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Published April 20, 2010 | Published + Supplemental Material
Journal Article Open

Generation and control of sound bullets with a nonlinear acoustic lens


Acoustic lenses are employed in a variety of applications, from biomedical imaging and surgery to defense systems and damage detection in materials. Focused acoustic signals, for example, enable ultrasonic transducers to image the interior of the human body. Currently however the performance of acoustic devices is limited by their linear operational envelope, which implies relatively inaccurate focusing and low focal power. Here we show a dramatic focusing effect and the generation of compact acoustic pulses (sound bullets) in solid and fluid media, with energies orders of magnitude greater than previously achievable. This focusing is made possible by a tunable, nonlinear acoustic lens, which consists of ordered arrays of granular chains. The amplitude, size, and location of the sound bullets can be controlled by varying the static precompression of the chains. Theory and numerical simulations demonstrate the focusing effect, and photoelasticity experiments corroborate it. Our nonlinear lens permits a qualitatively new way of generating high-energy acoustic pulses, which may improve imaging capabilities through increased accuracy and signal-to-noise ratios and may lead to more effective nonintrusive scalpels, for example, for cancer treatment.

Additional Information

© 2010 by the National Academy of Sciences. Communicated by L B Freund, Brown University, Providence, RI, February 12, 2010 (received for review October 4, 2009). Published online before print April 5, 2010. The authors thank Vitali F. Nesterenko for initial discussions, Tapio Schneider for helpful suggestions, and Veronica Eliasson for valuable experimental insight. Funding from the Army Research Office (Grant 54272-EG) and National Science Foundation (Materials Research Science and Engineering Center at the California Institute of Technology and NSF-CMMI-0806762-CAREER) is also acknowledged. Author contributions: C.D. designed research; A.S. performed research; A.S. and C.D. analyzed data; and A.S. and C.D. wrote the paper. The authors declare no conflict of interest. This article contains supporting information online at www.pnas.org/cgi/content/full/1001514107/DCSupplemental.

Attached Files

Published - Spadoni2010p9957P_Natl_Acad_Sci_Usa.pdf

Supplemental Material - SM1.avi

Supplemental Material - pnas.1001514107_SI.pdf


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