Active microdroplet merging by hydrodynamic flow control using a pneumatic actuator-assisted pillar structure.

Area of Science:

• Microfluidics
• Chemical Engineering
• Materials Science

Background:

• Microdroplet manipulation is crucial for various applications, including chemical synthesis and biological assays.
• Existing methods for droplet merging often lack precise control or require complex structures.
• Developing a simple, controllable microdroplet merging system is essential for advancing microfluidic technologies.

Purpose of the Study:

• To design and demonstrate a novel microdroplet merging device with active flow control.
• To achieve precise control over droplet merging, including the number of droplets and their volumes.
• To validate the device's performance in a chemical synthesis application.

Main Methods:

• Fabrication of a single-layer polydimethylsiloxane (PDMS) microfluidic device.
• Utilizing two horizontal pneumatic microactuators for hydrodynamic flow control.
• Numerical evaluation of flow dynamics and experimental validation of droplet trapping and merging.
• Performing chemical synthesis of a metal complex using the developed microdroplet merging system.

Main Results:

• Successful active control of microdroplet merging under diverse flow conditions.
• Demonstrated merging of droplets in four distinct modes with variable ratios and volumes.
• Achieved continuous merging performance using hydrodynamic control without surfactants.
• Verified chemical synthesis and real-time visualization of metal complex crystallization.

Conclusions:

• The developed microdroplet merging device offers a simple yet effective solution for controlled droplet fusion.
• The pneumatic actuation system provides precise control over merging events and droplet volumes.
• The device's applicability in chemical synthesis highlights its potential for various microfluidic applications.