Berlin 2018 – scientific programme
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DY: Fachverband Dynamik und Statistische Physik
DY 59: Microswimmers II (joint session DY/CPP/BP)
DY 59.8: Talk
Thursday, March 15, 2018, 12:00–12:15, BH-N 243
Chemotactic interactions in systems of active and passive colloids — •Julian Stürmer1, Dhruv Singh2, Maximilian Seyrich1, Peer Fischer2, and Holger Stark1 — 1Institut für Theoretische Physik, TU Berlin, Hardenbergstr. 36, 10623 Berlin, Germany — 2MPI-IS, Heisenbergstr. 3, 70569 Stuttgart, Germany
Self-propelled particles exhibit a variety of self-assembled dynamic structures. In particular, mixtures of active and passive colloids crystallize into 2D clusters as a result of chemotactic interactions [1]. The active colloids represent Janus particles that move while creating sinks in a chemical concentration field. The passive colloids react to the corresponding chemical gradients in form of a diffusiophoretic drift velocity towards the active particles. We model the mixtures using Langevin equations and a diffusion equation for the chemical field extending our approach in [2]. With increasing interaction strength, we observe a gaslike state, an oscillatory and finally a collapsed state. We study the clustering dynamics by quantifying the cluster growth and measuring the cluster velocity as a function of cluster size.
In a similar approach, we model a system of solely active colloids that interact via translational and rotational diffusiophoresis. Here, we take into account the asymmetric character of the Janus particles by including dipole contributions in the chemical concentration field. This asymmetry gives rise to interesting collective phenomena, e.g. the formation of chains that has been observed in recent experiments.
[1] D. P. Singh et al., Adv. Mater. 1701328 (2017)
[2] O. Pohl et al., Phys. Rev. Lett. 112, 238303 (2014)