3-D interconnected architecture presents a continuous pathway for load transfer to break the load-transfer scaling law seen in the conventional composites with low-dimensional ceramic fillers. The 3-D composite exhibits exceptional piezoelectric characteristics under multiple loading conditions (i.e., compression, stretching, and bending) and high mechanical durability under thousands of cycles. The 3-D composite also displays excellent pyroelectricity, thereby enabling concurrent thermal and mechanical energy scavenging. Our findings suggest an innovative material framework for high-performance energy harvesters and self-powered micromechanical devices.