3D high aspect ratio, MEMS integrated micro-solenoids and Helmholtz micro-coils

High-aspect-ratio 3D geometrically perfect solenoidal micro-coils are fabricated for the first time in a fully MEMS-integrated technology. Vertical micro-coils with up to 15 windings and diameters down to 100 mum have been wound using an automatic wirebonder around SU8 and PMMA cylindrical posts. Using this method we also fabricate Helmholtz micro-coils capable to generate magnetic fields of 1 mT, according to simulations. We demonstrate the potential to use large arrays of solenoidal micro-coils for energy harvesting applications by placing them in a sinusoidal magnetic field. The induced voltage is 1.4 mV at 300 kHz for a 7 windings micro-coil, in agreement with theoretical calculations.