An inclined plane based dynamic contact angle algorithm and its validity in application of hydrophobicity measurement for insulating materials

The dynamic contact angle is an important method to evaluate the hydrophobicity of material. To improve the accuracy of the dynamic contact angle measurement, the validity of the ellipse fitting algorithm in application of the dynamic contact angle measurement is analyzed. Water drop profiles with different volumes, contact angles and inclination angles are numerically generated based on the Laplace equation and finite difference method and at the same time, the ellipse fitting algorithm is used to calculate the dynamic contact angle. The results reveal that the significant error (/sp Gt/7°) in contact angle may be difficult to find. The dynamic contact angle error increases with the water drop volume. The ellipse fitting algorithm is not suitable for the case of too small or large contact angle. The critical water drop volumes corresponding to an error of 3° are given and the accuracy of the dynamic contact angle measurement is improved by using the volume. The results are verified by the experiments.