| LIN Chang-sheng,ZHU Zhang-lei,YIN Wan-zhong,JIANG You-hua.Droplet Pinning on Spherical Surfaces:Prediction of Apparent Advancing and Receding Angles[J],50(8):95-100 |
| Droplet Pinning on Spherical Surfaces:Prediction of Apparent Advancing and Receding Angles |
| Received:June 13, 2021 Revised:July 29, 2021 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2021.08.009 |
| KeyWord:contact angle apparent angle spherical surface Gibbs free energy pinning |
| Author | Institution |
| LIN Chang-sheng |
Fuzhou University, Fuzhou , China;Guangdong Technion-Israel Institute of Technology, Shantou , China |
| ZHU Zhang-lei |
Northeastern University, Shenyang , China |
| YIN Wan-zhong |
Fuzhou University, Fuzhou , China;Northeastern University, Shenyang , China |
| JIANG You-hua |
Guangdong Technion-Israel Institute of Technology, Shantou , China |
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| Abstract: |
| This paper aims to predict apparent advancing and receding angles, i.e., the angles between the liquid-gas interface and the horizontal plane, of droplets on spherical surfaces using the intrinsic advancing and receding contact angles, namely the angle between the liquid-gas interface and the solid-liquid interface. Based on the Gibbs free energy, droplet volume, and the correlation between the contact angle and the apparent angle, this study predicted the apparent angles of droplets on spherical surfaces and the predicted values were verified by experimental results. Results show that intrinsic advancing and receding contact angles are (91±2)° and (55±3)°, respectively, on a flat PET (Polyethylene Terephthalate) surface. For droplets on the edge of advancing or receding, the contact angles equal to the corresponding intrinsic contact angles when the Gibbs free energy of the system is at the minimal value, where the corresponding apparent angles are apparent advancing and receding angles. Therefore, the apparent advancing and receding angles of droplets on spherical surfaces can be predicted by minimizing the system Gibbs free energy. It is shown that the measured apparent advancing angles are (118±3)°, (110±2)°, (103±2)°, and (100±2)°, the apparent receding angles are (82±2)°, (71±2)°, (64±3)°, and (62±2)°, on spherical surfaces with radius of curvatures of 2 mm, 4 mm, 6 mm, and 8 mm, respectively. Such measured results agree well with the prediction. In conclusion, this paper develops a model that predicts apparent advancing and receding angles of droplets on spherical surfaces using the intrinsic advancing and receding contact angles, droplet volume, and radius of curvatures of the spherical surfaces. |
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