Probing elastic anisotropy on entropic interfaces

Abstract

Liquid-liquid phase separation is vital in the formation of many biomolecular condensates, including cellular membraneless organelles. When semiflexible macromolecules are involved, the process switches from mostly enthalpy- to dominantly entropy-driven, changing the intrinsic nature of the interfaces and bringing new physical traits. Here, we present a concept to address the complexity of entropic interfaces where laser trapping and microscopy are combined to capture the behavior of probe colloidal particles onto liquid crystalline droplet surfaces. Hertz-Frank-Oseen contact theory is extended to calculate the elasticity of the droplet based on particle trajectories. We show that this method is sensitive enough to resolve the anisotropic elasticity originating from the collective molecular orientation of constitutive semiflexible mesogens, introducing a possible tool to assess biomechanics of cellular and molecular condensates.