Quasi-graphitic carbon shell-induced Cu confinement promotes electrocatalytic CO2 reduction toward C2+ products

For steady electroconversion to value-added chemical products with high efficiency, electrocatalyst reconstruction during electrochemical reactions is a critical issue in catalyst design strategies. Here, we report a reconstruction-immunized catalyst system in which Cu nanoparticles are protected by a quasi-graphitic C shell. This C shell epitaxially grew on Cu with quasi-graphitic bonding via a gas–solid reaction governed by the CO (g) - CO2 (g) - C (s) equilibrium. The quasi-graphitic C shell-coated Cu was stable during the CO2 reduction reaction and provided a platform for rational material design. C2+ product selectivity could be additionally improved by doping p-block elements. These elements modulated the electronic structure of the Cu surface and its binding properties, which can affect the intermediate binding and CO dimerization barrier. B-modified Cu attained a 68.1% Faradaic efficiency for C2H4 at −0.55 V (vs RHE) and a C2H4 cathodic power conversion efficiency of 44.0%. In the case of N-modified Cu, an improved C2+ selectivity of 82.3% at a partial current density of 329.2 mA/cm2 was acquired. Quasi-graphitic C shells, which enable surface stabilization and inner element doping, can realize stable CO2-to-C2H4 conversion over 180 h and allow practical application of electrocatalysts for renewable energy conversion. © 2021, The Author(s).1

Augmented reality-based surgical guidance for wrist arthroscopy with bone-shift compensation

Background and objectives: Intraoperative joint condition is different from preoperative CT/MR due to the motion applied during surgery, inducing an inaccurate approach to surgical targets. This study aims to provide real-time augmented reality (AR)-based surgical guidance for wrist arthroscopy based on a bone-shift model through an in vivo computed tomography (CT) study. Methods: To accurately visualize concealed wrist bones on the intra-articular arthroscopic image, we propose a surgical guidance system with a novel bone-shift compensation method using noninvasive fiducial markers. First, to measure the effect of traction during surgery, two noninvasive fiducial markers were attached before surgery. In addition, two virtual link models connecting the wrist bones were implemented. When wrist traction occurs during the operation, the movement of the fiducial marker is measured, and bone-shift compensation is applied to move the virtual links in the direction of the traction. The proposed bone-shift compensation method was verified with the in vivo CT data of 10 participants. Finally, to introduce AR, camera calibration for the arthroscope parameters was performed, and a patient-specific template was used for registration between the patient and the wrist bone model. As a result, a virtual bone model with three-dimensional information could be accurately projected on a two-dimensional arthroscopic image plane. Results: The proposed method was possible to estimate the position of wrist bone in the traction state with an accuracy of 1.4 mm margin. After bone-shift compensation was applied, the target point error was reduced by 33.6% in lunate, 63.3% in capitate, 55.0% in scaphoid, and 74.8% in trapezoid than those in preoperative wrist CT. In addition, a phantom experiment was introduced simulating the real surgical environment. AR display allowed to expand the field of view (FOV) of the arthroscope and helped in visualizing the anatomical structures around the bones. Conclusions: This study demonstrated the successful handling of AR error caused by wrist traction using the proposed method. In addition, the method allowed accurate AR visualization of the concealed bones and expansion of the limited FOV of the arthroscope. The proposed bone-shift compensation can also be applied to other joints, such as the knees or shoulders, by representing their bone movements using corresponding virtual links. In addition, the movement of the joint skin during surgery can be measured using noninvasive fiducial markers in the same manner as that used for the wrist joint. © 2022 Elsevier B.V.FALS

A Mask-Shaped Respiration Sensor Using Triboelectricity and a Machine Learning Approach toward Smart Sleep Monitoring Systems

Daily sleep monitoring is limited by the needs for specialized equipment and experts. This study combines a mask-shaped triboelectric nanogenerator (M-TENG) and machine learning for facile daily sleep monitoring without the specialized equipment or experts. The fabricated M-TENG demonstrates its excellent ability to detect respiration, even distinguishing oral and nasal breath. To increase the pressure sensitivity of the M-TENG, the reactive ion etching is conducted with different tilted angles. By investigating each surface morphology of the polytetrafluoroethylene films according to the reactive ion etching with different tilted angles, the tilted angle is optimized with the angle of 60° and the pressure sensitivity is increased by 5.8 times. The M-TENG can also detect changes in the angle of head and snoring. Various sleep stages can be classified by their distinctive electrical outputs, with the aid of a machine learning approach. As a result, a high averaged-classification accuracy of 87.17% is achieved for each sleep stage. Experimental results demonstrate that the proposed combination can be utilized to monitor the sleep stage in order to provide an aid for self-awareness of sleep disorders. Considering these results, the M-TENG and machine learning approach is expected to be utilized as a smart sleep monitoring system in near future

Intraoperative zoom lens calibration for high magnification surgical microscope

Background and objectives: An augmented reality (AR)-based surgical guidance system is often used with high-magnification zoom lens systems such as a surgical microscope, particularly in neurology or otolaryngology. To superimpose the internal structures of relevant organs on the microscopy image, an accurate calibration process to obtain the camera intrinsic and hand–eye parameters of the microscope is essential. However, conventional calibration methods are unsuitable for surgical microscopes because of their narrow depth of focus at high magnifications. To realize AR-based surgical guidance with a high-magnification surgical microscope, we herein propose a new calibration method that is applicable to the highest magnification levels as well as low magnifications. Methods: The key idea of the proposed method is to find the relationship between the focal length and the hand–eye parameters, which remains constant regardless of the magnification level. Based on this, even if the magnification changes arbitrarily during surgery, the intrinsic and hand–eye parameters are recalculated quickly and accurately with one or two pictures of the pattern. We also developed a dedicated calibration tool with a prism to take focused pattern images without interfering with the surgery. Results: The proposed calibration method ensured an AR error of < 1 mm for all magnification levels. In addition, the variation of focal length was within 1% regardless of the magnification level, and the corresponding variation with the conventional calibration method exceeded 20% at high magnification levels. Conclusions: The comparative study showed that the proposed method has outstanding accuracy and reproducibility for a high-magnification surgical microscope. The proposed calibration method is applicable to various endoscope or microscope systems with zoom lens. © 2023 Elsevier B.V.FALS

Phase Engineering of Transition Metal Dichalcogenides via a Thermodynamically Designed Gas-Solid Reaction

Polymorph conversion of transition metal dichalcogenides (TMDs) offers intriguing material phenomena that can be applied for tuning the intrinsic properties of 2D materials. In general, group VIB TMDs can have thermodynamically stable 2H phases and metastable 1T/T&apos; phases. Herein, we report key principles to apply carbon monoxide (CO)-based gas-solid reactions for a universal polymorph conversion of group VIB TMDs without forming undesirable compounds. We found that the process conditions are strongly dependent on the reaction chemical potential of cations in the TMDs, which can be predicted by thermodynamic calculations, and that polymorphic conversion is triggered by S vacancy (V-S) formation. Furthermore, we conducted DFT calculations for the reaction barriers of V-S formation and S diffusion to reveal the polymorph conversion mechanism of WS2 and compared it with that of MoS2. We believe that phase engineering 2D materials via thermodynamically designed gas-solid reactions could be functionally used to achieve defect-related nanomaterials.1

Density Functional Theory Study of Edge-Induced Atomic-Scale Structural Phase Transitions of MoS2Nanocrystals: Implications for a High-Performance Catalyst

Molybdenum disulfide (MoS2) has attracted much attention as a material to replace the noble-metal-based hydrogen evolution reaction catalyst. Polymorphism is an important factor in improving the catalytic performance of transition-metal dichalcogenides (TMDs) including MoS2. Several methods have been proposed to synthesize the 1T/1T′ phase with high catalytic efficiency, and a gas-solid reaction has recently been proposed as one of the alternative methods. However, the atomic-scale reaction mechanism between gas molecules and MoS2 has not been clarified. Here, we report a detailed atomic-scale mechanism of structural phase transition of MoS2 nanocrystals under reaction with CO gas molecules using density functional theory calculations. We confirm that the evaporation of S atoms at the edge is much faster than the evaporation at the basal plane of MoS2 nanocrystals. It is found that the S evaporation at the edge induces the structural change from 2H to 1T/1T′ in the basal plane of nanocrystals. The structural change is also attributed to the chain reaction due to the sequential migration of S atoms to the octahedral sites, which is energetically favorable. The present results provide a guideline for the gas-solid reaction-based phase control of TMDs including MoS2 to synthesize a high-performance catalyst. © 2021 American Chemical Society.1

Robust Co alloy design for Co interconnects using a self-forming barrier layer

Abstract With recent rapid increases in Cu resistivity, RC delay has become an important issue again. Co, which has a low electron mean free path, is being studied as beyond Cu metal and is expected to minimize this increase in resistivity. However, extrinsic time-dependent dielectric breakdown has been reported for Co interconnects. Therefore, it is necessary to apply a diffusion barrier, such as the Ta/TaN system, to increase interconnect lifetimes. In addition, an ultrathin diffusion barrier should be formed to occupy as little area as possible. This study provides a thermodynamic design for a self-forming barrier that provides reliability with Co interconnects. Since Cr, Mn, Sn, and Zn dopants exhibited surface diffusion or interfacial stable phases, the model constituted an effective alloy design. In the Co-Cr alloy, Cr diffused into the dielectric interface and reacted with oxygen to provide a self-forming diffusion barrier comprising Cr2O3. In a breakdown voltage test, the Co-Cr alloy showed a breakdown voltage more than 200% higher than that of pure Co. The 1.2 nm ultrathin Cr2O3 self-forming barrier will replace the current bilayer barrier system and contribute greatly to lowering the RC delay. It will realize high-performance Co interconnects with robust reliability in the future

Thermodynamically driven self-formation of Ag nanoparticles in Zn-embedded carbon nanofibers for efficient electrochemical CO2reduction

The electrochemical CO2reduction reaction (CO2RR), which converts CO2into value-added feedstocks and renewable fuels, has been increasingly studied as a next-generation energy and environmental solution. Here, we report that single-atom metal sites distributed around active materials can enhance the CO2RR performance by controlling the Lewis acidity-based local CO2concentration. By utilizing the oxidation Gibbs free energy difference between silver (Ag), zinc (Zn), and carbon (C), we can produce Ag nanoparticle-embedded carbon nanofibers (CNFs) where Zn is atomically dispersed by a one-pot, self-forming thermal calcination process. The CO2RR performance of AgZn-CNF was investigated by a flow cell with a gas diffusion electrode (GDE). Compared to Ag-CNFs without Zn species (53% at −0.85 Vvs.RHE), the faradaic efficiency (FE) of carbon monoxide (CO) was approximately 20% higher in AgZn-CNF (75% at −0.82 Vvs.RHE) with 1 M KOH electrolyte. © The Royal Society of Chemistry 2021.1

Selective hydrocarbon or oxygenate production in CO2 electroreduction over metallurgical alloy catalysts

Alloying of metals can be used to optimize intermediate binding during electrocatalysis but challenges remain in overcoming thermodynamic atomic miscibility in alloys. Here we report a coordination-controlled metal alloy in which copper clusters are spatially dispersed in a crystalline silver lattice to promote the electrochemical reduction of CO2 to ethanol. The synergistic interactions between Cu–Cu sites and Cu–Ag interfaces achieve highly selective hydrocarbon and oxygenate production by strengthening and diversifying the binding of *CO intermediates on terrace and defect sites. To control atomic coordinates beyond the miscibility limit and optimize the catalyst microstructure, sacrificial elements are incorporated with thermodynamically guided compositions to form intermetallic compounds. The sacrificial elements are then selectively dealloyed. Using a membrane electrode assembly, ethylene-selective production on copper catalysts (Faradaic efficiency, 69.6 ± 1.3%; full cell efficiency, 23.5%) is steered to ethanol-selective production on the supersaturated Ag–Cu solid-solution catalyst (Faradaic efficiency, 40.4 ± 2.4%; full cell efficiency, 14.4%). Metallurgy-designed catalyst fabrication enables the efficient chemical manufacturing of either hydrocarbons or oxygenates and offers guidelines for catalyst design principles. [Figure not available: see fulltext.]. © 2023, The Author(s), under exclusive licence to Springer Nature Limited.FALS