סמינר מחלקה של איתמר קולוין - ממברנות פולימריות פעילות: הרכבה עצמית ללא שיווי משקל ודינמיקה מאורגנת עצמית
School of Mechanical Engineering Seminar
Monday, December 5, 2022 at 14:00
Wolfson Building of Mechanical Engineering, Room 206
Active polymerized membranes: nonequilibrium self-assembly and self-organized dynamics
Dr. Itamar Kolvin
Physics Department, UC Santa Barbara
Engineering flows and deformation is typically a top-down approach: think of a fluid pumped through a pipe, or a concrete pillar supporting a structure. Biology, however, often takes a bottom-up approach to mechanics. Microscopic actin filaments self-assemble into contracting sarcomere units and then into the myofibrils and muscle fibers that make up our skeletal muscles. In this talk, I will introduce the field of active matter: fluids and solids that are driven by mechanically active microscopic units. I will show how extensile active flows drive the assembly of polymerized membranes in an aqueous environment. Initially, homogeneously and isotropically distributed actin bundles condense into a thin two-dimensional layer where they connect to form an elastic network of tens-of-microns pore size. Membranes then exhibit out-of-plane bending fluctuations that exceed thermal motions by orders of magnitude. Active bending endows the fluctuating membranes with in-plane deformation soft modes that coarsen into large, millimeter-scale, strain fluctuations. For membranes that are a few millimeters in width, system-size displacement oscillations appear that are coupled to unidirectional flow waves. Active matter is thus an emerging paradigm for the mechanical control of assembly and dynamics in materials. I will discuss future extensions of this principle.
Dr. Itamar Kolvin received his Ph.D. from the Hebrew University of Jerusalem for studying dynamic fracture fronts in brittle hydrogels. In 2017, he became a Human Frontier Science Program fellow at UC Santa Barbara, where he pursues postdoctoral research in active and adaptive soft materials. Dr. Kolvin is broadly interested in the non-equilibrium mechanics of fluids and solids at the nexus of hydrodynamics, elasticity, and soft matter.
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