接触角测试的量高法的适用范围

Range of Validity of Hypsometry for Contact Angles

量高法是接触角测试的一种简便的测试方法,在工程和研究中得到广泛应用。该方法基于液滴的球形假设,决定其仅有有限的适用范围。通过数值模拟的方法研究量高法所引起的接触角偏差,从而考察量高法的适用范围并给出接触角修正的方法。研究发现:采用量高法计算的接触角与真实接触角有很大的偏差,这种偏差在超疏水表面上的接触角测量中尤为明显,可达20°;偏差范围决定于液滴的性质、表面的润湿性能和液滴的体积,液体表面张力小、接触角大和液滴体积大将导致大的偏差。在超疏水或超疏油表面研究中,为精确表征表面的润湿性能,需要对量高法进行偏差修正,提出了一种用于偏差修正的方法,通过该方法可精确确定出真实接触角。

As a simple and convenient method for contact angle measurement, hypsometry has been broadly used in engineering. However, the fact that this method is based on the assumption of spherical liquid droplet cau- ses its limited scope of application. Here numerical investigation of the contact angle deflection caused by the hyp- sometry is used and some methods are sought to modify the results. Results showed that there is considerable deflec- tion between the contact angle calculated from hypsometry and the actual value especially in the case of the droplet on superhydrophobic surfaces and superoleophobic surfaces, in which the maximum contact angle deflection is close to 20~. And the deflection depends on the liquid property, the wettability of the surface and the droplet volume. The lower liquid surface tension, larger contact angle and more droplet volume, the more the contact angle deflec- tion is. Therefore, to accurately characterize the wettability of superhydrophobic surfaces and superoleophobic sur- faces, it is necessary to modify the results by some strategies, one of which is proposed.