Transparent Micro-electrocorticography (μECoG) Arrays for Optogenetic Mapping of Surface Potentials

Electrocorticography (ECoG) has been used for decades clinically to help localize epileptic seizures but has only recently come into vogue as a potentially useful imaging modality. This change has partially been driven by the development of new micro-electrocorticography (µECoG) arrays which take advantage of modern surface micromachining techniques to achieve extremely dense electrode arrays packed with tiny (less than500µm diameter) electrodes. As an imaging tool, µECoG may be improved by taking advantage of the transparent µECoG array technology developed at the University of California, Berkeley, where the electrodes are manufactured out of a transparent conductive film of indium-tin-oxide (ITO). This work presents in detail the design, fabrication and testing of the transparent µECoG arrays including verification of impedance, transparency, and electrical properties. These arrays have the smallest electrodes to date of any µECoG array, enabling higher spatial resolution than previous devices. This work also extends previous work by plating the ITO electrodes with the transparent conductive polymer PEDOT in order to improve electrochemical impedance properties and characterizing the results. Finally, applications for the transparent µECoG technology for optogenetics experiments are suggested and described.