Ultrasound homogenises suspensions of hydrophobic particles

Hydrophobic particles inherently resist being suspended. Hydrophobic particles might be regarded as tiny solid particles surrounded by a thin gaseous shell. It has been hypothesised that hydrophobic particles act as cavitation nuclei. This cavitation behaviour would explain the translation speeds observed when hydrophobic polystyrene microspheres were driven through a liquid medium by means of ultrasound.5 These translation speeds corresponded to those observed with gas microbubbles of similar sizes. If hydrophobic particles do have a thin gaseous layer surrounding the solid cores, a sound field of sufficient pressure amplitude might force the gas layer to form and inertial cavity and subsequently fragment during the collapse phase. In this study, we investigated whether hydrophobic particles can be forced to suspend by using ultrasound. Hydrophobic particles of the materials C65 and ZnO can be forced to be suspended in water using ultrasound. The high-speed observations confirm that hydrophobic particles can act as cavitation nuclei. The lack of cavitation after the first pulse indicates that the gas layer surrounding the hydrophobic particle dissolves after inertial cavitation.Comment: 6 pages, 3 figures (7 frames), Submitted to the 39th Symposium on UltraSonic Electronics (USE2019

First-cycle oscillation excursions of Pickering-stabilised microbubbles subjected to a high-amplitude ultrasound pulse

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On the rigidity of four hundred Pickering-stabilised microbubbles

This study explores the rigidity of Pickering-stabilised microbubbles subjected to low-amplitude ultrasound. Such microbubbles might be suitable ultrasound contrast agents. Using an adapted Rayleigh-Plesset equation, we modelled the dynamics of microbubbles with a 7.6-N m-1 shell stiffness under 1-MHz, 0.2-MPa sonication. Such dynamics were observed experimentally, too, using high-speed photography. The maximum expansions were agreeing with those predicted for Pickering-stabilised microbubbles. Subjecting microbubbles to multiple time-delayed pulses yielded the same result. We conclude that Pickering-stabilised microbubbles remain very stable at low acoustic amplitudes.acceptedVersionPeer reviewe

Ultrasound homogenises suspensions of hydrophobic particles

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Acoustic hydrophobic particles

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Asymmetric oscillations of endoskeletal antibubbles

International audienceAntibubbles have been under investigation as potential vehicles in ultrasound-guided drug delivery. It is assumed that antibubbles can expand unhampered, but cannot contract beyond the size of their inner core. In this study, this hypothesis was tested on endoskeletal antibubbles and reference bubbles. These were subjected to 3-cycle pulses of 1-MHz ultrasound, whilst being recorded with a high-speed camera operating at 10 million frames per second. At low acoustic amplitudes (200 kPa), antibubbles and bubbles oscillated symmetrically. At high acoustic amplitudes (1.00 MPa), antibubbles and bubbles oscillated asymmetrically, but antibubbles significantly more so than bubbles. Furthermore, fragmentation and core release were observed at these amplitudes. This finding may have implications for ultrasound-guided drug delivery using antibubbles

Oscillating endoskeletal antibubbles

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