Triple emulsion

An emulsion in which the dispersed droplets themselves contain even more finely dispersed droplets of a separate phase. Thus, there can occur oil-dispersed-in-water-dis-persed-in-oil (O/W/O) and water-dispersed-in-oil-dis-persed-in-water (W/O/W) multiple emulsions. These emulsions are sometimes called three-phase emulsions , triple-phase emulsions , or simply triple emulsions . More complicated multiple emulsions such as O/W/O/Wand W/O/W/O are also possible. 

FIGURE 20.13 Examples of multiple emulsions formed in microfluidic systems (a) multiple shells-multiple cores configurations of monodisperse triple emulsions made with cascaded microcapillary devices results. (Reproduced with permission from Utada, A.S. et al.. Bull. MRS, 32(09), 702, 2007.), (b) composite emulsion formed by droplets of different composition and different volumes. (Reproduced with permission from Hashimoto, M. et al.. Small, 3(10), 1792, 2007.), and (c) examples of anisotropic particles formed by either polymerization (spheres and disks, rods) of droplets of monomer or thermal setting of droplets. (Reproduced with permission from Xu, S. et al., Angew. Chem. Int. Ed. Engl, 44(5), 724, 2005.)... 

A distinct advantage of the coaxial capillary approach is in the surface treatment of the device both W/O/W and O/W/0 emulsions can be formed without any surface modification ofthe capillaries, because neither the middle nor the inner fluid touches the capillary wall surface. This is clearly different from the other techniques mentioned above in this section. An additional advantage is the flexibility of the system. For example, the structure ofthe device can be easily modified to make higher order multiple emulsions, such as triple emulsions [100, 101]. 

Double emulsions (or in more general terms, multiple emulsions) are droplets of one kind of fluid that are encapsulated inside drops of a second fluid (or themselves can be encapsulated inside droplets of yet another fluid). Conventionally, double emulsions are produced using shear cells or porous membrane plates however, the distributions of sizes of primary droplets and double emulsion droplets are poorly controlled. For multiple emulsions (triple emulsions or droplets), the polydispersity makes the methods impractical. Microfluidic sequential emulsification offers the ability to produce double (and multiple) emulsions with narrow polydispersity and controlled structure [59,60]. 

Utada et al. (2005) fabricated a microfluidic device with glass microcapillaries to prepare triple emulsions of a W/OAV/O type, such as water/siUcon... 

Figure 6.14 Microcapillary devices for generating monodisperse emulsions from coaxial liquid jets. This approach allows single-, double-, or triple emulsion droplets to be generated in a single step (Weitz).

Figure 6.15 Preparation of asymmetric vesicle from a triple emulsion using microfluidic device shown in Figure 6.14a (Weitz).

The most common multiple emulsions reported in the literature are of W/ OAV type, but in some specific apphcations O/W/O emulsions can also be prepared. The terms multiple emulsion, double emulsions, and triple emulsions were used in the past to describe these systems. A more suitable and more... 

It is assumed that the crystallization behavior of milkfat is different between emulsion and bulk, and the lack of nucleation centers in the emulsion droplets may delay the nucleation, making less stable a form nucleated in the first. The occurrence of multiple forms of double-chain-length and triple-chain-length structures may be caused by segregated crystallization of multicomponent TAGs exhibiting complicated mixing behavior, but its details are open to fumre study. 

Double- and Triple-Shaft Mixers The planetary mixer is an example of a double shaft mixer. However, many different combinations of mixing actions can be achieved with multi-shaft mixers. One variation on planetary motion involves replacing one anchor-style impeller with a high-shear impeller similar to the one shown in Fig. 18-47. The high-shear mixer can be used to incorporate powdered material effectively or create a stable emulsion leading to a final batch of viscous paste or fluid. 

The formation of emulsions is an important event in an oil spill. First, and most importantly, it substantially increases the actual volume of the spill. Emulsions of all types contain about 70% water and thus, when emulsions are formed, the volume of the oil spill more than triples. Even more significantly, the viscosity of the oil increases by as much as 1000 times, depending on the type of emulsion formed. For example, an oil that has the viscosity of a motor oil can triple in volume and become almost solid through the process of emulsification. 

Research sponsored by the government and private corporations has contributed much to the understanding of fundamentals that govern the complex process of emulsion polymerization. Emulsifiers play the triple role of emulsifsdng the monomers, furnishing micelles which are the sites of polymer initiation, and stabilizing the latex during the polymerization and afterward. To obtain satisfactory rates of polymerization at low tem-... 

Figure 5 The original skin care formulation (x) is an emulsion, but the final state (area to the right of the triple lines) strongly depends on the surfactant/oil ratio, //em = microemulsion.

One future prospect for microfluidic control will be the development of tailor-made vesicles with more complex geometries, triple, quadruple, multiple emulsions and artificial cells (artificiells), i.e. liposomes containing hposomes with each a different functionality, closely mimicking a biological cell structure, all designed for optimal performance for the specific function demanded from the vesicle. Double emulsions had already been made in a microfluidic device in a very controlled way [60, 61] (Figures 19.7 and 19.8). The number of secondary droplets inside the primary droplet... 

Also called Triple-Phase Emulsion. See Multiple... 

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