Liming Dai of the University of Dayton and Zhong Lin Wang of the Georgia Institute of Technology reported that they have developed a super Post-It material that can come unstuck with a deliberate tug, but is 10 times stickier than the feet of some geckos and lizards:

Liming Dai and Zhong Lin Wang said that they developed their artificial setae by growing nested carbon nanotubes on a silicon wafer. The researchers controlled the growth process to make a forest of vertical nanotube trunks turning into a canopy of tangled ends on top. The curly entangled mess acted like natural spatulae: when pressed against a surface, they had a large contact area and hence a strong hold.

The group tested the new material for stickiness on surfaces ranging from Teflon to sandpaper. It was found that when attached to a glass surface, a single square centimetre of it could support 1600g when pulled roughly parallel to the surface, three times better than the best artificial competitor.

No word yet as to whether the researchers have tested it by attempting to scale a skyscraper.

Spider-Man's sticky suit gets real [The Times of India]

A release describing the new microfiber explains:

Taking a cue from the millions of hairs covering a gecko's toes, researchers squeezed 42 million hard plastic microfibers onto each square centimeter of material and loaded it with various weights. They found that on a smooth, clean, vertical surface, two square centimeters of the synthetic adhesive could hold 400 grams (0.88 pounds). At the same time, the adhesive easily lifts off with minimal force and no residue . . . Previous research on gecko-like adhesives has focused on the strength of the adhesion . . . However, that the ease of attachment and detachment are equally important when developing a material that can practically be used for scaling vertical walls and ceilings.

What sets this new gecko-inspired adhesive apart from the others created thus far is that it is directional, only "sticking" when it slides along a smooth surface, not when it is pressed down. "This difference is critical because if you're climbing up vertical surfaces, you can't afford to use a lot of energy pressing down into the surface to stick," said [UC Berkeley EECS professor Ron] Fearing. "Using force to attach also requires force to detach. A gecko running uphill may be attaching and detaching its feet 20 times a second, so it'd get very tired if it had to work hard to pull its feet off at every step." The microfibers, made of polypropylene, are 20 microns long, or one-fifth the thickness of a sheet of paper, with a diameter of 0.6 microns, or one-hundredth the diameter of a human hair.

New Adhesive Mimics Gecko Toe Hairs [Eurekalert]