Abstract

Abstract Metamaterials, consisting of subwavelength resonant structures, can be artificially engineered to yield desired response to electromagnetic waves. In contrast to the naturally existing materials whose properties are limited by their chemical compositions and structures, the optical response of metamaterials is controlled by the geometrics of resonant unit cells, called “meta-atoms”. Many exotic functionalities such as negative refractive index, cloaking, perfect absorber, have been realized in metamaterials. One recent technical advance in this field is the active metamaterial, in which the structure of metamaterials can be tuned to realize multiple states in a single device. Microelectromechanical systems (MEMS) technology, well-known for its ability of reconfiguring mechanical structures, complementary metal-oxide-semiconductor (CMOS) compatibility and low power consumption, is perfectly suitable for such purpose. In the past one decade, we have seen numerous exciting works endeavoring to incorporate the novel MEMS functionalities with metamaterials for widespread applications. In this review, we will first visit the fundamental theories of MEMS-based active metamaterials, such as the lumped circuit model, coupled-mode theory, and interference theory. Then, we summarize the recent applications of MEMS-based metamaterials in various research fields. Finally, we provide an outlook on the future research directions of MEMS-based metamaterials and their possible applications.

Highlights

  • Metamaterials, which consist of subwavelength resonant structures, have garnered significant research attention since the first experimental demonstration of negative refractive index [1]

  • In contrast to the naturally existing materials whose properties are limited by their chemical compositions and structures, the optical response of metamaterials is controlled by the geometrics of resonant unit cells, called “meta-atoms”

  • When the incident radiation that matches the spectrum of plasmonic resonators impinges the absorber, heat bends down the bimorph cantilever and the Pt tip touches with the contact pad below

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Summary

Introduction

Metamaterials, which consist of subwavelength resonant structures, have garnered significant research attention since the first experimental demonstration of negative refractive index [1]. To implement the active control of electromagnetic (EM) wave, many materials have been reported in the past a few years, such as liquid crystals [15, 16], graphene [17,18,19], phase change materials [20,21,22], ferroelectric materials [23, 24] and semiconductors [25, 26] Semiconductor, which can be either the substrate or part of the metamaterials, can photoexcite the extra carriers by laser and tune the electric properties of the resonance Among these tuning mechanisms, the most straightforward and efficient method is to geometrically change the configurations of the unit cells because the effective properties of metamaterials are determined by these unit cells. We will give an outlook and discussion about future technologies in this field

Metamaterials and MEMS
Theories and models of metamaterials
Lumped equivalent circuit model
Temporal coupled-mode theory
Numerical modeling
MEMS actuation methods for metamaterials
MEMS actuated metamaterials
Manipulation of wavefront: metalens with tunable focus
Manipulation of wavefront: beam steering
Tunable metasurface-based holograms
Tunable emitter and perfect absorber
Logic operation
Plasmonically enhanced physical sensor
Findings
Conclusion and outlook
Full Text
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