Abstract
The ability to deliver highly compliant biosensors through the toughest membranes of the central and peripheral nervous system is an important challenge in neuroscience and neural engineering. Bioelectronic devices implanted through dura mater and thick epineurium would ideally create minimal compression and acute damage as they reach the neurons of interest. We demonstrate that a novel diamond shuttle can deliver ultra-compliant polymer microelectrodes to intraneural structures with the smallest cross-sectional area and dimpling reported to date. This was demonstrated in vivo through rat dura mater and feline dura and dorsal root epineurium. The dorsal root ganglia are an especially relevant target for organ function and pain research, and unlike dura mater over the brain, its outer membrane cannot be removed surgically. We present a method of creating a unique diamond shuttle, only 11 microns thick with a T-beam vertical support, that pierces dura and epineurium. This T-beam structure reduced the cross-sectional area of the shuttle by 58% relative to an equivalently stiff silicon shuttle. We also discovered that higher frequency oscillation of the shuttle, at 200 Hz, significantly reduced tissue compression regardless of the insertion speed, while slow speeds independently also reduced tissue compression. Finally, we demonstrate the shuttle delivery of and neural recordings from ultra-fine, flexible arrays (5-μm thick, 65-μm wide) with 60 microelectrodes in a 1.2-mm span from different neural targets. This novel microelectrode shuttle has a large design space making it suitable for research in a variety of central and peripheral nervous system targets and animal models.
