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Archival Page—Content Superseded

Foresight Institute Adopts New Mission

The proposals described on this page were developed in late 2003 and announced in Foresight Update 53. The proposals below, however, were eventually altered after leadership changes and as a result of a reevaluation of Foresight's strategic plan that was done during the second half of 2004. Recently, Foresight announced a new mission. For more details, see About the Foresight Nanotech Institute and the Foresight Nanotechnology Challenges. If you would like to contribute to specific projects and initiatives that Foresight is developing: see Foresight projects for directed giving. To personally experience Foresight in action, attend Foresight's next conference: Advancing Beneficial Nanotechnology: Focusing on the Cutting Edge, 13th Foresight Conference on Advanced Nanotechnology.


Project: Design and Simulation of Nanomechanisms

Project manager: J. Storrs Hall, Ph.D.

Summary:

Simulate—test and make movies of—nanomechanisms from gears and shafts to robot arms, at the molecular dynamics (MD) level. Two main purposes are served:

First, on a technical level, significant progress in the actual design of molecular manufacturing systems can be achieved.

Second, on an educational level, movies will serve to give those who have not studied the concepts, a much-more-nearly-correct impression of just what is being proposed, and how things at the molecular scale actually work. Over the past decade, in the absence of specific designs presented in a form readily grasped by a general audience, a number of strawman concepts have appeared that have muddied the waters. Movies based on a level of simulation with a reasonable claim to scientific validity would go far toward clearing this up.

Current Status:

The project is currently supported entirely by the efforts and resources of Dr. Hall. Some preliminary results are available, in the form of movies of simulations of the Drexler/Merkle planetary gear (see below). Two months of effort have resulted in a new MD simulator designed specifically for nanomechanical applications (see Technical Rationale).

Goals and Necessary Resources:

In simple terms the goal is to extend the existing simulation of one gearbox doing half a turn to a robot arm doing mechanosynthesis. This will involve three major factors: actual designs to simulate; computing machinery adequate to the task; and software for doing the above.

Designs

Nanosystems is packed with appropriate next steps in this direction, but actual atomically-detailed designs are few and far between. Given the resources noted below, progress in this area is a "just do it" item.

Computers

Although the new simulator brings devices on the scale of the planetary gear (~3500 atoms) to within the purview of a somewhat annuated personal workstation, it only just does. For work on larger systems and longer timeframes, significantly more horsepower is needed.

Software

The new simulator needs to be extended in two major directions. Currently it has rudimentary controls and analysis capabilities, both of which need to be extended for use as an engineering tool. Also, there are a number of techniques that could be added to make large simulations faster.

A CAD system for for new nanomechanical designs is also desirable; see Technical Rationale.

Scope of Project and Budget:

The largest scope envisioned would be two people working with Dr. Hall, one a software and one a computational chemistry expert. If not fully supported, full time employees could be replaced with part-time or student help, or volunteer help, with concomitantly less progress.

Computer hardware, software, support, operations: $25,000 / yr
Overhead, travel, journals, secretarial, etc $25,000 / yr
Each employee, if full time (including overhead): $150,000 / yr
Each employee, if summer student (including overhead): $50,000 / yr

Thus a useful level of effort could be sustained for $50,000 /yr and the full envisioned project could absorb up to $350,000 / yr; rate of progress could reasonably be extrapolated as a linear function of support level.

Timetable

At a full level of support:

First year : designs and movies for a basic array of mechanical parts and subsystems (e.g., gears). Software to simulate and design same. (e.g., atom-at-a-time CAD)

Second year : designs and movies for complex systems with power (e.g., motors, computers). Software to simulate and design same. (e.g., matter compilers)

Second year : designs and movies for complete systems doing chemistry, e.g., assembler arms. Software to simulate and design same.

Technical Rationale:

Existing molecular CAD and simulation systems are designed for doing solution and/or gas phase chemistry, or for analysis of (bulk) materials. None is aimed at the nanomechanical realm where large numbers of stiff parts move and interact with relatively high contact forces, as in a machine.

In chemistry software, much time is spent, both in development and runtime, accurately simulating second and third-order forces which have little or no effect on nanomechanical operations. Meanwhile, chemistry programs do not have the instrumentation and test fixtures—software "motors" and "dynamometers"—that are necessary for the proper testing and development of machines.

A particularly important area that needs to be addressed in moving to the ability to do larger systems is multi-level simulation. This will most likely have to take the form of encapsulating phenomena that are specific to nanomechanical design and not found in any existing codes.

To produce useful results, specifically designs and movies, the software being developed does not have to be developed to anywhere near commercial standards (e.g., of portability, generality, and foolproofness). Thus the development envisioned will not take nearly as much time or resources as if such systems were being developed as products.

We do not envision, however, writing lower-level chemistry software (e.g., quantum-level molecular orbitals codes for validation and calibration of bond-making and -breaking heuristics). Existing codes would be obtained.

Preliminary results/ example movies:

Background

In the '90's a group at Caltech did some MD simulations of Drexler and Merkle's planetary gear—surprisingly, the only simulations of these nanomechanisms done to date. However, because of the amount of CPU time available and high computational complexity of the algorithms they were using, they tried to see too much action with too little time. The result was to simulate the gear at something like 1000 times its designed speed, with predictable results.
(See http://www.wag.caltech.edu/gallery/gallery_nanotec.html)

I simulated the gear at a number of different speeds. The results are markedly different, though at the higher speeds the phenomena are similar to the Caltech movies.

My movies can be found at http://discuss.foresight.org/~josh/*.mpg (see individual names below)

The actual simulation step for all movies is 0.1 fs—the atomic positions you see are averaged over 500 or 750 steps. Thus you do not see the fastest thermal vibration (but there are plenty of slower modes!) The longer movies represent about a million simulation steps.

The "motor" simulates the characteristics of an electric motor's linear speed/torque curve. It is connected to the input shaft/sun gear, and the rest of the mechanism is free—note the counter-rotation of the ring. In a real gear this is a good test of friction; i.e., an unoiled gear will simply rotate as a unit.

Note that the Caltech simulator did not have a motor—they simply initialized the velocity of the sun gear to a high speed, and let it rip.

  frame "motor"  
Movie timestep
fs
stall torque
nN nm
no-load speed
GHz
 
short (~6 sec)
 
       
gear.mpg 50 25 1000 not minimized
gear2.mpg 50 25 1000 minimized
 
long (~1 min)
 
       
longear.mpg 75 10 250 minimized
slogear.mpg 75 10 25 minimized

 

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