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Self-replication is the de facto hallmark of life and has thus far eluded efforts to mimic it in physical engineered systems. According to the John von Neumann self-replication model, there are four major components – (i) a physical instantiation of a program of instructions to build the self-replicator (DNA), (ii) a mechanism for copying those instructions (DNA polymerase), (iii) a controller to interpret those instructions into a set of physical procedures (proteins), and (iv) a means to physically construct the self-replicator (ribosomes). The first and latter two parts constitute a universal Turing machine and universal constructing machine respectively. It is these three parts, in particular, with which we are concerned. The most important constraint is in physical closure which requires a: (i) minimum materials inventory; (ii) minimal set of chemical processes; (iii) minimum set of component part types; (iv) minimal set of manufacturing methods; (v) minimal assembly requirements. This aids in the requirements for energy and information closure. We have identified (i) a minimal list of functional materials (demandite) to build the self-replicator; (ii) a single electrochemical process to extract the metals supplemented with a small set of mineral pre-processing methods; (iii) a set of two fundamental components that are key – the electric motor (which may be configured into any kinematic machine, i.e. universal constructor) and vacuum tube (active component of Turing-complete neural electronics, i.e. universal computer); (iv) a set of additive manufacturing techniques to 3D print all parts including electric motors and vacuum tubes.
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