Scientists have developed the first room-temperature light detector that can sense the full infrared spectrum and has the potential to put heat vision technology into a contact lens. Such a device has been developed by the engineering researchers of the University of Michigan.
"We can make the entire design super-thin. It can be stacked on a contact lens or integrated with a cell phone," said Zhaohui Zhong, electrical engineering professor.
Infrared light stretches to wavelengths up to a millimetre long. Infrared vision may be best known for spotting people and animals in the dark and heat leaks in houses, but it can also help doctors monitor blood flow, identify chemicals in the environment.
‘Graphene’- a single layer of carbon atoms, could sense the whole infrared spectrum - plus visible and ultraviolet light. But until now, it hasn't been viable for infrared detection because it can't capture enough light to generate a detectable electrical signal.
With one-atom thickness, it only absorbs about 2.3 per cent of the light that hits it. If the light can't produce an electrical signal, graphene can't be used as a sensor. To overcome that hurdle, Zhong and Ted Norris designed a new way of generating the electrical signal. Rather than trying to directly measure the electrons that are freed when light hits the graphene, they amplified the signal by looking instead at how the light-induced electrical charges in the graphene affect a nearby current. The new approach allowed the sensitivity of a room-temperature graphene device to compete with that of cooled mid-infrared detectors for the first time.
"If we integrate it with a contact lens or other wearable electronics, it expands your vision. It provides you another way of interacting with your environment," concluded Zhong.