Theoretical modeling of catalytic self-propulsion

TL;DR

This paper reviews the theoretical understanding of catalytic microswimmers' self-propulsion, emphasizing ionic effects, non-linear phenomena, and recent advances in modeling their complex behaviors.

Contribution

It provides a comprehensive summary of recent theoretical models, highlighting the roles of diffusiophoretic and electrophoretic effects and addressing non-linear dynamics in catalytic microswimmers.

Findings

Ionic self-propulsion involves both diffusiophoretic and electrophoretic effects.

Non-linear effects can cause direction reversal in particle motion.

Theoretical challenges remain in modeling complex active matter behaviors.

Abstract

Self-propelling particles or microswimmers have opened a new field of investigation with both fundamental and practical perspectives. They represent very convenient model objects for experimental studies of active matter, and have implications in nano-robotics, drug delivery, and more. Here, we summarize recent advances in theoretical description of the self-propulsion of catalytic microswimmers that non-uniformly release ions, including its physical origins and the current switch in focus to non-linear effects, geometric tuning and more. In particular, we show that the ionic self-propulsion always includes both diffusiophoretic and electrophoretic contributions, and that non-linear effects are physical causes of a number of intriguing phenomena, such as the reverse in the direction of the particle motion in response to variations of the salt concentration or self-propulsion of electro-neutral particles. We finally suggest several remaining theoretical challenges in the field.