Part 3. Nanorobot Locomotion and tools.

Nanorobot Locomotion

Assuming the nanorobot isn't tethered or designed to float passively through the bloodstream, it will need a means of propulsion to get around the body. Because it may have to travel against the flow of blood, the propulsion system has to be relatively strong for its size. Another important consideration is the safety of the patient -- the system must be able to move the nanorobot around without causing damage to the host.

Some scientists are looking at the world of microscopic organisms for inspiration. Paramecium move through their environment using tiny tail-like limbs called cilia. By vibrating the cilia, the paramecium can swim in any direction. Similar to cilia are flagella, which are longer tail structures. Organisms whip flagella around in different ways to move around.

Scientists in Israel created microrobot, a robot only a few millimeters in length, which uses small appendages to grip and crawl through blood vessels. The scientists manipulate the arms by creating magnetic fields outside the patient's body. The magnetic fields cause the robot's arms to vibrate, pushing it further through the blood vessels. The scientists point out that because all of the energy for the nanorobot comes from an external source, there's no need for an internal power source. They hope the relatively simple design will make it easy to build even smaller robots.
Other devices sound even more exotic. One would use capacitors to generate magnetic fields that would pull conductive fluids through one end of an electromagnetic pump and shoot it out the back end. The nanorobot would move around like a jet airplane. Miniaturized jet pumps could even use blood plasma to push the nanorobot forward, though, unlike the electromagnetic pump, there would need to be moving parts.

Another potential way nanorobots could move around is by using a vibrating membrane. By alternately tightening and relaxing tension on a membrane, a nanorobot could generate small amounts of thrust. On the nanoscale, this thrust could be significant enough to act as a viable source of motion.

Nanorobot tools

Current microrobots are only a few millimeters long and about a millimeter in diameter. Compared to the nanoscale, that's enormous -- a nanometer is only one-billionth of a meter, while a millimeter is one-thousandth of a meter. Future nanorobots will be so small, you'll only be able to see them with the help of a microscope. Nanorobot tools will need to be even smaller. Here are a few of the items you might find in a nanorobot's toolkit:

Medicine cavity -- a hollow section inside the nanorobot might hold small doses of medicine or chemicals. The robot could release medication directly to the site of injury or infection. Nanorobots could also carry the chemicals used in chemotherapy to treat cancer directly at the site. Although the amount of medication is relatively miniscule, applying it directly to the cancerous tissue may be more effective than traditional chemotherapy, which relies on the body's circulatory system to carry the chemicals throughout the patient's body.

Probes, knives and chisels -- to remove blockages and plaque, a nanorobot will need something to grab and break down material. They might also need a device to crush clots into very small pieces. If a partial clot breaks free and enters the bloodstream, it may cause more problems further down the circulatory system.

Microwave emitters and ultrasonic signal generators -- to destroy cancerous cells, doctors need methods that will kill a cell without rupturing it. A ruptured cancer cell might release chemicals that could cause the cancer to spread further. By using fine-tuned microwaves or ultrasonic signals, a nanorobot could break the chemical bonds in the cancerous cell, killing it without breaking the cell wall. Alternatively, the robot could emit microwaves or ultrasonic signals in order to heat the cancerous cell enough to destroy it.

Electrodes -- two electrodes protruding from the nanorobot could kill cancer cells by generating an electric current, heating the cell up until it dies.

Lasers -- tiny, powerful lasers could burn away harmful material like arterial plaque, cancerous cells or blood clots. The lasers would literally vaporize the tissue.

The two biggest challenges and concerns scientists have regarding these small tools are making them effective and making them safe. For instance, creating a small laser powerful enough to vaporize cancerous cells is a big challenge, but designing it so that the nanorobot doesn't harm surrounding healthy tissue makes the task even more difficult. While many scientific teams have developed nanorobots small enough to enter the bloodstream, that's only the first step to making nanorobots a real medical application.

Nanorobots: Today and Tomorrow

Teams around the world are working on creating the first practical medical nanorobot. Robots ranging from a millimeter in diameter to a relatively hefty two centimeters long already exist, though they are all still in the testing phase of development and haven't been used on people. We're probably several years away from seeing nanorobots enter the medical market. Today's microrobots are just prototypes that lack the ability to perform medical tasks.

Source:-

http://electronics.howstuffworks.com/nanorobot.htm