A new method for making ultrasmall metallic objects through the use of 3D printing has been developed by a group of researchers led by chemist Dmitry Momotenko. The goal of this method is to significantly increase the surface area of battery electrodes in order to significantly shorten charging times.
It takes scientist Liaisan Khasanova under a moment to transform a conventional silica glass tube into a printing spout for an exceptionally unique 3D printer. The chemist closes the flap on the blue device, inserts the one-millimeter-thick capillary tube, and presses a button. There is a loud bang after a few seconds, and the nozzle is ready to use.
“A laser pillar inside the gadget warms up the cylinder and pulls it apart.” Khasanova, who is pursuing her Ph.D. in chemistry in the Electrochemical Nanotechnology Group, explains, “Then we suddenly increase the tensile force so that the glass breaks in the middle and a very sharp tip forms.”
To print extremely small, three-dimensional metallic structures, Khasanova and her colleagues require tiny nozzles. As a result, the openings of the nozzles need to be just as small, sometimes so small that only a single molecule can pass through them. According to Dr. Dmitry Momotenko, who is in charge of the Institute of Chemistry’s junior research group, “We are trying to take 3D printing to its technological limits.” We want to put things together atom by atom.”
‘Metals are the perfect solution’
The chemist explains that nanoscale 3D printing, or 3D printing of objects that are just a few billionths of a meter in size, opens up amazing opportunities. “Metals are the perfect solution.” For metal items specifically, he can conceive various applications in regions like microelectronics, nanorobotics, sensor innovation, and battery innovation. “Metals are the ideal solution because electroconductive materials are required for a variety of applications in these areas.”
While plastic 3D printing has already reached these nanoscale dimensions, it has proven more challenging to produce tiny metal objects using 3D technology. The printed structures are still a thousand times too big for many advanced applications with some methods, and with others, the objects can’t be made with the right level of purity.
Momotenko is an expert in electroplating, a subfield of electrochemistry in which a negatively charged electrode is brought into contact with metal ions suspended in a salt solution. The neutral metal atoms that result from the combination of the positively charged ions and electrons are deposited as a solid layer on the electrode.
“A fluid salt arrangement turns into a strong metal — a cycle that we electrochemists have some control over,” says Momotenko. This equivalent cycle is utilized for chrome-plating vehicle parts and gold-plating gems for a bigger scope.
A little smaller than usual
A little smaller than usual, but transferring it to the nanoscopic scale takes a lot of creativity, care, and effort, as a visit to the group’s small laboratory on the Wechloy campus demonstrates. Momotenko points out that the team built and programmed all three printers in the lab. They have a print nozzle, tubes for feeding in the print material, a control mechanism, and mechanical parts for moving the nozzle, just like other 3D printers do. However, on these printers, everything is a little bit smaller than usual.
The anode—a hair-thin piece of wire—is inserted into the thin capillary tube by a colored saline solution that flows through delicate tubes. The negatively polarized cathode, a smaller-than-fingernail-sized gold-plated silicon flake that serves as the printing surface, completes the circuit. The nozzle is swiftly moved by fractions of a millimeter in each of the three spatial directions thanks to special crystals and micromotors that transform immediately when an electrical voltage is applied.
Unwanted vibrations
Two of the printers are housed in boxes covered in a thick layer of dark-colored acoustic foam because even the tiniest vibrations can disrupt the printing process. Moreover, they are lying on stone plates, each weighing 150 kilograms. The goal of both measures is to stop unwanted vibrations. The lights in the lab are likewise battery-fueled on the grounds that the electromagnetic fields delivered by exchanging flow from an attachment would impede the minuscule electrical flows and voltages expected to control the nanoprinting system.
Liaisan Khasanova, on the other hand, has prepared everything for a test print: The box is closed, the print nozzle is in its starting position, and the tubes are connected to a vial containing a light blue copper solution. She initiates the printing process by starting a program. Curves and dots represent measurement data on a screen. These record the nozzle briefly touching the substrate before repeatedly retracting, as well as the variations in the current flow. What exactly is the printing machine? “Just a few columns,” she says in response.
Exploring the depths of the nanoworld Columns are the simplest geometric forms that can be printed with 3D printers; however, the Oldenburg researchers are also able to print spirals, rings, and a wide variety of structures with overhangs. Copper, silver, and nickel, as well as nickel-manganese and nickel-cobalt alloys, can currently be printed using this method.
They have already ventured deep into the nanoworld in some of their experiments. In a study that was published in the journal Nano Letters in 2021, Momotenko and a group of researchers from around the world said that they had made copper columns with a diameter of just 25 nanometers. This was the first time that 3D metal printing had gone below the limit of 100 nanometers.
A feedback mechanism that makes it possible to precisely control the movements of the print nozzle was one of the main factors in this success. Momotenko and Julian Hengsteler, a Ph.D. student he supervised at his previous workplace, ETH Zurich in Switzerland, worked on it. The chemist elaborates, “The continuous retraction of the print nozzle is extremely important because otherwise it would quickly become clogged.”
The most effective method to control the imperceptible
The group prints the minuscule items layer by layer at velocities of a couple of nanometers per second. It still amazes Momotenko that here, things are being made that are too small to be seen by humans. You begin with a tangible object. The chemist continues, “It is almost unbelievable that you are able to control these invisible things at an extremely small scale after a certain transformation.”
Additionally, Momotenko’s plans for his nanoprinting method are quite perplexing. His objective is to lay the foundations for batteries that can be charged a thousand times more quickly than the models that are currently available. If that is possible, an electric vehicle could be charged in a matter of seconds,” he explains. The essential thought he is chasing after is, as of now, around 20 years old.
During the charging process, the basic idea is to significantly shorten the paths that the ions in the battery take. The current flat electrodes would need to have a three-dimensional surface structure in order to accomplish this. Because the electrodes are so far apart and relatively thick, the current battery design takes so long to charge,” Momotenko explains.
He proposes reducing the distance between the anodes and cathodes to a few nanometers and interlocking them like fingers at the nanoscale as the solution. This would permit the particles to move between the anode and cathode at lightning speed. The issue: battery structures with the required nanodimensions have not yet been produced.
Momotenko has taken on this challenge by fabricating battery materials with structural features that are extremely minute. The objective of his NANO-3D-LION project is to create active battery materials with ultrasmall structural features using cutting-edge nanoscale 3D printing methods.
Momotenko decided to base the project at the University of Oldenburg after collaborating with a research team led by Prof. Dr. Gunther Wittstock at the Institute of Chemistry on a previous project. “I moved here from Zurich at the beginning of 2021 because the Department for Research and Transfer was very helpful with my grant application,” he explains.
His exploration group currently has four individuals: In addition to Khasanova, the team now includes Ph.D. student Karuna Kanes and Master’s student Simon Sprengel. While Sprengel investigates the possibility of printing combinations of two different metals—a procedure required to produce cathode and anode material simultaneously in one step—Kanes focuses on a new method aimed at improving the precision of the print nozzle.
Liaisan Khasanova will soon concentrate on the compounds of lithium. Her main goal will be to figure out how the terminal materials currently utilized in lithium batteries can be organized using 3D printing. The team intends to look into compounds like lithium-iron or lithium-tin, then test how the electrodes should be aligned, how big the nano “fingers” on the surface of the electrodes need to be, and how much space is possible.
Research in the “glove box” One big problem is that lithium compounds are very reactive and can only be handled in a controlled environment. Consequently, the team recently acquired an extra-large laboratory glove box, a sealed, gas-tight chamber that can be filled with argon or another inert gas. The researchers can use one side’s built-in handling gloves to manipulate the contents.
The team plans to install an additional printer within the three-meter-long, half-ton chamber, which is not yet operational. “Momotenko explains that the material’s chemical transformation and all other tests will also need to be done inside the chamber.”
The group will face a few significant inquiries throughout the venture. How do minuscule debasements within the argon climate influence the printed lithium nanostructures? How can the heat that is generated when batteries are charged in a matter of seconds be dissipated? How can large batteries that can power a car or mobile phone be printed quickly as well as tiny battery cells?
“On the one hand, we are working on the chemistry needed to make nanoscale active electrode materials; on the other, we are attempting to adjust the printing innovation to these materials,” says Momotenko, framing the ongoing difficulties.
The issue of energy stockpiling is mind-boggling.
The issue of energy stockpiling is very perplexing, and his group can have a little impact in tackling it, the scientist underlines. Regardless, he sees his gathering in a decent starting position: He says that the only way to make nanostructured electrodes and test the idea right now is through electrochemical 3D printing of metals.
The chemist is also working on other daring ideas besides battery technology. He wants to use his printing method to make metal structures that let him control chemical reactions more precisely than before. The manipulation of “spin,” a quantum mechanical property of electrons, is the primary focus of a relatively new field of study known as spintronics. These plans are part of this field.
Sensors that can detect individual molecules Manufacturing sensors that can detect individual molecules is another idea he wants to put into practice. That would be useful in medicine, for example, in detecting biomarkers for Alzheimer’s disease or tumor markers at extremely low concentrations,” says Momotenko.
“All of these concepts are still very new chemistry approaches.” He admits that “it is not yet clear how it would all work.” However, this is how science works. Each significant examination project requires long reasoning and arranging, and in the end most thoughts fizzle,” he closes. In any case, at times they don’t, and he and his group have previously made the most effective strides on their excursion.
Journal information: Nano Letters
