Syringe-Injectable Mesh Electronics with Minimized Injection Footprint

Abstract

The advent of implantable neural probes has enabled significant contributions to fundamental scientific studies as well as clinical therapeutics for neurological diseases and disorders. While brain implants readily enable high spatiotemporal resolution for monitoring of single-unit neuronal activity, conventional technologies have been limited in their applications as a consequence of chronic inflammation. Prior efforts focused on the development of syringe-injectable mesh electronics have demonstrated a biocompatible neural interface that does not elicit chronic immune response. The work described here builds upon those seminal studies to address existing technological challenges that have limited the scope of possible applications. I will first introduce minimization of the mesh electronics injection footprint by significantly reducing the required delivery needle size and saline injection volume, which was accomplished by optimization of probe design for improved mechanical properties. Second, I will introduce a new paradigm for mesh electronics delivery that utilizes syringe injection but does not require fluid flow. Injection into mice using reduced diameter needles for low injection volume and for no injection volume mesh electronics was electrophysiologically and histologically investigated to assess how minimization of the injection footprint modulates temporal dynamics of the evolution of the probe-tissue interface. Third, I will report on mesh electronics injection directly between vertebrae in mice, which was previously inaccessible without reduced diameter needles. These studies demonstrated chronic stability of the mesh electronics in spinal cord tissue, correlated neuronal firing activity between the spinal cord and motor cortex in response to optogenetic stimulation, and stable evoked forelimb motion in response to electrical stimulation of spinal cord neurons by mesh electronics. Last, I will describe efforts on moving toward clinical applications through autoclave sterilization of an electrically prebonded mesh electronics input/output interface. Autoclave processing renders the prebonded mesh electronics sterile while introducing minimal to no impact on electrical recording capabilities with an appropriate interconnection and packaging approach. Together, these contributions highlight key advancements in mesh electronics delivery, applications for interfacing with the central nervous system, and progress toward near-future clinical translation.