Negative refraction and energy funneling by hyperbolic materials: An experimental demonstration in acoustics

This Letter reports the design, fabrication, and experimental characterization of hyperbolic materials showing negative refraction and energy funneling of airborne sound. Negative refraction is demonstrated using a stack of five holey Plexiglas plates where their thicknesses, layer separation, hole diameters, and lattice periodicity have been determined to show hyperbolic dispersion around 40 kHz. The resulting hyperbolic material shows a flat band profile in the equifrequency contour allowing the gathering of acoustic energy in a broad range of incident angles and its funneling through the material. Our demonstrations foresee interesting developments based on both phenomena. Acoustic imaging with subwavelength resolution and spot-size converters that harvest and squeeze sound waves irradiating from many directions into a collimated beam are just two possible applications among many.This work was partially supported by the Office of Naval Research (USA) under Grant No. N000140910554, and by the Ministerio de Economia y Competitividad (Spain) under Contract No. TEC2010-19751. J. C. gratefully acknowledges financial support from the Danish Council for Independent Research and a Sapere Aude Grant (12-134776).García Chocano, VM.; Christensen, J.; Sánchez-Dehesa Moreno-Cid, J. (2014). Negative refraction and energy funneling by hyperbolic materials : an experimental demonstration in acoustics. Physical Review Letters. 112(14). https://doi.org/10.1103/PhysRevLett.112.144301S1121

Acoustic metamaterial absorbers based on multilayered sonic crystals

Through the use of a layered arrangement, it is shown that lossy sonic crystals can be arranged to create a structure with extreme acoustic properties, namely, an acoustic metamaterial. This artificial structure shows different effective fluids and absorptive properties in different orientations. Theoretical, numerical, and experimental results examining thermoviscous losses in sonic crystals are presented, enabling the fabrication and characterization of an acoustic metamaterial absorber with complex-valued anisotropic inertia. To accurately describe and fabricate such an acoustic metamaterial in a realizable experimental configuration, confining structures are needed which modify the effective properties, due to the thermal and viscous boundary layer effects within the sonic crystal lattice. Theoretical formulations are presented which describe the effects of these confined sonic crystals, both individually and as part of an acoustic metamaterial structure. Experimental demonstrations are also reported using an acoustic impedance tube. The formulations developed can be written with no unknown or empirical coefficients, due to the structured lattice of the sonic crystals and organized layering scheme; and it is shown that higher filling fraction arrangements can be used to provide a large enhancement in the loss factor. (C) 2015 AIP Publishing LLC.This work was supported by the U.S. Office of Naval Research (Award No. N000141210216) and by the Spanish Ministerio de Economia y Competitividad (MINECO) under Contract No. TEC2010-19751.Guild, M.; García Chocano, VM.; Kan, W.; Sánchez-Dehesa Moreno-Cid, J. (2015). Acoustic metamaterial absorbers based on multilayered sonic crystals. Journal of Applied Physics. 117(11):114902-1-114902-14. https://doi.org/10.1063/1.4915346S114902-1114902-1411711Dowling, J. P. (1992). Sonic band structure in fluids with periodic density variations. 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New Journal of Physics, 10(11), 115032. doi:10.1088/1367-2630/10/11/115032Popa, B.-I., & Cummer, S. A. (2009). Design and characterization of broadband acoustic composite metamaterials. Physical Review B, 80(17). doi:10.1103/physrevb.80.174303Torrent, D., & Sánchez-Dehesa, J. (2010). Anisotropic Mass Density by Radially Periodic Fluid Structures. Physical Review Letters, 105(17). doi:10.1103/physrevlett.105.174301Gumen, L. N., Arriaga, J., & Krokhin, A. A. (2011). Metafluid with anisotropic dynamic mass. Low Temperature Physics, 37(11), 975-978. doi:10.1063/1.3672821Zigoneanu, L., Popa, B.-I., Starr, A. F., & Cummer, S. A. (2011). Design and measurements of a broadband two-dimensional acoustic metamaterial with anisotropic effective mass density. Journal of Applied Physics, 109(5), 054906. doi:10.1063/1.3552990Reyes-Ayona, E., Torrent, D., & Sánchez-Dehesa, J. (2012). Homogenization theory for periodic distributions of elastic cylinders embedded in a viscous fluid. The Journal of the Acoustical Society of America, 132(4), 2896-2908. doi:10.1121/1.4744933Naify, C. J., Chang, C.-M., McKnight, G., & Nutt, S. (2010). Transmission loss and dynamic response of membrane-type locally resonant acoustic metamaterials. Journal of Applied Physics, 108(11), 114905. doi:10.1063/1.3514082Yang, Z., Dai, H. M., Chan, N. H., Ma, G. C., & Sheng, P. (2010). Acoustic metamaterial panels for sound attenuation in the 50–1000 Hz regime. Applied Physics Letters, 96(4), 041906. doi:10.1063/1.3299007Naify, C. J., Chang, C.-M., McKnight, G., Scheulen, F., & Nutt, S. (2011). Membrane-type metamaterials: Transmission loss of multi-celled arrays. Journal of Applied Physics, 109(10), 104902. doi:10.1063/1.3583656Hussein, M. I., & Frazier, M. J. (2013). Metadamping: An emergent phenomenon in dissipative metamaterials. Journal of Sound and Vibration, 332(20), 4767-4774. doi:10.1016/j.jsv.2013.04.041Zhang, Y., Wen, J., Zhao, H., Yu, D., Cai, L., & Wen, X. (2013). Sound insulation property of membrane-type acoustic metamaterials carrying different masses at adjacent cells. Journal of Applied Physics, 114(6), 063515. doi:10.1063/1.4818435Manimala, J. M., & Sun, C. T. (2014). Microstructural design studies for locally dissipative acoustic metamaterials. Journal of Applied Physics, 115(2), 023518. doi:10.1063/1.4861632Oudich, M., Zhou, X., & Badreddine Assouar, M. (2014). General analytical approach for sound transmission loss analysis through a thick metamaterial plate. Journal of Applied Physics, 116(19), 193509. doi:10.1063/1.4901997Christensen, J., Romero-García, V., Picó, R., Cebrecos, A., de Abajo, F. J. G., Mortensen, N. A., … Sánchez-Morcillo, V. J. (2014). Extraordinary absorption of sound in porous lamella-crystals. Scientific Reports, 4(1). doi:10.1038/srep04674Sánchez-Dehesa, J., Garcia-Chocano, V. M., Torrent, D., Cervera, F., Cabrera, S., & Simon, F. (2011). Noise control by sonic crystal barriers made of recycled materials. 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Redirection of sound in straight fluid channel with elastic boundaries

A fluid channel clad between two solid plates is an acoustic waveguide where excitation of elastic waves at the channel boundaries has been usually neglected. This work develops a rigorous theory of scattering of sound by a finite-length fluid channel which takes into account excitation of elastic eigenmodes of two plates acoustically coupled through a fluid channel. The theory predicts an evidently contradictory result that the transmission and reflection coefficients of a nondissipative channel do not sum up to one. Moreover, they both exhibit deep minima at the same series of frequencies. It is shown that conservation of acoustic energy occurs due to redirection of sound, since part of the acoustic flux escapes into the solid plates. This scattering becomes possible because the uniform flatness of the boundaries of a straight channel is broken by vibrations. Theoretical predictions are supported by the experiments with ultrasound transmission through a narrow slit obtained between two brass or aluminum plates submerged in water. Measured transmission spectra exhibit deep minima exactly at the frequencies where the theory predicts strong redirection of sound.This study is supported by the Office of Naval Research (USA) under Contract No. N00014-12-1-0216. A.K. acknowledges support from the program "Plan de Movilidad e Internalizacion Academica VLC/CAMPUS."Bozhko, A.; Garcia Chocano, VM.; Sánchez-Dehesa Moreno-Cid, J.; Krokhin, A. (2015). Redirection of sound in straight fluid channel with elastic boundaries. Physical review B: Condensed matter and materials physics. 91(9):094303-094303. doi:10.1103/PhysRevB.91.094303S09430309430391

RICORS2040 : The need for collaborative research in chronic kidney disease

Chronic kidney disease (CKD) is a silent and poorly known killer. The current concept of CKD is relatively young and uptake by the public, physicians and health authorities is not widespread. Physicians still confuse CKD with chronic kidney insufficiency or failure. For the wider public and health authorities, CKD evokes kidney replacement therapy (KRT). In Spain, the prevalence of KRT is 0.13%. Thus health authorities may consider CKD a non-issue: very few persons eventually need KRT and, for those in whom kidneys fail, the problem is 'solved' by dialysis or kidney transplantation. However, KRT is the tip of the iceberg in the burden of CKD. The main burden of CKD is accelerated ageing and premature death. The cut-off points for kidney function and kidney damage indexes that define CKD also mark an increased risk for all-cause premature death. CKD is the most prevalent risk factor for lethal coronavirus disease 2019 (COVID-19) and the factor that most increases the risk of death in COVID-19, after old age. Men and women undergoing KRT still have an annual mortality that is 10- to 100-fold higher than similar-age peers, and life expectancy is shortened by ~40 years for young persons on dialysis and by 15 years for young persons with a functioning kidney graft. CKD is expected to become the fifth greatest global cause of death by 2040 and the second greatest cause of death in Spain before the end of the century, a time when one in four Spaniards will have CKD. However, by 2022, CKD will become the only top-15 global predicted cause of death that is not supported by a dedicated well-funded Centres for Biomedical Research (CIBER) network structure in Spain. Realizing the underestimation of the CKD burden of disease by health authorities, the Decade of the Kidney initiative for 2020-2030 was launched by the American Association of Kidney Patients and the European Kidney Health Alliance. Leading Spanish kidney researchers grouped in the kidney collaborative research network Red de Investigación Renal have now applied for the Redes de Investigación Cooperativa Orientadas a Resultados en Salud (RICORS) call for collaborative research in Spain with the support of the Spanish Society of Nephrology, Federación Nacional de Asociaciones para la Lucha Contra las Enfermedades del Riñón and ONT: RICORS2040 aims to prevent the dire predictions for the global 2040 burden of CKD from becoming true

Resonant excitation of coupled Rayleigh waves in a short and narrow fluid channel clad between two identical metal plates

Transmission of ultrasonic waves through a slit between two water immersed brass plates is studied for sub-wavelength plate thicknesses and slit apertures. Extraordinary high absorption is observed at discrete frequencies corresponding to resonant excitation of Rayleigh waves on the both sides of the channel. The coupling of the Rayleigh waves occurs through the fluid and the corresponding contribution to the dispersion has been theoretically derived and also experimentally confirmed. Symmetric and anti-symmetric modes are predicted but only the symmetric mode resonances have been observed. It follows from the dispersion equation that the coupled Rayleigh waves cannot be excited in a channel with apertures less than the critical one. The calculated critical aperture is in a good agreement with the measured acoustic spectra. These findings could be applied to design a broadband absorptive metamaterial