Production of Monodisperse Oil-in-Water Droplets and Polymeric Microspheres Below 20 μm Using a PDMS-Based Step...

Area of Science:

• Microfluidics
• Materials Science
• Chemical Engineering

Background:

• Step emulsification (SE) is a robust method for generating monodisperse droplets.
• Producing sub-20 µm monodisperse droplets and microspheres using poly(dimethylsiloxane) (PDMS)-based SE devices remains challenging.
• PDMS microfluidic devices offer potential for low-cost, scalable particle production.

Purpose of the Study:

• To develop and evaluate a PDMS-based microfluidic step emulsification device for producing sub-20 µm monodisperse droplets and polymeric microspheres.
• To compare the performance of straight versus triangular nozzle configurations in PDMS SE devices.
• To demonstrate the fabrication of monodisperse acrylic microspheres via off-chip photopolymerization.

Main Methods:

• Fabrication of two PDMS microfluidic devices, each with 264 nozzles (straight and triangular configurations).
• Hydrophilic surface treatment of devices using oxygen plasma.
• Emulsification of a photocurable acrylate monomer (dispersed phase) in an aqueous polyvinyl alcohol solution (continuous phase).
• Off-chip photopolymerization of generated droplets to form microspheres.

Main Results:

• Straight nozzles produced polydisperse droplets (>30 µm, CV >10%).
• Triangular nozzles yielded monodisperse oil-in-water droplets (<20 µm, CV <4%) with a throughput of 0.5 mL h^-1.
• Monodisperse acrylic microspheres were successfully produced via photopolymerization of the droplets.

Conclusions:

• The PDMS-based microfluidic SE device with triangular nozzles is effective for generating sub-20 µm monodisperse droplets and microspheres.
• This low-cost, disposable, and scalable device has significant potential for laboratory and industrial particle manufacturing.
• The triangular nozzle design is crucial for achieving high monodispersity in sub-20 µm droplet generation.