Gas-assisted microfluidic step-emulsification for generating micron- and submicron-sized droplets.

Area of Science:

• Microfluidics
• Emulsification science
• Biomedical engineering

Background:

• Micron- and submicron-sized droplets are crucial for biomedical diagnosis and drug delivery.
• Existing microfluidic coflow step-emulsification methods face limitations in droplet size control and production rates, especially for viscous fluids.
• The droplet diameter is constrained by microchannel height, and production rates are limited by the capillary number.

Purpose of the Study:

• To develop a novel gas-assisted coflow step-emulsification method for enhanced droplet generation.
• To overcome the limitations of traditional all-liquid biphasic step-emulsification.
• To achieve higher production rates and emulsify highly viscous liquids.

Main Methods:

• A gas-assisted coflow step-emulsification technique was developed using a hollow-core air/oil/water emulsion.
• Air, as the innermost phase, diffuses out, leading to the formation of oil droplets.
• The method utilizes the scaling laws of triphasic step-emulsification for droplet size control.

Main Results:

• The novel method achieved minimal droplet sizes unattainable with standard biphasic methods, reaching $$.
• Production rates per channel were an order of magnitude higher than standard methods and superior to alternatives.
• The technique successfully generated micron- and submicron-sized droplets from high-viscosity fluids due to low gas viscosity.

Conclusions:

• The gas-assisted coflow step-emulsification method offers a versatile and efficient approach for producing uniform micron- and submicron-sized droplets.
• This method significantly improves production rates and expands the applicability to highly viscous fluids.
• The technique holds promise for advancing applications in biomedical diagnosis and drug delivery.