Big advance for little machines

Scientists in China have built a collection of miniature vehicles that run on liquid metal wheels, powered and steered by electric fields.

Miniaturised vehicles can move small objects or deliver cargo in microfluidics, lab-on-a-chip applications or micromanufacturing. Most miniaturised motors are powered chemical reactions or external magnetic fields, which can be difficult to control accurately.

Jing Liu and You you Yao at Tsinghua University in Beijing, have 3D printed 1–2cm long vehicles that run on wheels made of a liquid gallium–indium alloy and are powered by an electric field. When immersed in an electrolyte, the electric field induces a gradient in the metal wheel’s surface tension, which causes it to rotate. Changing the voltage and direction of the currents allowed the team precise control over both the speed and direction of travel.

Liu and his team are now working on improving their designs by integrating miniaturised power and control systems into vehicle itself.