High-Throughput Aqueous Two-Phase System Droplet Generation by Oil-Free Passive Microfluidics

Area of Science:

• Biotechnology
• Microfluidics
• Biocompatible materials

Background:

• Aqueous two-phase systems (ATPS) offer biocompatibility for biological and medical uses.
• Generating ATPS droplets is challenging due to ultralow interfacial tension compared to water-in-oil (W/O) systems.

Purpose of the Study:

• To achieve passive, oil-free generation of ATPS droplets.
• To characterize droplet size and production rate in oil-free ATPS.

Main Methods:

• Passive droplet generation technique without oil or external forces.
• Analysis of flow rates and capillary (Ca) numbers in the jetting flow regime.
• Systematic variation of inlet pressures and flow rates to control droplet characteristics.

Main Results:

• Successfully generated ATPS droplets with radii as small as 7 μm at frequencies up to 300 Hz.
• Identified a capillary number range of 0.3-1.7 for passive ATPS droplet generation, confirming ultralow interfacial tension.
• Demonstrated independent control of droplet size and generation frequency via pressure and flow rate adjustments.

Conclusions:

• Passive, oil-free ATPS droplet generation is feasible with high production rates and tunable sizes.
• The findings provide crucial parameters for optimizing ATPS droplet generation in microfluidic devices.
• This method advances the application of ATPS in bioprocessing and diagnostics.