Question 1: Tell us about yourself. What is your background, and what is your current affiliation?

I received an undergraduate B.S. degree from Harvey Mudd College (dual major, physics and psychology) in 1974 and a Juris Doctor (J.D.) graduate degree from University of Santa Clara School of Law in 1978.  In the late 1970s and early 1980s I published numerous editions of Lobbying for Space, the first space program political advocacy handbook ever published, and conducted three separate observational SETA/SETI programs with a colleague, using both optical and radio telescopes.  I co-edited the 1980 NASA feasibility analysis of self-replicating space factories and in 1996 authored the first detailed technical design study of a medical nanorobot ever published in a peer-reviewed mainstream biomedical journal.  After a stint as Research Scientist at Zyvex Corp. from 2000-2004, I’m now back with the Institute for Molecular Manufacturing, my previous and current primary affiliation, as their Senior Research Fellow.

Question 2: When and how did you first hear about molecular nanotechnology? At what point did you decide to devote your career to this field?

The first time I ever thought about atomic-scale engineered objects was probably in 1977-78, when I was working on my first treatise-length book project (Xenology).  In Chapter 16 of that book, I hypothesized that “using molecular electronics with components on the order of 10 Å in size, 10¹⁰ microneurons could be packed into a space of a few microns” which would be “small enough to hide inside a bacterium.”  During my NASA work on self-replicating machines in the summer of 1980, I wondered how small machine replicators might be made.  I briefly studied the emerging micromachine technology, but by the time Engines of Creation came out in 1986 I had temporarily left the field in pursuit of more pragmatic opportunities.  In early 1994 I happened to pick up and read a copy of Unbounding the Future.  This was my first exposure to what has come to be known as molecular nanotechnology (MNT).  I studied the detailed technical arguments presented in Nanosystems, which confirmed what I had already suspected based on my own knowledge — namely, that the technical case for molecular nanotechnology was very solid.

Having fully absorbed the MNT paradigm, I immediately realized that medicine would be the single most important application area of this new technology.  In particular, nanomedicine offered a chance for significant healthspan (healthy lifespan) extension.  It also appeared that this objective could possibly be achieved within the several decades of life actuarially remaining to me and others of my generation.  But was anyone pushing it forward?  I contacted the Foresight Institute and learned that nobody had yet written any systematic treatment of this area, nor was anyone planning to do so in the near future.  So I took up the challenge of writing Nanomedicine, the first book-length technical discussion of the potential medical applications of molecular nanotechnology and medical nanorobotics.

I’ve been writing the Nanomedicine book series since 1994.  This technical book is my attempt to rationally assess various possible nanorobotic capabilities and medical systems to determine which ones might be plausible (and which ones not) if we could build nanorobots at some point in the future. The first volume (I) was published by Landes Bioscience in 1999 and is freely available online.  The second volume (IIA) was also published by Landes Bioscience, in 2003, and is also freely available online.  I’m still writing the last 2 volumes (IIB, III) of this book series, an ongoing effort that will continue during 2005-2010.

Question 3: Recently, the Foresight community has de-emphasized molecular assemblers in favor of a desktop manufacturing paradigm. What brought about this shift? How will this change affect the field?

While I’m not involved in the decisions of the Foresight Institute, I believe the shift occurred primarily as an attempt to redirect the often rancorous scientific debate away from the growing fears of runaway motile free-range replicators, and away from the seeming impossibility of building self-replicating machines (a prejudice common to many ill-informed scientists), and towards a more rational consideration of the underlying technologies and their benefits.  The civility of the public discourse may improve as a result, and to the extent that the mainstream scientific community begins to pay attention, it is possible that the research funding situation might also improve.  I’m all for it.

However, the change probably won’t much affect the actual research in the field, nor the achievement of useful results per dollar spent, because in truth the distinction between “molecular assemblers” and “nanofactories” is largely cosmetic.  That is, if you possess either one, you can use it either to replicate itself or to build the other in very short order.  Either one can be used equally well to build life-saving medical nanorobots or life-denying nanoweapons, including everyone’s favorite bugaboo, the marauding ecophages.  Both assemblers and nanofactories are examples of molecular manufacturing, which depends at its core on some form of replicative or massively-parallel fabrication and assembly capability in order to be able to economically generate macroscale quantities of useful end products.  The two approaches differ mainly in their technical design/performance tradeoffs.  Each approach has different strengths and weaknesses (as manufacturing systems) that can be readily enumerated.  I’ve been writing about both approaches since the 1980 NASA replicating factory study – wherein I was actually the main proponent for the factory approach.  The key thing is that molecular assemblers and nanofactories are both molecular manufacturing systems.  Each requires almost exactly the same set of enabling technologies.  Developing those enabling technologies as soon as possible should be our primary focus right now.

Question 4: Do you agree with those who claim that the desktop manufacturing paradigm could become a reality by 2020?

I would not be surprised if the fabrication of medical nanorobots (and other useful nanorobotic systems) via molecular manufacturing – whether via molecular assemblers or nanofactories – arrives during the decade of the 2020s.

As noted earlier, I undertook the Nanomedicine book series in an attempt to establish a solid foundation for the single most important future application of MNT.  The book introduces a long-term vision for nanorobotic medicine and articulates the technical underpinnings of that vision, so that when the day arrives that we have the technology to build such devices, we’ll have a clearer idea what can be done with them, and how.

More recently, to answer those who remain skeptical of the entire MNT enterprise, including the possibility of medical nanorobotics, I’ve turned my attention to figuring out how to build the nanorobots – the issue of implementation of the long-term vision.  My early work on diamond mechanosynthesis is described in a lecture I gave at the 2004 Foresight Conference in Washington DC, the text of which (plus many images) is available online.  I’m now involved in 6 research collaborations with various university and corporate groups in the U.S, U.K. and Russia in an effort to push forward the technology in this area as fast as possible.  These collaborations include a variety of computational chemistry simulations of plausible mechanosynthetic tooltips and reaction sequences, coupled with a nascent experimental effort that is just starting up.  I have several new papers on diamond mechanosynthesis nearing completion for journal submission, for publication in 2006.  Earlier this year I also filed the first-ever U.S. patent on diamond mechanosynthesis that describes a specific process for achieving molecularly precise diamond structures in a practical way.

Ralph Merkle and I are also writing an entire book-length discussion of diamond mechanosynthesis, entitled Diamond Surfaces and Diamond Mechanosynthesis (DSDM), to be published in 2006 or 2007.  The first half of this book is an extensive review of all that is presently known about diamond surfaces, and has been mostly written for several years.  The second half describes specific tools and reaction pathways for building those surfaces using positionally controlled mechanosynthetic tools, and methods for building those tools.  This part has been about 50% written for several years.  But finishing this part has been put on hold because our many current research collaborations involving ab initio and DFT-based quantum chemistry simulations are providing so much new information that we think it’s better to wait and incorporate this new material into the book.  (Otherwise we could’ve published DSDM in 2005.)  Until then, I’ve put together a brief technical bibliography of research on positional mechanosynthesis (including diamond).  Watch the Molecular Assembler website for updates and further news about DSDM.

Question 5: Tell us about your latest book, Kinematic Self-Replicating Machines.  Was this book written with the specific aim of convincing skeptics of the feasibility of molecular manufacturing?

Yes it was, though of course the subject of self-replicating machines has been a long-standing professional interest of mine, across 3 decades.  For instance, I published the first quantitative closure analysis for a self-replicating machine system in 1979-1980 and participated in (and edited) the first comprehensive technical analysis of a self-replicating lunar factory for NASA in 1980.

But focusing again on molecular manufacturing:  Once diamond mechanosynthesis and the fabrication of nanoparts becomes feasible, we will also need a massively parallel molecular manufacturing capability in order to assemble nanorobots cheaply, precisely, and in vast quantities.  Kinematic Self-Replicating Machines (KSRM) (Landes Bioscience, 2004, and freely available online), co-authored with Ralph Merkle, surveys all known current work in the field of self-replication and replicative manufacturing, including all known concepts of molecular assemblers and nanofactories.  It is intended as a general introduction to the systems-level analysis of self-replicative manufacturing machinery.  With 200+ illustrations and 3200+ literature references, KSRM describes all proposed and experimentally realized self-replicating systems that were publicly disclosed as of 2004, ranging from nanoscale to macroscale systems.  The book extensively describes the historical development of the field.  It presents for the first time a detailed 137-dimensional map of the entire kinematic replicator design space to assist future engineering efforts.  It includes a primer on the mathematics of self-replication, and has an extensive discussion of safety issues and implementation issues related to molecular assemblers and nanofactories.  KSRM has been cited in two articles appearing in Nature this year (Zykov et al, Nature 435, 163 (12 May 2005) and Griffith et al, Nature 437, 636 (29 September 2005)) and appears well on its way to becoming the classic reference in this field.

Perhaps the most salutary effect of KSRM is that it provides a number of physical examples of self-replicating systems (beyond the relatively simple autocatalytic-type replicators from the 1950s by Penrose, Jacobson and Morowitz and the more recent related examples by Lohn and Griffith) that have already been built and operated in a laboratory environment.  This provides a ready answer to the tedious and recurring objection by the ill-informed that such things are “impossible”:  The machines have actually been built.  Interestingly, one of these experimental replicators is a fully autonomous machine that runs around on a table and procures its own parts, which it then assembles into a working copy of itself, a crude analog of the molecular assembler approach.  Another of these experimental replicators is a computer-controlled manipulator arm anchored to a surface, that grabs its parts from a “warehouse” area and assembles these parts into a working copy of itself, a crude analog of the nanofactory approach (where the nanofactories are being used to make more nanofactories, rather than non-factory product).

Question 6: You and Dr. Hall are working on Fundamentals of Nanomechanical Engineering.  Is this book intended to serve as a guide book for college students hoping to enter the nanotechnology field?

Fundamentals will be sharply focused on nanomechanical design, with a concentration on diamondoid molecular machine systems, intended for use in a mechanical engineering curriculum at the 2nd- or 3rd-year undergraduate level.  We hope the book will be widely used in nanotechnology courses and will help to train the first generation of nanomechanical design engineers.

This is the primary purpose of the book.  A second purpose is to extend and complement the analyses already published in Drexler’s Nanosystems, providing more design details and engineering analysis of how to build structures with molecular precision, and understanding how molecular machines might function (and the limitations on them).  Once an experimental ability to build diamondoid gears, bearings, rods, and the like has been demonstrated in the laboratory, I think the development of nanorobotics will move very rapidly from that point, because the potential payoff to human welfare is so large and the design space will have become accessible to active experimentation.

Question 7: MIT granted Eric Drexler a PhD in molecular nanotechnology.  How long do you estimate before other universities offer undergraduate and graduate degrees in molecular nanotechnology?

If you mean college degrees in MNT, in the sense of diamondoid molecular machine systems, I think this will begin to occur as soon as the field gains scientific credibility – i.e., as soon as it becomes clear that there is a “there”, there.  The key here, in my opinion, will be the first experimental demonstration of positionally controlled diamond mechanosynthesis in the laboratory.  Once this has been done, it will no longer be possible for critics to deny that such a thing is possible, though they still may claim that perhaps such a thing is not very useful for anything important.  But with the newfound ability to tinker with real atoms, I expect legions of graduate students to rise up and prove the critics wrong on that score too, and the results of this revolution will rapidly trickle down to the undergraduate level as well.

How long until the first simple experimental demonstration of positionally controlled diamond mechanosynthesis in the laboratory?  Perhaps not as far off as you might think.  I’d be shocked if it was longer than ten years, and five years would not surprise me.  It depends on how fast we’re able to push it forward.

Question 8:  You are a scientific advisor to the startup nanotechnology company Nanorex.  What role do you anticipate that Nanorex will play in the development of nanotechnology?  What is your contribution to that company?

Nanorex is creating an incredibly cool piece of software called NanoEngineer that allows the user to quickly and easily design molecular machine systems of up to perhaps 100,000 atoms in size, then perform various computational simulations on the system such as energy minimization (geometry optimization) or a quantitative analysis of applied forces and torques.  It’s a CAD system for molecules, with a special competence in the area of diamondoid structures.  Once this software is released, users anywhere in the world will be able to begin creating designs for relatively complex nanomachine components.  We’d expect the library of designed machine systems to rapidly expand from the current 1-2 dozen items (including mostly just a few bearings, gears, and joints) into the hundreds or thousands in just a few years.  The existence of this expanded library of nanoparts will then make it easier to begin thinking about designs for more complex systems that may be built from thousands or more of these parts, containing millions or even billions of atoms.  It’s a big step along the molecular machine design and development pathway.

I’m a member of the Scientific Advisory Board of Nanorex.  The Board provides feedback in the development of the NanoEngineer software, especially including our respective “wish lists” of what the ideal molecular machine design package should include – most of which features were then incorporated into the software.  Thus the new software reflects the collective experience of those few of us in the world who have ever actually designed a molecular machine component the hard way – laboriously, atom by atom, using some previously existing (inadequate) software package.

Nanorex is also directly supporting the writing of Fundamentals of Nanomechanical Engineering, which we hope will be used to train the first generation of serious nanomechanical design engineers.

Question 9:  Is the mainstream scientific establishment’s assessment of the feasibility of molecular nanotechnology changing?  It appears that the National Nanotechnology  Initiative’s long term forecasts have become bolder, yet the standard response by Smalley and others is that molecular manufacturing is inherently unworkable.

I think this feasibility assessment may be slowly changing, but this change is probably being driven mainly by published experimental results, especially in the field of STM/AFM(scanning probe)-moderated single-atom chemistry.  For example, the first experimental demonstration of pure mechanosynthesis of any kind was reported in 2003 and is just now becoming more widely known.  Publication of credible high-accuracy theoretical results, demonstrating the feasibility of diamond mechanosynthesis, will also help change this assessment.  (For instance, in 2006 Merkle and I will be publishing a key theoretical paper in diamond mechanosynthesis representing ~10,000 CPU-hours of quantum chemistry simulations on 2600+ molecular structures to elucidate possible reaction pathways for building diamond.  Watch for it.)

Smalley has marginalized himself in this area by taking such an extreme and indefensible position, using fallacious arguments.  One by one, his arguments are slowly melting away under the hot glare of brilliant (but hard-won) experimental results.

Question 10: The Foresight Institute is collaborating with Battelle to create a nanotechnology roadmap.  What do you know about this roadmap?  Will it affect the mainstream scientific community’s assessment of molecular manufacturing?

Actually, I don’t know anything about their roadmap.  They haven’t consulted me at all on this, and I have no idea what they’re up to except what I “read in the newspaper”.  I believe it is an attempt to involve mainstream players in an assessment of possible development pathways leading toward some flavor(s) of molecular manufacturing.  Whether these flavor(s) will include some or all of biological systems, protein systems, polymer systems, MEMS systems, metal systems, diamondoid systems, or something else, I cannot say.

Meanwhile, over the last two years Ralph Merkle and I have worked hard to establish a small independent network of research (both theoretical and experimental) collaborators with a sharp focus on the implementation of diamondoid molecular machine systems.  Last June we put together a simple draft implementation flowchart that has about 100 boxes and lots of arrows, that starts from where we are today and ends with the manufacturing of complex molecular machine systems, including simple nanorobots.  The plan includes specific theoretical and experimental milestones in a particular sequence.  So we’re in the process of simplifying (and implementing) our own “roadmap”.  Perhaps this (or something like it) will eventually be incorporated in the broader Foresight nanotechnology roadmap.  Watch the Molecular Assembler website for more details in the months ahead.

Question 11: Let's turn to nanomedicine. How far can simple genetic engineering go towards curing diseases? Does pre-MNT technology have the potential to cure cancer and regrow organs?

Yes, of course.  Genetic engineering is a very powerful technology.  Pre-nanotechnology treatments for some forms of cancer already exist.  The emerging discipline of tissue engineering is already heading in the direction of building tissues and organs using special scaffolds that are impregnated with appropriate cells which grow into the matrix to form cohesive new tissues.  Single-organ cloning is also on the horizon.  But all of these treatments and organ substitutions could be accomplished with greater reliability, executed with greater speed, and completed in a side-effect free manner, using the tools of nanorobotic medicine.  There are also many kinds of treatments, particularly those related to physical trauma, that can only be dealt with efficiently using advanced nanorobotic medicine.

The way I like to think about all this is to recognize that “nanomedicine” is most simply and generally defined as the preservation and improvement of human health, using molecular tools and molecular knowledge of the human body.  Nanomedicine involves the use of three conceptual classes of molecularly precise structures:  nonbiological nanomaterials and nanoparticles, biotechnology-based materials and devices, and nonbiological devices including nanorobotics.

In the near term, say, the next 5 years, the molecular tools of nanomedicine will include biologically active materials with well-defined nanoscale structures, including those produced by the methods of genetic engineering.  For example, one of the first uses of “nanotechnology” in treating cancer employs engineered nanoparticles of various kinds to attempt a general cure while staying within the usual drug-treatment paradigm.  Kopelman’s group at the University of Michigan has developed dye-tagged nanoparticles that can be inserted into living cells as biosensors.  This quickly led to nanomaterials incorporating a variety of plug-in modules, creating molecular nanodevices for the early detection and therapy of brain cancer.  One type of particle is attached to a cancer cell antibody that adheres to cancer cells, and is also affixed with a contrast agent to make the particle highly visible during MRI, while also enhancing the selective cancer-killing effect during subsequent laser irradiation of the treated brain tissue.

Another example from the University of Michigan is the dendrimers, tree-shaped synthetic molecules with a regular branching structure emanating outward from a core.  The outermost layer can be functionalized with other useful molecules such as genetic therapy agents, decoys for viruses, or anti-HIV agents.  The next step is to create dendrimer cluster agents, multi-component nanodevices called tecto-dendrimers built up from a number of single-dendrimer modules.  These modules perform specialized functions such as diseased cell recognition, diagnosis of disease state, therapeutic drug delivery, location reporting, and therapy outcome reporting.  The framework can be customized to fight a particular cancer simply by substituting any one of many possible distinct cancer recognition or “targeting” dendrimers.  The larger trend in medical nanomaterials is to migrate from single-function molecules to multi-module entities that can do many things, but only at certain times or under certain conditions – exemplifying a continuing, and, in my view, inevitable, technological evolution toward a device-oriented nanomedicine.

In the mid-term, the next 5 or 10 years or so, knowledge gained from genomics and proteomics will make possible new treatments tailored to specific individuals, new drugs targeting pathogens whose genomes have now been decoded, and stem cell treatments to repair damaged tissue, replace missing function, or slow aging.  We will see genetic therapies and tissue engineering, and many other offshoots of biotechnology, becoming more common in medical practice.  We should also see artificial organic devices that incorporate biological motors or self-assembled DNA-based structures for a variety of useful medical purposes.  And we’ll also see biological robots, derived from bacteria or other motile cells that have had their genomes re-engineered and re-programmed.

So yes, there is a lot that pre-nanotechnology, or, more properly, pre-nanorobotic medicine can do to improve human health.  But the advent of medical nanorobotics will represent a huge leap forward.

Question 12:  Are there any diseases that can’t be cured by nanotechnology?  Are there any aspects of ageing that can’t be stopped by nanotechnology?

If we combine the benefits of a human physiology maintained at the level of effectiveness possessed by our bodies when we were children (e.g., dechronification), along with the ability to deal with almost any form of severe trauma (via nanosurgery), then there are very few diseases or conditions that cannot be cured using nanomedicine.  The only major class of incurable illness which nanorobots can’t handle is the case of brain damage in which portions of your brain have been physically destroyed.  This condition might not be reversible if unique information has been irrevocably lost (say, because you neglected to make a backup copy of this information).  There are several other minor “incurable” conditions, but all of these similarly relate to the loss of unique information.

Question 13:  The Foresight community has deemphasized molecular assemblers in favor of a desktop manufacturing paradigm.  How will medical nanorobots be constructed?

As noted above, my view is that this change of emphasis is unlikely to affect the conduct of research in the field, or the activities of those few of us who are actually doing the research involved, because the distinction between “molecular assemblers” and “nanofactories” is largely cosmetic and because both approaches require almost exactly the same set of enabling technologies.  At present we’re concentrating our efforts mostly on developing these component enabling technologies, not on integration of these technologies into larger systems.  Systems analysis will come next.

Medical nanorobots small enough to go into the human bloodstream will be very complex machines.  We don’t know exactly how to build them yet, but the overall pathway from here to there is slowly starting to come into focus.  Building and deploying nanorobotic systems will require first the ability to build diamondoid structures to molecular precision, using atomic force microscopy or similar means along with the techniques of diamond mechanosynthesis.  My early work on diamond mechanosynthesis is described in a lecture I gave at the 2004 Foresight Conference in Washington DC, the text of which (plus many images) is available online.  I’m currently involved in 6 collaborations with university groups in the U.S, U.K. and Russia (including both theoretical and experimental efforts) to push forward the technology in this area, and I have several new papers nearing completion for journal submission very soon on this work.

This must be followed by developing the ability to design and manufacture rigid machine parts and then to assemble them into larger machine systems, up to and including nanorobots.  My forthcoming book with Josh Hall (Fundamentals of Nanomechanical Engineering) and the development of the NanoEngineer software by Nanorex should advance our ability to design nanomechanical components, and further simulations and experiments will be required to learn how to build these systems and then assemble them into larger structures.

Once diamond mechanosynthesis and the fabrication of nanoparts becomes feasible, we will also need a massively parallel manufacturing capability to assemble nanorobots cheaply, precisely, and in vast quantities.  My recently published technical book, co-authored with Merkle and titled Kinematic Self-Replicating Machines (Landes Bioscience, 2004), surveys all known current work in the field of self-replication and replicative manufacturing, including concepts of molecular assemblers and nanofactories.  (This book is freely available online at the Molecular Assembler website.)

Finally, the reliable mass-production of medical nanorobots must be followed by a period of testing and approval for biocompatibility and safety by the FDA or its equivalent in other countries.  I would not be surprised if the first deployment of such systems occurred during the 2020s.  But until we can build these devices experimentally, we are limited to theoretical analyses and computational chemistry simulations (some of which are now so good that their accuracy rivals the results of actual experiments).

So we can take two approaches, both of which I’m pursuing.  First, we can use our knowledge of the laws of physics and the principles of good engineering to create exemplar designs of nanorobots, and to analyze potential capabilities and uses of these devices, and determine which applications are likely to be possible and which seem not to be feasible.  This helps to establish a clear long-term goal.  Second, we can examine the implementation pathways that could lead from where we are today to the future time when we may be able to build nanorobotic devices.  As noted above, this may require diamond mechanosynthesis and massively parallel nanofabrication capabilities.  Earlier this year I submitted the first-ever U.S. patent on diamond mechanosynthesis that describes one possible specific experimental process for achieving molecularly precise diamond structures in a practical way.

Question 14:   How will nanorobots avoid being destroyed by our immune systems?  Won’t our immune systems identify them as foreign organisms and immediately attack them?

Nanorobots constructed of diamondoid materials cannot be destroyed by our immune system.  They can be made to be essentially impervious to chemical attack.  However, the body may react to their presence in a way that may interfere with their function.  This raises the issue of nanorobot biocompatibility.

The biocompatibility of medical nanorobots is a complex and important issue.  That’s why I expanded my original discussion in the Nanomedicine book series from a single chapter (Chapter 15, Nanomedicine Vol. II) to an entire book-length treatment (Nanomedicine, Vol. IIA) (NMIIA).  My exploration of the particular problem you raise, nanorobot immunoreactivity, spans 16 pages in NMIIA.  There is not enough space here to go into details, so interested readers should refer to that extended discussion.  The short answer to your question is that the immune system invokes several different responses to foreign objects placed within the body, including complement activation and antibody response.  Phagocytosis and foreign-body granulomatous reaction are additional major immune system issues for medical nanorobots intended to remain in the body for extended durations.  The NMIIA book discusses all of these issues and suggests numerous methods by which antigenic reactions to nanorobots can be prevented or avoided, including (but not limited to) camouflage, chemical inhibition, decoys, active neutralization, tolerization, and clonal deletion.  NMIIA also has an extensive discussion of nanorobotic phagocytosis, including details of all steps in the phagocytic process and possible techniques for phagocyte avoidance and escape by medical nanorobots.  To summarize:  the problems appear arduous but surmountable with good design.

Question 15:  Ray Kurzweil has proposed having billions of nanorobots positioned in our brains, in order to create full-immersion virtual reality.  Do you think that such a scenario will ever be feasible?

Yes of course.  I first described the foundational concepts necessary for this in Nanomedicine, Vol. I (1999), including noninvasive neuroelectric monitoring (i.e., nanorobots monitoring neuroelectric signal traffic without being resident inside the neuron cell body, using >5 different methods), neural macrosensing (i.e., nanorobots eavesdropping on the body’s sensory traffic, including auditory and optic nerve taps), modification of natural cellular message traffic by nanorobots stationed nearby (including signal amplification, suppression, replacement, and linkage of previously disparate neural signal sources), inmessaging from neurons (nanorobots receiving signals from the neural traffic), outmessaging to neurons (nanorobots inserting signals into the neural traffic), direct stimulation of somesthetic, kinesthetic, auditory, gustatory, auditory, and ocular sensory nerves (including ganglionic stimulation and direct photoreceptor stimulation) by nanorobots, and the many neuron biocompatibility issues related to nanorobots in the brain, with special attention to the blood-brain barrier.

The key issue for enabling full-immersion reality is obtaining the necessary bandwidth inside the body, which should be available using the in vivo fiber network I first proposed in Nanomedicine, Vol. I (1999).  Such a network can handle 10¹⁸ bits/sec of data traffic, capacious enough for real-time brain-state monitoring.  The fiber network has a 30 cm³ volume and generates 4-6 watts waste heat, both small enough for safe installation in a 1400 cm³ 25-watt human brain.  Signals travel at most a few meters at nearly the speed of light, so transit time from signal origination at neuron sites inside the brain to the external computer system mediating the upload are ~0.00001 millisec which is considerably less than the minimum ~5 millisec neuron discharge cycle time.  Neuron-monitoring chemical sensors located on average ~2 microns apart can capture relevant chemical events occurring within a ~5 millisec time window, since this is the approximate diffusion time for, say, a small neuropeptide across a 2-micron distance.  Thus human brain state monitoring can probably be “instantaneous”, at least on the timescale of human neural response, in the sense of “nothing of significance was missed. 

I believe Ray was relying upon these earlier analyses, among others, when making his proposals.

Question 16: What is your best guess regarding the development of advanced medical nanotechnology?  Will it appear within a decade of the first desktop assembler?

The availability of practical molecular manufacturing is an obvious and necessary precursor to the widespread use of medical nanorobotics.  I would not be surprised if the 2020’s are eventually dubbed the “Decade of Medical Nanorobots.”

Question 17:  Will nanorobots be able to eradicate all infectious disease?  After all, bacteria and viruses are extremely adaptable, and have developed a plethora of effective techniques to thwart the immune system.

It will probably not be possible to eradicate all infectious disease.  The current bacterial population of Earth may be ~10³¹ organisms and so the chances are good that most of them are going to survive in some host reservoir, somewhere on the planet, for as long as life exists here, despite our best efforts to eradicate them.  However, it should be possible to eliminate all harmful effects, and all harmful natural disease organisms, from the human body, allowing us to lead lives that are free of pathogen-mediated illness (at least most of the time).  A simple antimicrobial nanorobot like the microbivore should be able to eliminate even the most severe bloodborne infections in treatment times on the order of an hour;  more sophisticated devices could be used to tackle more difficult infection scenarios.

Regarding microbial adaptability, it makes no difference if a bacterium has acquired multiple drug resistance to antibiotics or to any other traditional treatment – the microbivore will eat it anyway, achieving complete clearance of even the most severe septicemic infections in minutes to hours, as compared to weeks or even months for antibiotic-assisted natural phagocytic defenses, without increasing the risk of sepsis or septic shock.  Hence microbivores, each 2-3 microns in size, appear to be up to ~1000 times faster-acting than either unaided natural or antibiotic-assisted biological phagocytic defenses, and can extend the doctor’s reach to the entire range of potential bacterial threats, including locally dense infections.

Question 18:  Have you made any detailed, molecularly precise simulations of medical nanorobots?

The greatest power of nanomedicine will emerge in a decade or two as we learn to design and construct complete artificial nanorobots using diamondoid nanometer-scale parts and subsystems including sensors, motors, manipulators, power plants, and molecular computers.  The development pathway will be lengthy and difficult.  First, theoretical scaling studies must be used to assess basic concept feasibility.  These initial studies would then be followed by more detailed computational simulations of specific nanorobot components and assemblies, and ultimately full systems simulations, all thoroughly integrated with additional simulations of massively parallel manufacturing processes from start to finish consistent with a design-for-assembly engineering philosophy.  Once molecular manufacturing capabilities become available, experimental efforts may progress from component fabrication and testing, to component assembly, and finally to prototypes and mass manufacture, ultimately leading to clinical trials.

As of 2005, progress in medical nanorobotics remains largely at the concept feasibility stage – since 1998, the author has published four theoretical nanorobot scaling studies, including the respirocytes (artificial red cells), microbivores (artificial white cells), clottocytes (artificial platelets), and the vasculoid (an artificial vascular system).  These studies have not been intended to yield an actual engineering design for a future nanomedical product.  Rather, the purpose was merely to examine a set of appropriate design constraints, scaling issues, and reference designs to assess whether or not the core idea might be feasible, and to determine key limitations of such designs.

The basic diamondoid structure of the respirocyte, the simplest nanorobot designed to date, includes 18 billion atoms.  Molecular mechanics simulations of systems including 10-40 billion atoms have recently been reported using cluster supercomputers.  So it is now possible, at least in principle, to attempt a basic simulation of an entire working medical nanorobot.  The problems with actually doing this are many, and include the lack of a detailed atomic-level description of the respirocyte, a lack of reliable nanopart designs for components comprising the respirocyte, the difficulties of preparing input files and running massive simulations, and access to the personnel and computer time necessary to run the simulation.  Such a simulation might well be attempted sometime in the next 5-10 years.  Meanwhile we must content ourselves with molecular mechanics simulations of molecularly precise nanocomponents, starting with structures of up to 100,000 atoms using, for instance, the new NanoEngineer software produced by Nanorex.

Question 19:  How has the mainstream medical community reacted to your research? 

I think the biggest impact so far has been in solidifying the long-term vision of where the technology can go.  Typically articles describing future medicine, especially nanotechnology-based medicine, will lead off with a mention of “nanorobots in the bloodstream” as an idea that lies out there somewhere in the distant future, before moving on to a more substantive discussion of the latest news in medical nanoparticle research.  This is entirely understandable and logical.  Doctors are faced with the immediacy of sick or dying patients, and can only employ the instruments at their command today.  Realistically, there will only be some small fraction of the traditional medical community that “gets it” right off the bat.  The intended audience of my Nanomedicine book series is technical and professional people who are seriously interested in the future of medical technology.  Many practicing physicians do not – and quite correctly should not – fit this description.  But I know I’m having an impact.  I’ve received dozens of emails from students and young researchers thanking me for inspiring them to consider new career directions.  (I’ve also been told, only partly tongue-in-cheek, that my Nanomedicine books are often used by postdocs to help prepare their grant proposals because of all the relevant literature references collected in each volume.)

As medical nanorobotics proceeds along the development pathway I’ve outlined above – moving from drawing board, to computer simulation, to laboratory demonstration of mechanosynthesis, to component design and fabrication, to parts assembly and integration, and finally to device performance and safety testing – members of the mainstream medical community will naturally pay increasing attention to it, because it will become more directly relevant to them.  By mid-century, medical nanorobotics will completely dominate medical practice.  By writing the Nanomedicine book series, KSRM, and the rest, I hope to accelerate the process of technological development and adoption of nanorobotics in modern medicine.  To this end, the Nanomedicine book series and my other books are being made freely available online, with the generous consent of my publisher, Landes Bioscience.  Such generosity is still almost unheard of among conventional book publishers.  The main reason we’re doing this is to promote a broader discussion of the technical issues and a rapid assessment of the possibilities by the worldwide biomedical and engineering community.

Question 20:  How far along are you in writing your Nanomedicine book series?  What else have you been up to lately, in the nanomedicine area?

I’ve been writing the Nanomedicine book series since 1994.  It was originally conceived as a single book, then became a trilogy until I realized I needed an entire volume devoted solely to biocompatibility, whereupon it became a tetralogy.  Volume I was published by Landes Bioscience in 1999 and Volume IIA came out in 2003, also published by Landes Bioscience.  I’m still writing the last 2 volumes (NMIIB, NMIII) of this book series, an ongoing effort that will continue during 2005-2010.  Earlier this year I published two reviews on the current status of nanomedicine, available online at http://www.nanomedicine.com/Papers/WhatIsNMMar05.pdf and http://www.nanomedicine.com/Papers/NMRevMar05.pdf.  The first of these papers was the leadoff article for the premier issue of the new journal Nanomedicine (the first journal exclusively devoted to this field, published by Elsevier), on whose Editorial Board I also serve.

In a recent major collaborative effort, artist Gina Miller has finished work on a 3-minute long animation that nicely illustrates the workings of my proposed programmable dermal display (essentially, a video-touchscreen nano-tattoo that reports real-time medical information to the user, as reported back by numerous nanorobots stationed in various locations inside the body).  I think this is a very cool animation.  And of course you can always visit my Nanomedicine Art Gallery (hosted for me by Foresight Institute) with all the nice nanorobot images, where I continue on as curator.