ERJ staff report (PR)
Arlington, Virginia – A climber weighing 218 pounds (99 kilos) and carrying a 50-pound load has successfully scaled up and down 25 feet (7.5 metres) of glass aided only by a pair of hand-held, gecko-inspired elastomeric paddles, the US Defense Advanced Research Projects Agency (DAPRA) has announced.
The pioneering feat was staged under DARPA’s Z-Man programme to demonstrate a novel polymer microstructure technology used in those paddles and was developed for DARPA by Draper Laboratory of Cambridge, Massachusetts.
The gecko-inspired programme aims to overcome the limitations of conventional climbing gear and deliver maximum safety and flexibility for manoeuvring to military personnel operating in tight urban environments.
“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 manoeuvre challenges that US forces face in urban environments,” said Dr. Matt Goodman, the DARPA program manager for Z-Man.
“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.”
Geckos can climb on a wide variety of surfaces, including smooth surfaces like glass, with adhesive pressures of 15-30 pounds per square inch for each limb, meaning that a gecko can hang its entire body by one toe.
The anatomy of a gecko toe consists of a microscopic hierarchical structure composed of stalk-like setae (100 microns in length, 2 microns in radius). From individual setae, a bundle of hundreds of terminal tips called spatulae (approximately 200 nanometres in diameter at their widest) branch out and contact the climbing surface.
A gecko is able to climb on glass by using physical bond interactions – specifically van der Waals intermolecular forces – between the spatulae and a surface to adhere reversibly, resulting in easy attachment and removal of the gecko’s toes from the surface. This implied that it is the size and shape of the spatulae tips that affect adhesive performance, not specific surface chemistry.
The Draper Laboratory team created novel micro- and nanofabrication technologies to produce climbing paddles capable of balancing sufficient adhesive forces both parallel and perpendicular to the vertical surfaces. Climbers can, thereby, remain adhered on a surface without falling off while attaching and detaching the paddles with each movement.