Scalable fabrication of multiple emulsions via plasma-treated PDMS microfluidic devices

The significance of multiple emulsions lies in their capacity to serve as precision carriers that simultaneously encapsulate, protect, and co-deliver active substances, enabling critical functions including targeted delivery, sustained release, and enhanced ingredient stability. This study presents a scalable fabrication approach for preparing multiple emulsions via poly(dimethyl siloxane) (PDMS) microfluidic devices without requiring additional fluids or surface-modified coatings. We achieve controllable modulation of wettability on PDMS chip surfaces through localized plasma treatment following partial masking. Then, we successfully prepare single, double, and triple emulsions, demonstrating the scalability of this strategy for generating complex emulsions. Subsequently, using double emulsions as a model system, we systematically investigate the flow rate conditions required for their sustained generation. Finally, to achieve precise control over emulsion droplet size, we further explore the influence of flow rate parameters for the outer phase, middle phase, and inner phase on the size of double emulsions. This foundational work lays the groundwork for future research to optimize the preparation methods for multiple emulsions and develop stimuli-responsive systems for uses such as drug delivery and food preservation.