Droplets nano-scale

Surface switching coupled with geometric and potential asymmetry was used to cause directional motion of a droplet. Sophisticated design and active control of surface properties are important technology for motion control on the micro/nano-scales. 

The integrated DLS device provides an example of a measurement tool tailored to nano-scale structure determination in fluids, e.g., polymers induced to form specific assemblies in selective solvents. There is, however, a critical need to understand the behavior of polymers and other interfacial modifiers at the interface of immiscible fluids, such as surfactants in oil-water mixtures. Typical measurement methods used to determine the interfacial tension in such mixtures tend to be time-consuming and had been described as a major barrier to systematic surveys of variable space in libraries of interfacial modifiers. Critical information relating to the behavior of such mixtures, for example, in the effective removal of soil from clothing, would be available simply by measuring interfacial tension (ILT ) for immiscible solutions with different droplet sizes, a variable not accessible by drop-volume or pendant drop techniques [107]. 

Reverse micelles are self-organized aggregates of amphiphilic molecules that provide a hydrophilic nano-scale droplet in apolar solvents. This polar core accommodates some hydrophilic biomolecules stabilized by a surfactant shell layer. Furthermore, reverse micellar solutions can extract proteins from aqueous bulk solutions through a water-oil interface. Such a liquid-liquid extraction technique is easy to scale up without a loss in resolution capability, complex equipment design, economic limitations and the impossibility of a continuous mode of operation. Therefore, reverse micellar protein extraction has great potential in facilitating large-scale protein recovery processes from fermentation broths for effective protein production. 

An important common feature of macroion solutions is that they are characterized by at least two distinct length scales determined by the size of macroions (an order up to lOnm in the case of ionic micellar solutions) and size of the species of primary solvent (water molecules and salt ions, i.e. few Angstroms). Considering practical colloidal macro-dispersions, like foams, gels, emulsions, etc., usually we are dealing with as many as four distinct length scales molecular scale (up to lnm) that characterizes the species of the primary solvent (water or simple electrolytes) submicroscopic or nano scale (up to lOOnm) that characterizes nanoparticles or surfactant aggregates called micelles microscopic or mesoscopic scale (up to lOO m) that encompasses liquid droplets or bubbles in emulsion and foam systems as well as other colloidal suspensions, and macroscopic scale (the walls of container etc). 

A recent development in the production of polymer particles has created a revolutionary new technology for the production of submicron polymer particles from solution, In this experiment, generation and characterization of droplet streams with small (< 15 pm) average diameters have been used to create nano-polymer particles. This technique makes the initial volume of a dilute solution of any polymer material sufficiently small so that the solvent evaporation occurs on a very short time scale leaving behind a polymer particle. For micro and nano-scale generated polymer particles, the refractive index obtained from the data analysis is consistent with bulk (nominal) values and the level of agreement with Mie theory indicates that the particles are nearly perfect spheres. 

An emulsion is a mixture of two immiscible liquids, one of which is uniformly dispersed within the other as small droplets (i.e., droplet diameter in the range O.l-lOOpm) (McClements, 2005). In this chapter, the concern is exclusively with dispersions of oil in water, that is, oil-in-water emulsions. Advances in homogenizer technology have allowed the development of nanoemulsions with droplets far smaller and with more uniform size distributions than commonly seen in manufactured foods (Weiss et al, 2008). There is not a commonly accepted size cut-off for nanoemulsions and different researchers have used different definitions below lOOOnm (Muller et al, 2000), 500mn (Anton et al, 2008), 200nm (Higami et al, 2003 Solans et al, 2005), and lOOmn (Luykx et al, 2008). Emulsions with nano-scale crystalline droplets are sometimes referred to as solid lipid nanoparticles (SLN). 

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