Pictures, Science

Behold! The Nano-Car!

No not that Nano Car, this little guy is way cooler. A new paper published in the May 2009 issue of the oldest continuously published magazine in the United States, Scientific American, asks readers to imagine producing vehicles so small they would be about the size of a molecule and powered by engines that run on sugar. To top it off, a penny would buy a million of them.

Single-molecule nano-vehicles synthesized by researchers at Rice University in Texas measure just 4x3 nanometers and have four carbon-based buckyball wheels connected to four independently rotating axles and an organic chemical chassis.
Single-molecule nano-vehicles synthesized by researchers at Rice University in Texas measure just 4x3 nanometers and have four carbon-based buckyball wheels connected to four independently rotating axles and an organic chemical chassis.

The concept is nearly unthinkable, but it’s exactly the kind of thing occupying National Science Foundation supported researchers at Penn State and Rice universities.

For several years, Ayusman Sen, who heads Penn State’s department of chemistry, and his colleague Thomas E. Mallouk, director of the Center for Nanoscale Science at Penn State, have investigated technologies that could realize these remarkable machines whose uses might include delivering medicine to specific tissue, accomplishing surgeries or communicating with the outside world from inside the human body.

James Tour and coworkers at Rice University synthesized a molecular car with four carbon-based wheels that roll on axles made from linked carbon atoms. The nano-car's molecular wheels are 5,000 times smaller than a human cell. A powerful technique that allows viewing objects at the atomic level called scanning tunneling microscopy reveals the wheels roll perpendicular to the axles, rather than sliding about like a car on ice as the car moves back and forth on a surface.
James Tour and coworkers at Rice University synthesized a molecular car with four carbon-based wheels that roll on axles made from linked carbon atoms. The nano-car's molecular wheels are 5,000 times smaller than a human cell. A powerful technique that allows viewing objects at the atomic level called scanning tunneling microscopy reveals the wheels roll perpendicular to the axles, rather than sliding about like a car on ice as the car moves back and forth on a surface.

Though researchers consistently have improved ways to build nano-machines, the stumbling block has been finding a way to power them. Shrinking energy producers–internal combustion engines, electric motors or jet engines–below millimeter dimensions is not an easy task, but researchers may be closer to a fantastic solution.

In the 1966 movie Fantastic Voyage, scientists shrink a submarine to microscopic size and inject it into the blood stream of a brilliant scientist, who has a blood clot forming in his brain. The nano-sized surgeons then set out to remove the blood clot.

Powering nano-vehicles is a complex issue yet to be solved. Researchers know that external electric or magnetic fields could create small forces that cause the tiny machines to rotate or undergo intricate motions. But, they say, that approach would cause every nano-machine in the field to move in lock-step. Autonomous movement is preferred for uses such as microsurgery when machines need to move independently. Researchers look to biology for clues that could lead to an effective, self-directed nano-motor. Here, the tail-like structure of a Salmonella bacterium turning in a corkscrew motion and powered by stored chemical energy provides an example of how nano-machines could be autonomously powered.
Powering nano-vehicles is a complex issue yet to be solved. Researchers know that external electric or magnetic fields could create small forces that cause the tiny machines to rotate or undergo intricate motions. But, they say, that approach would cause every nano-machine in the field to move in lock-step. Autonomous movement is preferred for uses such as microsurgery when machines need to move independently. Researchers look to biology for clues that could lead to an effective, self-directed nano-motor. Here, the tail-like structure of a Salmonella bacterium turning in a corkscrew motion and powered by stored chemical energy provides an example of how nano-machines could be autonomously powered.

Today, researchers can steer nano-machines, use them to convey cargo, and guide them using electromagnetic forces or chemical interactions. All of this, they say, makes the world seen in Fantastic Voyage not so far-fetched.

I can’t wait, I want the full upgrade, photosynthetic skin, night vision, space suit skin…all of it. I want to walk on Mars, and the bottom of the ocean, all of it, go science go!

The study of bacteria offers some intriguing theories for building autonomous nano-motors. One theory involves phototaxis--particle motion driven by light in which particles move towards or away from the region of highest light intensity. Movement depends on the nature of the ions given off by a lighted particle and the charge of the particle. The phenomenon can lead to biomimetic cooperative behavior, such as one in which some particles act as "predators" and others as "prey," very much like white blood cells chasing down a bacterium. The design of "smart" autonomous nano-robots could take on similar characteristics, moving independently in a needed direction by harvesting energy from light, glucose or other abundant fuels in biological or organic systems. Here, two different particles engage in phototaxis "predator-prey" movement. Dark silver chloride particles when stimulated by UV light emit positively charged ions. These ions propel the movement of the silver chloride particles, but they also cause attraction of the lighter colored silica particles. Consequently, the "prey" particles are eventually surrounded by "predators." The silver chloride particles are shown first in a neutral state, and then they are photographed after 20 seconds of exposure to UV light and again after 85 seconds of exposure. The exposure causes them to be surrounded by silica particles that are attracted by the ions. The results cause researchers to hypothesize that nano-engines using similar technologies may not be that far away.