On demand nanoliter-scale microfluidic droplet generation, injection, and mixing using a passive microfluidic device

Area of Science:

• Microfluidics
• Biotechnology
• Chemical Engineering

Background:

• Microfluidic devices offer precise fluid control at the microscale.
• Programmable droplet generation is crucial for various applications, including diagnostics and synthesis.
• Existing systems often lack flexibility or are costly to prototype.

Purpose of the Study:

• To present and characterize a programmable nanoliter scale droplet-on-demand device.
• To demonstrate its integration with low-cost, single-layer rapid prototyping microfluidic systems.
• To showcase its utility in droplet sequencing and mixing applications.

Main Methods:

• Utilized a passive microfluidic device controlled by external, electronically controlled pinch valves.
• Employed hydrodynamic barriers and matched resistance channels with varying heights for pressure control.
• Integrated custom reversible microfluidic I/O connections and low dead-volume pinch valves.
• Leveraged open-source microfluidic simulation software and equivalent circuit models for optimization.

Main Results:

• Achieved programmable delivery of nanoliter droplets from up to 9 inputs to a central outlet.
• Demonstrated both nanoliter droplet sequencing and nanoliter-scale droplet mixing.
• Showcased the ability to handle continuous streams or discrete plugs as inputs, enabling hundreds to thousands of solutions.
• Reported successful use in characterizing droplet bunching and synthesizing a DNA library.

Conclusions:

• The developed device offers a versatile and low-cost solution for programmable nanoliter droplet manipulation.
• Its modular design and integration capabilities make it suitable for a wide range of user applications.
• Further enhancements in valve integration could increase operational frequencies for advanced applications.