Cross-sectional tracking of particle motion in evaporating drops: flow fields and interfacial accumulation.
Langmuir
; 29(21): 6221-31, 2013 May 28.
Article
em En
| MEDLINE
| ID: mdl-23611508
ABSTRACT
The lack of an effective technique for three-dimensional flow visualization has limited experimental exploration of the "coffee ring effect" to the two-dimensional, top-down viewpoint. In this report, high-speed, cross-sectional imaging of the flow fields was obtained using optical coherence tomography to track particle motion in an evaporating colloidal water drop. This approach enables z-dimensional mapping of primary and secondary flow fields and changes in these fields over time. These sectional images show that 1 µm diameter polystyrene particles have a highly nonuniform vertical distribution with particles accumulating at both the air-water interface and the water-glass interface during drop evaporation. Particle density and relative humidity are shown to influence interfacial entrapment, which suggests that both sedimentation rate and evaporation rate affect the dynamic changes in the cross-sectional distribution of particles. Furthermore, entrapment at the air-water interface delays the time at which particles reach the ring structure. These results suggest that the organization of the ring structure can be controlled based on the ratio of different density particles in a colloidal solution.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Poliestirenos
/
Água
Tipo de estudo:
Prevalence_studies
Idioma:
En
Ano de publicação:
2013
Tipo de documento:
Article