Scientists create night-vision contact lenses that even work with your eyes closed
Unlike night vision goggles, these lenses do not require a power source and allow the wearer to perceive a range of infrared wavelengths, and researchers say they could give people 'super-vision'.
Professor Tian Xue, from the University of Science and Technology in China, said: 'Our research opens up the potential for non-invasive wearable devices, and there are many potential applications right away.
'For example, flickering infrared light could be used to transmit information in security, rescue, encryption or anti-counterfeiting settings.'
Humans can see a range of light waves called the visible light spectrum, which encompasses wavelengths from around 380 to 700 nanometers.
The contact lens technology uses nanoparticles that absorb light we cannot see and converts it into wavelengths that are visible.
These nanoparticles specifically enable detection of 'near-infrared light', which is infrared light in the 800-1600 nanometer range - just beyond what humans can already see.
The team previously showed that these nanoparticles enable infrared vision in mice when injected into the retina, but they wanted to design a less invasive option.
To create the contact lenses, they combined the nanoparticles with flexible, non-toxic polymers that are used in standard soft contact lenses.
Tests showed that the contact lenses allowed humans to accurately detect flashing morse code-like infrared signals in pitch blackness.
They could even see better when they had their eyes closed, as it blocked out any interference from light on the normal visibility spectrum.
'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,' Professor Xue said.
'We also found that when the subject closes their eyes, they're even better able to receive this flickering information.
'This is because near-infrared light penetrates the eyelid more effectively than visible light, so there is less interference from visible light.'
An additional tweak to the contact lenses meant the nanoparticles could color-code different infrared wavelengths.
For example, infrared wavelengths of 980 nanometers were converted to blue light, wavelengths of 808 nanometers were converted to green light, and wavelengths of 1,532 nanometers were converted to red light.
This allowed wearers to perceive more detail in what they were seeing.
It could also one day help colorblind people see wavelengths that they would otherwise be unable to detect, the researchers said.
'By converting red visible light into something like green visible light, this technology could make the invisible visible for colorblind people,' Professor Xue said.
Currently, the 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,' Professor Xue said.
Writing in the journal Cell the team said: 'Light plays a particularly essential role in conveying a significant amount of external information for living organisms to comprehend the world.
'However, mammals can only perceive a small fraction of the electromagnetic spectrum as visible light.
'This means that over half of the solar radiation energy, existing as infrared light, remains imperceptible to mammals.
'Here, we report wearable near-infrared up-conversion contact lenses with suitable optical properties…flexibility and biocompatibility.
'Humans wearing [the contact lenses] could accurately detect near-infrared temporal information like Morse code and discriminate near-infrared pattern images.
'Interestingly, humans with [the contact lenses] exhibited better discrimination of near-infrared light compared with visible light when their eyes were closed.'
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