The capacity of some animals to climb vertical surfaces, and even hang upside down from ceilings, has inspired engineers and science fiction writers alike. Scientists unraveled how creatures such as geckos manage to apparently defy the laws of physics, and engineers have replicated it. Nevertheless, you haven't seen their work appearing at your local supermarket because production has been too difficult and expensive for widespread use. Now, however, a team think they've found an easier way to make devices that will have you climbing the walls (in a good way).
Tiny hairs are the key to small climbing animals' overcoming gravity. Geckos have ridges on their toes covered with flat extensions known as fibrils or setae that have a surface attraction to the atoms in solid objects. Weak as this attraction is, with enough setae packed onto the little lizard's disproportionately large toes they can hold up their body weight, even after death. Disengagement occurs by changing the angle at which the foot meets the wall.
Humans have a much larger mass to surface area than small reptiles, so simply covering our hands with fibrils wouldn't be enough to turn us into Spiderpeople. Nevertheless, the possibility of climbing vertical glass walls has been demonstrated, provided the pads used are about 10 times the size of a human hand.
Past efforts relied on making incredibly fine-scaled templates and filling them with liquids that form a polymer when they set. The process is slow and expensive. Other climbing pads have been made by military researchers, but their methods have not been disclosed, and if they're any cheaper to produce it's a state secret.
Dr Michael Varenberg of Georgia Institute of Technology found that pouring the same polymers onto a smooth surface, then imprinting it with a suitably shaped press after it has partially set, works better. The change might seem small, but Varenberg believes it not only improves the grip, but could transform the economics of pad production.
"Molding techniques are expensive and time-consuming processes. And there are issues with getting the gecko-like material to release from the template, which can disturb the quality of the attachment surface," Varenberg said in a statement. The method is described in ACS Applied Materials and Interfaces.
Besides making it possible for dare-devils to shock skyscraper inhabitants, the pads could have abundant applications. Robot cleaners could go where no Roomba has gone before, but production lines are probably the largest market. "With the exception of things like Teflon, it will adhere to anything. This is a clear advantage in manufacturing because we don't have to prepare the gripper for specific surfaces we want to lift,” Varenberg said. “Gecko-inspired adhesives can lift flat objects like boxes then turn around and lift curved objects like eggs and vegetables."
