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Multiscale Ommatidial Arrays with Broadband and Omnidirectional Antireflection and Antifogging Properties by Sacrificial Layer Mediated Nanoimprinting

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journal contribution
posted on 24.02.2015 by Hemant Kumar Raut, Saman Safari Dinachali, Yee Chong Loke, Ramakrishnan Ganesan, Kwadwo Konadu Ansah-Antwi, Aleksander Góra, Eng Huat Khoo, V. Anand Ganesh, Mohammad S. M. Saifullah, Seeram Ramakrishna
Moth’s eye inspired multiscale ommatidial arrays offer multifunctional properties of great significance in optoelectronic devices. However, a major challenge remains in fabricating these arrays on large-area substrates using a simple and scalable technique. Here we present the fabrication of these multiscale ommatidial arrays over large areas by a distinct approach called sacrificial layer mediated nanoimprinting, which involves nanoimprinting aided by a sacrificial layer. The fabricated arrays exhibited excellent pattern uniformity over the entire patterned area. Optimum dimensions of the multiscale ommatidial arrays determined by the finite-difference time domain simulations served as the design parameters for replicating the arrays on glass. A broadband suppression of reflectance to a minimum of ∼1.4% and omnidirectional antireflection for highly oblique angles of incidence up to 70° were achieved. In addition, superhydrophobicity and superior antifogging characteristics enabled the retention of optical properties even in wet and humid conditions, suggesting reliable optical performance in practical outdoor conditions. We anticipate that these properties could potentially enhance the performance of optoelectronic devices and minimize the influence of in-service conditions. Additionally, as our technique is solely nanoimprinting-based, it may enable scalable and high-throughput fabrication of multiscale ommatidial arrays.