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Gecko adhesion on flat and rough surfaces: simulations with a multi‐scale molecular model

Materzok, Tobias ; De Boer, Danna ; Gorb, Stanislav ; Müller‐Plathe, Florian (2022)
Gecko adhesion on flat and rough surfaces: simulations with a multi‐scale molecular model.
In: Small : nano micro, 18 (35)
doi: 10.1002/smll.202201674
Article, Bibliographie

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Abstract

A multiscale modeling approach is used to develop a particle‐based mesoscale gecko spatula model that is able to link atomistic simulations and mesoscale (0.44 µm) simulations. It is used to study the detachment of spatulae from flat as well as nanostructured surfaces. The spatula model is based on microscopical information about spatulae structure and on atomistic molecular simulation results. Target properties for the coarse‐graining result from a united‐atom model of gecko keratin in periodic boundary conditions (PBC), previously developed by the authors. Pull‐off forces necessary to detach gecko keratin under 2D PBC parallel to the surface are previously overestimated when only a small region of a spatula is examined. It is shown here that this is due to the restricted geometry (i.e., missing peel‐off mode) and not model parameters. The spatula model peels off when pulled away from a surface, both in the molecular picture of the pull‐off process and in the force‐extension curve of non‐equilibrium simulations mimicking single‐spatula detachment studied with atomic force microscopy equipment. The force field and spatula model can reproduce experimental pull‐off forces. Inspired by experimental results, the underlying mechanism that causes pull‐off forces to be at a minimum on surfaces of varying roughnesses is also investigated. A clear sigmoidal increase in the pull‐off force of spatulae with surface roughness shows that adhesion is determined by the ratio between spatula pad area and the area between surface peaks. Experiments showed a correlation with root‐mean‐square roughness of the surface, but the results of this work indicate that this is not a causality but depends on the area accessible.

Item Type: Article
Erschienen: 2022
Creators: Materzok, Tobias ; De Boer, Danna ; Gorb, Stanislav ; Müller‐Plathe, Florian
Type of entry: Bibliographie
Title: Gecko adhesion on flat and rough surfaces: simulations with a multi‐scale molecular model
Language: English
Date: 2022
Place of Publication: Weinheim
Publisher: Wiley-VCH
Journal or Publication Title: Small : nano micro
Volume of the journal: 18
Issue Number: 35
Collation: 10 Seiten
DOI: 10.1002/smll.202201674
Corresponding Links:
Abstract:

A multiscale modeling approach is used to develop a particle‐based mesoscale gecko spatula model that is able to link atomistic simulations and mesoscale (0.44 µm) simulations. It is used to study the detachment of spatulae from flat as well as nanostructured surfaces. The spatula model is based on microscopical information about spatulae structure and on atomistic molecular simulation results. Target properties for the coarse‐graining result from a united‐atom model of gecko keratin in periodic boundary conditions (PBC), previously developed by the authors. Pull‐off forces necessary to detach gecko keratin under 2D PBC parallel to the surface are previously overestimated when only a small region of a spatula is examined. It is shown here that this is due to the restricted geometry (i.e., missing peel‐off mode) and not model parameters. The spatula model peels off when pulled away from a surface, both in the molecular picture of the pull‐off process and in the force‐extension curve of non‐equilibrium simulations mimicking single‐spatula detachment studied with atomic force microscopy equipment. The force field and spatula model can reproduce experimental pull‐off forces. Inspired by experimental results, the underlying mechanism that causes pull‐off forces to be at a minimum on surfaces of varying roughnesses is also investigated. A clear sigmoidal increase in the pull‐off force of spatulae with surface roughness shows that adhesion is determined by the ratio between spatula pad area and the area between surface peaks. Experiments showed a correlation with root‐mean‐square roughness of the surface, but the results of this work indicate that this is not a causality but depends on the area accessible.

Uncontrolled Keywords: gecko adhesion, molecular dynamics, multiscale molecular model, pull‐off force, roughness, spatula
Identification Number: 2201674
Classification DDC: 500 Science and mathematics > 530 Physics
500 Science and mathematics > 540 Chemistry
Divisions: Profile Areas
Profile Areas > Thermo-Fluids & Interfaces
07 Department of Chemistry
07 Department of Chemistry > Eduard Zintl-Institut > Physical Chemistry
07 Department of Chemistry > Theoretische Chemie (am 07.02.2024 umbenannt in Quantenchemie)
Date Deposited: 23 Jan 2024 08:55
Last Modified: 23 Jan 2024 08:55
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