Hierarchically designed nanocomposites for triboelectric nanogenerator toward biomechanical energy harvester and smart home system

Triboelectric nanogenerator (TENG) has realized broad application prospects in the internet of things, human-machine interfaces, artificial intelligence. Among the abundant material options, polymer-based nanocomposites are highly potential for triboelectric devices, owing to their flexibility, easy processing and especially tunable properties (dielectric constant, polarity, etc.) by various additives. At present, the widely used approaches for output performance enhancement of nanocomposite-based TENG are to boost the dielectric constant for improved charge storage ability and/or to enlarge the polarity difference of these triboelectric materials. Herein, we discovered that large amounts of dielectric additives would boost the dielectric constant while impair the triboelectric polarity of nanocomposites with degraded output performance. A hierarchical design strategy by additionally constructing a triboelectric coating on the high dielectric nanocomposites is proposed to balance the dielectric constant and triboelectric polarity of nanocomposites for enhanced triboelectric performance. The hierarchical nanocomposites possess a high dielectric constant (εr ~ 82.35 at 103 Hz) and optimized triboelectric polarity. Owing to the synergistic influence of dielectric incorporation and hierarchical design by triboelectric coating, an enhancement of short-circuit current density and maximum instantaneous power density by 4.1 and 23.1 times, respectively, are achieved. Theoretical mode of hierarchical nanocomposites is established to guide the design and optimization. A polymer dispersed liquid crystal film driven by TENG and its application in smart home system are demonstrated successfully. This work facilitates the exploration of multi-layered nanocomposite materials for high-performance TENG in biomechanical energy harvester and smart home system applications.