ABSTRACT
Skulason and Frisbie probed systematically [56] the relationship between the tip radius and force of adhesion, F a , measured in CFS of hydrophobic contacts (CH3/CH3) in water. For tip radii ranging from R = 15 nm to 125 nm, they observed a remarkably good linear correlation between mean F a and R. Moreover, when they also considered substrate roughness (radius of curvature of Au grains) in defining effective radius (equation (1)), the linear fit had a zero intercept, as expected from the predictions of contact mechanics models (Fig. 8). From the slope of the least-squares linear fit, 0.52 ± 0.05 N/m, and value for thermodynamic work of adhesion in the CH3 —H2O-CH3 system, 103 mJ/m2, one can derive the value of the coefficient in the equation for the force of adhesion, (1.59 ± 0.15)7T, very close to the 1.57T value of the JKR model.
