Korean researchers have developed a flexible “snake-shaped” metamaterial absorber with the ability to suppress electromagnetic radiation.
Scientists have studied metamaterials since the late 19th century, when artificial dielectrics were developed just after World War II. These artificial materials are specially engineered to affect electromagnetic radiation, sound or seismic waves in a unique manner not achievable with conventional materials.
One such special characteristic, the ability to reverse the refractive index, was of particular interest to physicists at Hanyang University in Seoul, Korea looking for better methods of suppressing electromagnetic waves. They theorized that tapping into a negative index of refraction could be the key to smaller, thinner metamaterial absorbers.
“The unit size of typical metamaterial absorbers, however, is still only one-third to one-fifth of the wavelength of the incident electromagnetic wave,” YoungPak Lee, a physics professor at Hanyang University, said.
The team’s initial effort to design a metamaterial absorber for long-wavelength MHz electromagnetic waves failed, according to a press release from the American Institute of Physics (AIP)—the unit size actually increased, limiting its applications in suppressing radiation from mobile devices and other electric equipment. However, while addressing this problem, the researchers discovered a method of creating a flexible metamaterial absorber, using “snake-shaped” structures to enhance its inductance and shrink the unit size.
“In this case, think of the length of the ‘snake bar’ as the inductance. When we increase the length of the snake bar, the frequency of the resonance peak shifts to a lower frequency (longer wavelength)— keeping the unit size small,” Lee said. “By using a Teflon substrate as the dielectric layer, we can make it thin and elastic enough to be suitable as a flexible metamaterial.” With the new design, the successfully created two types of absorbers at 2 GHz and 400 MHz.
Lee points out that since the unit size of typical metamaterial absorbers is one-third to one-fifth of the wavelength of the incident electromagnetic wave, the unit size would likely to increase in the long-wavelength range. Surprisingly, however, the research “showed that the unit size using the snake-shaped structure is nearly one-twelfth at 2 GHz (single snake bar) and one-thirtieth at 400 MHz (5 snake bars)— making it entirely suitable for real applications,” he said.
The researchers are now focused on creating an even lower-frequency metamaterial absorber, with a range below 400 MHz, while still maintaining a small size and flexibility. They are also working on the development of wideband and thinner metamaterial absorbers within the MHz range.
The article, “Flexible and Elastic Metamaterial Absorber for Low Frequency, Based on Small-Size Unit Cell,” is published in the journal Applied Physics Letters. Additional authors include Y.J. Yoo, H.Y. Zheng, Y.J. Kim, J.Y. Rhee, J.H. Kang and K.W. Kim.
