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Abstract Nanostructured 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. 

Abstract Micro- and nanoporous materials have gathered attention from the scientific community due to their size dependent properties, including but not limited to high specific surface area, surface diffusivity, bulk diffusivity and permeability, catalytic activity, and distinct optical properties. In this work, spherical nanoporous copper (np-Cu) powders, due to their nanosized porosity and low Cu2O content, show hemispherical total reflectance of 20% which is significantly lower than its bulk counterpart value for solid or molten copper of approximately 97% at wavelengths of most commercial Laser Powder Bed Fusion (L-PBF) commercial machines. The low-reflectance of np-Cu powders has the potential to be used in L-PBF to improve laser absorption, volumetric energy efficiency, and throughput of this additive manufacturing process. In fact, a prepared mixture of solid Cu powders containing only 5 wt.% of np-Cu powders reflects 34.8 % less than pure copper powders as shown in this paper. Np-Cu powders are fabricated via chemical dealloying of gas atomized CuAl alloy in a robust and scalable approach, and then mixed with pure copper powders to prepare hybrid feedstocks. Under this framework, the crucial role of deglomeration strategies to achieve homogeneity and flowability of np-Cu/Cu hybrid mixtures are evaluated via particle imaging to determine agglomerate size and composition with an eye at obtaining a high-quality print in L-PBF. In np-Cu powders fabrication, washing them in low-surface tension fluids upholds the highest degree of deglomeration in their fabrication process, and for hybrid feedstocks preparation, pre-mixing Cu and CuAl prior to dealloying yields the best homogeneity results with smallest size of agglomerates and good flowability. 

Abstract Metal‐assisted electrochemical nanoimprinting (Mac‐Imprint) scales the fabrication of micro‐ and nanoscale 3D freeform geometries in silicon and holds the promise to enable novel chip‐scale optics operating at the near‐infrared spectrum. However, Mac‐Imprint of silicon concomitantly generates mesoscale roughness (e.g., protrusion size ≈45 nm) creating prohibitive levels of light scattering. This arises from the requirement to coat stamps with nanoporous gold catalyst that, while sustaining etchant diffusion, imprints its pores (e.g., average diameter ≈42 nm) onto silicon. In this work, roughness is reduced to sub‐10 nm levels, which is in par with plasma etching, by decreasing pore size of the catalyst via dealloying in far‐from equilibrium conditions. At this level, single‐digit nanometric details such as grain‐boundary grooves of the catalyst are imprinted and attributed to the resolution limit of Mac‐Imprint, which is argued to be twice the Debye length (i.e., 1.7 nm)—a finding that broadly applies to metal‐assisted chemical etching. Last, Mac‐Imprint is employed to produce single‐mode rib‐waveguides on pre‐patterned silicon‐on‐insulator wafers with root‐mean‐square line‐edge roughness less than 10 nm while providing depth uniformity (i.e., 42.9 ± 5.5 nm), and limited levels of silicon defect formation (e.g., Raman peak shift < 0.1 cm⁻¹) and sidewall scattering.