Vendredi 10 octobre 2025 à 11h00 ; salle 259, IUSTI
Lubricant-infused surfaces (LIS) are engineered materials that incorporate a stable liquid-liquid interface between a trapped lubricant and a working fluid. This configuration is expected to promote remarkable interfacial slip, enabling applications from anti-biofouling to thrombosis prevention. However, unlike controlled lab settings, real environments expose LIS to surface-active chemical contaminants. Even traces amounts of these surfactants can accumulate at the sheared water/lubricant interface, inducing Marangoni stresses that oppose the flow and reduce interfacial slip. This raises a key question: what kinematic condition should be imposed at the interface to predict the averaged behavior of the flow, especially in engineering contexts? In the presence of surfactants, accurately determining the stopping point positions and the resulting Marangoni stress poses a significant challenge due to the numerous hidden physico-chemical variables. Consequently, many numerical and analytical models fail to predict the experimental velocity field at the liquid-liquid interface, leading to inaccurate predictions of the flow within the working fluid. We propose using Doppler Optical Coherence Tomography (D-OCT) to characterize local flows near the liquid-liquid interface of a LIS under controlled surfactant conditions. This technique is relatively new in the soft-matter hydrodynamics community, and enables live in-situ velocimetry with velocities up to v ~ 10cm/s and with a spanwise/depthwise resolution of d ~ 2µm.