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As Sticky as a Gecko ... but Ten Times Stronger!
October 15, 2008The gecko's amazing ability to stick to surfaces and walk up walls has inspired many researchers to manufacture materials that mimic the special surface of a gecko's foot. The secret behind the gecko's ability to stick so well is a forest of pillars at the micro-/nano-scale on the underside of the gecko's foot. Because there are so many pillars so close together, they are held tightly to the surface the gecko is walking on by a molecular force called the Van der Waals force. This relatively weak force causes uncharged molecules to attract each other.
In an unprecedented feat, Liming Dai, at the University of Dayton, and colleagues report in the October 10th issue of Science successful construction of a gecko-inspired adhesive that is ten times stronger than a gecko, at about 100 newtons per square centimeter.
The researchers constructed their adhesive out of two slightly different layers of multi-walled carbon nanotubes. The lower layer is composed of vertically-aligned carbon nanotubes, while the upper segment--which comes into contact with the surface it is sticking to--is curly, like a mess of spaghetti.
As shown in the figure, the adhesive sticks best when it is pulled down parallel to the surface it is sticking to--this is called shear adhesion. This action arranges the tips of the curly nanotubes so they have maximum contact with the substrate, thereby maximizing the Van der Waals force. Pulling the adhesive off in a motion perpendicular to the substrate is much easier--at this angle the sticking force is ten times weaker.
In this way, the adhesive has strong shear adhesion for firm attachment and relatively weak adhesion for detachment perpendicularly to the substrate. Just like a gecko, the adhesive can stick to a wall when needed, and then lift off easily to take the next step. This breakthrough, supported by the National Science Foundation, will have many technological applications.
The National Science Foundation (NSF)
As shown in the figure, the adhesive sticks best when it is pulled down parallel to the surface it is sticking to--this is called shear adhesion. This action arranges the tips of the curly nanotubes so they have maximum contact with the substrate, thereby maximizing the Van der Waals force. Pulling the adhesive off in a motion perpendicular to the substrate is much easier--at this angle the sticking force is ten times weaker.
In this way, the adhesive has strong shear adhesion for firm attachment and relatively weak adhesion for detachment perpendicularly to the substrate. Just like a gecko, the adhesive can stick to a wall when needed, and then lift off easily to take the next step. This breakthrough, supported by the National Science Foundation, will have many technological applications.
The National Science Foundation (NSF)
Gecko Current Events and Gecko News RSSFlips, flops and cartwheels
Geckos and other lizards have long been known for their incredible ability to shed their tails as a decoy for predators, but little is known about the movements and what controls the tail once it separates from the lizard's body.
Hundreds of New Species Discovered in Fragile Eastern Himalayas
Over 350 new species including the world's smallest deer, a "flying frog" and a 100 million-year old gecko have been discovered in the Eastern Himalayas, a biological treasure trove now threatened by climate change.
Bizarre walking bat has ancient heritage
A bizarre New Zealand bat that is as much at home walking four-legged on the ground as winging through the air had an Australian ancestor 20 million years ago with the same rare ability, a new study has found.
Neon blue-tailed tree lizard glides like a feather
Most lacertid lizards are content scurrying in and out of nooks and crannies in walls and between rocks. However, some have opted for an arboreal life style.
'Gecko vision': Key to the multifocal contact lens of the future?
Nocturnal geckos are among the very few living creatures able to see colors at night, and scientists' discovery of series of distinct concentric zones may lead to insight into better cameras and contact lenses.
New species of spiders discovered by UBC scientist in Papua New Guinea
A University of British Columbia researcher has discovered dozens of species of jumping spiders that are new to science, giving scientists a peek into a section of the evolutionary tree previously thought to be sparse.
Genetic study finds treasure trove of new lizards
University of Adelaide research has discovered that there are many more species of Australian lizards than previously thought, raising new questions about conservation and management of Australia's native reptiles.
New gecko-like adhesive shakes off dirt
Researchers at the University of California, Berkeley, are continuing their march toward creating a synthetic, gecko-like adhesive, one sticky step at a time. Their latest milestone is the first adhesive that cleans itself after each use without the need for water or chemicals, much like the remarkable hairs found on the gecko lizard's toes.
New family of gecko discovered by researchers from the U of Minnesota and Villanova University
Researchers at the University of Minnesota's Bell Museum of Natural History and Pennsylvania's Villanova University have discovered a new family of gecko, the charismatic large-eyed lizard popularized by car insurance commercials.
MIT creates gecko-inspired bandage
MIT researchers and colleagues have created a waterproof adhesive bandage inspired by gecko lizards that may soon join sutures and staples as a basic operating room tool for patching up surgical wounds or internal injuries.
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Company's Coming DBP-074 Gecko Painted Doorbell Cover by Company's Coming 1/2" Diameter, Painted Gecko, Lighted Door Chime Push Button, With Solid Brass Mounting Screws, 4" x 3", Hard Wired, Maximum Voltage, 16V. |
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