Maximilian Kloppe: Phase-Field Modeling of Elastic Surfaces in flow

Abstract

The small thickness of membranes, shells and capsules enables their efficient approximation as hyper-surfaces. Phase-field modeling provides a versatile tool to capture the motion of such elastic hyper-surfaces in fluid flow under bending and surface tension forces. However, the in-plane stretching of the surface has been widely neglected or approximated by inextensibility of the material.

In this talk, we develop a novel phase-field model for elastic hyper-surfaces in Navier–Stokes fluids, which includes bending, tension, and in-plane stretching. The model is based on a coupling of a phase-field model for two-phase flow to a fully Eulerian description of the surface deformation tensor.

In the second part of this talk, we translate these modeling advances into a practical tool for high-throughput, contact-free mechanical characterization of giant unilamellar vesicles (GUVs) by real-time deformability cytometry (RT-DC).

The interpretation of vesicle deformation under flow has been hindered by the absence of a suitable theoretical or computational framework. Using phase-field simulations across a broad parameter space and treating the area expansion modulus K as the dominant mechanical quantity, we derive multiple complementary fitting strategies to extract K from RT-DC data. Furthermore, we show that our methods scale across varying flow rates, channel geometries and buffer viscosities, and produce predictions of K consistent with literature values for different lipid compositions.