A microfabricated coil for implantable applications of magnetic spinal cord stimulation

In this paper, a microfabricated inductive coil comprising of 125-turn coil windings and a MnZn-based magnetic core in a volume of 200 mm³ is presented for the magnetic neural stimulation in a spinal cord. The coil winding with the parallel-linkage design instead of the typical serial-linkage one is proposed not only to provide better design flexibility to the current mode driving circuit but also to simplify the fabrication process of the 3-D inductive coil, which can further advance the coil miniaturization. Experimental results show the microcoil with a 1.5 A, 1 kHz square-wave current input can induce a voltages of ~220 μV on the conducting wire with an impedance of ~0.2 Ω @ 1 kHz, 1 mm separation.