A new nano-coating that can pull water out of the air might allow us to harvest water where there seems to be none, like the moisture farms in Star Wars. The coating is based on naturally occurring moisture-gathering mechanisms, such as the spines of a cactus and the bumpy shell of a desert beetle.
Researchers at Harvard University have modeled their new material on the shell of the Namib desert beetle, but they’ve also taken aspects of cactus spines and the slippery surface of the pitcher plant. This mix-and-match approach to biomimicry is itself a radical notion.
“Everybody is excited about bio-inspired materials research,” researcher Joanna Aizenberg told Harvard News. “However, so far, we tend to mimic one inspirational natural system at a time. Our research shows that a complex bio-inspired approach, in which we marry multiple biological species to come up with non-trivial designs for highly efficient materials with unprecedented properties, is a new, promising direction in biomimetics.”
The key was in realizing that the shape of the bumps on the Namib beetle’s shell is as important to its water-gathering abilities as the shell’s chemistry. Previous research has concerned itself solely with this chemistry, which combines a water-attracting top with water-repelling sides, effectively forcing any water that condenses onto the shell to roll up to the top, where it can gather. The GIFs on this page show you how it works.
The research team realized that shape was also playing a significant role, enough that shape alone could be enough to pull water from the air. They pulled together a hybrid material based on other water-attracting shapes, a kind of greatest-hits of hydrophilic forms. “Bumps that are rationally designed to integrate these mechanisms are able to grow and transport large droplets even against gravity and overcome the effect of an unfavorable temperature gradient, says the paper.
The material uses the beetle bumps, modified to ape the asymmetric cactus splines, and coated with the ultra-slippery surface of the pitcher plant. The resulting hybrid not only allows the harvesting of water from air, but has other, more industrial, uses.
For example, thermal power plants could use the coating to speed up the conversion of steam back to liquid water. “This design could help speed up that process and even allow for operation at a higher temperature, significantly improving the overall energy efficiency,” says co-author Philseok Kim.
The next step in the research, says Kim, is “developing a passive system that can efficiently collect water and guide it to a reservoir.” If achievable, this could be a big deal in arid, water-deficient areas.
Cover Photo: Kichigin via Shutterstock