Coalescence dynamics in oil-in-water emulsions at elevated temperatures.

Emulsion stability in a flow field is an extremely important issue relevant for many daily-life applications such as separation processes, food manufacturing, oil recovery etc. Microfluidic studies can provide micro-scale insight of the emulsion behavior but have primarily focussed on droplet breakup rather than on droplet coalescence. The crucial impact of certain conditions such as increased pressure or elevated temperature frequently used in industrial processes is completely overlooked in such micro-scale studies.

Antisurfactant (Autophobic) Behavior of Superspreader Surfactant Solutions.

Surfactants are often added to water to increase the wetting of hydrophobic surfaces. We previously showed that most surfactant solutions behave identically to simple liquids with the same surface tension, indicating that the surfactants do not change the wettability of the solid surface itself. Here, we show that the superspreading surfactant Silwet results in a systematically higher contact angle on a hydrophobic surface than other surfactant solutions of comparable liquid-vapor surface tension.