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The research on harvesting the wasted mechanical energy and using it as a useful energy source has been in the spotlight. Conventional ceramic-based devices have disadvantages such as mechanical brittleness and high-temperature processing. To overcome these weaknesses, the piezoceramic materials mixed with polymer matrix have been studied to produce flexible piezoelectric devices. Herein, a piezoelectric composite film is fabricated by mixing lead-free 0.942[Na0.535 K0.480NbO3]-0.058LiNbO3 (KNNLN) nanocube powder with polydimethylsiloxane (PDMS) matrix. KNNLN nanocube powder is synthesized by a solid-state reaction method, which can typically present outstanding stoichiometric composition and perovskite crystalline structure. The cube-shaped particles are thought to show higher stress concentration at corners and edges of the nanocube than spherical particles when external mechanical input is applied. The flexible KNNLN nanocube–PDMS nanocomposite device generates the piezoelectric signals of ~ 28 V and ~ 220 nA during bending motion, which is a high-performance energy harvesting efficiency compared to previous KNN-based flexible piezoelectric composites generators. KNNLN nanocube-based composite can replace toxic lead-based nanocomposites for future flexible devices such as eco-friendly self-powered energy harvester and biocompatible sensor.

Two-dimensional (2D) transition metal dichalcogenide (TMDC) nanomaterials are currently regarded as next generation electronic materials for future flexible, transparent, and wearable electronics. Due to the lack of compatible synthesis and study, however, the characteristic influences of 2D TMDC nanomaterials have been little investigated in the field of triboelectric nanogenerator (TENG) devices that are currently one of the main technologies for mechanical energy harvesting. In this report, we demonstrate a fast, non-vacuum, wafer-scale, and patternable synthesis method for 2D MoS2 using pulsed laser-directed thermolysis. The laser-based synthesis technique that we have developed can apply internal stress to MoS2 crystal by adjusting its morphological structure, so that a surface-crumpled MoS2 TENG device generates ~40% more power than a flat MoS2 one. Compared to other MoS2-based TENG devices, it shows high-performance energy harvesting (up to ~25 V and ~1.2 μA) without assistance from other materials, even when the counterpart triboelectric surface has a slightly different triboelectric series. This enhanced triboelectrification is attribute to work function change as well as enlarged surface roughness. Finally, the direct-synthesized MoS2 patterns are utilized to fabricate a self-powered flexible haptic sensor array. The technique we propose here is intended to stimulate further investigation of the triboelectric effects and applications of 2D TMDC nanomaterials.

Triboelectricity is a self-powered phenomenon that has recently attracted attention because it is capable of instantaneously generating a large amount of electrical power. In this study, we developed a method to fabricate a fabric-based triboelectric energy-harvesting device and enhanced the output of this device using a Fluorinert coating and ultraviolet (UV)/ozone surface treatment. Through simple surface treatment processes, the electrical output of triboelectric self-generation device will be significantly increased, and at the same time, it will present the possibility of being naturally suitable for next-generation electric clothing products.

The authors regret the late revision of our published article as follows. After publication of the article, the authors found that the Acknowledgements information was wrong.