  The fracture mechanics was widely employed to explain the crack propagation
in the deposition produced by drying colloidal suspension. However, more
complex than conventional fracture, those cracks periodically distribute and
make up a unique pattern. This still remains mysterious so far. Inspired by the
concept of spinodal decomposition, here, we develop the theory to elucidate the
spatial arrangement of the cracks, which indicates that the crack pattern is
generated by the phase separation of colloidal clusters and water. It concludes
that the crack spacing results from the wavelength of the concentration
fluctuation during the phase separation, linearly growing with the increase of
the deposition thickness and initial particle concentration, which is
consistent with experimental results.
