Generation of High‐Order All‐Aqueous Emulsion Drops by Osmosis‐Driven Phase Separation

Abstract

Droplets containing ternary mixtures can spontaneously phase-separate into high-order structures upon a change in composition, which provides an alternative strategy to form multiphase droplets. However, existing strategies always involve nonaqueous solvents that limit the potential applications of the resulting multiple droplets, such as encapsulation of biomolecules. Here, a robust approach to achieve high-order emulsion drops with an all-aqueous nature from two aqueous phases by osmosis-induced phase separation on a microfluidic platform is presented. This technique is enabled by the existence of an interface of the two aqueous phases and phase separation caused by an osmolality difference between the two phases. The complexity of emulsion drops induced by phase separation could be controlled by varying the initial concentration of solutes and is systematically illustrated in a state diagram. In particular, this technique is utilized to successfully achieve high-order all-aqueous droplets in a different aqueous two-phase system. The proposed method is simple since it only requires two initial aqueous solutions for generating multilayered, organic-solvent-free all-aqueous emulsion drops, and thus these multiphase emulsion drops can be further tailored to serve as highly biocompatible material templates.

Non-associative phase separation in an evaporating droplet as a model for prebiotic compartmentalization

“…A single-phase mixture of PEG and dextran, which has been extensively studied in our previous work, [38][39][40][41] is prepared and used as the stock solution for non-associative phase separation. To achieve the NES required for LLPS, a droplet extracted from the stock solution is pipetted onto a glass slide and starts to evaporate.…”

“…In our model system, both dextran-rich and PEG-rich domains nucleate quickly at the rim of the droplet due to phase separation. However, since PEG is more hydrophobic than dextran 48 and can adsorb onto silica, 49 the dextran-rich compartments, though with a higher density than PEG-rich phase, 38 are advected to the inner part by the fluid flow and PEG-rich compartments stay outside the sessile droplet, as suggested by the SEM images of the deposits (SI Appendix, Fig. S1).…”

Exploring New Horizons in Liquid Compartmentalization via Microfluidics

“…Higher order emulsions are difficult to generate using w/w microfluidics; only a few examples are known of higher-order emulsions. 65 − 68 Combining ATPS with classical w/o microfluidics makes it possible to increase the stability and complexity of the emulsions and obtain more flexibility in choice of materials.…”

Bioinspired perovskite quantum dots microfibers from microfluidics

“…The miniature and high-integrated microfluidic systems realize the coexistence, interactions, and reactions of diverse fluids in microchannels [30][31][32]. Thus, microfluidics is considered a simple but versatile fabrication tool for the efficient generation of functional materials like nanocrystals, microparticles, microfibers, etc., with controllable sizes, shapes, and designed features [33][34][35][36]. These nano-and micro-materials could find their significant application values and profound influences in different fields covering analytical applications, drug delivery, tissue engineering, and others [37][38][39][40].…”