UC San Diego

Current spinal cord neural interfaces rely on bulky, low-channel count paddle arrays to interface with the spinal cord or resort to probing neural function at peripheral sites, such as the scalp or limbs, rather than interfacing with the spinal cord directly. In recent years, there has been growing interest to develop flexible, high-channel count microelectrode arrays for sophisticated neural interfaces. These arrays provide better contact to neural tissue and reduce the body’s immune response due to their high conformality and offer more choice in stimulation and recording location thanks to their high channel count. However, few studies have directly evaluated the benefits of these flexible, high-channel count microelectrode arrays compared to existing technologies in clinic. The studies that have examined this relationship have primarily involved cortical electrodes, such as those used for speech decoding. In this dissertation, I study the benefits of using flexible, high-channel count microelectrode arrays for spinal cord neural interfaces and provide evidence to support their further widespread adoption.In Chapter 1, I introduce a conformal, high-channel count microelectrode array for intraoperative neuromonitoring during spinal cord surgery. I show that this array can map spinal cord function at unprecedented spatial resolution, improving precision and reactivity to potential spinal cord damage. In Chapter 2, I introduce a conformal, high-channel count microelectrode array for epidural electrical stimulation of the rat spinal cord for treatment of spinal cord injury. I demonstrate that this electrode delivers highly focal stimulation, increasing its effectiveness in selectively recruiting muscles. Thus, Chapters 1 and 2 emphasize the importance of achieving submillimeter resolution in spinal cord mapping and stimulation. In Chapter 3, I address the need for durable and conductive materials for chronic neural interfaces by developing and characterizing a novel, more stable electrode coating material. I translate the use of this material from bulk film to microelectrodes and demonstrate its improved stability in benchtop and in vivo experiments. Together, the novel technologies established in this dissertation are important steps to drive the integration flexible, high-channel count microelectrode arrays in the clinic for spinal cord applications.