A contact lens with embedded sensor for monitoring tear glucose level

We report the design, construction, and testing of a contact lens with an integrated amperometric glucose sensor, proposing the possibility of in situ human health monitoring simply by wearing a contact lens. The glucose sensor was constructed by creating microstructures on a polymer substrate, which was subsequently shaped into a contact lens. Titania sol–gel film was applied to immobilize glucose oxidase, and Nafion® was used to decrease several potential interferences (ascorbic acid, lactate, and urea) present in the tear film. The sensor exhibits a fast response (20 s), a high sensitivity (240 μA cm−2 mM−1) and a good reproducibility after testing a number of sensors. It shows good linearity for the typical range of glucose concentrations in the tear film (0.1–0.6 mM), and acceptable accuracy in the presence of interfering agents. The sensor can attain a minimum detection of less than 0.01 mM glucose.