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A direct, accurate and convenient procedure for calibrating the spring constants of probes used for force microscopy/spectroscopy is described. It amounts to deflecting an `unknown' cantilever with a `standard' lever, where the standard lever has been precalibrated. The absolute and relative accuracies of the procedure are - 30% and - 20%, respectively; the former is limited by uncertainties in the determination of the spring constant for the `standard' lever, as well as that for the `unknown'. The method differs from others of the static deflection variety by its exploitation of the routine features of current instruments. The technique is compared with other static and dynamic methods currently being used.

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The putative functions and functional efficiencies of periodic nanostructures on the surface of cicada wings have been investigated by atomic force microscopy (AFM) used as a tool for imaging, manipulation, and probing of adhesion. The structures consist of hexagonal close-packed protrusions with a lateral spacing of approximately 200 nm and may have multiple functionalities. Not only do the structures confer survival value by virtue of camouflage, but they may also serve as antiwetting and self-cleaning surfaces and thus be resistant to contamination. These effects have been demonstrated by exposure to white light, liquid droplets, and AFM adhesion measurements. The dependence of optical reflectivity and surface adhesion on surface topography has been demonstrated using AFM as a nanomachining tool as well as an imaging and force-sensing probe. The intact arrays display exceptionally low adhesion for particles in the size range 20 nm-40 microm. The particles can be removed from the array by forces in the range 2-20 nN; conversely, forces in the range 25-230 nN are required to remove identical particles from a flat hydrophilic surface (i.e., polished Si). Measurements of contact angles for several liquids and particle adhesion studies show that the wing represents a low-surface-energy membrane with antiwetting properties. The inference is that a combination of chemistry and structure constitutes a natural technology for conferring resistance to contamination.

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