Enhanced Diffusive Transport in Fluctuating Porous Media

Journal Article · Thu Apr 01 00:00:00 EDT 2021 · ACS Nano

DOI:https://doi.org/10.1021/acsnano.1c00744· OSTI ID:1773875

Sarfati, Raphaël ^[1]; Calderon, Christopher P. ^[2]; Schwartz, Daniel K. ^[3]

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1. Univ. of Colorado, Boulder, CO (United States); University of Colorado Boulder
2. Univ. of Colorado, Boulder, CO (United States); Ursa Analytics, Inc., Denver, CO (United States)
3. Univ. of Colorado, Boulder, CO (United States)

Mass transport within porous structures is a ubiquitous process in biological, geological, and technological systems. Despite the importance of these phenomena, there is no comprehensive theory that describes the complex and diverse transport behavior within porous environments. While the porous matrix itself is generally considered a static and passive participant, many porous environments are in fact dynamic, with fluctuating walls, pores that open and close, and dynamically changing cross-links. While diffusion has been measured in fluctuating structures, notably in model biological systems, it is rarely possible to isolate the effect of fluctuations because of the absence of control experiments involving an identical static counterpart, and it is generally impossible to observe the dynamics of the structure. In this paper, we present a direct comparison of the diffusion of nanoparticles of various sizes within a trackable, fluctuating porous matrix and a geometrically equivalent static matrix, in conditions spanning a range of regimes from obstructed to highly confined. The experimental system comprised a close-packed layer of colloidal spheres that were either immobilized to a planar surface or allowed to fluctuate locally, within the space defined by their nearest neighbors. Interestingly, the effective long-time diffusion coefficient was approximately 35–65% greater in the fluctuating porous matrix than in the static one (depending on the size of the nanoparticle probes), regardless of the geometric regime. This was explained by considering the enhancing effects of matrix fluctuations on the short-time diffusion coefficient and cooperative “gate-opening” motions of matrix particles and nanoparticle probes.

• Research Organization: Univ. of Colorado, Boulder, CO (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: SC0001854
• OSTI ID: 1773875
• Journal Information: ACS Nano, Journal Name: ACS Nano Journal Issue: 4 Vol. 15; ISSN 1936-0851
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
confined diffusion
diffusive transport
fluctuations
hydrodynamic coupling
obstructed diffusion
porous media