Early stage of externally driven filling of viscous fluids within a microfluidic pore-doublet network

Abstract

The early stage of active capillary filling of viscous fluids in a pore-doublet network is studied experimentally. The effects of operating conditions and fluid properties on the filling process are revealed. In the straight channel, the evolution of the meniscus with time transferred from a linear stage to a power-law stage is due to the interplay among the inertial force, capillary force, and viscous force. An expression of the filling rate is proposed at the present startup of the capillary filling flow. With the addition of surfactant sodium dodecyl sulfate (SDS), the power-law stage of the penetration process turns into another linear stage. In symmetrical Y-shaped microchannels, increasing the capillary number or liquid viscosity or adding surfactant SDS to the solutions effectively reduces the difference in liquid position between the branches. A larger Ohnesorge number leads to more uniform and stable penetration.