Using computational modeling, we design colonies of biomimetic microcapsules that exploit chemical mechanisms to communicate and alter their local environment. As a result, these synthetic objects can self-organize into various autonomously moving structures and exhibit ant-like tracking behavior. In the simulations, signaling microcapsules release agonist particles, whereas target microcapsules release antagonist particles and the permeabilities of both capsule types depend on the local particle concentration in the surrounding solution. Additionally, the released nanoscopic particles can bind to the underlying substrate and thereby create adhesion gradients that propel the microcapsules to move. Hydrodynamic interactions and the feedback mechanism provided by the dissolved particles are both necessary to achieve the collective dynamics exhibited by these colonies. Our model provides a platform for integrating both the spatial and temporal behavior of assemblies of "artificial cells," and allows us to design a rich variety of structures capable of exhibiting complex, cooperative behavior. Due to the cell-like attributes of polymeric microcapsules and polymersomes, material systems are available for realizing our predictions.ne of the hallmarks of biological cells and microorganisms is their ability to share information and through this communication, perform concerted functions; herein, we use computational modeling to design synthetic microcapsules that mimic this basic biological behavior. To perform this study, we first devise a set of chemical mechanisms that enable a pair of permeable, three-dimensional capsules to create adhesion gradients on a substrate and thereby undergo coordinated, autonomous motion. Implemented in a colony of neighboring capsules, these same chemical mechanisms give rise to self-propelled "snakes" and other self-organized structures. Finally, we consider two distinct colonies of microcapsules and identify scenarios where capsules from the second colony follow the chemical trail left by species from the first. In this manner, the system resembles ant-tracking behavior (1). These studies illustrate how basic concepts from biological signaling can be used to create assemblies of microscopic objects that communicate through external cues and thus exhibit complex, collective behavior. Ultimately, the findings could enable the fabrication of small-scale, interactive devices that cooperate to perform specified functions (e.g., sensing, selforganizing, and self-actuation).Researchers in the physical sciences communities have become fascinated with creating self-propelled, microscopic objects; a recent review article (2) describes examples where chemical reactions (3-7) and external fields (8, 9) provide the "fuel" that drives these synthetic particles. On the other hand, scientists in the biological communities are attempting to develop theoretical and computational models to characterize biochemical signaling processes occurring between cells or microorganisms that lead to their collective...
