Using 'MXene', which has high electrical conductivity and electromagnetic wave blocking capabilities, 3D micro-printing at a thickness of about 1/100th of the thickness of a human hair has been successfully achieved, and expectations are high that it will be utilized in various fields such as high-efficiency batteries and electromagnetic shielding in the future.

Dr. Seung-Kwon Seol's team from the Smart 3D Printing Research Team at the Korea Electrotechnology Research Institute (KERI) has developed the world's first technology to print high-resolution 3D microstructures using 'MXene', known as a dream new material.

First discovered in the United States in 2011, MXene is a two-dimensional nanomaterial made of alternating layers of metal and carbon. MXene has high electrical conductivity and electromagnetic wave blocking ability, and is easy to combine with various metal chemicals, so it is receiving a lot of attention in various fields such as high-efficiency batteries and electromagnetic shielding.

On the other hand, applying Maxene to the 3D printing field required a separate additive (binder), and there was the difficulty of adjusting the ink viscosity (concentration) to the optimal level for printing. In other words, if the supply of Maxene was too much, the problem of high-concentration ink clogging the pipette nozzle occurred, and conversely, if the amount was greatly reduced, there was a limit to sufficiently printing the desired structure. There was also a disadvantage in that the original properties of Maxine were damaged due to additives.

To solve this problem, Dr. Seol Seung-kwon's team utilized their own 'Meniscus' method. Meniscus is a phenomenon in which a curved surface is formed on the outer wall of a water droplet without it bursting due to capillary action when a water droplet is pressed or pulled with a certain pressure. The KERI research team succeeded in manufacturing nano ink for 3D printing that can print high-resolution microstructures even with low viscosity by dispersing highly hydrophilic MXene in water without a binder.

The printing principle is simple. First, when ink is sprayed from the 3D printer nozzle, nano-materials such as MXene are sprayed through the meniscus. At this time, water (solvent) quickly evaporates from the meniscus surface of the ink, and a strong attractive force (van der Waals force) acts inside, causing the nano-materials to bind together. If the nozzle is moved and this process is continuously performed, a 3D micro-structure that conducts electricity is created.

This achievement was achieved by making the most of the characteristics of Maxine without additives, and the results were excellent. The printing resolution was 1.3㎛ (micrometers), which is 270 times higher than existing technology, and is about 1/100th the thickness of a hair.

The performance and usability of electrical and electronic devices have also been greatly improved through the miniaturization of 3D printed structures. When used in the field of energy storage devices such as batteries, the surface area and integration of the structure can be increased to maximize ion transfer efficiency and increase energy density. In electromagnetic shielding, the internal multiple reflection and absorption effects can be amplified to improve performance. In addition, when manufacturing various sensors, we can expect increased sensitivity and improved efficiency.

Dr. Seung-Kwon Seol said, “We put a lot of effort into optimizing the concentration conditions of Maxene ink and precisely analyzing various parameters that may occur during the printing process.” He added, “Our technology is the world’s first to obtain high-strength, high-precision 3D microstructures by taking advantage of Maxene without any separate additives or post-processing.”

The results of this study were highly evaluated and were recently selected as the cover paper of 'Small', a world-renowned academic journal in the field of materials published by Wiley in Germany (JCR top 7%, IF=13). KERI plans to actively seek out companies in demand for commercialization of the developed technology. In addition, as the demand for 'Form-Factor Free' ultra-small and flexible electronic devices that are not restricted by physical form is increasing, the goal is to lead the related market sector through nanoink-based 3D printing technology.

Meanwhile, KERI is a government-funded research institute under the National Research Council of Science and Technology of the Ministry of Science and ICT. This research was conducted as a KERI basic project and the Ministry of Science and ICT's 'Development of materials and process technology for customized 3D printed circuit boards for humanoid skeletons capable of real-time human-robot interaction' project. Dr. Seung-Kwon Seol also serves as a professor at the Korea Research Institute of Science and Technology (KERI) campus of the University of Science and Technology (UST).