Communications of the ACM
Research Gives Clues For Self-Cleaning Materials, Water-Striding Robots
Computer image of virtual water droplet on pillars
University of Nebraska-Lincoln
Scientists at the University of Nebraska-Lincoln (UNL) and Japan's RIKEN institute recently completed research that could lead to self-cleaning walls, counter tops, and fabrics, or micro-robots capable of walking on water. The research is based on a property called super hydrophobia. "A lot of people study this and engineers especially like the water strider because it can walk on water," says UNL professor Xiao Cheng Zeng. "A lot of scientists and engineers want to develop surfaces that mimic this from nature."
Organisms such as caterpillars, water striders, or the lotus use a two-level structure to achieve super hydrophobia. A hydrophobic waxy surface is made super hydrophobic with microscopic hair-like structures, or pillars, that could be covered in even smaller hairs, significantly increasing the surface area of the organism and making it impossible for water to stick. The supercomputer at RIKEN was used to design a computer simulation that performs tens of thousands of experiments on how surfaces behaved under different conditions. The computer was then used to "rain" virtual water droplets of different sizes and at different speeds onto surfaces with pillars of different heights and widths. The researchers found that there is a critical pillar height, based on the particular structure of the pillars and their chemical properties, beyond which water droplets cannot penetrate.
"This kind of simulation — we call it 'computer-aided surface design' — can really help engineers in designing a better nanostructured surface," Zeng says.
From University of Nebraska-Lincoln
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