Mechanically-Durable Antireflective Subwavelength Nanoholes on Glass Surfaces Using Lithography-Free Fabrication.

Traditional multilayer antireflection (AR) surfaces are of significant importance for numerous applications, such as laser optics, camera lenses, and eyeglasses. Recently, technological advances in the fabrication of biomimetic AR surfaces capable of delivering broadband omnidirectional high transparency combined with self-cleaning properties have opened an alternative route toward realization of multifunctional surfaces which would be beneficial for touchscreen displays or solar harvesting devices. However, achieving the desired surface properties often requires sophisticated lithography fabrication methods consisting of multiple steps. In the present work, we show the design and implementation of mechanically robust AR surfaces fabricated by a lithography-free process using thermally dewetted silver as an etching mask. Both-sided nanohole (NH) surfaces exhibit transmittance above 99% in the visible or the near-infrared ranges combined with improved angular response at an angle of incidence of up to θi = 60°. Additionally, the NHs demonstrate excellent mechanical resilience against repeated abrasion with cheesecloth due to favorable redistribution of the shearing mechanical forces, making them a viable option for touchscreen display applications.

Nanostructured Hybrid-Material Transparent Surface with Antireflection Properties and a Facile Fabrication Process.

Highly transparent optical surfaces with antireflection (AR) properties have the potential to increase the performance of a wide range of applications, such as windows for photovoltaic cells, photodetectors, and display screens among others. Biomimetic structures inspired by the moth-eye have attracted much attention as they can offer superior AR properties, which can generate broadband, omnidirectional optical transmission, and water-repellent self-cleaning behavior. However, many biomimetic surfaces suffer from time-consuming and complex processing, for example, electron beam and nanoimprint lithography, and/or sub-optimal mechanical reliability. In this paper, we introduce a hybrid material approach-nanostructured polyimide on a substrate-for demonstrating a surface with significant AR and hydrophobic properties together with low scattering (haze) and high mechanical resistance. As an example of applications, we demonstrate an indium tin oxide transparent conductive substrate with a large AR effect and optical transmission associated to the nanostructured polyimide coating. The proposed design and method based on conventional spin-coating and lithography-free metal dewetting have the potential to be a low-cost processing path of nanostructured AR transparent substrates.

Antireflective Transparent Oleophobic Surfaces by Noninteracting Cavities.

Oleophobic surfaces have been so far realized using complex microscale and nanoscale re-entrant geometries, where primary and secondary structures or overhang geometries are typically required. Here, we propose a new design to create them with noninteracting cavities. The suspension of liquid droplets relies on the mechanism of compression of air under the meniscus leading to stable composite oil-air-solid interfaces. To demonstrate the concept, we make oleophobic surfaces, with contact angle for oleic acid of about 130° (and hexadecane about 110°), using both microholes in silicon and nanoholes in glass. Thanks to the subwavelength dimensions and antireflection effect of the nanoholes, the glass substrate also shows a high degree of optical transparency with optical transmission exceeding that of the initial bare substrate. Crockmeter tests without any significant change in morphology, optical and wetting properties after more than 500 passes also confirm the high mechanical durability of the nanohole surface. The results indicate the possibility of using the proposed oleophobic surfaces for a wide range of applications, including self-cleaning transparent windows and windshields for automobiles and aircrafts.