It is indeed not the first time that people claim to have made something “unsinkable”. The famous Titanic was also considered unsinkable. Yet in 1912 the ship came across an iceberg and was swallowed up by the waves. Guo, however, dares to say that the metal developed in his studies really does not sink. “We have scientifically demonstrated that this metal cannot sink, no matter how many holes you drill into it or how often you push it into the water,” he says. “So we base ourselves on a scientific principle and not on trust in technology, such as the Titanic.”
Water spiders and fire ants
The researchers were inspired by this idea by learning from diving water spiders and the rafts of fire ants. These animals can stay on or even below the water surface for a long time. How? By catching air in an enclosed space. For example, the water spider weaves a dome-shaped web and uses air from the surface to fill the web. This air is retained by the hairs on the abdomen. This allows the water spider to stay underwater for a long time and simply breathe through. In addition, fire ants can form a raft together by clinging to each other. This keeps air bubbles between the bodies, so they do not drown.
The researchers decided to copy something similar. “The most important insight is that superhydrophobic surfaces can capture a large amount of air,” the researchers note. Something they had already done extensive research in the past for making superhydrophobic metals. “When I realized that spiders and ants also depend on their hydrophobic body surfaces, it was natural for me to make the connection,” Guo adds when asked. The researchers decided to use superhydrophobic surfaces to make floating objects. They tested this in the laboratory. They fired laser beams at a flat piece of metal to etch very small patterns onto the surface. These retain air and make the piece of metal water-repellent in this way. The inside of two aluminum plates was treated with this technique and then made together. The two plates do not touch each other completely but have exactly the right distance so that they retain enough air to float the structure.
Watch how it works in this video.
This method proves extremely effective. “It is this superhydrophobic effect that keeps the metal completely watertight and floating under all conditions,” Guo explains. The superhydrophobic surfaces prevent water from entering the compartment, even when the metal is submerged in water. It doesn’t matter how long. Because even after the metal was held underwater for two months, it immediately bounced back to the water surface when the weight of the metal was lifted. In addition, the researchers drilled several holes in the metal to see if it still worked. But even pierced with holes, the metal just floats. A great achievement. “Metals are heavy and do not naturally remain on the surface of the water,” says Guo. “It is therefore quite difficult to float a metal structure. And we have now achieved that. “
Thanks to this groundbreaking technology, potentially unsinkable ships are still on the horizon. “Metals are typical building materials for almost all sea-going vessels and boats,” says Guo. “It is therefore of great importance to investigate the potential of unsinkable metals. I hope that our study contributes to a series of new applications. Not only for ships but also for example for lifejackets or electronic devices that are used at sea and can no longer sink to the bottom.”