Soft contact lenses made from a polymer nanocomposite enabled human volunteers to perceive infrared light [Image: Yuqian Ma, Yunuo Chen, Hang Zhao]
Researchers in China have created soft and flexible contact lenses that enable people to perceive infrared light with a near-naked eye (Cell, doi: 10.1016/j.cell.2025.04.019). The wearable technology converts infrared light into the visible regime, allowing humans to recognize both spatial patterns and time-based signals, while different infrared wavelengths can be also be used to generate red, green and blue light.
Seeing the near-infrared
The contact lenses incorporate nanoparticles that absorb near-infrared light and upconvert it into the visible range. In previous work, the team had shown that these nanoparticles can produce infrared vision in mice when injected into the retina, but to create a less-invasive solution they combined the nanoparticles with the nontoxic polymers that are used to make standard soft contact lenses.
By carefully matching the optical properties of the nanoparticles to the polymer material, the researchers produced lenses containing a high concentration of nanoparticles—about 7% by weight—while still maintaining a transparency of more than 90% across most visible wavelengths. Tests showed that the excitation and emission spectra of the nanoparticles were unaffected by the fabrication process and that the lenses could convert infrared light of differing intensities into visible light.
When the contact lenses were attached to the eyes of living mice, their pupils were found to contract when illuminated by infrared light. By measuring the electrical and optical signals produced within the primary visual cortex, the team showed that near-infrared light generates the same visual response as would normally be expected for visible wavelengths.
Interestingly, their sensitivity to infrared light improved when the volunteers had their eyes closed, since the longer wavelengths penetrate the eyelid more effectively than visible light.
In trials with human volunteers, the contact lenses enabled participants to perceive the direction of incoming infrared light and to recognize simple shapes. They were also able to identify strings of letters by decoding timed sequences of flashing light. Interestingly, their sensitivity to infrared light improved when the volunteers had their eyes closed, since the longer wavelengths penetrate the eyelid more effectively than visible light.
Toward super-vision
The researchers then modified the design of the nanoparticles to convert near-infrared light at three different wavelengths into red, green and blue light. Contact lenses produced with these nanoparticles enabled the volunteers to discern three primary colors in the near infrared, with this additional information enabling them to interpret complete sentences from the flashing sequences of light.
While light scattering currently limits the ability of the contact lenses to capture fine detail, the team used the same nanoparticle technology to develop wearable glasses that enabled participants to see high-resolution infrared information and to recognize simple colored patterns. The researchers believe that the nanoparticles could be further engineered to achieve the same visual performance in the contact lens format, while the nanoparticles could also be modified to enable people with color blindness to see the full visible spectrum. “Our research opens up the potential for noninvasive wearable devices to give people super-vision,” says senior author Tian Xue, a neuroscientist at the University of Science and Technology of China.