Using Bubble Dynamics to Locally Probe and Restructure Soft Materials
| When |
Jul 19, 2022
from 11:00 to 12:00 |
|---|---|
| Where | Salle des thèses |
| Attendees |
Brice Saint-Michel |
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Bubbles inclusions are intentionally added or naturally present in many complex fluids and soft materials. They reduce the carbon footprint and improve the thermal insulation performances of concrete, and confer ice-creams a smoother, lighter texture. Yet, in contrast with solid particles, bubbles are not entirely passive in their environment: small bubbles (100 µm) both dissolve [1] and react to acoustic excitation by undergoing volumetric oscillations [2]. The resonance parameters of such oscillations depend on the bubble environment [3], whereas multiple bubbles precisely arranged in soft matrices confer them remarkable acoustic metamaterial properties [4].
While many of these phenomena have been investigated in standard hydrogels (agar, gelatin), they have only been marginally investigated in yield-stress fluids. In theory, the interplay between bubble dynamics and the yield stress indeed leads to rich physics: dissolution may or may not be arrested depending on the matrix properties [5]; bubble oscillation dynamics could be used as high-frequency rheological probes across the yielding transition, and they could also trigger their release from such fluids [6]. Material properties may also be probed using acoustic radiation forces. Lastly, considering the large strain applied by dissolution and volumetric oscillations, bubbles could be used to locally rearrange the surrounding matrix.
In this presentation, we examine the bubble dynamics in yield-stress fluids, both theoretically and through experiments. We compare the theoretical predictions to experiments conducted using conventional and high-speed microscopy in a standard Carbopol microgel and confocal microscopy in an attractive, model colloidal gel [7,8]. We finally conclude on the potential of using bubbles as local probes of yield-stress fluids.
[1] P. S. Epstein, P. S. and M. S. Plesset, J. Chem. Phys. 18(11), 1505-1509 (1950)
[2] T. J. Leighton, The Acoustic Bubble, Academic Press (1997)
[3] A. Jamburidze et al., Soft Matt. 13 (21), 3946-3953 (2017)
[4] V. Leroy et al., Phys. Rev. B. 91, 020301 (2015)
[5] B. Saint-Michel and V. Garbin, Curr. Opin. Colloid. Interf. Sci. 50, 101392 (2020)
[6] M. de Corato et al., Phys. Rev. Fluids 4, 073301 (2019)
[7] B. Saint-Michel and V. Garbin, Soft Matt. 18, 10405-10418 (2020)
[8] B. Saint-Michel, G. Petekidis and V. Garbin, Soft Matt. 18, 2092-2103 (2022)