Imaging viscoelasticity by force modulation with the atomic force microscope

Force modulation and phase sensitive detection was used to image soft surfaces with the atomic force microscope. This force modulation microscopy allows the simultaneous recording of images of the surface profile, the storage modulus, and the loss modulus of the sample. A theoretical treatment of the elastic tip-sample interaction is given. As examples, images of Langmuir-Blodgett films of a polymeric amphiphile and of a structured fatty acid are presented.