Chinese researchers have successfully built an electromagnetic（电磁的） absorbing（吸引人的） device for microwave frequencies. The device, made of a thin cylinder¹（汽缸，圆筒） comprising 60 concentric rings of metamaterials（材料） , is capable of absorbing microwave radiation, and has been compared to an astrophysical（天体物理学的） black hole (which, in space, soaks up吸收 matter and light). The research published today, Thursday, 3 June, in New Journal of Physics (co-owned by the Institute of Physics and German Physical Society), shows how the researchers utilised the special properties of metamaterials, a class of ordered composites which can distort（扭曲） light and other waves.

Qiang Cheng and Tie Jun Cui of the State Key Laboratory of Millimeter Waves at Southeast University in Nanjing, China, designed and fabricated（制造，组装） their absorbing device, officially called an "omnidirectional（全方向的） electromagnetic absorber", using 60 strips of circuit board arranged in concentric（同轴的） layers coated in copper². Each layer is imprinted³ with alternating patterns, which resonate（共鸣，共振） or don't resonate in electromagnetic waves.

The designed device can trap and absorb electromagnetic waves coming from all directions by spiraling（盘旋的） the radiation inwards and converting its energy into heat with an absorption rate of 99%. Hence it behaves like an "electromagnetic black body" or an "electromagnetic black hole".

At the moment, the device only works with microwaves, but the researchers are planning to develop a black hole for visible light next.

The current results could find some applications in microwaves. As the researchers write, "The good agreement between theoretical and experimental results has shown the excellent ability for metamaterials as the candidate to construct artificial omnidirectional absorbing devices.

"Since the lossy core can transfer electromagnetic energies into heat energies, we expect that the proposed device could find important applications in thermal⁴（热的，热量的） emitting（发射，散发） and electromagnetic-wave harvesting."