The scan-velocity dependence of friction force microscopy (FFM) is characterized on nominally-dry gelatin films and related to the rate dependence of dissipative molecular relaxations. For a range of scanning-parameter values the measurement itself affects the frictional characteristics of the films: imparted frictional energy populates molecular conformations from which more dissipative relaxations occur. Variations in frictional dissipation tens of nanometers in lateral size are quantified as histograms of the number of image pixels versus frictional force. Histogram breadth and symmetry apparently reflect the energy dispersion of molecular relaxations.
- force microscopy