Abstract: Lotus effect is based on the superhydrophobicity which results from the micro-nano structure of the surface.A simple experimental configuration is constructed to analyze the shape of a water drop on superhydro-phobic surface.The image processing toolbor（IPT） in MATLAB can be utilized in dealing with the corresponding digital image.By fitting Young-Laplace equation of the drop with the assistance of Runge-Kutta method and Newton-Raphson method,the contact angle of the water drop is obtained with relatively high precision.According to this result,the difference in wetting properties between Wenzel state and Cassie state is analyzed qualitatively,and the self-cleaning ability related to sand particles in different sizes is also presented,which provides an especially convenient and intuitive method for understanding lotus effect.

Key words: lotus effect, superhydrophobicity, self-cleaning, contact angle, Young-Laplace equation, digital image processing