Geckos are interesting animals. Have you ever thought, How geckos stick? Well, that’s the question people are trying to figuring out since the era of Aristotle. Their mystery of stickiness finally solved.
What is the secret behind geckos stickiness?
In the past, scientists tried to explain the phenomenon behind the stickiness of geckos. So they make many hypotheses about the stickiness of geckos like secretion, suction cups & tiny hooks, etc. but when scientists tested the hypothesis, none of them were true.
So, what is the mystery behind it, and how scientists solved it?
By that time Scientists had known that Geckos can stick to surfaces because their bulbous toes are covered in hundreds of tiny microscopic hairs called setae. Each seta splits off into hundreds of even smaller bristles called spatulae. but they didn’t know how these setae stick to the wall.
Regarding this, Two hypotheses had become quite famous: one that tropical geckos stick to the surface via a thin film of water. They thought that water molecules are polar in nature because of their unequal distribution of electronic charge.
So because of the opposite charge distribution, geckos can stick to the surface. This hypothesis is called Capillary (water-based) adhesion. And the 2nd hypothesis estimated that the stickiness of geckos is existed because of Van der Waals forces.
Scientist Name Kellar Autumn from Lewis & Clark College disproves the hypothesis of capillary adhesion and Solves the mystery behind geckos stickiness.
He and his colleagues work hard and find out the stickiness behind the geckos. The team tested two competing hypotheses: one based on van der Waals force and a second on capillary (water-based) adhesion.
“Our results provide the first direct experimental verification that a short-range molecular attraction called van der Waals force is definitely what makes geckos stick,” Autumn emphasizes.
Van der Waals forces, named after a Dutch physicist of the late 1800s, are weak electrodynamic forces that operate over tiny distances but bond to nearly any material.
Geckos have millions of setae—microscopic hairs on the bottom of their feet. These tiny setae are only as long as two diameters of human hair. That’s 100 millionths of a meter long.
Each seta ends with 1,000 even tinier pads at the tip. These tips, called spatulae, are only 200 billionths of a meter wide—below the wavelength of visible light.
Autumn Says, “Intermolecular forces come into play because the gecko foot hairs split and allow a billion spatulae to increase surface density and come into close contact with the surface. This creates a strong adhesive force”.
A single seta can lift the weight of an ant. A million setae, which could easily fit onto the area of a dime, could lift a 45-pound child. If a gecko used all of its setae, at the same time, it could support 280 pounds.
Words by Keller Autumn, “Our previous research suggested that van der Waals forces could explain gecko adhesion. But we couldn’t rule out water adsorption or some other types of water interaction. With our new data, we can finally disprove a 30-year-old theory based on the adhesion of water molecules.”