Spatiotemporal Electrochemical Sensing in a Smart Contact Lens

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.