Confinement Enhances the Diversity of Microbial Flow Fields

Area of Science:

• Fluid dynamics
• Microbiology
• Biophysics

Background:

• Microorganismal fluid flows are crucial in various processes.
• Flows under tight confinement remain experimentally under-investigated.
• Existing models predict universal flow fields dominated by swimmer body size due to Stokelet screening.

Purpose of the Study:

• To experimentally investigate microorganismal fluid flows under confinement.
• To challenge the prevailing assumption of universal flow fields in confined geometries.
• To explore the influence of microswimmer details on confined hydrodynamics.

Main Methods:

• Combined experimental approaches with theoretical modeling.
• Investigated microswimmer behavior and flow fields in confined environments.
• Developed an effective 2D model to capture hydrodynamic properties.

Main Results:

• Contrary to expectations, confinement does not universally collapse differences between microorganisms.
• Minute details such as microswimmer spinning and propulsion appendage arrangement play a leading role.
• Qualitative topological properties of hydrodynamic flow fields are significantly influenced by these micro-details.
• An effective 2D model accurately captures these effects even under weak confinement.

Conclusions:

• Active confined hydrodynamics is more complex than previously understood.
• Flow fields in confinement depend subtly on microswimmer size, shape, and propulsion.
• Microswimmer details are critical for understanding confined fluid dynamics, not just body size.