Controlled Lateral Positioning of Microparticles Inside Droplets Using Acoustophoresis

Area of Science:

• Microfluidics
• Acoustic manipulation
• Biochemical assays

Background:

• Droplet microfluidics integrates multiple unit operations on-chip for miniaturized biochemical assays.
• Controlling microparticle position within droplets is crucial for assay efficiency and success.

Purpose of the Study:

• To demonstrate a novel droplet unit operation for controlling microparticle position during droplet splitting.
• To achieve noncontact, label-free enrichment of microparticles within droplets using acoustic forces.

Main Methods:

• Utilizing bulk acoustic waves to generate an acoustic standing wave field within a microchannel.
• Employing acoustic forces to direct encapsulated microparticles to the center of droplets during a trident-shaped split.

Main Results:

• Achieved 2-fold enrichment of 5 μm polystyrene beads in the center daughter droplet.
• Demonstrated an average recovery rate of 89% for the manipulated microparticles.
• Successfully manipulated red blood cells within droplets, showcasing method versatility.

Conclusions:

• Acoustophoresis is effective for microparticle enrichment in two-phase microfluidic systems.
• This noncontact, label-free method enables new droplet-based assays.
• The technique offers a versatile tool for microparticle manipulation in microfluidic devices.