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4568177 
Journal Article 
Micro-flow induced peculiar surface profile of film from dried droplet of water-Poly (ethylene oxide) solution 
Hu Yinchun; Zhou Qiong; Dong Cuicui; Cui Lishan 
2013 
1 
Key Engineering Materials
ISSN: 1013-9826
EISSN: 1662-9795 
Key Engineering Materials 
531-532 
358-361 
WOS:000316642300079 
We report a peculiar surface of poly(ethylene oxide) (PEO) film from droplet of water-PEO solution dried at heating substrate. The drying process contains two stages. The contact line is pinned initially. When substrate temperature reaches 60 degrees C, it starts to recede and continues to leave a film The resulted film contains an edge-ring and middle-step surface profile. The rheological properties of PEO solution were studied. We found that capillary flow is dominant in the first drying stage and Marangoni flow appears because concentration gradient induced strong Marangoni effect and high temperature induced sharply decrease of viscous stress resulted in the contact line receding in the later drying stage. We confirm that the ringlike deposit is formed by outward capillary flow and the step in the middle is formed by Marangoni flow which carries solute to the inner, and these flows compete with the viscous force. 
Poly(ethylene oxide); Droplet; Micro-flow; Surface profile