When a soft mattress levitates the sleeper…
In a recent work, researchers show that particles entrained in a flow close to a deformable wall undergo a force that moves them slightly away from it, an important result for the general understanding of transport phenomena in biology.
References
H.Zhang, Z. Zhang A. Jha, Y.Amarouchene, T.Salez, T. Guérin, C. Misbah, and A. Maali, Direct Measurement of the Viscocapillary Lift Force near a Liquid Interface, Phys. Rev. Lett. 134, 094001,(2025) –Publié le 7 mars 2025
DOI :10.1103/PhysRevLett.134.094001
Open-access archive : arXiv
Thirty years ago, it was predicted that an emergent lift force would act on an object moving in a viscous fluid close to an interface if the interface or the object were soft and deformable. This force, resulting from the interaction between the viscous flow and the deformation of the interface, would push the object away from the interface and thus reduce the possibility of contact interaction between them. This counter-intuitive interaction is not only an academic curiosity, as most flows in living organisms involve liquids flowing in biological membranes, which are by nature deformable.
This research was carried out in the following CNRS laboratories:
- Laboratoire Ondes et Matière d'Aquitaine (LOMA, CNRS/Université de Bordeaux)
- Laboratoire interdisciplinaire de physique (LIPhy, CNRS / Université Grenoble Alpes)
Experiments carried out at the Laboratoire Ondes et Matière d'Aquitaine have made it possible for the first time to directly measure the lift force acting on a particle moving along the deformable interface separating two liquids. Using a sensitive device called an atomic force microscope (AFM), the lift force was probed as a function of key system parameters such as distance to the interface, particle size, velocity and liquid viscosity. The experimental results reveal that the lift force increases as the particle approaches the liquid-liquid interface, and saturates at very small distances. The experimental measurements show good agreement with theoretical predictions and numerical simulations.
This work is important for understanding particle dynamics near fluid interfaces and could have an impact on fields such as micro-fluidics, the behavior of biological cells in confined environments and self-propelled objects near liquid interfaces. The results of this study are published in the Physical Review Letters.
