  We introduce a new property of tile self-assembly systems that we call
size-separability. A system is size-separable if every terminal assembly is a
constant factor larger than any intermediate assembly. Size-separability is
motivated by the practical problem of filtering completed assemblies from a
variety of incomplete "garbage" assemblies using gel electrophoresis or other
mass-based filtering techniques.
  Here we prove that any system without cooperative bonding assembling a unique
mismatch-free terminal assembly can be used to construct a size-separable
system uniquely assembling the same shape. The proof achieves optimal scale
factor and temperature for the size-separable system. As part of the proof, we
obtain two results of independent interest on mismatch-free temperature-1
two-handed systems.
