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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 39: POSTERS Colloids and Liquids

CPP 39.7: Poster

Donnerstag, 26. März 2009, 17:00–19:30, P3

Studying mechanical microcontacts of fine particles with the quartz crystal microbalance — •Ewa Ilska, Michael Kappl, and Hans-Jürgen Butt — Max-Planck-Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany

Micromechanical contacts are an important issue in a wide variety of applications. Although their significance is acknowledged and micromechanics is widely studied e.g. in pharmaceutical or electronics industry, fundamental knowledge is still limited. Within this work, we attempt to understand and describe the physics behind particles and polymer surface contacts. We apply therefore the quartz crystal microbalance (QCM) technique, supported by particles video tracking and atomic force microscopy (AFM) imaging of contact zones. Glass particles of several diameters were deposited onto a thick polystyrene film, which was spin-coated onto the QCM surface. The shift of the resonance frequency f0 of the QCM signal depends in a complex manner on the mass loading but also on the coupling strength between surface and particles. Addition of small particles leads to a decrease of resonance frequency due to the added mass. Addition of larger particles leads to an f0 increase, further enhanced by oscillation amplitude. After annealing, amplitude increase and particle detachment are found to strongly influence the resonance behaviour. These striking differences can be explained by the different coupling of particles to the PS film. This is also supported by AFM images of the contact zones after particle removal.