Washington, Sep 13 (IANS): US scientists have developed the first untethered soft robot - a quadruped that can stand up and walk carrying weight on its back with utmost ease.

Researchers from Harvard University's school of engineering and applied sciences and the Wyss Institute for Biologically Inspired Engineering have enabled a single robot to carry on its back all the equipment it needs to operate - micro-compressors, control systems and batteries.

"Earlier versions of soft robots were all tethered. We wanted to challenge people's concept of what a robot has to look like," said Michael Tolley, a research associate from the Wyss Institute.

The system designed by Tolley and colleagues is huge, measuring more than a half a metre in length and capable of carrying as much as 3.5 kg on its back.

It is made of "composite" silicone rubber made from stiff rubber impregnated with hollow glass microspheres to reduce the robot's weight.

The robot's bottom was made from Kevlar fabric to ensure it was tough and lightweight.

"The result is a robot that can stand up to a host of extreme conditions," Tolley added.

Researchers tested the robot in snow, submerged it in water, made it walk through flames and even ran over it with the help of a car. After each experiment, it emerged unscathed.

"Though additional hurdles remain - such as increasing the speed of the robots and outfitting them with sensors - the development of an untethered soft robot is a major advance," Tolley noted.

The design was described in a paper published in the journal Soft Robotics.