Formation of a porous alumina electrode as a low-cost CMOS neuronal interface

A low-cost electrode design has been devised for drug discovery pharmacology, neural interface systems, cell-based biosensors and electrophysiology research, based on high volume CMOS (complementary metal oxide semiconductor) integrated circuit technology. The electrode is formed by the anodisation of CMOS metallisation to form nanoporous alumina. The process was developed to address the concern of aluminium neurotoxicity, improve corrosion resistance under physiological conditions and to present a preferential morpohology for cell-substrate adhesion. Thin-film anodisation is optimised to overcome problems of thermal fusing, enabling a variety of substrate morphologies to be produced using potentials of 10-100V. Current density scaling factors are shown to confirm the suitability of CMOS circuit geometries to the anodisation process. Corrosion tests demonstrate improved corrosion performance of the porous alumina electrode. The process and scaling factors are validated by anodisation of a simple CMOS device.