ROBOTS that can climb walls have been developed by scientists in the United States. The robots can scale surfaces using the same principles behind electrostatic charges, which make balloons stick to ceilings after being rubbed. Developed by a team in SRI's Mobile Robotics and Transducers Programme, the machines are about the size of a remote-controlled car and have caterpillar tracks similar to those on toy tanks. Inside these tracks are materials with electro-adhesive properties, which mean that when a current is applied, the tracks are attracted to the wall, preventing the robots from falling off. "What we've invented is a way to induce charges on the wall using a power supply located on the robot," research engineer Harsha Prahlad told BBC World Service's Digital Planet programme. "The robot carries with it positive and negative charges, and when the walls sees these charges it automatically generates the opposite charge. The robot can then clamp onto those charges. "In some ways it is similar to rubbing a balloon and sticking it on the wall, except we carry our own power supply and are able to control the adhesion." The technology, called compliant electroadhesion, uses a very small amount of power and the robots can crawl at a speed of about one body length per second.  The robots are being touted for use by the military, for reconnaissance, for service applications and as toys. "It is very similar to how a toy tank works, with the two treads," Prahlad explained. "There are positive and negative traces attached to the treads. "We simply drive it, moving it like a conveyer belt." The team is now working on a way to apply their technology to more insect-like robots, to mirror the way that creatures such as flies are able to walk upside-down. This will be done by putting electro-adhesive pads on the robot feet.  "We often think of electrostatic forces as very weak - but if you get very close, you can get very strong forces from this," Mr Prahlad added.                                   - BBC