A thread-shaped robot can worm through narrow spaces under the control of magnetic fields, raising hopes of its use in convoluted human organs.

Doctors use snake-like robots in procedures on the heart, but these commercially available devices are too large for more tortuous body parts. To address this gap, Xuanhe Zhao at the Massachusetts Institute of Technology in Cambridge and his colleagues created soft, thread-like robots less than 1 millimetre wide. The robots contain microscopic magnetic particles and are coated with a water-rich lubricating gel. A magnet some distance away directs the robot’s course.

The team showed that the robots can smoothly navigate through a series of closely spaced hoops. The devices can also glide through twisting passageways simulating blood vessels in a life-sized replica of the human brain.