techniques for handling liquid films is needed. A promising scenario is that of exploiting substrate heterogeneity to manipulate the motion of thin films, specially in the emerging field of microfluidics [8], where a thin film geometry is a small friction alternative to common channels, as a medium to conduct microflows [9]. Substrate heterogeneity has proven useful for interface handling, as in the sorting of drops running on dry substrates [10], or the creation of mixing domains in microchannels [11]. 

By profiting from heterogeneous substrates, our main motivation in this work will be to find ways in which thin films can be handled, orienting them toward a preferred path and controlling the way in which contact line structures grow. We shall perform a theoretical study, based on full three-dimensional hydrodynamical simulations, of the effect of imposing a hydrophilic-hydrophobic chemical pattern on the growth of the unstable contact line, exploring a variety of pattern configurations to gain understanding on how to control the motion of the thin film, on top of the intrinsic time and lengthscales of the contact line instability. 

The problem of unstable contact lines in driven thin films has been actively studied during the last two decades. Several experimental studies have addressed the problem of films driven by gravity on homogeneous substrates. In general, experiments are performed either by forcing a constant volume of liquid or by driving the film at constant injection rate. The constant volume configuration has been studied by Silvi and Dussan [5], Jerret and de Bruyn [6], and de Bruyn [7] using dry solids. They all agree in that sawtooth shaped structures are obtained on hydrophilic substrates, while fingers grow when using a hydrophobic substrate. Veretennikov, Indeikina and Chuang [12] observe the growth of fingers on a dry substrate, while for a prewet substrate sawtooth shapes are observed. For films driven at a constant flux, Johnson, Schutler, Miksis and Bankoff [13] observe that sawtooth and finger structures can be obtained for the same fluid and substrate combination by varying the inclination angle. 

Theoretical efforts have focused on the early stages of contact line destabilization and the subsequent nonlinear dynamics on homogeneous substrates. Generally speaking, the framework is that of lubrication theory, in which the film dynamics are reduced to a two dimensional problem by profiting from the smallness of the film thickness, and which is valid for hydrophilic substrates. Wetting properties enter in the regularization of the spurious divergence of viscous dissipation at the contact line. Standard approaches to this problem 

