Microfabricated thousand-turn coils for mW power generation from sub-mm vibrations

This paper presents two microfabrication approaches for 3D multiple-layer coils for vibration-energy harvesters. One type of coils is made out of 300 μm thick copper that is electroplated with silicon mold, and the other is built on 25 μm thick copper electroplated with photoresist mold. The latter approach is used to obtain 1,080-turn coil for microfabricated electromagnetic energy harvester with magnet array and plastic spring. Though the size and weight of the harvester are only 26×13×6 mm
³
and 12 gram, respectively, it generates 1.04 mW power output (into 190 Ω load) when it is vibrated at 75 Hz with vibration amplitude of 220 μm.