How Nanorobots Will Work

 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.

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.

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.

  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.

  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.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.

  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.