Controlled Movement of Complex Double Emulsions via Interfacially Confined Magnetic Nanoparticles

Abstract

Controlled, dynamic movement of materials through noncontacting forces provides interesting opportunities in systems design. Confinement of magnetic nanoparticles to the interfaces of double emulsions introduces exceptional control of double emulsion movement. We report the selective magnetic functionalization of emulsions by the in situ selective reactions of amine-functionalized magnetic nanoparticles and oil-soluble aldehydes at only one of the double emulsion’s interfaces. We demonstrate morphology-dependent macroscopic ferromagnetic behavior of emulsions induced by the interfacial confinement of the magnetic nanoparticles. The attraction and repulsion of the emulsions to applied magnetic fields results in controlled orientation changes and rotational movement. Furthermore, incorporation of liquid crystals into the double emulsions adds additional templating capabilities for precision assembly of magnetic nanoparticles, both along the interface and at point defects. Applying a magnetic field to liquid crystal complex emulsions can produce movement as well as reorganization of the director field in the droplets. The combination of interfacial chemistry and precise assembly of magnetic particles creates new systems with potentially useful field-responsive properties.

Liquid Crystals in Curved Confined Geometries: Microfluidics Bring New Capabilities for Photonic Applications and Beyond

“…Allowing the precise assembly of antibodies . (B) Schematic representations of the magnetic response of the Janus emulsion orientation change and LC single droplets with bipolar and radial organizations . Adapted with permission from refs and .…”

Responsive drop method: quantitativein situdetermination of surfactant effectiveness using reconfigurable Janus emulsions

“…the droplet geometries can be controllably altered after emulsification by triggering changes in the surfactant effectiveness, 15,16 and examples of the latter include stimuli-responsive or cleavable surfactants. 17 Owing to this unique morphological response to targeted chemical stimuli, Janus emulsions have been exploited in a number of applications, including as tunable microlenses, 18 optical waveguides, [19][20][21] scaffolds for the fabrication of anisotropic solid objects, 22,23 motile particle systems, 24,25 and as transducers and signal amplifiers in improved chemo-and biosensing platforms. [26][27][28][29] Herein, we leverage the exquisitely sensitive chemicalmorphological coupling inside Janus emulsions for the development of a new simple and broadly applicable method for the quantitative characterization of surfactants.…”

Manipulating Dispersions of Magnetic Nanoparticles

“…Therefore, the interfacially jammed MNP layer induces the para-to-ferro magnetic transformation on oil-in-water emulsion droplets even with incomplete nanoparticles coverage. Zentner et al 47 placed ferromagnetic particles into double and Janus emulsion droplets (Figure 6c). Amine-functionalized MNPs, dispersed in the surrounding aqueous phase, were chemically grafted to one side of the double oil emulsion droplet surface by in situ imine formation at water/oil interfaces.…”