© 2004 Robert A. Freitas Jr. and Ralph C. Merkle. All Rights Reserved.

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

4.11 Extruding Brick Assemblers (1992-2003)

In all assembler designs which employ a physical barrier to maintain separate internal and external environments, the products of molecular manufacturing – including successive replicas of the manufacturing system itself – must eventually be delivered from the internal space to the exterior environment. At least three strategies to accomplish this are apparent. First, the export of product to the external environment can be allowed to permanently contaminate the interior environment of the assembler, whereupon the original assembler can no longer function and must be discarded. Second, product export can be allowed to contaminate the interior environment of the assembler, but the assembler is designed to reseal itself and remediate its internal environment post-export, after which remediation the original assembler can then resume manufacturing operations with some delay. Third, product export can be accomplished while continuously maintaining the integrity of the physical barrier during the export process – there is never any contamination of the interior environment of the assembler and the original assembler can resume manufacturing operations immediately following product export, with no delays. Examples of the third approach might include progressive airlocks, construction of internal partitions or sliding sealwalls to isolate the product object prior to export, discardable “shipping crates,” or continuous extrusion systems.

A simple example of the latter approach is the “replicating brick” or “extruding brick” geometry, first suggested by Merkle and described in Section 14.3.2 of Nanosystems [208] in 1992.* In this geometry (Figure 4.38), an exported object can have two physical dimensions as large as the two smallest dimensions of the manufacturing system, and can have a third dimension which is essentially unlimited. Thus delivered products can be of the same size or larger than the system that produced them, and just three replicative generations may suffice to increase all three physical dimensions of the original manufacturing system. (A more complex extrusion system could export product objects that are rolled up and later unfurl, as proposed by Merkle [212], or that have nonrigid walls composed of the metamorphic surfaces proposed by Freitas in Section 5.3.2 of Nanomedicine [228], allowing all three product dimensions to be simultaneously larger than those of the parent device because the product object can expand itself immediately after extrusion, like inflating a balloon.)

* According to S.M. Krylov [2320], a crudely similar architecture “was suggested for a self-replicating robot in the patent application submitted to USSR Patent Department in 1974 [see included figures]. Of course this robot was built from ‘macro’ parts, but the concurrence of conceptual solutions is obvious. By the way, it is clear that there are other possible shapes very close to replicating brick.”

Three proposals for molecular assemblers employing the extruding brick architecture have been published in the literature – the Drexler minimal assembler (Section 4.11.1), the Merkle replicating brick assembler (Section 4.11.2), and the Merkle-Freitas molecular assembler (Section 4.11.3) – as summarized below.

Last updated on 1 August 2005