Berlin 2012 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 9: Biopolymers and Biomaterials (joint session with BP)
CPP 9.6: Vortrag
Dienstag, 27. März 2012, 11:00–11:15, H 1058
Adhesion of gecko setae reflects nanoscale differences in subsurface energy — •Peter Loskill1, Jonathan Puthoff2, Matt Wilkinson2, Kellar Autumn2, and Karin Jacobs1 — 1Saarland University, Experimental Physics, D-66041 Saarbrücken, Germany — 2Department of Biology, Lewis & Clark College, Portland, OR 97219, USA
Surface energies are commonly employed to determine the adhesive forces between materials. However, the component of surface energy derived from long-range forces, such as van der Waals forces, depends on the material’s structure below the outermost atomic layers. Prior theoretical results and indirect experimental evidence suggest that the van der Waals energies of subsurface layers will influence interfacial adhesion forces. We discovered that nanometerscale differences in the oxide layer thickness of silicon wafers result in significant macroscale differences in the adhesion of isolated gecko setal arrays. Si/SiO2 bilayer materials exhibited stronger adhesion when the SiO2 layer is thin (approx. 2 nm). To further explore how layered materials influence adhesion, we functionalized similar substrates with an OTS monolayer and again identified a significant influence of the oxide layer thickness on adhesion. Our theoretical calculations describe how variation in the silicon dioxide layer thickness produces differences in the van der Waals interaction potential, and these differences are reflected in the adhesion mechanics. Setal arrays employed as tribological probes provide the first empirical evidence that the ‘subsurface energy’ of inhomogeneous materials influences the macroscopic surface forces.