Many efforts have been devoted to the design and achievement of negative-refractive-index metamaterials since the 2000s1,2,3,4,5,6,7,8. One of the challenges at present is to extend that field beyond electromagnetism by realizing three-dimensional (3D) media with negative acoustic indices9. We report a new class of locally resonant ultrasonic metafluids consisting of a concentrated suspension of macroporous microbeads engineered using soft-matter techniques. The propagation of Gaussian pulses within these random distributions of ‘ultra-slow’ Mie resonators is investigated through in situ ultrasonic experiments. The real part of the acoustic index is shown to be negative (up to almost − 1) over broad frequency bandwidths, depending on the volume fraction of the microbeads as predicted by multiple-scattering calculations. These soft 3D acoustic metamaterials open the way for key applications such as sub-wavelength imaging and transformation acoustics, which require the production of acoustic devices with negative or zero-valued indices.
Subscribe to Journal
Get full journal access for 1 year
only $17.42 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
Krowne, C. M. & Zong, Y. (eds) Physics of Negative Refraction and Negative Index Materials (Springer, 2007).
Cubukcu, E. et al. Electromagnetic waves: Negative refraction by photonic crystals. Nature 423, 604–605 (2003).
Martinez-Sala, R. et al. Sound attenuation by sculpture. Nature 378, 241 (1995).
Shelby, R. A., Smith, D. R. & Schultz, S. Experimental verification of a negative index of refraction. Science 292, 77–79 (2001).
Zhang, S. et al. Experimental demonstration of near-infrared negative-index metamaterials. Phys. Rev. Lett. 95, 137404 (2005).
Dolling, G. et al. Simultaneous negative phase and group velocity of light in a metamaterial. Science 312, 892–894 (2006).
Soukoulis, C. M. & Wegener, M. Past achievements and future challenges in the development of three-dimensional photonic metamaterials. Nature Photon. 5, 523–530 (2011).
Smith, D. R., Pendry, J. B. & Wiltshire, M. C. K. Metamaterials and negative refractive index. Science 305, 788–792 (2004).
Wegener, M. Metamaterials beyond optics. Science 342, 939–940 (2013).
Liu, Z. Y. et al. Locally resonant sonic materials. Science 289, 1734–1736 (2000).
Lee, S. et al. Composite acoustic medium with simultaneously negative density and modulus. Phys. Rev. Lett. 104, 054301 (2010).
Fok, L. & Zhang, X. Negative acoustic index metamaterial. Phys. Rev. B 83, 214304 (2011).
Liang, Z. & Li, J. Extreme acoustic metamaterial by coiling up space. Phys. Rev. Lett. 108, 114301 (2012).
Xie, Y. et al. Measurement of a broadband negative index with space-coiling acoustic metamaterials. Phys. Rev. Lett. 110, 175501 (2013).
Pendry, J. B. Negative refraction makes a perfect lens. Phys. Rev. Lett. 85, 3966–3999 (2000).
Kadic, M. et al. Metamaterials beyond electromagnetism. Rep. Prog. Phys. 76, 126501 (2013).
Fang, N. et al. Ultrasonic metamaterials with negative modulus. Nature Mater. 5, 452–456 (2006).
Li, J. et al. Experimental demonstration of an acoustic magnifying hyperlens. Nature Mater. 8, 931–934 (2009).
Brunet, T., Leng, J. & Mondain-Monval, O. Soft acoustic metamaterials. Science 342, 323–324 (2013).
Pendry, J. B. & Li, J. An acoustic metafluid: Realizing a broadband acoustic cloak. New J. Phys. 10, 115032 (2008).
Norris, A. N. Acoustic metafluids. J. Acoust. Soc. Am. 125, 839–849 (2009).
Seeman, R. et al. Droplet based microfluidics. Rep. Prog. Phys. 75, 016601 (2012).
Brunet, T. et al. Tuning Mie scattering resonances in soft materials with magnetic fields. Phys. Rev. Lett. 111, 264301 (2013).
Li, J. & Chan, C. T. Double-negative acoustic metamaterial. Phys. Rev. E 70, 055602 (2004).
Still, T. et al. Soft silicone rubber in phononic structures: Correct elastic moduli. Phys. Rev. B 88, 094102 (2013).
Allard, J-F. Propagation of Sound in Porous Media (Springer, 1993).
Bretagne, A., Tourin, A. & Leroy, V. Enhanced and reduced transmission of acoustic waves with bubble meta-screens. Appl. Phys. Lett. 99, 221906 (2011).
Dubois, J., Aristégui, C. & Poncelet, O. Spaces of electromagnetic and mechanical constitutive parameters for dissipative media with either positive or negative index. J. Appl. Phys. 115, 024902 (2014).
Gokmen, M. & Du Prez, F. Porous polymer particles - A comprehensive guide to synthesis, characterization, functionalization and applications. Prog. Polym. Sci. 37, 365–405 (2012).
Brunet, T. et al. Sharp acoustic multipolar-resonances in highly monodisperse emulsions. Appl. Phys. Lett. 101, 011913 (2012).
Leroy, V. et al. Sound velocity and attenuation in bubbly gels measured by transmission experiments. J. Acoust. Soc. Am. 123, 1931–1940 (2008).
Page, J. H. et al. Group velocity in strongly scattering media. Science 271, 634–637 (1996).
Waterman, P. C. & Truell, R. Multiple scattering of waves. J. Math. Phys. 2, 512–537 (1961).
This work was supported by the Agence Nationale pour la Recherche (Grant 2011-BS0902101 Metakoustik-Aerospace Valley) and the US Air Force European Office of Aerospace Research and Development (Grant FA8655-12-1-2067). This work was performed under the auspices of the Labex AMADEUS ANR-10-LABX-0042-AMADEUS with the help of French state Initiative d’Excellence IdEx ANR-10-IDEX-003-02. We thank G. Pibre from Bluestar Silicones for fruitful advice and providing us with the silicone rubber, and J. Valencony (Siltech Corp.) for the surfactants.
The authors declare no competing financial interests.
About this article
Cite this article
Brunet, T., Merlin, A., Mascaro, B. et al. Soft 3D acoustic metamaterial with negative index. Nature Mater 14, 384–388 (2015). https://doi.org/10.1038/nmat4164
Negative index metamaterial through multi-wave interactions: numerical proof of the concept of low-frequency Lamb-wave multiplexing
Scientific Reports (2021)
Advanced Engineering Materials (2021)
Design and Fabrication of Negative-Refractive-Index Metamaterial Unit Cells for Near-Megahertz Enhanced Acoustic Transmission in Biomedical Ultrasound Applications
Physical Review Applied (2021)
Physical Review Letters (2021)
Frequency-dependent analysis of ultrasound apparent absorption coefficient in multiple scattering porous media: application to cortical bone
Physics in Medicine & Biology (2021)