Wettability-driven pore-filling instabilities: Microfluidic and numerical insights

Hypothesis: Interface dynamics, such as Haines jumps, are crucial in multi-phase flow through porous media. However, the role of intrinsic surface wettability in pore-filling events remains unclear, and the pressure response requires further study. This work evaluates the impact of wettability on interface stability and pressure dynamics. Experiments and simulations: We performed microfluidic experiments and level-set simulations of two-phase flow. Water displaced air or Fluorinert in a PDMS micro-model with controlled wettability (contact angles: 60^∘, 95^∘, 120^∘). Three injection velocities covered capillary- to viscous-dominated flow regimes. High-resolution imaging and synchronized pressure recordings linked interface curvature with capillary pressure changes. Findings: At low capillary numbers, wettability strongly affects burst pressure and pinning. Its influence decreases at higher capillary numbers. We observed an apparent wettability shift due to hysteresis and a capillary pressure barrier linked to pore-wall slope variations. Simulations replicated experimental trends, confirming the role of wettability in pore-scale displacement. These findings provide critical insights for improving pore-network models and understanding wettability effects in porous media.