Slender Phoretic Theory of chemically active filaments

TL;DR

This paper develops a comprehensive slender body theory for chemically active filaments of arbitrary 3D shape, revealing that azimuthal variations significantly influence their swimming behavior, unlike previous models limited to straight rods.

Contribution

It introduces a novel slender body theory for complex 3D shaped phoretic filaments, extending beyond previous axisymmetric straight rod models.

Findings

Azimuthal variations can dominate swimming kinematics.

The theory applies to arbitrary 3D shapes and patterns.

Curvature and confinement influence propulsion significantly.

Abstract

Artificial microswimmers, or "microbots" have the potential to revolutionise non-invasive medicine and microfluidics. Microbots that are powered by self-phoretic mechanisms, such as Janus particles, often harness a solute fuel in their environment. Traditionally, self-phoretic particles are point-like, but slender phoretic rods have become an increasingly prevalent design. While there has been substantial interest in creating efficient asymptotic theories for slender phoretic rods, hitherto such theories have been restricted to straight rods with axisymmetric patterning. However, modern manufacturing methods will soon allow fabrication of slender phoretic filaments with complex three-dimensional shape. In this paper, we develop a slender body theory for the solute of self-diffusiophoretic filaments of arbitrary three-dimensional shape and patterning. We demonstrate analytically that, unlike other slender body theories, first-order azimuthal variations arising from curvature and confinement can have a leading order contribution to the swimming kinematics.