A collaboration between ESA and the Simon Fraser University in Canada has led to the construction of a small robot that can walk on vertical surfaces or ceilings holding onto them like a gecko lizard. This prototype with six legs, called Abigaille, has the aim to develop robots capable of performing maintenance operations even in space.
Geckos legs have been the subject of several studies because they allow these animals to adhere to many types of surfaces without the use of adhesive secretions. The research showed that geckos can remain attached to the surfaces thanks to the van der Waals force between the ends of the tiny hairs called setae in the lower part of their legs that causes an interaction of attractive type at the atomic level with the surfaces.
Replicating that kind of interaction can be very useful because all other types of adhesive have some defect. The various types of tape become less and less effective over time because they collect dust, even in space, reducing their stickiness and in the void they tend to emit fumes that could damage some delicate instrument. Velcro requires a mating surface to hook to and it could wear out over time. Magnets only work on certain types of surfaces and can create problems near sensitive instruments.
Creating a robot equipped with legs that have sticky ends like those of geckos wasn’t easy and required the use of techniques derived from microelectronics industry. The extremities are still about a hundred times larger than geckos hairs but are small enough to generate enough interaction to support the weight of Abigaille. This robot is very light anyway, weighing only about 240 g.
At ESA’s European Space and Technology Centre in Noordwijk, Netherlands, the robot Abigaille was put to the test in a laboratory in which they replicated vacuum and temperatures conditions of space. A special instrument measured the robot’s stickiness to the surfaces and the results were positive. In space, in microgravity conditions, a robot of this type should work even better.
The robot Abigaille was also built to be dexterous. All its six legs have four degrees of freedom and this allows it to move from a vertical to a horizontal surface and vice versa. A robot on wheels couldn’t make those kind of maneuvers therefore couldn’t work that way on a satellite or a spacecraft.
This prototype has a speed closer to that of a snail than to that of a gecko. Another limitation is that it can walk vertically limited to artificial surfaces that are rather smooth. It will probably take years before more advanced versions get actually used but it’s only a matter of time.
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