Toward improved accuracy in nanomechanical measurements with Atomic Force Microscopy

B. Pittenger, S. Hu, J. Mosley, L. Huang, J. He, P. Dewolf
Bruker Corporation,
United States

Keywords: nanomechanical measurements, AFM

Summary:

The morphology and mechanical properties of sub-micron features in materials are of interest due to their influence on macroscopic material performance and function. Atomic Force Microscopy has the high resolution and force control to directly probe the mechanical properties of a wide range of these materials. Over the past two decades, several AFM based methods have evolved to allow this sort of mechanical mapping, each with specific strengths. These methods can be roughly divided into resonant modes (like TappingMode and Contact Resonance) and non-resonant modes (like Force Volume and PeakForce Tapping). In particular, researchers have begun to take advantage of the wide range of deformation rates accessible to AFM in order to study time dependent properties of materials such as viscoelasticity. More traditional measurements with indentation DMA are usually limited in frequency to a few hundred Hz and have limited spatial resolution. In contrast, AFM measurements can extend from less than one Hz to kHz and beyond while retaining the high resolution needed to see the details in distribution of properties near domain boundaries in nanocomposites and other materials. While qualitative maps have long been available, much progress has been made toward increasing the repeatability and accuracy of the mechanical property maps. Improved modeling, better calibration, and more optimal probe design have all contributed, resulting in relatively high accuracy with short time-to-data. This presentation will review this recent progress, providing examples that demonstrate the dynamic range of the measurements, their repeatability, and the speed and resolution with which they were obtained. Examples cover the range from very soft biomaterials and cells, through polymer blends and composites, to metals and ceramics.