The drop regained its anisotropic shape with increase in Cn, and this transition continued, with the movement of the three-phase contact line (TPCL). Further, the larger drops show a unique behavior of shape change from anisotropic to isotropic as a function of solvent vapor concentration (Cn) inside the dewetting chamber. The final morphology comprised smaller droplets or threads confined within the pattern grooves and anisotropic large drops covering several pattern stripes. During later stages of dewetting, there was a lateral coalescence of polymer threads across the grating stripes. Our findings show that the initial dewetting stages follow the direction of the underlying grating pattern with the formation of directional holes in the film. The PS film thickness was commensurate with grating pattern height (hP). In this work, we studied the process of dewetting polystyrene (PS) films on grating patterned substrates upon solvent vapor exposure. This instability-mediated drop formation lacks spatial order on flat substrates, but it can be ordered for better combinatorial studies using patterned substrates.

Thin polymer films can become unstable and dewet on a non-wettable substrate leading to the formation of an array of droplets.

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