Creating superhydrophobic surfaces with salt

In nature, one can observe such ultrahydrophobicity on a lotus leaf. The leaf has microscopic protrusions on its surface which minimizes adhesion. As a result, water droplets along with any dirt particles on the surface simply roll right off the leaf. This effect is appropriately referred to the “lotus effect.”

Complicated procedures

There have been numerous research into applying the “lotus effect” to other surfaces via simulating similar micro- and nanoscopic surface architectures. Anti-icing, anti-sticking, and self-cleaning characteristics are but a few of the many real-world applications of superhydrophobic surfaces. However, while the idea of a stain repellent fabric or a self-cleaning building is revolutionary, existing methods of applying a superhydrophobic layer required complicated procedures with exorbitant equipment costs and/or harsh chemicals.

Overcoming the barriers

Professor Dong Sung Kim’s research team from the Department of Mechanical Engineering at Pohang University of Science and Technology (POSTECH), has successfully overcome these barriers by utilising a salt-dissolution-assisted etching process. Taking advantage of the fact that salt readily dissolves in water, the team exposed a salt-particle-embedded PDMS surface to an aqueous environment. The remaining PDMS surface becomes roughened with micro/nano-hierarchical topography which satisfy the standards of superhydrophobic surfaces. Furthermore, this elegant process can readily be applied to large or three-dimensional surfaces.

Professor Kim anticipates that the salt-dissolution-assisted etching process will be utilised in various fields for numerous applications thanks to its malleable, cost-effective, and environmentally friendly process.