Nanotube carpet mimics gecko feet.
The talented gecko gecko (gĕk`ō), small or medium-sized lizard of the family Gekkonidae. The more than 300 species are distributed throughout the warm regions of the world, mostly in the Old World. Despite folklore to the contrary, their bite is not poisonous. can walk up a glass wall or hang from the ceiling by only one toe. The little lizard owes its gravity-defying powers to carpets of microscopic hairs, called setae, covering its feet. These hairs, when in close contact with a surface, induce intermolecular Adj. 1. intermolecular - existing or acting between molecules; "intermolecular forces"; "intermolecular condensation" attractive forces called van der Waals forces van der Waals forces: see intermolecular forces.
van der Waals forces
Relatively weak electrical forces that attract neutral (uncharged) molecules to each other in gases, liquefied and solidified gases, and almost all organic liquids and solids. between themselves and the surface (SN: 7/15/00, p. 47).
Materials scientists have now created synthetic gecko foot hairs that stick to surfaces 200 times as strongly as the setae do. To make this superstrong adhesive, Ali Dbinojwala of the University of Akron Enrollment in fall 2006 was 23,539 students. The school offers more than 200 undergraduate degrees  and 100 graduate degrees . The University's best-known program is its College of Polymer Science and Polymer Engineering, which is located in a in Ohio and his colleagues grew a forest of carbon nanotubes See nanotube. on glass. Next, they poured a liquid chemical onto the glass. The chemical solidified into a polymer matrix around the base of the tubes. The team then peeled the resulting polymer-nanotube "rug" off the glass.
Using an atomic-force microscope, Dhinojwala and his colleagues measured just how powerfully adhesive their synthetic invention was, compared with gecko setae. They report the result in the July Chemical Communications Chemical Communications, known as ChemComm, is a peer-reviewed scientific journal. Published weekly by the Royal Society of Chemistry (RSC), it contains communications .
Previous efforts to imitate gecko feet used tiny rods made from polymide, a plastic (SN: 6/07/03, p. 356). Unfortunately, says Dhinojwala, the plastic rods "are not mechanically strong, and they try to clump together" He attributes the carbon nanotubes' extraordinary adhesion to both van der Waals forces and to their strength and flexibility under strain.
Carbon-nanotube carpets could eventually serve as dry adhesives in applications where moisture would be a problem, such as in electronics, Dhinojwala says.