May 9, 2008 -- Some people customize cars by adding fuel injection systems and extra strong alloys. Now scientists in Arizona have customized nanoengines by spiking the gas with rocket fuel and adding carbon nanotubes to strengthen the motor's micro-sized frame.
The new additions revved up the tiny motors to 20 times faster than existing nanomotors.
A nanomachine is a tiny device that is less than a micron (one millionth of a meter) in size that scientists hope to use in a variety of medical and research applications.
The Arizona team's powerful nanomotors could one day deliver disease-fighting drugs inside the body to invading pathogens or tumor cells or help clean up environmental toxins by using them as fuel.
"This is the first example of a powerful, man-made nanomotor," said Joseph Wang, director of the Biodesign Institute at Arizona State University and a coauthor on the study to appear in the May 27 issue of the American Chemical Society Nano.
The heart of this synthetic nanomotor is a tiny rod, tipped with gold on one end and platinum on the other, that has been around for years.
When the gold or platinum encounters the fuel, hydrogen peroxide (H2O2) or hydrazine (H2N4), the metal breaks up the fuels' molecules, releasing water and oxygen in what one researcher, Vincent Crespi, describes as a "little jet of water."
Crespi is a researcher at Penn State University who works on similar gold-platinum-based nanomotors but was not involved in the most recent article.
The key to speed, according to Wang, is the tiny electron that gets peeled off during the reaction and powers the reaction between the fuel and the gold-platinum rod.
Hydrogen peroxide is the same chemical that bleaches hair. Hydrazine is used as rocket fuel.
To the existing gold-platinum rod, the scientists in Arizona added carbon nanotubes, which had never been done before.
Carbon nanotubes are tiny tubes, only a few atoms thick, made up entirely of carbon atoms. The atoms are linked extremely tightly together to create a material that conducts electricity and heat. They have a huge range of uses that seems to grow by the day, from helping repair bones to solar panels.
When hydrogen peroxide (the fuel) was added, the tiny motors topped out at 60 micrometers per second, six times faster than the previous record.
Next, Wang and his colleagues spiked the engine's fuel with hydrazine. The motors shifted into fifth gear and sped away at nearly 200 micrometers per second.
There is still some speculation about the exact reason why the nanomotors speed up so much, but Wang suspects that the carbon nanotubes sped up the electron in gold-platinum rod, allowing for more reactions to take place.
The fact that the researchers used rocket fuel is coincidental. Other teams have created biobased nanomotors that use simple sugar as fuel to carry very small objects.
Whatever the fuel, it just has to be found in the nanomotors immediate environment. Unlike a traditional automobile that carries its fuel with it, nanomotors are too small for a fuel tank and have to use whatever they can find.
"It's kind of like a battery that chases its nose," said Crespi.
The same way a bigger automobile is faster and more powerful than a compact car, faster, more powerful nanomotors could carry big, heavy drugs or biological markers directly to a site in the body faster than anything today.
Although any real-world applications are still years away, Wang and his fellow researchers are trying to adapt the powerful nanomotors for use inside the body and for environmental remediation.
If a hazardous chemical is released into the environment, nanomotors could use them as fuel to power themselves. As they move through the contaminate they spit harmless chemicals out of their nanotailpipes.
In the body, drugs work by passively diffusing through the body until they literally run into their target, whether that target is a tumor or a invading pathogen.
Pathogens and tumors both release chemicals that nanomotors could use as fuel. Once the injected nanomotors detect that fuel they would activate, swimming directly to the source and delivering their cargo.
"There are a wide range of applications for these nanomotors," said Wang.
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