Self-propulsion in 2D confinement: phoretic and hydrodynamic interactions

Chemically active Janus particles generate tangential concentration gradients along their surface for self-propulsion. Although this is well studied in unbounded domains, the analysis in biologically relevant environments such as confinement is scarce. In this work, we study the motion of a Janus sp...

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Published in:The European physical journal. E, Soft matter and biological physics Soft matter and biological physics, 2021-07, Vol.44 (7), p.97-97, Article 97
Main Authors: Choudhary, Akash, Chaithanya, K. V. S., Michelin, Sébastien, Pushpavanam, S.
Format: Article
Language:English
Subjects:
Biological and Medical Physics
Biophysics
Boundaries
Complex Fluids and Microfluidics
Complex Systems
Concentration gradient
Condensed Matter
Condensed matter physics
Confinement
Hovering
Nanoparticles
Nanotechnology
Oscillations
Particle interactions
Phase diagrams
Physics
Physics and Astronomy
Polymer Sciences
Regular Article - Soft Matter
Soft and Granular Matter
Soft Condensed Matter
Surface properties
Surfaces and Interfaces
Thin Films
Trajectory analysis
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Summary:Chemically active Janus particles generate tangential concentration gradients along their surface for self-propulsion. Although this is well studied in unbounded domains, the analysis in biologically relevant environments such as confinement is scarce. In this work, we study the motion of a Janus sphere in weak confinement. The particle is placed at an arbitrary location, with arbitrary orientation between the two walls. Using the method of reflections, we study the effect of confining planar boundaries on the phoretic and hydrodynamic interactions, and their consequence on the Janus particle dynamics. The dynamical trajectories are analyzed using phase diagrams for different surface coverage of activity and solute-particle interactions. In addition to near wall states such as ‘sliding’ and ‘hovering’, we demonstrate that accounting for two planar boundaries reveals two new states: channel-spanning oscillations and damped oscillations around the centerline, which were characterized as ‘scattering’ or ‘reflection’ by earlier analyses on single wall interactions. Using phase-diagrams, we highlight the differences in inert-facing and active-facing Janus particles. We also compare the dynamics of Janus particles with squirmers for contrasting the chemical interactions with hydrodynamic effects. Insights from the current work suggest that biological and artificial swimmers sense their surroundings through long-ranged interactions, that can be modified by altering the surface properties. Graphic abstract
ISSN:1292-8941
1292-895X
DOI:10.1140/epje/s10189-021-00101-1