The transistor's nanostructure. (Credit: Oregon State University)

A transparent sensor on a contact lens could enable Type 1 diabetes patients to monitor their blood glucose levels and even control their insulin infusions. The sensor uses a nanostructured transistor — specifically an amorphous indium gallium oxide field effect transistor, or IGZO FET — that can detect subtle glucose changes in physiological buffer solutions, such as the tear fluid in eyes.

Researchers say the sensors they fabricated using the IGZO FET will be able to transmit real-time glucose information to a wearable pump that delivers the hormones needed to regulate blood sugar: insulin and glucagon. The sensor and pump would, in effect, act as an artificial pancreas.

The FET’s closely packed, hexagonal, nanostructured network resulted from complimentary patterning techniques that have the potential for low-cost fabrication. Those techniques include colloidal nanolithography and electrohydrodynamic printing. Because the sensor is transparent, it doesn’t obstruct vision, making more space available for sensing on the contact lens. The transparent FET sensors might ultimately be used for cancer detection, by sensing characteristic biomarkers of cancer risk. Their high sensitivity could also measure things such as pulse rate, oxygen levels, and other aspects of health monitoring that require precise control.