Origami-inspired electret-based triboelectric generator for biomechanical and ocean wave energy harvesting

One of the critical issues for the conventional TENGs for applications in biomechanical and blue energy harvesting is to develop adaptive, simple-structured, high performance but low-cost TENGs for the complex excitation conditions. To solve this problem, we propose an origami-inspired TENG integrated with folded thin film electret, which can be facilely formed from two pieces of liquid crystal polymer (LCP) strips through high degrees of paper folding. It has been proved efficient for harvesting energy from both sinusoidal vibrations and impulse excitations which are universally existed in the ambient environment. Double-side corona discharging process is employed to maximize the charge density generated by the electret thin films. Attributing to the excellent elastic property of self-rebounding spring structures based on the origami design, the flexible TENGs can be readily integrated into smart shoes, floors, watches and clothes for wearable and energy harvesting applications. Triggered by impulse excitation of gentle finger tapping, instantaneous open-circuit voltage and short-circuit current of 1000 V and 110 μA, respectively, have been obtained with a remarkable peak power density of 0.67 mW/cm³ (or 1.2 mW/g). A spherical floating buoy generator integrating multiple origami TENGs is further developed to harvest ocean wave energy at various frequencies and amplitudes as well as in arbitrary directions. The outcomes of this work offer new insights of realizing single structured TENG designs for multifunctional applications.