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Fingering Instability and Maximum Radius at High Rotational Bond Number

2001; Institute of Physics; Volume: 148; Issue: 5 Linguagem: Inglês

10.1149/1.1365148

1945-7111

Mingwen Wang, Fu‐Chu Chou,

Fluid Dynamics and Heat Transfer

The spin-coating in the modern microfabrication practice takes place at a high rotational Bond number, Bo. An experimental study of fingering instability and maximum attainable radius at high Bo for both the injected liquid and released drop is presented. Compared to the released drop procedure, the effect of liquid injection tends to decrease the critical radius and the number of fingers at high Bo, although this effect is negligible for low Bo. The characteristics of apparent contact angles of the liquid front and the critical capillary number for high Bo are quite different from those for low Bo. This difference mainly comes from the competition between the speed of liquid spreading pushed by the centrifugal force and the speed of molecular wetting. For the number of fingers, are constant and independent of Bo. For high increases rapidly with Bo. The maximum attainable radius is almost independent of the fluid's viscosity μ and injection Reynolds number but is only a function of Bo for the fluids of high viscosity considered in this work. © 2001 The Electrochemical Society. All rights reserved.