Seminare der Theoretischen Physik

Living systems tune their mechanics across scales by coupling biochemistry to physical mechanisms that reconfigure and strengthen in response to their surroundings. We build controlled model systems from DNA nanostars, whose liquid-liquid phase separation (LLPS) harnesses nucleic acids' design power. First, dense packings of multiphase DNA droplets form a simple prototissue: same-species droplets coalesce, while different species repel like hard spheres. These packings undergo a solid-to-liquid unjamming transition, and simulations show its sharpness depends strongly on biomolecular diversity and stoichiometry. Second, DNA droplets occupying less than 10% of an entangled actin network stiffen it 25-fold, reversibly, far beyond the roughly 25% classical theory predicts. Actin penetrates the droplets, so network elasticity in turn sets droplet size, giving reciprocal control between matrix and inclusions. We attribute the stiffening to actin entrainment, which enlarges the effective inclusions until their contact network dominates the mechanics. Together, these results show that LLPS can control not only local composition but also mechanics, pointing toward design principles for adaptive materials.


	Oktober 2026

Do	29.10.2026 Institute for Theoretical Physics/SR 3 A03.101 Theoretische Physik
14:15	Seminar Statistical Physics Samuel Wilken Univ. of Mainz Self-assembled mesoscale mechanics: jamming and stiffening with DNA liquids Abstract Living systems tune their mechanics across scales by coupling biochemistry to physical mechanisms that reconfigure and strengthen in response to their surroundings. We build controlled model systems from DNA nanostars, whose liquid-liquid phase separation (LLPS) harnesses nucleic acids' design power. First, dense packings of multiphase DNA droplets form a simple prototissue: same-species droplets coalesce, while different species repel like hard spheres. These packings undergo a solid-to-liquid unjamming transition, and simulations show its sharpness depends strongly on biomolecular diversity and stoichiometry. Second, DNA droplets occupying less than 10% of an entangled actin network stiffen it 25-fold, reversibly, far beyond the roughly 25% classical theory predicts. Actin penetrates the droplets, so network elasticity in turn sets droplet size, giving reciprocal control between matrix and inclusions. We attribute the stiffening to actin entrainment, which enlarges the effective inclusions until their contact network dominates the mechanics. Together, these results show that LLPS can control not only local composition but also mechanics, pointing toward design principles for adaptive materials. Kontakt: Peter Sollich