Microneedle Penetrating Array with Axon-Sized Dimensions for Cuff-less Peripheral Nerve Interfacing

Autonomic nerves are typically only hundreds of microns in diameter near their organ targets and these carry all of the sympathetic and parasympathetic control signals. We present a cuff-less microneedle array specifically designed to potentially map small autonomic nerves. The focus of this paper is the design and fabrication of an ultra-miniaturized silicon needle array on a silicone substrate. We demonstrate arrays having 25 to 100 microneedles. Each needle has a 1-micron tip and dual-taper shaft. We demonstrate an ability to control the tip shape, angle, and shaft angle which is important for balancing sharpness and stiffness. These high-density arrays also include a special backside anchor embedded in silicone for stability in the elastic substrate, yet the array freely wraps over a 300-µm nerve. Another critical method presented here is a surgical technique for inserting and securing an array without a cuff (as small as 0.3 mm wide and 1.2 mm long) by photochemical bonding of collagen/Rose Bengal adhesive agents to epineurium. Future work will focus on device functionalization and histological characterization in a rat vagus model.