ABSTRACT
Chemical force microscopy addresses these problems by introducing chemical modification of the AFM probes [6, 8]. Well-defined chemical interactions are created by coating the interacting surfaces with self-assembled monolayers (SAMs) terminated with specific organic functional groups. Such modification transforms AFM from a tool for measuring interactions of silicon probes with surfaces to a tool for measuring specific well-defined chemical interactions [9]. Careful design of the probe coating can also help deal with contamination, control the number of interacting molecules, and even separate different types of interactions spatially. This review presents the progress in applying CFM techniques for measuring equilibrium and time-dependent force profiles of molecular interactions, which has led to a greater understanding of the origin of interfacial forces in adhesion. Measurements of force profiles with chemically modified probes are more appropriately termed 'chemical force spectroscopy' (CFS) (where the spectrum represents 'force versus probe-surface distance' dependence), while the term 'chemical force microscopy' (CFM) implies chemically sensitive imaging with such probes. While both names have been used interchangeably in the literature to describe the forcedistance experiments, we will use the above nomenclature to make the distinction.
