Reconfigurable Assembly of Active Liquid Metal Colloidal Cluster.

We report the reconfigurable assembly of rod-shaped eutectic gallium-indium alloy (EGaIn) liquid metal colloidal motors by mimicking the growth behavior of a dandelion. EGaIn nanorods with a diameter of 210 nm and a length of 850 nm were synthesized via an ultrasound-assisted physical dispersion method. The nanorods possess a core-shell structure with a 30 nm GaOOH shell and zero-valent liquid core. The EGaIn motors move autonomously at a speed of 41.2 μm s under an acoustic field. By modulating the frequency of the applied acoustic field, the EGaIn colloidal motors self-organize into various striped and circular patterns, followed by a flower-like cluster. The dandelion-like EGaIn colloidal motor clusters move collectively and redisperse when the applied acoustic frequency is changed. Numerical simulations reveal that the flower-like clusters are created by the acoustic propulsion in combination with steric repulsion and hydrodynamics.