It almost sounds like science fiction, but Sergey Shleev of Malmö University in Sweden and colleagues are developing a miniature bio-based fuel cell that can power a glucose sensor embedded into a contact lens. The biodevice with its three-dimensional nanostructured gold electrodes contains an organic complex (tetrathiafulvalene-tetracyanoquinodimethane conducting complex) and a redox enzyme (Myrothecium verrucaria bilirubin oxidase). Ascorbate and oxygen naturally present in tears act as fuel and oxidant for the device, which then drives a glucose sensor that keeps an eye on the patient’s health.

The tiny size of the electronics means the user’s vision is not impaired and presumably even patients with 20:20 vision could wear one optically “inactive” lens to monitor their blood glucose during the day. The system would preclude the need for regular pin-prick blood tests, which people with diabetes must carry out regularly to ensure they take insulin when their body needs it.

• Miniature Biofuel Cell as a Potential Power Source for Glucose-Sensing Contact Lenses
  Magnus Falk, Viktor Andoralov, Maria Silow, Miguel D. Toscano, Sergey Shleev
  Analytic. Chem. 2013.
  DOI: 10.1021/ac4006793