Convective Self-Sustained Motion in Mixtures of Chemically Active and Passive Particles

We develop a model to describe the behavior of a system of active and passive particles in solution that can undergo spontaneous self-organization and self-sustained motion. The active particles are uniformly coated with a catalyst that decomposes the reagent in the surrounding fluid. The resulting variations in the fluid density give rise to a convective flow around the active particles. The generated fluid flow, in turn, drives the self-organization of both the active and passive particles into clusters that undergo self-sustained propulsion along the bottom wall of a microchamber. This propulsion continues until the reagents in the solution are consumed. Depending on the number of active and passive particles and the structure of the self-organized cluster, these assemblies can translate, spin, or remain stationary. We also illustrate a scenario in which the geometry of the container is harnessed to direct the motion of a self-organized, self-propelled cluster. The findings provide guidelines for creating autonomously moving active particles, or chemical “motors” that can transport passive cargo in microfluidic devices

Designing Mechanomutable Composites: Reconfiguring the Structure of Nanoparticle Networks through Mechanical Deformation

Via a new dynamic, three-dimensional computer model, we simulate the tensile deformation of polymer-grafted nanoparticles that are cross-linked by labile bonds, which can readily rupture and reform. For a range of relatively high strains, the network does not fail, but rather restructures into a stable, ordered structure. Within this network, the reshuffling of the labile bonds enables the formation of this new morphology. The results provide guidelines for designing mechano-responsive hybrid materials that undergo controllable structural transitions through the application of applied forces