With a little help from nature, engineers at Iowa State University developed tiny metal particles that stay in a liquid state so they can be used for precise soldering that doesn’t require heat.
The engineers wanted to prevent liquid metal from turning into a solid, even below its melting point. First, Martin Thuo and his team used a high-speed rotary tool to sheer liquid metal into droplets within an acidic liquid. Then they simply let the air do some of the work; when the particles were exposed to oxygen, an oxidation layer created a capsule that surrounded the liquid metal. Thuo said, “We engineered the surface of the particles so there is no pathway for liquid metal to turn to a solid. We’ve trapped it in a state it doesn’t want to be in.”
They described their findings in a research paper that published in Scientific Reports. They wrote: “This simple and low cost technique for soldering and fabrication enables formation of complex shapes and joining at the meso- and micro-scale at ambient conditions without heat or electricity.”
In addition to enabling cold soldering, the nanoparticles can also be used for 3D metal printing and to repair metal objects under difficult conditions, such as naval ships at sea, aircraft away from facilities, or potentially explosive gas pipelines. Thuo and the Iowa State Research Foundation Inc. have filed for a patent on the technology, and the researchers have launched a startup called SAFI-tech to commercialize the liquid-metal material.
