Static contact angle liquid-solid system

It has been known in the literature for a long time that there are three measurable contact angles, 6, Ga, and Gr for a given liquid-solid system [17-19], The static... 

At present, when working with high-purity materials, smooth solid surfaces and low P02 atmospheres, the thermodynamic contact angle in a particular system can be determined at best within about five degrees. Roughness must be very low, particularly in non-wetting systems in order to obtain such an accuracy. The control of P02 is critical for oxidisable liquids and solids, specially at relatively low temperatures, and dynamic vacuum is often preferable to a static neutral gas atmosphere. 

The energy of the system illustrated in Fig. 4 is calculated when the two-dimensional meniscus attaches to the horizontal plate at macroscopic contact angle 6. S, V, and L in the figure indicate the solid, vapor, and liquid phases, respectively. The coordinates x and z are taken to be the horizontal and vertical directions, respectively. The geometry of the meniscus can be obtained from the solution of Laplace equation (2). The radius of curvature is estimated from differential geometry. Considering the static pressure due to gravitation as AP, Eq. (2) is rewritten for the two-dimensional case as [2]... 

For a static system, solid surface interfacial tensions can be calculated from the measured contact angles by using a mechanical equilibrium relation derived by Young in 1800 [38]. The liquid droplet contact angle on any solid surface can be defined by the mechanical equilibrium of the droplet under the action of three interfacial tensions. The interfacial tension a ij is defined as the amount of work that must be performed in order to separate a unit area of fluid j from k. The term aj is the surface tension between substance j and its own vapor phase (Figure 5.28). The work to separate two phases is expressed as... 

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