Stickybot gecko-like robot climbs vertical surfaces

Gecko’s foot ability to stick to many surfaces, including glass, has been inspiring scientists to mimic that ability in other to make dry adhesive materials and robots able to walk up various materials. A group of scientists from Stanford University are developing such a robot which is fittingly named Stickybot. They are already working on an improved version of the robot as well as a scaled up version that would allow humans to climb like geckos.

Mark Cutkosky, the lead designer of the Stickybot, a professor of mechanical engineering and co-director of the Center for Design Research, has been collaborating with scientists around the nation for the last five years to build climbing robots. After designing a robot that could conquer rough vertical surfaces such as brick walls and concrete, Cutkosky moved on to smooth surfaces such as glass and metal. He turned to the gecko for ideas.

The toe of a gecko’s foot contains hundreds of flap-like ridges called lamellae. On each ridge are millions of hairs called setae, which are 10 times thinner than a human’s. Under a microscope, you can see that each hair divides into smaller strands called spatulae, making it look like a bundle of split ends. These split ends are so tiny (a few hundred nanometers) that they interact with the molecules of the climbing surface. It differs from other adhesions because it is directional, thus suitable for climbing and fast motion.

“Other adhesives are sort of like walking around with chewing gum on your feet: You have to press it into the surface and then you have to work to pull it off. But with directional adhesion, it’s almost like you can sort of hook and unhook yourself from the surface”, Cutkosky said.

The versions they use was developed in 2009, have a two-layer system, similar to the gecko’s lamellae and setae. The “hairs” are about 20 micrometers wide and support higher loads, thus allowing Stickybot to climb surfaces such as wood paneling, painted metal and glass. The material is strong and reusable, and it doesn’t damage itself or the surface it is applied to.

The team’s new project involves scaling up the material for humans. A technology called Z-Man, which would allow humans to climb with gecko adhesive, is in the works. Cutkosky and his team are also working on a Stickybot successor which would be able to turn in the middle of a climb. Because the adhesive only sticks in one direction, turning requires rotating the foot.

Cutkosky has collaborated with scientists from Lewis & Clark College, the University of California-Berkeley, the University of Pennsylvania, Carnegie Mellon University and a robot-building company called Boston Dynamics. His project is funded by the National Science Foundation and the Defense Advanced Research Projects Agency. The research is described in a paper published online in Applied Physics Letters, “Effect of fibril shape on adhesive properties“.