A species of spider lives its entire life underwater, despite having lungs that can only breathe atmospheric oxygen. How does it do it? This spider, known as the Argyroneta aquatica, has millions of rough, water-repellent hairs that trap air around its body, creating an oxygen reservoir and acting as a barrier between the spider's lungs and the water.
This thin layer of air is called a plastron and for decades, material scientists have been trying to harness its protective effects. Doing so could lead to underwater superhydrophobic surfaces able to prevent corrosion, bacterial growth, the adhesion of marine organisms, chemical fouling, and other deleterious effects of liquid on surfaces. But plastrons have proved highly unstable under water, keeping surfaces dry for only a matter of hours in the lab.
Now, a team of researchers led by the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), the Wyss Institute for Biologically Inspired Engineering at Harvard, the Friedrich-Alexander-Universität Erlangen-Nürnberg in Germany, and Aalto University in Finland have developed a superhydrophobic surface with a stable plastron that can last for months under water. The team's general strategy to create long-lasting underwater superhydrophobic surfaces, which repel blood and drastically reduce or prevent the adhesion of bacterial and marine organisms such as barnacles and mussels, opens a range of applications in biomedicine and industry.
"Research in bioinspired materials is an extremely exciting area that continues to bring into the realm of man-made materials elegant solutions evolved in nature, which allow us to introduce new materials with properties never seen before," said Joanna Aizenberg, Amy Smith Berylson Professor of Materials Science and Professor of Chemistry & Chemical Biology at SEAS and co-author of the paper. "This research exemplifies how uncovering these principles can lead to developing surfaces that maintain superhydrophobicity under water."
Aizenberg is also an associate faculty member of the Wyss Institute.
The research is published in Nature Materials.
Researchers have known for 20 years that a stable, underwater plastron was theoretically possible but, until now, haven't been able to show it experimentally.
One of the biggest issues with plastrons is that they need rough surfaces to form, like the hair of Argyroneta aquatica. But this roughness makes the surface mechanically unstable and susceptible to any small perturbation in temperature, pressure, or tiny defect.
