| The rehabilitation of spinal cord injuries may one day be achieved by sending current pulses deep into the spinal cord, a research practice known as intraspinal microstimulation. A new electrode system that provides a three-dimensional distribution of stimulation sites within the spinal cord could provide a valuable tool for implementing intraspinal microstimulation. The goal of this dissertation was to design such an electrode array, refine the microfabrication processes required for building the electrodes, and test them both in saline and in animal experiments. The process variables underlying cylindrical microfabrication were explored in order to improve the process consistency and yields. Processes such as material deposition and removal, lithography, and connecting to cylinders were characterized. Using the improved cylindrical microfabrication techniques, cylindrical multielectrodes were constructed. Benchtop testing probed the mechanical and electrical properties of the electrodes. During in vivo testing, the electrodes were inserted in the spinal cord with little tissue dimpling and maintained their straight shape. Recruitment curves were collected over a wide range of stimulus parameters and, for a given charge, produced higher forces for higher current levels. Stimuli were delivered through two stimulation sites during overlap testing to provide a measure of overlap between the sites. These overlap measurements were then converted to current-distance constants. The recruitment curves and current-distance constants were utilized to update the specifications for an intraspinal microstimulation electrode array. |
