Fundamental Properties of Micromagnetics for Peripheral and Central Nervous System Stimulation

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Recent neuroengineering research has demonstrated that motor function and sensing in patients that are affected by neurodegenerative diseases can be partially restored by means of electrical neurostimulation. However, electrode arrays currently used to replace endogenous electrical activation present several drawbacks, including exposure of metal contacts to conductive tissue, potential need for excessive charge density to achieve stimulation when electrode size is small, and lack of tolerance with respect to imperfect contact between the electrode contacts and the neural tissue.The PIs have recently demonstrated that a new class of microcoils can effectively stimulate the peripheral nervous system, leading to the idea that magnetic microstimulators for implantable devices and neuroprostheses can be devised. Since the mechanisms of magnetic stimulation are centered on eddy currents and their gradients, coils do not need direct contact with the tissue and therefore they can be completely insulated, thus avoiding the possibility of material reactions with conductive neural or surrounding tissues. Further, arrays of coils can potentially offer more options to control the shape of the induced magnetic fields, and therefore eddy currents, and their operation is not affected by contact capacitance. Intellectual Merit: The goals of the proposed work capitalize on our theoretical and experimental findings that contact magnetic stimulation of the nervous system is feasible, and investigate new classes of microcoils and magnetic stimulators that will be particularly suited for micromagnetic stimulation. Specifically, a major goal is to investigate coil geometries that allow control of the microcoil?s magnetic fields; this will increase the magnetic flux density levels well beyond those of traditional coils and alter the orientation of the fields in the proximity of the target neurons. Ferrite-backed microcoil arrays have the potential to provide increased field strength, sharp gradients, and control of the magnetic field needed for selective neurostimulation. In this work, the PIs investigate novel devices that could provide a paradigm shift compared to traditional electrical neurostimulators. Broader Impacts: This work has the potential to offer a highly innovative solution to peripheral and central system neurostimulation devices. Providing an alternative solution to surface or penetrating electrodes could positively impact a number of implantable systems, which currently suffer from the significant drawbacks of electrical neural stimulation. Besides the important clinical impact, the proposed program offers unique opportunities to train engineering students in a highly interdisciplinary activity at the forefront of engineering technology and medical research. In addition to utilizing the proposed research activity in various existing programs designed to have a lasting impact on current and prospective undergraduate students, the proposed project will increase the interest of engineering students in the emerging field of neuroprosthetics and demonstrate the benefits of engineering to medicine. The PIs will provide additional learning opportunities targeted at K-12, 2-year, and 4-year feeder schools and colleges through outreach programs.