The behavior of a liquid drop on a solid or liquid surface can vary greatly depending on the properties of the materials in contact. Such spreading behavior of a liquid on a material is relevant to many important processes and studies including mixing, coating, spraying, microfluidic devices and biology. Surfactants inside the lungs are critical in preventing lung surfaces from sticking together and collapsing.
For a liquid drop on a liquid surface, under some conditions surface tension gradients can create large-scale flows in the liquid by the Marangoni effect. This and related topics have been researched for years. Thomson observed several of these effects as early as 1855. These usually involved the classic “tears of wine” example.
To date, studies of the Marangoni effect have primarily focused on miscible liquids such as the study of aqueous surfactant drops on thin layers of short-chain alcohols (Chowdhury, 2004). All that was found on n-alcohol drops dealing with surface tension was a study of surface tension oscillations observed in a droplet of n-octanol suspended under water (Kovalchuk, 2000).
In the present study, we have examined the Marangoni effect at the interface between slightly soluble but immiscible fluids, namely water and long chain alcohols (n = 5-10), which we could not find any documentation on. Behavior in these systems was found to display a surprising degree of complexity.