Background

The structure and mechanics of materials at the nanoscale a fundamental to understanding the functions of any system. Many of my publications are focused on pushing the bounds of our ability to measure and understand these nanoscale properties by novel methods of atomic force microscopy (AFM) nanomechanics. My work has enabled systematic characterization of viscoelastic nanoscale properties at higher frequencies, pushed the limits of AFM cantilever size by investigating novel cantilever detection methods, provided a framework to optimize detection sensitives in contact resonance AFM, and enabled systematic reconstruction of the distribution of force on an AFM cantilever. Faster and more accurate AFM nanomechanical measurements are the primary impact of this work.

Results

One of the most fundamental AFM nanomechanics measurements in an AFM force-displacement (FZ) curve. In a FZ curve the sample is ramped into the AFM tip. This causes the force between the tip and sample to increase. By recording both the sample position and force on the cantilever information about the sample nanomechanics can be extracted. An example of this is shown in the corresponding figure. In this case the force is applied to a cantilevered section of nanocrystalline cellulose. As the force increases the sample undergoes experiences a non-continuum kinking event where it plastically deforms into a new configuration. The AFM FZ curve enables us to quantify the force required to initiate this kinking behavior as approximately 20 nN.