Microfluidic droplet pinch-off modified by hard and soft colloids: A scaling transition

Abstract

This Letter explores the influence of colloids at liquid-liquid interfaces on droplet pinch-off dynamics in microfluidic devices, examining hard polystyrene particles and soft pNIPAM microgels. We uncover a significant deviation in droplet formation time compared to pure systems, similarly to surfactant-laden systems, yet notably, colloids exert minimal impact on droplet size, indicating potential nonlinear effects. The dynamics of neck thinning without colloids agree with the classic pendant drop scaling laws, while particle presence replaces traditional viscous and inertial-viscous regimes with a single power law, suggesting an elastic behavior driven by soft particle interactions. Published by the American Physical Society 2024