  We demonstrate a simple method by which time-dependent interactions can be
exploited to improve self-assembly in colloidal systems. We apply this method
to two systems: a model colloid with short-ranged attractive potentials that
undergoes crystallisation, and a schematic model of cluster growth. The method
is based on initially strong bonds between particles, to accelerate nucleation,
followed by a stage with weaker bonds, to promote growth of high-quality
assembled structures. We track the growth of clusters during assembly, which
reveals insight into effects of multiple nucleation events, and of competition
between the growth of clusters with different properties.
