Alignment of a topological defect by an activity gradient

TL;DR

This paper investigates how activity gradients can be used to control the orientation and motion of topological defects in active materials through analytic, theoretical, and numerical methods.

Contribution

It introduces a combined approach using analytic solutions, symmetry-based theory, and simulations to show activity gradients align defect orientation.

Findings

Activity gradients align defect orientation.

Alignment influences defect motion control.

Multiple methods confirm the effect of activity gradients.

Abstract

As a method for controlling active materials, researchers have suggested designing patterns of activity on a substrate, which should guide the motion of topological defects. To investigate this concept, we model the behavior of a single defect of topological charge $+1/2$, moving in an activity gradient. This modeling uses three methods: (1) approximate analytic solution of hydrodynamic equations, (2) macroscopic, symmetry-based theory of the defect as an effective oriented particle, and (3) numerical simulation. All three methods show that an activity gradient aligns the defect orientation, and hence should be useful to control defect motion.