Characterization of Surface Mechanical Properties of Polymer Coatings using AFM Force Distance Curves

We use the force distance curve mode of Tosca Atomic Force Microscope to characterize the surface mechanical properties of polymer coatings.

The atomic force microscope (AFM) provides not only high resolution 3D surface images using various imaging modes but also allows sensitive force measurements using force distance curves. The first studies on force distance curve date back to the early 1990s shortly after the invention of AFM. In principle, force distance curves can be performed on any kind of surface and in any kind of environment. Force distance curve controls the force applied on the sample via the controlled movement of z-piezo. In AFM imaging modes, the cantilever moves in xy directions as well as in z direction to record 3D surface images. In AFM force distance curve mode, the cantilever moves only in z direction for a single point force measurement, consisting of a full cycle of approaching to the surface and retracting from the surface. The force curve measurement has high lateral resolution in nanometer range depending on the AFM tip radius, high vertical resolution in subnanometer to pm range depending on z-piezo resolution and system noise, and high force resolution down to pN range depending on cantilever properties. The force distance curves are usually fitted by various contact mechanics models to extract quantitative nanomechanical properties of the sample such as Young’s modulus and adhesion. Here we use Tosca to characterize the mechanical properties of a thin film of polymer blends.

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