Working at Lewis & Clark College, the University of California at Berkeley, the University of California at Santa Barbara, and Stanford University, the interdisciplinary team:
* confirmed speculation that the gecko’s amazing climbing ability depends on weak molecular attractive forces called van der Waals forces,
* rejected a competing model based on the adhesion chemistry of water molecules, and
* discovered that the gecko’s adhesive depends on geometry, not surface chemistry. In other words, the size and shape of the tips of gecko foot hairs—not what they are made of—determine the gecko’s stickiness.
To verify its experimental and theoretical results, the gecko group then used its new data to fabricate prototype synthetic foot-hair tips from two different materials.
“Both artificial setal tips stuck as predicted,” notes Autumn, assistant professor of biology at Lewis & Clark College in Portland, Ore. “Our initial prototypes open the door to manufacturing the first biologically inspired dry, adhesive microstructures, which can have widespread applications.”
Geckos have millions of setae—microscopic hairs on the bottom of their feet. These tiny setae are only as long as two diameters of a human hair. That’s 100 millionth 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.
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,” says Autumn.
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
gecko
Why van der Waals? Although they are the weakest type of intermolecular force, they are ubiquitous and occur between all types of surfaces. This means that the key to dry adhesion is the shape or geometry of the adhesive, rather than the chemistry. Other insects which stick by secretions (e.g. ants, beetles, flies, etc.) are much more picky about what types of surfaces they stick to. Geckos can stick to any surface, with the exception of Teflon, which was specifically engineered to prevent even van der Waals adhesion. (You might say that Teflon is the Anti-Gecko.)
Dry adhesives such as these have evolved independently multiple times within gekkonid lizards, as well as in anoles, skinks, and multiple times again in spiders. This highly diverse set of organisms allows us to conduct statistically powerful comparative studies to determine how adhesive feet evolved and what benefits they confer on the animals which possess them.
anne peattie
* confirmed speculation that the gecko’s amazing climbing ability depends on weak molecular attractive forces called van der Waals forces,
* rejected a competing model based on the adhesion chemistry of water molecules, and
* discovered that the gecko’s adhesive depends on geometry, not surface chemistry. In other words, the size and shape of the tips of gecko foot hairs—not what they are made of—determine the gecko’s stickiness.
To verify its experimental and theoretical results, the gecko group then used its new data to fabricate prototype synthetic foot-hair tips from two different materials.
“Both artificial setal tips stuck as predicted,” notes Autumn, assistant professor of biology at Lewis & Clark College in Portland, Ore. “Our initial prototypes open the door to manufacturing the first biologically inspired dry, adhesive microstructures, which can have widespread applications.”
Geckos have millions of setae—microscopic hairs on the bottom of their feet. These tiny setae are only as long as two diameters of a human hair. That’s 100 millionth 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.
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,” says Autumn.
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
gecko
Why van der Waals? Although they are the weakest type of intermolecular force, they are ubiquitous and occur between all types of surfaces. This means that the key to dry adhesion is the shape or geometry of the adhesive, rather than the chemistry. Other insects which stick by secretions (e.g. ants, beetles, flies, etc.) are much more picky about what types of surfaces they stick to. Geckos can stick to any surface, with the exception of Teflon, which was specifically engineered to prevent even van der Waals adhesion. (You might say that Teflon is the Anti-Gecko.)
Dry adhesives such as these have evolved independently multiple times within gekkonid lizards, as well as in anoles, skinks, and multiple times again in spiders. This highly diverse set of organisms allows us to conduct statistically powerful comparative studies to determine how adhesive feet evolved and what benefits they confer on the animals which possess them.
anne peattie
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