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Stability of a thin liquid layer, spreading on a quasi–rotating disk
Author(s) -
Boettcher Konrad,
Ehrhard Peter
Publication year - 2009
Publication title -
pamm
Language(s) - English
Resource type - Journals
ISSN - 1617-7061
DOI - 10.1002/pamm.200910207
Subject(s) - coating , capillary action , lubrication , lubrication theory , spin coating , evaporation , layer (electronics) , materials science , capillary number , mechanics , composite material , rotation (mathematics) , thin film , process (computing) , nanotechnology , thermodynamics , physics , computer science , mathematics , geometry , operating system
In many industrial processes solids are coated to obtain specific surface properties, as e.g. corrosion resistance, mechanical (wear) resistance, optical, or electrical properties. Even today many coating processes are not fully understood and the choice of parameters is largely based on experience. Hence, a prediction of the complete hydrodynamic process and the appearance of instabilities in its dependency on the parameters appears highly desirable. This would serve to optimize the quality of the coating. A common coating technique is the so‐called spin coating. The coating agent is dissolved or suspended in a liquid, brought onto the solid, spread by rotation, and the carrier liquid is finally removed by evaporation or by chemical reactions. In this article an evolution equation is derived from lubrication theory, valid for thin liquid layers. The model involves a dynamic contact angle, centrifugal, capillary, and gravitational forces. The evolution equation can be solved analytically, provided the capillary number is small. Then a coupled linear stability analysis of the contact line and the free interface is performed. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)