Effect of evaporation and solutocapillary-driven flow upon motion and resultant deposition of suspended particles in volatile droplet on solid substrate

Particle motion in a volatile droplet on a solid surface, especially the behavior of particles depositing in the vicinity of a solid–liquid–gas boundary line (contact line) is focused. This phenomenon is called the ‘coffee stain problem’. Motion and deposition of the particles suspended in distilled water droplets and distilled water–ethanol mixture droplets are discussed. The spatio-temporal particle motion is analyzed by the three-dimensional particle tracking velocimetry (3D PTV). A discussion of the morphology of the particles stuck to the solid surface after the dryout of the droplet is also given.