ROBOTIC surgery is one thing, but sending a robot inside the body to carry out an operation quite another. It has long been a goal of some researchers to produce tiny robotic devices which are capable of travelling through the body to deliver drugs or to make repairs without the need for a single incision. That possibility has just got a bit closer.

In a presentation this week to the International Conference on Robotics and Automation in Stockholm, Daniela Rus and Shuhei Miyashita of the Massachusetts Institute of Technology described a robot they have developed that can be swallowed and used to collect dangerous objects ingested accidentally. The device is based on foldable robot technology that their team of researchers have been working on for years. The basic idea is to make robots that fold up, a bit like origami, into small structures less than a few millimetres in diameter so that they can be swallowed like tablets. Then, once inside the body, the capsules enclosing the robots dissolve, allowing the devices to unfold, reconfigure themselves and get to work.

To test their latest version, Dr Rus and Dr Miyashita designed a robot as a battery retriever. This might seem to be an odd task, but more than 3,500 people in America alone, most of them children, accidentally swallow the tiny button cells used in small electronic devices every year. Because these batteries contain a charge, they have an unpleasant tendency to burn holes in the stomach. They can be removed surgically, but it is a tricky and unpleasant procedure.

To start with, the researchers created an artificial oesophagus and stomach made out of silicone. It was closely modelled on that found in a pig and filled with simulated gastric fluid. The robot itself is made from several layers of different materials, including pig intestine, and contains a little magnet. This is folded up and encased in a 10mm x 27mm capsule of ice. Once this reaches the stomach the ice melts and the robot unfolds. It is moved and steered with the use of a magnetic field outside the body.

In their tests, the robot was able to latch onto a button battery with its own magnet. Dragging it along, the robot could then be guided towards the intestines where it would eventually be excreted through the anus. After the robot had done its work, the researchers sent in another robot loaded with medication to deliver it to the site of the battery burn to speed up healing.

The team sent their robots on dozens of missions, each time successfully extracting the offending object. They got pretty good at it too, averaging five minutes to conduct the entire process.

Since the artificial stomach was transparent on one side, the researchers were able to see the batteries and visually guide the robots. The next step will be to try this procedure in pigs. That will require help with guidance from imaging systems such as ultrasound and magnetic resonance imaging. It will be a bit more of a challenge, but Dr Rus and Dr Miyashita are determined to succeed.