Motorized Nanocars, Nanogenerators, and Nanomedical Advances

WASHINGTON, DC, April 17, 2006 (ENS) - Cars made of a single molecule now are motorized, and mechanical energy from body movement is being harnessed to generate electricity and eventually, power implantable medical devices. These are just two of the nanotechnology breakthroughs announced in the past seven days.

Nanotechnology is the science of creating or modifying materials at the atomic and molecular level to develop new or enhanced materials and products. The breakthroughs are based on work with nanometers - each one billionth of a meter in size - about one ten-thousandth the diameter of a human hair, or a thousand times smaller than a red blood cell.

At Rice University in Houston, Texas, chemists who last year invented the world's first single-molecule car have now produced the first motorized version of their tiny nanocar. The research is published in the April 13 issue of the journal "Organic Letters."

"We want to construct things from the bottom up, one molecule at a time, in much the same way that biological cells use enzymes to assemble proteins and other supermolecules," said lead researcher James Tour, the Chao Professor of Chemistry, professor of mechanical engineering and materials science and professor of computer science. nanocar

The nanocar's light-powered motor is attached mid-chassis. When struck by light, it rotates in one direction, pushing the car along like a paddlewheel. (Photo by Takashi Sasaki courtesy Rice U.)
The nanocar consists of a rigid chassis and four alkyne axles that spin freely and swivel independently of one another. The motorized model of the nanocar is powered by light.

Its rotating motor, a molecular framework that was developed by Ben Feringa at the University of Groningen in the Netherlands, was modified by Tour's group so that it would attach in-line with the nanocar's chassis. When light strikes the motor, it rotates in one direction, pushing the car along like a paddlewheel.

The nanocars, which measure just 3-by-4 nanometers, are about the same width as a strand of DNA, but much shorter than DNA. About 20,000 of these nanocars could be parked, side-by-side, across the diameter of human hair. They are the first nanoscale vehicles with an internal motor.

The nanocar research was funded by the National Science Foundation, the Welch Foundation, Honda, the Natural Sciences and Engineering Research Council of Canada, and Le Fonds Québécois de la Recherche sur la Nature et les Technologies.

A different nanotech advance has emerged this week from the Georgia Institute of Technology (GIT). Researchers there have developed a new technique for powering nano-scale devices without the need for bulky energy sources such as batteries - tiny nanowires that generate electricity when they vibrate.

By converting mechanical energy from body movement, muscle stretching or water flow into electricity, these "nanogenerators" could make possible a new class of self-powered implantable medical devices, sensors and portable electronics.

"There is a lot of mechanical energy available in our environment," said Zhong Lin Wang, a Regents Professor in the GIT School of Materials Science and Engineering. "Our nanogenerators can convert this mechanical energy to electrical energy. This could potentially open up a lot of possibilities for the future of nanotechnology."

Described in the April 14th issue of the journal "Science," the nanogenerators produce electric current by bending and then releasing zinc oxide nanowires – which are both piezoelectric and semiconducting.

The nanogenerators could also be used wherever mechanical energy – such as the hydraulic motion of seawater, wind or the motion of a foot inside a shoe – is available. The nanowires can be grown not only on crystal substrates, but also on polymer-based films. Use of flexible polymer substrates could one day allow portable devices to be powered by the movement of their users.

nanowires

A scanning electron microscope image (top) shows an array of zinc oxide nanowires. Middle image shows a schematic of how an AFM tip was used to bend nanowires to produce current. Bottom image depicts output voltages produced by the array as it is scanned by the probe. (Photo courtesy Zhong Lin Wang)
"You could envision having these nanogenerators in your shoes to produce electricity as you walk. This could be beneficial to soldiers in the field, who now depend on batteries to power their electrical equipment. As long as the soldiers were moving, they could generate electricity," said Wang, who also holds affiliated faculty positions at Peking University and the National Center for Nanoscience and Technology of China.

"Our bodies are good at converting chemical energy from glucose into the mechanical energy of our muscles," Wang explained. "These nanogenerators can take that mechanical energy and convert it to electrical energy for powering devices inside the body. This could open up tremendous possibilities for self-powered implantable medical devices."

The research was sponsored by the National Science Foundation, the NASA Vehicle Systems Program and the Defense Advanced Research Projects Agency.

Also on the nano-medical front, in Australia, Professor Mark Kendall at the University of Queensland (UQ) has received funding to research how nanotechnology may replace syringes in administering medications. His work could eventually replace needles with tiny nano-patches on the skin.

"There is an explosion of designer drugs requiring precise delivery to specific locations in the skin and we are producing new delivery methods that are practical and needle-free," Kendall said Saturday.

"We are targeting immunologically sensitive cells to produce improved immune responses in the treatment of major diseases such as HIV, malaria and allergies," said Kendall. "This has enormous potential, including for the delivery of cheap and more effective vaccinations in the developing world."

Professor Kendall is a UQ graduate who recently returned from the University of Oxford, where he achieved commercial success with a bioballistic gene gun. He was the associate director of the PowderJect Centre for Gene and Drug Delivery at Oxford. He is jointly appointed to UQ's Australian Institute for Bioengineering and Nanotechnology, Centre for Immunology and Cancer Research, and Faculty of Health Sciences.

His work on needle-free drug delivery last week won a three year Queensland Government Smart State Senior Fellowship.

Back in the United States, researchers at University of California-Berkeley, have found a way to use the electric-field process to make nanofibers in a direct, continuous and controllable manner. Their study is in the April issue of the journal "Nano Letters."

The new technique, known as near-field electrospinning, offers the possibility of producing out of nanofibers new, specialized materials with organized patterns that can be used for such applications as wound dressings, filtrations and bio-scaffolds.

For 72 years, scientists have been able to use electric fields to spin polymers into tiny fibers. But the fibers tangled randomly almost as soon as they are created.

In the mid-1990s, the emerging field of nanotechnology rekindled interest in electrospinning. Since then, scientists have spun more than 100 synthetic and natural polymers into fibers with diameters ranging from tens of nanometers to a few microns.

A micron is one-thousandth of a millimeter. A nanometer is one-thousandth of a micron, or about the width of 10 atoms.

When Daoheng Sun, a professor of mechanical and electrical engineering from China's Xiamen University came to Liwei Lin's laboratory at UC Berkeley for two years with the Berkeley Scholars Program in 2004, he and Lin, a professor of mechanical engineering, came up with the idea of trying to tame the electrospinning process to make orderly arrays of fibers.

"I'd been doing work with nanotechnology, but nothing on electrospinning before then," Lin said. "We were really outsiders in the field, so we didn't have any preconceived notions. We just tried things that others may have never thought about. And in the end, they worked just fine."

fibers

These orderly rows of nanofibers were created using the new near-field electrospinning process. Until now, electrospinning produced random tangles of fibers. (Photo by Ron Wilson courtesy UC Berkeley)
Lin said he foresees applications that require precise deposition of the nanofibers, such as making nanosensors for biological measurements – a glucose monitor, for instance.

Another will be to make non-woven fabrics with organized patterns that can have many applications, such as scaffolds for living cells.

Near-field electrospinning may also be useful in nanolithography for making next-generation microchips, Lin predicted. But, he said, this will require more effort to develop.

The Berkeley Scholars Program is a privately funded program founded by the Tang Family Foundation.

Today, nanomaterials are used in paints and coatings to protect against corrosion, scratches and radiation; protective and glare-reducing coatings for eyeglasses and cars; metal-cutting tools; sunscreens and cosmetics; longer-lasting tennis balls; light-weight, stronger tennis racquets; stain-free clothing and mattresses; dental-bonding agent; burn and wound dressings; ink; and automobile catalytic converters.

The federal government is spending about $1 billion per year from 2004 - 2008 to promote nanotechnology.

Useful and intriguing as nanomaterials are, the U.S. Environmental Protection Agency says there may be dangers to human health and the environment.

To date, EPA has funded 65 grants for more than $22 million related to the environmental applications or implications of manufactured nanomaterials.

"This emerging field has the potential to transform environmental protection. Researchers are now testing iron nanoparticles that could clean up pollutants in large areas of groundwater cheaper and more effectively than any existing techniques," said George Gray, assistant administrator for EPA's Office of Research and Development, announcing another round of research grants March 16.

"At the same time, we must understand whether nanomaterials could negatively impact health or the environment," said Gray. "This research will help determine the viability of nanotechnology as a tool for protecting our environment."

Even though there are hundreds of nano products already on the market in the United States, there are currently no regulations to ensure that new nanomaterials are safe for human health and the environment.

Human health research underway is testing the absorption and toxicity of nanoparticles on skin, the effects of nanoparticles on drinking water, and the effects of nanoparticles on lung tissues.

Environmental researchers are investigating the impacts on marine and freshwater sediments and on aquatic bacteria, algae and plankton; and the conditions under which nanoparticles absorb or release environmental contaminants.