The generation of octadecanol monolayers on acoustically levitated water drops

Condensed monolayers of octadecanol have been formed on the surface of single water drops suspended in ambient air by acoustic levitation. As known from former work which has been mostly carried out on Langmuir troughs many monolayers are able to reduce remarkably the evaporation rate at the air–water interface. In contrast to Langmuir troughs, acoustic levitation offers the advantages of a minimized and contact-less technique. The surface area of an evaporating water drop suspended in ambient air declines linearly with time described by the evaporation constant K. After adding octadecanol a condensed monolayer is formed on the drop surface while the drop evaporates. During this process, the evaporation constant is scaled down by a factor of approximately 20.