For a Molecular Robotic "Hand"
by K. Eric Drexler, Ph.D.
For those aiming to realize the potential of
nanotechnology, a general purpose assembler is a prime goal. For that reason,
one requirement for Foresight Institute's
Feynman Grand Prize, announced last year, is the design and construction
of a functional assembler.
One can think of an assembler as a nanoscale robotic arm used in manufacturing.
An assembler would position and move individual molecules precisely with
respect to a workpiece, causing reactions, creating chemical bonds, and
thus building up a precise and functional structure. Assemblers will be
the enablers for the rest of molecular manufacturing, building more specialized
tools as needed.
Other means of assembling precise molecular structures offer considerable
promise-- protein folding, molecular self-assembly, and so forth-- but nothing
else yet suggested can approach the ability of a programmable general purpose
assembler to make almost any stable, atomically precise structure. For that
reason, the Institute for Molecular Manufacturing(IMM) has centered its efforts on assembler design.
I presented several designs for molecular manipulators, including a 100
nanometer-scale manipulator arm estimated to contain about 4 million atoms.
Many other kinds of positional devices have been proposed and used at the
macro scale, ranging from robotic arms to Stewart platforms.
In its most basic form, the Stewart platform takes the form of an octahedron
in which one triangular face is designated the "platform" and
the opposing triangular face is designated the "base." Each of
the six struts of the octahedron that connect the base to the platform can
be made longer and shorter, changing the position and orientation of the
platform with respect to the base. The six struts enable the Stewart platform
to control position and orientation in all six degrees of freedom.
An early design based on a Stewart platform was estimated to contain about
3 million atoms. Mechanisms of this size and complexity were proposed and
analyzed based upon a bounded continuum model, rather than designed in atomic
detail. Another remarkably flexible family
of six-degree-of-freedom positional devices of comparable scale has been
discussed by computational nanotechnologist Ralph Merkle of the Xerox
Palo Alto Research Center. (Dr. Merkle also serves on the board of Foresight
Institute and as an advisor to IMM.)
Although these designs appear workable, their size and complexity makes
them hard to design and model with today's computational tools. So we have
a strong incentive to "think small" even within the very small
world of nanotechnology. In collaboration with Dr. Merkle, I set out to
develop an atomically detailed design for a far smaller molecular manipulator
than previously had been considered-- one intended not to do the whole job
of molecular positioning, but to serve as a "hand" for the final,
precise step of applying a molecular tool. The resulting
design uses fewer than 3,000 atoms for its core mechanism, much reduced
from an earlier estimate of 250,000 atoms for a device with the same purpose.
A general-purpose molecular assembler arm must be able to move its "hand"
by many atomic diameters, position it with fractional-atomic-diameter accuracy,
and then execute finely-controlled motions to transfer one or a few atoms
in a guided chemical reaction. Our own arms use large muscles and joints
for large motions, but more finely-controlled finger motions for precision.
Assembler mechanisms will likely be designed along similar lines; putting
the fine-motion control capabilities into a small hand lets the rest of
the arm be much cruder and jerkier in its motions, and hence simpler to
design and build.
The accompanying illustration shows a structure
resembling a Stewart platform that results from a long series of designs
and redesigns aimed at specifying the atomic structure of a molecular-scale
fine-motion controller. Its core consists of a shaft linking two hexagonal
endplates, sandwiching a stack of eight rings.
In a complete system (batteries not yet included...), each ring would be
rotated by a lever driven by a cam mechanism. Each ring supports a strut
linked to a central platform (shown in the illustration raised, displaced,
and twisted). Rotating a ring moves a strut; moving a strut moves the platform;
positioning all eight rings determines a platform position in x, y, z, roll,
pitch, and yaw. (If the struts were rigid, six would do the job; here, two
struts have been added to increase stiffness, decrease elegance, and annoy
The chief design problem in this effort was to enable an adequate range
of motion without mechanical interference or unacceptable bond strains,
and to do so within the size constraints set by available modeling tools
and patience. Within a range of several atomic diameters and roughly 90-degree
rotations, the illustrated "hand" can position a tool anywhere,
and in any attitude. These capabilities together provide the fine control
of molecular position and motion needed to guide chemical reactions at the
surface of a workpiece-- in one process contemplated, the device would push
to make a bond, then drag to make a second bond, twist to break a double
bond, and pull to remove a handle from the spent tool.
Much work remains to be done before some successor to this mechanism can
be built and made part of a functional system, but our ability to simplify
the design and reduce its bulk (by almost a factor of 100) has been encouraging.
This suggests some of what can be done with today's tools to speed the design
Dr. Drexler is a Research Fellow with the Institute for Molecular Manufacturing.
The conference is co-chaired by Ralph Merkle of Xerox Palo Alto Research
Center and Al Globus of MJR Inc./NASA. It is expected to draw "substantially
greater participation" than the
1995 conference, said Merkle, who chaired the previous event two years
ago. "Interest in nanotechnology research in government, academic and
business circles is growing exponentially," he said.
The conference will be held November 5-8 at the Hyatt Hotel in Palo Alto,
CA. Attendance will be limited by conference facilities, so early registration
Confirmed speakers include:
Smalley, head of the Center for Nanoscale Science and Technology
at Rice University, will be the keynote speaker. Smalley is recipient
of the 1996 Nobel Prize for chemistry for the discovery of complex carbon
molecules called fullerenes. His goal is to develop nanoscale structures
and probes for such structures.
Avouris, of the IBM Research Division, T.J. Watson Research Center.
His recent work involves using scanning tunneling microscopy for studies
of site-selective chemistry on semiconductor surfaces, quantum-size effects
at metal surfaces, and the electrical properties of nanostructures.
Brenner, Materials Science and Engineering Department, North Carolina
State University. His areas of interest include the development of new strategies
for engineering nanometer-scale structures and devices.
K. Eric Drexler,
Institute for Molecular Manufacturing. Drexler, author of the field-defining
Nanosystems text, has recently published
a molecularly precise design for the "hand" of a nanoscale robot
M. Reza Ghadiri,
the Scripps Research Institute. He has developed novel methods to assemble
and study artificial proteins, molecular receptors, peptide architectures,
and self-replicating molecular systems.
James K. Gimzewski,
IBM Research Division, Zurich Research Laboratory. His recent work includes
room temperature manipulation of complex molecules.
MJR Inc./NASA Ames Research Center (co-chair of event). Globus, a computational
nanotechnologist, has worked on gear designs using fullerene structures;
he has specific interest in applications of nanotechnology to space travel.
A. Goddard III, California Institute of Technology, Materials and
Process Simulation Center. Goddard's work includes investigation of molecular
dynamics of large molecules and solids to determine the structure, vibrations,
and dynamical processes of materials and nanotechnology designs.
Ralph C. Merkle, Xerox
Palo Alto Research Center (co-chair of event). Merkle's efforts as a computational
nanotechnologist span much of the field.
Washington University (St. Louis) Laboratory for the Study of Novel Carbon
Materials. Ruoff has focused his efforts on carbon nanotube arrays, with
potential information storage and transmission applications, and upon the
mechanical properties of nanotubes.
Dan Goldin, Administrator of the National Aeronautics and Space Administration
(NASA), is invited as a speaker but has not yet confirmed.
Several of the confirmed presenters have received widespread attention in
the scientific press in recent months for their nanotechnology-related work.
Smalley has received notice for his development of fullerene
tube probes for scanning probe microscopy. Such probes allow much finer
imaging than available with mechanically sharpened probe tips.
Gimzewski and his colleagues also
have received attention for creating a molecular-scale
abacus using buckyballs (C60 molecules) as beads upon a grooved
copper plate. Although functioning only slowly as a calculator for demonstration
purposes, the work shows that complex molecules can be manipulated.
As has been the custom in the last two Molecular Nanotechnology Conferences,
Foresight will award its 1997 Feynman Prizes at the conference. This year,
two $5,000 prizes will be awarded to researchers whose recent work has most
advanced the development of molecular nanotechnology. Separate prizes will
be awarded for theoretical and experimental work.
As co-chairs of the conference, Merkle and Globus are assisted on the program
committee by Avouris, Charles W. Bauchlicher Jr. of NASA Ames Research Center,
Brenner, Drexler, Goddard, Seeman, and Smalley.
The day before the conference begins, Foresight also will offer a Tutorial
on Critical Enabling Technologies for Nanotechnology. Conference participants
Merkle, Brenner, Gimzewski, Ghadiri, and Bauschlicher will be among the
instructors in the day-long session, which will provide an introduction
and overview of four relevant fields, as well as a consideration of how
the advances in each will address the challenges raised by the design of
any molecular manufacturing system. Those with science, engineering or software
backgrounds are invited to participate and begin preparing for careers in
molecular nanotechnology. Registration
information and program details are available
An expanded list of co-sponsors for the conference includes divisions or
departments of major academic centers including Caltech, Carnegie Mellon,
Rice, University of Southern California, University of Wisconsin-Madison,
and Washington University of St. Louis. Federal research centers with co-sponsoring
divisions include Argonne National Laboratory, Lawrence Berkeley National
Laboratory, and NASA. Others include the Institute for Molecular Manufacturing,
Molecular Graphics Society of the Americas, Ohio Supercomputer Center, and
San Diego Supercomputer Center.
Proceedings of the conference will be published in a special edition of
the journal Nanotechnology.
Registration fees (before August 31) are $495 for regular registration;
$395 for academic, nonprofit and government participants, Senior Associates;
$150 for students, and $195 for single-day registration. Fees increase after
September 1. More information, including Web links to all speakers and registration
forms are available online,
or from Foresight Institute at (415) 917-1122.
For years, many Foresight and
IMM Senior Associates have been wanting to build a physical model of a nanomachine
design. They assume-- correctly-- that many people will be better able to
understand a physical model than they can a two-dimensional picture on a
Finally, there's a molecular machine design which is both complex enough
to be interesting, and has a low enough atom count that it may be feasible
for us to build a 3D physical model. Those with web access have probably
seen the new fine-motion
controller design on the IMM web site
with six-degrees of freedom in its positioning ability. (See story
on page 1 for details.)
It has only about 2600 atoms, the lowest atom count we've yet seen for an
interesting device. This has encouraged some Senior Associates to examine
the idea of building this design using CPK space-filling molecular models--
the kind used by pharmaceutical designers before molecular modeling software
became usable for their purposes. CPK (Cory, Pauling, Kultun) models are
not the ball-and-stick models you remember from undergraduate work; they
result in a 3D model that looks a lot like the computer models that IMM
has been producing on two-dimensional screens.
And best of all, in theory, they should enable the model to be moved in
a realistic fashion, with rings and bonds rotating correctly. If the Senior
Associates can make this work in the model, we will be able to show the
six-degrees-of-freedom motion of these "fingers" of the assembler.
While IMM Senior Associates
are spearheading this effort, Senior
Associates of the other Foresight organizations are also welcome to
join in. Indeed, even if you are not an Associate, if you have CPK experience
and are willing to participate, we welcome your help; please contact me
at the Foresight office.
Planning of this project, among others, will take place at the upcoming
May 2-4 Senior AssociateGathering here in Palo Alto, with an evening reception on May 2.
The program for this meeting should be up on our web site by the time you
read this; by popular demand it is going to be more informal and have more
"schmoozing" time than previous Gatherings. Contact the Foresight
office for registration information, or watch the Foresight web site-- this
is a great excuse to become a Senior Associate if you've been looking for
one. Think of it as long-term career development.
Another opportunity for career development comes this fall, with the Fifth
Foresight Conference on Molecular Nanotechnology, co-sponsored by the
Institute for Molecular Manufacturing. Those of you who have attended these
in the past may be surprised by how many prestigious organizations and researchers
are participating this year. This is due to our topic being more accepted--
considered to be more "politically-correct" by mainstream science--
than previously. Of course, having a Nobel Prizewinner, chemist Rick
Smalleyof Rice, as our keynote speaker doesn't hurt in helping
the herd instinct operate increasingly in our favor. (See page
1 for more details.)
Still more career development is available in Foresight's new series
of two-hour telephone seminars, which you'll be hearing a lot more about
in the coming months. The most exciting aspect of this new phone seminar
technology is that participants can indeed participate instead of just listening
in: the audience can ask questions of the speakers. Currently the tentative
speakers for 1997 are:
Eric Drexler and Ralph Merkle
Chris Peterson and Gayle Pergamit
Ralph Merkle and Al Globus
Winners of both the theoretical and experimental 1997 Feynman Prizes
The cost-per-site to U.S. participants for each seminar is currently planned
to be $140 for non-members, $120 for members, and $90 for Senior Associates.
More than one person can listen in at each site, so you can invite friends
over to use phone extensions or a speakerphone.
Regarding the upcoming Hyper-G project
for policy debate, starting with a computer security debate: you'll recall
from the last Update
that we were hoping to be able to join the Hyper-G
Consortium. Thanks go to Senior Associate Andre Robatino, whose timely
gift is enabling us to move ahead on this, and thereby both obtain the Hyper-G
source code and qualify for R&D grants from the Consortium.
Finally, those of you who can read this on paper only may be starting to
get the uneasy feeling that you're missing some of the action as Foresight
increasingly moves toward being a web-based organization. And it's true:
from a paper-newsletter-for-$35 model, we're moving toward a free-web-info
and high-value-Senior-Associate-services model. There's no plan to drop
the paper publication --even web users like getting it in addition to the
web information-- but over the next few years, those of you who want to
keep up on Foresight activities will increasingly feel the need to get web
access and become Senior Associates.
For the former, contact a local Internet Service Provider. For the latter,
give us a call or email; we'd love to have you on the team in time for the
Chris Peterson is Executive Director of Foresight Institute. She may
be reached at firstname.lastname@example.org.