6.4.3

Kinematic Self-Replicating Machines

Robert A. Freitas Jr., Ralph C. Merkle, Kinematic Self-Replicating Machines, Landes Bioscience, Georgetown, TX, 2004.

6.4.3 Exemplify a Capable Design

For a proposed molecular assembler design to be acceptable, it must exhibit several elementary capabilities:

(1) Bootstrap-Capable System. It should be obvious that the system design will enable the manufacture of devices of similar or different architecture that can be scaled to larger sizes. Even if the original design describes only a very small device (e.g., with typical dimensions of ~100 nanometers), the manufacturing system, once built, should clearly be capable of “bootstrapping” larger and more complex devices, extending our capabilities beyond the submicron scale and beyond other architectural limitations of the initial system.

(2) Ease of Reprogramming. Molecular assemblers should be able to readily change what they are manufacturing, thus exhibiting ease of reprogramming [209]. For a general manufacturing system, we should be able to redirect the manufacturing process quickly and rapidly in response to changing demand, once a sufficient factory mass or number of device generations has been replicated. Additionally, numerous software issues must be resolved, including methods of rigorously controlling and coordinating the activities of trillions of simultaneously operating nanoscale manipulators for mechanosynthesis with high reliability and flexibility.

(3) Maximum Geometric Accessibility to Products During Manufacture. Positional manufacturing manipulators should have the greatest possible geometric access to the object being manufactured. Designs are favored which give greater access to the parts being manufactured, and which permit a wider range of tools and synthetic methods to be used. This objective is one that can be applied during the geometric design of the system, and which is largely independent of the specific mechanosynthetic reactions used to fabricate the product. Satisfaction of this objective also implies that the design can be adapted to other systems of greater complexity (regardless of size).

(4) Maximum Reliability During Operation. Within the constraints of the limited technologies employed in early designs, the molecular assembler should operate as reliably as possible. The required reliability of subsystems depends on the overall reliability requirements of the entire system, and on the number of subsystems. Even the earliest systems should have a probability of successful replication of at least 99% per replication cycle. Furthermore, the system architecture should be chosen such that the failure of daughter units has minimal impact on the operation of the remaining units that continue to function without error. In this regard, a unit replicator motif is more clearly failure tolerant than a factory replicator motif. The isolation of a failure to a single unit replicator is more clearly feasible than the isolation of a failure in a factory. Continued satisfactory functioning of a factory in the face of a failure would require a more sophisticated failure isolation strategy and would benefit greatly from a method for switching out or circumventing the failed module [2334].

Last updated on 1 August 2005