Speaker
Description
In the living world, organisms often adapt their behavior based on how crowded their environment is—a phenomenon known as quorum sensing. For example, people slow down in crowded spaces, and bacteria change activity depending on population density. However, most synthetic active materials, made of self-propelled particles, lack this ability. They move, but they do not respond to their surroundings, which limits the complexity of patterns they can form. In our study, we introduce a new kind of synthetic material that incorporates quorum sensing to overcome this limitation.
We design microscopic colloidal rods that are powered by an electric field and programmed to sense local density. When the rods are in low-density regions, they actively roll; when they encounter crowded areas, they shut off their inner engine and stop moving. This simple feedback mechanism leads to surprising behaviors. We observe two main effects: one where active and inactive regions coexist, and another where the entire system freezes, entering an absorbing state. By combining experiments, simulations and theoretical modeling, we show how this adaptive behavior emerges from interactions between particles and their environment.
Our findings provide a new design strategy for synthetic materials that can react to their surroundings, a step toward creating active matter that does not just move, but adapts.
