Device for measuring the force and separation between two surfaces down to molecular separations

Abstract

We present an apparatus for measuring the force as a function of distance between surfaces at separations down to the order of molecular dimensions. The device is a simplified yet improved version of the surface force apparatus first developed by Israelachvili and Adams [J. Chem. Soc. Faraday Trans. 1, 74, 975 (1978)]. It gives the same measurement resolution and has the same possibilities of studying various phenomena in thin films such as friction, viscosity, adhesion, and phase transitions. It offers improved performance with regard to control of surface separation and increased versatility by virtue of variable chamber dimensions and geometry.

Long-Range Hydrophobic Forces between Mica Surfaces in Dodecylammonium Chloride Solutions in the Presence of Dodecanol

“…Since this area is substantially larger than Direct force measurements were carried out using a Mark that ( 0.20 nm 2 ) occupied by each hydrocarbon chain in IV surface force apparatus (from Anutech Pty. ), which is a close-packed monolayer, single-chain surfactants form described by Parker et al (21). Two molecularly smooth sparsely packed monolayers on mica.…”

Interactions between Adsorbed Layers of a Low Charge Density Cationic Polyelectrolyte on Mica in the Absence and Presence of Anionic Surfactant

“…Two types of setups were Two different approaches for the experiments were used. used, the Mark II type originally developed by Israelachvili In the first procedure solutions (20-25 ml) with different and Adams (30) and the Mark IV type designed by Parker polyelectrolyte concentrations were prepared and SDS was et al (31). Muscovite mica was obtained from Mica New added in small portions (50-100 ml) with a pipette (Brand York Corp. in New York (green mica) and from M. Wata-Transferpette digital, 250 ml) until flocculation occurred.…”

Conformational and Disorder to Order Transitions in Proteins: Structure / Function Correlation in Apolipoproteins

“…All these interactions depend on the kind of surface and solution where the proteins are immersed, as well as on their charge, shape, and conformation. The surface force apparatus (SFA) (Israelachvili, 1973;Parker et al, 1989) offers the possibility of measuring long-range and contact forces between two mica surfaces covered with adsorbed proteins (Claesson et al, 1995), as well as, measuring the absorbed layer thickness and its compressibility. The latter parameter can give information about the conformational structure and size of the adsorbed protein.…”

“…The SFA instrument and experimental procedures have been described by Israelachvili (Israelachvili & McGuiggan, 1990) and Parker (Parker et al, 1989). In general, the force is measured between two curved molecularly smooth mica surfaces (typically 1 cm 2 of area with 2-5 µm constant thickness) where a silver layer of about 520 Å thick was deposited through evaporation on one side of each surface.…”