Electrochemiluminescence (ECL)-Based Electrochemical Imaging Using a Massive Array of Bipolar Ultramicroelectrodes

In this report, we describe the fabrication, characterization, and use of a massive array of closed bipolar ultramicroelectrodes (UMEs) in electrochemical imaging applications. The bipolar UME array is 1 cm2 in size and contains >146 000 carbon electrodes embedded in a 15 μm thick insulating and freestanding membrane of Parylene C. Structural characterization with optical and electron microscopies shows that the carbon UMEs are highly uniform in size, shape, and interelectrode spacing. The bipolar UME array was used in electrochemical imaging to probe highly dynamic redox processes in which the reduction of redox molecules on one side the array is electrically coupled to an oxidative electrochemilumescence (ECL) process on the opposite side. This allows one to simultaneously monitor electrochemical reactions on hundreds of thousands of individual electrodes with millisecond temporal resolution. Our results suggest that microfabricated closed bipolar UME arrays can be useful for imaging fast and transient electrochemical processes in which scanning probe methods are inapplicable due to their limited temporal resolution.