An electrochemical smart contact lens (ESCL) capable of real-speed spatiotemporal electrochemical sensing across the surface of the eye is demonstrated. Four microelectrode arrays, each comprising 33 gold microdiscs of 30 µm diameter, and a distributed common gold counter electrode, are integrated into a soft smart contact lens platform based on polyimide and thermoplastic polyurethane. Using a novel fast-switching chronoamperometric method, an electrochemical 'video' of concentration variation in a model eye under flow conditions is produced, in which the introduction, progress, mixing and drainage of fluid of varying concentration can be observed. The device builds on previous work towards a platform suitable for clinical use and has proven to be robust under expected use conditions, with sensing performance remaining unchanged after thermoforming and repeated mechanical deformation. This work represents a significant step forward in ESCL design, and constitutes significant progress towards a technology with real clinical utility.

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 μm in thickness comprising patterned gold metallisation on a polyimide substrate was fabricated, with eight individually addressable working electrodes (diameter 30 μm) 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.

Most advances in electronic contact lenses are aimed at active vision enhancement. Here, additional sensing and display functionalities are discussed. Integration of individually addressable microelectrodes (30 µm diameter) is demonstrated for biomarker detection in tear fluid, with a focus on future applications, challenges, and integration with display technology.

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