Simple math: If a nanobot had wheels 20 nm in diameter, it could move about 62 nm in one rotation of those wheels. If the wheels can be made to turn at one million RPM, possibly through agitation by high frequency radio energy, the nanobot would travel at 62 million nm per minute, 1 millimeters per second, 3.6 meters (12 feet) per hour, or 89 meters in a day. This seems quite fast for something so small, but I am not reflecting on the feasibility of such rapid rotation or any other physical problems with using wheels at this scale. Of course, if the nanobot’s wheels can be made to turn at only one rotation per second its speed would be reduced to about 0.2 millimeters per hour or about 5 millimeters per day, but that is still fast enough for some important tasks as long as the nanobots are delivered quite close to where they will be needed and sufficient time is available for them to make the journey. Clearly, mobility will be needed for many nanotechnology applications, but how else might it be achieved?
Wheels, however, may not be the best way for a nanobot to move, due to surface tension and other forces that become extremely important at nano-scale. For this reason spider-like, walking nanobots may work better. If the nanobot takes steps of 5 nm each and can be made to move at a million steps per second, the nanobot will move at .005 meters per second, 18 meters per hour, or almost a quarter-mile per day. At 10 steps per second the nanobot would only move at about 0.18 mm per hour or 0.17 inches per day .
Other alternative methods of locomotion will be required. In many applications nanobots may have to swim to move. If a nanobot moves at a rate of 1000 nm per second that translates to only .0036 meters per hour, and only 86 cm (less than a yard) per day.
One remedy for the slow speed of nanobots, and for situations where a nanobot can’t be designed to move on its own, is to hitchhike by grabbing onto moving objects and letting go at a chosen place, time, or signal. Minimal steering and propulsion capability would permit moving to the target object or stream of fluid, or steering in moving fluids.
Specially designed nanobots might provide transportation for others. Some nanobots might be designed for the sole function of moving non-mobile nanobots around, functioning like tow trucks or container ships. Nanobots might also grab onto each other in a line, with one on the end of the line grabbing onto a “tractor” nanobot that would pull the string like a railroad train.
How can a nanobot be made to reach the right destination? For a nanobot to know where it is going would require a fairly complex intelligence in software and hardware, and the small size of the nanobot might not permit such complexity. The challenge of building such intelligence into a nanobot might remain beyond us for some time, but there are other possibilities.
Nanobots might use molecular “recognition” to identify their targets. In a direct copy of biological microorganisms, a nanobot might have an external molecular key structure such that contact with a target object would enable it to grab on, while contact with other objects without the right molecular structure would have no effect. In the large numbers in which nanobots are expected to be made, as long as a portion of the nanobots reached their intended targets their purpose might be achieved.
Nanobots can already be created with radio receivers. It is possible that externally applied radio signals could be used to control nanobots, changing their mode of operation once significant numbers of them are in an intended position. Transmitting radio signals requires amounts of energy so far unavailable to nanobots, however, leaving the job to microbots or larger devices.
Different sized, specialized nano- and microbots could work together. As has been mentioned in earlier blog articles here, larger microbots, a thousand or more times the size of nanobots but still too small to see with the naked eye, might be able to contain computing and communications capabilities advanced enough to receive external signals, interact with human-operated controls, and issue commands, using chemicals or radio transmissions, for example, to control large numbers of nanobots.
Eventually much more than we can now imagine will exist. I’ve long said that tomorrow’s great ideas usually look crazy or impossible to us now, as otherwise we’d all be using them today. Some of our daydreams today, however, will guide the research of the future, so we must keep dreaming, thinking, recording our thoughts, and communicating them so our combined creativity can lead to a better future for all.
Nanoscience and nanotechnologies: opportunities and uncertainties, 2004, The Royal Academy of Engineering
Nanotechnology War and Just How Big Are Nanobots Anyway?, 2008, Tim Prosser
Nanobot Communications, Power Sources, and Nanotechnology War, 2008, Tim Prosser