Molding metals into minuscule shapes is a challenging task, especially when it comes to metals in their solid state. However, the moldability of the metal depends on its flowability under certain conditions. Flowability is high in thermoplastics, gels, and glasses, but most metals are too hard when solid and too fluid in their liquid states to mold with conventional techniques at the nanoscale.
Now, Yale scientists have developed a process that allows manufacturers to essentially shape any metal and alloy and replicate even the smallest details. They dubbed this process as thermomechanical nanomolding, which allows them to mold crystalline metals into shapes as small as a few nanometers in diameter.
Jan Schroers, professor of mechanical engineering & materials science at Yale, said, “It’s really a new way of nanomanufacturing. Today’s nanomanufacturing relies on a few materials that can be fabricated very specifically for a particular material. But our discovery suggests one technique for all metals and alloys: It allows us to fabricate essentially every metal and its combination in the periodic table in a predictable and precise manner to nano-sized features.”
By applying atomic diffusion, in which a change in pressure transports the atoms, scientists found that not only could they efficiently mold crystalline metals, but that decreasing the size of the mold actually made the process easier. As a result, they were able to create very long features at about 10 nanometers in diameter — 8,000 times smaller than a human hair — that would previously have been impossible to make.
Scientists noted, “Because the mechanism of diffusion is present in all metals and alloys, the process could theoretically be used across the board.”
For various applications, scientists experimented the method by molding gold, nickel, vanadium, iron, and numerous alloys. In each case, they found that the method could really fabricate very small nanorods.
The study is published in the journal Physical Review Letters.