Microfluidic fabrication of water-in-water (w/w) jets and emulsions

Abstract

We demonstrate the generation of water-in-water (w/w) jets and emulsions by combining droplet microfluidics and aqueous two-phase systems (ATPS). The application of ATPS in microfluidics has been hampered by the low interfacial tension between typical aqueous phases. The low tension makes it difficult to form w/w droplets with conventional droplet microfluidic approaches. We show that by mechanically perturbing a stable w/w jet, w/w emulsions can be prepared in a controlled and reproducible fashion. We also characterize the encapsulation ability of w/w emulsions and demonstrate that their encapsulation efficiency can be significantly enhanced by inducing formation of precipitates and gels at the w/w interfaces. Our work suggests a biologically and environmentally friendly platform for droplet microfluidics and establishes the potential of w/w droplet microfluidics for encapsulation-related applications.

One‐Step Microfluidic Fabrication of Polyelectrolyte Microcapsules in Aqueous Conditions for Protein Release

“…[6] We use these transient W/W/W drops as templates to fabricate PE microcapsules based on the interfacial complexation of oppositely charged polyelectrolytes.R emarkably,t he shell thickness of PE microcapsules is nearly independent of the concentration and molecular weight (MW) of the polyelectrolytes.W eq uantify the release profile of the PE microcapsules for both neutral and charged molecules.I nterestingly,t he release of negatively charged molecules is significantly prolonged because of attractive electrostatic interactions.F inally,w ed emonstrate the application of PE microcapsules in encapsulation and release of platelet-derived growth factor-BB (PDGF-BB) without impairing its biological activities. [6] We use these transient W/W/W drops as templates to fabricate PE microcapsules based on the interfacial complexation of oppositely charged polyelectrolytes.R emarkably,t he shell thickness of PE microcapsules is nearly independent of the concentration and molecular weight (MW) of the polyelectrolytes.W eq uantify the release profile of the PE microcapsules for both neutral and charged molecules.I nterestingly,t he release of negatively charged molecules is significantly prolonged because of attractive electrostatic interactions.F inally,w ed emonstrate the application of PE microcapsules in encapsulation and release of platelet-derived growth factor-BB (PDGF-BB) without impairing its biological activities.…”

“…Herein, we report ao ne-step microfluidic fabrication of PE microcapsules in aqueous conditions.U nlike traditional methods that rely on organic-aqueous systems,w eu se two aqueous polymer solutions with ar elatively small interfacial tension, yet large enough to generate transient water-inwater-in-water (W/W/W) double emulsion drops. [6] We use these transient W/W/W drops as templates to fabricate PE microcapsules based on the interfacial complexation of oppositely charged polyelectrolytes.R emarkably,t he shell thickness of PE microcapsules is nearly independent of the concentration and molecular weight (MW) of the polyelectrolytes.W eq uantify the release profile of the PE microcapsules for both neutral and charged molecules.I nterestingly,t he release of negatively charged molecules is significantly prolonged because of attractive electrostatic interactions.F inally,w ed emonstrate the application of PE microcapsules in encapsulation and release of platelet-derived growth factor-BB (PDGF-BB) without impairing its biological activities.…”

All-aqueous multiphase microfluidics : from formation of liquid structures to synthesis of biomaterials

“…15,36,37 Stabilization of these emulsions is thus critical in both scientific studies and practical applications.…”

“…To prevent the coalescence of droplets, photocurable monomers such as PEGDA 15 or dextran-HEMA 34 have been added to the emulsion phase, and the fast photo-polymerization helps to solidify the emulsion within seconds. However, photo-polymerization typically generates toxic free radicals, potentially harming the encapsulated species, especially the living ones.…”

“…The approach of all-aqueous multiphase microfluidics will facilitate many biomedical studies that use ATPS as the medium, such as efficient molecular or cellular extraction, 13,14 and biomaterials synthesis. 11,15 In the following sections, we will separately discuss two basic fluidic structures formed by ATPS using microfluidic techniques: jets and drops.…”