Drexler has some comments about nanotechnology development, progress in nanotechnology and development pathways.
Note : Eric Drexler reminded me that he no longer has any connection with the Foresight Institute and asked that I split the original post to avoid confusion.
Molecular nanotechnology/nanofactories will not be developed in a basement. The implementation problems will involve complex devices and extensive laboratory facilities, they will be most effectively addressed by large teams of diverse and well-funded specialists.
Another idea that should be dropped, the idea of a direct leap from accessible, starting-point technologies to the most advanced technologies that have been discussed.
Problems of perception and organization are the chief obstacles to more rapid progress in developing molecular machine technologies on the critical path to fulfilling the promise that launched the field of nanotechnology.
Available technologies now enable the design and fabrication of intricate, atomically precise nanometer-scale objects made from a versatile engineering polymer, together with intricate, atomically precise, 100-nanometer scale frameworks that can be used to organize these objects to form larger 3D structures. These components can and have been designed to undergo spontaneous, atomically precise self assembly. Together, they provide an increasingly powerful means for organizing atomically precise structures of million-atom size, with the potential of incorporating an even wider range of functional components.
The nanometer-scale objects that I mentioned above have nylon-like backbones that link and organize an extraordinarily diverse set of molecular components to form structural elements, electronic devices, and machines. The problem is that because they are traditionally called “protein molecules” their nature is obscured by a powerful association with food. The frameworks have a similar representativeness-heuristic problem: “DNA” makes one think of genetic information in cells, but structural DNA nanotechnology uses it as a construction material.
We now have in hand the engineering materials for a new, breakthrough class of nanosystems, yet the bug in our minds whispers “meat” and “genes”. And even in more sophisticated minds, the biological origin of the these materials encourages the seductive idea that their engineering is a task that can be left to biologists. Developing complex, functional systems, however, is quite unlike studying complex, functional systems that already exist. In science, nature provides the pattern. In engineering, human beings provide the pattern. The difference in tasks and mindsets is profound.
Researchers working at Caltech and IBM have taken the first steps toward combining nanosystems [nanolithography, quantum dots, carbon nanotubes, DNA nanotechnology, self assembly etc…] of this kind with nanoscale circuitry to produce a new class of digital devices
The productive nanosystems I refer to above are, of course, ribosomes and nucleic acid polymerases, the programmable molecular machines that assemble polypeptide and polynucleotide chains. In making these polymers, productive nanosystems assemble monomers of different kinds in sequences specified by information encoded in the sequences of (other) polynucleotides, and these sequences determine how, for example, a foldamer product will fold and the functions that the resulting component can perform.
Advances along these lines can support the development of artificial productive nanosystems that are specialized to produce complex, atomically precise components of new kinds. The most accessible advances in this direction would be devices that expand the range of available foldamers. Clever exploitation of existing productive nanosystems has already expanded the range of products by enabling the use of a wider range of monomeric building blocks; new productive nanosystems could add the ability to build foldamers of wholly new kinds that offer (for example) stiffer backbones and greater chemical and physical stability.
The productive nanosystems in use today can operate only in aqueous environments, and their products are usually (but not always) used under the same conditions. I expect that next-generation productive nanosystems built from components of this sort will also be constrained to operate in aqueous environments. For chemical reasons, the presence of water limits the range of fabrication operations that these devices can perform, but these constraints allow more than one might suppose. Within the scope are not only novel foldamers and highly cross-linked 2D and 3D polymeric nanostructures, but also high-modulus inorganic solids, such as metal oxides and pyrite. Even metals and semiconductors are within the scope of aqueous synthesis.
The ability to make better and more robust components will, of course, enable the fabrication of better and more robust products, including better and more robust productive nanosystems that are not constrained to operate in aqueous environments. And these, of course, will provide means for working with a wider range of materials, enabling the production of components and systems that are even better. The expanded scope of component fabrication can be applied to improve Brownian assembly, but constrained Brownian assembly will become more practical and desirable as fabrication technologies advance.
Note that graphenes, carbon nanotubes, and related structures are locally 2D, and can be regarded as extreme cases of “highly cross-linked polymeric nanostructures”. The useful electronic and mechanical properties of these materials are legendary, and they also work well as low-friction nanoscale moving parts. With the aid of nanoscale arrays of catalytic particles, materials of this class have been synthesized at room temperature.
Beyond Ribosome Level Complexity
A productive nanosystem can build chains by controlling positions in just one dimension, extending a 1D chain by adding monomers to the end. A mechanism of a similar kind, with essentially 1D control could extend a 2D sheet by stepping along an edge, adding monomers to the end of a row. In some implementations, devices of this sort could be simpler than a ribosome.
To extend a complex structure with a 3D bond network, however, will typically require adding building blocks of specific kinds at specific locations across a 2D surface. This will typically require a mechanism that can step through a series of positions with two degrees of freedom — a step toward greater complexity