  It has been argued that a central objective of nanotechnology is to make
products inexpensively, and that self-replication is an effective approach to
very low-cost manufacturing. The research presented here is intended to be a
step towards this vision. We describe a computational simulation of nanoscale
machines floating in a virtual liquid. The machines can bond together to form
strands (chains) that self-replicate and self-assemble into user-specified
meshes. There are four types of machines and the sequence of machine types in a
strand determines the shape of the mesh they will build. A strand may be in an
unfolded state, in which the bonds are straight, or in a folded state, in which
the bond angles depend on the types of machines. By choosing the sequence of
machine types in a strand, the user can specify a variety of polygonal shapes.
A simulation typically begins with an initial unfolded seed strand in a soup of
unbonded machines. The seed strand replicates by bonding with free machines in
the soup. The child strands fold into the encoded polygonal shape, and then the
polygons drift together and bond to form a mesh. We demonstrate that a variety
of polygonal meshes can be manufactured in the simulation, by simply changing
the sequence of machine types in the seed.
