A Fully Transient Mechanical Energy Harvester

Abstract Here, a novel design of a mechanical energy harvester combining peak power output competitive with state‐of‐the‐art energy harvester devices is reported, but with a design enabling full transience, or dissolution, of the harvester after 30 min upon triggering in basic water. The harvester incorporates a symmetric cell combining Li_xAl alloy electrodes and polyvinyl alcohol packaging that harvests mechanical energy due to the mechanical–electrochemical stress coupling between the electrodes. Prototype harvester devices demonstrate peak output power of 0.208 µW cm⁻² with continuous energy generation up to 1.76 µJ cm⁻² at a mechanical input frequency of 0.1 Hz. This work introduces a new class of power systems simultaneously tailored for transience, high‐performance energy harvesting, and operation frequency relevant to wearable technologies.