Orientational frustration drives enhanced diffusion of anisotropic particles in a liquid labyrinth

Rohit Mangalwedhekar; Limeng Ruan; Somen Nandi; Quentin Gresil; Marc Tondusson; Stephane Bancelin; Lea-Laetitia Pontani; Laurent Cognet

arXiv · 2605.23340

Orientational frustration drives enhanced diffusion of anisotropic particles in a liquid labyrinth

Rohit Mangalwedhekar·Limeng Ruan·Somen Nandi·Quentin Gresil·Marc Tondusson·Stephane Bancelin·Lea-Laetitia Pontani·Laurent Cognet

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Abstract

Transport of nanoscale objects in complex, structured environments plays a key role in a wide range of processes, from biomolecular dynamics in extracellular spaces to transport in porous materials such as filters and catalysts. While anomalous diffusion is well established, how particle anisotropy governs transport under geometric constraints remains unclear. Here we use 3D single-particle tracking to investigate the diffusion of stiff one-dimensional carbon nanotubes in a continuous soft matter network of interconnected chambers and constrictions. Transport is anomalous and antipersistent, with strong length dependent confinement and trapping, consistent with obstructed diffusion. Unexpectedly, however, escape from confinement is poorly sensitive to nanotube length as opposed to what would be expected of pore mediated transport. Despite a tenfold length increase and significantly enhanced trapping, escape time increased by only ~1.4. Single-particle orientational tracking reveals the origin of this weak scaling. Indeed, long nanotube, i.e. those with length comparable to the chamber dimensions, dynamically align with constrictions enabling efficient, geometry-assisted escape that offsets increased confinement while shorter nanotubes need to screen the volume to find their escape path. These results uncover an alignment-mediated transport mechanism that decouples confinement strength from escape kinetics, distinct from pore-mediated transport mechanisms, establishing a quantitative framework for anisotropic diffusion in complex environments.

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Rohit Mangalwedhekar, Limeng Ruan, Somen Nandi, Quentin Gresil, Marc Tondusson, Stephane Bancelin, Lea-Laetitia Pontani, Laurent Cognet. 2026-05-22. Orientational frustration drives enhanced diffusion of anisotropic particles in a liquid labyrinth. https://arxiv.org/abs/2605.23340

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