The Path to Invisibility: Enabling the Large-scale Fabrication of Plasmonic Metamaterials
The rapid advancement of science and technology have pushed the boundaries to the point where naturally occurring materials are insufficient in providing the scientists with the tools for cutting-edge development. Metamaterials, as the name implies, are materials engineered to have properties not found in nature. These remarkable properties, such as negative refractive index and artificial magnetism, are crucial in enabling scientists to perform research at a level and detail never before thought possible.
Plasmonic metamaterial is an extraordinary metamaterial that uses surface plasmons to exhibit negative real permittivity. In other words, they have optical properties that differ from and are often opposite to those of glass or air. However, the fabrication of such complex nanostructures requires difficult and expensive top-down processes, such as multiple e-beam lithography, and consequently, are practically impossible at a large-scale.
Collaborative research conducted by Professors Jin Kon Kim (NCRI Center for Block Copolymer Self-Assembly) and Junsuk Rho from the Department of Chemical Engineering at Pohang University of Science and Technology has successfully demonstrated an elegant and efficient process for the large-scale fabrication of sophisticated nanostructures that could be applied to develop metamaterials with unique optical properties. This achievement was published in the world-renowned Nature Publishing Group’s NPG Asia Materials.
The research team used a versatile and scalable process known as block copolymer (BCP) self-assembly to fabricate a high-density array of 3D nanostructures of plasmonic silver nanorods by confining lamellar nanodomains inside cylindrical anodized aluminum oxide (AAO) pores. In other words, the team used BCP self-assembly with an AAO template to create a nanostructure composed of vertically stacked ‘accordion like’ nanorods with alternating layers of plasmonic silver and PMMA over a large area. The lamellar structure allows for multiple resonances in the visible and near-infrared spectrums that could be used for multi-analyte detection.
This achievement is made even more noteworthy because the innovative process could be applied to large-scale metamaterial fabrication. Professors Kim and Rho expressed their anticipation that this novel process will be the key to overcoming a conundrum of metamaterials research and enable the cost-effective fabrication of metamaterials for multi-analyte sensing, imaging, and even invisibility.
The National Creative Research Initiative Program and the National Research Foundation of Korea supported this research.