Janus Colloids Actively Moving at the Surface of Water

Active motion of living or artificial swimmers (active colloids) may occur in strong confinement and in complex environments. Motion properties of confined active colloids may strongly differ from the ones observed in the liquid bulk. Recently, we showed that the interface between two fluids act as a confinement, which dramatically affects frictions of partially wetted colloidal particles [1]. Here, the impact of partial wetting dynamics on the motion of active Janus colloids will be presented. Immersion depth of the Janus colloids as well as their orientation with respect to the water surface reveal complex and rich wetting properties of Janus particles at the air-water interface [2]. Active directional and circular trajectories have been observed at the interface with a motion persistence significantly enhanced by the partial wetted state of the Janus particles. This confined state impacts the in-plane and out-of-plane particle rotational diffusions, and leads to a truly two dimensional active motion [3].
[1] Nature Materials 14, 908 (2015).
[2] Faraday Discussions 191, 305 (2016).
[3] Soft Matter 11, 7376 (2015).