Abstract

Driven chemical reactions can control the macroscopic properties of droplets, like their size. Such active droplets are critical in structuring the interior of biological cells. When bridging two structures, such droplets generate capillary forces, which depend on surface properties and distance. Understanding these forces in the presence of active chemical reactions requires determining how chemical reactions alter both droplet nucleation, which controls the onset of force, and the forces themselves. Here, we employ an equilibrium surrogate model, which reveals that reactions increase the effective energy barrier of nucleation, enabling quantitative predictions of the increased nucleation times. Once bridges form, we demonstrate that reactions control the radius of the bridge. This ultimately leads to purely repulsive forces, which contrasts with the typically attractive forces in passive systems. Our results reveal how chemical activity can fundamentally alter forces generated by liquid bridges, which could be exploited by cells.