Design of a resonant Luneburg lens for surface acoustic waves

Octet lattice-based plate for elastic wave control

“…While building such lenses with ordinary composite materials appears a daunting task, employing phononic crystals 38 – 40 or metamaterials 41 , 42 considerably relieves this complexity. From a metamaterial perspective, the cluster of locally resonant rods with graded height, previously discussed, has proven an effective candidate for the design of GRIN lenses 43 – 45 . Its rod-resonance bandgap, besides providing attenuation, serves as tuning variable for the phase velocity of waves traveling in the metastructure and leads to applications at different scales, from acoustics 43 to seismology 46 .…”

Rayleigh wave propagation in nonlinear metasurfaces

“…Several of these resonant interfaces aim at manipulating the propagation of surface waves in elastic substrates, e.g., Rayleigh and Love waves. Metasurfaces of this type can support a rich variety of wave phenomena, such as amplitude attenuation via mode conversion (classical [4] or Umklapp conversion [5]), energy trapping [6], waveguiding [7], and lensing [8,9]. These phenomena are investigated to inform and enable technological applications based on surface acoustic waves (SAW) for signal processing [10], energy harvesting [6], and mitigation devices for ground-borne vibrations [11].…”

Enhanced Energy Harvesting of Flexural Waves in Elastic Beams by Bending Mode of Graded Resonators

“…To push the operational regime of such systems toward lower frequencies, the exploitation of local resonance has received considerable attention (Liu et al, 2000;Miroshnichenko et al, 2010;Lemoult et al, 2011;Williams et al, 2015), especially for applications in geophysics, mechanical and civil engineering (Colombi et al, 2016a;Miniaci et al, 2016;Achaoui et al, 2017) involving common ambient spectra. While the concept was initially employed for vibration isolation purposes, it was later linked to a variety of phenomena including lensing (Colombi, 2016;Chaplain and Craster, 2019;Fuentes-Domínguez et al, 2021), localisation (Lott et al, 2020) or topological edge states (Pal and Ruzzene, 2017;Xia et al, 2020).…”

“…To capitalize on these recent metamaterial designs, energy harvesting is an attractive application: vibration-based energy harvesting has received considerable attention over the last 2 decades, aiming at powering devices using vibrational energy. A practical example consists in the opportunity to harvest energy from the environment to potentially remove the cost associated with battery replacement and avoid the waste of conventional batteries (Erturk and Elvin, 2013). Among the various possible energy harvesting methods, the ones based on piezoelectric materials are widely used due to their large power densities and ease of application (Anton and Sodano, 2007;Erturk and Inman, 2011).…”

“…A practical example consists in the opportunity to harvest energy from the environment to potentially remove the cost associated with battery replacement and avoid the waste of conventional batteries (Erturk and Elvin, 2013). Among the various possible energy harvesting methods, the ones based on piezoelectric materials are widely used due to their large power densities and ease of application (Anton and Sodano, 2007;Erturk and Inman, 2011). A recent line of work in this context exploits methods to locally concentrate the vibrational energy in the attempt to enhance the efficiency of piezoelectric devices.…”