Liyang Chen

This work details the combination of displacement Talbot lithography, deep reactive dry etching of silicon, and bottom-up gold electrochemical deposition to produce void-free gold microgratings with 700 nm wide Au lines of 27 μm depth, corresponding to an aspect ratio (depth/width) of 38 with vertical sidewall. Systematic optimization of the grating design and manufacturing processes yielded high-quality sub-micrometer gold gratings with precisely controlled structural profiles, minimal deviation of the duty cycle as a function of depth and absence of voids in the Au filling. A symmetric X-ray grating interferometer at 20 keV design energy with 1.2 μm pitch gratings showcases the application.

The escalating demand for wearable electrodes in the era of digital healthcare underscores the urgent need for more efficient and accurate biopotential monitoring techniques. Here, we report a scalable and facile approach to the fabrication of microneedle electrodes (MNEs) for accurate and imperceptible biopotential monitoring, leveraging a unique micro/nanoelectroforming technique. We exploited magnetron sputtering of indium tin oxide on an inverse-microneedle mold and subsequent electrodeposition of metal layers to produce ultrathin, flexible, and highly conductive MNEs. These MNEs outperformed the planar metal electrodes and commercial silver/silver chloride gel electrodes. The microstructured surface of MNEs increases the contact area and bypasses sweat and grease on uneven skin surfaces, leading to lower electrode-skin interface impedance. This innovative design enhances the signal-to-noise ratio, enabling more accurate and noninvasive detection of electrophysiological signals, such as electromyograms and electrocardiograms. In addition, the MNEs exhibited superior mechano-electrical stability, biocompatibility, and comfort, making them suitable for long-term healthcare monitoring and human-robot interactions. This work illuminates a pathway toward more reliable and adaptable biopotential monitoring technologies.

Precise micropatterning on three-dimensional (3D) surfaces is desired for a variety of applications, from microelectronics to metamaterials, which can be realized by transfer printing techniques. However, a nontrivial deficiency of this approach is that the transferred microstructures are adsorbed on the target surface with weak adhesion, limiting the applications to external force-free conditions. We propose a scalable "photolithography-transfer-plating" method to pattern stable and durable microstructures on 3D metallic surfaces with precise dimension and location control of the micropatterns. Surface patterning on metallic parts with different metals and isotropic and anisotropic curvatures is showcased. This method can also fabricate hierarchical structures with nanoscale vertical and microscale horizontal dimensions. The plated patterns are stable enough to mold soft materials, and the structure durability is validated by 24 h thermofluidic tests. We demonstrate micropatterned nickel electrodes for oxygen evolution reaction acceleration in hydrogen production, showing the potential of micropatterned 3D metallic surfaces for energy applications.

Soft transparent electrodes (TEs) have received tremendous interest from academia and industry due to the rapid development of lightweight, transparent soft electronics. Metallic micro‐nano networks (MMNNs) are a class of promising soft TEs that exhibit excellent optical and electrical properties, including low sheet resistance and high optical transmittance, as well as superior mechanical properties such as softness, robustness, and desirable stability. They are genuinely interesting alternatives to conventional conductive metal oxides, which are expensive to fabricate and have limited flexibility on soft surfaces. This review summarizes state‐of‐the‐art research developments in MMNN‐based soft TEs in terms of performance specifications, fabrication methods, and application areas. The review describes the implementation of MMNN‐based soft TEs in optoelectronics, bioelectronics, tactile sensors, energy storage devices, and other applications. Finally, it presents a perspective on the technical difficulties and potential future possibilities for MMNN‐based TE development.

This study investigates low bend loss in terahertz photonic crystal waveguides by analyzing their transmission characteristics with different bending radii and geometries, as well as exploring the impact of various structural parameters. Results demonstrate that optimizing the structure can significantly reduce bend loss, and a novel topological PCW design is proposed. The study compares Rib and regular waveguides, circular and rectangular lattices, and introduces a hexagonal cell design based on C6(sixfold rotational symmetry) chiral symmetry that can effectively reduce bending losses. These findings provide valuable insights for the design and optimization of photonic crystal waveguides in terahertz applications, with promising applications in sensing, imaging, and communication.