Graphene lets your contact lens see infrared images

It sounds like it was from a spy-thriller thriller. You just have to wear a contact lens to see the infrared image. Researchers at the University of Michigan have turned the glasses in the movie into reality. They use graphene to create fingernail-size infrared image sensors that do not require bulky cooling devices. Due to its small size and light weight, it can be integrated into contact lenses or mobile phones, and has a wide range of applications in military, security and medical fields.

The research report was published in Nature Nanotechnology. The wavelength of infrared rays is between 760 nm and 1 mm. It is a non-visible light with a wavelength longer than that of red light, and is classified into three types: near-infrared ray, medium-infrared ray, and far-infrared ray. Mid-infrared and far-infrared sensors usually must operate at extremely low temperatures. Zhaohui Zhong, assistant professor of electrical engineering and computer science at the University of Michigan, and his team improved the process of generating electrical signals from graphene. An insulating barrier layer was placed between the two graphene sheets, and the bottom layer had an electric current passing through it. .

When light hits the top graphene, the device releases electrons, creating positively charged holes. Then, under the quantum tunneling effect, the electrons pass through the intermediate insulating layer and reach the bottom graphene layer. At this time, the positively charged holes left on the upper graphene will generate an electric field and affect the current of the lower graphene. By measuring the change in current, the brightness of the light shining on the upper graphene can be inferred. Zhonghui Zhao said that the new method has brought the sensitivity of the mid-infrared and far-infrared sensors to a new level for the first time, and it is completely comparable to traditional infrared sensors that require a cooling device to operate.