Biophysical Society Thematic Meeting | Riga 2026

Active and Responsive Soft Matter: From Biological to Engineered Systems

Tuesday Speaker Abstracts

A CONTRACTING CYTOSKELETAL NETWORK ORGANIZES INTO A SELF CENTERING SWIMMER Christoph F. Schmidt 1 ; Jianguo Zhao 1,2 ; Charlie Duclut 2,3,4 ; Abhinav Singh 5,6,7 ; Rahil Golipour 8 ; An Pham 1 ; Behzad Golshaei 1 ; Chonglin Guan 1 ; Mingru Li 1 ; Dieter R Klopfenstein 9 ; Rudolf Oldenbourg 10 ; Ivo F Sbalzarini 5,6,11 ; Stephan W Grill 5,7,11 ; James L Harden 8 ; Frank Jülicher 2,7,11 ; 1 Duke University, Department of Physics and Soft Matter Center, Durham, NC, USA 2 Max Planck Institute for the Physics of Complex Systems, Dresden, Germany 3 Institut Curie, Laboratoire Physico-Chimie, Paris, France 4 Université Paris Cité, Laboratoire Matière et Systèmes Complexe, Paris, France 5 Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany 6 TU Dresden, Faculty of Computer Science, Dresden, Germany 7 Center for Systems Biology Dresden, Dresden, Germany Active, collective cytoskeletal flow patterns drive many processes in eukaryotic cells. The physical mechanisms underlying the emergence of mesoscale flow of the cytoskeleton are still not well known. We here reconstituted an active cytoskeleton in water-in-oil emulsion droplets filled with Xenopus Laevis egg extract to study a model system that includes the full molecular complexity of the cytoskeleton and its non-equilibrium dynamics. The actin network remained isotropic, while a 3D radially convergent steady-state flow emerged, driven by actomyosin contraction and maintained by continuous actin turnover. We present a hydrodynamic computational model that treats the actin network as an isotropic active viscoelastic gel and suggests that connectivity percolation of actin filaments is essential for the observed flow velocity and density profiles. We introduce the concept of the cytoskeletal network as an exotic active swimmer that can sense boundaries without being physically attached, which leads to the observed robust centering of phase-separated inclusions. 8 University of Ottawa, Department of Physics, Ottawa, ON, Canada 9 University of Göttingen, Third Institute of Physics, Göttingen, Germany 10 Marine Biological Laboratories, Woods Hole, MA, USA 11 TU Dresden, Cluster of Excellence Physics of Life, Dresden, Germany 12 TU Dresden, Biotechnology Center, Dresden, Germany

14