Dip-coating of chemically patterned surfaces

For the purpose of solution-based manufacturing of organic electronic devices, we conducted dip-coating experiments on flat, chemically patterned surfaces. The patterns consisted of long wettable lines of varying width or triangles of different base lengths on an otherwise non-wettable surface. The thickness of the coated film has been measured as a function of pattern dimensions and coating speed. For lines of width comparable to the capillary length, i.e. several millimeters, which were oriented with the long axis parallel to the direction of withdrawal, qualitative agreement has been found with analytical results by Landau and Levich [1], Darhuber et al. [5] and Davis [6]. For narrower lines, quantitative agreement was found. Whereas the coating of long lines is essentially a steady-state process, the coating of compact shapes such as circles and squares is intrinsically time-dependent and involves capillary break-up effects. Nevertheless, for equilateral triangles oriented tip-down, the dependence of film thickness on coating speed and pattern dimensions was found to resemble the behavior of long lines.