Droplet elasticity

D.C. Morse and T.A. Witten Droplet Elasticity in Weakly Compressed Emulsions. Europhys. Lett. 22, 549 (1993). 

It is unexpected that the droplet would jump away from the surface when encountering the unpattemed strips, since the strips were measured to be more hydrophflic than the patterned squares. The high speed videos show that the unpattemed strips suddenly pulled a portion of liquid adhered to the smooth surface. In many cases, the droplet elasticity due to surface tension was overcome, resulting in a separated droplet. In other cases, the droplet pulled the adhered liquid back to the droplet until a sudden detachment (jumping) event from the surface. Cases where a detached droplet was propelled towards the meniscus due to surface tension forces acting on it or off the surface were observed when the adhered liquid was pulled towards the droplet but still pinched off. 

D. C. Morse and T. A. Witten. Droplet elasticity in weakly compressed emulsions. EPL (Europhysics Letters), 22(7) 549,1993. 

These fascinating bicontinuous or sponge phases have attracted considerable theoretical interest. Percolation theory [112] is an important component of such models as it can be used to describe conductivity and other physical properties of microemulsions. Topological analysis [113] and geometric models [114] are useful, as are thermodynamic analyses [115-118] balancing curvature elasticity and entropy. Similar elastic modulus considerations enter into models of the properties and stability of droplet phases [119-121] and phase behavior of microemulsions in general [97, 122]. 

G. Gompper, S. Zschocke. Elastic properties of interface in a Ginzburg-Landau theory of swollen micells, droplet crystals and lamellar phases. Euro-phys Lett 16 13 -136, 1991. 

The mechanism of droplet deformation can be briefly summarized as follows. The factors affecting the droplet deformation are the viscosity ratio, shear stress, interfacial tension, and droplet particle size. Although elasticity takes an important role for general thermoplastics droplet deformation behavior, it is not known yet how it affects the deformation of TLCP droplet and its relationship with the processing condition. Some of... 

Many other interesting examples of spontaneous reflection symmetry breaking in macroscopic domains, driven by boundary conditions, have been described in LC systems. For example, it is well known that in polymer disperse LCs, where the LC sample is confined in small spherical droplets, chiral director structures are often observed, driven by minimization of surface and bulk elastic free energies.24 We have reported chiral domain structures, and indeed chiral electro-optic behavior, in cylindrical nematic domains surrounded by isotropic liquid (the molecules were achiral).25... 

Kaiser, T. Roll, G. Schweiger, G., Investigation of coated droplets in an optical trap Raman scattering, elastic light scattering, and evaporation characteristics, Appl. Opt. 1996, 35,... 

J.-Z. Zhang, D. H. Leach, and R. K. Chang, Photon lifetime within a droplet Temporal determination of elastic and stimulated Raman scattering, Opt. Lett. 13, 270-272 (1988). 

It is probable that numerous interfacial parameters are involved (surface tension, spontaneous curvature, Gibbs elasticity, surface forces) and differ from one system to the other, according the nature of the surfactants and of the dispersed phase. Only systematic measurements of > will allow going beyond empirics. Besides the numerous fundamental questions, it is also necessary to measure practical reason, which is predicting the emulsion lifetime. This remains a serious challenge for anyone working in the field of emulsions because of the polydisperse and complex evolution of the droplet size distribution. Finally, it is clear that the mean-field approaches adopted to measure > are acceptable as long as the droplet polydispersity remains quite low (P < 50%) and that more elaborate models are required for very polydisperse systems to account for the spatial fiuctuations in the droplet distribution. 

A new variation of interfacial polymerization was developed by Russell and Emrick in which functionalized nanoparticles or premade oligomers self-assemble at the interface of droplets, stabilizing them against coalescence. The functional groups are then crosslinked, forming permanent capsule shells around the droplets to make water-in-oil (Lin et al. 2003 Skaff et al. 2005) and oil-in-water (Breitenkamp and Emrick 2003 Glogowski et al. 2007) microcapsules with elastic membranes. 

Microemulsions are dynamic systems in which droplets continually collide, coalesce, and reform in the nanosecond to millisecond time scale. These droplet interactions result in a continuous exchange of solubilizates. The composition of the microemulsion phase determines the exchange rate through its effect on the elasticity of the surfactant film surrounding the aqueous microdomains. Compared with nonionic surfactant-based microemulsions, AOT reverse micelles have a more rigid... 

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