Microfluidic characterization of extra virgin coconut oil for stable water-in-oil droplet encapsulation

• Emulsification of water in EVCO system has been characterized and optimized to produce stable, monodisperse droplets. • A throughput of ∼190–300 Hz and droplet diameters ranging from 13.29 to 25.22 µm was achieved. • The effect of nonionic surfactants (Tween 20 and Span 80) and comparative study with mineral oil revealed enhanced performance of EVCO. • Capillary and Weber number analysis indicates a clear shift in the jetting regime boundary with surfactant addition. Microfluidic encapsulation enables uniform droplet formation, yet most systems rely on synthetic oils with limited biocompatibility and sustainability. This study evaluates extra virgin coconut oil (EVCO) as a natural continuous phase for water-in-oil (W/O) droplet-based encapsulation, using single droplet generation in a flow-focusing microchannel. Experiments were conducted across varying continuous-to-dispersed flow-rate ratios, with or without nonionic surfactants (Tween 20 or Span 80 at 0.5 % v/v). High-speed imaging and MATLAB-based analysis provided droplet diameter, frequency, and coefficient of variation (CV), which were mapped onto Capillary (Ca) and Weber (We) number coordinates. Without surfactant, EVCO generated droplets at ∼110–140 Hz—lower than mineral oil (∼150–220 Hz)—but maintained more stable dripping. Surfactant addition improved performance: Tween 20 yielded the smallest and most frequent droplets (13–25 μm, CV ∼9–12 %, frequency up to 300 Hz), surpassing mineral oil benchmarks. Span 80 offered moderate enhancement (frequency 120–220 Hz). Stable dripping occurred at Ca = 1.5 × 10⁻³–5 × 10⁻³ and We < 0.1, while transitions to jetting emerged at higher values. Tween 20 shifted droplets deeper into this stable region, confirming its superior interfacial stabilization. Overall, EVCO demonstrates excellent compatibility with microfluidic encapsulation, supporting fine size control and regime stability without synthetic oils. This work affirms the viability of natural oils in flow-focusing systems and highlights their potential for biocompatible, sustainable applications in drug delivery, diagnostics, and food-grade formulations.