(in collaboration with Pengtao Yue of Virginia Tech and Jean-Christophe Loudet of Université de Bordeaux)

Complex fluids are often used as mixtures as in polymer blends and polymer-dispersed liquid crystals (PDLCs). The flow and rheology of such materials depend on two factors: the complex rheology of the components and the interfacial dynamics. Both are formidable tasks for modeling and simulation.

Our group has been working on this topic since 2004, when we developed a diffuse-interface model that handles these two factors in a unified theoretical framework. Over the years, we have tackled a host of problems, including drop interaction, breakup, coalescence and retraction in Newtonian and viscoelastic fluids, liquid crystals and ferrofluids, as well as dynamics of thin filaments and films. Some of this work has been summarized in review articles.

More recently, we have focused on the dynamics of colloidal particles straddling an isotropic-nematic interface. The diffuse interface model couples the capillary forces on the interface with the elastic stresses in the nematic phase, while allowing a self-contained treatment of the three-phase contact line. The following graphs show how the nematic anchoring on the particle mediates orientational defects inside the liquid crystal and the particle motion on the isotropic-nematic interface:

Diagrams showing conflict between the anchoring on the particle and the bulk nematic orientation.

Defects near a particle translating along the interface with different anchoring strength.