Fabrication Process for Ultra-Reliable Polyimide-Based Neural-Interface Technology

Although polyimide can be used to produce high-channel-count neural interfaces with microelectrodes, their chronic reliability as an implant is a concern. In this paper we compared two different surface-treatment methods (O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> plasma and KOH/HCl soaks) to increase the strength and reliability of a bond formed between two fully cured layers of polyimide. Peel tests were used to quantify adhesion strength and were performed after test samples were soaked in RAA for days. The surface treatment based on O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> plasma formed a relatively strong bond (280 N/m) that was rapidly compromised by a 7-day RAA soak test. The bond formed by the surface treatment based on KOH and HCl soaks was far stronger (~500 N/m) and was not compromised by even a 15-day RAA soak test.