In vitro Assessment of Long-Term Reliability of Low-Cost μECoG Arrays

Micro-electrocorticographic (mu ECoG) electrode arrays provide a minimally invasive, high-resolution neural interface with broad cortical coverage. Previously, we fabricated mu ECoG arrays at a lower cost than commercially available devices using low-cost industrial processes [1], [2]. Here, we report the in vitro electrical performance of five mu ECoG designs undergoing an accelerated aging protocol. The impedance and yield of the mu ECoG arrays were tracked over time. The equivalent lifetime at 37(omicron)C depended on the manufacturer and material stack-up, and ranged between 30 and greater than 760 days (ongoing). The main failure modes of these devices were delamination at the site of the electrode contact and broken traces due to metal dissolution. Based on these in vitro results, we offer several recommendations for mu ECoG designs suitable for chronic implantation.