Marangoni propulsion and interaction with flows
Where : Institut Lumière Matière, Lyon, team Liquides et Interfaces, UMR 5306
Contact : Cécile Cottin-Bizonne,
cecile.cottin-bizonne@univ-lyon1.fr
François Detcheverry,
francois.detcheverry@univ-lyon1.fr
Christophe Ybert, Christophe Ybert,
christophe.ybert@univ-lyon1.fr
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 where their behavior
was shown to motivate a host of questions, from their individual propulsion to striking collective properties
such as active turbulence.
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 swimmer 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 and simulations 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, if funding obtained by the student from école doctorale”