A noise-resistant ADSA-PH algorithm for superhydrophobic surface’s static contact angle evaluation

Abstract

The blur around the contact points significantly decreases the evaluated static contact angle for superhydrophobic surface which is clearly presented in the paper. To improve the accuracy in the evaluated static contact angle for superhydrophobic surface, an accurate static contact angle algorithm, namely ADSA-PH (axisymmetric drop shape analysis-profile and height), is proposed. It discards the extracted drop edge points close to the contact points and makes use of the residual points and the drop height to determine the static contact angle. The contact angle errors caused by the blur close to the contact points are significantly reduced. The classical ADSA-P algorithm, the modified selected-plane method and the proposed algorithm are used to evaluate static contact angle. The results validate the proposed algorithm. The accuracy in the evaluated contact angle increases with increasing image resolution. To reduce the error caused by a limitation of image resolution, the minimum allowable image resolutions are presented.

Uncertainties in contact angle goniometry

“…51 It has been shown that for superhydrophobic surfaces with contact angles approaching 1801 error in determined contact angles can be up to 51 even when subpixel resolution is used. 30 The errors in contact angle produced by one-pixel displacement of the baseline To demonstrate the importance of correct positioning of the baseline, we simulate a one-pixel baseline shift from an actual baseline position. We perform numerical simulations described above, and the results are shown in Fig.…”

“…[25][26][27][28][29] The choice of the image analysis algorithm is important since different algorithms give different values of contact angles. 30,31 Contact angle goniometry, as a technique that utilizes image processing, is prone to substantial inaccuracies for superhydrophobic surfaces (y 4 1501). 32 The area close to the three-phase contact line is distorted or blurred due to optical errors, [33][34][35] leading to systematic errors in the determination of the droplet shape and tangent line (Fig.…”

“…38 For specific image resolution, one subpixel or pixel may correspond to a few mm, and thus uncertainty in contact angle can be even larger than 101. 30 Despite many attempts to improve contact angle measurements, 19,30,[39][40][41][42][43] the technique remains to a certain degree subjective and depends on the experience and skillfulness of the user. Even for a tiny deviation of the optical path from the horizontal or for a slight tilt of the sample, errors in the measured contact angle can be significant.…”

“…S1). The results obtained by independent, experienced scientists can also easily vary up to a dozen degrees 30,38 even if the same experimental conditions were used, and up to 101 if the same image is analysed ( Fig. 1d and ESI, † Fig.…”

Characterization of Rough PTFE Surfaces by the Modified Wilhelmy Balance Technique

“…Contact angle measurements using the sessile drop technique depend on the experience and skills of the user. There are large deviations even if an experienced user performs the measurements [44]. Vuckovac et al have shown that errors increase for superhydrophobic surfaces.…”