Hydrodynamic capture and release of a microswimmer by a meniscus corner

TL;DR

This study investigates how microswimmers interact with meniscus corners in microchannels, revealing how hydrodynamic forces influence their trapping, escape, and trajectory, with implications for manipulating microscale swimmers.

Contribution

The paper combines experiments, theory, and simulations to elucidate hydrodynamic interactions of microswimmers with corner geometries, enabling controlled manipulation.

Findings

Pusher-type microswimmers are attracted and transiently trapped at corners.

Hydrodynamic interactions depend on swimmer type, corner geometry, and viscosity ratio.

Swimmer trajectories can be tuned by geometrical and fluid parameters.

Abstract

Biological microswimmers alter their motility in complex corner geometries, facilitating their survival. However, the dynamical features of low-Reynolds-number swimming at corners remain undefined. Here, we use active droplet microswimmers near a confined meniscus in a microchannel as a model system to study how microswimmer-corner interactions determine swimming patterns. Combining experiments, theory and simulations, we show that pusher-type micrsowimmers are attracted towards a meniscus corner, followed by transient trapping and eventual escape. We demonstrate that hydrodynamic interactions with the wall-interface corner intimately dictate the attraction and trapping or escape of the microswimmer on the basis of its strength. We show that the swimming trajectory at the meniscus corner can be tuned depending on the type of the microswimmer, the corner geometry and the viscosity ratio for the liquid interface. Our study provides a simple way to manipulate microswimmers by exploiting their hydrodynamic interactions near corner geometries.