NanoDay 2020 Poster 12 – Carson Allen

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Predicting Axon Recruitment for Different Microelectrode Geometries

Carson Allen (LinkedIn)

Authors: Carson Allen, Jack Judy, Erin Patrick

Faculty Mentor: Jack Judy, PhD

College: College of Engineering

Department: Electrical and Computer Engineering

Abstract

For decades neural interfaces have been used to communicate with the central and peripheral nervous systems for many clinical applications. When developing neural interfaces for next-generation prostheses for amputees, the use of implantable electrode arrays used in peripheral nerves have gained attention. Several intra-fascicular designs have been developed (i.e., the Utah Slanted Electrode Array, Longitudinal Intra-Fascicular, and Transverse Intra-fascicular Electrode). Although all these designs have potential in being able to help those with missing limb regain lost sensory and motor function, there is still a huge gap to achieve fine motor control and proper sensory feedback due to the lack of precision in stimulation and recording. In this study we use a detailed COMSOL model that uses literature-derived material properties for nerve tissue compartments to calculate electric potential gradients caused by current driven microelectrodes on narrow polyimide strip. We then use a NEURON-Python simulation to determine electrical current thresholds for activating fibers nearby the implanted electrode. We analyze every fiber within a fascicle for a set of node of Ranvier positions to better understand how stimulation current, fiber diameter, electrode-fiber separation, and electrode diameter impact fiber activation. By running these simulations for various electrode diameters (8 – 64 µm), fiber diameters (2 – 16 µm), and nodal displacements ranging from zero to half the nodal spacing, we determined trends for how these factors influence which fibers become activated.

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