Perforated 2×2 Parylene sheath electrode array for chronic intracortical recording

We present the development of a perforated 2×2 Parylene sheath electrode array (PSEA). Parylene C is surface micromachined to create conical sheath structures with electrode sites on the interior and exterior. Individual probes can be configured into a 2×2 array. Building upon previous designs, the sheath geometry was redesigned to have sharper taper and incorporate perforations in order to minimize insertion trauma and facilitate cell-cell signaling, respectively, with the aim of improving long-term recording reliability. Bioactive coatings were applied to the PSEA to encourage dendritic growth and control the immune response. Benchtop electrochemical results confirmed that electrode sites possess appropriate impedance values for neural recording. A custom-made insertion shuttle was fashioned to deliver the PSEA to the target location in the cortical tissue and then retract, leaving only the flexible PSEA in the tissue. This system successfully implanted multiple PSEAs into the rat M1 motor cortex and a 6 month in vivo study is currently underway.