New technology developed by researchers at the University of Michigan could give users infrared or UV vision through specialized contact lenses made from graphene. In addition to numerous other nigh-miraculous characteristics, graphene also provides a very strong effect when it is struck by photons (a.k.a. light energy). The material absorbs the energy and becomes a “hot carrier” capable of measuring, processing, and turning that energy into an image—across the whole infrared spectrum, as well as visible and ultraviolet light.
Because graphene is only one atom thick, it is a perfect material for unobtrusive wearable optic devices, such as contact lenses. However, it’s thinness only allows it to absorb 2.3 percent of the light that hits it, not enough to generate an electronic signal, and therefore making incapable of operating as a sensor on its own.
Zhaohui Zhong and other University of Michigan researchers have devised a solution: using a single layer of graphene as the primary photodetector, they add an insulating dielectric layer beneath it, with another layer of graphene beneath that. As light hits the topmost layer, electrons are freed up, creating “positively charged holes,” and allowing electrons to slip through. This creates an electrical field that affects the flow of current through the bottom layer. By measuring the change in current in the bottom layer, the brightness of the light can then be deduced.
“The challenge of the current generation of graphene-based detectors is that their sensitivity is typically very poor,” Zhong said in a press release. “It’s a hundred to a thousand times lower than what a normal commercial device would require. […] Our work pioneered a new way to detect light. We envision that people will be able to adopt this same mechanism in other material and device platforms.”
Zhong and company’s device is essentially a phototransistor, with around the same sensitivity as CMSO silicon imaging sensors in everyday digital cameras. And, while most imaging technologies capable of seeing in the UV and IR spectrums require bulky cooling systems, the graphene phototransistor is so sensitive that it can operate at room temperature.
In its current design, the device is roughly the size of a pinky nail—ideal for contact lenses—and could easily be scaled down even further. “If we integrate it with a contact lens or other wearable electronics, it expands our vision,” Zhong’s said. “It provides you another way of interacting with your environment.”
• “Graphene Contact Lenses Could Give You ‘Predator’ Vision” http://www.mnn.com/green-tech/research-innovations/stories/graphene-contact-lenses-could-give-you-predator-vision
• “Graphene Gives You Infrared Vision In A Contact Lens” http://spectrum.ieee.org/nanoclast/semiconductors/optoelectronics/graphene-gives-you-infrared-vision-in-a-contact-lens
• “Graphene Smart Contact Lenses Could Give You Thermal Infrared and UV Vision” http://www.extremetech.com/extreme/178593-graphene-smart-contact-lenses-could-give-you-thermal-infrared-and-uv-vision