Scientists in Switzerland have created a robot the size of a grain of sand that is controlled by magnets and can deliver drugs to a precise location in the human body, a breakthrough aimed at reducing the severe side effects that stop many medicines from advancing in clinical trials.

“We’re just at the tip of the iceberg,” said Bradley J. Nelson, an author of the paper in Science describing the discovery and a professor of robotics and intelligent systems at ETH Zurich. “I think surgeons are going to look at this. I’m sure they’re going to have a lot of ideas on how to use” the microrobot.

The capsules have been tested successfully in pigs, which have similar vasculature to humans, and in silicone models of the blood vessels in humans and animals. The silicone models are used in medical training.

Nelson said drug-ferrying microrobots of this kind may be three to five years from being tested in clinical trials.

The problem faced by many drugs under development is that they spread throughout the body instead of going only to the area in need. When we take aspirin for a headache, for example, it is absorbed into the bloodstream and circulates throughout the body.

A major cause of side effects in patients is medications traveling to parts of the body that don’t need them.

The capsules developed in Switzerland, however, can be maneuvered into precise locations by a surgeon using a tool not that different from a PlayStation controller. The navigation system involves six electromagnetic coils positioned around the patient, each about 8 to 10 inches in diameter.

The coils create a magnetic field and can be used to push the capsule in one direction or pull it in the opposite direction.

“By combining these fields and controlling them individually, you can get the precise kind of motion you want to move through the blood vessels or the cerebrospinal fluid,” Nelson said.

The magnetic field is strong enough to move the capsule even when it is traveling against the flow of blood.

The capsules are made of materials that have been found safe for people in other medical tools. These include tantalum, a dense silvery metal used for contrast so that doctors can see the capsule on X-rays, and tiny particles made of iron and oxygen that have magnetic properties. The latter, known as iron oxide nanoparticles, were developed for the capsules by a team at ETH Zurich led by chemist Salvador Pané.

The nanoparticles, tantalum and the medication itself are all bound together in a structure created using the protein gelatin.

Although the capsule moves rapidly in the body, doctors can track how it is progressing through blood vessels via X-ray. When the capsule reaches its destination in the body, “we can trigger the capsule to dissolve,” Nelson said.

The paper in Science generated excitement in the robotics field.

“I try not to overhype things, but this work ― in terms of being able to deliver high-precision care ― out of all the research I’ve seen, it is by far the most exciting,” said Howie Choset, a professor of robotics and biomedical engineering at Carnegie Mellon University. Choset, who has worked in the robotics field for more than 30 years, was not involved in the study.

Biomedical applications have been one of the most coveted applications in robotics but also one of the most challenging, said Marc Miskin, an assistant professor of electrical and systems engineering at the University of Pennsylvania. He did not participate in the study.

“Robotics is hard to begin with,” Miskin said. “Biomedical engineering is hard, and nanofabrication and nanoscience are hard, and this is a problem that basically sits at the interface of all of these.”

Miskin predicted the paper will be a landmark.

“This is going to be a big step forward,” he said. “Actually showing a technology that looks like a clinically ready technology, that’s going to change the way people think about it.”