In the future, tiny robots of all kinds of shapes could be swimming and crawling through your body, delivering drugs or patching up wounds. The next robot to join those ranks is a caterpillar-inspired device, which gets around with ease on hundreds of tiny, pointy legs.

Developed by researchers from City University of Hong Kong, the new robot measures 17 mm long, 7 mm wide and stands about 1 mm tall (0.7 x 0.3 x 0.03 in). More than half of that height is taken up by its hundreds of cone-shaped legs, giving it the appearance of a caterpillar or millipede.

The robot is made of a soft silicon material full of embedded magnetic particles. Applying a magnetic force in just the right way lets it move, either in a flap propulsion pattern – where its front section raises up and drags its body forwards – or in an inverted pendulum pattern, where it alternates between tilting up onto its left and right legs, rocking itself forwards.

This design has several advantages. With each of its legs ending in a tiny point, the robot has relatively little surface contact, reducing friction by about 40 times that of limbless machines like the crawling "milli-robot" we saw early this year. That lets it move efficiently across surfaces lined with body fluids like blood or mucus, or even while fully submersed.

"Both the materials and the multi-leg design greatly improve the robot's hydrophobic property," says Wang Zuankai, an author of the study. "Besides, the rubbery piece is soft and can be cut easily to form robots of various shapes and sizes for different applications."

In tests, the robot was also able to climb over obstacles much taller than itself, by lifting its front end up to a 90-degree angle and pulling itself up. That could come in handy for traversing the uneven terrain inside the human body. Along with its skills in getting around, the robot looks like it will be able to carry heavy loads. It was found in tests to be capable of lifting 100 times its own weight.

"The amazingly strong carrying capability, efficient locomotion and good obstacle-crossing ability make this milli-robot extremely suitable for applications in a harsh environment, for example delivering a drug to a designated spot through the digestive system, or carrying out medical inspection," says Shen Yajing, lead researcher on the study.

The researchers plan to keep tinkering with the robot to see what else they can get it to do, what other shapes might work and whether it can be made of materials that naturally biodegrade after its job is done.

The research was published in the journal Nature Communications.