Séminaire de Mécanique d'Orsay

Le Jeudi 23 juin 2022 à 14h00 - Salle des séminaires FAST-LPTMS (Bât. 530, salle C.120, 1er)

Temperature-induced phase separation of an ionic liquid binary mixture in microfluidics : Marangoni flows and thermocapillary instability

Marie-Caroline Jullien
IPR - Univ. Rennes1

Ionic liquids have remarkable properties and are commonly harnessed for green chemistry, lubrication, and energy applications. In this presentation, we study a thermoresponsive ionic liquid (IL) solution mixed with water which has the property of phase separating above a critical temperature, an interesting feature for the recovery of the IL-rich phase. For this purpose, we generate a temperature gradient in a microfluidic cavity where the confinement strengthens wetting effects and enhances the demixing. Depending on the solution composition, three regime are observed: 1) below 33% of IL, the phase separation is performed by the joint effects of sedimentation and thermocapillary actuation giving rise to a three dimensional flow structure, which is quantitatively captured by our model ; 2) for a concentration lying between 33 and 55 %, a thermocapillary instability is observed that we recover quite well using a linear stability analysis, and finally, 3) above 55% in IL, water droplets are expelled outward by thermocapillarity.

Accès Salle des séminaires FAST-LPTMS (Bât. 530, salle C.120, 1er)