Tiny "Nanoswimmer" Robots Could Clean Chemical Spills, Purify Water, or Deliver Drugs

Researchers at the University of Colorado Boulder have detailed tiny "nanoswimmer" robots that, they say, could help clean up the environment and even deliver drugs where they're needed — thanks to their efficiency at escaping mazes.

"This is the discovery of an entirely new phenomenon," claims senior author Daniel Schwartz, Glenn L. Murphy Endowed Professor at CU Boulder, "that points to a broad potential range of applications."

The concept behind the nanoswimmers isn't new. Also known as Janus particles, the tiny robots were first documented 20 years ago — but their small size means it's been difficult to observe or model their movement.

Unlike a mechanical robot, the nanoswimmers rely on self-propulsion: One half of the nanoswimmer promotes a chemical reaction, while the other stays inert; the chemical field thus produced lets the particle pull energy from the environment to propel itself along.

"In biology and living organisms, cell propulsion is the dominant mechanism that causes motion to occur, and yet, in engineered applications, it’s rarely used," Schwartz explains. "Our work suggests that there is a lot we can do with self-propulsion."

To test the concept, the researchers placed the nanoswimmers into a maze made of a porous medium. Compared to purely passive particles, the nanoswimmers escaped the maze as much as 20 times faster compared to particles moving passively through Brownian motion.

"We know we have a lot of applications for nanorobots, especially in very confined environments, but we didn’t really know how they move and what the advantages are compared to traditional Brownian particles. That's why we started a comparison between these two," adds Haichao Wu, lead author of the paper.

"And we found that nanoswimmers are able to use a totally different way to search around these maze environments."

The team is hopeful that the work can lead to a range of use cases for the nanoswimmers, including using them to clean up chemical spills in soil, purify contaminated water, and even deliver drugs exactly where they're needed in the body.

The work has been published under closed-access terms in the journal PNAS.