Hollow porous silica microcapsules have emerged as critical materials for applications in bottom-up nanostructure fabrication¹, controlled drug delivery², and catalysis³. In the context of this study, we create these microcapsules and use them to controllably synthesize silicon nanowires with programmable optical and electromagnetic properties using a scalable, bottom-up method known as the Geode Process⁴. However, achieving precise size control and uniformity remains challenging, particularly when using conventional batch emulsification systems where imperfect mixing limits reproducibility. Membrane emulsification systems present a promising alternative, yet studies reporting particle-stabilized double emulsions within this context are scarce.
In this work, we introduce a membrane emulsification technique for producing particle-stabilized water-in-oil-in-water (W/O/W) double emulsions, which serve as templates for the controlled synthesis of hollow porous silica microcapsules. These microcapsules are subsequently used in a scalable bottom-up process to synthesize silicon nanowires, as aforementioned. Here, we systematically investigate how the flow rates of the continuous phase (CP) and dispersed phase (DP) influence droplet formation–identifying the CP/DP flow ratio as a key parameter. Our results show that higher CP/DP flow ratios yield smaller droplets with reduced polydispersity which demonstrates precision in droplet size control. This membrane emulsification approach offers a scalable and reproducible pathway for fabricating uniform hollow porous silica microcapsules, enhancing their applicability in advanced material applications.
