Final Activity Report Summary - DROPLET DETACHMENT (Droplet detachment by thermal fluctuations)
We have presented experimental evidence that drop breakup is caused by thermal noise in a system with a surface tension that is more than a million times smaller than that of water. We have observed that at very small scales classical hydrodynamics breaks down and the characteristic signatures of pinch-off due to thermal noise are observed. Surprisingly, the noise makes the drop size distribution more uniform, by suppressing the formation of satellite droplets of the smallest sizes. The crossover between deterministic hydrodynamic motion and stochastic thermally driven motion has repercussions for our understanding of small-scale hydrodynamics, important in many problems such as micro- or nanofluidics and interfacial singularities. This was the main goal of the Marie Curie EIF.
Furthermore, we have studied and analysed the effects of shear on the thermal fluctuations in a system similar to the one used in the above work. Strikingly, we found that the shear strongly suppresses capillary waves, making the interface smoother. This phenomenon can be described by introducing an effective interfacial tension that increases with the shear rate. These observations are of fundamental importance.
Finally, we have studied and analysed the influence of thermal fluctuations on the thickness of wetting layers. Here, we have demonstrated for the first time the importance of fluctuations in a system showing complete wetting with short ranged forces.
Furthermore, we have studied and analysed the effects of shear on the thermal fluctuations in a system similar to the one used in the above work. Strikingly, we found that the shear strongly suppresses capillary waves, making the interface smoother. This phenomenon can be described by introducing an effective interfacial tension that increases with the shear rate. These observations are of fundamental importance.
Finally, we have studied and analysed the influence of thermal fluctuations on the thickness of wetting layers. Here, we have demonstrated for the first time the importance of fluctuations in a system showing complete wetting with short ranged forces.