arXiv subjects

Anaïs Gauthier

Publications and source records attributed to Anaïs Gauthier.

5 recordsLinked to original sources

arXiv2026

Long distance attraction between particles in a soap film

Millimeter-sized particles trapped at the surface of a liquid bath attract each other through the deformation of the liquid-air interface, a phenomenon known as "the Cheerios effect". We consider here a situation similar at first sight: the interaction between two millimeter-sized particles trapped in an horizontal soap film. In this geometry, the deformation of the film due to the weight of one particle extends over the entire system size, which induces an extremely long-ranged attraction. Combined with the low viscous friction in the film, this leads to intricate particle orbits, lasting up to ten seconds before the two particles eventually collide. By tracking the particles dynamics, we measure the force exerted by each particle on the other, and we develop a theoretical model. Because the interface deformation induced by a particle depends on its position in the soap film, the attractive force has two features that fundamentally depart from classical interaction forces. The force exerted by one particle on the other differs both in direction and magnitude from the reverse interaction, with an asymmetry reaching 150% when one particle is close to the center and the other one close to the frame. Reciprocity is recovered when both particles are close to the film center. These results are a original example of non-reciprocal effective interactions due to boundary conditions.

cond-mat.soft↗

arXiv2025

Sliding dynamics of a particle in a soap film

We investigate the sliding dynamics of a millimeter-sized particle trapped in a horizontal soap film. Once released, the particle moves toward the center of the film in damped oscillations. We study experimentally and model the forces acting on the particle, and evidence the key role of the mass of the film on its shape and particle dynamics. Not only is the gravitational distortion of the film measurable, it completely determines the force responsible for the motion of the particle - the catenoid-like deformation induced by the particle has negligible effect on the dynamics. Surprisingly, this is expected for all film sizes as long as the particle radius remains much smaller than the film width. We also measure the friction force, and show that ambient air and the film contribute almost equally to the friction. The theoretical model that we propose predicts exactly the friction coefficient as long as inertial effects can be neglected in air (for the smallest and slowest particles). The fit between theory and experiments sets an upper boundary of 0.01 μPa s m for the surface viscosity, in excellent agreement with recent interfacial microrheology measurements.

cond-mat.soft↗

arXiv2024

Line tension in a thick soap film

The thickness of freshly made soap films is usually in the micron range, and interference colors make thickness fluctuations easily visible. Circular patterns of constant thickness are commonly observed, either a thin film disc in a thicker film or the reverse. In this Letter, we evidence the line tension at the origin of these circular patterns. Using a well controlled soap film preparation, we produce a piece of thin film surrounded by a thicker film. The thickness profile, measured with a spectral camera, leads to a line tension of the order of 0.1 nN which drives the relaxation of the thin film shape, initially very elongated, toward a circular shape.A balance between line tension and air friction leads to a quantitative prediction of the relaxation process. Such a line tension is expected to play a role in the production of marginal regeneration patches, involved in soap film drainage and stability.

cond-mat.soft↗

arXiv2021

Total-internal-reflection deflectometry for measuring small deflections of a fluid surface

We describe a method that uses total internal reflection at the water-air interface inside a large, transparent tank, to measure the interface's deflections. Using this configuration, we obtain an optical set-up where the liquid surface acts as a deformable mirror. The set-up is shown to be extremely sensitive to very small disturbances of the reflecting water surface, which are detected by means of visualising the reflections of a reference pattern. When the water surface is deformed, it reflects a distorted image of the reference pattern, similar to a synthetic Schlieren set-up. The distortions of the pattern are analysed using a suitable image correlation method. The displacement fields thus obtained correlate to the local spatial gradients of the water surface. The gradient fields are integrated in a least-squares sense to obtain a full instantaneous reconstruction of the water surface. This method is particularly useful when a solid object is placed just above water surface, whose presence makes the liquid surface otherwise optically inaccessible.

physics.flu-dyn↗

arXiv2019

Inverse Leidenfrost drop manipulation using menisci

Drops deposited on an evaporating liquid bath can be maintained in an inverse Leidenfrost state by the vapor emanating from the bath, making them levitate and hover almost without friction. These perfectly non-wetting droplets create a depression in the liquid interface that sustains their weight, which generates repellent forces when they approach a meniscus rising against a wall. Here, we study this reflection in detail, and show that frictionless Leidenfrost drops are a simple and efficient tool to probe the shape of an unknown interface. We then use the menisci to control the motion of the otherwise elusive drops. We create waveguides to direct and accelerate them and use parabolic walls to reflect and focus them. This could be particularly beneficial in the scale up of droplet cryopreservation processes: capillary interactions can be used to transport, gather and collect vitrified biological samples in absence of contact and contamination.

physics.flu-dyn↗