Infrared contact lens gives wearers vision in the dark

27 May 2025

USTC project puts photosensitive nanoparticles into lenses adding infrared- to visible-light perception.

A project at the University of Science and Technology of China (USTC) has developed a contact lens allowing wearers to perceive near-IR wavelengths and see better in the dark.

Described in Cell, the contact lenses are transparent, so they convey both infrared and visible light simultaneously when worn in daylight, and enhance IR vision when worn in the dark or while a subject has their eyes closed.

Unlike conventional night vision goggles, the contact lenses require no external power source. They are also less invasive for the wearer than surgical routes to the same result, such as the injection of photoreceptor nanoparticles into the retina, an approach previously investigated at USTC.

"Our research opens up the potential for non-invasive wearable devices to give people super-vision," said Tian Xue, a UTSC neuroscientist.

"There are many potential applications right away for this material. For example, flickering infrared light could be used to transmit information in security, rescue, encryption or anti-counterfeiting settings."

USTC's breakthrough relies on gold-based upconversion nanoparticles around 45 nanometers in diameter, incorporated into a suitable soft wearable polymeric material to produce upconversion contact lenses, or UCLs.

The team's nanoparticles specifically enable detection of near-IR in the 800 to 1600 nanometer range, coverting it to visible wavelengths. USTC previously showed that these Au/NaGdF₄ nanoparticles enabled infrared vision in mice when injected directly into the retina.

Color-coding nanoparticles

One hurdle for the project was that incorporating nanoparticles into a contact lens material can alter its optical properties, and obtaining high-concentration optically transparent nanocomposites is challenging. The project tackled this through careful control of the nanoparticles' dimensions, and selection of a contact lens polymer with a refractive index close to that of the nanoparticle material.

Trials on mice showed that animals wearing the contact lenses displayed behaviors suggesting that they could see infrared wavelengths, along with physiological signals such as pupil contraction. Brain imaging confirmed that infrared light caused the visual processing centers to light up.

Human subjects wearing the lenses could detect flashing morse code-like signals at infrared wavelengths in a dark room and perceive the direction of incoming infrared light.

"It's totally clear cut: without the contact lenses, the subject cannot see anything, but when they put them on, they can clearly see the flickering of the infrared light," said Tian Xue. "We also found that when the subject closes their eyes they're even better able to receive this flickering information, because near-infrared light penetrates the eyelid more effectively than visible light, so there is less interference from visible light."

The lenses were given additional functionality by using trichromatic upconversion nanoparticles with multiple absorption-emission layers, effectively allowing them to differentiate between different wavelengths of infrared light.

The project's trichromatic UCLs converted IR wavelengths of 980 nanometers into blue light, 808 nanometers into green light, and 1,532 nanometers into red light. As well as enabling wearers to perceive more detail within the infrared spectrum, these color-coding nanoparticles might be modified to help color blind people see wavelengths that they would otherwise be unable to detect.

At present the USTC contact lenses are only able to detect infrared radiation projected from an LED light source, but the researchers are working to increase the nanoparticles' sensitivity so that they can detect lower levels of infrared light.

"In the future, by working together with materials scientists and optical experts, we hope to make a contact lens with more precise spatial resolution and higher sensitivity," commented Tian Xue.