Microwave and Acoustic Absorption Metamaterials

TL;DR

This review explores the absorption mechanisms of microwave and acoustic metamaterials, introduces a universal resonance model, and discusses recent advances and future challenges in broadband absorption near fundamental limits.

Contribution

It establishes a universal resonance-based model for absorption in metamaterials and surveys recent progress towards performance limits and novel low-frequency absorption metastructures.

Findings

Recent advances approach the causal limit for absorption performance.

Emerging metastructures can bypass causal constraints for low-frequency absorption.

Theoretical framework guides design of broadband, high-efficiency metamaterials.

Abstract

Wave absorption metamaterials have been an enduring topic over the past two decades, propelled not only by novel scientific advances, but also by their extensive application potential. In this review, we aim to provide some general insights into the absorption mechanism common to both microwave and acoustic systems. By establishing a universal model for resonance-based metamaterials, we present the theoretical conditions for broadband impedance matching and introduce the fundamental causal limit as an evaluation tool for absorption performance. Under this integrated framework, we survey the recent advances on metamaterials absorption in both microwave and acoustic systems, with the focus on those that pushed the overall performance close to the causal limit. We take note of some new, emerging metastructures that can circumvent the constraint imposed by causal limit, thereby opening a new avenue to low-frequency absorption. This review concludes by discussing the existing challenges with possible solutions and the broad horizon for future developments.