Broadband Magnetic Composite Energy Harvester

Energy from ambient vibrations is a potential source for powering the multitude of sensing and computing systems that comprise the internet of things. In order to exploit the broadband nature of natural low frequency vibrations, a magnetic composite energy harvester that has a dual resonant response in the sub–100 Hz region is presented by the authors. A unique structure composed of a proof mass mounted on an array of high aspect ratio, bioinspired hair like structures called cilia is fabricated using polydimethylsiloxane (PDMS) − NdFeB magnetic microcomposite. This structure has a frequency response comprised of two closely spaced resonant peaks facilitating the desirable broadband behavior at low frequency. Each cilium is shaped like a conical frustum with a top diameter of 200 μm and a bottom diameter of 450 μm and has a height of 3 mm, while the proof mass is cuboid with dimensions of 12 × 12 × 8 mm3. This composite structure is fabricated on top of a micromachined 1 cm2 planar coil, made up of 40 turns of 7.6 μm thick electroplated copper. The effect of material composition of the magnetic composite on the resonant frequencies, bandwidth, and energy harvesting performance of the device is studied.