Berlin 2012 – wissenschaftliches Programm

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PV: Plenarvorträge

PV 20: PV XX

PV 20.1: Keynote Talk

Donnerstag, 29. März 2012, 14:00–14:45, H 0105

How superficial is adhesion? Common fundamentals of gecko, bacteria, protein and thin film adhesion — •Karin Jacobs — Saarland University, Experimental Physics, D-66041 Saarbrücken

Controlling the adhesion of biological objecs to inorganic surfaces is an important issue for multiple different disciplines, from surgery and the biomedical sciences to material engineering. For an effective control, however, a thorough understanding of the fundamentals of adhesion is necessary. If e.g. an antibacterial coating of some nanometer thickness is prepared on different substrates, will it always act antibacterial? In other words, is only the surface of two adhering bodies responsible for the adhesive strength? Our studies show that also the subsurface compositions of the interacting materials play an important role. Common examples are the adhesion of gecko paws, the sticking of bacteria, the unspecific adsorption of proteins or the stability of thin films. The reason for this is that adhesion is an interplay of short- and of long-range forces. To separate the one from the other and to allow for a controlled variation, we performed the experiments with tailored Si wafers (variable Si dioxide layer thickness, variable surface coating) as substrates. Adhesion measurements were e.g. conducted by scanning probe microscopy in force spectroscopy mode and protein adsorption was monitored by ellipsometry, X-ray and neutron reflectometry. In the various set-ups and the different systems, the same trend is recorded: Adhesion is not only superficial, the long-range van der Waals forces which make up for the subsurface force contribution, have to be taken into account.