Active liquid interfaces

How do active flows drive pattern formation at soft interfaces?

Interfacial instabilities

The shape of living matter is often determined by the active flows pushing and pulling on the boundary. At a soft boundary, active stresses couple to surface stresses, producing unique morphologies such as the interfacial instability shown on the left. Large droplets grow different radial modes due to the bulk, interior active stress; small droplets are stable due to their larger Laplace pressure.

After the initial linear instability, nonlinearities onset and active interfaces become highly dynamic. We observe asymmetric height fluctuations and even the formation of cusp-like structures. I combine tools from hydrodynamics and differential geometry to theoretically model how active interfaces get their shape. In parallel, I perform experiments to explore the novel shapes dynamics of active interfaces and quantify their behavior.

To build active interfaces in the laboratory, I embed a microtubule-based active fluid into a phase separating polymeric fluid containing PEG and Dextran. The active fluid partitions itself into the Dextran rich phase, creating an active, Dextran-rich fluid and passive, PEG-rich fluid separated by a fluid interface.

Broken symmetries

Geometry & Topology in Reaction-Diffusion

Living materials use chemical signals to coordinate behavior over large length scales. But often these signals travels along a curved surface and are constrained by the material's topology. I’m interested in how geometric and topological constraints affect reaction–diffusion processes in living materials. Our recent experimental work found that chemical waves travel anisotropically in a tissue with nematic order. The simulations on the right show chemical waves bending around nematic defects.

How do geometric and topological order sculpt chemical waves?