Mathematical model of fluid front dynamics driven by porous media pumps

Abstract

Air-permeable porous media hosts air within their pores. Upon removal from the interior of the material, these porous media have the tendency to reabsorb air from the surrounding, acting as a suction pump. Therefore, the technique used to convert porous media into a pump, consists of degassing the material to remove their air inside. The suction property when recovering the air, can be used to move a liquid through a microfluidic channel. Porous media pumps are very accurate devices to move liquids in a completely controlled way. {By studying the dynamics of the liquid front moved by these pumps, it is possible to extract characteristic properties of both the fluid and the porous material.} In this article, we have developed a theoretical mathematical model that precisely characterizes the dynamics of a liquid moved by a degassed porous media pump through a microchannel by comparing it with experimental data. {We have seen the differences between sealing the external surface of the pump so that it cannot absorb air from the outside, both mathematically and experimentally.} We have observed that, in all cases, the theory fits satisfactorily with the experiments, corroborating the validity of the model. The creation of microfluidic pumps using porous media can be a very useful tool in various fields due to its long operating time, small size and the fact that it operates without any external power source.