"For this work, we have developed a fabrication approach based on self assembly of nanostructures, which lets us precisely control the surface texture geometry over as large an area as we want-in principle, even as large as square meters," Checco said.
The procedure for creating these superhydrophobic nanostructured surfaces, developed in collaboration with scientists at Brookhaven's Center for Functional Nanomaterials (CFN), takes advantage of the tendency of "block copolymer" materials to spontaneously self-organize through a mechanism known as microphase separation. The self-assembly process results in polymer thin films with highly uniform, tunable dimensions of 20 nanometers or smaller. The team used these nanostructured polymer films as templates for creating nanotextured surfaces by combining with thin-film processing methods more commonly used in fabricating electronic devices, for example by selectively etching away parts of the surface to create textured designs.
"This new approach leverages our thin-film processing methods, in order to precisely tailor the surface nanotexture geometry through control of processing conditions," said Brookhaven physicist and co-author Charles Black.
The effect of shape
The scientists created and tested new materials with different nanoscale textures-some decorated with tiny straight-sided cylindrical pillars and some with angle-sided cones. They were also able to control the spacing between these nanoscale features to achieve robust water repellency.
After coating their test materials with a thin film of wax-like material, the scientists measured how water droplets rolled off each surface as they were tilted from vertical to flat positions and compared the behavior with that of untextured solids.'/>"/>
|Contact: Karen McNulty Walsh|
DOE/Brookhaven National Laboratory