Enhancing structural response via macro-micro hierarchy for piezoelectric nanogenerator and self-powered wearable controller

Piezoelectric polymeric composites exhibit pronounced impact on flexible electronic devices, demonstrating the capacity to harvest high-entropy energy. Nevertheless, the conventional incorporation of piezoelectric ceramics is gradually approaching its limitations due to the unexpected increase in Young's modulus and the resulting deterioration in output. In this study, we propose a macro–micro hierarchical (MMH) design concept for the preparation of a polyvinylidene fluoride/barium titanate piezoelectric nanogenerator (PENG). Micro porosity is introduced into the macro truss structure through in-situ foaming additive manufacturing. Leveraging the synergistic effects of the micro-porous structure (stress concentration and piezoelectret) and the macro-truss design (strain accumulation), the output capacity, i.e., open-circuit voltage and short-circuit current of the MMH-PENG, is effectively amplified from 16.1 V and 350 nA to 24.5 V and 642 nA, respectively. Upon further integration onto a flexible substrate, the MMH-PENG exhibits compelling features, including substantial flexibility, controllable sensitivity, easy detachability, and reusability, facilitating practical applications as a wearable and self-powered controller. Illustrated by applications in video game and robotic controllers, the MMH-PENG introduces a pioneering concept that enhances output performance through the simultaneous construction of a macro–micro hierarchy, paving the way for potential large-scale utilization of piezoelectric nanogenerators.