More Than a Feeling

The atomic force microscope (AFM) is enabling engineers to understand mechanical systems at the most basic level. The heart of the AFM is a probe comprising a microfabricated cantilever with an extraordinarily sharp tip. The AFM tip can be thought of as a nanometer-scale finger that we have at our disposal to interface with matter on the scale of individual molecules, and even atoms. The paper highlights that it is the only instrument that allows us to ‘touch’ the surface of a sample with nanometer-scale resolution and atomic-level force sensitivity. Researchers using AFM have now established that after relatively weak bonds break, untying segments of a relatively large structural molecule, the energy needed to stretch the untied segment can be orders of magnitude larger than the broken bond's energy. The AFM has evolved into a highly modular instrument. Advanced AFMs such as the BioScope II from Veeco Instruments operate in liquid to image and probe biologically important matter, both organic and synthetic. Also, there are AFMs for operating in vacuum, useful in investigating properties of matter without a water layer adsorbed on it, or for probing tip-sample interactions with highly sensitive probes in long range or in contact.