We Measure Pull-off (Adhesion) Forces Using AFM and Analyze Them in Term of Surface Energy

Atomic force microscopy (AFM) is capable of characterizing solid surfaces at the microscopic and sub-microscopic scales. As demonstrated in several laboratories in recent years, it can also be used to determine the surface tension of solids based on adhesion (pull-off) force measurements. However, the experimental data presented in the literature indicate poor reproducibility of pull-off forces measured with the AFM technique. For AFM force measurements to ever become an accepted technique for particle-substrate adhesion characterization, individual problems causing irreproducibility of the measurement must be resolved.  Until this is performed, it will be uncertain as to the reasons behind the scattering of pull-off force data collected for almost any system.

We also measure the pull-off forces in very complex geometry systems that are of importance to the industry. For example, we measured adhesion forces between pharmaceutical particles with irregular geometry and polymeric surfaces of varying roughness in a gas of controlled humidity level.

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