Nanoimprinting technique for moisture-sensitive holographic images – Zoo House News
A magical display has been developed that projects holographic images that change on contact with water. This new technology increases the possibilities of commercialization as it can infinitely imprint holographic images.
A POSTECH research team led by Professor Junsuk Rho (Faculty of Mechanical Engineering and Faculty of Chemical Engineering) and Ph.D. The candidates Byoungsu Ko, Younghwan Yang, Jaekyung Kim and Dr. Trevon Badloe have developed a humidity-sensitive display technology that changes brightness and color depending on the level of humidity.
The team successfully realized brightness-adjustable holographic images for the first time using polyvinyl alcohol (PVA). This material is so flexible that it’s typically used for liquid glue or slime, and one of its defining characteristics is that it swells with increasing humidity. A holographic image that is clear at a low humidity level will gradually become unclear as humidity increases.
In addition, the team developed a display on which structural colors can be matched as desired. A blue image when humidity is low turns red as humidity increases. If the humidity is finely adjusted, all RGB colors can be expressed in addition to the two colors.
This study also draws attention to the team’s success in using the one-step nanoimprinting technique to print the images. It is remarkable that images can be vividly expressed even on a flexible substrate. In addition, since a single pixel of this display – reaching 700nm (1nm = 1/1 billion m) – is smaller than that of currently commercialized displays, it is expected to become the core technology for nanostructured displays.
The results of the study attracted a lot of attention because the newly developed security label technology can be used to authenticate against counterfeit goods, including items such as whiskey, banknotes or passports. The team has worked with Korea Minting and Security Printing Corporation (KOMSCO) to apply optics-based future security technology to actual products. This technology will then be applied to the development of a hydrogel macromolecule-based display that responds to external stimuli such as heat, acidity (pH) and particulate matter pollution.
These results on the brightness and color tunability of holographic images were published in the international journals Nature Communications and Advanced Science, respectively.
This research was supported by the Samsung Science & Technology Foundation, the National Research Foundation’s Pioneer Program of Future Technology under the Ministry of Science and ICT, and the POSCO-funded POSCO-POSTECH-RIST Convergence Research Center program.
Materials provided by Pohang University of Science & Technology (POSTECH). Note: Content can be edited for style and length.