A Study On The Hydrophobic Force Measurements By Using AFM

This paper studied several fundamental problems on the measurement of hydrophobic force by using Atomic Force Microscope (AFM). The researches on the surface force measurements; especially the hydrophobic interaction forces by means of AFM during the past two decades were reviewed in the first chapter of this paper.The colloid probe. was prepared by three different methods, including the traditional glass bead adhesion method, the AFM mechanical modification of the cantilever tip method and the chemical etching method. Compared to the traditional small glass bead adhesion method, the chemical etching method was easy operation and helpful to reduce the hydrodynamic resistance during the hydrophobic interaction force curve measurement by AFM, especially fit for the unique demands of the hydrophobic force measurements by AFM. We also studied the one of the fundamental problems in the AFM force curve measurement—the calibration of the spring constant of AFM probe cantilever experimentally. Our results showed that if we used the Sader method as the cantilever calibration's benchmark, the relative calibration errors of the geometric method was at least 8%, and that the Cleveland method was about 3-5%. Considering the domestic experimental conditions, we suggested the Cleveland method for the calibration of AFM probe cantilever. In terms of our research results, we proposed and suggested "the adhesion force or the interface energy" as the at least one of the criterions of the hydrophobic interaction force curves measured by AFM.