Substrate liquid film configuration

In the substrate-liquid film configuration of Figure 2.3, the interfacial deformation at a distance r from an isolated spherical particle in the small-deformation limit is Mjso,(r) = qJ2ny)KQ rl K), with... 

Figure 6-1. A sketch of the generic thin-film configuration for a liquid film on a solid substrate that is tilted to an angle a from the horizontal. The upper surface of the film is an interface.

The liquid is poured onto the substrate, put into a press configuration where a plate is placed on top of the liquid film, and pressed down onto spacer shims located between the substrate and plate (i.e., to control the final film thickness)... 

FIGURE 7.1. The dewetting process has been studied in three different geometries (a) supported films resting on a solid substrate. The process controls the spontaneous drying out of liquid films without the intervention of heat, as well as the stability of liquid films (b) inserted films, sandwiched between a rubber-like material and a solid, with applications to the process of adhesion onto a wetted solid surface and to the stability of the lachrymal film between a soft contact lens and the cornea (c) suspended viscous films (in air or in a liquid with low viscosity) this configuration controls the stability of polymer and glass foams as well as that of emulsions. 

One of the primary differences between CVD (or in the case of polymers, commonly referred to, as chemical vapor polymerization or CVP) and other conventional deposition techniques, particularly for polymer thin films, is that CVD is a dry process. There is no liquid intermediate between the gas phase reactants and the resultant solid thin film and thus, problems due to surface tension such as pulling away from the corners, sharp edges etc, are not present. Additionally, CVD enables deposition of uniform thin films in recesses, holes and other difficult three dimensional configurations unlike solution based techniques which are limited to planar substrates. In the terminology of thin film device fabrication, CVD films have excellent gap-filling and step coverage characteristics. 

There has been considerable interest in recent years in the formation of condensed films of purine and pyrimidine bases at the solid-liquid interface. It is well recognised that non-covalent affinities between base pairs play a prevalent role in determining nucleic acid conformation and functionality. Likewise, there has been interest in the role of substrate and non-covalent intermolecular interactions in the configuration of ordered monolayers of purine and pyrimidine bases. There is also more general interest in the interaction of bases with metal surfaces and metal complexes. In the latter case it is noted that the biological role of nucleic acids and certain nucleotides are dependent on metal ions, particularly Mg, Ca, Zn, Mn, Cu and Ni. " Also certain metal complexes, notably of platinum, have the anti-tumour activity, which is linked to their ability to bind to bases on DNA. On a different note, the possibility that purine-pyrimidine arrays assembled on naturally occurring mineral surfaces might act as possible templates for biomolecular assembly has been discussed by Sowerby et al. 

The intrinsic structure of a liquid-vapor interface resembles the surface of a polymer liquid in contact with a nonattractive solid substrate at the pressure where the liquid coexists with its vapor. In the latter case, the system is in the vicinity of the drying transition and a layer of vapor intervenes between the substrate and the polymer liquid. There is, however, one important difference between the vapor-polymer interface and the behavior of a polymer at a solid substrate the local position of the interface can fluctuate. Let us first consider the case where the film is very thick and the solid substrate does not exert any influence on the free surface of the film in contact with its vapor. The fluctuations of the free surface are capillary waves. Neglecting bubbles or overhangs, one can use the position of the liquid-vapor interface, z = h x,y), as a function of the two lateral coordinates, x and y, parallel to the interface to describe the system configuration on a coarse scale. In this Monge representation, the free energy of the interface is given by the capillary-wave Hamiltonian " ... 

Smooth substrates include crystal and glass surfaces, and polymer films. The direct influence of such a substrate on the liquid crystal is limited to the molecules in the surface layer and is due to the short-range interaction of these molecules with the substrate (Fig. 4a). Once these microscopic anchoring conditions are known, the configuration of the rest of the liquid crystal (in particular the orientation of the director outside the interfacial region) can be determined from the properties of the liquid crystal regarding propagation of orientational order. 

The final constant chemical potential configuration considered represents a film of alkane melts sandwiched between two solid plates in Refs 27 and 28. The system was periodic in the x and y directions, but only a portion of the surfaces in the y direction was occupied by the solid substrate. Constant chemical potential was maintained using the reservoir method, where the liquid bubbles which form at the edge of the substrates are in equilibrium with a vapor phase which interacts across the periodic boundaries. The surfaces were modeled as static surfactant crystalline monolayers which interacted with the alkanes as united atom CH2 and CH3 groups (weakly attractive surface). Both /i-octane and 2-methylheptane systems were studied as a function of surface separation. 

Constant pressure, or external load, systems have been studied in Refs 29 and 32. In Ref. 29, -hexadecane melt films in a semidfoplet configuration were considered, where the surfaces and liquid were periodic in the x direction but limited in extent in the y direction, with the entire substrate being occupied in the x direction but only partially occupied in the y direction. 

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