Geckos are known for their grippy feet which allow them to scale vertical surfaces. This superpower comes from millions of microscopic, hairlike structures on their toes. Scientists already understood gecko adhesion, but now have a clearer picture of the molecular structures that give the animal its grip.
In a study from the National Institute of Standards and Technology (NIST), researchers analyzed the setae by zooming in using X-rays called a synchrotron. The experts discovered that the structures are coated in an ultra-thin film of water-repelling lipid molecules.
Setae are flexible and assume the microscopic contours of any surface the gecko is climbing. To release its foot, the gecko changes the angle of the setae, interrupting those forces and allowing the animal to take its next step.
These lipids are hydrophobic, meaning they repel water. “The lipids might function to push away any water beneath the spatulae, allowing them to make closer contact with the surface,” said study co-author Tobias Weidner of Aarhus University in Denmark. “This would help geckos maintain their grip on wet surfaces.”
The setae are made of a keratin protein similar to that found in human hair and fingernails which are extremely delicate. These keratin fibers are aligned in the direction of the setae, which might help them resist abrasion.
“You can imagine gecko boots that don’t slip on wet surfaces, or gecko gloves for holding tools that are wet,” said NIST physicist and study co-author Dan Fischer. “Or a vehicle that can run up walls, or a robot that can run along power lines and inspect them.”
The NIST synchrotron microscope can uniquely identify molecules on the surface of a three-dimensional object, measure their orientation and map their position. It is located at the U.S. Department of Energy’s Brookhaven National Laboratory, where the National Synchrotron Light Source II provides a source of high-energy X-rays for illumination.
This microscope is typically used on advanced industrial materials, including batteries, semiconductors, solar panels and medical devices. “But it is fascinating to figure out how gecko feet work, and we can learn a lot from nature when it comes to improving our own technology,” said Fischer.
“A lot was already known about how setae work mechanically,” said study co-author Cherno Jaye. “Now we have a better understanding of how they work in terms of their molecular structure.”
Geckos have inspired many products like adhesive tapes. Understanding the molecular features of setae could further inspire inventors to mimic nature in design, a concept called biomimicry.