Oscillating phospholipid-coated ultrasound contrast agent microbubbles display a so-called “compression-only” behavior, where it is observed that the bubbles compress efficiently while their expansion is suppressed. Here, a theoretical understanding of the source of this nonlinear behavior is provided through a weakly nonlinear analysis of the shell buckling model proposed by Marmottant et al. [J. Acoust. Soc. Am. 118, 3499–3505 (2005)]. It is shown that the radial dynamics of the bubble can be considered as a superposition of a linear response at the fundamental driving frequency and a second-order nonlinear low-frequency response that describes the negative offset of the mean bubble radius. The analytical solution deduced from the weakly nonlinear analysis shows that the compression-only behavior results from a rapid change of the shell elasticity with bubble radius. In addition, the radial dynamics of single phospholipid-coated microbubbles was recorded as a function of both the amplitude and the frequency of the driving pressure pulse. The comparison between the experimental data and the theory shows that the magnitude of compression-only behavior is mainly determined by the initial phospholipids concentration on the bubble surface, which slightly varies from bubble to bubble.
“Compression-only” behavior: A second-order nonlinear response of ultrasound contrast agent microbubbles
Present address: Institut de Physique de Rennes, UMR 6251 CNRS/Universite de Rennes 1, Campus Beaulieu, Batiment 11A, 35042 Rennes Cedex, France.
Present address: Department of Chemical and Biomolecular Engineering, University of Pennsylvania, 330 South 33rd Street, Philadelphia, PA 19104.
Jeroen Sijl, Marlies Overvelde, Benjamin Dollet, Valeria Garbin, Nico de Jong, Detlef Lohse, Michel Versluis; “Compression-only” behavior: A second-order nonlinear response of ultrasound contrast agent microbubbles. J. Acoust. Soc. Am. 1 April 2011; 129 (4): 1729–1739. https://doi.org/10.1121/1.3505116
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