Unidirectional Droplet Propulsion onto Gradient Brushes without External Energy Supply

Using extensive molecular dynamics simulation of a coarse-grained model, we demonstrate the possibility of sustained unidirectional motion (durotaxis) of droplets without external energy supply when placed on a polymer brush substrate with stiffness gradient in a certain direction. The governing key...

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Bibliographic Details
Published in:arXiv.org 2023-03
Main Authors: Kajouri, Russell, Theodorakis, Panagiotis E, Deuar, Piotr, Bennacer, Rachid, Židek, Jan, Egorov, Sergei A, Milchev, Andrey
Format: Article
Language:English
Subjects:
Brushes
Droplets
Interfacial energy
Molecular dynamics
Polymers
Stiffness
Substrates
Online Access:Get full text
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Summary:Using extensive molecular dynamics simulation of a coarse-grained model, we demonstrate the possibility of sustained unidirectional motion (durotaxis) of droplets without external energy supply when placed on a polymer brush substrate with stiffness gradient in a certain direction. The governing key parameters for the specific substrate design studied, which determine the durotaxis efficiency, are found to be the grafting density of the brush and the droplet adhesion to the brush surface, whereas the strength of the stiffness gradient, the viscosity of the droplet, or the length of the polymer chains of the brush have only a minor effect on the process. It is shown that this durotaxial motion is driven by the steady increase of the interfacial energy between droplet and brush as the droplet moves from softer to stiffer parts of the substrate whereby the mean driving force gradually declines with decreasing roughness of the brush surface. We anticipate that our findings indicate further possibilities in the area of nanoscale motion without external energy supply.
ISSN:2331-8422
DOI:10.48550/arxiv.2303.02652