Probing near-surface nanoscale mechanical properties of low modulus materials using a quartz crystal resonator atomic force microscope.

We describe the development of a technique for making indentations on the top 5-20 nm of the surfaces of relatively low modulus materials using a high spatial and force sensitivity atomic force microscope (AFM) whose optical cantilever has been replaced by a quartz crystal resonator (QCR). Unlike conventional optical-cantilever-based AFMs, the accuracy of this technique is not compromised by the compliance of the loading system due to the high stiffness of the QCR. To obtain material modulus values from the indentation results, we find the commonly used Oliver-Pharr model to be unsuitable because of our use of a sharp tip and relatively deep indentation.

Using steered molecular dynamics simulations and single-molecule force spectroscopy to guide the rational design of biomimetic modular polymeric materials.

This article describes results on using steered molecular dynamics (SMD) simulations and experimental single molecule force spectroscopy (SMFS) to investigate the relationship between hydrogen bonding and mechanical stability of a series of homodimeric β-sheet mimics. The dimers consisting of 4, 6, and 8 H-bonding sites were modeled in explicit chloroform solvent and the rupture force was studied using constant velocity SMD. The role of solvent structuring on the conformation of the dimers was analyzed and showed no significant contribution of chloroform molecules in the rupture event.