Oscillating dispersed-phase co-flow microfluidic droplet generation: Multi-droplet size effect

Area of Science:

• Microfluidics
• Fluid Dynamics
• Biotechnology

Background:

• Controllable microdroplet generation is crucial for biological assays and other applications.
• Generating size-optimized droplets from identical samples prevents experimental errors.

Purpose of the Study:

• To develop a novel method for simultaneously generating monodispersed microdroplets of different sizes.
• To enable size optimization of droplets for applications like biological assays.

Main Methods:

• A modified co-flow droplet generation technique was developed.
• The disperse-phase (d-phase) nozzle was oscillated perpendicular to the continuous phase (c-phase) flow.
• This oscillation introduced lateral drag, interacting with axial drag from the c-phase flow.

Main Results:

• Simultaneous and repeatable generation of monodispersed droplets with varying sizes (4 nl–4 μl) was achieved.
• Droplet size was found to be directly proportional to the Weber (We) number and inversely proportional to the Capillary (Ca) number and oscillation frequency.
• The method demonstrated effectiveness even with low interfacial tension fluids, such as in aqueous two-phase systems.

Conclusions:

• The novel oscillatory co-flow method offers precise control over microdroplet size generation.
• This technique is highly promising for applications requiring size-specific droplet generation, including aqueous two-phase systems.
• The ability to generate diverse droplet sizes from a single source enhances experimental reliability.