Here we present a novel surface modification method based on the sequential layer-by-layer deposition of polyelectrolytes yielding hydrophilic microchannels in PDMS-based microfluidic devices. The coatings are long-term stable and allow for the generation of monodisperse oil-in-water microdroplets even several months after the channel surface treatment. Due to the robustness of the polyelectrolyte multilayers ultra-high flow rates can be applied, making high-throughput droplet formation in the jetting mode possible. Furthermore, we successfully used our method to selectively modify the surface properties in certain areas of assembled microchannels. The resulting partially hydrophilic, partially hydrophobic microfluidic devices allow for the production of monodisperse water-in-oil-in-water double emulsions.

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Abstract:Here we report the application of monodisperse double emulsion droplets, produced in a single step within partially hydrophilic/partially hydrophobic microfluidic devices, as defined containers for quantitative flow cytometric analysis. Samples with varying fluorophore concentrations were generated, and a clear correlation between dye concentration and fluorescence signals was observed.

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Electron beam lithography is a powerful technique for the production of nanostructures but pattern quality depends on numerous interacting process variables. Orthogonal gradients of resist composition, baking temperatures, and development time as well as dose variations inside writing fields are used to prepare ternary combinatorial libraries for an efficient stepwise optimization of a molecular glass negative tone resist system.