Figure 1.

Examples of droplet generation techniques. (a) Co-flow. Experiment setup and schematic of a microfluidic chip for droplet generation. Variations in droplet size as a function of P_PEG at different P_DEX. Reprinted with permission from [68]. Copyright (2018) ACS publications. (b) A multi-inlet flow-focusing channel generator. The morphology of double-emulsion drops formed at different core–shell flow-rate ratios (scale bar: 20 μm). Image of the double-emulsion drops generated at flow rates of 200 μL/h (DEX-rich), 600 μL/h (PEG-rich), and 3000 μL/h (oil). Scale bar: 100 μm. Reprinted with permission from [69]. Copyright (2020) Springer Nature. (c) Thermal control. Schematic of the microfluidic droplet chip and integrated heating system. Endoskeletal droplets generated using this technique at a higher temperature (T > T_m) and a lower temperature (T < T_m). Reprinted with permission from [70]. Copyright (2022) Springer Nature. (d) Mechanical control. Image showing the manual operation of a pushbutton-activated microfluidic dropenser (PAMD) that generates and dispenses droplets. Image showing the droplets generated by the PAMD. Schematic of the composition of the single droplet generation channel and the pumping unit. Reprinted with permission from [71]. Copyright (2021) Elsevier.