Self-powered sensing is a sensing operational principle under which a sensor node harvests all required electrical working energy directly from surrounding ambient energy sources instead of relying on external wired power supply connections or pre-installed chemical batteries ^[1]. Available ambient energy forms that can be harvested include mechanical vibration, kinetic motion, thermal temperature gradients, ambient light illumination and environmental electromagnetic radiation ^[2]. The harvested energy is conditioned, regulated and stored locally to power sensor transduction, signal processing and data transmission functions. This concept defines the energy supply mechanism of the sensing node. It imposes no inherent restriction on the types of physical measurands, sensor transduction principles or signal output formats of the sensing device itself, and is applicable across temperature, vibration, chemical, biological and other sensing modalities ^[3].