Titre : Mouvement brownien en liquide fortement fluctuant Auteurs : Daniel Beysens, Revue : Thermodynamique des interfaces et mécanique des fluides Numéro : Numéro 1 Volume : 3 Date : 2019/04/25 DOI : 10.21494/ISTE.OP.2019.0377 ISSN : 2514-4642 Résumé : In this paper is reported how the Brownian motion of colloids (beads) immersed in a liquid can be affected by the local properties of the fluid and how, in turn, it can alter them. Near- critical binary mixtures are known to exhibit important concentration fluctuations when nearing their liquid-liquid critical point (CP). Photon-beating spectroscopy measurements show that colloids immersed in such a critical mixture of isobutyric acid and water exhibit a slow-down of their Brownian motion due to the fluctuation-induced critical enhancement of viscosity. However, as the mixture temperature is brought close to the CP temperature, the fluctuations lifetime becomes large enough such that the fluctuations can be in turn strongly deformed by the shear flow around the colloids. Mean-field behavior, where the influence of fluctuations can be ignored, follows. Viscosity does not increase anymore and colloids motion ceases to slow down. Éditeur : ISTE OpenScience