Bioinspired Gyrotropic Metamaterials with Multifarious Wave Adaptability and Multifunctionality

Abstract

Electromagnetic wave loss caused by rotating polarization of chiral structures has long been considered as a disadvantage in transmission, detection, etc., however, it can be turned to benefit in microwave absorbing materials to enhance absorption. Herein, inspired by the chiral structure of jeweled beetles, gyrotropic metamaterials (MMs) are designed and prepared, and experimentally demonstrate the enhanced microwave absorption by rotating polarization; the bandwidth of absorptivity greater than 80% (reflection loss, RL ≤ −7 dB) covers the entire 4–18 GHz frequency range under an ultralow surface density of 1.45 kg m−2; the mechanism analyzed and verified by simulation models demonstrates this a universal method. A new paradigm of MMs fabricated by high entropy alloy (HEA) is offered in this work, which increases the freedom of MM design and promotes the integration of material science and physics. Multifarious wave adaptability and multifunctionality achieved by integrated HEA unit cell and foamed polyurethane realize ultrasonic and water wave absorption, as well as impact and corrosion resistance. These designs hold great promise for facilitating functionally integrated materials for stealth technology, antiterrorist, encryption, sensing, and photon detection.

Optimized Absorption Performance of FeSiCr Nanoparticles by Changing the Shape Anisotropy

“…By calculating the impedance matching of all samples, the calculated value of | Z in / Z 0 | is equal to 1, by which perfect impedance matching can be obtained. [ 25,27,28 ] The impedance matching of S3 and S4 is closest to one from Figure 8d, so samples S3 and S4 have excellent absorption performance.…”

High-Yield Two-Dimensional Metal–Organic Framework Derivatives for Wideband Electromagnetic Wave Absorption

“…Figure a–f shows the RL of the MOF-derived Co/Ni/C composites calculated based on the transmission line theory as follows , where Z in is the input impedance of the absorber, Z 0 is the impedance of free space, d is the thickness of the absorber, and f and c are the frequency of EM wave and the velocity of light, respectively. The bulk derivative presents the minimum RL of −47.2 dB and EAB (RL < −10 dB) of 1.9 GHz at a thickness of 5.3 mm.…”

Chiral Asymmetric Polarizations Generated by Bioinspired Helical Carbon Fibers to Induce Broadband Microwave Absorption and Multispectral Photonic Manipulation

“…In this context, chiral microstructure is expected to provide a new path to solve above-mentioned bottlenecks of MAMs. [35] Chiral structure has special symmetry that its mirror image cannot be superimposed with it via any symmetrical operations, [36] which give rise to particular electromagnetic coupling: [27] the chiral electric dipole can not only derive electric polarization, but also magnetic polarization, and vice versa (Note S1, Supporting Information), which thus expected to improve impedance match and absorption bandwidth. Carbon fiber, [37] carbon nanotube, [38] polypyrrole, [39] and polyaniline [40] etc.…”

“…Metastructures can give MAMs additional effect to form metamaterials, [ 21 ] which could improve the absorption bandwidth by constructing equivalent circuit models, [ 22 ] vortex current loss, [ 23 ] overlapped reflections, [ 24 ] and polarization rotation, [ 25 ] etc., a metamaterial with square unit cells made of carbon black can achieve absorption bandwidth that 2.35–18 GHz (absorptivity more than 96.8%) under thickness of 17 mm, [ 26 ] our previous works brought optical rotation of chiral metamaterials based on high entropy alloys to consume microwaves, the effective absorption bandwidth (RL ≤ −10 dB) covered 4–5.54, 6.66–8.12, and 8.84–18 GHz under 20 mm thickness. [ 27 ] Whereas the thickness of metamaterials has to close to wavelength, because the loss effects of metamaterials are generated by subwavelength resonance that based on wave theory, thus difficult to broadband absorption under thin thickness. On the other hand, microstructures could manipulate the electromagnetic loss effectively, e.g., the core–shell microstructure in favor of enhance interface polarization, [ 28 ] porous microstructure facilitate to eliminate the skin effect at interface to consume microwaves, [ 29 ] flake microstructure tend to break through the Snoek limit of ferromagnetic materials to improve magnetic loss, [ 30 ] as well as the orientation, [ 7 ] defects, [ 31 ] distribution, [ 32 ] spacing, [ 33 ] and size [ 34 ] of the microstructures have significant effects on absorption.…”

“…Metastructures can give MAMs additional effect to form metamaterials, [21] which could improve the absorption bandwidth by constructing equivalent circuit models, [22] vortex current loss, [23] overlapped reflections, [24] and polarization rotation, [25] etc., a metamaterial with square unit cells made of carbon black can achieve absorption bandwidth that 2.35-18 GHz (absorptivity more than 96.8%) under thickness of 17 mm, [26] our previous works brought optical rotation of chiral metamaterials based on high entropy alloys to consume microwaves, the effective absorption bandwidth (RL ≤ −10 dB) covered 4-5.54, 6.66-8.12, and 8.84-18 GHz under 20 mm thickness. [27] Whereas the thickness of metamaterials has to close to wavelength, because the loss effects of metamaterials are generated by subwavelength resonance that based on wave theory, thus difficult to broadband Chirality, in which electromagnetic characteristic promotes asymmetric polarization, is expected to realize broadband absorption for microwave absorption materials (MAMs). Herein, inspired by the microstructure of nepenthes, a scalable approach is reported for fabricating hierarchical-chiral helical carbon fibers with broadband microwave absorption as well as multispectral chiral manipulation.…”