TY - JOUR

T1 - Droplet pinning on spherical surfaces

T2 - Prediction of apparent advancing and receding angles

AU - Lin, Chang Sheng

AU - Zhu, Zhang Lei

AU - Yin, Wan Zhong

AU - Jiang, You Hua

N1 - Publisher Copyright:
© 2021, Chongqing Wujiu Periodicals Press. All rights reserved.

PY - 2021

Y1 - 2021

N2 - 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.

AB - 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.

KW - Apparent angle

KW - Contact angle

KW - Gibbs free energy

KW - Pinning

KW - Spherical surface

UR - http://www.scopus.com/inward/record.url?scp=85114502911&partnerID=8YFLogxK

U2 - 10.16490/j.cnki.issn.1001-3660.2021.08.009

DO - 10.16490/j.cnki.issn.1001-3660.2021.08.009

M3 - 文章

AN - SCOPUS:85114502911

SN - 1001-3660

VL - 50

SP - 95

EP - 100

JO - Surface Technology

JF - Surface Technology

IS - 8

M1 - 1001-3660(2021)08-0095-06

ER -