Doctors have long sought better ways to examine the workings of the human body without having to cut patients open. A swallowable camera, little bigger than a normal pill, can already snap pictures as it floats through the stomach and intestine, offering a less invasive way to diagnose ailments than would an endoscope or surgery. A consortium of European researchers is now testing a way to connect several swallowable devices to create a surgical "robot" that would self-assemble inside the stomach.

The Israeli company, Given Imaging that developed the first pill cameras, is working on a way to control the movement of its camera capsule from outside the body. Several academic research groups also are looking at ways to let swallowable capsules maneuver themselves by rolling, crawling, or sticking to tissue.

A collaboration of researchers from Italy, France, Switzerland and Spain, called ARES, is testing a way for multiple capsules to automatically snap together. Each would be swallowed individually before assembling into a more complex device once in the stomach.

The goal is for each capsule to perform a different task, such as imaging, power, and taking samples. Once inside the stomach, the capsules would link together, creating a snake-like device that could slide through the intestines, performing more complex tasks than those possible by a single capsule or several free-floating ones.

The Swiss Federal Institute of Technology (ETH) decided to use magnets to connect its modules because they don't require onboard power and are easily monitored outside the body. The researchers tested different designs in a plastic stomach models filled with liquid. A single magnet with its positive-negative axis on the surface of a longer capsule worked best, yielding a 75% success rate at linking the two capsules. The success rate jumped to 90% after making the magnet module more flexible. The ETH team detected how well modules linked together by monitoring changes to the field of each magnet.

The next research stage involves making sure the magnets do not harm tissue when they lock together. The system will be tested in a moving artificial or animal stomach. The team must also find a way to control how the capsules arrange themselves.

In the accompanying photo, researchers at the Swiss Federal Institute of Technology used a plastic stomach to see which magnetic design links best in a small fluid-filled space.