The simultaneous flow of multiple fluid phases through a porous solid occurs in many natural and industrial processes — for example, rainwater infiltrates into soil by displacing air, and carbon dioxide is stored in deep saline aquifers by displacing brine. It has been known for decades that wettability — the affinity of the solid to one of the fluids — can have a strong impact on the flow, but the microscale physics and macroscopic consequences remain poorly understood. Here, we study this problem experimentally by systematically varying the wettability of a microfluidic porous medium. We find that increasing the porous medium’s affinity to the invading fluid results in more efficient displacement of the defending fluid up to a critical wetting transition, beyond which the trend is reversed.
This work is licensed under the Creative Commons Attribution-NonCommercial 4.0 International License. Any reuse must credit the author(s) and provide a link back to this page.