Marangoni propulsion and interaction with flows
The presence of surfactant such as amphiphilic molecules at the air-water interface may locally alter
the surface tension and induce a flow in the underlying water, as exemplified in the celebrated tears of wine
phenomenon. Such Marangoni effects have a long history - with early observation dating back to 1557- but
their study has received a new impetus with the current interest in active matter. Indeed, they can be
exploited to design “
Marangoni swimmers”: macroscopic particles without moving parts that spontaneously
self-propel at the surface of water. Such swimmers have been developed in our team [1] where
their behavior was shown to motivate a host of questions, from their individual propulsion to striking
collective properties such as active turbulence [2].
Having recently characterized the propulsion mechanism at an individual scale and in the presence
of a simple external flow, the goal is now to study
the interactions between two swimmers. To do so, we
will leverage the techniques we have developed for characterizing both the flows and forces, using PIV
(Particle Image Velocimetry) and a cantilever force sensor. We will examine the forces and flows that develop around a pair of swimmers. We will also investigate the interactions of a swimmers with a wall.
In the long term, we will seek to understand how the transport of an interfacial swimmer is affected
by a
complex external flow. By placing a swimmer in a vortex network, we will study, both experimentally
and numerically, the interaction between the swimmer and the flow on the scale of a vortex. This study will
also unveil the resulting large-scale transport properties of the swimmer, a complex situation that involves
many couplings.
The student will combine experimental investigation with exploration of simplified models to develop a clear physical understanding. This topic lies at the confluence of
soft matter, fluid mechanics and
statistical physics.
Opening toward a PhD: yes (funding with «bourse ministère»).
Contact:
Cécile Cottin-Bizonne (
cecile.cottin-bizonne@univ-lyon1.fr)
François Detcheverry (
francois.detcheverry@univ-lyon1.fr)
Christophe Ybert (
christophe.ybert@univ-lyon1.fr)
Team
Liquides et Interfaces, Institut Lumière Matière, Lyon
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References
[1] Self-propulsion of symmetric chemically active particles: Point-source model and experiments on camphor disks
Boniface, Cottin-Bizonne, Kervil, Ybert and Detcheverry, Physical Review E (2019).
[2] Kolmogorovian active turbulence of a sparse assembly of interacting Marangoni surfers,
Bourgoin, Kervil, Cottin-Bizonne, Raynal, Volk and Ybert, Physical Review X (2019).
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