The robot's secret is its footpads, which heat rapidly to melt plastic compounds that ooze into the nooks and crannies of a surface it wants to climb, briefly bonding to it. Rapidly cooling the footpad allows the robot to disengage and take its next step.
Until now, climbing robots have been mostly featherweight machines that scamper up flat surfaces using the tiny hairs, called setae, on their footpads to stick to walls in the same way that geckos do. What's crucial is the angle at which the hairs attach: in some directions they adhere and in others they don't, allowing them to be detached.
But the pressure-sensitive materials used to make robot setae create weak bonds that cannot support heavy robots – and they have trouble climbing rough surfaces. So Fumiya Iida and colleagues at the Swiss Federal Institute of Technology (ETH) in Zurich took a different tack.
"Our technology uses thermoplastic adhesives, which are much stronger than those used in gecko-type climbing systems." says team member Liyu Wang.
These adhesives melt at about 70 °C. Above that there is a critical temperature where it is fluid but still maintains a high degree of tackiness. The robot feet the ETH team has tested use resistors to heat the material to that threshold. When a foot needs to be freed up to make another step, electrical elements that use the thermoelectric effect kick in to cool it, allowing that foot to detach and advance.
While warmed, the adhesives become less viscous and easily flow into surface gaps, says Wang, filling them and allowing a robot to climb "complex vertical terrain". In tests, a two-footed droid weighing a little more than a kilogram carried a 7-kg weight up walls made of wood, plastic, stone and aluminium.
"We are thinking about using this to climb cliffs or other complex natural environments, which no previous climbing technologies can handle," Wang says.
Journal reference: IEEE Transactions on Robotics, doi.org/mc4
Syndicated content: Paul Marks, New Scientist