Squirmer hydrodynamics near a periodic surface topography

Area of Science:

• Fluid dynamics
• Microhydrodynamics
• Soft matter physics

Background:

• Microswimmer behavior near surfaces is crucial for understanding biological and artificial systems.
• Previous studies focused on large or very small surface features, leaving an intermediate scale unexplored.

Purpose of the Study:

• To investigate the behavior of a spherical squirmer near periodic sinusoidal surface topographies.
• To determine how microswimmer dynamics are influenced by surface topography features at an intermediate scale.

Main Methods:

• Utilized the nearest neighbor regularized Stokeslet method for numerical simulations.
• Validated the method's accuracy for a spherical squirmer near a flat surface before applying to complex topographies.

Main Results:

• The squirmer's size relative to the topography wavelength is the key factor governing its behavior.
• Directional guidance was observed only when the squirmer size was comparable to the topography wavelength, often leading to capture in troughs.
• Complex dynamics emerged with varied initial configurations, while amplitude and shape variations had minor impacts.

Conclusions:

• Microswimmer behavior is highly sensitive to the interplay between swimmer size and surface topography wavelength.
• The developed numerical framework is essential for studying microswimmer guidance by surface topographies.