Continuous and tunable droplet splitting using standing-wave acoustofluidics.

Area of Science:

• Microfluidics
• Acoustic manipulation
• Biotechnology

Background:

• Droplet splitting is crucial for microfluidic applications like single-cell analysis and material fabrication.
• Conventional droplet splitting methods face limitations in controlling split ratios and throughput.
• Existing active methods are often complex, slow, or specific to certain droplet types.

Purpose of the Study:

• To demonstrate a simple and effective method for droplet splitting using acoustic fields.
• To investigate the underlying mechanism of acoustic droplet splitting.
• To showcase the potential for high-throughput and controllable droplet manipulation.

Main Methods:

• Excitation of a one-dimensional standing-wave field within a microchannel.
• Theoretical analysis and numerical simulations to understand the splitting mechanism.
• High-speed imaging to observe the droplet splitting dynamics.

Main Results:

• Droplet splitting is achieved via opposing acoustic radiation pressure near a pressure node.
• The splitting process involves distinct necking, full-stretch, and splitting regimes, completed within 1 ms.
• High-throughput droplet splitting demonstrated at flow rates up to 161 μL min⁻¹ with controllable ratios.

Conclusions:

• Acoustic standing-wave fields offer a simple, efficient, and high-throughput method for droplet splitting.
• This technique enables precise control over droplet size and manipulation for microfluidic applications.
• The method extends capabilities in microreactions and drug delivery through selective particle manipulation.