length of the front. For thinner stripes, surface tension smooths the interface, creating wider structures. On the other hand, wider stripes eventually allow for the growth of unstable wavelengths, which generate additional fingers. In this paper we will study the orientation of the thin film on hydrophilic-hydrophobic patterns of sharply contrasted wetting properties, thus departing from the hydrophilic regime of previous numerical studies [3, 19, 20], analyzing the interplay between the typical length- scale of the pattern and the intrinsic lengthscale of the instability. Apart from orienting the film on a prescribed path, another interesting problem is how to control the growth of the contact line structures triggered by the instability. Both experimental and theoretical results show that fingering can be suppressed by either decreasing the inclination angle of the sub- strate or by increasing its wettability sufficiently, as in these limits the contact line saturates to a sawtooth shape. Decreasing the inclination angle is effective only for mostly wetting fluids; for non wetting fluids fingering is observed even at small inclination angles[5–7, 12]. Increasing surface wettability is then an appealing strategy to improve surface coverage. A way to increase the wettability of the substrate is by imposing a chemical pattern on the solid. Such an exploitation of substrate heterogeneity to control the growth of the film has not been studied previously. This shall be a second question to be addressed in this work. Overall, the instability poses two challenges when trying to handle thin films. First, there is the presence of an intrinsic lengthscale, Λ$_{max}$, which imposes the typical spacing between contact line structures. Secondly, there is an intrinsic timescale, which corresponds to the growth rate of the contact line. We shall therefore explore the effect of patterns where the typical time and lengthscales are comparable to Λ$_{max}$ and the typical growth rate of the film, respectively. Hence, in a hydrophilic domain, the front is expected to saturate to a sawtooth, while for hydrophobic domains contact line growth should occur. The rest of this paper is organized as follows. In section II we present the hydrody- namical model and the lattice-Boltzmann integration algorithm that we use to perform the numerical simulations. Section III is devoted to the results of gravity driven thin films on different substrates. In section III A we study the formation of sawtooth- and finger- shaped fronts on homogeneous substrates. We follow by analyzing the growth of the contact line in different patterned substrates. Section IV A is devoted to longitudinal patterns of hydrophilic-hydrophobic stripes. In section IV B we consider arrangements of hydrophilic- hydrophobic domains in checkerboard patterns. Finally, in section V we discuss our results 5