  We report experiments, modeling and numerical simulations of the
self--assembly of particle patterns obtained from a nanometric metallic square
grid. Initially, nickel filaments of rectangular cross section are patterned on
a SiO$_2$ flat surface, and then they are melted by laser irradiation with
$\sim 20$ ns pulses. During this time, the liquefied metal dewets the
substrate, leading to a linear array of drops along each side of the squares.
The experimental data provides a series of SEM images of the resultant
morphology as a function of the number of laser pulses or cumulative liquid
lifetime. These data are analyzed in terms of fluid mechanical models that
account for mass conservation and consider flow evolution with the aim to
predict the final number of drops resulting from each side of the square. The
aspect ratio, $\delta$, between the square sides' lengths and their widths is
an essential parameter of the problem. Our models allow us to predict the
$\delta$-intervals within which a certain final number of drops are expected.
The comparison with experimental data shows a good agreement with the model
that explicitly considers the Stokes flow developed in the filaments neck
region that lead to breakup points. Also, numerical simulations, that solve the
Navier-Stokes equations along with slip boundary condition at the contact
lines, are implemented to describe the dynamics of the problem.
