Institute of Physical Chemistry and Cluster of Excellence livMatS
The AFM is a versatile tool to investigate a large and still growing number of systems, in particular in combination with fluorescence microscopy.
First, we will present an investigation of human cartilage. In a combination of AFM and fluorescence microscopy we can show that local changes in the organization of fluorescent stained cells, a marker for early osteoarthritis, lead to a significant local reduction of the elastic modulus, local thinning of the collagen fibers, and a roughening of the articular surface . This approach is currently extended towards locally measuring the frequency dependent storage and loss modulus by AFM indentation and its correlation to fluorescence images.
Second, we will present fundamental insights into the formation and breaking of multivalent bonds. Since the first mechanical characterization of the silicon-carbon bond by AFM in 1999 , many other physical and chemical bonds have been characterized, usually in well defined systems. Here, we disentangle physical and chemical bonds that form in mussel-inspired coatings. Both, the timescale of bond formation and their strength is determined. This helps to understand the interplay between adsorption (physisorption) and chemical reactions (chemisorption) in polymer coatings.
 Tschaikowsky et al., Acta Biomaterialica, in revision
 Grandbois et al., Science, 283 (5408), 1727-1730 (1999)