Surface characterization of viscoelastic materials through spectral intermittent contact atomic force microscopy

The ability to recover material properties at the atomic scale has been the ongoing objective of the Atomic Force Microscope (AFM). More specifically, the most popular operation of the probe with this microscope (Intermittent Contact AFM) has not yet been able to resolve material properties of viscoelastic samples. By using the force and position time signals of the AFM and the constitutive equations for linear viscoelasticity, a method is developed by which such material properties are extracted in real-time scanning. A parametric study is then performed by simulating surface and AFM system conditions to understand the limits under which the method can accurately be performed in experiment. Suggestions are made to help experimentalists optimize the method to cater to the range of viscoelastic materials being measured and the results are related to measured material properties in literature. The method is found to be accurate for a wide range of viscoelastic materials.