Researchers in China have developed contact lenses that could allow humans to see in the dark using infrared vision.
The team, led by Professor Tian Xue and Professor Yuqian Ma from the University of Science and Technology of China (USTC), collaborated with multiple research groups to enable human near-infrared (NIR) spatiotemporal colour vision.
A media release said that, in nature, electromagnetic waves span a wide range of wavelengths, but the human eye can perceive only a narrow portion known as visible light, making NIR light beyond the red end of the spectrum invisible to us.
In 2019, a team at USTC achieved a breakthrough by injecting nanomaterials into the retinas of animals, enabling the first-ever naked-eye NIR image vision capability in mammals.
But the challenge remained about how to apply this to humans through non-invasive means.
The team infused contact lenses with nanoparticles that convert near-infrared light in the 800–1,600 nanometre range into the 400–700 nanometre range.
The new lenses offer multi-coloured infrared images that night-vision goggles, which operate on a monochrome green scale, typically do not. They also pick up intense infrared signals, such as those emitted by light-emitting diodes (LEDs).
To create the contact lenses, the research team added nanoparticles made of rare-earth metals, including ytterbium and erbium, to a soup of polymer building blocks to form the soft lenses.
Prof Ma told Nature journal that during tests, participants could see flickering infrared light from an LED well enough to pick up Morse code signals and sense which direction the signals were coming from.
“Witnessing people wearing contact lenses and successfully seeing infrared flashes was undoubtedly an exhilarating moment,” Prof Ma said.
Further research will involve improving the technology’s sensitivity to enable the nanoparticles to convert light with higher efficiency.
The researchers said the study, which demonstrated a wearable solution for NIR vision in humans through contact lenses, provided a proof of concept for NIR colour vision and opened up promising applications in security, anti-counterfeiting, and the treatment of colour vision deficiencies.
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