Modular microfluidics for double emulsion formation.

For many engineering applications such as manipulating two phase flows, generating single and double emulsions, and passively propelling liquids through channels, control over the surface energy of microfluidic channels is essential. In particular, double emulsion formation, which benefits from alternating hydrophobic and hydrophilic sections of channel, represents a challenge in fabricating controlled microfluidic channel surface properties. As double emulsions find further applications in single-cell handling and analysis, straightforward methods for generating them increase in value. Here, we present a method for generating double emulsions in microfluidic channels fabricated from modular fluidic blocks. By using a vapor-phase polymer coating technology-initiated chemical vapor deposition-we are able to fabricate blocks with varying surface properties. Assembling these blocks together then creates step-like changes in surface energy within a microchannel.

Giant Lipid Vesicle Formation Using Vapor-Deposited Charged Porous Polymers.

In this study, we prepare giant lipid vesicles using vapor-deposited charged microporous poly(methacrylic acid- co-ethylene glycol diacrylate) polymer membranes with different morphologies and thicknesses. Our results suggest that vesicle formation is favored by thinner, more structured porous hydrogel substrates. Electrostatic interactions between the polymer and the lipid head groups affect vesicle yield and size distribution. Repulsive electrostatic interactions between the hydrogel and the lipid head groups promote vesicle formation; attractive electrostatic interactions suppress vesicle formation. Ionic strength and sugar concentration are also major parameters affecting the yield and size of giant vesicles. The presence of both ions and sugars in the hydration buffer results in increased vesicle yields. These results indicate that lipid-polymer interactions and osmotic effects in addition to the substrate morphology and surface charge are key factors affecting vesicle formation. Our data suggest that surface chemistry should be designed to tune electrostatic interactions with the lipid mixture of interest to promote vesicle formation. This vapor-deposited hydrogel fabrication technique offers tunability over the physicochemical properties of the hydrogel substrate for the production of giant vesicles with different sizes and compositions.