Spatiotemporal electrochemistry on flexible microelectrode arrays: Progress towards smart contact lens integration

We demonstrate a real-speed spatiotemporal electrochemical map showing both time-and position-varying concentration of an analyte in contact with a flexible microelectrode array. A polymer-based device of 11 mu m in thickness comprising patterned gold metallisation on a polyimide substrate was fabricated, with eight individually addressable working electrodes (diameter 30 mu m) and an integrated counter electrode. We performed a repeated sequence of high-speed chronoamperometric measurements at each electrode and processed the data to generate a spatiotemporal concentration map, in which a number of fluid effects, including bulk flow, diffusive mixing and homogenisation of two miscible fluids of different concentration were observed. This device was fabricated using processes compatible with an existing smart contact lens platform, with a view to develop integrated sensors in future work. We believe this technique has significant potential in the field of electrochemical smart contact lenses, both in introducing new functionality and in improving our ability to draw accurate and clinically-relevant conclusions from measurements made in the tear film.