Imaging and estimating the surface heterogeneity on a droplet containing cosolvents.
Cosolvents have numerous applications in many industries as well as scientific research. The shortage in the knowledge of the structures in a cosolvent system is significant. In this work, we display the spatial as well as the kinetic distribution of the cosolvents using droplets as paradigms. When an alcohol/water-containing sessile droplet evaporates on a substrate, it phase segregates into a water-enriched core and a thin alcohol prevailing shell. This is considered to be due to the different escaping rate of solvents out of the liquid-vapor (l-v) interfaces. In between the core and shell phases, there exists a rough and solid-like liquid-liquid (l-l) wall interface as marked by the fluorescent polystyrene spheres and imaged by a confocal microscope. Holes and patches of beads are observed to form on this phase boundary. The water-dispersed beads prefer to partition within the core. The shell prevails in the droplet during most of the drying and shrinks with the l-v boundary. By monitoring the morphological progression of the droplet, the composition of the cosolvent at the liquid-vapor interface is obtained.
Fang
Xiaohua
X
Li
Bingquan
B
Wu
Jun
J
Maldarelli
Charles
C
Sokolov
Jonathan C
JC
Rafailovich
Miriam H
MH
Somasundaran
Ponisseril
P
D000433:1-Propanol / Q000737:chemistry*; D000431:Ethanol / Q000737:chemistry*; D007700:Kinetics; D012997:Solvents / Q000737:chemistry; D013499:Surface Properties; D014835:Volatilization; D014867:Water / Q000737:chemistry*
D012997:Solvents; D014867:Water; D000431:Ethanol; D000433:1-Propanol