Contact Lens Biofuel Cell Tested in Conditions Similar to Human Eyes

Researchers in recent years have begun developing “smart” contact lenses for biomedical applications or for wearable electronic displays. Most of these devices require an external power source, which can be cumbersome, especially to people with an active lifestyle. In this work, we describe a biofuel cell contact lens prototype, which could someday replace external power sources for contact lens devices. Our first-generation prototype consisted of buckypaper electrodes with a poly(methylene green)/NAD⁺/lactate dehydrogenase anode and a bilirubin oxidase cathode (Fig. 1). These electrodes were molded into a silicone elastomer contact lens, and the prototype was tested in synthetic tears, both in vitro and on a test stand that mimicked eye conditions. The open circuit voltage was 0.413 ± 0.06 V and the maximum current and power density were 61.3 ± 2.9 µA cm^-2 and 8.01 ± 1.4 µW cm^-2, respectively. A COMSOL model was created and subsequently used to determine better electrode size and arrangement. These model results guided the design and fabrication of a second-generation contact lens biofuel cell, which showed improved performance compared to the first-generation lens.

Fig. 1. Contact lens biofuel cell prototype. Modified buckypaper electrodes were integrated into a silicone elastomer lens. Connecting leads can be seen extending to the right.