Stiffness gradients control phase separation in gels and cells

Living cells compartmentalize various processes using phase separation. The physical mechanisms which control this phase separation are not fully understood. However, the interior of the cell can be simply viewed as a closely packed elastic network, with well-regulated regions of lower or higher stiffness. Using droplet formation in a polymer gel as a model system, we found that phase separation can be controlled by the elasticity of the network, and that droplet size and location evolve over time under a stiffness gradient. Our findings further suggest that elasticity differences in cells may similarly regulate phase separation and could be used by cells to control droplet location.