We explore the mechanisms to actuate and manipulate liquid plugs in monolithic closed channel fluidics with porous hydrophobic walls. Applying a small pressure, as much as 10 mbar, from the rear side of the porous wall, hereafter backpressure, the inherently pinned plug is depinned and flows through downwards the fluidic. The method is reversible in that by removing the backpressure the plug sticks back again to the fluidic. 3D numerical simulations with the volume of fluid method, presented here for the first time, show that the velocity of the plug can be manipulated by adjusting the backpressure. The movement of the plug results from deformation – displacement phases which are observed in the simulation and are corroborated by experimental results, recorded inside fluidics. A simplified model based on measurements of back and front contact angles under backpressure is developed.
Fluidics, Porous materials, Plug actuation, Plug mobility manipulation