Tunable Three-Dimensional Architecture of Nematic Disclination Lines

TL;DR

This paper develops a theoretical and experimental framework to control three-dimensional disclination lines in nematic liquid crystals, enabling advanced manipulation of defect structures for various applications.

Contribution

It introduces a new theoretical approach and experimental method to tailor and predict the 3D architecture of disclination lines in nematic liquid crystals.

Findings

Disclination lines connect same-charge defects on opposite surfaces.

Disclination lines are attracted to high-twist regions.

Experimental and simulation results agree on disclination behavior.

Abstract

Disclinations lines play a key role in many physical processes, from the fracture of materials to the formation of the early universe. Achieving versatile control over disclinations is key to developing novel electro-optical devices, programmable origami, directed colloidal assembly, and controlling active matter. Here, we introduce a theoretical framework to tailor three-dimensional disclination architecture in nematic liquid crystals experimentally. We produce quantitative predictions for the connectivity and shape of disclination lines found in nematics confined between two thinly spaced glass substrates with strong planar anchoring. By drawing an analogy between nematic liquid crystals and magnetostatics, we find that: i) disclination lines connect defects with the same topological charge on opposite surfaces, and ii) disclination lines are attracted to regions of the highest twist. Using polarized light to pattern the in-plane alignment of liquid crystal molecules, we test these predictions experimentally and identify critical parameters that tune the disclination lines' curvature. We verify our predictions with computer simulations and find non-dimensional parameters enabling us to match experiments and simulations at different length scales. Our work provides a powerful method to understand and practically control defect lines in nematic liquid crystals.