Smart contact lenses could be used to monitor glucose levels in tears. Such noninvasive and real-time monitoring could improve care and prevent finger pricks for diabetics. However, smart contact lenses developed so far use opaque materials that can impede vision, and are built using hard substrates that can irritate the eye.
Franklin Bien, Jang-Ung Park, Ulsan National Institute of Science and Technology (UNIST), Republic of Korea, and colleagues have developed a flexible smart contact lens with improved transparency. The lenses feature a glucose sensor, wireless power transfer circuits, and an LED (light-emitting diode) display pixel. The electronic components are included on separate “islands”, embedded in a silicone elastomer. This arrangement allows the lens to be stretched and bent without putting strain on the electronic components. The team matched the refractive indices of the different components of the lens to provide unobstructed vision to the lens wearer.
The stretchable and transparent antenna for wireless power transfer was produced from silver nanoparticles using photolithography and a wet etching process. The glucose sensor is based on the enzyme glucose oxidase, which is immobilized on a graphene surface using a pyrene linker. When this enzyme oxidizes glucose, the products of the reaction cause the resistance of the sensor to change. This change can be measured. An integrated LED pixel is bonded to the circuit using a silver epoxy glue. This LED turns off once the lens detects high glucose levels to alert the user.
- Soft, smart contact lenses with integrations of wireless circuits, glucose sensors, and displays,
Jihun Park, Joohee Kim, So-Yun Kim, Woon Hyung Cheong, Jiuk Jang, Young-Geun Park, Kyungmin Na, Yun-Tae Kim, Jun Hyuk Heo, Chang Young Lee, Jung Heon Lee, Franklin Bien, Jang-Ung Park,
Sci. Adv. 2018, 4, eaap9841.