IMPLICATIONS OF HYDROPHOBIC SLIPPAGE FOR THE DYNAMIC MEASUREMENTS OF HYDROPHOBIC FORCES

It has previously been shown that capillary measurements may be interp reted in favor of hydrophobic slippage. Here, the possible implication s of this phenomenon for using the drainage technique for hydrophobic attractive force measurements are studied numerically. Attention is fo cused on investigating the role of various experimental conditions in the surface force apparatus. We demonstrate that under experimental co nditions discernible deviations from the Reynolds theory may occur due to slippage. The misuse of Reynolds theory may lead to overestimation of the hydrophobic attractive force. We conclude that the apparent ex tra attraction has to depend on both the parameters of the surface for ce apparatus (configuration geometry, stiffness of the spring, and dri ving speed) and the types of surface interactions in the system. Appar ently the only possibility of distinguishing between deviations from D LVO theory and deviations from Reynolds theory is to perform the drain age rate measurements at various driving speeds. However, sometimes th e effect of slippage will be undistinguishable from that of the hydrop hobic force, because the apparent hydrophobic force will be nearly ind ependent of the driving speed.