They have been created by a team of Chinese and US bioengineers by injecting nanoparticles into the contact lens “mixture”. These innovative infrared lenses enable wearers to see in the dark.
What if you could see in the dark, like a comic strip superhero, without wearing goggles or devices that need batteries, but just using normal – or close to normal – contact lenses?
The idea could soon become a reality with new lenses created by a multidisciplinary team of Chinese and US bioengineers who have published the results of their studies in the prestigious scientific journal Cell.
The contact lenses capture infrared light, giving humans night vision
The ability to see in the dark is thanks to special nanoparticles – particles with a diameter of approximately one millionth of a millimetre – which, when combined with the standard plastic polymers used in contact lenses, allow infrared light to be “captured” and converted into wavelengths that are visible to the human eye.
Infrared rays are almost always there, even when it seems pitch black to us, because they don’t depend solely on common light sources (like the sun or light bulbs), but are linked to thermal radiation: as a rule, any object with a temperature above absolute zero (-273.15 °C) emits infrared radiation. So even our bodies, a wall, a tree or animals in the night produce infrared waves, which our eyes are however unable to see. The Earth, for that matter, also emits heat in the infrared spectrum, which is how weather satellites “see” clouds when it’s dark.
The first tests with the new contact lenses, conducted on laboratory animals, have confirmed that these devices work.
Mice wearing the lenses were able – in the dark – to make out a series of obstacles and objects “illuminated” by infrared LEDs. What’s more, the pupils of the mice constricted in the infrared light and MRI scans showed that the areas of the brain involved in visual processing were activated.
Infrared light even passes through closed eyelids
In a second stage, the lenses were also tested on humans. Notably, a group of volunteers could accurately detect flashing Morse code-like infrared signals in the dark and were even able to tell what direction the infrared light was coming from. “We also found that when the subject closes their eyes, they’re even better able to receive this flickering information, because... infrared light penetrates the eyelid more effectively,” explained Tian Xue, leader of the study and researcher at the University of Science and Technology of China.
Finally, further tweaking of the lenses made it possible to associate a series of visible colours with different infrared wavelengths. For example, infrared light at 980 nanometres was converted into blue light, at 808 nm into green light and at 1,532 nm into red light. This technique to translate infrared wavelengths into different colours could be used, say the researchers, in another setting, to help people with colour blindness, enabling them to distinguish colours that would otherwise be invisible.
High-resolution glasses are available
For now, the contact lenses are only able to detect infrared radiation emitted from an LED light source. However, the researchers are working to make them more sensitive and precise, so they can detect lower levels of infrared light, too. Alongside this, a wearable system, similar to a pair of glasses, has also been developed that improves image resolution. “There are many potential applications right away for this material,” said Tian Xue. “For example, flickering infrared light could be used to transmit information in security, rescue, encryption or anti-counterfeiting settings.”
