Strength in numbers: probing and understanding intermolecular bonding with chemical force microscopy

Scanning probe microscopy (SPM) provided researchers with a simple, intuitive, and versatile tool for probing intermolecular interactions using SPM probes functionalized with distinct chemical species. Chemical force microscopy (CFM) was developed as a way to probe and map these interactions in a rational and systematic way. But does the rupture strength of a bond measured in these experiments provide the definitive and useful information about the interaction? The answer to this question is closely linked to understanding the fundamental physics of bond rupture under an external loading force. Even a simple model shows that bond rupture can proceed in a variety of different regimes. I discuss the approaches for extracting quantitative information about the interaction from these experiments and show that even though the measured rupture force is almost never unique for a given bond, force spectroscopy measurements can still determine the essential interaction parameters.