Triboelectric nanogenerator (TENG) technology is a promising research field for energy harvesting and nanoenergy and nanosystem (NENS) in the aspect of mechanical, electrical, optical, acoustic, fluidic, and so on. This review systematically reports the progress of TENG technology, in terms of energy-boosting, emerging materials, self-powered sensors, NENS, and its further integration with other potential technologies. Starting from TENG mechanisms including the ways of charge generation and energy-boosting, we introduce the applications from energy harvesters to various kinds of self-powered sensors, that is, physical sensors, chemical/gas sensors. After that, further applications in NENS are discussed, such as blue energy, human-machine interfaces (HMIs), neural interfaces/implanted devices, and optical interface/wearable photonics. Moving to new research directions beyond TENG, we depict hybrid energy harvesting technologies, dielectric-elastomer-enhancement, self-healing, shape-adaptive capability, and self-sustained NENS and/or internet of things (IoT). Finally, the outlooks and conclusions about future development trends of TENG technologies are discussed toward multifunctional and intelligent systems.

The rapid development of the fifth-generation mobile networks (5G) and Internet of Things (IoT) is inseparable from a large number of miniature, low-cost, and low-power sensors and actuators. Piezoelectric micro-electromechanical system (MEMS) devices, fabricated by micromachining technologies, provide a versatile platform for various high-performance sensors, actuators, energy harvesters, filters and oscillators (main building blocks in radio frequency (RF) front-ends for wireless communication). In this paper, we provide a comprehensive review of the working mechanism, structural design, and diversified applications of piezoelectric MEMS devices. Firstly, various piezoelectric MEMS sensors are introduced, including contact and non-contact types, aiming for the applications in physical, chemical and biological sensing. This is followed by a presentation of the advances in piezoelectric MEMS actuators for different application scenarios. Meanwhile, piezoelectric MEMS energy harvesters, with the ability to power other MEMS devices, are orderly enumerated. Furthermore, as a representative of piezoelectric resonators, Lamb wave resonators are exhibited with manifold performance improvements. Finally, the development trends of wearable and implantable piezoelectric MEMS devices are discussed.