Mimicking the Geckos' Ability To Defy Gravity

In the same way that a gecko can run up sheer surfaces, robots may soon be able to scale vertical walls thanks to a new adhesive tape created by UC Berkeley engineers.

The engineers have developed a new type of tape that mimics the gecko hairs' unique "easy-to-attach and easy-to-release" effect on surfaces, said Ronald Fearing, professor of electrical engineering and computer sciences at UC Berkeley.

The tape leaves barely any residue on surfaces and is easier to remove than Scotch tape, Fearing said.

For many years, engineers had been trying to create a synthetic material with the gecko's ability to stick to surfaces.

The engineers' first concern was how humans grasp onto objects-or the surface of a wall-using their bare hands. Knowing this would help the engineers develop a robot capable of grasping objects.

To approach the problem, the engineers modeled their adhesive from the way geckos walk on surfaces. According to Fearing, geckos gently drag their feet parallel to surfaces.

"Our material doesn't stick when you press in, only when you drag it along parallel to the surface," he said.

The tape was also modeled off the structure of the millions of tiny hairs on a gecko's toes. Each hair fiber has one-hundredth the diameter of a human hair and one-fifth the thickness of a sheet of paper, he added.

The tape, with 40 million cylinder fibers per square centimeter, was created by melting plastic onto a mold with etched holes, said Carmel Majidi, postdoctoral fellow at Princeton University.

Even though the material is constructed from hard plastics, the long, thin structure of each fiber allows the fibers to bend more easily.

"We choose the material and geometry that prevents fibers from sticking to each other," Fearing said. "The geometry (of the fiber) needs to capture the essence of principles that the real animal is using."

The tape can be removed and reattached easily, similar to how geckos actually move on top of surfaces.

"The geckos' feet will actually make contact (with the surface) and pull off twenty times a second," Fearing said.

The engineers only need to apply five pounds of force to stick the tape onto the wall. The tape can then support 200 pounds.

Additionally, the tape becomes more effective after increased use, Fearing said.

"As we have used it up to 200 times and the performance keeps improving, we haven't seen the performance decreasing," he said. "The more we use it the better it works."

Previous adhesives created by scientists either took more force to stick on surfaces or were harder to detach.

The tape works so far on smooth, clean surfaces. The engineers now plan on making the tape work effectively on rough and dirty surfaces, the natural environment of geckos in the wild.

Fearing said because the gecko tape is easy to attach and remove, it would be convenient for daily use.

"With an interested buyer, the product could be on the market in two to three years," he said.

Tags: ADHESIVE, GECKO