Researchers Create Molecule-sized Nanosubmarines with Motors Powered by Light

Rice University scientists have created light-driven, single-molecule submersibles, illustrated above, that contain just 244 atoms. Loic Samuel/Rice University

If you were to scan the journal Nano Letters, you'd be confronted with seemingly impenetrable article titles such as "Statistical Study on the Schottky Barrier Reduction of Tunneling Contacts to CVD Synthesized MoS2." But a recent article carries the slightly less intimidating title "Unimolecular Submersible Nanomachines. Synthesis, Actuation, and Monitoring." And its focus is something that's pretty darn cool.

The article describes a vehicle built by scientists at Rice University and North Carolina University. Imagine a submersible made up of only 244 atoms, and the whole thing measures less than 10 nanometers long. A nanometer is just one-billionth of a meter. The 10 nanometer size is the range for stuff like antibodies — even viruses are larger than that. The submersibles are so tiny, you wouldn't be able to see them even with the world's most powerful optical microscope.

"These are the fastest-moving molecules ever seen in solution," Rice chemist James Tour, whose lab developed the nanosub, said in a press release.

When this submersible's tail makes a full rotation, the device is propelled forward 18 nanometers. That's not far at all, but the tail can rotate more than one million times every minute. In 60 seconds, the unimaginably tiny submersible can travel more than 18 million nanometers, which translates to more than 1.8 centimeters (.7 inches).

The submersibles were able to move through a solution faster than Brownian motion would predict, showing that their little motors were working properly. That's particularly impressive since the molecules in the solution are about the same size as the submersibles themselves. Imagine having to push your way through a crowd of kids while maintaining a regular speed, and you get the idea.

Rice graduate student Victor Garca-Lpez holds a vial with millions of single-molecule nanosubmersibles.
Jeff Fitlow/Rice University

Shining light on the submersibles activates the motors — developed by a Dutch team — causing them to rotate in four phases. There's no method to steer the suckers yet. Still, the motors mark a breakthrough in nanotechnology.

"These motors are well-known and used for different things," said lead author and Rice graduate student Victor García-López. "But we were the first ones to propose they can be used to propel nanocars and now submersibles."

And unlike earlier nanomotors, this new model neither uses nor creates toxic chemicals while it operates. Perhaps we'll see this technology evolve into something that can be used in future medical applications.

"There's a path forward," García-López said. "This is the first step, and we've proven the concept. Now we need to explore opportunities and potential applications."

It's pretty exciting to imagine devices on this incredibly tiny scale. To build them, scientists use carefully controlled chemical reactions. So maybe the mechanic of the future won't own a garage, but a Petri dish.