Thin-film coatings are prevalent in engineering applications. The quality of coating is often affected by the interfacial properties of the coating and the substrate. Due to material inhomogeneity at the interface, as well as internal stresses from deposition conditions, defects often occur in thin-film coatings, such as delamination and cracking. These defects have significant impacts on service behaviors of thin-film composites and often undermine their field applications.<br/><br/>In this work, we find coatings on polymer substrates can be greatly stabilized by ordered surface micro- and nanostructures. Nanoimprint with a flexible nickel template is used to directly pattern surface structures on polycarbonate substrates in a low-cost fashion. By coating silicon dioxide films of various thickness with sputtering on patterned polycarbonate substrates, we find the delamination and cracking behaviors of the oxide films change dramatically in cyclic bending tests. Dense global cracks quickly appear on planar substrates, while cracks are significantly suppressed on patterned substrates. The cracks also terminate at the patterned structures, yielding short local cracks. When the ratio of the pattern depth to the film thickness reaches a certain level, cracks completely disappear in the sputtered thin films.<br/><br/>We systematically study the effect of pattern size, shape, and depth on the cracking behavior of the dielectric coating on patterned polymer substrate. The observation here can also be extended to other material combinations in thin-film composites. Thus surface patterning by nanoimprint can impact a wide range of applications where multilayer composites are required, such as flexible printed circuit boards, catalyst coating on membranes, and surface coating for enhanced surface properties.

Stabilization of thin-film coatings by nanoimprinted surface micro- and nanostructures on polymers

256th National Meeting (2018)

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