Transformable smart materials move closer to realisation

The team has developed an alloy that can increase its breaking strength upon application of an electrical charge by an unprecedented factor of two.

‘We were pretty happy to see this, I wouldn’t have expected it,’ said one of the collaborators, Dr Jörg Weissmüller from Hamburg University of Technology. ‘In terms of mechanical properties, this has never been done — this is the first time and there is no comparison.’

The material was made using a silver-gold alloy that underwent a corrosion process to remove the silver and form a gold structure containing a network of nanopores 10–20nm in size. This gave the gold a sponge-like structure, massively increasing its surface area. 

By filling the structure with a perchloric-acid electrolyte, an electrochemical double layer was formed between the liquid and metal. The team then applied an electrical charge to alter the absorption and desorption of oxygen on the gold’s surface. Standard mechanical tests revealed that the electric charge reversibly altered the material’s breaking strength and ductility by a factor of two.