Berkeley Fluids Seminar

Wednesday, November 14, 2018

12:00-13:00, Fanuc Room, 6120 Etcheverry Hall

Amaresh Sahu (Chemical Engineering, UC Berkeley)

Irreversible thermodynamics of curved lipid membranes: Theory and computation

Abstract: Biological membranes make up the boundary of the cell as well as several of its internal organelles, including the nucleus, endoplasmic reticulum, and Golgi complex. Although much has been learned about biological membranes experimentally, they are different to model wholistically as they are arbitrarily curved, two-dimensional objects which bend elastically out-of-plane yet behave as a fluid in-plane. We develop the theory of irreversible thermodynamics for arbitrarily curved lipid membranes, and study the coupling between elastic membrane bending and the irreversible processes of in-plane lipid flow, intra-membrane phase transitions, and protein binding reactions. A balance law formulation, combined with an irreversible thermodynamic framework, is used to determine the equations of motion governing lipid membrane dynamics. However, these equations are highly nonlinear and cannot be solved analytically. We develop an arbitrary Lagrangian–Eulerian (ALE) finite element method for arbitrarily curved and deforming lipid membranes. An ALE theory is developed by endowing the surface with a mesh whose in-plane velocity is independent of the in-plane material velocity, and which can be specified arbitrarily. This framework is then used to study two-dimensional curved and deforming fluid films. A new physical insight is obtained, as two-dimensional fluid cylinders are numerically and analytically found to be unstable with respect to long-wavelength perturbations, when their length exceeds their circumference.

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Acknowledgments

Prof. Graham Fleming (Vice Chancellor for Research, UC Berkeley)

Prof. Eliot Quataert on behalf of The Theoretical Astrophysics Center and the Astronomy Department (UC Berkeley)

Prof. Philip S. Marcus on behalf of the Mechanical Engineering Department (UC Berkeley)

Prof. Michael Manga (Earth and Planetary Science, UC Berkeley)

Prof. Evan Variano (Civil and Environmental Engineering, UC Berkeley)