MSGP Seminar 3/23/2022 Cholesterics in Cylinders and Pulsating Bubbles in Nematics

Dr. Joonwoo Jeong, UNIST, Korea, School of Physics


Abstract :

This talk will walk you through our two recent journeys with confined and confining liquid crystals (LCs): cholesterics in a cylinder and pulsating bubbles in nematic LCs. If time allows, I will introduce other ongoing and non-LC works in Experimental Soft Matter Physics (SOPHY) group at UNIST, South Korea.

First, we report our investigation of chiral nematic lyotropic chromonic LCs confined in a cylinder. They have the double-twist (DT) director configuration in a cylinder with a degenerate planar anchoring. Upon increasing the chiral dopant concentration, a discontinuous increase of twist angle occurs. This 'step-like' behavior, so-called layering transition, arises because local minima exist in the energy landscape, and a new global minimum emerges according to the dopant concentration. Consequently, meta-stable DT domains with different twist angles coexist with topological defects between them. We propose a topological invariant, Thurston-Bennequin number, to justify the existence of the topological defects.

Second, employing thermotropic nematic LCs, we demonstrate that a pulsating spherical bubble accompanying the hedgehog defect can swim in the anisotropic fluid, despite the bubble's symmetric shape and motion. The deformed nematic director field around the bubble with the hyperbolic point defect provides the centrosymmetry breaking, and the nematodynamic response to the bubble's pulsation breaks the time-reversal symmetry. Proposing a new mechanism that symmetry breaking solely in a fluid can realize symmetric and reciprocal swimmers, this study deepens our understanding of microswimmers in complex fluids.


3:20 pm (EST)
Wednesday, March 23, 2022

Meeting ID: 961 9973 6956
Passcode: 2022

POSTED: Wednesday, March 23, 2022 - 2:27pm
UPDATED: Wednesday, March 23, 2022 - 2:27pm