Conformal Electrochemical Nanoimprinting of Silicon: Toward Bio‐Inspired Hierarchical Infrared Meta‐Optics

Abstract

AbstractNanostructured anti‐reflection metasurfaces for infrared lenses are designed for imaging in harsh environments such as dust (e.g., moon or battlefield), micrometeorites (e.g., Lagrange points), and high‐radiation fluctuations (e.g., Mars) with limited lifetimes. These multifunctional optical meta‐surfaces (MOMS) simultaneously deliver high thermal stability and anti‐fouling behavior due to their monolithic nature (e.g., no mismatch in the coefficient of thermal expansion), hydrophobicity, and low dust adherence. However, the incompatibility of inorganic semiconductor micromachining with non‐planar substrates has limited MOMS to polymeric and glass lenses. Here, a new method of conformal electrochemical nanoimprinting is presented to directly micromachine a nature‐inspired MOMS onto a silicon lens. Uniquely, stretchablegold‐coated patterned porous PVDF stamps are made by lithographically templated thermally induced phase separation (lt‐TIPS), which simultaneously embeds it with (i) interconnected porosity for promoting mass transport, (ii) HF‐resistance for increasing operational lifetime, and (iii) stretchable electronic nanocoatings (i.e., Au) that can catalyze the electrochemical process. In a demonstration of its hierarchical micromachining capability, a sharklet microscale pattern is successfully transferred to a silicon lens with anti‐reflective and hydrophobic properties. This work paves the way for MOMS’ extension onto inorganic semiconductors and IR lenses.