Scalable Dry Process for Fabricating a Na Superionic Conductor-Type Solid Electrolyte Sheet

The cost reduction and mass production of oxide-based solid electrolytes are critical for the commercialization of all-solid-state batteries. In this study, an environmentally friendly, low-cost, and high-density oxide-based Na superionic conductor-type solid electrolyte sheet was fabricated via a dry process without the use of any solvent. The polytetrafluoroethylene (PTFE), used as a binder, was transformed into thin thread-like structures via shear force, resulting in a flexible solid electrolyte sheet. The solid electrolyte powder quantity was limited to 50 wt % for fabricating a uniform green sheet via the wet process. However, when the dry process was employed for green sheet fabrication, the solid electrolyte powder quantity could be increased to values exceeding 95 wt %. Therefore, the green sheets produced by using the dry process demonstrated a higher density than those fabricated by using the wet process. The binder content and particle size affected the ionic conductivity of a solid electrolyte sheet fabricated via a dry process. The sheet obtained via the blending of 3 wt % PTFE binder with a solid electrolyte powder, finely ground using a planetary ball mill, which exhibited the highest total ionic conductivity of 1.03 mS cm–1

Electronic Properties of Cu_2–<i>x</i>Se Nanocrystal Thin Films Treated with Short Ligand (S^2–, SCN^–, and Cl^–) Solutions

To exploit interesting electronic properties of colloidal semiconductor nanocrystals (NCs) in thin film devices, replacement of the original bulky ligands attached on the NC surface to short ones is essential. Here, we investigate the electronic properties of thin films of Cu2–xSe NCs treated chemically with short sulfide (S2–), thiocyanate (SCN–), and chloride (Cl–) ligands that are known to yield superior physical properties compared to the first-generation short ligand systems including amines and thioles. Specifically, the study focuses on the impact of ligand treatment on their direct/indirect bandgap and NIR-localized surface plasmon resonance (LSPR) in the near-IR regime as well as their electrical conductivity and thermoelectric properties. While the application of S2– solution resulted in exchange of the original oleylamine (OAm) on NC surface with S2– ligands, use of SCN– and Cl– solutions only removed the original ligands. The different ligands consistently led a red-shift of the direct and indirect bandgap. The LSPR was also red-shifted after applying solutions with SCN– and Cl– but was blue-shifted after applying solutions with S2–, which we attribute to the formation of sulfur shell on NC surface. Conductivity as high as 442 S/cm and Seebeck coefficient of 13 μV/K could be obtained from the NC films with Cl– and SCN– ligands, respectively. We believe that the understanding on Cu2–xSe NCs will expand the materials library for electronic applications of copper chalcogenide NCs

4D Printing of Ultrastretchable Magnetoactive Soft Material Architectures for Soft Actuators

Magnetoactive soft materials (MSMs) comprising magnetic particles and soft matrices have emerged as smart materials for realizing soft actuators. 4D printing, which involves fabricating 3D architectures that can transform shapes under external magnetic fields, is an effective way to fabricate MSMs-based soft actuators with complex shapes. The printed MSMs must be flexible, stretchable, and adaptable in their magnetization profiles to maximize the degrees of freedom for shape morphing. This study utilizes a facile 4D printing strategy for producing ultrastretchable (stretchability > 1000%) MSM 3D architectures for soft-actuator applications. The strategy involves two sequential steps: (i) direct ink writing (DIW) of the MSM 3D architectures with ink composed of NdFeB and styrene-isoprene block copolymers (SIS) at room temperature and (ii) programming and reconfiguration of the magnetization profiles of the printed architecture using an origami-inspired magnetization method (magnetization field, Hm = 2.7 T). Various differently shaped MSM 3D architectures, which can be transformed into desired shapes under an actuation magnetic field (Ba = 85 mT), are successfully fabricated. In addition, two different soft-actuator applications are demonstrated: a multifinger magnetic soft gripper and a Kirigami-shaped 3D electrical switch with conductive and magnetic functionalities. Our strategy shows potential for realizing multifunctional, shape-morphing, and reprogrammable magnetoactive devices for advanced soft-actuator applications

In Situ Analyses of Carbon Dissolution into Ni-YSZ Anode Materials

A combination of in situ analyses, including measurement of both electrical resistance and volumetric expansion, and thermogravimetric analysis (TGA) was employed to elucidate the deactivation process of a nickel-yttria-stabilized zirconia (Ni-YSZ) cermet (60 wt % NiO-YSZ) upon exposure to methane at 750 °C. In conjunction with the aforementioned in situ techniques, a number of ex situ analyses, including scanning electron microscopy (SEM), electron probe microanalysis (EPMA), X-ray diffraction (XRD), and Raman spectroscopy, revealed that carbon deposition initially occurred at the Ni centers, followed by carbon dissolution into the Ni-YSZ cermet after an induction period of 200 min, which then led to three-dimensional expansion. The structural change of the Ni-based cermet induced increases in electrical resistance of the material. The increased electrical resistance likely originated from the breakage of the Ni–Ni conducting network as well as from the formation of microscopic cracks within the Ni-YSZ material, resulting from the observed process of carbon dissolution. Moreover, a combination of TGA involving measurements of electrical resistance was demonstrated to be useful for determining amounts of carbon deposits critical for carbon dissolution. These results strongly suggest that changes in electrical resistance can be utilized to monitor the extent of carbon dissolution into the Ni-YSZ catalysts in situ, which would be helpful for the development of an efficient curing system for solid oxide fuel cells (SOFCs)

4D Printing of Ultrastretchable Magnetoactive Soft Material Architectures for Soft Actuators

Magnetoactive soft materials (MSMs) comprising magnetic particles and soft matrices have emerged as smart materials for realizing soft actuators. 4D printing, which involves fabricating 3D architectures that can transform shapes under external magnetic fields, is an effective way to fabricate MSMs-based soft actuators with complex shapes. The printed MSMs must be flexible, stretchable, and adaptable in their magnetization profiles to maximize the degrees of freedom for shape morphing. This study utilizes a facile 4D printing strategy for producing ultrastretchable (stretchability > 1000%) MSM 3D architectures for soft-actuator applications. The strategy involves two sequential steps: (i) direct ink writing (DIW) of the MSM 3D architectures with ink composed of NdFeB and styrene-isoprene block copolymers (SIS) at room temperature and (ii) programming and reconfiguration of the magnetization profiles of the printed architecture using an origami-inspired magnetization method (magnetization field, Hm = 2.7 T). Various differently shaped MSM 3D architectures, which can be transformed into desired shapes under an actuation magnetic field (Ba = 85 mT), are successfully fabricated. In addition, two different soft-actuator applications are demonstrated: a multifinger magnetic soft gripper and a Kirigami-shaped 3D electrical switch with conductive and magnetic functionalities. Our strategy shows potential for realizing multifunctional, shape-morphing, and reprogrammable magnetoactive devices for advanced soft-actuator applications

4D Printing of Ultrastretchable Magnetoactive Soft Material Architectures for Soft Actuators

Magnetoactive soft materials (MSMs) comprising magnetic particles and soft matrices have emerged as smart materials for realizing soft actuators. 4D printing, which involves fabricating 3D architectures that can transform shapes under external magnetic fields, is an effective way to fabricate MSMs-based soft actuators with complex shapes. The printed MSMs must be flexible, stretchable, and adaptable in their magnetization profiles to maximize the degrees of freedom for shape morphing. This study utilizes a facile 4D printing strategy for producing ultrastretchable (stretchability > 1000%) MSM 3D architectures for soft-actuator applications. The strategy involves two sequential steps: (i) direct ink writing (DIW) of the MSM 3D architectures with ink composed of NdFeB and styrene-isoprene block copolymers (SIS) at room temperature and (ii) programming and reconfiguration of the magnetization profiles of the printed architecture using an origami-inspired magnetization method (magnetization field, Hm = 2.7 T). Various differently shaped MSM 3D architectures, which can be transformed into desired shapes under an actuation magnetic field (Ba = 85 mT), are successfully fabricated. In addition, two different soft-actuator applications are demonstrated: a multifinger magnetic soft gripper and a Kirigami-shaped 3D electrical switch with conductive and magnetic functionalities. Our strategy shows potential for realizing multifunctional, shape-morphing, and reprogrammable magnetoactive devices for advanced soft-actuator applications

Meniscus-on-Demand Parallel 3D Nanoprinting

Exploiting a femtoliter liquid meniscus formed on a nanopipet is a powerful approach to spatially control mass transfer or chemical reaction at the nanoscale. However, the insufficient reliability of techniques for the meniscus formation still restricts its practical use. We report on a noncontact, programmable method to produce a femtoliter liquid meniscus that is utilized for parallel three-dimensional (3D) nanoprinting. The method based on electrohydrodynamic dispensing enables one to create an ink meniscus at a pipet–substrate gap without physical contact and positional feedback. By guiding the meniscus under rapid evaporation of solvent in air, we successfully fabricate freestanding polymer 3D nanostructures. After a quantitative characterization of the experimental conditions, we show that we can use a multibarrel pipet to achieve parallel fabrication process of clustered nanowires with precise placement. We expect this technique to advance productivity in nanoscale 3D printing

MoSe₂ Embedded CNT-Reduced Graphene Oxide Composite Microsphere with Superior Sodium Ion Storage and Electrocatalytic Hydrogen Evolution Performances

Highly porous MoSe2-reduced graphene oxide-carbon nanotube (MoSe2-rGO-CNT) powders were prepared by a spray pyrolysis process. The synergistic effect of CNTs and rGO resulted in powders containing ultrafine MoSe2 nanocrystals with a minimal degree of stacking. The initial discharge capacities of MoSe2-rGO-CNT, MoSe2-CNT, MoSe2-rGO, and bare MoSe2 powders for sodium ion storage were 501.6, 459.7, 460.2, and 364.0 mA h g–1, respectively, at 1.0 A g–1. The MoSe2-rGO-CNT composite powders had superior cycling and rate performances compared with the MoSe2-CNT, MoSe2-rGO composite, and bare MoSe2 powders. The electrocatalytic activity of MoSe2-rGO-CNT in the hydrogen evolution reaction (HER) was also compared with that of MoSe2-CNT, MoSe2-rGO, and bare MoSe2. MoSe2-rGO-CNT composite powders exhibited an overpotential of 0.24 V at a current density of 10 mA cm–2, which was less than that of MoSe2-CNT (0.26 V at 10 mA cm–2), MoSe2-rGO (0.32 V at 10 mA cm–2), and bare MoSe2 (0.33 V at 10 mA cm–2). Tafel slopes for the MoSe2-rGO-CNT, MoSe2-CNT, MoSe2-rGO, and bare MoSe2 powders were 53, 76, 86, and 115 mV dec–1, respectively. Because a large electrochemical surface area and ultrafine MoSe2 nanocrystals, the MoSe2-rGO-CNT composite possesses more active sites than the MoSe2-CNT, MoSe2-rGO composite, and bare MoSe2 powders with extensive stacking and large crystalline size, which provide greater catalytic HER activity

Meniscus-on-Demand Parallel 3D Nanoprinting

Exploiting a femtoliter liquid meniscus formed on a nanopipet is a powerful approach to spatially control mass transfer or chemical reaction at the nanoscale. However, the insufficient reliability of techniques for the meniscus formation still restricts its practical use. We report on a noncontact, programmable method to produce a femtoliter liquid meniscus that is utilized for parallel three-dimensional (3D) nanoprinting. The method based on electrohydrodynamic dispensing enables one to create an ink meniscus at a pipet–substrate gap without physical contact and positional feedback. By guiding the meniscus under rapid evaporation of solvent in air, we successfully fabricate freestanding polymer 3D nanostructures. After a quantitative characterization of the experimental conditions, we show that we can use a multibarrel pipet to achieve parallel fabrication process of clustered nanowires with precise placement. We expect this technique to advance productivity in nanoscale 3D printing

4D Printing of Ultrastretchable Magnetoactive Soft Material Architectures for Soft Actuators

Magnetoactive soft materials (MSMs) comprising magnetic particles and soft matrices have emerged as smart materials for realizing soft actuators. 4D printing, which involves fabricating 3D architectures that can transform shapes under external magnetic fields, is an effective way to fabricate MSMs-based soft actuators with complex shapes. The printed MSMs must be flexible, stretchable, and adaptable in their magnetization profiles to maximize the degrees of freedom for shape morphing. This study utilizes a facile 4D printing strategy for producing ultrastretchable (stretchability > 1000%) MSM 3D architectures for soft-actuator applications. The strategy involves two sequential steps: (i) direct ink writing (DIW) of the MSM 3D architectures with ink composed of NdFeB and styrene-isoprene block copolymers (SIS) at room temperature and (ii) programming and reconfiguration of the magnetization profiles of the printed architecture using an origami-inspired magnetization method (magnetization field, Hm = 2.7 T). Various differently shaped MSM 3D architectures, which can be transformed into desired shapes under an actuation magnetic field (Ba = 85 mT), are successfully fabricated. In addition, two different soft-actuator applications are demonstrated: a multifinger magnetic soft gripper and a Kirigami-shaped 3D electrical switch with conductive and magnetic functionalities. Our strategy shows potential for realizing multifunctional, shape-morphing, and reprogrammable magnetoactive devices for advanced soft-actuator applications