Non-monotonic speed-dependence of microswimmers on wall distance

While substrates naturally occur in most microswimmer experiments, their impact on the swimming performance is not well understood. In the present study, we functionalize substrates with polymer brushes of varying swelling properties, grafting densities and brush lengths to systematically modify and...

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Bibliographic Details
Published in:Soft matter 2021-10, Vol.17 (41), p.9428-9433
Main Authors: Heidari, Mojdeh, Jakob, Franziska, Liebchen, Benno, von Klitzing, Regine
Format: Article
Language:English
Subjects:
Brushes
Landscape design
Polymers
Substrates
Surface charge
Surface roughness
Swimming
Thickness
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Summary:While substrates naturally occur in most microswimmer experiments, their impact on the swimming performance is not well understood. In the present study, we functionalize substrates with polymer brushes of varying swelling properties, grafting densities and brush lengths to systematically modify and explore the substrate-swimmer interactions. Notably, the swimming speed does not monotonically change with brush thickness, but shows a distinct maximum at a certain intermediate thickness, which results from two counteracting factors: surface charge and surface roughness. The results show that the speed of thermophoretic microswimmers does not only depend on the particle properties but is also strongly influenced by the properties of the underlying substrate. This provides a route to control the speed of microswimmers via the underlying substrate, which could be applied in the future e.g. to design complex motility landscapes by patterning substrates with polymer brushes. It is expected that similar effects would occur for diffusio- and electrophoretic particles. While substrates naturally occur in most microswimmer experiments, their impact on the swimming performance is not well understood.
ISSN:1744-683X
1744-6848
DOI:10.1039/d1sm01277k