Abstract
This work introduces a facile geometry-controlled method for the fabrication of embossed and engraved polymeric moth-eye-inspired nanostructures in imprinting molds using anodic aluminum oxide (AAO) templates, resulting in a novel anti-reflective transparent coating. The moth-eye nanostructures are prepared directly on the surface of a flexible polyethylene terephthalate (PET) substrate. As a prerequisite procedure, a UV-curable polyurethane acrylate resin is spun on the PET. The shape of the moth-eye nanostructures can then be adjusted by controlling the size and shape of the nanopores in the AAO templates. Both embossed and concaved polymer moth-eye nanostructures were successfully mounted on a PET substrate. Embossed polymer replica molds were prepared using the AAO master templates in combination with an imprinting process. As revealed by field-emission electron microscope (FE-SEM) images, conical nanopatterns in the AAO template with a diameter of ~90 nm and a depth of ~100 nm, create a homogeneous embossed morphology in the polymer moth-eye nanostructure. The polymeric molds with the depths of 300 and 500 nm revealed the amalgamated structures in their apexes. In addition, a dip-imprinting process of the polymeric layers was implemented to yield a concaved mold by assembly on the surface of the 100 nm embossed polymer mold substrate. Considering that the embossed structures may be crumbled due to their protuberant shapes, the concaved geometries can have an advantage of stability in a certain application concerning physical degradation along with a higher transmission by ~2%, despite somewhat nonuniform structure. The experimental and theoretical results of this study indicate that this polymer layer has the potential for use in anti-reflective coating applications in transparent films.
Highlights
Nanostructures have been used for various applications in chemistry and materials science [1]
Physicochemical Characterization and COMSOL Multiphysics Simulation anodic aluminum oxide (AAO) templates and moth-eye-like nanostructures of polymer layers were examined via a JEOL JSM-7500F field-emission electron microscope (FE-SEM) (Tokyo, Japan)
For UV imprinting, coating the polyethylene terephthalate (PET) with a polymer is a prerequisite procedure, and the nanostructured moth-eye layer was applied using an AAO master mold, which was subsequently compressed against polymer-coated PET film using a roll bar
Summary
Nanostructures have been used for various applications in chemistry and materials science [1]. There has been a series of studies on the AAO templateassisted synthesis of moth-eye-inspired nanostructures reporting significant properties such as superhydrophobicity [17], anti-reflectivity [18,19], and ultrasensitive substrates for surface-enhanced Raman scattering-based detection [4,20] Such templates represent a low-cost and facile process to provide an alternative to the above-mentioned techniques. Since AAO platforms have been successfully employed in preparing nanostructured metal materials with high uniformity in numerous shapes, including wires, tubules, rods, and dots, the present method of combining an AAO template with the UV imprinting process appears to be a convenient, straightforward, low-cost, and reusable method to build moth-eye-inspired polymeric nanostructures with a promise for anti-reflective coating applications
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