A novel and practical fab-route for superomniphobic liquid-free surfaces
A joint research team led by Professor Hee Tak Kim and Shin-Hyun Kim in the Department of Chemical and Biomolecular Engineering at KAIST developed a fabrication technology that can inexpensively produce surfaces capable of repelling liquids, including water and oil.
The team used the photofluidization of azobenzene molecule-containing polymers to generate a superomniphobic surface which can be applied for developing stain-free fabrics, non-biofouling medical tubing, and corrosion-free surfaces.
Mushroom-shaped surface textures, also called doubly re-entrant structures, are known to be the most effective surface structure that enhances resistance against liquid invasion, thereby exhibiting superior superomniphobic property.
However, the existing procedures for their fabrication are highly delicate, time-consuming, and costly. Moreover, the materials required for the fabrication are restricted to an inflexible and expensive silicon wafer, which limits the practical use of the surface.
To overcome such limitations, the research team used a different approach to fabricate the re-entrant structures called localized photofludization by using the peculiar optical phenomenon of azobenzene molecule-containing polymers (referred to as azopolymers). It is a phenomenon where an azopolymer becomes fluidized under irradiation, and the fluidization takes place locally within the thin surface layer of the azopolymer.
SEM image of mushroom-shaped structure. Credit: KAIST
With this novel approach, the team facilitated the localized photofluidization in the top surface layer of azopolymer cylindrical posts, successfully reconfiguring the cylindrical posts to doubly re-entrant geometry while the fluidized thin top surface of an azopolymer is flowing down.
The structure developed by the team exhibits a superior superomniphobic property even for liquids infiltrating the surface immediately.
Moreover, the superomniphobic property can be maintained on a curved target surface because its surficial materials are based on high molecules.
Furthermore, the fabrication procedure of the structure is highly reproducible and scalable, providing a practical route to creating robust omniphobic surfaces.
Image of superomniphobic property of different types of liquid. Credit: KAIST
Professor Hee Tak Kim said, “Not only does the novel photo-fluidization technology in this study produce superior superomniphobic surfaces, but it also possesses many practical advantages in terms of fab-procedures and material flexibility; therefore, it could greatly contribute to real uses in diverse applications.”
Professor Shin-Hyun Kim added, “The designed doubly re-entrant geometry in this study was inspired by the skin structure of springtails, insects dwelling in soil that breathe through their skin. As I carried out this research, I once again realized that humans can learn from nature to create new engineering designs.”
Flexible and Robust Superomniphobic Surfaces Created by Localized Photofluidization of Azopolymer Pillars
Springtails, insects which breathe through their skins, possess mushroom-shaped nanostructures. As doubly re-entrant geometry in the mushroom head enhances the resistance against liquid invasion, the springtails have robust, liquid-free omniphobic skins.
Although omniphobic surfaces are promising for various applications, it remains an important challenge to mimic the structural feature of springtails.
This paper presents a pragmatic method to create doubly re-entrant nanostructures and robust superomniphobic surfaces by exploiting localized photofluidization of azopolymers.
Irradiation of circularly polarized light reconfigures azopolymer micropillars to have a mushroom-like head with a doubly re-entrant nanogeometry through protrusion and inward bending of polymer film from the top edge.
The light-driven reconfigured micropillars facilitate the pining of triple line as the springtails do.
In particular, the unique geometry exhibits superomniphobicity even for liquids whose equilibrium contact angles are almost zero in the presence of a practical level of external pressure. In addition, the simple fabrication process is highly reproducible, scalable, and compatible with various substrate materials including flexible polymeric film.
Our results suggest that our photofluidization technology will provide a practical route to develop robust superomniphobic surfaces.
Scientists Develop Superomniphobic, The potential for this is huge. You can use it on smartphone screens, glasses, and cameras to avoid rain or water damage. You can also use it in the medical industry, and even in the food industry – to make sure that you can get every last bit from that ketchup bottle, for example. The potential for this is truly endless, but it all relies on two factors: price and durability.
Scientists Develop Superomniphobic, This research mostly targets price and the ease with which such a surface can be developed. However, in terms of durability, achieving the desired outcome is still a challenge. Kota and others working in the field definitely have a lot on their hands, but for now, they already have a few interested customers: the packaging industry, which doesn’t really need durable products – just cheap and efficient.
Scientists Develop Superomniphobic, surfaces repel all liquids. They generally feature an air cushion which lies between a liquid and a solid surface. Now, Arun Kota, assistant professor of mechanical engineering at Colorado State University has made a surface which can adhere to anything, giving it strong liquid-repelling properties.
Scientists Develop Superomniphobic, The concept isn’t completely new, as researchers have been working in the field since 2007. However, this time it’s different. Kota’s breakthrough is notable not only in terms of overall efficiency, but especially in terms of the method through which the surface was developed. Previously, superomniphobic surfaces were extremely complex and very expensive and could only be created by trained professionals. But now, with doctoral student Hamed Vahabi and postdoctoral fellow Wei Wang, Kota developed a relatively simple technique through which this can be achieved – and anyone can do it. Go to Source