Microfluidic Droplet-Generation Device with Flexible Walls

Area of Science:

• Microfluidics
• Fluid Dynamics
• Biomedical Engineering

Background:

• Precise control of droplet size is critical for biomedical research, drug discovery, high-throughput screening, and emulsion manufacturing.
• Current droplet generation devices often have limited ranges of droplet sizes and require multiple setups.

Purpose of the Study:

• To develop a single co-flow microfluidic device with adjustable channel width for flexible droplet size control.
• To investigate the impact of channel width on droplet generation regimes and sizes.

Main Methods:

• A co-flow microfluidic device with adjustable flexible walls was designed and fabricated.
• The continuous (C)-phase channel width was varied to modulate flow velocity and viscous forces.
• Droplet generation regimes (dripping and plug) were observed, and droplet sizes were measured across different channel widths and flow conditions.

Main Results:

• Adjusting the channel width allowed for on-demand modulation of droplet sizes within a single device.
• Two regimes, dripping and plug, were identified based on channel width and low dispersed (D)-phase Weber numbers.
• Reducing channel width, particularly at a constant C-phase flow rate, resulted in smaller droplets due to wall effects and increased C-phase velocity.
• A droplet size range of 175–913 µm was achieved, significantly wider than existing single-device capabilities.

Conclusions:

• The developed microfluidic device offers a versatile platform for generating a broad spectrum of droplet sizes.
• An empirical model based on Buckingham's Pi theorem was established to predict droplet size, incorporating channel dimensions and flow parameters.