Seeing in the dark could take on a whole new meaning. Scientists at the University of Michigan have created the first infrared light detector that is thin enough to be integrated with contact lenses. It's made from graphene.
Graphene is a thin sheet of carbon atoms. Considered the world's strongest material, it can sense the entire infrared spectrum, as well as visible and ultraviolet light. Researchers believe the material can someday give people super-human vision.
"We can make the entire design super-thin," Zhaohui Zhong, assistant professor of electrical and computer engineering, said in a press release. "It can be stacked on a contact lens or integrated with a cell phone."
But graphene has its limits. The super strong material can only absorb about 2.3 percent of the light that hits it. And it can't capture enough light to create an electrical signal, which is required to be an effective sensor.
Faced with this challenge, Zhong and colleague Ted Norris, professor of electrical engineering and computer science, worked with a team of graduate students to design a new way of generating and measuring electrical signals.
They did it by shifting their attention away from measuring electrons that are freed when light hits graphene to how to amplify the signal. The researchers looked at how nearby currents are affected by the electrical charges in light-induced graphene.
The device they created is smaller than a pinky nail, and has an insulating layer sandwiched between two sheets of graphene. Electrons are freed when light hits the top layer of graphene, which then creates positively charged holes. The electrons slip through middle barrier into the bottom layer of graphene, where a current runs through.
Positively charged holes left behind create an electric field that affects the flow of electricity going through the bottom layer. The process creates a way for the researchers to measure the change in electric current, which makes it possible to deduce the brightness of the light hitting the graphene.
One of the challenges of infrared detectors is that it gets hot. The researchers say their infrared detector doesn't require bulky cooling systems, like other detectors on the market. Making a room-temperature light detector opens new doors for such devices.
"If we integrate it with a contact lens or other wearable electronics, it expands your vision," Zhong said. "It provides you another way of interacting with your environment."
The scientists have not yet created a contact lens prototype, but believe their discovery will likely have military and scientific uses. Their findings were published in the journal Nature Nanotechnology.