Using Grains to Control Sound Waves
Crystals are important materials because of their well-ordered molecular structures. By controlling these structures, it is possible to affect control on waves including light waves and sound waves. Now researchers at MIT have started examining how microscopic grains can be used in a similar way.
Though visibly dissimilar, granular materials can behave like crystals, as the grains order themselves like molecules ordering themselves in crystals. Researchers have known this for some time, but have typically kept to studying grains about the size of a piece of sand. The MIT researchers decided to go about a thousand times smaller, with grains just one micrometer across. By carefully attaching the microspheres to a substrate, the researchers were able to create a 2D granular material capable of guiding and slowing surface acoustic waves. These types of waves are used in a variety of electronics, including cellphones.
As the material the researchers made is two dimensional, they suspect it may be possible to shrink the devices that process surface acoustic waves to one-sixth their current size. Also by combining layers of the material, it should be possible to create a blast-shielding material that protect against an explosion's shock waves.