NEW YORK: What about wearing a contact lens that can let you see things in the dark? A smart contact lens is in the offing that could give its wearer infra-red 'night vision'.

According to researchers from University of Michigan, by placing graphene inside the lens, they can build a sensor capable of capturing infrared light.

A prototype is already here. Smaller than a fingernail, it could one day be built into lenses for soldiers and others who need to see in the dark.

“The layered approach can lead to ultra-thin sensors. We can make the entire design super-thin,” explained Zhaohui Zhong, an assistant professor of electrical and computer engineering at University of Michigan.

Graphene is a promising candidate material for ultra-broadband photodetectors as its absorption spectrum covers the entire ultraviolet to far-infrared range,” he added.

Graphene is made of a single layer of carbon atoms that are bonded together in a repeating pattern of hexagons.

It is one million times thinner than paper.

The sensor can be stacked on a contact lens or integrated with a cell phone.

The material shows a very strong effect when it’s struck by photons (light energy).

“Here, we report an ultra-broadband photo-detector design based on a graphene double-layer heterostructure,” Zhong said.

The detector is a photo-transistor consisting of a pair of stacked graphene monolayers separated by a thin tunnel barrier.

Under optical illumination, photo-excited hot carriers generated in the top layer tunnel into the bottom layer, leading to a charge build-up on the gate and a strong photogating effect on the channel conductance, he noted.

The devices demonstrated room-temperature photo-detection from the visible to the mid-infrared range, said the study published in the journal Nature.

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