Materials scientists at the North Carolina State University have connected copper particles with gallium indium alloy bridges to form a conductive printing ink with gel-like properties that are well suited for 3D and 4D printing. Their results appear in the journal Matter.
“3D printing has revolutionized manufacturing, but we’re not aware of previous technologies that allowed you to print 3D metal objects at room temperature in a single step,” said North Carolina State University’s Professor Michael Dickey, co-corresponding author of the paper.
“This opens the door to manufacturing a wide range of electronic components and devices.”
To create the metallic gel, Professor Dickey and his colleagues start with a solution of micron-scale copper particles suspended in water.
They then add a small amount of an indium-gallium alloy that is liquid metal at room temperature. The resulting mixture is then stirred together.
As the mixture is stirred, the liquid metal and copper particles essentially stick to each other, forming a metallic gel network within the aqueous solution.
“This gel-like consistency is important, because it means you have a fairly uniform distribution of copper particles throughout the material,” Professor Dickey said.
“This does two things. First, it means the network of particles connect to form electrical pathways. And second, it means that the copper particles aren’t settling out of solution and clogging the printer.”
The resulting gel can be printed using a conventional 3D printing nozzle and retains its shape when printed.
And, when allowed to dry at room temperature, the resulting 3D object becomes even more solid while retaining its shape.
However, if users decide to apply heat to the printed object while it is drying, some interesting things can happen.
The researchers found that the alignment of the particles influences how the material dries. For example, if you printed a cylindrical object, the sides would…
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