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Manufacturing Technology for Ultra-stretchable Materials by Using the Periodic 3D Porous Nanostructure

Development of world-leading stretchable electronic materials

"As the wearable computer market has become more active, it is expected that alternative technologies that increase stretchability while maintaining desirable material characteristics will gain more attention. The manufacturing technology for ultra- stretchable materials by using the periodic 3D porous nanostructure is quite significant as it can be used to increase the stretchability of any elastomeric materials up to a desired level through the 3D nanostructuring process. It is expected that the technology can be applied to the multifunctional stretchable platform in various fields including optical science and biology.”

Expectation for the Creation of High Added Value Based on the Development of the Core Technology by Using the 3D Nanopatterning Technology

The core technology of the stretchable electronic element is related to the improvement of the stretchable limitation of commercialized materials or the development of new stretchable materials. However, the method that used to be applied in order to improve the stretchability of any credible material only focused on the process of making wrinkled films like those of an accordion or making holes with a puncher in order to establish a network structure like a fishing net. By using such a method, it was only possible to expect an increase stretchability by about 30% compared to the original level of stretchability shown by a particular material. Therefore, the research team led by Professor Seokwoo Jeon at KINC focused on the development of a technology that was significant in terms of engineering based on a totally different mechanism compared to any of the previously-suggested ones in order to realize a new kind of stretchable material. As a result, the team developed the manufacturing technology of ultra-stretchable elements by using the periodic 3D porous nanostructure.

From June 2010, while carrying out its research, the research team had a high level of interest in developing new materials with unconventional optical properties through the periodically nanostructured materials based on 3D nanopatterning technology, which could be used to manufacture a large-scale 3D nanostructure. During the research process, the team realized the largest periodic 3D nanostructure in the world and started to look for new applications beyond the consideration of optical properties. Then, it focused on the point that, if the nanostructure could be transformed into a rubberic materials, it could have an excellent level of stretchability, like a sponge. The team also thought that if the nanostructure was made of a countless number of invisible nanoholes at regular intervals rather than the macroholes forming a sponge at irregular intervals, the stretchability could be further improved and the nanostructure could be used as a stretchable platform for electronic devices.

In the initial stages of R&D, it only took four to five months to obtain experimental results based on the previous technologies and to be sure of the possibility of success for the target technology. It took about six to seven months more until a credible method was established for the measurement of material properties since there had been no case of carrying out a mechanical strength test for a thin rubber film whose thickness was only 1/10th that of a hair.

After obtaining experimentally significant results, in 2011, the research team led by Professor Seokwoo Jeon carried out a joint research project with the team led by Professor Yonggang Huang, a simulation expert from the Department of Mechanical Engineering, Northwestern University, in order to verify the results theoretically. After four to five months passed, a new mechanism for the improvement of elasticity, which had never been reported before, was established theoretically and matched with the research results successfully. Then, in order to certify the applicability of the newly developed 3D stretchable material, the world-leading conductive complex was developed over a period of about two months while the LED experiment was carried out. As stated above, it took one year and six months to develop the process, realize the new physical properties, carry out the theoretical certification process, and apply to stretchable devices after the related idea was established. It took six months until the related academic paper and the patent process were completed. Through such a process, it was possible to develop stretchable electronic elements based on the 3D nanopatterning technology.

The 3D nanopatterning technology, which has been autonomously possessed by the research team led by Professor Seokwoo Jeon, has the largest size in the world. By using it, it is possible to establish patterns more rapidly and uniformly than with other methods. As a result, the technology is evaluated to have the greatest level of possibility for commercialization. A thin rubber film, which has a periodic 3D nanoporous structure with a size of greater than 1 inch, could be made by using the technology. The stretchable limit of such an element is more than 60% higher than the original level. Also, when a liquid metal is put into the porous channel of the inside, it is also possible to maintain electrical conductivity.

Through such a process, a material with an excellent level of conductivity and stretchability can be developed. As an experiment to prove the level of conductivity and stretchability, LEDs can be connected to the established stretchable conductor. In such a case, it is possible to see that the level of brightness is not deteriorated, even in a state that is tensioned by 220%.

Until now, most of the technologies related to the stretchable elements for the next generation, including those related to stretchable displays or wearable computers, have been developed and patented by foreign research institutes through advanced research. However, it is still hard to find a core technology that can be standardized. In such a context, it is quite meaningful to see that a local research team led by Professor Seokwoo Jeon has developed innovative original technologies including a new mechanism for the realization of ultra-stretchable elements with no external help. If it is possible to carry out the process for mass production in the future through the roll-to-roll process or the metal sintering process, great contributions could be made to the production of ultra-light and ultra-strong components. Also, it is possible to expect high added values such as the application of the product as a coating material for the structure of the next-generation nuclear reactors or a structural material with a high level of reliability.

Prof. Jeon, Seokwoo
2013 Annual Report

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