(311e) Predicting and Engineering Multiphase Behavior in Complex and Living Fluids

Complex immiscible fluids are widespread in living and synthetic systems – hydrocarbon mixtures in oil extraction, bacterial colonies, and the cytoplasm of a cell being prominent examples. In the past few years, phase separation has emerged as a key mechanism of cellular organization. The cellular milieu, containing thousands of interacting and reactive species, is compartmentalized into dozens of co-existing phases. However, predicting the emergent phase behavior of multi-component and active fluid mixtures has remained a daunting challenge. In this talk, I will discuss our efforts to address this challenge of relating microscopic interactions to emergent phase behavior in complex living fluids. I will first describe development of simulations that enable tracking of spontaneous phase separation in mixtures with dozens of interacting components. Surprisingly, I will show that mixtures whose components interact randomly have predictable emergent properties - validated by random-matrix theory as well as computer simulations. Our model provides a description of the composition, dynamics, and steady-state properties of complex interacting mixtures with many components. Subsequently, I will describe how this model can be extended to fluids whose constituent interactions are derived from specific considerations that are not purely random - for e.g. particular design strategies or evolutionary constraints. Finally, I will discuss how non-equilibrium processes, such as chemical fluxes, can tunably modify these emergent properties. I will conclude by discussing future directions and potential applications to bio-molecular engineering and programmable self-assembly.