Shear-induced gelation of self-yielding active networks

• Published in: arXiv.org 2020-04
• Main Authors: Gagnon, David A, Dessi, Claudia, Berezney, John P, Chen, Daniel T -N, Boros, Remi, Dogic, Zvonimir, Blair, Daniel L
• Format: Article
• Language: English
• Subjects: Biomimetics; Cell division; Continuum modeling; Dynamic mechanical properties; Fluidizing; Gelation; Gels; Mechanical properties; Molecular motors; Networks; Reforming; Rheological properties; Rheology; Shear rate; Stiffness; Stresses; Viscoelasticity; Viscosity
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2004.07331

Molecular-motor generated active stresses drive the cytoskeleton away from equilibrium, endowing it with tunable mechanical properties that are essential for diverse functions such as cell division and motility[1-5]. Designing analogous biomimetic systems is a key prerequisite for creating active matter that can emulate cellular functions[6-7]. These long-term goals requires understanding of how motor-generated stresses tune the mechanics of filamentous networks[8-11]. In microtubule-based active matter, kinesin motors generate extensile motion that leads to persistent breaking and reforming of the network links[12]. We study how such microscopic dynamics modifies the network's mechanical properties, uncovering that the network viscosity first increases with the imposed shear rate before transitioning back to a low-viscosity state. The non-monotonic shear-dependent viscosity can be controlled by tuning the speed of molecular motors. A two-state phenomenological model that incorporates liquid- and solid-like elements quantitatively relates the non-monotonic shear-rate-dependent viscosity to locally-measured flows. These studies show that rheology of extensile networks are different from previously studied active gels[13], where contractility enhances mechanical stiffness. Moreover, the flow induced gelation is not captured by continuum models of hydrodynamically interacting swimmers[14-21]. Observation of activity-dependent viscoelasticity necessitates the development of models for self-yielding of soft active solids whose intrinsic active stresses fluidize or stiffen the network.