Characterization and connectorization of optoelectronic neural probes

Abstract

Reliability of interfaces between the nervous system and the neuroprosthetics can be significantly improved through the use of flexible polymer and polymer composite neural stimulation and recording systems. Furthermore, recent advances in optical neural stimulation methods would benefit from seamless integration of optical waveguides into neural probes. In this thesis, we describe electronic and optical characterization of polymer-based probes produced through thermal drawing process. Our results indicate that polymer-based fiber-probes maintain low-loss optical transmission even in the presence of 90-270* bending deformation with radii of curvature as low as 500 pim over multiple deformation cycles. These probes were robust enough to chronically function in the brain of freely moving mice. Furthermore, these flexible devices enabled direct optical stimulation in the spinal cord, which for the first time allowed for direct spinal optical control of lower limb muscles. In addition to optical characterization, we have developed a method for high-throughput connectorization of the fiber-probes with microscale features to external electronics. This required the development of custom printed circuit boards and involved a multi-step lithographic process. Finally, in a three-months long study we have demonstrated that probes characterized in this thesis yield significantly reduced tissue response in the brain as compared to the steel microwires traditionally used by neuroscientists.