Control of filament network rigidity by the condensation of crowding molecules

Jiyong Cheon; Zhengyan Lin; Dean Kim; Anirudh Malli; Itamar Kolvin

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arXiv · 2609.26983

Control of filament network rigidity by the condensation of crowding molecules

Jiyong Cheon·Zhengyan Lin·Dean Kim·Anirudh Malli·Itamar Kolvin

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Abstract

Understanding how liquid-liquid phase separation impacts the mechanics of filament networks 6 is a fundamental physical problem at the heart of biological cellular processes and soft material 7 design. While a few theoretical mechanisms have been proposed, a clear demonstration of the direct 8 coupling of phase separation to the overall network stiffness is missing. We report experiments 9 that reveal a universal mechanism by which the condensation of macromolecular crowders induces 10 a rigidity transition in a model filament network. We reconstituted stiff sterically interacting helical 11 filaments and polymeric crowders. Initially, the macromolecules were uniformly dissolved and the 12 filaments formed bundles that assembled a rigid entangled network. Once the crowders condensed 13 into droplets, the network structure lost its rigidity and its mechanical response weakened by an 14 order-of-magnitude. The subsequent dissolution of the condensates was accompanied by the re15 establishment of rigidity. Our results show that crowder phase separation modulates the mechanics 16 of filament networks by tuning the osmotic pressure holding the network together. This principle 17 may serve as a paradigm for devising dynamically tunable filamentous materials.

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Jiyong Cheon, Zhengyan Lin, Dean Kim, Anirudh Malli, Itamar Kolvin. 2026-09-22. Control of filament network rigidity by the condensation of crowding molecules. https://arxiv.org/abs/2609.26983

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