Looping Network Meetings

#57 October 28, 2024

Monday 15:00 (Paris/Warsaw time)

Qing Zhang (Stanford University)

Flow instabilities in nematic liquid crystals: from viscous fingering to spontaneous chirality

Abstract:
While flow instabilities lead to complex patterns that can be harnessed to create functional structures, controlling their self-amplified and non-linear growth remains challenging. In this talk, I will present how we exploit shear-enhanced anisotropy in lyotropic chromonic liquid crystal (LCLC) solutions to control the growth morphology of viscous-fingering instability that occurs when a less viscous fluid displaces a more viscous one between two parallel plates. By adjusting flow conditions, we induce a transition from the generic dense-branching growth characterized by repeated tip-splitting of the growing fingers to dendritic patterns with stable fingertips. Furthermore, we have discovered the emergence of flow-induced defects and structures in LCLC solutions themselves. Pure-twist disclination loops form under specific shear rates due to the material's unique elastic properties. Remarkably, chiral domains spontaneously arise in the achiral LCLC when subjected to pressure-driven flow. This chirality results from periodic double-twist deformations, leading to striking stripe patterns perpendicular to the flow direction. I will discuss the mechanisms behind these phenomena, revealing a distinct pathway to mirror symmetry breaking in fluid systems.

Recording