Non-Resonant Vibration Energy Harvester with Wound Micro-Coil Arrays

This paper describes a wrist-wearable non-resonant vibrational energy harvester (1.4 cc in volume and 3.2 gram in weight, with two arrays of wound copper coils adjacent to a movable array of magnets suspended by ferrofluid bearing) for generating power from a human’s walking motion. Thousand-turn coils are wound with a customized coil winding machine, and two sets of such coils are mounted on the top and bottom of a movable magnet array to obtain 20% improvement (compared to the earlier version based on an electroplated coil array) on the figure of merit (FOM) defined to be the power (delivered to a matched load) divided by the device’s volume for a given acceleration of 1 g at 2 Hz.