8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

Tue 611:23-14:00P10.33Hydrodynamic interactions in populations of modelsquirmersShashi Thutupalli, 1 Ralf Seemann, 2 and Stephan Herminghaus 11 MPI-DSO, Bunsenstraße 10, 37073, Göttingen, Germany2 Saarland University, Saarbrücken, GermanyMany questions remain open regarding the hydrodynamic effects on microswimmers, in particularthe coupling between swimmers. Here we present experiments on artificial swimmers, where hydrodynamicsis seen to be responsible for a wide range of collective behavior. We create monodispersedroplets containing chemicals that produce a steady source of Bromine ions in an externalsurfactant rich oil phase. The surfactant (mono-olein) reacts at the droplet interface with theBromine from the droplets, and a dynamic instability leads to gradients of interfacial tension.These gradients set up Marangoni flows propelling the droplets, in a manner similar to the classicalsquirmer model of swimming. The flow around the swimmers is measured using particle imagevelocimetry (PIV) and reveals the far field flows generated by the swimmers in the surroundingliquid, leading to the emergence of bound states and oriented clusters.33