Multi-scale interfaces

In the past few years, we have initiated a multi-scale approach that aims at establishing the link between dynamical processes taking place at the nanoscale and behaviors observed at macroscopic scale.

Our studies seek to  reunify field of physical sciences that are usually disconnected, such as nanosciences and physics of liquids at various scales. Our entry point is the key role of interfaces, which provide an efficient way to couple effects at different scales. Our research themes include:
- super wetting and transport in laminar regime,
- interfacial flows and osmotic,
- large-scale super-hydrophobic surfaces,
- chaotic transport and mixing.

  

 

Members:

Biance, Anne-Laure Colombani, Jean  
Cottin-Bizonne, Cécile
Ehlinger, Quentin
Le Merrer, Marie

Maquet, Laurent     Pirat, Christophe
Ramos-Canut, Stella

Titta, Andrea
Ybert, Christophe

Highlights

 

Drop evaporation on superhydrophobic surfaces

We experimentally study the evaporation of drops on heated superhydrophobic surfaces decorated with micrometer-sized mushroom-like pillars.The drop evaporation appears to be controled by the contact line dynamics. Main results (i) in the pinned regime, the substrate heating promote the contact line depinning; (ii) in the moving regime, the droplet motion is described by periodic stick−slip events and contact-angle oscillations (iii) remarkable stability of the “fakir” state to the temperature.

Water drop evaporation on mushroom-like super-hydrophobic surfaces..., et al., Langmuir (2016)

 

SEM image of a typical investigated sample and snapshots of the top views of an evaporating sessile drop,

 

Topological rearrangement in a soap film assembly

A specific soap film architecture has been designed to study the structure of the freshly formed film during a topological rearrangement. PIV, interferometric and absorption measurements allow to define two distinct mechanisms of soap film generation depending on the physicochemistry of the soap film solution. These results have large impat on the understanding of foam rheology.

On the generation of a soap film during a topological rearrangement, Petit et al., Journal of Fluid Mechanics (2015)

 

 Set up used to mimick a topological rearrangement in a liquid foam.

 

"Cracks" in rigid soap films

We study the influence of the physico-chemistry of surfactants on soap film bursting dynamics, in order to understand its effect on liquid foam stability. With certain type of surfactants, the bursting dynamics deviates from the classical established law, providing a new method to measure the interfacial elasticity of the surfactant solutions. Besides, new "crack" patterns, similar to fractures in a solid membrane, are observed during the liquid film opening.

Holes and cracks in rigid soap films, Petit et al., JFM Rapids (2015).

 

 (a) Soap film withdrawn from a liquid bath. (b) Opening hole in a film of colored soap. A darker i.e. thicker aureole is visible around the hole.(c) Bursting of a rigid soap film with visible « cracks ».

 

Oil transport in a soap film architecture

A specific soap film architecture has been used to study a fluorescent oil globule transport during a topological rearrangement in a soap film assembly. Depending on oil volume fraction, different regimes have been observed, including one where the transport is favored by the rearrangement process. Collaboration with E. Lorenceau IFFSTAR

Oil repartition in a foam film architecture,  Piroird et al., Soft Matter (2014)

 

Different configuration of oil repartition (bright) in a soap film assembly experiencing a topological rearrangement.

 

Drop impacts

We study the dynamics of drops impacting a solid surface. Using experimental tools that provide the local thickness and velocity of the liquid lamella,  we compare impacts at room temperature with impact on a hot surface, where calefaction makes the liquid-substrate fraction negligible. Our approach allow us to evidence a viscous layer in the former case, and a purely convective flow in the latter.

Bridging local to global dynamics of drop impact onto solid substrates, Lastakowski et al., Journal of Fluid Mechanics (2014)

 

Impact  of an ethanol drop on  silicon wafer. (a)  calefaction on a substrate maintained at 350°C, (b)  on a cold substrate.

 

Super-oléophobic surfaces

We study experimentally the properties of oleophobic and super-oleophobic surfaces nanostructured with fractal patterns. In particular, we discuss the stability of the super-oleophobic regime, the mechanism underlying partial impregnation and the non-existence of homogeneous wetting.

 

 Hexadecane  drop on a fractal super-oléophobic surface.

 

Chaotic mixing

We explore the consequences of molecular effects on the macroscopic mixing properties of particles: in chaotic or turbulent flow. Even though diffusion phenomena amounts, ultimately, to mixing between strands generated by the flow, the influence of diffusion - and more generally molecular effects - have never been considered for this kind of phenomena. For the case of co-mixing of particles and a molecular solute (salt), we have shown the coupling mechanism - osmotic in nature - between those two passive tracers, and explore the macroscopic consequences.

Boosting migration of large particles by solute contrasts. Abecassis et al. Nature Materials (2008).

 

 

Schematic of the chaotic mixer used (left) and experimental results for co-mixing of fluorescent particles: cross-section after various number of stretching-folding cycles: no co-solute (saltless), salt co-solute with the particles (saltin), or with the mixing solution (saltout).

 
Scroll To Top