One basic ingredient of life is directed motion found across all scales from molecular motors marching along microtubules, suspensions of bacteria, to flocks of birds. To this end, free energy supplied by some means has to be converted, which drives life out of thermal equilibrium. Even in simple and artificial systems, the combination of directed motion with interactions between many similar "units" leads to fascinating collective behavior and dynamical patterns.
Active Brownian particles
Following a statistical physics perspective, we focus on a minimal model that combines directed motion with volume exclusion.
Dynamical Clustering and Phase Separation in Suspensions of Self-Propelled Colloidal ParticlesI. Buttinoni, J. Bialké, F. Kümmel, H. Löwen, C. Bechinger, and T. Speck, Phys. Rev. Lett. 110, 238301 (2013)[abstract] [arXiv]
Besides physical interactions, some microorganisms can react to their environment through sensing certain signaling molecules emitted by other members of a population. This is a simple form of communication, in which a population follows a predefined action once a quorum has formed. One example is V. fischeri, which controls bioluminescence in accordance with its population density. We are studying how collective behavior and pattern formation can arise in simple models combining directed motion with motility changes triggered by the local concentration of signaling molecules.
Self-organization of active particles by quorum sensing rulesT. Bäuerle, A. Fischer, T. Speck, and C. Bechinger, Nat. Commun. 9, 3232 (2018)[abstract]
Collective Behavior of Quorum-Sensing Run-and-Tumble Particles under ConfinementM. Rein, N. Heinß, F. Schmid, and T. Speck, Phys. Rev. Lett. 116, 058102 (2016)[abstract] [arXiv]