"Metal glue" could replace welding and soldering – in some applicationsView gallery - 2 images
Usually, if you want to join two metal objects together, you either weld or solder them – depending on how big they are. Both processes involve the application of heat, however. This can damage the items (in the case of electronics), or even cause explosions (in the case of things like gas pipes). That's why scientists at Boston's Northeastern University created MesoGlue. It's a glue that bonds metal to metal – or to other materials – and it sets at room temperature.
Designed by a team led by Prof. Hanchen Huang, MesoGlue is made up of microscopic nanorods that have a metal core. Some of them are coated with the element indium, and some with gallium.
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The facing surfaces of the two objects-to-be-joined are first treated with these rods. A layer of the indium-coated rods is applied to one surface, while a layer of the gallium-coated rods goes on the other. In both cases the rods stand up from the surface, sort of like the bristles of a hairbrush.
"When you mash the heads of the brushes together, all the little bristles push past each other so the two brushes are basically stuck together," PhD student/co-inventor Paul Elliott explains to us. "The interlacing process is fairly similar in our glue. The bristles are spaced well enough so they can slide or be pressed in between each other."
A diagram illustrating how the nanorods interlace and then create a liquid which is subsequently solidified
When the indium and gallium on the rods come into contact, they form a liquid. The metal cores of the rods then react with that liquid, causing it to harden into a cohesive solid. This results in a bond that reportedly matches the strength of a traditional weld or solder.
Additionally, unlike those formed by regular polymer-based glues, MesoGlue bonds are thermally and electrically conductive, they aren't adversely affected by heat, they're highly resistant to air/moisture leaks, and they require little pressure when being formed.
"The metallic glue has multiple applications, many of them in the electronics industry," says Huang. "As a heat conductor, it may replace the thermal grease currently being used, and as an electrical conductor, it may replace today's solders. Particular products include solar cells, pipe fittings, and components for computers and mobile devices."
MesoGlue is now being commercially developed by a spin-off company of the same name. "We are working on turning this into a liquid form that will make the process just like a glue or epoxy that you would use at home," Elliott tells us.
A paper on the research was recently published in the journal Advanced Materials & Processes, plus there's more information in the video below.