Unconventionally Fast Transport through Sliding Dynamics of Rodlike Particles in Macromolecular Networks

TL;DR

This study reveals that thick rodlike particles exhibit unconventional, fast sliding diffusion in macromolecular networks due to length commensuration, challenging traditional thin-rod diffusion models and offering insights for designing efficient transport systems.

Contribution

The paper uncovers a novel sliding diffusion mechanism for thick rods in networks, supported by experiments, simulations, and theory, expanding understanding beyond thin-rod models.

Findings

Fast diffusion occurs at rod lengths multiple of mesh size.

Sliding dynamics is an intermediate between hopping and Brownian motion.

Theoretical analysis matches simulation results, explaining the mechanism.

Abstract

Transport of rodlike particles in confinement environments of macromolecular networks plays crucial roles in many important biological processes and technological applications. The relevant understanding has been limited to thin rods with diameter much smaller than network mesh size, although the opposite case, of which the dynamical behaviors and underlying physical mechanisms remain unclear, is ubiquitous. Here, we solve this issue by combining experiments, simulations and theory. We find a nonmonotonic dependence of translational diffusion on rod length, characterized by length commensuration-governed unconventionally fast dynamics which is in striking contrast to the monotonic dependence for thin rods. Our results clarify that such a fast diffusion of thick rods with length of integral multiple of mesh size follows sliding dynamics and demonstrate it to be "anomalous yet Brownian". Moreover, good agreement between theoretical analysis and simulations corroborates that the sliding dynamics is an intermediate regime between hopping and Brownian dynamics, and provides a mechanistic interpretation based on the rod-length dependent entropic free energy barrier. The findings yield a principle, that is, length commensuration, for optimal design of rodlike particles with highly efficient transport in confined environments of macromolecular networks, and might enrich the physics of the diffusion dynamics in heterogeneous media.