Abstract
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 mu m and a bottom diameter of 450 mu m and has a height of 3 mm, while the proof mass is cuboid with dimensions of 12 x 12 x 8 mm(3). This composite structure is fabricated on top of a micromachined 1 cm(2) planar coil, made up of 40 turns of 7.6 mu m 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.