Night vision contact lenses can sense ‘invisible’ wavelengths

Heat or thermal vision, one variety of night vision, illuminates the heat being itted by animals, humans, cars, electronic devices and more.
The researchers have built the first room-tperature light detector that can sense the full infrared spectrum. Infrared light starts at wavelengths just longer than those of visible red light and stretches to wavelengths up to a millimeter long. Infrared vision is perhaps the best known variety of night vision. It can also help visualise heat leaks in houses, help doctors monitor blood flow, identify chicals in the environment and allow art historians to see Paul Gauguin’s sketches under layers of paint.
Unlike comparable mid- and far-infrared detectors currently on the market, the new detector doesn’t need bulky cooling equipment to work. To make the device, the researchers put an insulating barrier layer between two graphene sheets. The bottom layer had a current running through it. When light hit the top layer, it freed electrons, creating “holes” – gaps between electrons that act as positive charges. Then, the electrons used a quantum mechanical trick to slip through the barrier and into the bottom layer of graphe.
The positively charged holes, left behind in the top layer, produced an electric field that affected the flow of electricity through the bottom layer. By measuring the change in current, the team could deduce the brightness of the light hitting the graphene. The new approach allowed the sensitivity of a room-tperature graphene device to compete with that of cooled mid-infrared detectors for the first time. The device is already smaller than a pinky nail and is easily scaled down.
According to the researchers: “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”.
The research has been published in Nature Nanotechnology.

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