Different experimental patterns of microstreaming observed around acoustically excited microbubbles

HAL Id: hal-02445059

https://hal.archives-ouvertes.fr/hal-02445059

Submitted on 19 Jan 2020

HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.

L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Different experimental patterns of microstreaming observed around acoustically excited microbubbles

Sarah Cleve, Gabriel Regnault, Cyril Mauger, Claude Inserra, Philippe Blanc-Benon

To cite this version:

Sarah Cleve, Gabriel Regnault, Cyril Mauger, Claude Inserra, Philippe Blanc-Benon. Different experi-

mental patterns of microstreaming observed around acoustically excited microbubbles. 25th European

symposium on Ultrasound Contrast Imaging, Jan 2020, Rotterdam, Netherlands. �hal-02445059�

The 25 ^th European symposium on Ultrasound Contrast Imaging

Different experimental patterns of microstreaming observed around acoustically excited microbubbles

Sarah Cleve

, Gabriel Regnault

, Cyril Mauger

, Claude Inserra

, Philippe Blanc-Benon

1

Univ Lyon, École Centrale de Lyon, INSA de Lyon, CNRS, LMFA UMR 5509, F-69134 Écully CEDEX, France

2

Univ Lyon, Université Lyon 1, Centre Léon Bérard, INSERM, LabTAU, F-69003 Lyon, France

*

now at: Physics of Fluids group, MESA+ Institute for Nanotechnology and Technical Medical (TechMed) Center, University of Twente, P.O. Box 217, 7500 AE, Enschede, The Netherlands

Corresponding author: [email protected]

Introduction

The use of bubbles in combination with ultrasound is known to significantly enhance both, the imaging contrast and the efficacy of therapeutic approaches such as sonoporation and blood-brain-barrier opening. Both, inertially cavitating and stably oscillating bubbles can cause these effects [1,2]. Stably oscillating bubbles are argued to be more controllable [3] and to lead to more repairable sonoporation. In this context, the microstreaming generated around acoustically excited bubbles and the subsequent shear stress induced to the cell membranes are assumed to play a major role. The exact mechanisms are, however, not yet fully understood. In particular, there have been little fundamental studies on the streaming patterns that also take into account the detailed temporal bubble dynamics or bubble deformations (in particular surface modes). Here, we show the different microstreaming patterns arising around a single microbubble and successfully correlate them to the microbubble dynamics on the timescales of the oscillations. To ensure the free-field behaviour, we acoustically trap the bubble far from any solid boundary. We drive the bubbles into stable, non-inertial oscillations, and tune the acoustic pressure and the bubble size to trigger specific surface modes. The method provides direct insight into the role of the surface modes in the generated streaming patterns.

Methods

Experiments were conducted in a cubic water tank in which a standing wave is generated by an ultrasound transducer driven at 31 kHz. The ultrasound field allows to simultaneously trap the bubble at a pressure antinode and to drive its radial oscillations. We then ‘trigger’ surface modes by inducing the coalescence of two bubbles of chosen size at a specific acoustic pressure [4]. The bubble dynamics is recorded using a high speed camera, and the fluid motion around the bubble is imaged in fluorescence by means of tracer particles passing through a laser sheet (see example in Figure 1). The combined approach allows to correlate liquid flow, velocity field and bubble dynamics [5].

Results

A large collection of streaming patterns was observed [5]. In particular, we can classify two classes of streaming patterns with a different outreach: (i) patterns consisting of multiple lobes closely confined around the bubble and (ii) cross-shaped patterns leading to streaming further away from the bubble. From the direct correlation with the bubble dynamics, we can identify parameters linked to the exact shape of the streaming patterns. As expected, different mode numbers will lead to different streaming patterns, but a further distinction between large patterns and lobe-shaped patterns can be achieved through the bubble size (relating to the resonance of the shape modes). Furthermore, a closer look on the modal analysis reveals differences in the amplitudes and phase behavior of the modal content. A recent theoretical approach [6,7] supports many of our experimental observations.

1

The 25 ^th European symposium on Ultrasound Contrast Imaging

Discussion

Even though in the clinical application of ultrasound contrast agents, the microbubbles are exposed to a more complicated environment, the present findings are a first step towards understanding the exact role of microstreaming in applications such as sonoporation. In particular, the size of the streaming patterns is interesting to take into account. Furthermore, from the measured velocity fields, it is possible to directly deduce the induced shear stress acting on membranes and cells.

Conclusion

We show for the first time a detailed study on different streaming patterns that are induced by acoustically trapped bubbles oscillating on surface modes. A large variety of patterns is observed for which a first classification according to mode numbers and bubble sizes (relating to the resonance of the shape modes) is possible.

Acknowledgements

This work was performed within the framework of the Labex CeLyA of the Université de Lyon, within the programme ‘Investissements d’Avenir’ (ANR-10-LABX-0060/ANR-11-IDEX-0007) operated by the French National Research Agency (ANR).

Figure 1. Upper left: Snapshot series of a bubble of about 53 μm radius oscillating on a surface mode 4; lm radius oscillating on a surface mode 4; lower left: temporal evolution of the radial mode and the mode 4 with respect to the time (expressed in acoustic periods T=0.032ms); right: the resulting microstreaming (visualization of the particle trajectories by streak photography, that means superposition of all images taken during 1 s of recording is shown, the bubble is

visible in the center).

References

[1]. Lentacker I, De Cock I, Deckers R, De Smedt S, Moonen C, Understanding ultrasound induced sonoporation:

definitions and underlying mechanisms, Advanced drug delivery reviews, 72, 49–64, 2014.

[2]. Kooiman K, Vos HJ, Versluis M, de Jong N, Acoustic behavior of microbubbles and implications for drug delivery, Advanced Drug Delivery Reviews, 72, 28-48, 2014.

[3]. Marmottant P, Hilgenfeldt S, Controlled vesicle deformation and lysis by single oscillating bubbles, Nature 423.6936,153–156, 2003.

[4]. Cleve S, Guédra M, Mauger C, Inserra C, Blanc-Benon P, Surface modes with controlled axisymmetry triggered by bubble coalescence in a high-amplitude acoustic field, Physical Review E , 98, 033115 2018.

[5]. Cleve S, Guédra M, Mauger C, Inserra C, Blanc-Benon P, Microstreaming induced by acoustically trapped, non- spherically oscillating microbubbles, Journal of Fluid Mechanics, 875, 597-621, 2019.

[6]. Doinikov AA, Cleve S, Regnault G, Mauger C, Inserra C, Acoustic microstreaming produced by nonspherical oscillations of a gas bubble. I. Case of modes 0 and m, Physical Review E, 100, 033104, 2019.

[7]. Doinikov AA, Cleve S, Regnault G, Mauger C, Inserra C, Acoustic microstreaming produced by nonspherical oscillations of a gas bubble. II. Case of modes 1 and m, Physical Review E, 100, 033105, 2019.

2