A research team from the University of Science and Technology of China, in collaboration with researchers from Fudan University and international research institutions, has developed a highly transparent, high-conversion-efficiency upconversion contact lens that can enable humans to gain near-infrared spatiotemporal color image vision. The relevant research results were published online in Cell on May 22.
In nature, visible light that can be perceived by the human eye only accounts for a very small part of the electromagnetic spectrum. In previous studies, researchers injected an upconversion nanoparticle that can convert near-infrared light into visible light into the animal retina, enabling mammals to have naked-eye near-infrared image vision for the first time. However, intraocular injections are limited in human application. Therefore, how to achieve near-infrared vision in a non-invasive way has become a key challenge facing the practical application of this technology.
Soft transparent contact lenses made of polymer materials provide a wearable solution. However, the preparation of near-infrared light upconversion contact lenses requires solving two problems, namely how to achieve efficient upconversion capability and good optical performance. To this end, the researchers modified the surface of upconversion nanoparticles to improve their uniform dispersion in polymer materials, and screened polymer materials that matched the refractive index of upconversion nanoparticles to prepare near-infrared light upconversion contact lenses with high doping ratio and high transparency.
Upconversion contact lenses. Image provided by the research team
The experimental results show that mice wearing the contact lenses can distinguish near-infrared light information of different temporal frequencies and different directions. After wearing the contact lenses, human volunteers can not only see near-infrared light within a certain range of light intensities, but also accurately identify the time-coded information of near-infrared light.
In addition, the researchers have developed a wearable frame glasses system with built-in near-infrared light upconversion contact lenses, which enables human volunteers to obtain near-infrared image vision with the same spatial resolution as visible light vision and accurately identify complex near-infrared graphics.
In addition to time and space information, visual perception can also convey rich information in the color dimension. The researchers replaced traditional upconversion nanoparticles with three-color orthogonal upconversion nanoparticles to prepare three-color upconversion contact lenses. The experimental results show that human volunteers wearing three-color upconversion contact lenses can effectively identify three wavelengths of near-infrared light and perceive a variety of near-infrared colors. This shows that three-color upconversion contact lenses can effectively enable humans to acquire the ability to see near-infrared color images.
According to the researchers, there is still room for improvement in this technology. For example, the current upconversion efficiency still requires auxiliary irradiation with infrared light sources. In addition, if upconversion contact lenses can achieve directional output of emitted light, they may not rely on the frame optical system and directly realize contact lens-mediated fine near-infrared graphic vision. All of this depends on interdisciplinary cooperation in visual physiology, material science and optics. In the future, this technology has broad application prospects in the fields of medicine, information processing and visual assistance technology.
Related paper information: https://doi.org/10.1016/j.cell.2025.04.019
(Original title: "New contact lenses give humans near-infrared color image vision")