The special forces carry out operations by infiltrating enemy lines on a moonless night. This is possible because night vision goggles convert infrared light into visible light, allowing visibility of enemy movements even at night. Chinese scientists have developed night vision goggles that fit into contact lenses. When the lenses are worn, one can see even with their eyes closed.
In particular, unlike night vision goggles, there is no need for a separate power source. Once commercialized, it is expected to be of great assistance not only to the military but also for nighttime rescue operations or emergency construction. The day when stories typical of spy movies become a reality is not far off.
◇Converting infrared light into visible light
The research team, led by Professor Tian Xue from the First Affiliated Hospital of University of Science and Technology of China, announced on the 23rd in the international journal "Cell" that they developed contact lenses that convert infrared light into visible light and confirmed that both humans and mice can detect infrared light.
The reason it is hard to see at night is that visible light, which humans can perceive, is scarce. Night vision goggles work by converting infrared light into visible light, allowing sight at night. The principle of the contact lenses is the same as that of night vision goggles.
The research team developed nanoparticles that absorb near-infrared light in the wavelength range of 800 to 1600 nm (nanometers, where 1 nm equals one billionth of a meter) and convert it to visible light in the range of 400 to 700 nm that mammals can see. Previously, in 2019, the research team confirmed that injecting these nanoparticles into the retinas of mice allowed them to see infrared light.
This time, a new method was developed to implement the capabilities of the nanoparticles without damaging the eyes. This involves embedding nanoparticles into contact lenses. The research team mixed the nanoparticles with a non-toxic polymer material known as hydrogel. Hydrogel has a mesh structure that allows light to pass through and is transparent. The nanoparticles adhere to this mesh structure.
Mice wearing the contact lenses were able to see infrared wavelengths. When given a choice between a dark box and a box illuminated with infrared light, the mice with contact lenses chose the dark box. It was because the infrared light, which the mice prefer in dark places, was visible to them. Other mice randomly selected boxes. The pupils of the mice wearing the contact lenses constricted when exposed to infrared light, and brain imaging analysis confirmed that the visual cortex was activated. This indicates that infrared light was visible to the mice.
◇Potential for correcting color vision deficiencies
Professor Xue said, "Our research opens up the possibility of providing vision that surpasses normal vision through wearable devices that do not cause harm to the human body." The newly developed contact lenses are not yet capable of seeing as clearly at night as night vision goggles do. However, the presence of infrared light can be sufficiently detected. In this respect, there are more practical applications than night vision goggles, such as detecting infrared distress signals sent by those in trouble or verifying codes or anti-counterfeiting information.
In fact, humans wearing contact lenses were confirmed to accurately detect infrared signals similar to Morse code and recognize the direction of infrared light. Professor Xue noted, "Participants in the experiment could see nothing without contact lenses, but when wearing the lenses, they could clearly see the flicker of infrared light." The research team explained, "In particular, when the eyes were closed, infrared information was observed better because near-infrared light penetrates eyelids better than visible light, resulting in less interference from visible light."
The nanoparticles used in the contact lenses can also distinguish infrared wavelengths. Short wavelengths of infrared light convert to blue-toned short-wavelength visible light, while long wavelengths of infrared light convert to red long-wavelength visible light. The nanoparticles converted 980 nm infrared light to blue light, 808 nm to green, and 1532 nm to red light. The research team stated, "Contact lenses allow clearer recognition of the infrared spectrum and simultaneously enable individuals with color vision deficiencies to see wavelengths that are usually undetectable to them."
However, before applying this to humans, it is necessary to verify whether there is a possibility that the nanoparticles may leak into the retina and whether the heat generated during the process of converting infrared light to visible light does not affect the eyes. Also, this research only detected infrared light emitted from light-emitting diodes (LEDs), not from natural environments. The research team indicated that they are working on enhancing the sensitivity of the nanoparticles to detect lower levels of infrared light emitted from natural environments.
References
Cell (2025), DOI: https://doi.org/10.1016/j.cell.2025.04.019
Cell (2019), DOI: https://doi.org/10.1016/j.cell.2019.01.038