Hydrodynamics can Determine the Optimal Route for Microswimmer Navigation

TL;DR

This paper investigates how the flow fields generated by microswimmers influence their optimal navigation strategies, revealing non-intuitive trajectories and demonstrating that hydrodynamics can significantly reduce travel time.

Contribution

It systematically analyzes the impact of microswimmer flow fields on optimal navigation, highlighting the importance of hydrodynamics in designing efficient microscale movement strategies.

Findings

Optimal trajectories are non-intuitive and flow-dependent.

Hydrodynamics can halve the time to reach a target.

Strategic control of distance to walls enhances survival.

Abstract

Contrasting the well explored problem on how to steer a macroscopic agent like an airplane or a moon lander to optimally reach a target, "optimal microswimming", i.e. the quest for the optimal navigation strategy for microswimmers, remains unsolved. Here, we systematically explore this problem and show that the characteristic flow field of microswimmers crucially influences the required navigation strategy to reach a target fastest. The resulting optimal trajectories can have remarkable and non-intuitive shapes, which qualitatively differ from those of dry active particles or motile macroagents. Our results provide generic insights into the role of hydrodynamics and fluctuations on optimal navigation at the microscale and suggest that microorganisms might have survival advantages when strategically controlling their distance to remote walls. In particular, when fluctuations are present, choosing the optimal strategy, which appropriately respects hydrdynamics, can halve the time to reach the target compared to cases microswimmers head straight towards it.