  Colloidal self-replication represents an exciting research frontier in soft
matter physics. Currently, all reported self-replication schemes involve
coating colloidal particles with stimuli-responsive molecules to allow
switchable interactions. In this paper, we introduce a scheme using
ferromagnetic dipolar colloids and pre-programmed external magnetic fields to
create an autonomous self-replication system. Interparticle dipole-dipole
forces and periodically varying weak-strong magnetic fields cooperate to drive
colloid monomers from the solute onto templates, bind them into replicas, and
dissolve template complexes. We present three general design principles for
autonomous linear replicators, derived from a focused study of a minimalist
sphere-dimer magnetic system in which single binding sites allow formation of
dimeric templates. We show via statistical models and computer simulations that
our system exhibits nonlinear growth of templates and produces nearly
exponential growth (low error rate) upon adding an optimized competing
electrostatic potential. We devise experimental strategies for constructing the
required magnetic colloids based on documented laboratory techniques. We also
present qualitative ideas about building more complex self-replicating
structures utilizing magnetic colloids.
