SPREADING OF OIL DROPLETS ON SILICON-OXIDE SURFACES WITH PARALLEL V-SHAPED CHANNELS

The spreading of silicone and paraffin oils has been studied on two en ergetically and chemically different smooth surfaces (gold and polysty rene). It was found that for these surfaces, neither the surface tensi on nor the surface free energy influenced the spreading behaviour of t he oils. The data for the two different liquids can be transposed onto a master curve when the product of velocity and viscosity is plotted versus the dynamic contact angle. The spreading of paraffin oil drople ts was also studied on a set of silicon oxide surfaces containing para llel v-shaped surface channels at various widths and spacings. It was found that the sharp edges of the channel walls strongly affected spre ading, and that the droplet shape was distorted from the usual circula r shape displayed on a smooth surface. An elongated droplet was formed with the contact line following a channel edge and with the short sid es having a semicircular shape. Transverse spreading was very slow and decreased as the spacing was decreased Increased channel size and dec reased spacing produced an increase in the spreading velocity in the d irection of the channels.