Adhesion and short-range forces between surfaces. Part I: New apparatus for surface force measurements

Abstract

A new miniature Surface Forces Apparatus (SFA Mark III) is described for measuring the forces between surfaces in vapors and liquids. The apparatus employs similar techniques to those used in current SFAs, but it is easier to operate and is generally more user-friendly. Four stages of increasingly sensitive distance controls replace the three control stages of previous apparatuses. The first three stages allow for rapid manual control of surface separation to within 10 Å, while the fourth piezo-control stage has a sensitivity of better than 1 Å. All four distance controls have been specially designed to produce perfectly linear displacements of the surfaces. In addition, the SFA Mk III is more robust, less susceptible to thermal drifts, easier to clean, and requires smaller quantities of liquid than conventional SFAs. The high performance of this new instrument is illustrated in the succeeding paper (Part II), which describes the subtle effects of surface lattice mismatch on the oscillatory forces in water in the distance regime from 0 to 10 Å.