Fabrication and testing of a large area, high density, parylene MEMS µECoG array

We report the design, microfabrication and testing of a flexible 256-electrode array for micro-electrocorticography (μECoG) with an electrode pitch of 500 μm. Our μECoG grid is a flexible five-layer parylene MEMS device (two layers of platinum insulated by three layers of parylene) featuring plasma-etched vias and a monolithically integrated parylene cable which is compression-bonded to a fan-out board using anisotropic conductive film (ACF) technology. We have characterized the device by electrochemical impedance spectroscopy in artificial cerebrospinal fluid (aCSF) and recorded acoustic evoked potentials in vivo from the rat primary auditory cortex.