Microfluidic Valves for Selective on-Chip Droplet Splitting at Multiple Sites.

Area of Science:

• Microfluidics
• Fluid Dynamics
• Chemical Engineering

Background:

• Droplet microfluidics enables precise control over small fluid volumes.
• Controlling droplet division at multiple locations is crucial for complex assays and synthesis.
• Existing microfluidic designs often lack the ability to finely tune droplet division at sequential points.

Purpose of the Study:

• To develop and characterize a microfluidic system for controlled droplet division at two sequential locations.
• To investigate the influence of microchannel geometry, specifically T-junctions and expansion channels, on droplet breakup.
• To establish design principles for integrating microvalves for droplet manipulation.

Main Methods:

• Fabrication of a microfluidic chip with a T-junction followed by an expansion channel.
• Systematic variation of flow rates to observe droplet division regimes.
• Utilizing resistive network analysis to guide microchannel redesign.
• Experimental validation of simulated microvalve placement through channel wall deformation.

Main Results:

• Identified five distinct regimes of droplet breakup based on flow conditions and channel geometry.
• Demonstrated that sequential T-junctions result in division primarily at the first junction.
• Redesigned the microchannel with an expansion channel to achieve balanced flow and enable division at both locations.
• Showcased design requirements for microvalve integration for droplet manipulation.

Conclusions:

• The developed microfluidic system offers precise control over droplet division at two distinct locations.
• Microchannel geometry, including T-junctions and expansion channels, significantly impacts droplet breakup dynamics.
• The findings provide a foundation for designing advanced microfluidic devices for applications requiring sequential droplet manipulation.