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The Vasculoid Personal Appliance
Robert A. Freitas Jr. (author, "Nanomedicine") visualizes a future "vasculoid" (vascular-like machine) that would replace human blood with some 500 trillion nanorobots distributed throughout the body’s vasculature as a coating. It could eradicate heart disease, stroke, and other vascular problems; remove parasites, bacteria, viruses, and metastasizing cancer cells to limit the spread of bloodborne disease; move lymphocytes faster to improve immune response; reduce susceptibility to chemical, biochemical, and parasitic poisons; improve physical endurance and stamina; and partially protect from various accidents and other physical harm.
Originally published March 31, 2002 by the Institute for Molecular
Manufacturing. Published on KurzweilAI.net Oct. 22, 2002.
Six years ago, while in the midst of writing the first volume of
Nanomedicine [1], I was delighted to discover the germ of a fascinating
idea for a very aggressive nanomedical augmentation, originally
called "roboblood," that had just been proposed online [2] at sci.nanotech
by Foresight Institute Senior Associate Chris Phoenix. The initial
concept elicited considerable enthusiastic discussion, but contained
what I regarded as several crucial "show-stopper"-type technical
flaws. I contacted Chris directly and we began an intermittent but
constructive collaboration that extended through 1996-2002, finally
culminating in a detailed technical paper [3] that runs ~100 pages
with more than 500 references — which I can only briefly summarize
here.
Before proceeding further, I must offer two notes of caution about
this work to two distinct audiences of possible readers. First,
conservative medical practitioners should be aware that the technical
paper summarized in this article is not intended to represent an
actual engineering design for a future nanomedical product. Rather,
the purpose is merely to examine a set of appropriate design constraints,
scaling issues, and reference designs as a purely theoretical exercise
to investigate whether or not the basic idea of a blood replacement
appliance might be feasible, and to determine key limitations of
such designs.
Second, futurist- and transhumanist-oriented readers are warned
that, in order to maintain a tight analytical focus, the technical
paper necessarily ignores many possible future nanomedical augmentations
to human cellular, tissue, and organ systems that would clearly
be accessible to a molecular manufacturing nanotechnology capable
of building the vasculoid appliance, and that might significantly
influence vasculoid architecture, utility or the advisability of
its use.
The idea of the vasculoid originated in the asking of a simple
question: Once a mature molecular nanotechnology becomes available,
could we replace blood with a single, complex robot? This robot
would duplicate all essential thermal and biochemical transport
functions of the blood, including circulation of respiratory gases,
glucose, hormones, cytokines, waste products, and all necessary
cellular components. The device would conform to the shape of existing
blood vessels. Ideally, it would replace natural blood so thoroughly
that the rest of the body would remain, at least physiochemically,
essentially unaffected. It is, in effect, a mechanically engineered
redesign of the human circulatory system that attempts to integrate
itself as an intimate personal appliance with minimal adaptation
on the part of the host human body.
A robotic device that replaces and extends the human vascular system
is properly called a "vasculoid," a vascular-like machine; but the
vasculoid is more than just an artificial vascular system. Rather,
it is a member of a class of space- or volume-filling nanomedical
augmentation devices whose function applies to the human vascular
tree.
The device is extremely complex, having ~500 trillion independent
cooperating nanorobots. In simplest terms, the vasculoid is a watertight
coating of nanomachinery distributed across the luminal surface
of the entire human vascular tree. This nanomachinery uses a ciliary
array to transport important nutrients and biological cells to the
tissues, containerized either in "tankers" (for molecules) or "boxcars"
(for cells). The basic device weighs ~2 kg and releases ~30 watts
of waste heat at a basal activity level and a maximum of ~200 watts
of power at peak activity level. The power dissipation of the human
body ranges from ~100 watts (basal) to ~1600 watts (peak) [1], so
the device presents no adverse thermogenic consequences to the user.
Power is derived from native supplies of glucose and oxygen, both
plentiful in the human body, as may be common in medical nanorobotic
systems [1, 4-8].
The most important basic structural component of the exemplar vasculoid
robot is a ~300 m2 two-dimensional vascular-surface-conforming
array of ~150 trillion "sapphiroid" (i.e., using sapphire-like building
materials) basic plates. (Thermal conductivity favors sapphire over
diamond in this application.) These square plates are nanorobots
that cover the entire luminal surface of all blood vessels in the
body, to one-plate thickness. Each basic plate is an individual
self-contained nanorobot ~1 micron thick and ~2 micron2
in surface area, a size small enough to allow adequate clearance
even in the narrowest human capillaries.
Molecule-conveying "docking bays" comprise ~24 trillion, or 16%,
of all vasculoid basic plates. Tankers containing molecules for
distribution can dock at these bays and load or unload their cargo.
Cell-conveying "cellulocks" are built on "cellulock plates" which
span the area of 30 basic plates, or 60 micron2 each.
Boxcars containing biological cells for distribution can dock at
these cellulocks and load or unload their cargo. With only 32.6
billion cellulock plates in the entire vasculoid design, cellulocks
occupy the area of 0.978 trillion basic plates or only 0.65% of
the entire vasculoid surface. The remaining ~125 trillion basic
plates are reserved for special equipment and other as-yet undefined
applications. All nanomachinery within each plate is of modular
design, permitting easy replacement and repair by mobile repair
nanorobots called vasculocytes [7].
Adjacent plates abut through flexible but watertight mechanical
interfaces on metamorphic bumpers [1] along the entire perimeter
of each plate. Each bumper has controllable variable volume, permitting
the vasculoid surface: (1) to slightly expand or contract in area,
or (2) to flex, either in response to macroscale body movements
or in response to vascular surface corrugations or other irregularities
to the same degree or better than the natural endothelium.
Thus, plated surfaces readily accommodate the natural cyclical
volume changes of various organs such as lung, bladder, or spleen.
Rigidity of the plate array is also subject to engineering control
and to localized real-time control as well, via the bumpers; diamondoid
or sapphire plating may be made substantially stiffer than natural
endothelium, if desired.
Installation of the vasculoid involves complete exsanguination
of a sedated patient, replacement of the natural circulatory fluid
with various installation fluids, followed by mechanical vascular
plating, defluidization, and finally activation of the vasculoid.
Installation takes ~6.5 hours from start to finish and requires
a peak ~200-watt power draw midway through the procedure. (By comparison,
present-day kidney dialysis treatments require 4-12 hours and the
equipment also draws a few hundred watts.) The hypothetical installation
protocol was selected for maximum comfort, reversibility, and reliability
according to contemporary medical standards.
The advantages of installing a vasculoid are potentially numerous.
Many of these benefits theoretically could be provided on a temporary
or more limited basis using terabot-dose injections of considerably
less aggressive bloodborne nanomedical devices. However, the vasculoid
appliance simultaneously provides all benefits on an essentially
permanent and whole-body basis. Additionally, some benefits appear
unique to the vasculoid and can be achieved in no other way.
Whether the entire package is sufficiently attractive to warrant
installation will probably be a matter of personal taste rather
than of medical necessity, since a molecular nanotechnology capable
of building and deploying a complex vasculoid is likely to offer
complete non-vasculoid cures for most circulatory and blood-related
disorders that plague humanity today, and biological enhancements
may also be available. And in nanomedicine, moving from an augmentation
technology that works alongside a natural system (e.g., respirocytes
[5]) to an augmentation technology that entirely replaces a natural
system (e.g., vasculoid [3]) may involve significant safety, psychological,
and even ethical considerations.
The most important benefits of vasculoid installation may include:
- Exclusion of parasites, bacteria, viruses, and metastasizing
cancer cells from the bloodflow, thus limiting the spread of bloodborne
disease. Such microorganisms and cells are easily eliminated from
the blood using ~cm3 doses of appropriately programmed
nanobiotics [1, 4], but such individual nanorobotic devices might
not normally be deployed on a permanent basis. Intracellular pathogens
that can infect motile phagocytic cells (e.g., the tuberculosis
Mycobacterium or the bacterium Listeria, both of
which can reside inside macrophages [9]) cannot be directly excluded
from the tissues when infected cells are transported by the vasculoid.
However, cell surface markers will often reveal such infection,
so vasculoid systems can check for the presence of such markers
and thus deny these cells re-entry to human tissues.
For example, the membrane surface of macrophages infected by Mycobacterium
microti is antigenically different from that of uninfected
macrophages [10]; Listeria-derived peptides are found acting
as integral membrane proteins in the plasma membrane of infected
macrophages [11], and other Listeria-infected antigen-presenting
cells display hsp60 on their plasma membranes only when infected
[12].
- Faster and more reliable trafficking of lymphocytes throughout
the secondary lymphoid organs, allowing them to survey for targeted
antigens in minutes or hours, rather than days (because both white
cells and antigenic sources can be efficiently concentrated),
thus greatly speeding the natural immune system response to foreign
antigen. This lymphocyte function might also be augmented or replaced
using individual histomobile medical nanorobots [1] or biorobots.
If biorobots are developed first, many vasculoid installations
might take place in patients possessing largely artificial immune
systems, thus obviating the need for much of the cellular component
trafficking that would otherwise be mediated by boxcars and cellulocks.
- Eradication of most serious circulatory-related pathological
conditions including all vascular disease (e.g., aortic dissection,
vessel blockages, spasms, aneurysms, phlebitis, varicose veins),
heart disease, syncope (including orthostatic hypotension) and
shock, stroke, and bleeding, due to the elimination of unconstrained
metabolite and fluid circulation.
Certain other conditions due to localized prevention of blood
flow such as bedsores and subclinical paresthesias (e.g., "pins-and-needles"
sensation) can also be ameliorated, since stiffened blood vessels
will not be nearly so easy to close via external compression.
Again, many of these conditions may already have adequate nanomedical
treatments by the time the vasculoid can be built, but other conditions
might not yet be readily or as conveniently treatable, such as
the dangers of large-scale bleeding (both internal and external).
- Reduced susceptibility to chemical, biochemical, and parasitic
poisons of all kinds, including allergenic substances in food,
air and water, although bloodborne nanotankers or pharmacytes
[1] may be able to partially duplicate this function as well.
- Faster metabolite transport and distribution, significantly
improving physical endurance and stamina, including the ability
to breathe at low O2 partial pressures and the ability
to flush out unwanted specific biochemicals from the body (a feature
which might be duplicated using bloodborne respirocyte-class devices
[1, 5]). The architecture would also permit convenient long-term
storage of protein, or amino acid recovery and recycling, which
could prove nutritionally useful.
- Direct, rapid user control of many hormonal- and neurochemical-mediated,
and all blood-mediated, physiological responses. It would be difficult
(though not impossible) to provide equivalent comprehensive whole-body
physiological control using individual micron-scale bloodborne
nanorobots alone.
- Voluntary control of capillary conductance and rigidity permitting
conscious regulation of thermal energy exchange with the environment
and at least limited control of whole-body morphological structure,
rigidity (e.g., stiffness, bending modulus, etc.), and volume
with ~millisecond response times.
- At least partial protection from various accidents and other
physical harm such as insect stings, animal bites, collisions,
bullet or shrapnel penetrations, or falling from heights. This
is perhaps the only specific benefit of the vasculoid appliance
that could not be achieved by any less radical means: extreme
trauma resistance, especially resistance to exsanguination and
cushioning against mechanical shock.
Medically oriented readers might properly wonder why anyone would
want to discuss replacing a perfectly functional natural fluid transport
system with an untested, complex, artificial, dry system with which
humans have no experience today. There are several answers to this
very good question.
First of all, medical skeptics should bear in mind that the vasculoid
appliance is clearly a highly sophisticated medical nanosystem.
It cannot be built without using a manufacturing system based on
a mature molecular nanotechnology. Its use would come only after
many decades of previous engineering experience in building, testing,
and operating such highly complex systems inside the human body.
In the future nanomedicine-rich milieu in which it would be deployed,
the vasculoid as a medical intervention may be closer to the typical
than to the extreme (as it might appear today). It is as if we were
looking forward from the limited vantage point of the 1950s —
a technological era in which vacuum tubes still reigned supreme
— to the year 2002, and estimating the future feasibility of
a 1 GHz Pentium III laptop computer (a feat of prognostication actually
achieved by Arthur C. Clarke [13]).
In the nanomedical era, it will be a matter of personal preference
and choice for each patient, in consultation with their physician,
whether the aforementioned benefits of the vasculoid appliance are
worth the risks. The device described in this article would represent
a most extreme intervention using a very advanced medical molecular
nanotechnology.
The technical paper [3] concludes: "Ultimately, and from the standpoint
of human-guided evolution, the body exists primarily to ensure the
survival of the mind — not the replication of the genes, which
was the ancient paradigm [14, 15]. It would seem that a somewhat
more advanced and compact version of the proposed device could function
independently of nearly all noncortical tissue. Thus the vasculoid
is most fascinating because it may represent one last outpost of
humanity at the final frontier of biological evolution."
Acknowledgements
The author thanks Robert J. Bradbury, Ken Clements, J. Storrs Hall,
Hugh Hixon, Tad Hogg, Markus Krummenacker, Jerry B. Lemler, M.D.,
James Logajan, Ralph C. Merkle, Rafal Smigrodzki, M.D., Tihamer
Toth-Fejel, and Brian Wowk for their comments and review of an earlier
version of the original technical paper upon which this article
was based.
© 2002 Robert A. Freitas Jr. All Rights Reserved. Published
on KurzweilAI.net with permission. The full technical article
with co-author C. Phoenix, Vasculoid:
A Personal Nanomedical Appliance to Replace Human Blood, is
also available.
References
1. Robert A. Freitas Jr., Nanomedicine, Volume I: Basic Capabilities,
Landes Bioscience, Georgetown, TX, 1999; http://www.nanomedicine.com
2. Christopher J. Phoenix, "Early Nanotech Project: Replace Blood?"
sci.nanotech posting on 14 June 1996; http://discuss.foresight.org/critmail/sci_nano/2273.html
or http://crit.org/critmail/sci_nano/2273.html
3. Robert A. Freitas Jr., Christopher J. Phoenix, "Vasculoid: A
personal nanomedical appliance to replace human blood," Journal
of Evolution and Technology, 11(April 2002); http://www.transhumanist.com/volume11/vasculoid.html,
http://www.transhumanist.com/volume11/vasculoid.pdf
4. Robert A. Freitas Jr., "Microbivores: Artificial Mechanical
Phagocytes using Digest and Discharge Protocol," Zyvex preprint,
March 2001; http://www.zyvex.com/Publications/articles/Microbivores.html.
See also: Robert A. Freitas Jr., "Microbivores: Artificial Mechanical
Phagocytes," Foresight Update No. 44, 31 March 2001, pp.
11-13; http://www.imm.org/Reports/Rep025.html
5. Robert A. Freitas Jr., "Exploratory design in medical nanotechnology:
A mechanical artificial red cell," Artificial Cells, Blood Substitutes,
and Immobil. Biotech. 26(1998):411-430; http://www.foresight.org/Nanomedicine/Respirocytes.html
6. K. Eric Drexler, Engines of Creation: The Coming Era of Nanotechnology,
Anchor Press/Doubleday, New York, 1986; http://www.foresight.org/EOC/index.html
7. Robert A. Freitas Jr., "Vasculocytes," unpublished document,
14 September 1996; http://www.foresight.org/Nanomedicine/Gallery/Species/Vasculocytes.html
8. Robert A. Freitas Jr., "Clottocytes: Artificial Mechanical Platelets,"
Foresight Update No. 41, 30 June 2000, pp. 9-11; http://www.imm.org/Reports/Rep018.html
9. Amy L. Decatur, Daniel A. Portnoy, "A PEST-like sequence in
listeriolysin O essential for Listeria monocytogenes pathogenicity,"
Science 290(3 November 2000):992-995.
10. S. Majumdar, H. Kaur, H. Vohra, G.C. Varshney, "Membrane surface
of Mycobacterium microti-infected macrophages antigenically
differs from that of uninfected macrophages," FEMS Immunol. Med.
Microbiol. 28(May 2000):71-77.
11. P.M. Allen, D.I. Beller, J. Braun, E.R. Unanue, "The handling
of Listeria monocytogenes by macrophages: the search for
an immunogenic molecule in antigen presentation," J. Immunol.
132(January 1984):323-331; P.M. Allen, E.R. Unanue, "Antigen processing
and presentation by macrophages," Am. J. Anat. 170(July 1984):483-490.
12. Cindy Belles, Alicia Kuhl, Rachel Nosheny, Simon R. Carding,
"Plasma membrane expression of heat shock protein 60 in vivo in
response to infection," Infect. Immun. 67(August 1999):4191-4200;
http://iai.asm.org/cgi/content/full/67/8/4191?view=full&pmid=10417191
13. Arthur C. Clarke, Profiles of the Future, Harper and
Row Publishers, New York, 1962.
14. Charles Darwin, The Origin of Species by Means of Natural
Selection, 1859; definitive 6th London edition: http://www.literature.org/authors/darwin-charles/the-origin-of-species-6th-edition/
15. Edward O. Wilson, Sociobiology: The New Synthesis, Harvard
University Press, Cambridge, MA, 1975.
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