title: Shear-Induced Detachment of Polystyrene Beads from SAM-Coated Surfaces.
abstract: In this work we experimentally and theoretically analyze the detachment of microscopic polystyrene beads from different self-assembled monolayer (SAM) surfaces in a shear flow in order to develop a mechanistic model for the removal of cells from surfaces. The detachment of the beads from the surface is treated as a thermally activated process applying an Arrhenius Ansatz to determine the activation barrier and attempt frequency of the rate determing step in bead removal. The statistical analysis of the experimental shear detachment data obtained in phosphate-buffered saline buffer results in an activation energy around 20 kJ/mol, which is orders of magnitude lower than the adhesion energy measured by atomic force microscopy (AFM). The same order of magnitude for the adhesion energy measured by AFM is derived from ab initio calculations of the van der Waals interaction energy between the polystyrene beads and the SAM-covered gold surface. We conclude that the rate determing step for detachment of the beads is the initiation of rolling on the surface (overcoming static friction) and not physical detachment, i.e., lifting the particle off the surface.
authors.affiliation: Institute for Functional Interfaces, Karlsruhe Institute of Technology , Kaiserstraße 12, 76131 Karlsruhe, Germany.
authors.forename: Kwun Lun
authors.initials: KL
authors.lastname: Cho
authors.affiliation: Analytical Chemistry-Biointerfaces, Ruhr-University Bochum , 44801 Bochum, Germany.
authors.forename: Axel
authors.initials: A
authors.lastname: Rosenhahn
authors.affiliation: Institute of Microstructure Technology, Karlsruhe Institute of Technology , Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen, Germany.
authors.forename: Richard
authors.initials: R
authors.lastname: Thelen
authors.affiliation: Institute for Functional Interfaces, Karlsruhe Institute of Technology , Kaiserstraße 12, 76131 Karlsruhe, Germany.|Applied Physical Chemistry, University of Heidelberg , D-69120 Heidelberg, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Grunze
authors.affiliation: Department of Physics and Atmospheric Science, Dalhousie University , Halifax, Nova Scotia B3H 3J5, Canada.
authors.forename: Matthew
authors.initials: M
authors.lastname: Lobban
authors.affiliation: Department of Physics and Atmospheric Science, Dalhousie University , Halifax, Nova Scotia B3H 3J5, Canada.
authors.forename: Markus Leopold
authors.initials: ML
authors.lastname: Karahka
authors.affiliation: Department of Physics and Atmospheric Science, Dalhousie University , Halifax, Nova Scotia B3H 3J5, Canada.
authors.forename: H Jürgen
authors.initials: HJ
authors.lastname: Kreuzer
mesh_terms: D018625:Microscopy, Atomic Force; D011137:Polystyrenes / Q000737:chemistry*; D033081:Shear Strength; D013499:Surface Properties
chemical_list: D011137:Polystyrenes