IT SOUNDS like the stuff of nightmares - a robot that crawls around inside your gut, anchoring itself by biting onto the walls of your intestine.

But the researchers behind a new take on the camera-in-a-pill claim its ability to move and stop on command will give doctors greater control over the images it takes, allowing them to focus on particular areas of concern.

Existing camera capsules designed to take images of the intestine cannot be controlled externally, so they simply drift through the gut along with everything else. "It's like watching the view from a train window," says the bot's developer, Arianna Menciassi of the Sant' Anna School of Advanced Studies in Pisa, Italy. "If you see something of interest, there's no way to turn back and get a better look."

The radio-controlled crawling capsule has six legs, each with tiny hooks on the end. These help prevent the device slipping on mucus in the intestine as it moves along, but are too small to damage the soft tissues, says Menciassi. The capsule can park at any site of interest by releasing a clamp with two 5-millimetre-long jaws, each with teeth. These grab onto the gut wall tightly enough to resist the muscular pulsations trying to push the device along.

The clamp may sound painful, but Menciassi says it only pinches a small area of tissue, and the intestine has relatively few nerve endings. "All the indications are that this will be far less uncomfortable than a colonoscopy or gastroscopy, in which the intestine is inflated, causing much pain to the patient," she says (Journal of Micromechanics and Microengineering, vol 15, p 2045). So far, Menciassi's team has tested the robot's mobility in an artificial gut made of pig tissue, but they hope to begin human trials soon.

Walter Koltun, a surgeon specialising in gastrointestinal disorders at Pennsylvania State University College of Medicine in Hershey, urges that care must be taken to ensure the clamp won't perforate the bowel wall. But overall he is optimistic. "The ability to stop the camera's travel or control it would be a benefit," says Kotlun. "This device definitely complements the doctor's armoury."