Npg Asia Materials最新文献

In this study, using the Pt/Cr₂O₃/Pt epitaxial trilayer, we demonstrate the giant voltage modulation of the antiferromagnetic spin reversal and the voltage-induced 180° switching of the Néel vector in maintaining a permanent magnetic field. We obtained a significant modulation efficiency of the switching field, Δμ₀H_SW/ΔV (Δμ₀H_SW/ΔE), reaching a maximum of −500 mT/V (−4.80 T nm/V); this value was more than 50 times greater than that of the ferromagnetic-based counterparts. From the temperature dependence of the modulation efficiency, X-ray magnetic circular dichroism measurements and first-principles calculations, we showed that the origin of the giant modulation efficiency relied on the electric field modulation of the net magnetization due to the magnetoelectric effect. From the first-principles calculation and the thickness effect on the offset electric field, we found that the interfacial magnetoelectric effect emerged. Our demonstration reveals the energy-efficient and widely applicable operation of an antiferromagnetic spin based on a mechanism distinct from magnetic anisotropy control.

Studying the properties of thermoelectric materials needs substantial effort owing to the interplay of the trade-off relationships among the influential parameters. In view of this issue, artificial intelligence has recently been used to investigate and optimize thermoelectric materials. Here, we used Bayesian optimization to improve the thermoelectric properties of multicomponent III–V materials; this domain warrants comprehensive investigation due to the need to simultaneously control multiple parameters. We designated the figure of merit ZT as the objective function to improve and search for a five-dimensional space comprising the composition of InGaAsSb thin films, dopant concentration, and film-deposition temperatures. After six Bayesian optimization cycles, ZT exhibited an approximately threefold improvement compared to its values obtained in the random initial experimental trials. Additional analysis employing Gaussian process regression elucidated that a high In composition and low substrate temperature were particularly effective at increasing ZT. The optimal substrate temperature (205 °C) demonstrated the potential for depositing InGaAsSb thermoelectric thin films onto plastic substrates. These findings not only promote the development of thermoelectric devices based on III–V semiconductors but also highlight the effectiveness of using Bayesian optimization for multicomponent materials.

The mechanism of energy loss due to magnetostriction in soft magnetic materials was analytically formulated, and our experiments validated this formulation. The viscosity of magnetic materials causes the resistive force acting on magnetic domain walls through strain due to magnetostriction, and magnetic energy is eventually dissipated by friction even without eddy currents. This energy loss mechanism explains the frequency dependence of the excess loss observed in the experiments, and the excess loss is dominated by the contribution of magnetostriction when the magnetostriction constant exceeds approximately 20 ppm. The random anisotropy model was extended by considering the effect of local magnetostriction as a correction to the magnetocrystalline anisotropy. The effect of magnetostriction was considerably suppressed by the exchange-averaging effect. The estimated effective random magnetoelastic anisotropy for nanocrystalline α-Fe reached as low as 18.6 J/m³, but this static effect could not explain the high excess loss at high frequencies observed in the experiments. The results of this research could provide new design criteria for high-performance soft magnetic materials based on low magnetostriction to reduce the excess loss.

Physical factors in the cellular microenvironment have critical effects on stem cell differentiation. The utilization of physical factors to promote the osteogenic differentiation of stem cells has been established as a new strategy for developing bone tissue engineering scaffolds. In this context, scaffolds with multiscale anisotropy are considered to possess biomimetic properties, which are advantageous for their biological performance. In the present study, a novel magnetic anisotropic hydrogel (MAH) with magnetic and topographic anisotropy was designed by combining static magnetic field-induced magnetic nanomaterials and a hydrogel. In in vitro studies, the MAH exhibited excellent biocompatibility and osteogenic bioactivity. The alkaline phosphatase activity and the expression of osteogenic-related genes and proteins induced by the MAH were greater than those induced by the pure PEGDA–GelMA hydrogel (PGH) and the magnetic isotropic hydrogel (MIH). In addition, the present study revealed that the dual anisotropic properties of the MAH activated the NOTCH1/2 pathway by upregulating SNHG5 and downstream SIRT6, which modulates the level of NOTCH1/2 by antagonizing DNMT1 protein stability, ultimately inducing the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). Furthermore, the MAH, MIH, and PGH were tested for in vivo bone regeneration in rabbits with femur defects, and the results demonstrated that the MAH effectively stimulated bone regeneration. Taken together, these findings suggest that this magnetically and topographically anisotropic biomimetic hydrogel might be a promising candidate for application in the field of bone tissue regeneration.

Magnetic skyrmions with nontrivial topologies have great potential to serve as memory cells in novel spintronic devices. Small skyrmions were theoretically and experimentally confirmed to be generated under the influence of external fields in ferrimagnetic films via Dzyaloshinskii–Moriya interactions (DMIs). However, this topological state has yet to be verified in ferrimagnetic crystals, especially in the absence of external fields and DMIs. Here, spontaneous biskyrmions were directly observed in the Tb_0.2Gd_0.8Co₂ ferrimagnetic crystal with a Kagome lattice using Lorentz transmission electron microscopy. The high-density biskyrmions exhibited a small size (approximately 50 nm) over a wide temperature range, were closely related to subtle magnetic interaction competition, and coexisted with some broken stripes that could be easily converted into zero-field biskyrmions by utilizing proper field-cooling manipulation. These results can be used to establish a platform for investigating functional sub-50-nm skyrmions in ferrimagnetic crystals and to facilitate advanced applications in magnetic devices.

Bone tissue engineering is pivotal in facilitating bone reconstruction by promoting persistent angiogenesis and osteogenesis. Initially, the hot gel composite hydrogel scaffold technique was employed. However, to address various limitations, numerous gel structures have since been developed, including osteogenic gellan gels, semi-interpenetrating network hydrogels, photoinduced crosslinking methacrylate gels, and supramolecular hydrogels. This review examines the mechanisms, formation principles, and medical benefits of these gel structures. In addition, novel bioengineering techniques to regulate human bone growth are expected to emerge in the future. This work is expected to significantly expedite the advancement of hydrogel membranes in the field of bone repair.

Here, we report the fabrication of transparent multichannel vertical nanotube electrode arrays for detecting cellular activity and optically imaging neuronal networks. To fabricate these transparent electrode arrays, position- and morphology-controlled ZnO nanotube arrays consisting of ultrathin nanowalls were grown on transparent graphene layers and coated with Ti/Au metal layers. Using these multichannel arrays, electrophysiological signals were individually recorded from primary mouse hippocampal neurons and recorded distinctive intracellular potential-like signals. Moreover, the transparent electrode array enabled fluorescence imaging of neuron cell bodies and neurite connections. This transparent graphene- and nanotube-based recording device is proposed to greatly increase the versatility of capabilities for investigating neuronal activity through simultaneous recording and imaging of neuron cultures.

Implantable medical devices have played an important role in human medicine in recent decades. However, traditional implanted devices require battery replacement and a second surgery for device removal, which can cause pain to the patient. This work presents a biodegradable triboelectric nanogenerator (BI-TENG) made from both natural and synthetic biodegradable materials that is utilized to collect mechanical energy in vivo and transduce it into electricity. Reed film and polylactic acid were chosen among different biodegradable materials as the triboelectric layers due to having the best generator output performance by providing voltages that reached 368 V. The biocompatibility of the friction layer and the device was verified via a blood test. After implantation in mice, the BI-TENG exhibited an open-circuit voltage of 0.176 V and a short-circuit current of 192 nA as generated from body movement. The BI-TENG was connected to an interdigital electrode to generate an electric field, which stimulated the accelerated release of doxorubicin (DOX) from red blood cells in targeted drug delivery systems. After stopping the electric field, the release of DOX normalized, facilitating the precise killing of cancer cells. Our work demonstrates the broad potential of BI-TENGs in the field of cancer treatment.

Cryomicroneedles (cryoMNs) offer a convenient and minimally invasive way to precisely deliver therapeutic cells intradermally for treating local and systemic diseases. cryoMNs are manufactured by shaping and freezing the cell-containing cryogenic media in a microneedle template, which allows cells to be packaged in advance for direct usage in the clinic. However, the current cryoMNs require cold-chain transportation and storage and do not permit the loading of autologous cells in situ. This article introduces the second generation of cryoMNs (S-cryoMNs) that address these limitations. Specifically, S-cryoMNs are made by dipping a porous MN scaffold in the cell suspension before cryopreservation. The porous scaffold can be transported at room temperature, and researchers can load any cells with the optimized cryogenic medium. As a proof-of-concept, we examined the loading and intradermal delivery of three cell types in clinically relevant in vitro and in vivo models, including mesenchymal stem cells for wound healing, melanocytes for vitiligo treatment, and antigen-pulsed dendritic cells for cancer vaccination.

Due to the strong interactions from multiple degrees of freedom at the interfaces, electron-correlated oxide heterostructures have provided a promising platform for creating exotic quantum states. Understanding and controlling the coupling effects at the oxide interface are prerequisites for designing emergent interfacial phases with desired functionalities. Here, we report the dimensional control of the interface coupling-induced ferromagnetic (FM) phase in perovskite-CaRuO₃/infinite-layered-SrCuO₂ superlattices. Structural analysis reveals the occurrence of chain-type to planar-type structural transitions for the SrCuO₂ layer as the layer thickness increases. The Hall and magnetoresistance measurements indicate the appearance of an interfacial FM state in the originally paramagnetic CaRuO₃ layers when the CaRuO₃ layer is in proximity to the chain-type SrCuO₂ layers; this superlattice has the highest Curie temperature of ~75 K and perpendicular magnetic anisotropy. Along with the thickness-driven structural transition of the SrCuO₂ layers, the interfacial FM order gradually deteriorates and finally disappears. As shown by the X-ray absorption results, the charge transfer at the CaRuO₃/chain-SrCuO₂ and CaRuO₃/plane-SrCuO₂ interfaces are different, resulting in dimensional control of the interfacial magnetic state. The results from our study can be used to facilitate a new method to manipulate interface coupling and create emergent interfacial phases in oxide heterostructures.