基于螺线拟合的高精度接触角测量方法

High Precision Contact Angle Measurement Method Based on Spiral Sitting

液滴在表面上的接触角是表征材料表面性能的重要参数,在流体力学、表面化学、医学等学科中具有重要应用。高精度的接触角测量与三相接触点的准确定位和拟合曲线的吻合程度密不可分,因此提出一种新的接触角测量方法。首先,基于Harris角点检测算法实现液滴三相接触点的自动检测,通过角点间的距离进行筛选,在筛选出角点的基础上进行亚像素角点检测,得到精确的三相接触点的位置。其次,针对多项式曲线拟合疏水和超疏水液滴轮廓不准确的问题,使用对数螺线和阿基米德螺线对液滴轮廓进行拟合,并求出拟合曲线在三相接触点处的切线,得到准确的接触角测量值。最后,对多幅液滴图片进行测量验证,结果表明本方法不仅适用于测量静态接触角,还适用于测量动态接触角,且接触角自动测量结果与电子量角器测量结果基本一致。

The contact angle of droplets on the surface is an important parameter to characterize the surface properties of materials.It has critical applications in fluid mechanics,surface chemistry,medicine,and other disciplines.High-precision contact angle measurement is closely related to the accurate positioning of three-phase contact points and the degree of coincidence of fitting curves.Therefore,a new contact angle measurement method was proposed.Firstly,the three-phase contact point of the droplet was automatically detected based on the Harris corner detection algorithm.The distance between corners was screened,and sub-pixel corner detection was performed based on screened corners to obtain the accurate position of the three-phase contact point.Secondly,in order to solve the problem that the hydrophobic and superhydrophobic droplet contours are not accurate in polynomial curve fitting,the logarithmic spiral and Archimedes spiral were used to fit the droplet contours.The tangent line of the fitted curve at the contact point of the three phases was obtained to obtain the accurate contact Angle measurement value.Finally,several droplet pictures were measured and verified.The results show that this method is not only suitable for measuring static contact angles,but also for measuring dynamic contact angles.The automatic contact angle measurement results are basically consistent with the electronic protractor measurement results.