Capillary Driven Two-Phase Flow Dynamics in Nonpatterned and Patterned Microchannels

Study of the behavior of fluids inside micro and nanochannels has become particularly important with the extensive advances in micro- and nanofluidic systems. Capillary filling is a phenomenon that occurs in microchannels when the fluid is in contact with the channel walls. This phenomenon can be controlled by introducing certain characteristics in the channel walls and these channels are used in specific applications such as micro-reactors and pressure-sensitive switches. In this paper new insights about some effective parameters in the capillary are provided by which it is possible to increase or decrease the fluid's velocity or even stop its motion at a specific point in the microchannel. The influence of different regimes governed the capillary action on the fluid's velocity is studied. Furthermore, the effect of introducing certain obstacles on the microchannel wall on the capillary action and its relation with the contact angle of fluid is investigated. 2D FEM capillary simulation for three different fluids at contact angles of 30, 50 and 60 degrees showed that at 30 degrees and 50 degrees fluid passes the obstacle and at 60 degrees remains pinned at the obstacle. Finally, certain grooves on the channel walls are used to increase fluid's velocity. Results showed that the grooves increase fluid velocity by 15%.