TrendAdvances in developing wall-climbing, ceiling-walking robot

Published 30 April 2007

There are many applications to wall-climbing, ceiling-walking robots, and a Carnegie Mellon team has made advances in developing one; the main problem to overcome: Keeping the robot’s feet clean

Talk of infusing the term “climbing up the wall” with new meaning! Researchers at the Robotics Institute at Pittsburgh, Pennsylvania-based Carnegie Mellon University (CMU) have created a robot that can run up a wall as smooth as glass and even crawl on the the ceiling at a rate of six centimeters a second. The robot uses a dry elastomer adhesive to achieve this feat, but the research group is testing a new geckolike ultrasticky fiber on the robot’s feet that should make it up to five times stickier. The CMU robot is not the first one to use fiberlike dry adhesives to stick to surfaces, but this robot has a greater sticking power thanks to fibers that are twice as adhesive as those used by geckos.

There are several applications for such robots, among them, inspection of the hulls of spacecraft for damage, stealthy surveillance and observation of facilities in the event of terrorist or hostage situations, and more.

Technology Review Dauncan Graham-Rowe reports that the key features of the new robot is that it can turn very sharply and that it can transfer from floor to wall and wall to ceiling with great ease. “It is very compact and has great maneuverability,” says Mark Cutkosky, a professor of mechanical engineering and codirector of the Center for Design Research at Stanford University. “It is a practical solution for climbing.”

Geckos stick to surfaces owing to to very fine hair-like structures on their feet called setae. These angled fibers split into even finer fibers toward their tips, thus giving the gecko’s foot a spatula-like appearance. These end fibers have very weak intermolecular forces, thus allowing for attractive forces to act between the fiber tips and the surface they are sticking to.

The interest in wall-climbing robots has led several research groups to fabricate fiber structures designed to emulate setae. The CMU group has improved upon the gecko’s design by using microfabrication techniques. Specifically, the CMU team created fibers just four micrometers in diameter —two orders of magnitude smaller than those used in any other robots. The reduction in size allows the fibers to increase their surface contact and hence enhances adhesion.

There are still problems to be resolved, key among them the question of dirt. Andre Geim, a professor of condensed-matter physics at the University of Manchester, says that “No one has yet explained why geckos can first run on a dirt road picking up dust and then somehow climb up walls…. This is a major obstacle.” Mark Cutkosky, a professor of mechanical engineering and codirector of the Center for Design Research at Stanford University, agrees. “The world is dirty, and robots cannot be stopping to wash their feet every few meters,” he says.