Mesenchymal stem cells (MSCs) are multipotent stromal cells that exist in many tissues and are capable of differentiating into several different cell types. Exogenously administered MSCs migrate to ...damaged tissue sites, where they participate in tissue repair. Their communication with the inflammatory microenvironment is an essential part of this process. In recent years, much has been learned about the cellular and molecular mechanisms of the interaction between MSCs and various participants in inflammation. Depending on their type and intensity, inflammatory stimuli confer on MSCs the ability to suppress the immune response in some cases or to enhance it in others. Here we review the current findings on the immunoregulatory plasticity of MSCs in disease pathogenesis and therapy.
Exciting advancements have been made in the field of flexible electronic devices in the last two decades and will certainly lead to a revolution in peoples’ lives in the future. However, because of ...the poor sustainability of the active materials in complex stress environments, new requirements have been adopted for the construction of flexible devices. Thus, hierarchical architectures in natural materials, which have developed various environment-adapted structures and materials through natural selection, can serve as guides to solve the limitations of materials and engineering techniques. This review covers the smart designs of structural materials inspired by natural materials and their utility in the construction of flexible devices. First, we summarize structural materials that accommodate mechanical deformations, which is the fundamental requirement for flexible devices to work properly in complex environments. Second, we discuss the functionalities of flexible devices induced by nature-inspired structural materials, including mechanical sensing, energy harvesting, physically interacting, and so on. Finally, we provide a perspective on newly developed structural materials and their potential applications in future flexible devices, as well as frontier strategies for biomimetic functions. These analyses and summaries are valuable for a systematic understanding of structural materials in electronic devices and will serve as inspirations for smart designs in flexible electronics.
The rapid development of integrated electronics and the boom in miniaturized and portable devices have increased the demand for miniaturized and on‐chip energy storage units. Currently thin‐film ...batteries or microsized batteries are commercially available for miniaturized devices. However, they still suffer from several limitations, such as short lifetime, low power density, and complex architecture, which limit their integration. Supercapacitors can surmount all these limitations. Particularly for micro‐supercapacitors with planar architectures, due to their unique design of the in‐plane electrode finger arrays, they possess the merits of easy fabrication and integration into on‐chip miniaturized electronics. Here, the focus is on the different strategies to design electrode finger arrays and the material engineering of in‐plane micro‐supercapacitors. It is expected that the advances in micro‐supercapacitors with in‐plane architectures will offer new opportunities for the miniaturization and integration of energy‐storage units for portable devices and on‐chip electronics.
In‐plane micro‐supercapacitors possess the merits of easy fabrication and integration into on‐chip electronics, and offer new opportunities for the miniaturization and integration of energy‐storage units for portable devices. Strategies to fabricate electrode finger arrays and the material engineering of in‐plane micro‐supercapacitors are discussed.
TiO2 photoredox catalysis has recently attracted much interest for use in performing challenging organic transformations under mild reaction conditions. However, the reaction scheme is hampered by ...the fact that TiO2 can only be excited by UV light of wavelengths λ shorter than 385 nm. One promising strategy to overcome this issue is to anchor an organic, preferably metal‐free dye onto the surface of TiO2. Importantly, we observed that the introduction of a catalytic amount of the redox mediator TEMPO (2,2,6,6‐tetramethylpiperidin‐1‐yl)oxyl ensured the stability of the anchored dye, alizarin red S, thereby resulting in the selective oxidation of organic sulfides with O2. This result affirms the essential role of the redox mediator in enabling the organic transformations by visible‐light photoredox catalysis.
Dye‐sensitized titanium dioxide and a catalytic amount of the redox mediator TEMPO, (2,2,6,6‐tetramethylpiperidin‐1‐yl)oxyl, served as a well‐organized scheme of photoredox catalysis for the selective oxidation of sulfides into sulfoxides using oxygen under irradiation of visible light. The redox mediator enabled the organic transformations by visible‐light‐induced photoredox catalysis.
The knowledge of mechanics of materials has been extensively implemented in developing functional materials, giving rise to recent advances in soft actuators, flexible electronics, mechanical ...metamaterials, tunable mechanochromics, regenerative mechanomedicine, etc. While conventional mechanics of materials offers passive access to mechanical properties of materials in existing forms, a paradigm shift is emerging toward proactive programming of materials’ functionality by leveraging the force–geometry–property relationships. Here, such a rising field is coined as “mechanomaterials”. To profile the concept, the design principles in this field at four scales is first outlined, namely the atomic scale, the molecular scale, the manipulation of nanoscale materials, and the microscale design of structural materials. A variety of techniques have been recruited to deliver the multiscale programming of functional mechanomaterials, such as strain engineering, capillary assembly, topological interlocking, kirigami, origami, to name a few. Engineering optical and biological functionalities have also been achieved by implementing the fundamentals of mechanochemistry and mechanobiology. Nonetheless, the field of mechanomaterials is still in its infancy, with many open challenges and opportunities that need to be addressed. The authors hope this review can serve as a modest spur to attract more researchers to further advance this field.
The emerging paradigm shift, from passive access to the mechanics of materials toward proactive functionality programming, is coined as mechanomaterials. Its rise comes with the rational deployment of force–geometry–property relationships at multiples scales, which has delivered diverse functional materials with unprecedented mechanical, optical, electrical, and biological performance, including the explosion of novel actuators, flexible electronics, mechanochromics, and mechaomedicine.
Emerging clean energy technologies such as regenerative fuel cells and rechargeable metal–air batteries have attracted increasing global interest because of their high efficiency and environmental ...benignity, but the lack of highly active bifunctional electrocatalysts at low cost for both oxygen reduction and evolution reactions (ORR and OER) greatly hinders their commercial applications. Here, we report the multilevel architecture optimization of Co-based nanoparticles (NPs) embedded in hollow N-doped carbon polyhedra for boosting the ORR and OER, which are fabricated by a two-step pyrolysis–oxidation strategy with a Co-based MOF (ZIF-67) as precursor. The key for this strategy lies in the precise and effective control of the oxidation processes of Co NPs, which enables the synthesis of a series of Co–Co3O4-based nanoarchitectures that are embedded in hollow nitrogen-doped carbon polyhedra (HNCP), including core–shell Co/Co3O4, yolk@shell Co@Co3O4, and hollow Co3O4 NPs. Benefiting from its abundant oxygen vacancies and tetrahedral Co2+ and the potential synergies of CoO x species and nitrogen-doped carbon as well as the efficient mass transfer of hollow and yolk–shell structures, the optimal yolk@shell Co3O4/HNCP-40 exhibits high activity for the OER with a low overpotential of 333 mV at 10 mA cm–2 and a small Tafel slope of 69 mV dec–1, which is better than those of commercial IrO2 (its overpotential and Tafel slope are 409 mV at 10 mA cm–2 and 104 mV dec–1, respectively). Meanwhile, the catalyst also exhibits comparable ORR catalytic activity with a half-wave potential of 0.834 V but better stability and methanol tolerance relative to commercial Pt/C (20 wt %), making it a potential bifunctional electrocatalyst for both the OER and ORR. This MOF-templated strategy for multilevel nanostructures provides insights into the development of highly efficient and low-cost bifunctional electrocatalysts for the OER/ORR.
High conductivity, large mechanical strength, and elongation are important parameters for soft electronic applications. However, it is difficult to find a material with balanced electronic and ...mechanical performance. Here, a simple method is developed to introduce ion‐rich pores into strong hydrogel matrix and fabricate a novel ionic conductive hydrogel with a high level of electronic and mechanical properties. The proposed ionic conductive hydrogel is achieved by physically cross‐linking the tough biocompatible polyvinyl alcohol (PVA) gel as the matrix and embedding hydroxypropyl cellulose (HPC) biopolymer fibers inside matrix followed by salt solution soaking. The wrinkle and dense structure induced by salting in PVA matrix provides large stress (1.3 MPa) and strain (975%). The well‐distributed porous structure as well as ion migration–facilitated ion‐rich environment generated by embedded HPC fibers dramatically enhances ionic conductivity (up to 3.4 S m−1, at f = 1 MHz). The conductive hybrid hydrogel can work as an artificial nerve in a 3D printed robotic hand, allowing passing of stable and tunable electrical signals and full recovery under robotic hand finger movements. This natural rubber‐like ionic conductive hydrogel has a promising application in artificial flexible electronics.
A simple method to introduce ion‐rich pores into a strong hydrogel matrix and fabricate a novel ionic conductive hydrogel with a high‐level performance of both electronic and mechanical properties is developed, which has great potential for stretchable electronics and artificial tissue applications.
The rise of micro‐supercapacitors is satisfying the demand for power storage in portable devices and wireless gadgets. But the miniaturization of the energy‐storage components is significantly ...limited by their energy density. Electrode materials with adequate electrochemical active surfaces are therefore required for improving performance. 2D materials with ultralarge specific surface areas offer a broad portfolio of the development of high‐performance micro‐supercapacitors in spite of their several critical drawbacks. An architecture engineering strategy is therefore developed to break these natural limits and maximize the significant advantages of these materials. Based on the approaches of phase transformation, intercalation, surface modification, material hybridization, and hierarchical structuration, 2D architectures with improved conductivity, enlarged specific surface, enhanced redox activity, as well as the unique synergetic effect exhibit great promise in the application of miniaturized supercapacitors with highly enhanced performance. Herein, the architecture engineering of emerging 2D materials beyond graphene toward optimizing the performance of micro‐supercapacitors is discussed, in order to promote the application of 2D architectures in miniaturized energy‐storage devices.
Recent advancement in 2D architecture engineering toward high‐performance micro‐supercapacitors is comprehensively reviewed. 2D materials with reduced size meet the demands of micro‐supercapacitors. Architecture engineering strategies based on phase transformation, intercalation, surface modification, material hybridization, and hierarchical structure are therefore developed to break their natural limits and maximize the significant advantages of these materials, thus opening up new opportunities to develop high‐performance miniaturized devices.
We constructed highly oriented and ordered macropores within metal-organic framework (MOF) single crystals, opening up the area of three-dimensional-ordered macro-microporous materials (that is, ...materials containing both macro- and micropores) in single-crystalline form. Our methodology relies on the strong shaping effects of a polystyrene nanosphere monolith template and a double-solvent-induced heterogeneous nucleation approach. This process synergistically enabled the in situ growth of MOFs within ordered voids, rendering a single crystal with oriented and ordered macro-microporous structure. The improved mass diffusion properties of such hierarchical frameworks, together with their robust single-crystalline nature, endow them with superior catalytic activity and recyclability for bulky-molecule reactions, as compared with conventional, polycrystalline hollow, and disordered macroporous ZIF-8.
Ti2O3 nanoparticles with high performance of photothermal conversion are demonstrated for the first time. Benefiting from the nanosize and narrow‐bandgap features, the Ti2O3 nanoparticles possess ...strong light absorption and nearly 100% internal solar–thermal conversion efficiency. Furthermore, Ti2O3‐nanoparticle‐based thin film shows potential use in seawater desalination and purification.
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