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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 RSSNew 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.
Sticky questions tackled in gecko research
Velcro, Superglue and Post-It Notes- Three things that started out as obscure inventions but are now indispensable for everyday life. So what will the next idea to stick with modern society look like" The answer may lie in the tiny toes of a humble lizard, according to a University of Calgary biologist who is trying to figure out how geckos can cling to virtually any surface, including glass.
Synthetic adhesive mimics sticking powers of gecko and mussel
Geckos are remarkable in their ability to scurry up vertical surfaces and even move along upside down. Their feet stick but only temporarily, coming off of surfaces again and again like a sticky note. But put those feet underwater, and their ability to stick is dramatically reduced.
Nature's secrets yield new adhesive material
Scientists report they have merged two of nature's most elegant strategies for wet and dry adhesion to produce a synthetic material that one day could lead to more durable and longer-lasting bandages, patches, and surgical materials.
Nanotube Adhesive Sticks Better Than a Gecko's Foot
Mimicking the agile gecko, with its uncanny ability to run up walls and across ceilings, has long been a goal of materials scientists.
The original nanoworkout -- Helping carbon nanotubes get into shape
Researchers at Rensselaer Polytechnic Institute have developed a new method of compacting carbon nanotubes into dense bundles.
Fossilized liquid assembly: Nanomaterials research tool
From a butterfly's iridescent wing to a gecko's sticky foot, nature derives extraordinary properties from ordinary materials like wax and keratin.
Engineers create gecko-inspired, high-friction micro-fibers
Inspired by the remarkable hairs that allow geckos to hang single-toed from sheer walls and scamper along ceilings, a team of researchers led by engineers at the University of California, Berkeley, has created an array of synthetic micro-fibers that uses very high friction to support loads on smooth surfaces.
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