Microfluidic droplet generation based on non-embedded co-flow-focusing using 3D printed nozzle.

Area of Science:

• Microfluidics
• Fluid Dynamics
• Materials Science

Background:

• Commercial microfluidic droplet generators often use planar flow-focusing, requiring specific coatings or surfactants.
• Planar geometry presents limitations in fluid compatibility and operational versatility.
• Existing axisymmetric capillary generators are difficult to fabricate and not scalable for market entry.

Purpose of the Study:

• To introduce a novel, scalable, and universally compatible microfluidic droplet generator.
• To investigate the fluid dynamics and droplet formation mechanisms in an axisymmetric co-flow-focusing configuration.
• To demonstrate the potential for high-throughput droplet generation without specialized additives.

Main Methods:

• Development of the Raydrop device using aligned capillaries in a pressurized chamber with a 3D-printed nozzle.
• Experimental emulsification of diverse fluids to assess device universality and droplet size range.
• Numerical computation of Navier-Stokes equations to model droplet formation and dripping-to-jetting transitions.

Main Results:

• The Raydrop device successfully generated droplets across a wide range of radii using various fluids without surfactants or coatings.
• Numerical models accurately predicted droplet radius and the dripping-to-jetting transition, validating the underlying physics.
• The non-embedded axisymmetric co-flow-focusing configuration demonstrated enhanced dripping regime performance.

Conclusions:

• The Raydrop technology offers a universal, surfactant-free solution for microfluidic droplet generation.
• Its robust fabrication and numerical optimization capabilities position it for high-throughput applications.
• This device overcomes limitations of planar systems and difficult-to-assemble capillary generators.