Microswimmer dynamics in a Hele-Shaw droplet

Bacterial motility is strongly influenced by confinement. Here, we derive an asymptotic solution for the flow about a microswimmer enclosed in a weakly deformable Hele-Shaw drop-a drop sandwiched between two solid planes. For a microswimmer modelled as a dipole, we explore the swimmer's trajectory, the evolution of the droplet interface and the drop velocity. The results show that at steady state, the dipole induces droplet translation with a velocity independent of the dipole location and in the same direction as the dipole orientation. The trajectory of the swimming dipole is significantly affected by droplet deformability.This article is part of the theme issue 'Biological fluid dynamics: emerging directions'.