Foresight Update 2

page 2

A publication of the Foresight Institute

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Technical Progress

Many readers have requested news and references on technical progress related to nanotechnology. The brief summaries below cover some recent advances in the three enabling technologies of chemistry, micromanipulation, and protein engineering.

Although many orders of magnitude larger than nanomachines, the micromechanical systems work by W. Trimmer and K. Gabriel at Bell Labs explores the feasibility of small electrostatic motors, a concept also useful on the nanometer scale. Assuming the use of standard electronic materials (silicon wafers, etc.) they present designs for electrostatic motors with diameters as small as 1 mm (Sensors and Actuators, 11, p189).

Joined by first author M. Mehregany, they have fabricated silicon gears down to a diameter of 300 microns and a micro-turbine that turns at up to 24,000 rpm (draft, "Micro Gears and Turbines Etched from Silicon.")

On the micromanipulation path, R. Becker et al., also of Bell Labs, have used a scanning tunneling microscope to make atomic-scale modifications to a surface, albeit with limited control; see discussion in this issue (Nature, 29Jan87, p419).

On the chemical path to nanotechnology, J. Rebek of U. Pittsburgh has found that synthetically-accessible small molecules can be designed to "recognize" acids, bases, amino acids, metal ions, and neutral substrates, abilities once assumed to require complex biological macromolecules. It is suggested that such small molecules can be designed and efficiently assembled to recognize almost any small molecule or ion, and that carbohydrates, peptides, and nucleotides will also be recognizable in this way (Science, 20Mar87, p1478).

The protein design path is being pursued vigorously. Scripps Clinic has received a $2.72 million NIH grant to study protein folding. Principal investigator A. Olson plans to combine NMR and X-ray crystallography data with computer graphics techniques (Genetic Tech. News, Sep87, p8).

C. Pabo and E. Suchanek of Johns Hopkins School of Medicine have a program, PROTEUS, which tests proposed modifications to a protein and could be used in de novo design as well, perhaps by starting with the desired backbone and then adding side chains (Biochem, 25, p5987--MEDLINE Abstract). J. Ponder and F. Richards of Yale propose to develop templates derived from the tertiary (i.e., high-level folding) structure of known sequenced proteins. New sequences could be tested against the templates to see whether they are likely to fold in a known way (J Mol Biol, 193, p775--MEDLINE Abstract). Both groups cite Drexler's 1981 PNAS paper as a source for their general approach.

T. Blundell et al. of the University of London advocate use of a knowledge-based approach for prediction of protein structures and the design of novel molecules, using analogies between the protein being modeled and known proteins. Subsequent X-ray analysis of several modeled proteins showed good agreement with the predicted shape (Nature, 26Mar87, p347--MEDLINE Abstract).

J. Leszczynski and G. Rose of Penn State have identified a new type of protein secondary structure termed the omega loop, an omega-shaped structure extending out from the protein surface. These loops could have important roles in recognition and may serve as convenient modules for use in protein design (Science, 14Nov86, p849--MEDLINE Abstract).

A. Napper et al. of Penn State and Scripps have used an evolutionary approach based on variation and selection within an organism's immune system, rather than deliberate design, to find a new agent of catalysis for a given chemical reaction. They obtained monoclonal antibodies elicited by an analog of the reaction's transition state, then used the antibodies as catalysts, facilitating formation of the transition state and increasing the reaction rate by a factor of 170 (Science, 28Aug87, p1041--MEDLINE Abstract).

A. Lapedes and R. Farber at Los Alamos are using neural-net simulation on a supercomputer to predict which short DNA sequences code for proteins and which do not, with 80% accuracy compared to 50% using conventional methods. Both they and, in parallel, T. Sejnowsi of Johns Hopkins are using similar techniques to try to predict a protein's structure from its sequence (Sci News, 1Aug87, p76).

R. Altman and O. Jardetzky of Stanford maintain that knowing the behavior and structure of proteins in solution, rather than in crystals, is of critical interest. They use an expert system to determine which structures are compatible with experimental data--e.g. from NMR--on proteins in solution (J Biochem, 100, p1403--MEDLINE Abstract).

J. Tiedje has found a novel anaerobic bacterium capable of dechlorinating aromatic compounds, showing that natural molecular machines can carry out unusual reactions needed to clean up toxic waste (Science, 28Aug87, p975). Specially designed nanomachines should be able to tackle even tougher cleanup tasks.

J. McBride of Yale, et al., discuss the chemistry which occurs under high stress within organic single crystals (Science, 14Nov86, p830). Such high-stress conditions, with spontaneous mechanical forces equivalent to tens of thousands of atmospheres, give some indication of the chemistry that could be done by an assembler able to hold molecules firmly, and push.

Foresight Update 2 - Table of Contents


Hypertext Publishing

A "hypertext system" can be anything from a hyper-notepad to a hyper-Library-of-Congress

Interest in hypertext is exploding, for the time being. Dozens of systems are in use, the University of North Carolina, the ACM, and the IEEE have sponsored a conference, and Apple Computer has massively promoted a new hypertext product for the Macintosh, HyperCard. There have been hopes of a hypertext revolution bringing an impact on the scale of the Gutenberg revolution. It seems to have arrived.

Or has it? Words can mean many things. A "programming language" can be anything from a system of detailed instructions for pushing bits around inside a computer, to a system of general rules for describing logical reasoning. A "hypertext system" can be anything from a hyper-notepad to a hyper-Library-of-Congress. Present systems are closer to the notepad class. We shouldn't expect them to give library-class performance.

Different hypertext systems have been built to serve different goals, though some aim to serve several. One goal is to improve personal filing systems by helping people connect information in ways that reflect how they think about it. Another is to improve educational publications by helping authors connect information in rich, explorable networks. Many recent hypertext systems are actually hypermedia systems in which authors can link descriptions to pictures, video, and sound.

Filing systems on a single machine can serve a single user or a small group. Teaching documents written on one machine, can be copied and distributed to other machines around the world. Both these goals can be served by stand-alone systems on single machines, such as HyperCard on the Macintosh. But both these goals, though valuable, are peripheral to the goal of evolving knowledge more rapidly and dependably, to improve our foresight and preparedness.

An improved medium for evolving knowledge would aid the variation and selection of ideas. To aid variation essentially means to help people express themselves more rapidly, accurately, and easily. To aid selection essentially means to help people criticize and evaluate ideas more rapidly, effectively, and easily. Several characteristics of a hypertext system are important to these goals.

To help critical discussion work effectively, a hypertext system must have full links, followable in both directions, rather than just references followable in a single direction. That is, the system must support full hypertext, not just semi-hypertext. In a semi-hypertext system, a reader cannot see what has been linked to a document, hence cannot see other reader's annotations and criticisms. Many existing hypertext systems lack full links.

To help express criticism, a hypertext system should be fine-grained. In a fine-grained system, anything--not just a document, but a paragraph, sentence, word, or link--can be the target of a link. In a fine-grained hypertext system, if you wanted to disagree with this article, you could express yourself by linking to the objectionable part (perhaps the definition of fine-grained in the previous sentence). In a coarse-grained system, you might have to link to the article as a whole. Many existing hypertext systems are coarse-grained.

To make the system a useful medium of debate, it must be public. This in turn requires suitable software, access policies, and pricing policies (such as fee-for-service, rather than free-to-an-elite). No hypertext system yet functions as a genuine public medium; many cannot do so.

To work, a public hypertext system must support filtering software. If readers automatically see all the links to a document, the equivalent of a presidential speech or an Origin of Species will become incredibly cluttered. Software mechanisms can provide a flexible way to cut through the clutter, enabling readers to be more choosey, seeing only (say) links that other readers (editors, colleagues, etc.) have recommended. There are subtleties to making filtering work well, but promising approaches are known; readers would be free to use whichever filters they think best at the moment, so filters would be free to evolve.

No existing hypertext system is full, fine-grained, filtered, and public--yet all of these characteristics (with the possible exception of "fine-grained") seem essential in a system that can make a qualitative difference in the evolution of knowledge. They are needed if we are to have a genuine hypertext publishing system.

It is this sort of system--not "a hypertext system" but a hypertext publishing system--that can make a real difference to society's overall intellectual efficiency, and overall grasp of complex issues. How great a difference? Even a small improvement in something so fundamental to our civilization would save billions of dollars, lengthen millions of lives, and give us a better chance of surviving and prospering through the coming technological revolutions. And there is reason to think the improvement might not be small.

Foresight Update 2 - Table of Contents


Nanogears, Nanobearings

Enzymes show that a nanomachine needn't have gears and bearings, but macroengineering shows how useful these parts can be. Conventional gears and bearings are built to tight tolerances--bumps a thousandth of an inch high on a one-inch part would often be too large. Since an atomically smooth surface is bumpy on a tenth-nanometer scale, it might seem that gears and bearings couldn't be reduced below 100 nm or so. A complex nanomachine using gears and bearings would then be huge--entire microns across.

A paper on "Nanomachinery: Atomically Precise Gears and Bearings" (by K. Eric Drexler, to appear in the proceedings of the November, 1987, IEEE Micro Robots and Teleoperators Workshop) examines how to build these devices much smaller. The essential insight is that an atom's surface is a soft, elastic thing, helping to smooth interactions. Conventional gears need precisely machined teeth if their hard surfaces are to mesh smoothly, but nanogears can use round, single-atom teeth, relying on atomic softness to aid smooth meshing.

This principle can also be applied to bearings. In one approach, two surfaces can slide on roller bearings. The bearings can roll smoothly, despite atomic bumpiness, by having a pattern of surface bumps that meshes smoothly, gear-fashion, with a similar pattern of bumps on the bearing race.

Mathematical analysis shows that two surfaces (of a shaft in a sleeve, for example) can slide smoothly over one another if their bumps are spaced to systematically avoid meshing. In effect, the bumps cancel out--while one is pushing back, another is pushing forward. With a ring of six atoms sliding within a ring of 22, for example, the friction force can be less than one billionth of the force holding two atoms together in a molecule.

Yet another class of bearing avoids atomic bumpiness by using a single atom or bond as a bearing. A fraction of a nanometer across, these bearings are as small as the moving parts in a nanomachine can possibly be.

Carbon skeleton for a bearing shaft with six-fold symmetry.
A few examples of more recent work on nanogears and nanobearings:

Foresight Update 2 - Table of Contents


Molecular Electronics

The proceedings volume from MEDIII (the Third International Symposium on Molecular Electronic Devices) has been delayed, but we can give a few notes on the meeting here. It was indeed international, with attendees from Europe, Japan, and Argentina as well as the US. A speaker from the USSR was scheduled, but failed to appear.

Besides many papers on conducting polymers and thin films, there were talks more directly relevant to nanotechnology. S. Staley of Carnegie-Mellon's Center for Molecular Electronics discussed work on an optically-switched molecular NAND gate. J. Milch of Eastman Kodak proposed using a molecular crystal as a cellular automaton, reminiscent of Conway's Game of Life, leading to a molecular computer.

J. Deisenhofer of the Max-Planck Institut discussed work on a molecular electronic system found in living cells, the light-driven charge separation process of photosynthesis in purple bacteria. E. Greenbaum of Oak Ridge National Lab presented experimental results on connecting photosynthesizing molecular systems to external electric circuits by means of colloidal platinum directly contacting the molecules. E. Drexler presented the nanocomputer rod logic work cited in our previous issue.

This young, chaotic field also made progress by starting to standardize its terminology. The one-page handout distributed by workshop organizers, "Molecular Electronics and Technology: Some proposed distinctions and terms," is available from the FI office.

Foresight Update 2 - Table of Contents


Britain Spearheads "Nanotechnology"

or What is Nanotechnology?

Under the headline "Funds for Nanotechnology," Britain's IEE News (October 1987) reports that "Funds are now available through the National Physical Laboratory ... for the support of projects which will lead to the commercial exploitaton of nanotechnology techniques. Nanotechnology covers the manufacture and measurement of devices and products where dimensions or tolerances are in the range 0.1 to 100 nm..." This sounds exciting until one realizes that this definition of "nanotechnology" covers everything from memory chips to electron microscopy.

The use of the term "nanotechnology" for everything smaller than 100 nanometers (0.1 micron) is apt to lead to confusion. As used in recent years in the US (and in this publication), "nanotechnology" implies a general ability to build structures to complex, atomic specifications; it refers to the technique used rather than to the size of the product.

We can see a parallel in the term "microtechnology": the broad ability to shape bulk materials into surface patterns having complex specifications on a scale of microns or less. This term does not apply to all processes having micron-scale products. Consider the case of a forest fire simulation experiment for which micron-sized particles of smoke are needed--the fire we set to produce these particles is not an example of microtechnology. Like nanotechnology, the term refers to a family of techniques and abilities, not size and scale. In the case of nanotechnology, this means structuring matter atom-by-atom with precise control. Some products of nanotechnology, such as fracture-tough diamond composite spacecraft, will not be small.

Nanotechnology is qualitatively different from microtechnology, being based on molecular operations rather than the miniaturization of bulk processes. It will enable a cube 0.1 micron on a side to hold, not just a single device, but the equivalent of an entire microprocessor. It will lead to far more than just denser circuits, more precise machines, and so forth--it will lead to self-replicating machines, cell repair systems, and a broad, deep revolution in technology, economics, and medicine.
The advance of microtechnology into the submicron regime no more calls for a change of prefix than did the similar advance of microscopy--we do not speak of "electron nanoscopes." If "nanotechnology" becomes a trendy term for submicron technology, we are in for some confusing times and a lot of wasted words used in describing assembler-based technology. The IEE News article holds no hint of real nanotechnology. Readers are encouraged to state their opinions on this matter to editors of publications which misuse the term.

One cubic nanometer of diamond, containing 176 atoms. A cube 100 nm on a side would contain 176 million atoms.

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From Foresight Update 2, originally published 15 November 1987.

Foresight thanks Dave Kilbridge for converting Update 2 to html for this web page.