Droplet Size Estimator

Estimate droplet size for T-junction and flow-focusing geometries

Input Parameters

Geometry Type

Continuous Phase Flow Rate (Qc) (µL/min)

Dispersed Phase Flow Rate (Qd) (µL/min)

Channel Width (µm)

Interfacial Tension γ (mN/m)

~72 mN/m for water-air, ~25 mN/m for oil-water

Continuous Phase Viscosity (mPa·s)

~1 mPa·s for water, ~20 mPa·s for oil

Results

Droplet Diameter

52.53 µm

Droplet Volume

0.08 pL

Generation Frequency

13175.4 Hz

Capillary Number (Ca)

3.333e-3

Low Ca: Droplet dominated

About Droplet Generation

Droplet size in microfluidics depends on the geometry and flow rates. These scaling laws provide quick estimates for droplet diameter.

T-Junction: d ≈ w × (Qd/Qc)^0.4

Simple geometry, predictable droplet formation at the junction

Flow-Focusing: d ≈ w × (Qd/Qc)^(1/3)

Continuous phase surrounds dispersed phase, tighter size control

Capillary Number (Ca = μQc/γw²): Indicates the balance between viscous and interfacial forces:

• Ca < 0.01: Droplet dominated (large, uniform droplets)
• 0.01 < Ca < 1: Squeezing regime (good control)
• Ca > 1: Dripping regime (smaller droplets, higher shear)

Disclaimer: This calculator uses empirical scaling laws for idealised geometries. Actual droplet size depends on surfactant type, channel wettability, fluid viscoelasticity, and fabrication tolerances. Always validate with experimental measurements.