Electro-coalescence in step emulsification: dynamics and applications

Area of Science:

• Microfluidics
• Chemical Engineering
• Materials Science

Background:

• Step emulsification is a low-shear technique for producing monodispersed microdroplets.
• Controlling the coalescence of multiple components in step emulsification remains a challenge.

Purpose of the Study:

• To develop a method for controllable coalescence in step emulsification using low voltage.
• To investigate the interplay between electro-coalescence and fluid dynamics in droplet formation.
• To establish a semi-empirical model for predicting droplet size.

Main Methods:

• Utilizing a low voltage to influence the coalescence position of flow tips in a step microfluidic device.
• Conducting numerical simulations to analyze flow tip shape evolution and coalescence behavior.
• Developing a semi-empirical model correlating droplet size with flow rates and applied voltage.

Main Results:

• Demonstrated voltage-controlled coalescence of multiple fluid streams in step emulsification.
• Successfully avoided clogging issues in precipitate-producing reactions by triggering coalescence in a wider reservoir.
• Established a predictive model for droplet size based on experimental parameters.
• Showcased the potential for producing multilayered droplets due to the low-shear nature of the method.

Conclusions:

• The electro-coalescence approach offers precise control over droplet formation in step emulsification.
• This method addresses limitations of previous techniques, particularly in reactions prone to clogging.
• The developed model provides a valuable tool for optimizing droplet generation for various applications.