A Cheap Way To Make Materials Repel Both Water And Oil

By melting the top of cylindrical posts, researchers have created mushroom-shaped nanostructures that give materials the ability to repel both water and oil.

AsianScientist (Sep. 14, 2017) – A joint research team led by Professors Kim Hee Tak and Kim Shin-Hyun from the Korea Advanced Institute of Science and Technology (KAIST) has developed an inexpensive way to produce surfaces capable of repelling liquids, including water and oil. Their results, published in ACS Nano, could lead to affordable stain-free fabrics, non-biofouling medical tubing and corrosion-free surfaces.

Unlike hydrophobic and oleophobic surfaces which repel water and oil respectively, omniphobic surfaces repel any liquid, whether it is water- or oil-based. Mushroom-shaped surface textures—also called doubly re-entrant structures—are known to be the most effective omniphobic surface structure. However, the existing procedures to fabricate such structures are highly delicate, time-consuming and costly. Moreover, the materials required for the fabrication are restricted to an inflexible and expensive silicon wafer, limiting 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. They exploited the fact that azobenzene molecule-containing polymers (azopolymers) become fluidized under irradiation, using irradiation to locally fluidize the azopolymers within a thin surface layer.

With this novel approach, the team successfully fluidized the top surface layer of cylindrical posts made of azopolymers, reshaping them to the required mushroom shape. The resulting structure exhibits a superior superomniphobic property even for liquids infiltrating the surface immediately.

Furthermore, the fabrication procedure of the structure is highly reproducible and scalable, providing a practical route to creating robust omniphobic surfaces.

“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,” said Professor Kim Hee Tak.

“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,” added Professor Kim Shin-Hyun Kim.

The article can be found at: Choi et al. (2017) Flexible and Robust Superomniphobic Surfaces Created by Localized Photofluidization of Azopolymer Pillars.


Source: Korea Advanced Institute of Science and Technology.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.

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