American researchers have created submarines consisting of only 244 atoms that can be powered by ultraviolet light.
Developed by researchers from Rice University in the US, the submarines are equipped with minuscule tail-like propellers that rotate at more than a million rounds per minute. With each revolution of the propeller, the submarine moves forward by 18 nanometers covering about one inch every second
"These are the fastest-moving molecules ever seen in solution," said chemist James Tour, who led the team developing the nano-machines described in the latest issue of the journal Nano Letters.
Although the researchers cannot directly steer the submarines yet, they believe the devices could be used in the future for targeted drug delivery.
The submarine’s motors have been developed in cooperation with a Dutch research group. Created through a 20-step chemical synthesis process, the propellers operate similarly to a bacteria's flagellum.
Each revolution of the propeller takes four steps. First, when exposed to light, the double bond that holds the rotor to the body becomes a single bond, allowing it to rotate a quarter of a circle. As the motor seeks to return to a lower energy state, it jumps adjacent atoms for another quarter turn. The process repeats as long as the light is on.
"These motors are well-known and used for different things," said lead author of the study Victor García-López. "But we were the first ones to propose they can be used to propel nano-cars and now submersibles."
"One of the challenges was arming the motors with the appropriate fluorophores for tracking without altering the fast rotation," García-López said.
The team used a custom confocal fluorescence microscope to observe how the vehicles moved.
Tour's group has extensive experience with molecular machines. A decade ago, his lab introduced the world’s first nanocars: single-molecule cars with four wheels, axles and independent suspensions that could be ‘driven’ across a surface.