There is still at present no simple and practical way to build such an assembler. It's the old problem of the chicken and the egg. You need an assembler to make an assembler. Catch 22.
Researchers seeking a way around this deadlock have proposed two possible solutions, called, reasonably enough, "Top Down" and "Bottom Up"
One corporation that is backing nanotech research and development is the NanoTechnology Development Corporation in Houston, Texas. In addition to funding companies developing nano-scale manufacturing technologies and equipment, NTDC also considers corporations whose technologies hold promise in manufacturing processes associated with the top down or bottom up approaches, or whose macro scale technology holds promise for being scaled down to the nanometer realm and are capable of facilitating mature MNT.
The "Top Down" approach is already shown in computer manufacturing, where the race for faster and more powerful chips is leading to greater and greater precision and miniatarisation.
Another way of doing things here would be a larger machine that can make a smaller machines and so on (which as we have seen was Feynman's suggestion). This is already being built by a company called Robodyne, which is being backed by NanoTechnology Development Corporation.
Fractal robots are programmable machines that can do unlimited tasks in the physical world, the world of matter. With the right software the same device can remove household refuse and deliver to a pre-determined location, paint a car, or construct an office building and later, wash that building's windows. This is an example of programmable "Digital Matter".
A fractal robot essentially resembles a Rubicís Cube. Each of the component blocks can slide over each other on command, changing and moving in any overall shape desired for a particular task. The cubes communicate with each other and share power. When sufficiently miniaturized (below 0.1mm) and fabricated using photolithography methods, cubes can also be programmed to assemble other cubes of smaller or larger size. Over the last year, Robodyne has been demonstrating 30 cm prototype cubes. It already has plans to use large cubes in the bridge-building industry.
The "Bottom Up" advocates try to "bootstrap" molecular nanotech by designing and building a nano assembler directly (essentially, pulling it up by it's own bootstraps), using existing technology. Here again we have a number of possible approaches:
The first approach is the very diverse field of biotechnology, including protein design, biomimetic chemistry, and working with DNA.
This biotech Bottom Up method is being explored by Professor Nadrian C. Seeman of New York University, who is working on nanotechnological applications of DNA. By attaching specific "sticky ends" to a DNA branched junction, his team has already been able to build a tiny cube and a truncated octahedron out of DNA. The ultimate goals for this approach include the synthesis of crystalline matter and the assembly of a biochip computer.
An alternative Bottom Up approach involves atomic positioning; technically known as mechanochemistry, whereby a chemical reaction helped over its normal reaction barriers by mechanical force. In other words, manually shoving atoms together. This is the path being followed by Texas-based Zyvex, the world's first nanotechnology firm, founded in April of last year by software magnate James Von Ehr for the purpose of building Drexler and Merkle style assemblers using STMs in a high vacuum environment. Mr Von Ehr told me "We're spending most of our time on mechanochemistry, but with the goal of building a Drexler/Merkle style assembler with a present-day macroscopic STM or AFM."
A more unconventional bottom up approach is suggested by Forrest Bishop, a prolific formulator of nano-devices. He proposes an Optical Assembler, which uses light emission to create a wave front that's steerable like phased array radar, in order to push atoms into position. Although vast, the computing power for stearing and positional control is obtainable. It sounds like pure science fiction, and indeed Bishop points out the similarity of his Optical Assembler to the "replicator" of Star Trek.
Perhaps the most commonly asked question about nanotechnology is: how long will it take to develop? Although prediction is a risky business, Ralph Merkle observes that if the trend in miniaturisation in the computer industry continues, nanotech is likely to come about "in the 2010 to 2020 time frame." James Von Ehr answered "more than 5 years" to the goal of a working prototype Drexlerian assembler. Expect something soon. But donít hold your breath.
However it is achieved, one thing is certain; with the invention of the working assembler, we will witness a technological revolution unparalleled in human history; a revolution that will quite possibly occur within our lifetimes.
NanoTechnology Development Corporation
Robotic Construction International - the fractal robot
Ned Seeman's Laboratory Home Page - building nano-structures with DNA
Zyvex home page
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