In-droplet microparticle separation using travelling surface acoustic wave.

Area of Science:

• Microfluidics
• Acoustofluidics
• Biotechnology

Background:

• Controlling microscale objects within microfluidic droplets is essential for various applications.
• Existing methods for microparticle manipulation in droplets have limitations.

Purpose of the Study:

• To develop an active method for separating microparticles of different sizes within moving droplets.
• To demonstrate label-free and on-demand separation using acoustic waves.

Main Methods:

• Utilized travelling surface acoustic waves (TSAWs) to generate acoustic radiation forces.
• Applied TSAWs at two different frequencies to manipulate 5 and 10 μm polystyrene microparticles in water-in-oil droplets.
• Demonstrated separation through droplet splitting at a Y-junction.

Main Results:

• Successfully achieved preconcentration and size-based separation of microparticles within moving droplets.
• Microparticles moved laterally, directed by the TSAW propagation, enabling separation based on size.
• In-droplet separation was effectively demonstrated via droplet splitting.

Conclusions:

• The proposed TSAW-based method offers an effective, label-free, and on-demand approach for separating micro-objects in moving droplets.
• This technique has significant potential for applications like in-droplet sample purification and enrichment.
• The study advances microparticle manipulation in droplet microfluidics.