Self-propelling liquid metals, developed by researchers at RMIT University in Melbourne, are said to be a critical step towards flexible and reconfigurable soft circuit systems, such as 3D electronic displays and components. Potential applications range from smart engineering to biomedicine.

As well as being malleable, any droplet of liquid metal contains a highly-conductive metallic core and an atomically thin semiconducting oxide skin – essential for making electronic circuits.

To work out how to enable liquid metal to move autonomously, Professor Kourosh Kalantar-zadeh and his group from the School of Engineering at RMIT first immersed liquid metal droplets in water.

"Putting [liquid metal] droplets in another liquid with an ionic content … can allow them to move about freely in three dimensions," Prof Kalantar-zadeh said. "We adjusted the concentrations of acid, base and salt components in water and investigated the effect. Simply tweaking the water's chemistry made the liquid metal droplets move and change shape, without any need for external mechanical, electronic or optical stimulants.

"Using this discovery, we were able to create moving objects, switches and pumps that could operate autonomously – self-propelling liquid metals driven by the composition of the surrounding fluid."

According to the professor, it may be possible to build a 3D liquid metal humanoid on demand: “Like the T-1000 Terminator but with better programming," he concluded.