Reconfigurable Assembly of Active Liquid Metal Colloidal Cluster

Area of Science:

• Materials Science
• Nanotechnology
• Soft Robotics

Background:

• Colloidal motors offer autonomous movement and self-assembly capabilities.
• Liquid metals, particularly eutectic gallium-indium (EGaIn) alloy, are promising for soft robotics due to their unique properties.

Purpose of the Study:

• To develop reconfigurable, self-assembling colloidal motors using EGaIn nanorods.
• To investigate the autonomous movement and pattern formation of these liquid metal motors under acoustic fields.
• To understand the mechanisms driving cluster formation and collective motion.

Main Methods:

• Synthesis of rod-shaped EGaIn nanorods (210 nm diameter, 850 nm length) using an ultrasound-assisted physical dispersion method.
• Characterization of nanorods revealing a core-shell structure (GaOOH shell, zero-valent liquid core).
• Application of acoustic fields to induce autonomous movement and observe self-organization into patterns.

Main Results:

• EGaIn nanorods function as autonomous colloidal motors, achieving speeds of 41.2 μm/s under acoustic fields.
• Modulating acoustic frequency leads to self-organization into striped, circular, and flower-like clusters.
• Dandelion-like clusters exhibit collective motion and can be dispersed by altering acoustic frequency.

Conclusions:

• Acoustically driven EGaIn colloidal motors can be reconfigured into complex, dynamic patterns.
• The observed flower-like clusters result from a combination of acoustic propulsion, steric repulsion, and hydrodynamics.
• This work demonstrates a novel approach for creating programmable micro-scale robotic systems using liquid metal colloids.