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SFU Researchers Build Wall-Climbing ‘Gecko’ Robots

A team of researchers at SFU’s engineering science department has built a robot that is able to stick to vertical surfaces and climb up it all without the use of suction cups, glue, or any other traditional bonds.

Jeff Krahn, the project’s lead researcher and author of the paper published in Smart Materials and Science said that geckos inspired the robots they built — though the robot looks more like a tank than a lizard. The robots are able to stick to and climb vertical surfaces because of a principal known as the Van der Waals force, which is the same principle that causes a gecko’s foot to adhere to vertical surfaces.

The Van der Waals force is caused by the difference in the charges of two molecules (called a dipole) passing by each other. When these two molecules, one electron rich and the other electron poor, come close to each other they attract. In a situation with billions of molecules, this creates an adhesive force.

The biological inspiration for the robot Krahn’s team produced — a gecko’s foot — works because it is covered with millions of tiny hair-like growths called setae, and each setae is covered with tiny micron sized structures called spatulae. The molecules in each spatulae are attracted to those on whatever surface the gecko is climbing on.

This isn’t the first application of such a technology. In 2010 engineers at Stanford University created what they called “the Sticky-bot” which also used the principle of the van der Waals force to climb up walls. The robot developed by Krahn’s team used a material called polydimethylsiloxane to mimic the gecko’s spatulae. Each synthetic spatulae on the treads of the robot are only 17 microns across (slightly bigger than a blood cell) and are have a mushroom cap shape. The molecules in the treads of the gecko-tank are dipoles that have both a positive and negative side, which makes them attracted to their charged opposites on whatever surface the robot is climbing. Because of the surface area of the robot’s treads, the Van der Waals force that occurs is strong enough to keep the robot stuck to the wall.

Now that this concept has proved successful, Krahn is optimistic about the potential future uses for this technology. “If we can increase [the contact area] we should be able to increase the amount of weight the robot is able to hold,” said Krahn. “Our research is now focused on making new adhesive tracks, with new styles, and new materials. What we want is something that can climb up drywall or concrete.”

Krahn also mentioned that another team in the lab is working on a spider-like version of this robot that would be able to climb over rough surfaces like rocks.

The project has been something of a media sensation, with coverage from publications around the world including Popular Mechanics, Discovery News, and The Guardian. Krahn understands the media’s interest in the project. “It appeals to me because it’s a climbing robot. Its cool!”

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