Molecular coordination of hierarchical self-assembly

A serious challenge to nanotechnology is the problem of assembling complex physical systems that are structured from the nanoscale up through the macroscale, but embryological morphogenesis provides a good model of how it can be accomplished. We review the fundamental processes in embryological development and argue that these processes, or approximations to them, will be feasible in artificial morphogenetic systems. Nevertheless, there are differences between natural and artificial systems, which future research must address. We explain the approach we are taking toward morphogenetic programming, present a notation for describing morphogenetic programs, and present two examples: the routing of neuron-like connections and the assembly of a segmented body frame with segmented legs by a clock-and-wavefront mechanism. Although much research remains to be done, we show how to implement the fundamental processes of morphogenesis and thereby coordinate very large numbers of agents to self-assemble into multiscale complex hierarchical systems.