Dynamic approaches to minimize the classical curvature-elasticity free energy for a fluid lipid membrane, are extended towards a Surface Beris--Edwards--Helfrich model. This extension explicitly treats the liquid crystal structure of the membrane, which results from the lipid molecules, that are, on average, oriented normal to the surface. Locally varying liquid crystal order leads to local variations in bending rigidities and surface viscosity and thus influences the shape evolution. This provides a multiscale coupling between the local membrane mechanics on the level of the lipids and the mesoscopic length and time scales of biological functions. The model is derived using the Lagrange--d'Alembert principle. We provide a numerical algorithm to solve the equations in the one-constant approximation and demonstrate the impact on the emerging equilibrium shapes, which not only depend on the specified conserved surface area and enclosed volume, as for the classical curvature-elasticity free energy, but also the elastic parameter. Exploring the dynamic evolution shows a tight coupling of tangential flow, shape evolution and liquid crystalline order. We further point to extensions towards lipid phase separation and asymmetric lipid bilayers.
We develop a method to extract the shear viscosity of a lipid membrane from equilibrium molecular dynamics simulations. The method characterizes the rheology of general interfacial systems embedded in three-dimensional media; we term it molecular interfacial rheology. In our simulations the planar bilayer and surroundi...
We investigate the dynamics of spherical lipid vesicles subjected to an osmotic shock using continuum simulations of a permeable, area-incompressible fluid membrane with bending elasticity and surface viscosity. The dynamics are governed by a single dimensionless parameter $\varGamma$, which measures the relative stren...
We rigorously derive a dynamic membrane theory for nonlinear viscoelastic solids with Kelvin-Voigt rheology from the corresponding three-dimensional bulk theory, in the limit of vanishing thickness. The bulk model accounts for inertia, a nonsimple elastic energy depending on the second deformation gradient, and a frame...
The area compressibility modulus is a key descriptor of lipid membrane mechanics, but the molecular interactions that determine this elasticity are not evident from the total modulus alone. Here, molecular dynamics simulations of a POPC bilayer described by the coarse-grained Martini 3 force field were combined with vi...
We present a novel computational framework that couples smoothed particle hydrodynamics~(SPH) with a triangulated membrane mesh to simulate the dynamics of vesicles suspended in fluids. A novel interface-tracking approach enforces membrane impermeability naturally, without resorting to non-physical constraints such as...
Kuiliang Wang, Xinwei Cai, Ting Ye et al.· 0 citations
Water balloons provide a simple model system for studying the dynamics of membrane-confined liquids, yet their quantitative relationship to classical liquid droplets remains unclear. In this work, we experimentally investigate the mechanical properties and impact dynamics of water balloons and compare them with those o...
Shi-Ji Lin, Jing Lei, Bai-Han Wang et al.· The Physics of Fluids· 0 citations
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