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Rotating oil droplets driven by motile bacteria at interfaces
Narendra K Dewangan1, Jacinta C Conrad1
1Department of Chemical and Biomolecular Engineering, University of Houston, Houston, TX 77204, USA. jcconrad@uh.edu.
Soft Matter
|November 7, 2019
Summary
Motile bacteria adhered to oil droplets near an interface can induce droplet rotation. Bacterial type, droplet size, and surfactant presence influence rotation speed, demonstrating bacterial manipulation of droplets.
Area of Science:
- Fluid dynamics
- Microbiology
- Soft matter physics
Background:
- Microbial motility can generate fluid flows.
- Interactions between microorganisms and interfaces are complex.
- Controlling micro-scale objects is a growing area of research.
Purpose of the Study:
- To investigate the rotational manipulation of oil droplets by bacteria.
- To understand the role of bacterial adhesion and hydrodynamics in droplet rotation.
- To explore factors influencing the speed of bacterial-driven droplet rotation.
Main Methods:
- Observing oil droplets suspended near a liquid-solid interface.
- Utilizing motile bacteria (e.g., Escherichia coli, Shewanella haliotis, Halomonas titanicae) adhered to droplet surfaces.
- Analyzing droplet rotation speed in response to varying droplet size, bacterial species, and surfactant concentration.
Main Results:
- Oil droplets rotate clockwise due to bacteria-mediated hydrodynamic interactions.
- Droplet rotation speed decreases with increasing droplet size.
- Different bacterial species exhibit varying rotation speeds based on adhesion and affinity.
- Surfactant addition reduces bacterial adhesion and lowers rotation speed.
Conclusions:
- Bacterial activity can effectively drive and control the rotation of suspended oil droplets.
- Hydrodynamic interactions between bacteria and the liquid-solid interface are key to this phenomenon.
- This study highlights the potential of using microorganisms for micro-manipulation applications.
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