RF Coupling of Interdigitated Electrode Array on Aerogels for in vivo Nerve Guidance Applications

Abstract

Aerogels are light-weight porous materials that can tolerate the processing steps required for designing and creating an electric circuit such that the aerogel can be utilized as a substrate for device fabrication. Previous studies have shown the biostability and biocompatibility of polyurea crosslinked silica aerogels both in vivo and in vitro and have demonstrated the potential use of aerogels in biomedical applications. In vitro studies have shown that in the presence of an applied electric field neurites regeneration rate was greater on crosslinked silica aerogels than on tissue culture petridish used as a positive control. Currently, epineural suturing and nerve grafting are the gold standards for surgical reconstruction of injured nerves. However, because they rely on passive mechanisms for reapproximating the distal and proximal terminals they often lead to partial or no recovery leaving room for improvement. The present study investigates the feasibility of a wireless aerogel–based electrically-stimulating implant intended for nerve repair applications. Here the authors report on RF coupling between a secondary coil and a primary coil to wirelessly energize an interdigitated electrode array consisting of eleven interlocking fingers, created on a silica aerogel substrate. The coupling strength was tested both in air and in an animal model, as a function of distance and will be reported. This study focuses on in vivo evaluation and feasibility assessment of a novel active 3-D aerogel-based peripheral nerve repair device. The device utilizes induced EMF to establish a current (hence electrical stimulation) in predetermined pathways where nerve stumps will be confined to. Fundamental differences between in vitro and in vivo models necessitate the in vivo approach. The novel inductively-powered electrical stimulation aerogel-based device utilizes previously established 3-D confinement method for immobilization of nerve stumps, taking advantage of the mesoscopic surface roughness, unique to aerogels. The technique is tested on a mechanically strong, lightweight, porous, and biostable aerogel. Lithographic techniques, gold (Au) thin film metallization, and Faraday induction is used for circuit design, development, and activation.