Extending the surface force apparatus capabilities by using white light interferometry in reflection

Abstract

An important factor in the success of the surface force apparatus ͑SFA͒ in measuring interactions between surfaces over nanometer separations has been the optical interference technique used to measure the surface separation. Until recently, this technique has only been used when both of the materials are transparent. As a result, thin sheets of mica have been the material of choice. We describe a simple method to extend the capabilities of the SFA so that a wide variety of material surfaces can be studied while retaining an optical measurement technique. The key to this technique is to modify the optics so that reflected, rather than transmitted, light is used to produce the interference pattern. Now, only one material is required to be thin and transparent while the other can be any material providing it is at least partially reflective. To succeed with this technique, it is necessary to maximize the visibility of the interference fringes. This is achieved by optimizing the thickness of a partially reflective coating ͑often silver͒ deposited on the back side of the transparent material.

In situ nano- to microscopic imaging and growth mechanism of electrochemical dissolution (e.g., corrosion) of a confined metal surface

“…Moreover, pure roughening leaves the FECO fringe wavelength position unchanged (because the average surface height does not change), yet the width of a FECO fringe increases proportionally with the rms roughness. As of now, the setup is restricted to corroding thin films studied in transmission mode; extensions to bulk samples are easily possible using reflection mode interferometry (27).…”

A general contact mechanical formulation of multilayered structures and its application to deconvolute thickness/mechanical properties of glue used in surface force apparatus

“…However, Connor and Horn [21] modified the SFA to allow FECO to be observed in reflected light. This configuration still requires one of the contacting surfaces to be a thin transparent solid, but allows the other one to be replaced by a bulk material, which can be opaque.…”

“…The details of the SFA modified to measure FECO in reflected light have been described by Connor and Horn [21]. For the indentation experiments reported here, the arrangement consists of a thin partially silvered mica sheet glued to the bottom of a glass window, with a spherical glass indenter pressed up against the mica from below (i.e., an inverted system compared to the usual indentation arrangement shown in Fig.…”

Fluid drop shape determination by the Rayleigh--Ritz minimization method

“…For an unstressed drop, Figure 2 shows the profiles obtained with the Rayleigh-Ritz method, for increasing amount of correction terms, using the exponential basis functions defined in (10). The inset is a plot of the difference between exact and approximated drop profiles, z sph (r) − z rr (r), where z rr (r) is the Rayleigh-Ritz solution (4).…”

“…During the past few years there has been growing experimental [1,2,3,4,5,6,7,8,9,10,11] and theoretical [12,13,14,15,16,17,18,19,20,21,22], interest in systems where deformable surfaces interact with colloidal particles in liquids. These systems are important as they commonly appear in both nature and in technical situations.…”