Research team develops new nanomotors

In a “major step” toward a practical energy source for powering tomorrow’s nanomachines, researchers at ASU’s Biodesign Institute report the development of a new generation of tiny nanomotors that are up to 10 times more powerful than existing motors.

Just like weekend hot-rodders who tinker with their car engines in the ultimate quest for speed, a research team led by Joseph Wang, who directs the institute’s Center for Biosensors and Bioelectronics, set out to improve on the design of current nanomotors. These so-called “catalytic nanomotors” are made with gold and platinum nanowires and use hydrogen peroxide (the same chemical that bleaches hair) as a fuel for self-propulsion.

But these motors are too slow and inefficient for practical use, with top speeds of about 10 micrometers per second, the researchers say. One micrometer is about a 25,000th of an inch across, or almost 100 times smaller than the width of a human hair. (If one could somehow magnify the nanoworld to human scale by multiplying by a factor of 100,000, the speed would be the seem the same as a walking speed of 3.6 miles per hour.)

Wang and colleagues supercharged their nanomotors by inserting carbon nanotubes into the platinum, thus boosting average speed to 60 micrometers per second. This was the first time that carbon nanotubes had been added to the existing gold and platinum nanowires. The tiny tubes, only a few atoms thick, help conduct electricity and heat.

“This is the first example of a powerful, man-made nanomotor,” says Wang, who is an ASU professor with a joint appointment in the departments of chemical and material engineering in the Ira A. Fulton School of Engineering, and chemistry and biochemistry in the College of Liberal Arts and Sciences.

Spiking the hydrogen peroxide fuel with hydrazine (a type of rocket fuel) kicked up the speed still further, to 94-200 micrometers per second (using the same multiplying factor of 100,000, the top speed would now be equal to a moped-like speed of 43.2 miles per hour). This innovation “offers great promise for self-powered nanoscale transport and delivery systems,” Wang says.

Authors on the paper include: Rawiwan Laocharoensuk, Jared Burdick, and Joseph Wang. Their study appeared in the May 27 issue of ACS Nano, a monthly journal. They also reported their findings in the online edition of ACS Nano.