Nanobots get to the heart of the matter

By Dean Irvine for CNN

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LONDON, England (CNN) -- A new breed of nanobots is being designed to assist doctors by going where no surgeon or technology has gone before.

Working at the scale of molecules, these micro-machines are taking their cues from bacteria and the way in which they find their way around the human body. If they are successful, they could bring about a new type of molecular surgery and a different perspective to our own inner space.

The engineers and scientists working on the development of these nanobots -- the size of only a few molecules -- believe they could reach liquid parts of the body difficult or impossible to get to using today's medical practices, precisely delivering drugs to areas such as the eyeball cavity or arteries in the heart.

They might sound like the stuff of science fiction, but at their most basic level these medical micro-robots are man-made protein "machines" that produce movement through chemical reactions.

Dr. James Friend, senior lecturer in the Department of Mechanical Engineering at Monash University in Australia, is developing a nanobot propelled by a tiny rotor motor measuring about five-millionths of a meter.

A simple injection would place the tiny machine into the body and it would swim to its intended target.

"We aim to provide doctors with a means to avoid major surgery and extend the capabilities of doctors to diagnose and treat patients. The powerful micro-motor will have its own power supply and be perform tasks by remote control," said Friend.

One of the most difficult tasks when developing these nanobots is creating and maintaining propulsion.

Ordinary rotors do not work on such a small scale, so Friend's micro-robot project has a special flagellated propeller, mimicking the swimming behaviour of E.coli bacteria. A strange inspiration perhaps for a potentially life-saving device.

At such a minute scale, everyday forces such as gravity are not the main obstacles to be overcome. The main challenge is overcoming viscousity, which means that completely different engineering principles are involved.

From an engineering perspective, when it comes to making micro-machines, nanotechnology has a distinct advantage over electromagnetic motors.

While conventional electromagnetic motors spin much faster, when scaled down to tiny sizes they lose torque. An electromagnetic motor that has 1mm diameter would not even be able to overcome its bearings.

With funding from the Australian Research Council, Friend's team hope to have a completed model by 2009.

Bacteria to the future

Taking queues from bacteria more directly comes the microscopic mechanical device being developed at the Japan Advanced Institute of Science and Technology in Tokyo.

Yuichi Hiratsuka and his team are creating biological motors powered by an actual bacterium called Mycoplasma mobile. In nature the bacteria infect the gills of fresh-water fish, but does not cause any disease in humans.

Hiratsuka and his team believe they could power micro-pumps on computer chips by harnessing the bacteria, likes mules to a mill wheel. The chips could be designed to analyze blood or drug compounds, in essence acting as a mini laboratory travelling through a person's blood stream.

As the devices are hybrids of inorganic and biological material, there are no wires, plus Hiratsuka believes that the nanobots could even repair themselves by using glucose in the blood stream to, in effect, refuel.

The key to moving the tiny motors comes from the nature motion of the bacterium Mycoplasma mobile. Seen under a powerful microscope, the bacteria appear pear-shaped and move along in a sliding motion.

After studying the bacterium, the team realised that it moved towards its tapered end. Attaching them to a cog made from silicon, Hiratsuka believes that it could force the rotor to turn at a rate of 2.6 rpm.

However there is some skepticism that remotely controlled man-made nano machines whizzing around our bodies will be the silver bullet for medical science, at least in our lifetimes.

It might not sound as dynamic, but instead of an all-new nano-machine with a synthesized rotor motor, one adapted from an existing bacteria would be a better bet.

Using a linear motion it could crawl along an existing line of proteins already within the human body, thereby eliminating any other complications, such as the need for its own power supply.

"Bacteria have developed all sorts of ingenious ways to travel around the body and reach all sorts of areas over millions of years. Rather than try and synthesize a bacterium, it seems more likely that we could take a virus or parasite that we already know about and tweak it," Justin Molloy, Royal Society University Research Fellow, told CNN.

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