In an AFM-based single molecule force spectroscopy experiment, a functionalized AFM cantilever tip is brought into contact with a surface such that the polymer at the AFM cantilever tip physisorbs to this surface. By retracting the AFM cantilever tip from the surface, a change in the deflection of the AFM cantilever is converted into a force leading to a force-extension curve.

 

Physical parameters such as stretching force, desorption force and desorption length can be determined dependent on different parameters such as pulling velocity, dwell time on surface, indentation depth into the surface, temperature, solvent and different surfaces like solid substrates, polymer films or supported lipid bilayers. Furthermore, a polymer can be probed in different spatial directions, thus investigating the frictional properties of the polymer.

 

Covalent attachment of a polymer to an AFM cantilever tip is essential for such studies because only then can hundreds of force-extension curves with one and the same single molecule be obtained. We develope functionalization protocols that can easily be applied to a variety of polymers.

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Literature:

A. Kolberg, C. Wenzel, T. Hugel, M. Gallei & B.N. Balzer
Covalent attachment of single molecules for AFM-based force spectroscopy
J. Vis. Exp., 157, e60934 (2020). https://doi.org/10.3791/60934