High‐Performance Doped Silver Films: Overcoming Fundamental Material Limits for Nanophotonic Applications

The field of nanophotonics has ushered in a new paradigm of light manipulation by enabling deep subdiffraction confinement assisted by metallic nanostructures. However, a key limitation which has stunted a full development of high‐performance nanophotonic devices is the typical large losses associated with the constituent metals. Although silver has long been known as the highest quality plasmonic material for visible and near infrared applications, its usage has been limited due to practical issues of continuous thin film formation, stability, adhesion, and surface roughness. Recently, a solution is proposed to the above issues by doping a proper amount of aluminum during silver deposition. In this work, the potential of doped silver for nanophotonic applications is presented by demonstrating several high‐performance key nanophotonic devices. First, long‐range surface plasmon polariton waveguides show propagation distances of a few centimeters. Second, hyperbolic metamaterials consisting of ultrathin Al‐doped Ag films are attained having a homogeneous and low‐loss response, and supporting a broad range of high‐k modes. Finally, transparent conductors based on Al‐doped Ag possess both a high and flat transmittance over the visible and near‐IR range.     

Fabrication of High‐Performance Silver Mesh for Transparent Glass Heaters via Electric‐Field‐Driven Microscale 3D Printing and UV‐Assisted Microtransfer

Great challenges remain concerning the cost‐effective manufacture of high‐performance metal meshes for transparent glass heaters (TGHs). Here, a high‐performance silver mesh fabrication technique is proposed for TGHs using electric‐field‐driven microscale 3D printing and a UV‐assisted microtransfer process. The results show a more optimal trade‐off in sheet resistance (R_s = 0.21 Ω sq^?1) and transmittance (T = 93.9%) than for indium tin oxide (ITO) and ITO substitutes. The fabricated representative TGH also exhibits homogeneous and stable heating performance, remarkable environmental adaptability (constant R_s for 90 days), superior mechanical robustness (R_s increase of only 0.04 in harsh conditions–sonication at 100 °C), and strong adhesion force with a negligible increase in R_s (2–12%) after 100 peeling tests. The practical viability of this TGH is successfully demonstrated with a deicing test (ice cube: 21 cm³, melting time: 78 s, voltage and glass thickness: 4 V, 5 mm). All of these advantages of the TGHs are attributed to the successful fabrication of silver meshes with high resolution and high aspect ratio on the glass substrate using the thick film silver paste. The proposed technique is a promising new tool for the inexpensive fabrication of high‐performance TGHs.     

Light‐Induced Buckles Localized by Polymeric Inks Printed on Bilayer Films

Buckling instabilities generate microscale features in thin films in a facile manner. Buckles can form, for example, by heating a metal/polymer film stack on a rigid substrate. Thermal expansion differences of the individual layers generate compressive stress that causes the metal to buckle over the entire surface. The ability to dictate and confine the location of buckle formation can enable patterns with more than one length scale, including hierarchical patterns. Here, sacrificial “ink” patterned on top of the film stack localizes the buckles via two mechanisms. First, stiff inks suppress buckles such that only the non‐inked regions buckle in response to infrared light. The metal in the non‐inked regions absorbs the infrared light and thus gets sufficiently hot to induce buckles. Second, soft inks that absorb light get hot faster than the non‐inked regions and promote buckling when exposed to visible light. The exposed metal in the non‐inked regions reflects the light and thus never get sufficiently hot to induce buckles. This second method works on glass substrates, but not silicon substrates, due to the superior thermal insulation of glass. The patterned ink can be removed, leaving behind hierarchical patterns consisting of regions of buckles among non‐buckled regions.     

Screen‐printed gold thick films for electrochemical sensor applications

Screen‐printed gold electrodes have been assembled in Low Temperature Co‐fired Ceramics technology and characterised and tested for applications in electrochemical analytics. They were investigated by scanning electron microscopy and by cyclovoltammetry in sulphuric acid and of typical redox couples such as hexacyanoferrate and quinhydrone. The electrodes differ in surface morphology, microstructure with the formation of preferential crystal orientation and exhibit different real surface sizes depending on the chosen gold paste. After pre‐treatment in sulphuric acid an almost reversible behaviour can be achieved however differences between the thick films occur at high scan rates and especially with quinhydrone. Differences in the sensitivity of the thick films at low analyte concentration can be explained by their surface properties.