Guiding microscale swimmers using teardrop-shaped posts

Abstract

The swimming direction of biological or artificial microscale swimmers tends to be randomised over long time-scales by thermal fluctuations. Bacteria use various strategies to bias swimming behaviour and achieve directed motion against a flow, maintain alignment with gravity or travel up a chemical gradient. Herein, we explore a purely geometric means of biasing the motion of artificial nanorod swimmers. These artificial swimmers are bimetallic rods, powered by a chemical fuel, which swim on a substrate printed with teardrop-shaped posts. The artificial swimmers are hydrodynamically attracted to the posts, swimming alongside the post perimeter for long times before leaving. The rods experience a higher rate of departure from the higher curvature end of the teardrop shape, thereby introducing a bias into their motion. This bias increases with swimming speed and can be translated into a macroscopic directional motion over long times by using arrays of teardrop-shaped posts aligned along a single direction. This method provides a protocol for concentrating swimmers, sorting swimmers according to different speeds, and could enable artificial swimmers to transport cargo to desired locations.

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• Chiral Active Particles are Sensitive Reporter to Environmental Geometry
• Activity-induced microswimmer interactions and cooperation in one-dimensional environments
• The flow field around a confined active droplet
• Geometric effects induce anomalous size-dependent active transport in structured environments
• Active particles with polar alignment in ring-shaped confinement
• Random motion of a circle microswimmer in a random environment
• Quasi-two-dimensional bacterial swimming around pillars: enhanced trapping efficiency and curvature dependence
• Fluid circulation driven by collectively organized metachronal waves in swimming T. aceiti nematodes
• Macrotransport of active particles in periodic channels and fields: rectification and dispersion