Metallic material can switch back and forth between hard and soft states
By Ben Coxworth
June 7, 2011
We may not yet have the liquid metal depicted in the Terminator movies, but scientists have now developed something that's vaguely along the same lines. German materials scientist Dr. Jörg Weißmüller and Chinese research scientist Hai-Jun Jin have created a metallic material that can change back and forth between being strong but brittle and soft but malleable, via electrical signals.
The metals used in the material are typically precious ones, such as gold or platinum. They are placed in an acidic solution, which causes minute pores to form within them - in other words, they start corroding. Those pores are then impregnated with a conductive liquid, such as saline solution or diluted acid.
By varying an electrical current that is applied to the liquid, electrons are added to or withdrawn from the surface atoms of the metal. This can increase the strength of the material as a whole by up to 200 percent, or it can cause it to become softer, but also better able to absorb energy without shattering.
Not only could the strength of an entire component made with the material be controlled with the flip of a switch, but it is also conceivable that the material could create its own electrical signals within specific regions, in response to mechanical stress. In this way, it could mostly remain strong and hard, yet selectively allow parts of itself to become malleable in order to avoid cracking. Existing cracks could perhaps also be healed.
"For the first time we have succeeded in producing a material which, while in service, can switch back and forth between a state of strong and brittle behavior and one of soft and malleable," said Weißmüller, head of the Institute of Materials Physics and Technology at the Technical University of Hamburg and also of the department for Hybrid Material Systems at the Helmholtz Center Geesthacht. "We are still at the fundamental research stage but our discovery may bring significant progress in the development of so-called smart materials."