Renewable energy harvesting and absorbing via multi-scale metamaterial systems for Internet of things

Highlights: • Natural and human environments are abundant of unused renewable energy. • Metamaterials are able to enhance local energy density for improved energy harvesting. • An overview on multi-field energy harvesting via multi-scale metamaterials is provided. • The goal is to spark interest of new investigators to metamaterial energy harvesting. • Multiscale metamaterial based energy harvesting will benefit the Internet of things. -- Abstract: Natural and human environments are abundant of unused renewable energy such as mechanical energy, acoustic energy, electromagnetic energy, thermal energy, etc. The idea of designing multi-scale metamaterials with super-normal functions on energy manipulation is utilized in multi-field renewable energy harvesting and absorbing. The metamaterials are able to enhance the local energy density by confining and focusing the energy before it to be harvested, leading to remarkable improvement of the output power and conversion efficiency. Leveraging the multi-scale metamaterials for renewable energy harvesting is an emerging direction to exploit the excess energy in the natural and man-made environments. This paper provides a brief overview of the studies published over the past decade on mechanical, acoustic, electromagnetic and thermal energy harvesting using the relevant metamaterials. The goal is to spark the interest of new investigators to this unconventional but fast-evolving branch of energy harvesting that will impact the Internet of things, smart cities and sustainable developments.