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On the origin of the imaginary part of complex contact angles
Author(s) -
Jennissen H. P.
Publication year - 2015
Publication title -
materialwissenschaft und werkstofftechnik
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.285
H-Index - 38
eISSN - 1521-4052
pISSN - 0933-5137
DOI - 10.1002/mawe.201500437
Subject(s) - the imaginary , ideal (ethics) , wetting , contact angle , surface tension , wilhelmy plate , surface (topology) , surface roughness , classical mechanics , geometry , physics , thermodynamics , mathematics , philosophy , epistemology , psychotherapist , psychology
Complex contact angles of water on rough surfaces have been described to consist of a real part for ideal wetting and of an imaginary part for non‐ideal wetting (Jennissen, 2011, 2014). The concept of imaginary contact angles has accordingly been successfully applied to the analysis of hyperhydrophilic rough surfaces. The origin of the imaginary part of complex contact angles has hitherto been attributed to the non‐ideality of surfaces (e.g. surface roughness) but is otherwise unclear. It is generally accepted that the Young equation is valid, if the criteria ideal surface and thermodynamic equilibrium are fulfilled. What has been overlooked is a third criterion, namely, if an ideal fluid also exists. This criterion, has never been seriously questioned, but is assumed to be fulfilled. Recent evidence indicates that this assumption is false. Xiong et al. 2014 have reported that the surface tension of water is a complex quantity consisting of a real and an imaginary part. In this paper it is demonstrated that imaginary contact angles can also originate after incorporation of a complex surface tension of water into the Young and Wilhelmy equations, thus confirming the concept of complex contact angles also from the side of the non‐ideality of the fluid.