Planar surface sliding

Figure 11.10 Two solids with parallel planar surface sliding over each other across a lubricating film.

Fig I. Geometries for the formation of an internal solid surface in volume samples Stacked planar glass slides, porous materials, nonporous colloidal particle dispersions, and densely packed colloidal particles. 

Sintered alumina (99,7%) bodies were used as stationary spherical (toroids with R = 21 mm and R = 21 mm) specimens with polished surfaces (Rpk= 0,019 pm), which were pressed against the planar surfaces of the rotating NbC. A normal force of 10 N was applied, resulting in an initial Hertzian contact pressure Pomm of approximately 660 MPa. The sliding distance was 5,000 m. Experiments were performed at 23°C and 400°C in air (rel. humidity at RT approx. 35%) with sliding speeds of 0.1, 0.3, 1.0, 3.0 and 7.5/8.0 m/s. The resolution limit of the wear rate for the rotating specimen corresponds to about 10 mm /N-m. 

Using a concentration jump as the perturbation, Sutherland et a/.(113) measured the kinetics of binding of fluorescein-labeled human IgG (present as an antigen in solution) to surface-immobilized sheep anti-human IgG. Two TIRF surfaces were used a planar slide and a fiber-optic cylinder. Also using a TIRF recovery after a concentration jump, Kalb et a/,(114) measured the slow ( 10 4 s 1) unbinding kinetics of anti-trinitrophenol (TNP) antibodies in solution and a TNP-derivatized lipid in a planar bilayer. 

The disadvantage of the nitrocellulose (NC) slide relates to resolution because biomolecules more easily diffuse from the surface than with planar arrays. Also, membranes suffer from considerable light scatter and higher intrinsic fluorescence, which are problematic for increased sensitivity. Membranes are better suited for detection of colorimetric or chemiluminescence reporters. Pall introduced a similar product, the Vivid GeneArray slide, based upon nylon-impregnated slides. 

The slide surface has to be planar, uniform, inert and accessible. Several materials can provide slides with these characteristics, but the glass surface is the most commonly used for fluorescent labeling, since most plastics do not permit the use of fluorescent dyes. Different glasses are available that are suitable for slide preparation (borosilicate, fused silica, etc.) and all are stable materials with low intrinsic fluorescence and reflectivity and an efficient transmission throughout the visible range. In order to allow the efficient... 

The planar waveguides are stored at room temperature under mild vacuum in three layer food saver bags using a FoodSaver (Vac360) from Tilia (San Francisco, CA). The transduction elements/reporter molecules are applied to the surfaces by incubating a porphyrin solution with the immobilized enzymes at pH 7. Application of the porphyrin to the immobilized enzyme surface has been suggested to adversely affect the slide lifetime [27] however, recent experiments have shown that AChE-porphyrin slides stored under mild vacuum as described are as sensitive and responsive as freshly made slide surfaces. 

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