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Andre Georges Nanorobots/Nanomedicine 3/22/99
This is a synopsis with excerpts from several of the leading experts in the field of Nanotechnology. An early author of computer replication, Von Neumann, wrote about a two dimensional cellular automata that employed a universal computer and a universal constructor. The computer would direct the constructor, which would be to fabricate another computer. Eric Drexler expanded the theory to be in miniature 3D by specifying the replication to shrink to the atomic level with the intent to manipulate surrounding atoms. The mechanism would have positional capability as well as tip chemistry. The positional robotic arm would allow the programmer to move molecular structure around while the chemical tip would alter the physical nature of the surrounding molecular structure. The size of this miniature computer, Drexler says, could be in the range of 100 cubic nanometers. This is about 0.001 cubic microns, compared to a red blood cell, which is about 8 microns in diameter. This is approximately 80 times larger than the nanorobot. At this size, the nanobot could enter a single cell for repair or alteration. One well thought out example for nanomedicine is the "respirocyte" by Robert Freitas Jr. This would serve as a super efficient red blood cell, by providing oxygen or carbon dioxide as necessary. It would be a roving thin celled tank with a brain and sensors. The material could likely be diamond arranged in a highly efficient manner as to create a very low bioactivity. It is possible that the immune system would ignore it, however, there are many alternatives to mask the pod with covalently attached biogenetic molecules that would allow it to go unnoticed. Or perhaps just because of its size, about one micron, would allow it free rein. The amazing idea about this machine is its capability. First of all, it could be programmed to seek the areas that need oxygen and arrive very rapidly. Once there, it could administer much larger quantities than a single red blood cell could. The reason for this is that it would be pressurized. A red blood cell is capable of approximately 0.51 atm of pressure, of which only 0.13 atm is deliverable to the tissues. The respirocyte could deliver easily 236 times that of the red blood cell. Drexler is stated as saying that the structure of diamond should easily withstand pressures of 1000 atm which is about 10^8 pascals. Diamond has a Young‚s Modulus of about 10^12 pascals so the pressure is well below the margin of safety. The connotations for this are incredible! Imagine sitting under water for 4 hours without needing to take a breath with the help of an injection of a liter of these respirocytes! The author, Freitas, also mentioned running at sprinting speed for 15 minutes before needing a breath of air! The nanorobots would probably be guided also by the physician with acoustic signals for behavioral modification. As a means of locomotion, Drexler imagines metabolizing the surrounding glucose in the blood stream as a power source. The power needed is probably less than 10^-9 watts, as compared to the human body, which burns about 100 watts at rest. Another area of interest is the removal of the nanorobots. One simple solution would be to filter the patients blood like a dialysis machine does. The respirocytes could be programmed to become buoyant once they were out and simply rise to the surface, where a fine screen could scoop them up. Intelligence is another topic of interest. The respirocyte would probably need only about 1000 operations per second, far less than the old Apple II. The noted Swedish expert on nanotechnology, Nick Bostrom, predicts that according to Moores Law, which describes the rate of chip expansion as doubling every 18 months, we should see computational strength equaling human capacity of 10 teraflops (~1013 operations per/sec.) by 2004. A nanostructured data storage device could be in the range of 8000 microns3, smaller than the size of a single neuron, and could store the entire Library of Congress. It could be situated strategically and interface with the brain, allowing extraordinary access toinformation. The expectations for this new age of technology will certainly change life morethan anything in history has. It sounds like the most far fetched sciencefiction, but many very level headed scientists see it as on the horizon. We could hope that people who are independently well-fed, well clothed, well housed, smart, well-educated, healthy and happy will have little motivation to make war.
Web sites referenced: http://nano.xerox.com/nanotech/nanotechAndMedicine.html |