Development of a single-sided Parylene C based intrafascicular multichannel electrode for peripheral nerves

As cleanroom fabricated polyimide based electrodes are commonly used in clinical trials due to their small dimensions and high flexibility we want to translate these advantages to a maskless manufacturing technology and another substrate material with FDA approval: Parlyene C. Using a picosecond laser (355 nm Nd:YVO₄) an established laser fabrication process (1064 nm Nd:YAG nansecond laser) for silicone rubber electrodes was modified to allow the fabrication of thin parylene C electrodes for intrafascicular application. The process utilizes a 25 μm thick platinum iridium foil that is placed between two 10 μm thick parylene C substrate layers. Using the laser for thinning down the metal, increasing the active surface and cutting the complete electrode array a new fabrication process is developed. Adhesion parameters of the involved materials are measured and tailored to fit each other. The single electrode arrays feature 4 intrafascicular contacts as well as a ground electrode and fixation openings outside the nerve. Functionality of the electrode array was measured and a first assessment of its usability has been performed. The mechanical and electrochemical parameters are promising for intrafascicular implantation, successful stimulation and recording application in a peripheral nerve.