2, University of Delaware, Newark, Delaware, United States
3, University of Florida, Gainsville, Florida, United States
Given that organ function is regulated by neurological signals, various diseases can potentially be treated via bioelectronic devices that modulate these signals. However, state-of-the-art micro-cuffs based on rigid pad, wire, and pin electrodes do not yet provide fiber type selectivity or precision below the length scale of the electrode, which is a major limitation for achieving targeted stimulation of peripheral nerves that innervate critical organs. Thus, a technique for intrafascicular, molecular-guided formation of fiber type-selective polymer electrodes could potentially enable novel bioelectronic therapies for organ health. Here, we describe the in situ deposition of conjugated polymers for direct, local interfacing with peripheral nerves from custom designed electrodes created by 3D printing. In vitro experiments using hydrogel nerve mimics and explanted peripheral nerve tissue showed that polythiophene-based polymer electrodes could be polymerized in situ by application of cuff voltages above the polymerization threshold of the monomer species. In vivo studies showed precise control of the deposition by changing the size, shape, and location of the working and counter electrodes. 3D printing was leveraged to create micro-cuffs with programmable symmetric and asymmetric pad and wire electrode configurations to explore the potential for omni-directional guidance of the in situ deposited polymer, as well as to customize the mechanical and anatomical matching of printed cuffs and small diameter nerves. The experimentally observed conjugated polymer electrode polymerization trajectories showed agreement with finite element simulations of electric field and current density distributions in the 3D printed micro-cuffs. This work shows the potential to achieve fiber type-selective electrodes for peripheral nerve stimulation via directed in situ polymerization of conducting polymers.