Enhanced Diffusive Transport in Fluctuating Porous Media

Area of Science:

• Physics
• Materials Science
• Chemical Engineering

Background:

• Mass transport in porous media is crucial across various scientific disciplines.
• Existing theories lack a comprehensive description for complex transport behaviors in dynamic porous environments.
• Porous matrices are often dynamic, featuring fluctuating walls and changing pore structures, unlike the traditionally assumed static models.

Purpose of the Study:

• To directly compare nanoparticle diffusion in fluctuating versus static porous matrices.
• To quantify the impact of matrix dynamics on transport across different confinement regimes.
• To elucidate the mechanisms behind diffusion enhancement in dynamic porous systems.

Main Methods:

• Utilized a model system of close-packed colloidal spheres as a porous matrix.
• Compared nanoparticle diffusion in a fluctuating matrix with an identical, immobilized static matrix.
• Investigated diffusion across regimes from obstructed to highly confined using various nanoparticle sizes.

Main Results:

• Effective long-time diffusion coefficients were 35-65% higher in fluctuating matrices compared to static ones.
• The enhancement was observed across different geometric regimes and nanoparticle sizes.
• Fluctuations were found to enhance short-time diffusion and facilitate cooperative particle motion.

Conclusions:

• Dynamic matrix fluctuations significantly accelerate nanoparticle mass transport.
• The observed diffusion enhancement is attributed to increased short-time diffusion and cooperative "gate-opening" effects.
• Findings challenge the static matrix assumption and provide insights into transport in dynamic porous media.