Sessile Droplet Evaporation on a Structurally Heterogeneous Multiwalled Carbon Nanotube Membrane

This paper presents an experimental investigation of the evaporating behavior of a 10 mu l water droplet on a structurally heterogeneous surface. A hydrophilic surface was made of multiwalled carbon nanotubes (MWCNTs); then, part of it was tuned to a hydrophobic surface by restructuring it, using the electrowetting method. A droplet was placed across the structure interface by merging two droplets close to the interface, and its evaporation behavior was recorded from both side and top views. Results show that the droplet originally appeared to be asymmetric with the contact angle on the hydrophobic side and remained smaller than the one on the hydrophilic side throughout most of the evaporation process. The contact line of the droplet stayed pinned until an obvious recession occurred from the hydrophobic side to the hydrophilic side in the latter part of the evaporation, although the pinning force was prominent on the hydrophobic side.