“…For example, the nanoscopic, frictional forces between functionalized tips and surfaces have been determined 2,6 and the mechanical properties of viruses, DNA, carbon nanotubes, and fibrin fibers have been measured. [7][8][9] In all AFM force measurements, the AFM cantilever is used to apply forces to the sample under investigation. To extract reliable, quantitative values for material properties from these measurements, the applied forces need to be accurately known, which, in turn, critically depends on reliable and universally applicable force calibration methods for AFM instruments.…”