Water in Oil Emulsions
Water in oil emulsions (W/O) form the basis manufacturing techniques widely used in the industrial and R&D environments to manufacture droplets (e.g., for compartmentalization applications), hydrogel beads (e.g., alginate, agarose, or polyacrylamide), and polymer beads (e.g., acrylic, vinyl, and ethyl-based). Of particular importance is the ability to produce high-quality, monodisperse droplets and the ability to do so reproducibly and at a viable production rate.
The combination of Fluigent pressure pump units and Raydrop microfluidic devices developed and manufactured by Secoya enable smooth fluid delivery, precision flowrate control, automation, and reproducibility necessary to generate high-quality water in oil emulsions.
Materials and methods
Reagents
Droplet Phase: Water (Mili Q)
Continuous phase: Decane + 2% (wt) SPAN 80
| Reagent | Supplier | Catalogue number | CAS Number |
| Water | Ultrapure 18.2 MΩ – cm | – | 7732-18-5 |
| Decane | Sigma Aldrich | D901 | 124-18-5 |
| SPAN 80 | Sigma Aldrich | 8.40123 | 1338-43-8 |
Microfluidic Setup
The microfluidic setup was composed of:
Protocols steps
Results
| Continuous phase flowrate (μl/min) | Droplet phase flowrate (μl/min) | Droplet diameter (μm) | Production rate (Hz) |
| 100 | 5 | 71 | 445 |
| 100 | 10 | 75 | 754 |
| 100 | 15 | 87 | 725 |
| 50 | 5 | 85 | 259 |
| 50 | 10 | 91 | 422 |
| 50 | 15 | 92 | 613 |
| 25 | 5 | 89 | 225 |
| 25 | 10 | 93 | 396 |
| 25 | 15 | 94 | 575 |
| 15 | 15 | 94 | 575 |
Figure 4: Images of water droplets in decane generated using Fluigent equipment and Raydrop microfluidic device
Conclusion
Fluigent pressure based flow controller units and Raydrop microfluidic device were successfully used to generate high-quality, monodisperse droplets of water in hydrocarbon oil. The droplet size was controlled in the range of 75 – 94 μm by adjusting the continuous and dispersed phase flowrates. Peak stable droplet production rate was recorded for 75 μm droplets at 754 Hz. The production techniques developed here can be extended to the generation of hydrogel, protein, or polymer beads by adding appropriate post-processing steps