Generating forces in confinement via polymerization

The growth and reconfiguration of polymer networks such as the cytoskeleton can generate forces that move objects and deform materials and membranes, even in the absence of molecular motors. Taking inspiration from this, we ask whether a dynamic polymer system can generate deformation forces by merely controlling the monomer structure and interactions, and the temporal schedule of monomer release, which can be considered a "molecular program" directing polymer assembly. Using simulations of patchy particles that are released into the interior of a vesicle at a given rate, we ask which molecular programs are most proficient at generating forces. We show that stiff polymers induce deformation by spontaneously bundling, and deforming the vesicle axially. The rate at which monomers are released controls whether the polymers can generate forces quickly, or deform the vesicle more slowly but with a larger maximal force. For softer polymers, which cannot ordinarily deform the vesicle, we demonstrate that introducing crosslinkers can be enough to promote the bundling of polymers required to deform vesicles, but that the details of how this crosslinking is implemented can significantly affect the outcome. Finally, we show that dynamic release of monomers and crosslinkers can increase the variance of this process, and that by making the polymers polar filaments one can obtain better force generation by suppressing nucleation. Our results provide a blueprint for the experimental realization of molecular programs that could produce nanoscale forces using synthetic biopolymers.