Introduction to How Nanorobots Will Work

Imagine going to the doctor to get treatment for a persistent fever. Instead of giving you a pill or a shot, the doctor refers you to a special medical team which implants a tiny robot into your bloodstream. The robot detects the cause of your fever, travels to the appropriate system and provides a dose of medication directly to the infected area.

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nanorobot
The robot in this illustration swims through the arteries and veins using a pair of tail appendages.
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Surprisingly, we're not that far off from seeing devices like this actually used in medical procedures. They're called nanorobots and engineering teams around the world are working to design robots that will eventually be used to treat everything from hemophilia to cancer.

Bigger Isn't Always Better
In 1959, Richard Feynman, an engineer at CalTech, issued a challenge to engineers everywhere. He wanted someone to build a working motor that could fit within a cube 1/64th of an inch on each side. His hope was that by designing and building such a motor, engineers would develop new production methods that could be used in the emerging field of nanotechnology. In 1960, Bill McLellan claimed the prize, having built a working motor to the proper specifications. Feynman awarded the prize even though McLellan built the motor by hand without devising any new production methodologies.

As you can imagine, the challenges facing engineers are daunting. A viable nanorobot has to be small and agile enough to navigate through the human circulatory system, an incredibly complex network of veins and arteries. The robot must also have the capacity to carry medication or miniature tools. Assuming the nanorobot isn't meant to stay in the patient forever, it also has to be able to make its way out of the host.

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In this article, we'll learn about the potential applications of nanorobots, the various ways nanorobots will navigate and move through our bodies, the tools they will use to heal patients, the progress teams around the world have made so far and what theorists see in the future.

In the next section, we'll learn about the conditions and diseases nanorobots will treat in the future.

Take Two Bots and Call Me in the Morning

Properly realized, nanorobots will be able to treat a host of diseases and conditions. While their size means they can only carry very small payloads of medicine or equipment, many doctors and engineers believe the precise application of these tools will be more effective than more traditional methods. For example, a doctor might deliver a powerful antibiotic to a patient through a syringe to help his immune system. The antibiotic becomes diluted while it travels through the patient's bloodstream, causing only some of it makes it to the point of infection. However, a nanorobot -- or team of nanorobots -- could travel to the point of infection directly and deliver a small dose of medication. The patient would potentially suffer fewer side effects from the medication.

Several engineers, scientists and doctors believe that nanorobot applications are practically unlimited. Some of the most likely uses include:

  • Treating arteriosclerosis: Arteriosclerosis refers to a condition where plaque builds along the walls of arteries. Nanorobots could conceivably treat the condition by cutting away the plaque, which would then enter the bloodstream.

    lithotripsy
    Nanorobots may treat conditions like arteriosclerosis by physically chipping away the plaque along artery walls.

  • Breaking up blood clots: Blood clots can cause complications ranging from muscle death to a stroke. Nanorobots could travel to a clot and break it up. This application is one of the most dangerous uses for nanorobots -- the robot must be able to remove the blockage without losing small pieces in the bloodstream, which could then travel elsewhere in the body and cause more problems. The robot must also be small enough so that it doesn't block the flow of blood itself.
  • Fighting cancer: Doctors hope to use nanorobots to treat cancer patients. The robots could either attack tumors directly using lasers, microwaves or ultrasonic signals or they could be part of a chemotherapy treatment, delivering medication directly to the cancer site. Doctors believe that by delivering small but precise doses of medication to the patient, side effects will be minimized without a loss in the medication's effectiveness.
  • Helping the body clot: One particular kind of nanorobot is the clottocyte, or artificial platelet. The clottocyte carries a small mesh net that dissolves into a sticky membrane upon contact with blood plasma. According to Robert A. Freitas, Jr., the man who designed the clottocyte, clotting could be up to 1,000 times faster than the body's natural clotting mechanism [source: Freitas]. Doctors could use clottocytes to treat hemophiliacs or patients with serious open wounds.
  • Parasite Removal: Nanorobots could wage micro-war on bacteria and small parasitic organisms inside a patient. It might take several nanorobots working together to destroy all the parasites.
  • Gout: Gout is a condition where the kidneys lose the ability to remove waste from the breakdown of fats from the bloodstream. This waste sometimes crystallizes at points near joints like the knees and ankles. People who suffer from gout experience intense pain at these joints. A nanorobot could break up the crystalline structures at the joints, providing relief from the symptoms, though it wouldn't be able to reverse the condition permanently.
  • Breaking up kidney stones: Kidney stones can be intensely painful -- the larger the stone the more difficult it is to pass. Doctors break up large kidney stones using ultrasonic frequencies, but it's not always effective. A nanorobot could break up a kidney stones using a small laser.

    lithotripsy
    Nanorobots might carry small ultrasonic signal generators to deliver frequencies directly to kidney stones.

  • Cleaning wounds: Nanorobots could help remove debris from wounds, decreasing the likelihood of infection. They would be particularly useful in cases of puncture wounds, where it might be difficult to treat using more conventional methods.

In the next section, we'll see how nanorobots will navigate through the circulatory system.

Nanorobot Navigation

There are three main considerations scientists need to focus on when looking at nanorobots moving through the body -- navigation, power and how the nanorobot will move through blood vessels. Nanotechnologists are looking at different options for each of these considerations, each of which has positive and negative aspects. Most options can be divided into one of two categories: external systems and onboard systems.

External navigation systems might use a variety of different methods to pilot the nanorobot to the right location. One of these methods is to use ultrasonic signals to detect the nanorobot's location and direct it to the right destination. Doctors would beam ultrasonic signals into the patient's body. The signals would either pass through the body, reflect back to the source of the signals, or both. The nanorobot could emit pulses of ultrasonic signals, which doctors could detect using special equipment with ultrasonic sensors. Doctors could keep track of the nanorobot's location and maneuver it to the right part of the patient's body.

MRI machine
Photo courtesy NASA
Some scientists plan to control
and power nanorobots
using MRI devices like this one.

Using a Magnetic Resonance Imaging (MRI) device, doctors could locate and track a nanorobot by detecting its magnetic field. Doctors and engineers at the Ecole Polytechnique de Montreal demonstrated how they could detect, track, control and even propel a nanorobot using MRI. They tested their findings by maneuvering a small magnetic particle through a pig's arteries using specialized software on an MRI machine. Because many hospitals have MRI machines, this might become the industry standard -- hospitals won't have to invest in expensive, unproven technologies.

Doctors might also track nanorobots by injecting a radioactive dye into the patient's bloodstream. They would then use a fluoroscope or similar device to detect the radioactive dye as it moves through the circulatory system. Complex three-dimensional images would indicate where the nanorobot is located. Alternatively, the nanorobot could emit the radioactive dye, creating a pathway behind it as it moves through the body.

Other methods of detecting the nanorobot include using X-rays, radio waves, microwaves or heat. Right now, our technology using these methods on nano-sized objects is limited, so it's much more likely that future systems will rely more on other methods.

Onboard systems, or internal sensors, might also play a large role in navigation. A nanorobot with chemical sensors could detect and follow the trail of specific chemicals to reach the right location. A spectroscopic sensor would allow the nanorobot to take samples of surrounding tissue, analyze them and follow a path of the right combination of chemicals.

Hard as it may be to imagine, nanorobots might include a miniature television camera. An operator at a console will be able to steer the device while watching a live video feed, navigating it through the body manually. Camera systems are fairly complex, so it might be a few years before nanotechnologists can create a reliable system that can fit inside a tiny robot.

In the next section, we'll look at nanorobot power systems.

Powering the Nanorobot

Just like the navigation systems, nanotechnologists are considering both external and internal power sources. Some designs rely on the nanorobot using the patient's own body as a way of generating power. Other designs include a small power source on board the robot itself. Finally, some designs use forces outside the patient's body to power the robot.

Nanorobots could get power directly from the bloodstream. A nanorobot with mounted electrodes could form a battery using the electrolytes found in blood. Another option is to create chemical reactions with blood to burn it for energy. The nanorobot would hold a small supply of chemicals that would become a fuel source when combined with blood.

A nanorobot could use the patient's body heat to create power, but there would need to be a gradient of temperatures to manage it. Power generation would be a result of the Seebeck effect. The Seebeck effect occurs when two conductors made of different metals are joined at two points that are kept at two different temperatures. The metal conductors become a thermocouple, meaning that they generate voltage when the junctures are at different temperatures. Since it's difficult to rely on temperature gradients within the body, it's unlikely we'll see many nanorobots use body heat for power.

While it might be possible to create batteries small enough to fit inside a nanorobot, they aren't generally seen as a viable power source. The problem is that batteries supply a relatively small amount of power related to their size and weight, so a very small battery would only provide a fraction of the power a nanorobot would need. A more likely candidate is a capacitor, which has a slightly better power-to-weight ratio.

capcitor
© Photographer: Newstocker I Agency: Dreamstime.com
Engineers are working on building smaller capacitors that will power technology like nanorobots.
Another possibility for nanorobot power is to use a nuclear power source. The thought of a tiny robot powered by nuclear energy gives some people the willies, but keep in mind the amount of material is small and, according to some experts, easy to shield [source: Rubinstein]. Still, public opinions regarding nuclear power make this possibility unlikely at best.

External power sources include systems where the nanorobot is either tethered to the outside world or is controlled without a physical tether. Tethered systems would need a wire between the nanorobot and the power source. The wire would need to be strong, but it would also need to move effortlessly through the human body without causing damage. A physical tether could supply power either by electricity or optically. Optical systems use light through fiber optics, which would then need to be converted into electricity on board the robot.

The Piezoelectric Effect
Some crystals gain an electrical charge if you apply force to them. Conversely, if you apply an electric charge to one of these crystals, it will vibrate as a result, giving off ultrasonic signals. Quartz is probably the most familiar crystal with piezoelectric effects.

External systems that don't use tethers could rely on microwaves, ultrasonic signals or magnetic fields. Microwaves are the least likely, since beaming them into a patient would result in damaged tissue, since the patient's body would absorb most of the microwaves and heat up as a result. A nanorobot with a piezoelectric membrane could pick up ultrasonic signals and convert them into electricity. Systems using magnetic fields, like the one doctors are experimenting with in Montreal, can either manipulate the nanorobot directly or induce an electrical current in a closed conducting loop in the robot.

In the next section, we'll look at nanorobot propulsion systems.

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.

flagella
Nanorobot designers sometimes look at microscopic organisms for propulsion inspiration, like the flagellum on this e-coli cell.
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.

In the next section, we'll look at the tools nanorobots might carry to fulfill their medical missions.

Teeny, Tiny Tools

red blood cells
Photo courtesy Garrigan.net
Nanorobot tools will have to
be small enough to manipulate
cells like these red blood cells.
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.

In the next section, we'll learn about where nanorobot technology is today and where it might be in the future.

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.

2-centimeter-long robot
Yoshikazu Tsuno/AFP/Getty Images
Although this 2-centimeter-long robot
is an impressive achievement,
future robots will be hundreds
of times smaller.
In the future, nanorobots could revolutionize medicine. Doctors could treat everything from heart disease to cancer using tiny robots the size of bacteria, a scale much smaller than today's robots. Robots might work alone or in teams to eradicate disease and treat other conditions. Some believe that semiautonomous nanorobots are right around the corner -- doctors would implant robots able to patrol a human's body, reacting to any problems that pop up. Unlike acute treatment, these robots would stay in the patient's body forever.

Another potential future application of nanorobot technology is to re-engineer our bodies to become resistant to disease, increase our strength or even improve our intelligence. Dr. Richard Thompson, a former professor of ethics, has written about the ethical implications of nanotechnology. He says the most important tool is communication, and that it's pivotal for communities, medical organizations and the government to talk about nanotechnology now, while the industry is still in its infancy.

Will we one day have thousands of microscopic robots rushing around in our veins, making corrections and healing our cuts, bruises and illnesses? With nanotechnology, it seems like anything is possible.

To learn more about nanotechnology, follow the links on the next page.

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Sources

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