The impact of ordinary raindrops on a solid surface can have deleterious effects and induce erosion of fragile solid such as soils [1] but also alteration of the surface optical properties [2] or even degradation of plant leaves [3].

Yet, at first glance, one would think that the liquid would absorb all the deformation resulting from the impact on a surface as stiff as glass or silicon, thus exerting a moderate stress and leaving the surface unharmed. However, during impact, the forced flow of the contact line generates violent velocity gradients in the triple line trail, and therefore important shear and normal stresses at the surface. The theoretical and experimental determination of these actions is a difficult task, as it requires a knowledge of the unsteady and inhomogeneous velocity field at all times and all scales [4,5]. In this talk, I will discuss the state of the art concerning the stress exerted on a surface by an impacting drop [6] and present how we have used nanoparticules as nano-probes for the shear stress enabling us to quantify the maximum shear stress exerted by the impact. [7]. We also discuss how our work can be used for a better understanding of spray cleaning processes in microelectronics industry.

Contributors

A. Lallart(1),(2),(3), A. Cartellier, P. Garnier, E. Charlaix and E. Lorenceau(1)

(1) Université Grenoble Alpes, CNRS, LIPhy, F-38000 Grenoble, France

(2) Université Grenoble Alpes, Grenoble-INP, CNRS, LEGI, F-38000 Grenoble, France

(3) STMicroelectronics, 850 Rue Jean Monnet, Crolles 38926-Cedex, France

References

[1] M. Fernandez-Raga, et al. Earth Sci Rev 171, (2017) 463.

[2] M. H. Keegan, D. H. Nash, and M. M. Stack, J Phys D: Appl Phys 46, (2013) 383001

[3] A. Roth-Nebelsick, et al. J.Exp. Bio. 73, (2022) 1155

[4]. J.Eggers et al. Phys. Fluids 22 (2010) 6

[5] J. Philippi, P.-Y. Lagree, and A. Antkowiak, J. Fluid Mech. 795, (2016) 96.

[6] X. Cheng, T.-P. Sun, and L. Gordillo, Annu. Rev. Fluid Mech. 54 (2022) 57

[7] A. Lallart et al., J. Fluid Mech. 1000 (2024) A31