A range of applications could come from changing the surface structure of liquid metal – and potentially solid metal – with the right amount of heat.
Researchers from Iowa State University have achieved a breakthrough that could lead to the development of smart alloys that evolve with their environment. If perfected, it could have a range of applications from sensing to catalysis.
Writing in Angewandte Chemie, the researchers compared it to a chameleon changing its skin colour in response to its environment. They showed that treating particles in liquid metal alloys with heat causes them to roughen their surfaces with tiny spheres or nanowires.
By controlling that heat, it’s possible to control the surface patterns. The researchers started off with a liquid metal alloy of gallium, indium and tin synthesised into particles and covered with a smooth oxide shell that has been chemically stabilised. When the particles are heated, it thickens the surface and stiffens until it starts behaving like a solid.
Eventually, the surface breaks, allowing the liquid metal inside to come to the surface. Gallium, as the most reactive, breaks through first, followed by indium and then tin once temperatures of almost 900 degrees Celsius are reached.
“The particles are responding to a certain level of heat and releasing a specific element based on temperature, just as a chameleon responds to the colour of its environment,” said Martin Thuo, lead author of the paper. “That’s why we say they’re chameleon metals – but responding to heat, not to colour as the reptile does.”
Because the metal particles respond to a very controlled environment, the researchers can predict and program the exact surface texture of the particles. This, they added, could allow for its use to fine-tune a metal’s performance as a catalyst or its ability to absorb compounds.
“When you talk about smart materials, polymers come to mind,” Thuo said. “But metals can do this, too. But it’s a big beast – you just need to know how to tame it.”