Scientific breakthroughs are not often marked by one defining moment. Rather, a “breakthrough” typically comes at the end of a long, sequential process of experimentation, discovery, and refinement that builds upon itself. Bit by bit, scientists make incremental progress on solving a problem, and the results only look like a sudden breakthrough in the moment. In retrospect, it becomes clear that all the work that came before formed the building blocks of the scientific discovery.
From gene research and vaccine development, to GPS applications, you can see how the “experiment/advance/iterate” pattern repeats itself in science, leading to new discoveries that will be further built upon.
One area that has experienced significant advancements in recent decades is the development of superhydrophobic materials. Superhydrophobic materials are highly effective at repelling water, and therefore are used in a number of commercial applications such as preventing ice build-up on surfaces, water-proofing electronics and other objects, and making ships cut through the water more efficiently.
A whole range of new applications for superhydrophobic materials may soon be on the way thanks to work being done by scientists at the University of Rochester and the Changchun Institute of Optics, Fine Mechanics, and Physics in China. The researchers, through grants provided by the U.S. Army, the National Science Foundation, and the Bill and Melinda Gates Foundation, developed “unsinkable metals” that stay afloat, even when punctured, by using superhydrophobic materials.
How Superhydrophobic Materials Work
A superhydrophobic surface repels water by trapping air on the surface of objects. Tiny air bubbles make it hard for water to stick, so drops bounce or roll off instead of pooling on the surface. Superhydrophobic coatings are made from composite materials with two different properties: roughness and low surface energy. In nature, the leaf of a lotus plant exhibits the water repellant properties that man-made superhydrophobic materials mimic.
How Superhydrophobicity Supports Buoyancy
To create unsinkable metals, the scientists used ultra-fast laser pulses to etch microscale and nanoscale grooves into the surface of an aluminum disk. The etchings trapped large volumes of air, forming a protective barrier that allowed the metal to repel water via large contact angles, and consequently, float.
If the metal was submerged in water for a long period of time, however, the grooves would eventually fill up with water instead of air, causing the metal to lose its buoyancy. To remedy the problem, the researchers placed two of the etched metal disks facing each other, connected by a small pillar. A gap was formed in the center that was small enough to prevent water from entering but big enough to create an air bubble that allowed the metal object to float.
The metal was submerged underwater as part of the experiment to see if it would lose its buoyancy. After two months of being weighed down underwater, the metal still rose to the surface. Even drilling holes in the metal was not enough to make it sink.
Practical Applications for Superhydrophobic Metals
In the study, the researchers suggest that practical applications for unsinkable metals could include use in life rafts and buoyant clothing, building floating cities, or constructing highly floatable ships and vessels. In an interview with Business Insider, Chunlei Guo, the study's chief researcher, said that, “[t]he weight of the ship wouldn't matter...as long as the surface area of the metal was large enough to counterbalance it.”