Tag archives: metamaterial
By Jon Cartwright
The past few years has seen a steady stream of proposals for cloaking objects, whether it’s from light, heat, water waves, magnetic fields or even time. Now, physicist Sang-Hoon Kim at the Mokpo National Maritime University in Korea is adding to this list, first off with a cloak that could protect buildings from earthquakes.
An earthquake cloak has been proposed before using – as is common in invisibility cloaks – elaborately structured “metamaterials” to guide seismic waves safely around a building. However, Kim, together with Mukunda Das at the Australian National University in Canberra, has put forward a different approach: a metamaterial barrier that dissipates seismic energy as sound and heat. The idea is that many buildings could hide in the “shadow zone” of the barrier. This could be a boon for city planners, who would not have to make cloaks for individual buildings. Kim and Das’s paper has been accepted for publication in Modern Physics Letters B and is available as a preprint entitled “Artificial seismic shadow zone by acoustic metamaterials“.
By Tushna Commissariat
Invisibility cloaks seem to fascinate scientists and the public in equal measure, and every few months a novel design for some sort of metamaterial that cloaks either light or sound catches our eye, if you excuse the pun.
This week, we came across a group of researchers in Spain that claims to have designed, fabricated and tested the first “directional 3D acoustic cloak” that works for airborne sound. Previous designs of acoustic cloak work in water and air, but only if the sound propagates in 2D. Also, many cloaks only work within a narrow band of frequencies, limiting their uses.