Scalable Design of Ru-Embedded Carbon Fabric Using Conventional Carbon Fiber Processing for Robust Electrocatalysts.

Metal-carbon composites are extensively utilized as electrochemical catalysts but face critical challenges in mass production and stability. We report a scalable manufacturing process for ruthenium surface-embedded fabric electrocatalysts (Ru-SFECs) via conventional fiber/fabric manufacturing. Ru-SFECs have excellent catalytic activity and stability toward the hydrogen evolution reaction, exhibiting a low overpotential of 11.9 mV at a current density of 10 mA cm-2 in an alkaline solution (1.0 M aq KOH solution) with only a slight overpotential increment (6.5%) after 10,000 cycles, whereas under identical conditions, that of commercial Pt/C increases 6-fold (from 1.3 to 7.8 mV). Using semipilot-scale equipment, a protocol is optimized for fabricating continuous self-supported electrocatalytic electrodes. Tailoring the fiber processing parameters (tension and temperature) can optimize the structural development, thereby achieving good catalytic performance and mechanical integrity. These findings underscore the significance of self-supporting catalysts, offering a general framework for stable, binder-free electrocatalytic electrode design.

Three-dimensional Printing of Silver Microarchitectures Using Newtonian Nanoparticle Inks.

Although three-dimensional (3D) printing has recently emerged as a technology to potentially bring about the next industrial revolution, the limited selection of usable materials restricts its use to simple prototyping. In particular, metallic 3D printing with submicrometer spatial resolution is essential for the realization of 3D-printed electronics. Herein, a meniscus-guided 3D printing method that exploits a low-viscosity (∼7 mPa·s) silver nanoparticle (AgNP) ink meniscus with Newtonian fluid characteristics (which is compatible with conventional inkjet printers) to fabricate 3D silver microarchitectures is reported. Poly(acrylic acid)-capped AgNP ink that exhibits a continuous ink flow through a confined nozzle without aggregation is designed in this study. Guiding the ink meniscus with controlled direction and speed enables both vertical pulling and layer-by-layer processing, resulting in the creation of 3D microobjects with designed shapes other than those for simple wiring. Various highly conductive (>104 S·cm-1) 3D metallic patterns are demonstrated for applications in electronic devices. This research is expected to widen the range of materials that can be employed in 3D printing technology, with the aim of moving 3D printing beyond prototyping and into real manufacturing platforms for future electronics.

Three-Dimensional Printing of Highly Conductive Carbon Nanotube Microarchitectures with Fluid Ink.

Moving printed electronics to three dimensions essentially requires advanced additive manufacturing techniques yielding multifunctionality materials and high spatial resolution. Here, we report the meniscus-guided 3D printing of highly conductive multiwall carbon nanotube (MWNT) microarchitectures that exploit rapid solidification of a fluid ink meniscus formed by pulling a micronozzle. To achieve high-quality printing with continuous ink flow through a confined nozzle geometry, that is, without agglomeration and nozzle clogging, we design a polyvinylpyrrolidone-wrapped MWNT ink with uniform dispersion and appropriate rheological properties. The developed technique can produce various desired 3D microstructures, with a high MWNT concentration of up to 75 wt % being obtained via post-thermal treatment. Successful demonstrations of electronic components such as sensing transducers, emitters, and radio frequency inductors are also described herein. We expect that the technique presented in this study will facilitate selection of diverse materials in 3D printing and enhance the freedom of integration for advanced conceptual devices.