Droplet dynamics in textured flow-focusing microchannels: effects of surface texture on deformation and transport

This study investigates the post-formation dynamics of water droplets dispersed in an oil continuous phase within a microfluidic flow-focusing channel incorporating lithographically fabricated surface grooves. The effects of continuous-phase flow rate, interfacial tension, and viscosity ratio on droplet deformation and transport are systematically examined. The role of surface topography is elucidated by quantifying droplet morphology upstream and downstream of the grooved section. At low flow rates, droplets conform closely to the groove geometry, while increasing flow rate promotes a partially suspended state above the oil-filled grooves due to enhanced shear and reduced interfacial residence time. Detailed visualisation of droplet morphologies reveals the coupled influence of hydrodynamics and surface texture. Compared to smooth microchannels, introducing surface texture alters droplet-wall interactions and interfacial behaviour even when the flow rate and fluid properties are unchanged.