Superspreading: A possible mechanism

It is suggested that superspreading of droplets of dilute aqueous solutions of siloxane surfactants over a hydrophobic surface is driven by: (i) the spreading at their leading edges of the surfactant as bilayers, (ii) the suction of water in the hydrophilic atmosphere between the two layers and (iii) the displacement of the surfactant and water by a Marangoni effect intensified by the formation of bilayers. An explanation is provided for the observation that the rate of spreading passes through a maximum at an optimum degree of surface wettability (surface hydrophobicity).