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Geckos and Their Sticky Feet

2002-9-5

This is the VOA Special English ENVIRONMENT REPORT.

Geckos are small lizards that livein warm climates. These lizards can stick to any surface. Forexample, geckos can climb up walls and across the top of a room.Scientists have studied the little lizards for hundreds of years tolearn the secret of how they stick to things. Now, they say theyhave finally solved the mystery. They hope the finding will helpthem develop powerful materials that hold things together.

A team of American biologists and engineers carried out thestudy. Their findings were published in the Proceedings of theNational Academy of Sciences.

Geckos have millions of very smallhairs on their toes. The end of each hair splits into as many asone-thousand smaller hairs. So the gecko's foot has hundreds ofmillions of tiny hairs that touch a surface.

Scientists have debated the purpose of these hairs. Some thoughtthe hairs dug into a surface. Others thought geckos released anatural sticky substance onto their hairy toes to hold onto asurface, like a leaf, and prevent enemies from pulling them loose.

Over the years, scientists have put geckos into water to see ifthey would stick. They do. They have dropped them into strongdevices, but their sticking ability was not weakened. Scientistsalso have used radiation to neutralize static electricity. Theythought electrostatic force helped the animals hold on to a surface.

Scientists say the gecko's sticking power comes from somethingcalled the van der Waals force. The term was named after the Dutchscientist who first described it more than one-hundred years ago.The force is the attraction between molecules at the ends of thegecko's toe hairs and the surface of an object. When molecules areso close together, the unbalanced electrical charges around themolecules can attract one another. This provides the attractionbetween the foot of the gecko and a wall or other object.

The scientists showed that a single gecko toe hair has enoughholding power to lift an insect. They say a small group of hairs thesize of a coin could possibly lift a small child.

Scientists say they have created the first sticky substance basedon the geckos' hairs. They hope to use the powerful substance todevelop new products. The scientists recently joined with a companyto develop robots that can climb walls.

This VOA Special English ENVIRONMENT REPORT was written byCynthia Kirk.