Taylor line swimming in microchannels and cubic lattices of obstacles

TL;DR

This study uses simulations to explore how a Taylor line swimmer moves in microchannels and obstacle lattices, revealing enhanced speeds and new geometric swimming behaviors influenced by environmental structures.

Contribution

It introduces the concept of geometric swimming in dense obstacle lattices and analyzes the swimmer's directional choices and speed behaviors in microstructured environments.

Findings

Enhanced swimming speed near walls and in dilute lattices

Discovery of geometric swimming in dense obstacle lattices

All data collapse on a master curve when plotting velocity against lattice vector magnitude

Abstract

Microorganisms naturally move in microstructured fluids. Using the simulation method of multi-particle collision dynamics, we study an undulatory Taylor line swimming in a two-dimensional microchannel and in a cubic lattice of obstacles, which represent simple forms of a microstructured environment. In the microchannel the Taylor line swims at an acute angle along a channel wall with a clearly enhanced swimming speed due to hydrodynamic interactions with the bounding wall. While in a dilute obstacle lattice swimming speed is also enhanced, a dense obstacle lattice gives rise to geometric swimming. This new type of swimming is characterized by a drastically increased swimming speed. Since the Taylor line has to fit into the free space of the obstacle lattice, the swimming speed is close to the phase velocity of the bending wave traveling along the Taylor line. While adjusting its swimming motion within the lattice, the Taylor line chooses a specific swimming direction, which we classify by a lattice vector. When plotting the swimming velocity versus the magnitude of the lattice vector, all our data collapse on a single master curve. Finally, we also report more complex trajectories within the obstacle lattice.