Many porous media contain fluids confined at the nanoscale, including a variety of natural (rocks, plant vessels) and industrial (concrete, filters) materials. In this presentation, I will discuss the dynamics of a few specific phenomena that occur in materials containing nanopores, including capillary condensation and cavitation, which I have investigated at Cornell University using model systems obtained with micro and nano-fabrication techniques.
First, I will show that the massive capillary stresses associated with the large curvatures of liquid-vapor interfaces in nanopores can be used to generate significant controlled flows through the porous matrix, a strategy similar to that used by trees to move the water from their roots to their leaves. Analysis of these flows allowed us to probe the dynamic response of nano-confined liquids.
Second, confinement may induce large deviations to the liquid-vapor phase transition, and I will discuss the dynamics of capillary condensation, where vapor spontaneously condenses as a liquid in the nanopores even when far from saturation (~50% relative humidity).
Last, drying of a material containing nanopores can bring the liquid to strongly metastable states (negative pressure, or tension) that relax suddenly through the nucleation of vapor bubbles (cavitation). I will show that the coupling between nucleation kinetics and transient pressure relaxations results in self-organized periodic bursts of cavitation that are tunable with the geometry of the porous matrix.