Rotational energy harvesting for self-powered sensing

Advances in wireless sensors, biomedical devices, and micro-robotics exert more pressure on creating reliable, miniaturized, and self-sustained energy supply solutions for these micro-electrome-chanical systems. Rotational energy harvesting (REH) is one of the rapidly growing areas for self-powered electronics using available rotational energy or energy converted from other sources in the environment. This paper comprehensively reviews the state-of-theart progress in REH in terms of the available energy characteristics, harvester categories, adopted methodologies and mechanisms, and promising applications. Unique mechanisms and methodologies, such as using gravity and centrifugal force combined with other nonlinear mechanisms, are discussed and characterized. In terms of applications, wearable and implantable devices, automotive, rotating machines, renewable energy systems, and environmental sensing are discussed and reviewed to illustrate how rotational energy harvesters have been developed and adopted accordingly. Based on progress to date, the key developments, critical challenges, and issues are summarized and discussed. Moving forward, an outlook is presented to outline potential research directions and opportunities in this area.