Understanding Uniform, Fast, and Scalable Buoyancy-Driven Macro-Sized Drop Generations.

Generating uniform drops with fast production rate and tunable volume in a high-throughput way is important in various academic and industrial disciplines. In this study, we propose a strategy to produce milliscale drop in a size-tunable way and model its formation processes. The size of generated drops is uniform (<1% of the standard deviation) and tunable by controlling the flow rate, the pore diameter in membrane, and the surface hydrophobicity of membranes in the dripping regime. Also, their production rates range from ca. 0.1-2.1 Hz. The drop formation is successfully investigated by our five-force balance model. On hydrophobic membranes, the range of the dripping regime for uniform drops is wider (from ca. 5.7 to 10.4 mm) than that on hydrophilic membranes (from ca. 3.8 to 7.0 mm). Also, in the dripping regime in hydrophilic membranes, the production rates of the drop are faster than those of the hydrophobic membrane.