Accurate friction measurement at nanoscale is critical in reliable micro- and nano-device design. Different values of coefficient of friction (COF) have been reported in the literature for the same material when different instruments and tip sizes were used. We have conducted a series of experiments to delineate the effects of different tip sizes and shapes on friction as a function of load and found that friction force values under the elastic contact regime for various tips can be unified when plotted against the tip cross-sectional area in the direction of sliding. This observation implies a volumetric dependence of friction that has not been reported before in the elastic regime.
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