Lightweight absorption-dominated electromagnetic interference (EMI) shielding materials are more attractive than conventional reflection-dominated counterparts because they minimize the twice pollution of the reflected electromagnetic (EM) wave. Here, porous Ti2CT x MXene/poly(vinyl alcohol) composite foams constructed by few-layered Ti2CT x (f-Ti2CT x) MXene and poly(vinyl alcohol) (PVA) are fabricated via a facile freeze-drying method. As superior EMI shielding materials, their calculated specific shielding effectiveness reaches up to 5136 dB cm2 g-1 with an ultralow filler content of only 0.15 vol % and reflection effectiveness (SER) of less than 2 dB, representing the excellent absorption-dominated shielding performance. Contrast experiment reveals that the good impedance matching derived from the multiple porous structures, internal reflection, and polarization effect (dipole and interfacial polarization) plays a synergistic role in the improved absorption efficiency and superior EMI shielding performance. Consequently, this work provides a promising MXene-based EMI shielding candidate with lightweight and high strength features.

Lightweight Ti2CTx MXene/Poly(vinyl alcohol) Composite Foams for Electromagnetic Wave Shielding with Absorption-Dominated Feature

Synthesis of fish skin-derived 3D carbon foams with broadened bandwidth and excellent electromagnetic wave absorption performance

Engineering morphology configurations of hierarchical flower-like MoSe2 spheres enable excellent low-frequency and selective microwave response properties

Active metamaterials and metadevices: a review

Synthesis of Ti3C2/Fe3O4/PANI hierarchical architecture composite as an efficient wide-band electromagnetic absorber

Facile synthesis of hierarchical chrysanthemum-like copper cobaltate-copper oxide composites for enhanced microwave absorption performance.

Acoustic metamaterial science is an emerging field at the frontier of modern acoustics. It provides a prominent platform for acoustic wave control in subwavelength-sized metadevices or metasystems. However, most of the metamaterials can only work in a narrow frequency band once fabricated, which limits the practical application of acoustic metamaterials. This paper highlights some recent progress in tunable acoustic metamaterials based on various modulation techniques. Acoustic metamaterials have been designed to control the attenuation of acoustic waves, invisibility cloaking, and acoustic wavefront engineering, such as focusing via manipulating the acoustic impedance of metamaterials. The reviewed techniques are promising in extending the novel acoustics response into wider frequency bands, in that tunable acoustic metamaterials may be exploited for unusual applications compared to conventional acoustic devices.

A Review of Tunable Acoustic Metamaterials

We investigate the electrically tunable Electromagnetic induced transparency (EIT)-like effect of active metamaterial structures composed of a wire and a split ring resonator by the simulation, experiment, and temporal coupled-mode theory It is illustrated that an EIT-like effect appears as a result of weak coupling between bright and dark resonators Around the EIT-like peak frequency, the superradiant resonance mode of the bright resonator is highly suppressed by the subradiant resonance mode of the dark resonator, and high transmittance as well as large group delay is manifested By integrating a varactor diode into the EIT structure and altering the bias voltage, the EIT-like effect can be dynamically tuned As the bias voltage ranges from 0 V to 8 V, the EIT-like peak frequency exhibits a prominent blueshift of 022 GHz and the transmittance experiences a modulation with a modulation depth up to 98% Using the temporal coupled-mode theory, the transmission spectrum of the EIT structure is predicted 

Weak coupling between bright and dark resonators with electrical tunability and analysis based on temporal coupled-mode theory

Engineering Coiling‐Up Space Metasurfaces for Broadband Low‐Frequency Acoustic Absorption

An acoustic metagrating composed of Helmholtz-resonators is demonstrated to control the propagation direction of acoustic waves. The transmissive acoustic wavefront steering is realized by simply modulating the geometric parameters of the resonators as well as the phase delay to coherently suppress the unwanted diffractions orders and to achieve the expected wave propagation. • A kind transmissive acoustic beam steering is designed and demonstrated by simply modulating the phase response of the three high-transmissive resonators which is promising for high efficiency wavefront manipulation. • It is shown that the transmissive metasurface (metagrating) can be designed for the controlling of acoustic wave with classical Helmholtz-resonators. • The designed metagraing is well demonstrated in experiments for novel beam steering and the designed function can operate in a wide-angle range of 0°-28°. Recently, a kind simply structured metasurface made of binary phase modulated meta-unit shows extraordinary beam steering functionality especially in the reflective beam manipulation. In this work, we demonstrate a Helmholtz-resonator based acoustic metagrating for high efficient beam wavefront steering in transmissive configuration. The complex meta-unit of the metagrating made of three Helmholtz-resonators combines traditional diffraction and interference theory with the free phase modulation ability of local resonant periodic structure to coherently control the acoustic wavefront steering. We show numerically and experimentally the anomalous refraction can be acquired with the designed metagrating of subwavelength thickness. By properly designing the geometric parameters of the meta-unit, the -1st order diffraction can be retained, and the unexpected diffraction orders are eliminated through destructive interference for a high efficient anomalous refraction. The anomalous refraction performance of the proposed metagrating is achieved over a wide incident range. The reported structure is promising for high efficient and wide angle complex wavefront engineering in e.g. encryption or communications. 

Shuang Chen

Papers

Facile synthesis of hierarchical chrysanthemum-like copper cobaltate-copper oxide composites for enhanced microwave absorption performance.

A Review of Tunable Acoustic Metamaterials

Weak coupling between bright and dark resonators with electrical tunability and analysis based on temporal coupled-mode theory

Engineering Coiling‐Up Space Metasurfaces for Broadband Low‐Frequency Acoustic Absorption

High Efficient Transmissive Wavefront Steering with Acoustic Metagrating Composed of Helmholtz-Resonators