Design and Fabrication of Bioinspired Hierarchical Dissipative Elastic Metamaterials

Fractal Acoustic Metamaterials with Subwavelength and Broadband Sound Insulation

“…To provide further veri cation of the broadband sound insulation performances of the designed materials, the transmission losses and band structures of the metamaterials in the ΓX direction are calculated. Due to increase in the number of structure units, the properties of transmission losses will be better [24,26,29]; to get better sound insulation, we calculate the sound transmission losses of ve units, with results as shown in Figures 4(a)-4(c). First, the calculation results show that there are more bandgaps in the ΓX direction and that the higher transmission losses appear within the ranges of these bandgaps.…”

“…If a structure with multiple resonance modes can be developed to form multiple bandgaps, it will provide a promising basis for achievement of broadband sound insulation. rough studies of labyrinthine fractal structures, researchers have found that multiple resonances appear in these structures [24][25][26][27][28][29] that can produce multiple bandgaps and thus broadband sound insulation. In these labyrinthine fractal structures, the sound waves propagate along the labyrinthine channels rather than in a straight line, which thus greatly increases their transmission paths and produces an ultraslow transmission effect.…”

“…In these labyrinthine fractal structures, the sound waves propagate along the labyrinthine channels rather than in a straight line, which thus greatly increases their transmission paths and produces an ultraslow transmission effect. Because of the increased lengths of their transmission paths, these metamaterials have high refractive indexes and demonstrate extraordinary physical properties, including multiple bandgaps [24][25][26][27][28][29], negative refraction [30,31], and acoustic focusing [32,33]. Liang et al constructed an extreme acoustic metamaterial by coiling up the space using zigzag channels, which caused their material to have negative refraction and sound tunneling properties [30].…”

Chlorophyll-Inspired Tunable Metamaterials With Multi-Negative Refractive Index Bands: The Porphyrin Ring and Hydrophobic Tail Effect

“…MTMs are excited or stimulated by diverse sources and forces, e.g., electromagnetic fields in photonic MTMs, sound waves in acoustic MTMs, and the flow of heat or diffusive particles in thermodynamic MTMs, respectively. There were several attempts to design bioinspired MTM structures in a broad EM spectrum ranging from sound wave to the optical frequency [15][16][17][18][19][20][21]. It was demonstrated that frustule-inspired hierarchical nanostructure designs could be utilized in broadband infrared metamaterial absorbers [15].…”

Acoustic waveguide filters made up of rigid stacked materials with elastic joints

“…In this case, low-frequency band gaps may be obtained, even if heavy resonators and low stiffness cells are required to get wide stop-bands. Improvements in creating wide low frequency band gaps have been obtained by virtue of the concept of effective inertia, consisting in amplifying a small mass through embedded amplification mechanisms (see Yilmaz et al, 2007, Acar and Yilmaz, 2013, Taniker and Yilmaz, 2015, Frandsen et al, 2016 or by mimicking biological structural systems (see Miniaci et al, 2016 andMiniaci et al, 2018). Recently, Yin et al, 2014, and Chen and Wang, 2015, obtained ultra-wide lowfrequency band gaps in composites designed on the thought of staggered and combined soft and hard materials.…”