Wideband-Switchable Metamaterial Absorber Using Injected Liquid Metal

Abstract

Metamaterial absorbers can provide good solutions for radar-cross-section (RCS) reduction. In spite of their attractive features of thinness, lightness, and low cost, resonant metamaterial absorbers have a drawback of narrow bandwidth. For practical radar applications, wideband absorbers are necessary. In this paper, we propose a wideband-switchable metamaterial absorber using liquid metal. In order to reduce RCS both for X-band and C-band, the switchable Jerusalem cross (JC) resonator is introduced. The JC resonator consists of slotted circular rings, chip resistors, and microfluidic channels. The JC resonator is etched on a flexible printed circuit board (FPCB), and the microfluidic channels are laser-etched on a polydimethylsiloxane (PDMS) material. The proposed absorber can switch the absorption frequency band by injecting a liquid metal alloy into the channels. The performance of the absorber was demonstrated through full-wave simulation and through measurements employing prototypes. The experimental results showed absorption ratios of over 90% from 7.43 GHz to 14.34 GHz, and from 5.62 GHz to 7.3 GHz, with empty channels and liquid metal-filled channels, respectively. Therefore, the absorption band was successfully switched between the C-band (4–8 GHz) and the X-band (8–12 GHz) by injecting liquid metal eutectic gallium indium alloy (EGaIn) into the channels.

Frequency-Tunable Electromagnetic Absorber by Mechanically Controlling Substrate Thickness

“…Most frequency-tunable metamaterial absorbers have been realized using electronic devices such as diodes [25][26][27], microelectromechanical systems (MEMS) [28][29][30], and liquid crystal technology [31,32]. Recently, fluidically tunable metamaterial absorbers have been proposed using liquid metal [33][34][35]. These electrically tunable devices show an instantaneous response.…”

Fluidically Switchable Metasurface for Wide Spectrum Absorption

“…Additionally, they can exhibit switchable conductivity via external control, thus offering a good alternative in adaptive metasurfaces in the microwave regime. Recently, a microfluidically-reconfigured switchable broadband absorber has been demonstrated based on the coupling between the top metallic geometry and bottom liquid-metal-filled channels 43 . However, the proposed structure suffers from polarization-sensitive behaviour, and exhibits small absorption bandwidth.…”

Pixelated Checkerboard Metasurface for Ultra-Wideband Radar Cross Section Reduction

“…Basically, there are two main ways to achieve this objective. In the first approach, the object is covered with a radar absorbing material (RAM) converting the incident EM energy into heat 17 – 19 . Although, applying RAM has certain advantages, it has drawbacks including high overall material thickness, heavy weight, and high material and maintenance cost.…”