Printed Transformable Liquid-Metal Metamaterials and Their Application in Biomedical Sensing

Metamaterial is becoming increasingly important owing to its unique physical properties and breakthrough applications. So far, most metamaterials that have been developed are made of rigid materials and structures, which may restrict their practical adaptation performances. Recently, with the further development of liquid metal, some efforts have explored metamaterials based on such tunable electronic inks. Liquid metal has high flexibility and good electrical conductivity, which provides more possibilities for transformable metamaterials. Here, we developed a new flexible liquid-metal metamaterial that is highly reconfigurable and could significantly extend the working limit facing current devices. The printed electronics method was adopted to fabricate artificial units and then construct various potential transformable metamaterials. Based on metamaterial theory and printing technology, typical structured flexible liquid-metal electromagnetic metamaterials were designed and fabricated. The electronic and magnetic characteristics of the liquid-metal-based electromagnetic metamaterials were evaluated through simulated analysis and experimental measurement. Particularly, the potential of liquid-metal metamaterials in biomedical sensing was investigated. Further, the future outlook of liquid-metal metamaterials and their application in diverse categories were prospected.

Metamaterials

Metamaterials are composites that have extended the concept of a material. They derive their properties from strong coupling between carefully designed and positioned structural units within them and an incident elastic or electromagnetic wave. They are paragons of materials design. In certain frequency ranges of the incident wave they may display properties that no other materials have ever shown, such as negative refraction. First, an elastic metamaterial demonstrates the principle. Electromagnetic metamaterials have been designed using transformation optics to cloak an object and make it invisible in a certain range of frequencies. The concept of metamaterials has been applied to protect cities and coastal regions from seismic waves and ocean waves.

Advanced Electromagnetic Metamaterials for Temperature Sensing Applications

Metamaterials with novel properties have excited much research attention in the past several decades. Many applications have been proposed and developed for the reported metamaterials in various engineering areas. Specifically, for the resonant-type metamaterials with narrow resonance line width and strong resonance strength, the resonant frequency and strength are highly depended on the changings of meta-atom structure and/or substrate media properties induced by the environment physical or chemistry parameters varying. Therefore, physical or chemistry sensing applications for the resonant-type metamaterial units or arrays are developed in recent years. In this mini review, to help the researchers in those fields to catch up with the newly research advances, we would like to summarize the recently reported high-performance metamaterial-inspired sensing applications, especially the temperature sensing applications, based on different kinds of metamaterials. Importantly, by analyzing the advantages and disadvantages of several conventional metamaterial units, the newly proposed high quality-factor metamaterial units are discussed for high-precision sensing applications, in terms of the sensitivity and resolution. This mini review can guide researchers in the area of metamaterial-inspired sensors to find some new design routes for high-precision sensing.

Metamaterials and their applications: An overview

Metamaterials are man-made substances with unique spatial alternations in their constituent components. They are widely used in modifying elastic, acoustic, or electromagnetic properties of materials. Metamaterials induce low/high-frequency band gaps to control wave propagations with different wavelengths and are also frequently applied in microwave engineering, waveguides, dispersion compensation, smart antennas, and lenses. For instance, permittivity and permeability of the metamaterials can take positive or negative values. Due to smaller single-cell dimensions than their wavelength, the selective frequency of surface-based metamaterials is used for waveguiding. The need for adjustable bandgaps can also lead to a plethora of research into metamaterials’ tunability for structures that operate at different speeds. In this article, recent studies in the field of metamaterials and their applications are reviewed. The piezoelectric metamaterials and the electromagnetic metamaterials are introduced that is followed by a review of new types of chiral metamaterials. Additionally, absorber, nonlinear, terahertz, tunable, photonic, selective surface-based frequency in acoustic metamaterials are comparedand some remarks on tuning bandgaps methods in locally resonant metamaterials are provided.