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 [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.

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Persistent URL dx.doi.org/10.1121/1.3505116, hdl.handle.net/1765/33485
Sijl, J, Overvelde, M, Dollet, B, Garbin, V, de Jong, N, Lohse, D, & Versluis, M. (2011). "Compression-only" behavior: A second-order nonlinear response of ultrasound contrast agent microbubbles. Journal of the Acoustical Society of America, 129(4), 1729–1739. doi:10.1121/1.3505116