Microfluidic Fabrication of Stable Nanoparticle-Shelled Bubbles

Abstract

We introduce a microfluidic approach to generating monodisperse, stable nanoparticle-shelled bubbles using air-in-oil-in-water (A/O/W) compound bubbles as templates. The oil phase of the A/O/W compound bubbles comprises a volatile organic solvent and a hydrophobic silica nanoparticle. Upon evaporation of the organic solvent, the nanoparticles in the oil layer form a stiff shell at the air-water interface, which drastically enhances the stability of the bubbles against dissolution and coarsening. On the basis of this approach, we demonstrate that it is also possible to generate functional bubbles stabilized by composite shells that are composed of mixtures of hydrophobic materials and nanoparticles with unique properties.

Porous polymer particles—A comprehensive guide to synthesis, characterization, functionalization and applications

“…It is the elaborate chip design that allowed researchers not only to miniaturize microchannel emulsification reactors and prepare narrowly monodisperse spherical beads but also to achieve unprecedented control over structure and shape of particles. This unique capability of control resulted in the realization of perfectly controlled multiple emulsions [136][137][138][139][140][141][142][143][144][145], Janus particles [146][147][148][149][150][151][152][153][154][155][156], regular nonspherical shapes [157][158][159][160][161][162][163][164][165][166] and even gas bubbles [167][168][169][170][171], almost all of which were impossible to achieve before.…”

Formation of Polymeric Hollow Microcapsules and Microlenses Using Gas-in-Organic-in-Water Droplets

“…However, it was essential to match the generation rate and pitch of the droplets and the method often produced relatively thick shells. In contrast, Luo et al [28][29][30] and Lee et al [31][32][33] reported droplet formation methods using three-dimensional glass capillaries. They used a separated serial or simultaneous droplet generation structure to form core and shell layers.…”

“…Highly uniform microcapsules have been formed in miniaturized devices, and the functionality of these microcapsules has expanded as a result of new developments in microcapsule synthesis [22][23][24]. Formation of hollow microcapsules by direct injection of a gas into the capsule core is of particular interest [25][26][27][28][29][30][31][32][33][34]. Since the inner cavity and shell layer are formed directly in this technique, the number of materials available for capsule synthesis was significantly increased compared with single emulsion techniques using self-assembly or interfacial polymerization of the shell layer [35][36][37].…”

On-chip synthesis of silica nanoparticle assemblies with controlled shape and size

“…Few research articles show the synthesis of inorganic microparticles from sol precursors in droplets [9,10]. Others showed the assembly of inorganic nanoparticles at the surface of microdroplets to create hollow capsules that can, for instance, comprise and release drugs [11][12][13][14].…”

“…In previous studies, cohesion between the nanoparticles in the assembly was assured either by van der Waals forces [2,17], hydrophobic interactions between functionalized nanoparticles [14], adsorbing polyelectrolytes on the assembly [13], cross-linking the nanoparticles with reactive molecules [18] or embedding the nanoparticles in an organic photopolymerizable matrix [19].…”