Abstract
Over the years, different approaches to obtaining antireflective surfaces have been explored, such as using index-matching, interference, or micro- and nanostructures. Structural super black colors are ubiquitous in nature, and biomimicry thus constitutes an interesting way to develop antireflective surfaces. Moth-eye nanostructures, for example, are well known and have been successfully replicated using micro- and nanofabrication. However, other animal species, such as birds of paradise and peacock spiders, have evolved to display larger structures with antireflective features. In peacock spiders, the antireflective properties of their super black patches arise from relatively simple microstructures with lens-like shapes organized in tightly packed hexagonal arrays, which makes them a good candidate for cheap mass replication techniques. In this paper, we present the fabrication and characterization of antireflective microarrays inspired by the peacock spider’s super black structures encountered in nature. Firstly, different microarrays 3D models are generated from a surface equation. Secondly, the arrays are fabricated in a polyacrylate resin by super-resolution 3D printing using two-photon polymerization. Thirdly, the resulting structures are inspected using a scanning electron microscope. Finally, the reflectance and transmittance of the printed structures are characterized at normal incidence with a dedicated optical setup. The bioinspired microlens arrays display excellent antireflective properties, with a measured reflectance as low as 0.042 ± 0.004% for normal incidence, a wavelength of 550 nm, and a collection angle of 14.5°. These values were obtained using a tightly-packed array of slightly pyramidal lenses with a radius of 5 µm and a height of 10 µm.
Highlights
When the directional reflectance of a surface is below 0.5% and all light is absorbed by the bulk material, that surface can be considered super black [2]
Before investigating all the parameters, hemispheres were first printed with varying characteristic structure sizes, R0, ranging from 2 to 10 μm
R0 was set to 5 μm and the other parameters were individually varied from 1 to 2, while keeping the remaining parameters the same as for the hemisphere
Summary
Antireflective (AR) coatings are typically applied to the surface of various optical elements in order to reduce reflection and improve efficiency. AR coatings have been around for more than a century, with the simplest form dating back to Lord. Rayleigh’s 1886 tarnished glass [1]. Different approaches for obtaining AR coatings exploit index-matching, interference, or absorbing phenomena. When the directional reflectance of a surface is below 0.5% and all light is absorbed by the bulk material, that surface can be considered super black [2]. Super black surface treatment was first developed by Brown et al at the National Physical Laboratory in the UK in 2002 [3] and soon gained significant interest, both in academia and in industry
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
