Inter-layer coatings for softening polymer-based neural interfaces

This paper reports the successful fabrication of softening polymer (SP)-based devices with inter-layer coatings for neural interface applications. SPs are flexible biocompatible polymers that soften upon implantation into the body, thus capable of reducing mechanical stress on the surrounding tissue and increasing the conformability of the implant. The softening process relies on water uptake into the polymer that can affect its electrical insulation capabilities. Employing an amorphous silicon carbide (a-SiC) thin film inter-layer between the metal traces and the SP is expected to provide a reliable water-barrier while allowing the SP plasticization once the device is implanted. We report the electrochemical properties and leakage current characteristics of various structures with a-SiC and polyimide inter-layer coatings under simulated physiological conditions. The fabricated structures demonstrated appropriate electrical properties and were found to be reliable up to a 2.5 mm radius of curvature when bending in compression.