Collective functionalities emerging in active matter

Organisms often cooperate to achieve functionalities that they cannot accomplish alone. However, this puzzle of how biological self-organization emerges from the collective dynamics of individual constituents remains unsolved. In this talk, I will discuss some of these collective functionalities, including non-reciprocal communication, coordinated navigation, and cooperative nutrient transport. First, we focus on ultra-fast communication through "hydrodynamic trigger waves", signals between cells that propagate hundreds of times faster than their swimming speed [1]. Second, we will explore how bacteria can reorient against flows and contaminate reservoirs upstream [2]. Third, we consider how bacteria generate their own flows to transport nutrients [3], and how "active carpets" like biofilms can lead to enhanced non-equilibrium diffusion [4]. Together, these ideas help us understand emergent self-organization in biological systems, but they also teach us about the design space of active and adaptive materials.