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Metallic microswimmers driven up the wall by gravity
Quentin Brosseau1, Florencio Balboa Usabiaga2, Enkeleida Lushi3
1Applied Mathematics Laboratory, Courant Institute, New York University, NY, NY 10012, USA.
Soft Matter
|July 14, 2021
Summary
Tail-heavy nanorods use boundary interactions to climb surfaces against gravity. Hydrodynamic drag asymmetry enhances this upward movement, enabling even heavy microswimmers to ascend vertical planes.
Area of Science:
- Physics, Nanotechnology, Fluid Dynamics
Background:
- Autophoretic bimetallic nanorods are microswimmers propelled by chemical fuels like hydrogen peroxide.
- These nanorods exhibit complex motion influenced by gravity and surrounding environments.
Purpose of the Study:
- To investigate the gravitactic behavior of tail-heavy autophoretic bimetallic nanorods.
- To understand the role of solid boundaries in facilitating upward movement and climbing of microswimmers.
Main Methods:
- Experimental observation of nanorod motion on inclined planes in a hydrogen peroxide fuel.
- Theoretical modeling and simulations to analyze hydrodynamic interactions and torques.
- Investigating the effect of boundary proximity on nanorod orientation and ascent.
Main Results:
- Tail-heavy nanorods preferentially orient upwards and ascend inclined planes.
- Solid boundaries significantly enhance gravitaxis, enabling microswimmers to climb nearly vertical surfaces.
- Hydrodynamic interactions with walls create a fore-aft drag asymmetry that reinforces gravitational alignment.
Conclusions:
- Boundary-induced hydrodynamic interactions are crucial for efficient gravitaxis in microswimmers.
- This mechanism allows even dense or heavy nanorods to overcome gravity and ascend challenging inclines.
- Findings have implications for designing and controlling microswimmers in complex fluidic environments.
