Contact angle hysteresis: A new paradigm?

The wetting of a surface by liquid is crucial part many natural and industrial processes. Despite numerous existing studies, some elements wetting-drying such as contact angle variation during flow, are still poorly understood, yet it piece information needed for modeling fluid displacements in capillary-dominated flows. In the context multi-phase flow porous media, scarcity direct measurements inside pores (in-situ) has added to ambiguity. This work presents an unprecedented study variations at different stages variety systems, using pore-scale measurements. Observations reveal that on average, patterns depend strongly type nonwetting fluid: dodecane decane, instance, show large hysteresis between drainage (drying) imbibition (wetting) cycles, while air or Soltrol® 220 oil exhibits little hysteresis. To further explore this behavior, we evaluate from perspective geometry, combined effects fluid-fluid curvature wetted-pore-radius can explain observed trends. We hypothesize that, certain fluids, fluid-solid chemical interactions lead pinning interfaces fairly enhanced fluids. Overall, suggests result interplay pore geometry forces deforming interface (including interactions), thus, - despite traditional practice -, alone not always accurate metric wettability.