Contact Angle axisymmetric drop technique

Contact Angle Measurements. Axisymmetric drop shape analysis - profile (ADSA-P) The hydrophobicity/ hydrophilicity of a solid surface is usually expressed in terms of wettability, which can be quantified by contact angle measurements. ADSA-P is a technique to determine liquid-fluid interfacial tensions and contact angles... 

Kwok, D.Y., Gietzelt, T., Grundke, K., Jacobasch, H.J., and Neumann, A.W. (1997). Contact angle measurements and contact angle interpretation. 1. Contact angle measurements by axisymmetric drop shape analysis and a goniometer sessile drop technique. Langmuir, 13, 2880-2894. 

For even better results, drop profile analysis can be applied instead of measuring the contact angle directly (axisymmetric drop shape analysis, ASDA Fig. 4.20). This technique extracts experimental drop profiles from video images while slowly increasing or decreasing the droplet volume [42, 43]. The best fit of experimental data with theoretical assumptions based on the Laplace equation of capillarity allows one to calculate the surface/inter-facial tension and subsequently the contact angle. Also droplet radius, droplet volume, and the contact area are computed. ADSA can therefore reveal... 

Axisymmetric Drop Shape Analysis-Profile The technique of Axisymmetric Drop Shape Analysis-Profile (ADSA-P), as practiced by the present authors, is a powerful method for determining contact angles and liquid-fluid interfacial tensions from the profile of liquid drops. Besides these two parameters, the drop volume and the drop surface area, as well as the drop radius, all with their corresponding 95% confidence limits, or other statistical information are also output. 

Axisymmetric Drop Shape Analysis-Diameter As discussed earlier, a drop shape method, such as ADSA-P, utilizes the meridian profile of a sessile drop to calculate the contact angle and the interfacial tension. Despite its versatility, this technique does suffer from some limitations. In cases of very low contact angles (less than 20°), it may be difficult to measure contact angles accurately by using profile techniques, e.g. ADSA-P. In order to avoid this difficulty, an alternate method called ADSA-(C)D (contact diameter) has been developed by utilizing the drop contact diameter (see Figure 14.6(b)... 

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