Making and doing

Eric Drexler is quoted in Adam Keiper’s report from the NRC nanotechnology workshop in DC as saying:

“What’s on my wish list: … A clear endorsement of the idea that molecular machine systems that make things … with atomic precision is a natural and important goal for the development of nanoscale technologies … with the focus of that endorsement being the recognition that we can look at biology, and beyond…. It would be good to have more minds, more critical thought, more innovation, applied in those directions.”

I almost completely agree with this, particularly the bit about looking at biology and beyond. Why only almost?. Because “systems that make things” should only be a small part of the story. We need systems that do things – we need to process energy, process information, and, in the vital area of nanomedicine, interact with the cells that make up humans and their molecular components. This makes a big difference to the materials we choose to work with. Leaving aside, for the moment, the question of whether Drexler’s vision of diamondoid-based nanotechnology can be make to work at all, let’s ask the question, why diamond? It’s easy to see why you would want to use diamond for structural applications, as it is strong and stiff. But its bandgap is too big for optoelectronic applications (like solar cells) and its use in medicine will be limited by the fact that it probably isn’t that biocompatible.

In the very interesting audio clip that Adam Keiper posts on Howard Lovy’s Nanobot, Drexler goes on to compare the potential of universal, general purpose manufacture with that of general purpose computing. Who would have thought, he asks (I paraphrase from memory here), that we could have one machine that we can use to do spreadsheets, play our music and watch movies on? Who indeed? … but this technology depends on the fact that documents, music and moving pictures can all be represented by 1’s and 0’s. For the idea of general purpose manufacturing to be convincing, one would need to believe that there was an analogous way in which all material things could be represented by a simple low level code. I think this leads to an insoluble dilemma – the need to find simple low level operations drives one to use a minimum number – preferably one – basic mechanosynthesis step. But in limiting ourselves in this way, we make life very difficult for ourselves in trying to achieve the broad range of functions and actions that we are going to want these artefacts for. Material properties are multidimensional, and it’s difficult to believe that one material can meet all our needs.

Matter is not digital.

12 thoughts on “Making and doing”

  1. Well, matter isn’t a simple binary state such as digital computing deals with, true.

    However, how different is diamond and buckytube? They’re both carbon, they’re both covalently bonded. While I don’t have a study to point to (sorry to beat you to the punch, Philip *grin*) I’d have to wonder if tools similiar to those proposed for diamondoid construction might not be usable to produce buckytube.

    And buckytube can either conduct electricity or act as a transistor, depending on the degree of chirality. There’s your electronics capability.

    It can be used in solar panels without doping. And there’s where you could get power for those electronics, as well as optoelectronic capabilities.

    As for biocompatibility, I don’t know enough about the problems to comment. *shrug*


  2. You can use fullerenes to make solar cells, but for this purpose, as materials with a high electron affinity, they need to be blended with a good hole conductor, typically a semiconducting polymer. And given recent reports about their toxicity, they are going to need to be heavily functionalised before you can use them for medical devices. But this is besides the main point; both fullerenes and diamond have many virtues as materials but the very varied properties we require for all the devices and materials with their different functions that we need mean that, in my view, it’s unrealistic to expect that any single material will do the job.

  3. Richard,
    I can certainly accept that you can add capabilities by moving beyond just carbon and hydrogen atoms. The elements in the rest of the periodic table have many many uses. But, diamond and graphite are extremely complementary in many properties. (3-D solid vs 2-D plane, Transparent to visible light vs absorbs visible light, rigid vs flexible, insulator vs directional conductor, or in other words sp-3 vs sp-2) With structural, mechanical, electrical and optical properties that are very impressive, diamond and graphite give you a very rich design space for making artifacts. So, I see a huge value in focusing on those two forms of carbon.

    Although, I would like to see the MNT community open a second front in the quest for a nano-factory. A real coordinated push to extend the capabilities of 3-D fabrication systems. It would play on the strengths within the community; computer science, design, system architecture. The right kind of fabrication system could dovetail in with a lot of bio-tech, soft nano-tech, inorganic nano-tech, and diamond / graphite nano-tech. If we stick the what seems to be the dominate metaphor (printing) for spanning the gap between the nano-world and our everyday world, we should simultaneously work on making more capable printers and better inks at the same time.

  4. Endless debating apart, a consortium of EU scientist and a company called ProtoLife will assemble programmable artificial cells from scratch, creating life under the control of current computers. I think the main thing here is “programmable.” If this is achived, then we can further program it to build more sophisticated machinery, ultimately a nanofactory. According to them ,such artificial cells will be “useful because of their distinctness from, rather than similarity to current biology”–which certainly sounds reasonable, cause “anything goes” will be a safe strategy. I think the way to go forward would be to try things out like these bold attempts.

  5. Anonymous, I agree absolutely with you that the way to go is to design and make something that looks in some way like artificial life. In fact, that’s one of the major themes of my book “Soft Machines”, and that’s the idea that underlies what we are trying to do in my own laboratory, where we are combining systems which self-assemble, molecules which change shape according to their environment and the non-linear chemical kinetics of oscillating chemical reactions to duplicate (in a very crude way, of course) some of the functions of living organisms.

    Jim, I think what you suggest is already to some extent being done (judging by the meeting I had yesterday with scientists from one of the world’s largest manufacturers of printing inks).

  6. Just for full disclosure, I work for a very large ink company myself, and I will hopefully be moving to a new job doing development in our energy curable ink jetting group. I am not aware that we are doing any 3-D fabrication work yet, but hopefully that will change soon.


  7. Jim, I’d better be careful what I say then! Though it’s not at all impossible that the companies we are talking about are one and the same. In any case, I think any company with a good technology base in the very low margin world of printing inks is going to be looking pretty seriously at whether they can get some new high added value businesses from these sorts of ideas.

  8. Richard,
    Here is a bit more detail on the fabrication system I have in mind.

    Laminate Ink Jetting Fabrication,
    How Top – Down and Bottom – Up fabrication techniques can meet to form artifacts that are structured from nanometers to meters.

    The purpose of this post is to outline an approach for the creation of computer controlled, general purpose, fabrication systems. The fabrication system can;
    1.) handle a wide variety of materials,
    2.) be fast enough to make large, complex artifacts in less than a day
    3.) use off the shelf techniques that can be refined to give greater precision and wider capabilities.

    The general process is straight forward, yet flexible.
    a.) You start with a substrate that has a uniform length and width.
    b.) The substrate is passed under a series of ink jetting stations which produce a pattern of ink on the substrate.
    c.) The printed substrate is moved and stacked upon the previously printed layer.
    d.) The top layer is bonded to the layer underneath.
    e.) Excess substrate is removed.

    This system uses an additive process (layering of the ink jetted patterns) to make the artifact and a subtractive process (the removal of excess substrate) to simplify the handling of each layer.

    Material diversity can come from both the substrate and the ink. The substrate could be made from a wide variety of materials; e.g. metal foil, plastic sheet, paper, woven bucky tube mesh, etc. The inks can range from a simple, single component liquid (DPDGA monomer) to a very complex multi component mixture ( water, long chain functionalized polymer, DNA coated nano-particles) The final artifact could be made of ~ 1-10 different substrates and ~ 5 -100 different inks. (*note* you must make sure that the ink is compatible with the substrate that it is printed on.)

    Commercial ink jetting systems run at speeds from ~ 30 – 300 meters per minute. If each layer was 10 cm by 10 cm one printing station would be able to print ~400 thousand to ~4 million layers in a day. If stacking, and bonding the layers together takes 1 second you could stack ~80,thousand layers in a day. Cutting and removing the excess substrate will probably be the rate limiting step. Lets assume that you use a laser to cut away the excess substrate and that it takes 5 seconds to print, stack, bond, and cut a layer you could fabricate an artifact with ~13,000 layers in a day. If each layer was 10 microns thick it would take less than a day to make an artifact that would fill a 10 x 10 x 10 centimeter cube.

    Although the thinness of your substrate, the size of ink droplets and the precision of placement of the ink is all measured in the micron range, smaller levels of organization can be obtained from pre-patterning of the substrate, adding nano-structured particles to the ink, and using methods of self-assembly.

    The type of system described here could be constructed today, yet this general set up can accommodate a great deal of technological evolution in the substrates and inks. For example, make the substrate out of a 2-D weave of fibers that have a pattern of different chemical groups along their length. Then ink jet out simple particles, complex objects or cells that will bind to a specific chemical group on the fiber.

  9. I can definitely see this working for heterogeneus solids, along the lines of computer chips and the like, but I don’t see how it’d work to make objects with voids/unbonded seams within them, such as motors, gears, etc. Unless you plan on one or more of the layers being effectively a ‘lubricant’ held in place by the solid materials around it?


Comments are closed.