Spreading of a micrometric fluid strip down a plane under controlled initial conditions.

We experimentally study the spreading of a small volume of silicon oil down a vertical plane with small Bond number. The initial condition is characterized by a horizontal long fluid strip with cross sectional area A and width w(0). We find that the experiments are characterized by a unique nondimensional parameter, R proportional w4(0)/(a2A), where a is the capillary length. An empirical criterium to estimate the onset of the contact line instability is established. The later rivulet formation at the contact line leads to a pattern which is characterized by a dominant wavelength. We find that this wavelength is approximately proportional to R(-1/4).