A new material that can bend light
University of Glasgow
Scientists have discovered a technique that can bend light around edges, inspired by the way clouds scatter sunlight. This type of light bending could lead to advances in medical imaging, electronics cooling, and even nuclear reactor design.
Daniele Fazio The researchers and their colleagues at the University of Glasgow, UK, said they were shocked that this type of light scattering had not been discovered before. It works on the same basis as clouds, snow and other white substances that absorb light. Once a photon hits the surface of such a material, it scatters in all directions, barely penetrates, and reflects in all directions. For example, when sunlight hits a large cumulonimbus cloud, it reflects off the top, making this part of the cloud appear bright white. However, because so little light reaches the bottom of the cloud, this part appears gray even though it is made up of identical water droplets.
“The light bounces around, trying to come in, and then bounces off all the molecules and defects,” Faccio said. “And eventually, because it can’t go in, it bounces back. That’s scattering.”
To replicate this process, the team 3D printed the object with an opaque white material, leaving behind a thin tunnel of transparent resin. When light hits a material, it travels into a tunnel and scatters, like light on snow or a cloud. But instead of scattering randomly in all directions until they are uniformly dispersed, the photons are directed by the opaque material back into the resin tunnel. The team used this to create a variety of objects that systematically manipulate light.
3D printed white block with curved channels guiding scattered light
University of Glasgow
These 3D printed objects are functionally similar to fiber optic cables that transmit light along their length, but operate on fundamentally different principles. Fiber optic cables internally manipulate light by reflecting it infinitely. When a photon attempts to leave the inner plastic or glass core of the cable, it hits another material with a lower index of refraction and is reflected back inside. In this way, light can travel for kilometers at a time, even through curves.
The researchers say their material can improve light transmission by more than two orders of magnitude compared to a solid block without the same clear tunnel and direct it around a curve. It is much less efficient than optical fiber and therefore has trouble reaching long distances, but it is very simple and inexpensive.
This light bending method could provide a new way to perform medical imaging by utilizing existing tunnels in translucent materials, such as tendons or body fluids in the spine. Faccio says the same principle also works to induce heat and neutrons, so it could also be used in a variety of engineering applications, such as cooling systems and nuclear reactors.
“It wasn’t clear if this would work at all. We were shocked,” says Faccio. He believes this phenomenon could have easily been discovered decades or even centuries ago. “It’s not like we created or discovered some very niche, strange equations with strange properties.”
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