Capillary bridges

H. Schubert, Kapillaritat in porosen Systemen, Springer (1982). (Emphasis on capillary bridges in porous systems, static and dynamic systems, wetting and dewetting. The book was primarily intended for engineers.)... 

Figure 5.46. Junctions between particles by capillary bridges.

Capillary bridges can also be created in liquid systems. Let, in the same fig., A be water and the hatched immiscible liquid be an oil. Then an attraction is created between the particles and this has to compete with the disjoining pressure. In practice the phenomenon is used by adding an oil as an agglomeration aid to coagulate slurries of hydrophobic particles, such as coal tailings. 

Chemical Properties of Aerosols. Surface chemical properties of aerosol particles can also be tailored to improve deaggregation [273]. Hygroscopic particles absorb water when inhaled into the humid airways [282-284], increasing particle size and density in the process, as well as creating the potential for capillary bridge formation between particles. Hygroscopic growth can be reduced by the use of hydrophobic additives [285] or compounds with low aqueous solubility [286,287]. 

FIGURE 5.9 Concave (a) and convex (b) capillary bridges between two parallel plates. and Pj denote the pressures inside and outside the capillary bridge, is the radius of its section with the midplane is the radius of the three-phase contact lines. 

In summary, it is more likely that two different effects are called hydrophobic interaction (1) the known molecular hydrophobic effect, - which could bring about a relatively short-range attractive surface force,and (2) formation of capillary bridges-cavities between two hydro-phobic surfaces. For now, there is sufficient evidence showing that both effects exist in reality, often in interplay with each other. 

Civ s3mometry 118 C2v synunetry 122 calcunitic nematic 74 cantilever elastic const mt 60 cantilever instability 69 capillary attraction 59 capillary bridge 51 capillary condensation 51,53, 56,190, 225... 

The typical pull-in step in the measured force curve is a consequence of a sudden capillary condensation, which occurs at a certain separation for a given temperatmre. At the moment of capillary condensation, a tiny capillary bridge of the nematic phase is formed between the apex of the sphere and the flat substrate. Since there is a capillary pressure across the curved isotropic-nematic interface, a strong force between both surfaces is observed. The separation dependence of the capillary force can be analyzed within the LdG formalism [21] and fits very well to the experiment. 

Most common fluidic grippers use capillary bridge cOTifiguration. Surface energy minimization results in a finite contact angle between the liquid and the solid surface which is defined by Young s equation (Fig. 1) ... 

Fluidic Assembly, Fig. 2 A capillary bridge with the principle radii of curvature illustrated... 

Another effect of surface tension can be observed from the physical shape of the capillary bridge. The Laplace pressure (AP) is expressed as... 

This section draws on the work of Laplace published in 1805. Surface tension is at the origin of the overpressure existing in the interior of drops and bubbles. This pressure difference has multiple consequences. For instance, smaller drops will disappear in favor of larger ones in an emulsion, and they will be the first to evaporate during the cooling phase of an aerosol. The pressure difference also explains the phenomenon of capillary adhesion between two plates, between hairs or fibers, or in wet sand, all of which are induced by capillary bridges. 

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