Navy scientists are tapping some of Mother Nature’s tricks in developing a new generation of water-repellant coatings for ship hulls and other applications.
Inspired by water striders that walk on water, butterflies that shed water from their wings, and similar phenomena, scientists at the Naval Research Laboratory are part of a research team that is working to engineer surfaces that imitate nature’s own water-repellent adaptations.
“This technology offers the possibility of significant advances for producing new generations of coatings that will be of great value for military, medical, and energy applications,” the team reports in its research, published in the December 2010 issue of Nature Materials.
Controlling the Flow
NRL’s Dr. Walter Dressick, Professor Melik Demirel of Pennsylvania State University, and Dr. Matthew Hancock of MIT have collaborated to create an engineered water-repellant thin film that can, for the first time, control the directionality of liquid transport, NRL reports.
In this system, parylene nanorods are deposited on the surface by a simple, straightforward vapor deposition method. The single step usually takes less than 60 minutes, compared with the more complex, multi-step lithography processes often used in previous systems, researchers say.
This is the first time this kind of surface has been engineered at the nanoscale, they say.
Reducing Friction, Fouling
In the newly created surface, the nanorods that form the film are smooth on a micron scale. Researchers are hopeful that this film could be used as a coating on ship hulls, to reduce drag and slow fouling.
The size and smoothness in the posts means that droplets move without being distorted in any way when they are placed on the surface. Droplets can also be moved without pumps or optical waves. Previous systems caused the water droplets to be distorted, which could rupture, spill, or destroy the cargo in the droplet when used in medical or microassembly applications.
|Water droplets are not distorted in any way on the anisotropic wetting surface, researchers say.|
As they continue the research, the scientists will focus on optimizing the droplet transport mechanism and tuning the preparation method.
The team also foresees industrial applications such as pump-free digital fluidic devices, increased efficiency of thermal cooling for microchips, and tire coatings.
The Office of Naval Research is providing the funding for this research. NRL, established in 1923, is the corporate research laboratory for the Navy and Marine Corps and conducts a broad program of scientific research, technology and advanced development.