Regensburg 2010 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 30: Poster: Micro and Nanofluidics
CPP 30.13: Poster
Mittwoch, 24. März 2010, 17:30–19:00, Poster C
Deriving elastic properties of rubber substrates by analyzing the shape of nanodroplets on their surface — •Konstantina Kostourou1, Stephan Herminghaus1, and Ralf Seemann1,2 — 1Max Planck Institute for Dynamics and Self-Organization, D-37073 Göttingen, Germany — 2Experimental Physics, Saarland University, 66041 Saarbrücken, Germany
We study the shape of polystyrene (PS) nanodroplets generated by the complete dewetting of a PS thin film on rubber elastic substrates of cross-linked Polydimethylsiloxane (PDMS). We are interested in the full shape of the droplet, i.e. the shape of the air/PS interface, the deformation at the dry side of the three phase contact line (TPCL) and the deformation below the droplet. The exact position of the TPCL is determined by scanning the air/PS interface with Harmonix™ AFM, a tool which allows us to extract the elasticity of the material. Thus, overlapping the topography and elasticity signals, we identify the crossover from PDMS to PS, i.e. the TPCL. In parallel, the deformation at the dry side of the TPCL is compared to the one calculated by existing theories. Using the theoretical model as a fitting function with the Elastic modulus being the only free parameter, we can extract the elasticity of the substrate. Finally, the PS/PDMS interface is also imaged by AFM. Quantifying the deformation below the droplet and applying a nanoindentation model, we can extract the substrate Elastic modulus, which is compared and found in very good agreement with the one calculated by the fitting of the dry side of the TPCL.