MechE Seminar: Topological defects in active and living matter
Event details
| Date | 19.05.2025 |
| Hour | 11:00 › 12:00 |
| Speaker | Prof. Cristina Marchetti, University of California, Santa Barbara |
| Location | |
| Category | Conferences - Seminars |
| Event Language | English |
Abstract:
Motile topological defects are the hallmark of active nematic liquid crystals, where defect creation, motion and annihilation continuously remodel the texture and drive self-sustained active flows. Defects have also been shown to play an important role in the organization of epithelial tissue and in animal morphogenesis. In this talk I will describe topological defects in an active nematic elastomer – a solid-like materials where forces are generated internally by active processes. I will show that in these active solids defects can become motile through local melting of the nematic texture driven by strains induced by active stresses. Unlike in fluids, where defects are advected by active flows, this mechanism does not require flow of material as the defect move relative to the medium via local remodeling of the texture. This work provides a natural framework for understanding the restructuring of the nematic order observed in the fresh water polyp Hydra when the organism regenerates itself from an excised fragment.
Bio:
Cristina Marchetti is a Professor of Physics at the University of California Santa Barbara, where she joined the faculty in 2018, after about thirty years on the faculty at Syracuse University. She is a theoretical physicist who has worked on a broad range of problems in condensed matter and biological physics, including supercooled fluids, transport in disordered media, superconductors, cell mechanics, and, most recently, the physics of active matter. Marchetti is a Fellow of the American Physical Society and of the American Association for the Advancement of Science, a member of the American Academy of Arts and Sciences and the US National Academy of Sciences. In 2019 she was awarded the inaugural 2019 Leo P. Kadanoff Prize by the American Physical Society for "original contributions to equilibrium and non-equilibrium statistical mechanics, including profound work on equilibrium and driven vortex systems, and fundamental research and leadership in the growing field of active matter.”
Motile topological defects are the hallmark of active nematic liquid crystals, where defect creation, motion and annihilation continuously remodel the texture and drive self-sustained active flows. Defects have also been shown to play an important role in the organization of epithelial tissue and in animal morphogenesis. In this talk I will describe topological defects in an active nematic elastomer – a solid-like materials where forces are generated internally by active processes. I will show that in these active solids defects can become motile through local melting of the nematic texture driven by strains induced by active stresses. Unlike in fluids, where defects are advected by active flows, this mechanism does not require flow of material as the defect move relative to the medium via local remodeling of the texture. This work provides a natural framework for understanding the restructuring of the nematic order observed in the fresh water polyp Hydra when the organism regenerates itself from an excised fragment.
Bio:
Cristina Marchetti is a Professor of Physics at the University of California Santa Barbara, where she joined the faculty in 2018, after about thirty years on the faculty at Syracuse University. She is a theoretical physicist who has worked on a broad range of problems in condensed matter and biological physics, including supercooled fluids, transport in disordered media, superconductors, cell mechanics, and, most recently, the physics of active matter. Marchetti is a Fellow of the American Physical Society and of the American Association for the Advancement of Science, a member of the American Academy of Arts and Sciences and the US National Academy of Sciences. In 2019 she was awarded the inaugural 2019 Leo P. Kadanoff Prize by the American Physical Society for "original contributions to equilibrium and non-equilibrium statistical mechanics, including profound work on equilibrium and driven vortex systems, and fundamental research and leadership in the growing field of active matter.”
Practical information
- General public
- Free
Organizer
- Prof. Sangwoo Kim, MESOBIO
Contact
- sangwoo.kim@epfl.ch