Utilizing finite element analysis to capture in-plane shear banding lipid monolayer collapse

Mechanisms of biological processes related to self-assembled lipid monolayers in organs such as the ears, eyes, and lungs can be probed through studying the response of Langmuir lipid monolayers to lateral compressive stress. Mechanically, lipid monolayers can be represented as elastic sheets. In this sense, some monolayers relax stress through out-of-plane deformation, while others relax through shear banding, where in-plane rearrangements of condensed domains are observed via fluorescence microscopy (FM). These collapse modes are accessible by tuning system softness, leading to the search for a constitutive material model with similar tunability. The elastic models that are currently used to describe out-of-plane collapse have been unsuccessful in capturing in-plane collapse. Utilizing finite element analysis, we have found that uniaxial compression of a 2D sheet forms shear bands when the elastic material exhibits a non-monotonic stress-strain response. Simulation results from models that incorporate FM-derived domain morphology show that we can trigger shear bands around domains, allowing for their reorganization and reproduction of experimental shear banding morphology. Our findings expand understanding of lipid monolayer mechanical response and microscale elasticity related phenomena.