Nanoscale 3D printing: atom printing successful

Atoms are like Lego blocks. You can literally build anything that exists. Lumps of copper only a few atoms wide are the latest achievement.

A small book on the cross section of a human hair

The German-Ukrainian chemist Dmitrij Momotenko and his team have succeeded in printing extremely small copper objects. The smallest objects are only 25 nm wide. That is several tens of atoms. To give an impression of how small that is: if you were to print letters with this technique, you could print the contents of a small book on the cross-section of a human hair.

This is still eight times larger than the dimensions that are within reach with the very best EUV technology from ASML. In principle, this technique is capable of printing one atom at a time.

Electroplating to the nanometer

The principle of electroplating has been known for four centuries. Only this time it’s incredibly accurate. A solution containing copper ions comes into contact with a negatively charged electrode.

Since copper ions are positively charged, in other words, they lack electrons, they turn into neutral copper atoms when they gain a (negatively charged) electron. The result is that you get a small clump of copper at the electrode site. This forms a solid metal layer, accurate to nanometers.

“Inkjet” nanoscale printer

The “ink”, the droplets with copper ions, flows out through a very fine nozzle with a diameter of 1.6 to 253 nm. 1.6 nanometers is so small that only two copper ions can pass through it at a time. As soon as a droplet of this solution lands on the negatively charged surface, this droplet turns into a clump of copper in this way. So it works roughly like an inkjet printer head, but then on an atomic scale.

It wasn’t as easy as it sounds here. Because the fast-growing mounds of copper tend to quickly clog the print head. But thanks to a smart technique, they were able to get ahead of this process. As soon as the printhead threatens to short-circuit, it retracts. In this way they could print vertical columns as well as oblique and spiral shapes, even horizontal shapes.

4000 times smaller than now

Currently, 3D metal printers reach an accuracy of 100 micrometers. This is equivalent to the thickness of a human hair. These work with metal powder. With this new technique, the accuracy is 4000 times greater. Or should we say, small? That existing record is therefore completely shattered with this new technique.

Awesome, you will say to yourself. But when is a tube full of nanorobots going to turn my empty Coke cans into spare keys? Please wait. The applications are now mainly in the chemical industry, says Momotenko, and better batteries, for example.

The more finely branched surfaces are, the more economical and accurate the reactions will be. This way you can produce more with less energy and less pollution. And there is also an application that is very interesting for consumers like us. Because with finely branched electrodes in batteries, our phone charges much faster.

Source:
Dmitry Momotenko et al., Bringing Electrochemical Three-Dimensional Printing to the Nanoscale, Nano Lett.2021, 21, 21, 9093–9101, https://doi.org/10.1021/acs.nanolett.1c02847