When it comes to deciding on a form of locomotion for their creations, roboticists have plenty of options to choose from. While many go for the tried and tested tank-like tracks or wheels, nature is also a veritable treasure trove of inspiration. That's just where Fraunhofer researchers have turned with a new eight-legged robot modeled on the same principle that moves spider legs. Not only does the design give the spiderbot the agility and stability of real spiders when getting around on the ground, it also features special joints that allow it to jump.

Like its biological brethren, the spiderbot is extremely stable, keeping four of its legs on the ground at any one time while the remaining four legs turn and ready themselves for the next step. Diagonally opposed members can also move simultaneously and bending the front pairs of legs pulls the spiderbot's body along, while stretching the rear legs pushes it.

As real spiders don't have extensor muscles at each of its leg joints, they rely on a sudden change in blood pressure in addition to the extensor muscles found on some joints to force the legs to extend rapidly and provide the full extension of the legs required for jumping. Borrowing this design, the researchers fitted the spiderbot's eight 20 cm (8 inch)-long legs and its body with pneumatically operated elastic drive bellows that bend and extend its legs with the force required to get it to jump.

The control unit, valves and compressor pump that provide the means of locomotion are located in the robot's body, which can also be fitted with various measuring devices and sensors, depending on the job at hand.

Instead of producing the robot using conventional mechanical-engineering technologies, the Fraunhofer team turned to a 3D printing process called selective laser sintering (SLS) that sees thin layers of a polyamide powder applied one at a time and melted into place using a laser. Not only does this process allow complex geometries and inner structures to be produced, but the resulting robot is also very lightweight and cheap to produce.

"We can use SLS to produce one or even several legs in a single operation; this minimizes assembly effort, saves materials and reduces the time it takes to build a robot. With the modular approach, individual parts can be quickly swapped as well. Our robot is so cheap to produce that it can be discarded after being used just once - like a disposable rubber glove," says Ralf Becker, a scientist at the Fraunhofer Institute for Manufacturing Engineering and Automation (IPA).

Although the spiderbot is still just a prototype, the researchers envision it could be used to explore environments that are hazardous or too difficult to access for humans, such as natural disaster areas and industrial or reactor accident sites. It could also be used to assist first responders and fire departments by broadcasting live images or tracking down hazards or leaking gas.

The Fraunhofer team will be displaying a prototype of the robot at the EuroMold 2011 trade fair that runs from November 29 to December 2 in Frankfurt.3