Summary: Researchers have engineered soft contact lenses that let humans and mice perceive near-infrared (NIR) light by converting it into visible wavelengths. The lenses embed specialized upconversion nanoparticles into standard soft contact materials, allowing wearers to detect flickering infrared signals without an external power source. This non-invasive wearable approach preserves normal vision while adding the ability to sense multiple infrared wavelengths, opening possibilities in security, communication, accessibility and visual science.
Tests in both animals and people produced clear behavioral and physiological evidence of infrared perception, including responses even when eyes were closed. The team also developed a color-coding strategy that translates different NIR wavelengths into distinct visible colors, which could support new forms of information transmission and help people with color-vision deficiencies.
Key Facts:
- Nanoparticle upconversion: The lenses use upconversion nanoparticles to absorb near-infrared light (800–1600 nm) and emit visible light in the 400–700 nm range.
- Behavioral evidence: Mice wearing the lenses avoided infrared-lit areas and showed pupil and brain responses consistent with infrared detection.
- Color-coding potential: Engineered nanoparticles can convert different NIR wavelengths into different visible colors, enabling trichromatic NIR perception and potential support for color-blind users.
Source: Cell Press
Overview
Neuroscientists and materials scientists collaborated to build contact lenses that convert invisible near-infrared light into visible light the retina can detect. Unlike conventional infrared night-vision devices, these upconversion contact lenses require no onboard power: the nanoparticles absorb incoming NIR photons and emit visible photons that reach the eye. Because the lenses remain transparent, wearers can see visible and converted infrared light at the same time; in some tests, perception of the converted infrared signal improved when participants closed their eyes, since NIR penetrates the eyelid more effectively and reduces interference from ambient visible light.
“Our research opens up the potential for non-invasive wearable materials that extend human vision,” says senior author Tian Xue of the University of Science and Technology of China. The team highlights near-term use cases such as secure optical communication, rescue operations, encryption of visual signals, and anti-counterfeiting measures where flickering NIR light could carry information that is visible only to lens wearers.
The lenses are made by dispersing biocompatible upconversion nanoparticles into flexible, non-toxic polymer matrices used in standard soft contact lenses. The resulting upconversion contact lenses (UCLs) were validated for basic biocompatibility and optical performance before behavioral and physiological testing in mice and human volunteers.
Animal and human testing
In mice, UCLs produced measurable behavioral choices and physiological signals. When given a choice between a dark enclosure and one illuminated by infrared LEDs, mice wearing UCLs preferred the dark space, while mice without lenses showed no preference. Pupil constriction and brain imaging further indicated that NIR-evoked visual processing took place in visual centers.
Human participants wearing the lenses reliably detected flashing, Morse code–like infrared signals and could judge the direction of incoming infrared light. The authors report a clear on-off effect: subjects could not perceive the NIR signals without the lenses but readily perceived them when wearing UCLs. Closing the eyes sometimes improved detection, reflecting deeper NIR penetration through eyelid tissue relative to visible wavelengths.
Trichromatic color-coding
To expand functionality, the team created trichromatic upconversion contact lenses (tUCLs) that map separate NIR bands to different visible colors. For example, their demonstrations converted 980 nm NIR to blue, 808 nm to green, and 1532 nm to red. This color-coding enables richer NIR spatiotemporal information and suggests potential adaptations to assist people with color vision deficiencies by translating otherwise indistinguishable wavelengths into distinct visible colors.
Because the close proximity of the lenses to the eye can limit fine spatial detail—converted photons scatter before forming a high-resolution image—the researchers also developed a wearable glass system using the same upconversion materials to provide higher-resolution NIR perception in situations where detail matters.
At present, the lenses are optimized to detect infrared light from LED sources in laboratory demonstrations. Ongoing work with materials scientists and optical engineers aims to increase nanoparticle sensitivity and spatial precision so that lenses can work with lower-intensity and more varied NIR sources.
Funding
This research received support from the Science and Technology Innovation 2030 Major Program; the National Key Research and Development Program of China; the Natural Science Foundation; the CAS Project for Young Scientists in Basic Research; the Major Scientific and Technological Program of Anhui Province; the Anhui Provincial Natural Science Foundation; the New Cornerstone Science Foundation; the Feng Foundation of Biomedical Research; and the Human Frontier Science Program.
About this neurotech and visual neuroscience research news
Author: Julia Grimmett
Source: Cell Press
Contact: Julia Grimmett – Cell Press
Image: The image is credited to Neuroscience News
Original Research: Open access. “Near-Infrared Spatiotemporal Color Vision in Humans Enabled by Upconversion Contact Lenses” by Tian Xue et al., published in Cell. The study reports wearable NIR upconversion contact lenses with suitable optical properties, hydrophilicity, flexibility and biocompatibility that enabled NIR temporal and spatial perception in mice and human participants, including trichromatic NIR color discrimination.
Abstract
Near-Infrared Spatiotemporal Color Vision in Humans Enabled by Upconversion Contact Lenses
Humans cannot directly perceive infrared light because of the physical limits of photoreceptive opsins. Detecting multispectral infrared light with the naked eye would be highly desirable for a range of applications. This work introduces wearable near-infrared (NIR) upconversion contact lenses (UCLs) that combine the required optical properties, hydrophilicity, flexibility and biocompatibility. Mice fitted with UCLs could recognize NIR temporal and spatial patterns and make behavioral decisions. Human participants wearing UCLs could discriminate NIR temporal codes and spatial signals. The team further developed trichromatic UCLs (tUCLs) that allow humans to distinguish multiple NIR spectra as three primary colors, achieving NIR spatiotemporal color vision. These results demonstrate the potential of polymeric wearable materials for non-invasive enhancement of human vision to perceive and convey temporal, spatial and color dimensions of NIR light.