Over the years, scientists have come up with all manner of new ways to deliver medication, from sophisticated dual-sided pills to drug-packed nanoparticles. Now, researchers at Drexel University in Philadelphia are working on something even more sophisticated, developing tiny bead-shaped robots controlled by magnetic fields.

It sounds like something from a sci-fi movie – tiny robots swimming through the body and delivering medication exactly where it's needed most – but it's actually something scientists around the world have been working to make a reality. We've seen the concept in the past, in a Max Planck Institute study using scallop-like robots, and in a University of California, San Diego project, which made use of magnetically propelled helical microswimmers.

The Drexel University project is built upon the same idea, using a magnetic field to propel a tiny intravenous robot swim team to deliver medicine inside the body. Today, the researchers announced that they've made significant strides towards making it a reality.

Unlike other microswimmers, the Drexel team's robots are bead-shaped. The tiny robots are magnetically linked together, and the researchers use external rotating magnetic fields to spin chains of them, creating a screw-like propeller that pushes them forward. According to the team, using magnetic fields for propulsion inside the body is a good fit, as they can journey over long distances with minimal effects on patient health.

The team tried out different lengths of chain, and found that longer groups of beads can swim faster than shorter ones. The longest chain studied consisted of 13 beads, and reached a speed of 17.85 microns/second.

The spinning motion of the swimmers is key to their ability to decouple when required, with certain rates of rotation causing groups to split off and start moving independently. It's also possible to reconnect two chains by tweaking the magnetic field, bringing the beads back into contact with one another.

The Drexel research demonstrates that the versatility of bead-like robots could make them a good fit for intravenous drug delivery or for clearing clogged arteries. It's an important part of the puzzle, but there's still plenty more work to be done, not least to demonstrate such systems can actually wiggle their way to the desired location inside the body.

"For applications of drug delivery and minimally invasive surgery, future work remains to demonstrate the different assembled configurations can achieve navigation through various in vivo environments, and can be constructed to accomplish different tasks during operative procedures," stated the authors of the study.

The team published full details of its work in the journal Scientific Reports. To see the tiny robots in action, you can check out the video below.

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