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Liquid Metals to “Soft-Wire” Elastic Electronics

The shape-shifting metals behind the T-1000 android assassin in the sci-fi movie Terminator 2 may not remain science fiction for long with the development of self-propelling liquid metals that could lead to the replacement of solid state circuits by elastic electronics.

Modern electronics are mainly based on circuits that use solid state components with fixed metallic tracks. However, researchers are trying to create soft circuits that act more like live cells, moving around autonomously and communicating with each other to form new circuits rather than being stuck in a predefined configuration.

Liquid metal droplets have offered the most promising path for achieving this as they are malleable, contain a highly-conductive core and an atom-thin semiconducting oxide skin, all of which are needed to make electronic circuits.

To work out how to enable a liquid metal to move autonomously, Prof Kourosh Kalantar-zadeh’s team at RMIT University first immersed liquid metal droplets in water. “We adjusted the concentrations of acid, base and salt components in the water and investigated the effect,” Kalantar-zadeh said.

“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,” Kalantar-zadeh said. “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.”

The research lays the foundation for the use of “electronic” liquid metals in 3D electronic displays and components on demand, and to create makeshift and floating electronics. “Eventually, using the fundamentals of this discovery, it may be possible to build a 3D liquid metal humanoid on demand – like the T-1000 Terminator but with better programming,” Kalantar-zadeh said.

The research, which has been published in Nature Communications, details the precise conditions in which liquid metals can be moved or stretched, how fluid on their surfaces moves around and – as a result – how they can make different flows.

The work also explains how the electric charges that accumulate on the surface of liquid metal droplets, together with their oxide skin, can be manipulated and used in a range of industries including engineering and biomedicine.