Imaging probes liquid environments

Studies on fundamental interactions between surfaces extend across physics, chemistry, materials science, and a variety of other disciplines. With a force sensitivity on the order of a few pico-Newtons, AFMs are excellent tools for probing these fundamental force interactions. Force measurements in water revealed the benefits of AFM imaging in this environment due to the lower tip-sample forces. Some of the most interesting force measurements have also been performed with samples under liquids where the environment can be quickly changed to adjust the concentration of various chemical components. In liquids, electrostatic forces between dissolved ions and other charged groups play an important role in determining the forces sensed by an AFM cantilever. 

Experimental details have been described at length in references (P), (10), and (11). Force-distance measurements and lateral-force imaging were performed with a scanning probe microscope (Nanoscope III Multimode, Digital Instruments, USA) equipped with a liquid cell and enclosed in a thermally equilibrated environment. Silica-coated tips were prepared by oxygen-plasma treating SiaN4 Microlevers (Park Scientific Instruments, USA). 

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