On the design of efficient magnetic coils for the stimulation of peripheral nerves

Neural stimulators are the key building blocks of current neuroprosthetic systems, such as cochlear and retinal implants. Due to direct current injections and foreign body reactions, conventional current passing electrodes suffer from reduced performance and reduced lifetimes. However, magnetic fields can be used as an alternative technique to induce currents in neural tissues with the goal of stimulating the central and/or peripheral nervous systems (M. Yamaguchi et. al., JAP'89). Because the effectiveness of magnetic stimulation is directly related to the magnitude of the generated magnetic fields resulting from the current carried by a magnetic coil, the magnetic coil needs to be optimized to enhance the induced electric field at the stimulus site.