We humans see because our eyes have light -sensitive cells – cones and rods – which detect electromagnetic wavelengths between about 400 nanometers (violet) and 700 nanometers (red).
This means that nearby infrared radiation (NIR in English), which has a longer wavelength, is not enough energy to activate our photoreceptor cells located on the eye retina.
Thus, when we need to see infrared light, as wildlife observations at night, for example, we need to resort to bulky glasses or night vision devices with their own energy source. At least so far.
a team of researchers at the University of Science and Technology of Hefei in East China announced the creation of contact lenses that allow the vision of infrared radiation in humans and mice.
A surprising aspect of the new invention is that, as lenses are transparent, users can see visible and infrared light at the same time, although the latter is better perceived when the user has their eyes closed, for the light nir crosses the eyelids.
Testing contact lenses in rats and men
Special contact lenses that allow humans to see in the dark are soft and made of polymeric composites. This gelatinous material is combined, sodium gadolinium fluoride and metallic ions such as itérbio and erbium.
They are called ascending conversion contact lenses because they turn infrared radiation between 800 and 1,600 nanometers into visible light. In the process, the nanoparticles present in the lenses enrich the waves of infrared light with energy, converting them into three primary colors.
One of the challenges faced by the team was the low sharpness of the images, due to the spread of light caused by nanoparticles. To circumvent the problem, the researchers added supplementary corrective lenses, partially improving the definition of perceived visual results.
But even with advances, infrared lenses do not yet reach the power of traditional night vision glasses that amplify weak infrared signs more efficiently. The wearable devices, in turn, are more discreet and practical as they do not require large equipment.
To reach the lenses, the team tested technology injecting nanoparticles directly into the retinas of mice, which came to see in the dark. With nanoparticles in the lens, humans also managed to recognize patterns, letters and infrared signs, even with eyes closed.
Visible infrared light applications
Some animals, such as snakes and bats, can detect infrared radiation through specialized sensory organs that perceive the heat emitted by the bodies. This mechanism creates a thermal image processed by the brain, but does not surround the eyes or the formation of images.
Humans, with the upward conversion lenses, do not perceive heat, but see the infrared light as if it were visible light. The nanoparticles in the lens transform the invisible radiation into colors that activate the retinal cones and rods, allowing to form real but less clear images.
For developers, Chinese innovation has the potential to boost a billionaire market, with applications in surgical procedures, encryption and counterfeiting protection, such as hidden documents in documents.
In addition, lenses could help rescue people in low visibility environments, detecting heat -emitting objects. Applications range from military industry to consumer technology solutions for everyday life, such as assistance to colorblinds and integration with wearable devices.
Despite the existing limitations, the creation of these lenses represents a remarkable advance in the expansion of human sensory capabilities. The possibility of perceiving color infrared light paves the way for future use in safety, medicine and support for visually impaired people.
