PARIS, March 11: Robots of the future may be able to climb up and down walls and zigzag across ceilings — and the cockroach will be the one we should thank.

One of the most reviled species in the book of life, the cockroach is also one of the most successful. Its design, honed by 300 million years of evolution, enables it to exploit a huge range of habitat niches, and its locomotion is notoriously fast and versatile.

In a study published on Wednesday, University of Cambridge zoologists Walter Federle and Christofer Clemente say they can explain how the roach (Nauphoeta cinerea) is able to effortlessly perform gravity-defying tricks.

Two tiny pads on the insect’s feet are able to pull or push, enabling the critter to skip around on surfaces that are vertical or upside-down, they found.

Previous research has found that the cockroach’s pads are soft and cushion-like and covered with a very thin film of oily and watery liquid, the exact composition of which remains unclear.

The film acts in the same way as a droplet of water between two glass plates, making them stick firmly together through surface tension.

The cockroach conundrum is this: pads typically stick when pulled towards the body but they detach when they are pushed.

Yet moving vertically up and down requires not only pulling but also pushing.

Without these two abilities, the insect would slip.

Federle and Clemente found the secret by amputating legs from adult cockroaches, freeze-drying the limbs and examining the pads — just half a millimetre (0.019 of an inch) across — under a powerful electron microscope.

They then taped live cockroaches to a mount and tested the movement and force of their legs and finally used a high-speed camera to record the insects going through their paces, zipping up and down the walls of a glass tube.

The pads essentially comprise a “toe”, a front part called an arolium, which is used for pulling, and a “heel,” or back part, called an euplantula, which is used for pushing, they found.

The clever cockroaches use combinations of arolia and euplantulae on different feet of their six legs to compensate for the shifting forces exerted on them.

For instance, a cockroach that climbs upwards uses arolia on its front legs and euplantulae on its rear legs. But when it climbs downwards, its front legs use the euplantulae and the hind legs use the arolia.

And it can swiftly switch direction thanks to a single muscle in its claw flexor, which is relaxed during push strides and contracted during pull strides.

Thanks to this turn-on-a-dime ability, the roach can laugh as you try to swipe it with a dish towel.

In an interview, Federle said the findings could be useful for robot engineers inspired by other creatures in nature that have adhesive feet, such as the spider and the gecko.

Current bio-robots are able to climb upwards but hit big problems when it comes to climbing down.

They cannot climb downwards head-first — they have to have the same head orientation for going up or down, because their feet are designed mainly for pulling and not for pushing.

“An insect-inspired robot foot that can generate both pushing and pulling forces might help to achieve better manoeuverability,” said Federle.

The study appears in Proceedings of the Royal Society B, a journal published by Britain’s de-facto academy of sciences.—AFP