June 6, 2014
Humans Can Climb Like Geckos Thanks To DARPA’s Z-Man Program
Gerard LeBlond for redOrbit.com - Your Universe Online
The gecko is a small lizard that can climb on a variety of surfaces, including glass. It uses adhesive pressure equaling 15 to 30 pounds per square inch (PSI) on each limb. Theoretically, the gecko can also support its body weight hanging on one toe. Each toe is comprised of a microscopic hierarchical structure which are little stalk-like extensions 100 microns long and 2 microns around. Each stalk is a bundle of hundreds of tips called spatulae approximately 200 nanometers in diameter, which are used for climbing on any surface. There are also intermolecular forces between the spatulae which allow the gecko to attach and remove its toes easily.
The Z-Man program recently demonstrated a 218-pound person ascending and descending 25 feet of glass carrying an additional 50 pounds with only the gecko-inspired paddles.
Draper Laboratory of Cambridge, Mass. developed the polymer microstructure for the paddles. By studying the gecko’s toe anatomy and its ability to climb on a variety of surfaces (van der Waals intermolecular forces), scientists were able to design and fabricate the adhesive aspect of the paddles. Van der Waals mechanism suggested that the size and shape of the spatulae tips is what allows the gecko to adhere to surfaces, not the chemistry makeup.
This technology was developed mainly for use by war fighters to gain an advantage in urban environments. Previously, ladders, ropes and other climbing equipment was used, which was labor intensive and the first climber was at the greatest risk. With this new system, climbers can now carry a full combat load and ascend vertical walls constructed of typical building materials, including glass.
“The gecko is one of the champion climbers in the Animal Kingdom, so it was natural for DARPA to look to it for inspiration in overcoming some of the maneuver challenges that U.S. forces face in urban environments. Like many of the capabilities that the Department of Defense pursues, we saw with vertical climbing that nature had long since evolved the means to efficiently achieve it. The challenge to our performer team was to understand the biology and physics in play when geckos climb and then reverse-engineer those dynamics into an artificial system for use by humans,” said Dr. Matt Goodman, the DARPA program manager for Z-Man.
The typical gecko weighs about 7 ounces, but the average human male weighs about 165 pounds, so the challenge was to develop the climbing paddles to be able to support the total weight of the person and gear while climbing. The climber needs to remain adhered to the surface while attaching and detaching the paddles.
Image 2 (below): During testing, an operator climbed 25 feet vertically on a glass surface using no climbing equipment other than a pair of hand-held, gecko-inspired paddles. The climber wore, but did not require, the use of a safety belay. Credit: DARPA