Studies of adhesion and friction on the micro- and nanoscale are fundamental for the understanding of our general understanding of these processes in natural phenomena as well as in industrial applications. Friction between macroscopic objects generally takes place at microcontacts. The function of micromechanical devices depends critically on the minimization of friction and adhesion to avoid failure due to stiction. The interactions between small particles, i.e., adhesion and friction forces, are important for processes as the aggregation and dispersal of powders and colloids and the flow properties of granular matter.

We employ atomic force microscopy(AFM)-based techniques to study the interaction between individual micrometer-sized particles using so-called colloid probes, i.e. single partciles that have been mounted at the end of an AFM cantilever. Functionalized AFM tips allow the investigations of the adhesion behavior of single nanocontacts or single molecule spectroscopy of biomimetic adhesives or to study the influence of humidity on adhesion via the capillary force.

• Gojzewski, H, M. Kappl, A. Ptak, H.-J. Butt: Effect of Humidity on Nanoscale Adhesion on Self-Assembled Thiol Monolayers Studied by Dynamic Force Spectroscopy.
  Langmuir, 2010, 26(3), 1837-1847.
• Ptak, A., M. Kappl, S. Moreno-Flores, H, Gojzewski, H.-J. Butt: Quantitative characterization of nanoadhesion by dynamic force spectroscopy.
  Langmuir 2009, 25, 256-261.
• Wang, J., M. Nawaz Tahir, M. Kappl, W. Tremel, N. Metz, M. Barz, P. Theato, H.-J. Butt: Influence of Binding-Site Density in Wet Bioadhesion.
  Adv. Mater., 2008, 20, 3872-3876
• Ling, X., H.-J. Butt, M. Kappl: Quantitative measurement of friction between single microspheres by friction force microscopy.
  Langmuir, 2007, 23, 8392-8399.