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Driven Shear Flow in Biological Magnetoactive Fluids
M Marmol1,2, C Cottin-Bizonne2, A Cēbers3
1BIAM, CNRS, CEA, Aix Marseille Université, 13115 Saint Paul-Lez-Durance, France.
Physical Review Letters
|January 2, 2026
Summary
Researchers harnessed magnetotactic bacteria
Area of Science:
- Physics and Biology
- Active Matter Physics
- Biophysics
Background:
- Active fluids exhibit spontaneous patterns and flows.
- Controlling active fluid behavior with external cues is crucial for applications.
Purpose of the Study:
- To investigate the control of macroscopic shear flows using magnetotactic bacteria.
- To understand how external fields influence the collective behavior of active swimmers.
Main Methods:
- Utilizing magnetotactic bacteria responsive to magnetic and chemical signals.
- Applying external fields to shape swimmer order and generate active stress.
- Developing a magnetoactive model to capture observed flows.
Main Results:
- External fields successfully controlled the onset of global scale shear flows.
- The collective force dipoles of swimmers formed a finite active stress.
- The model quantitatively predicted steady-state flows.
- Time-dependent responses to rotating fields revealed complex dynamics.
Conclusions:
- Magnetotactic bacteria can be effectively controlled to generate macroscopic flows.
- Active stress generated by ordered swimmers is a key factor in flow generation.
- The developed model provides a quantitative framework for understanding active fluid dynamics.
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