Conjugated polymers (CPs), organic macromolecules with a linear backbone of alternating C–C and C=C bonds, possess unique semiconductive properties, providing new opportunities for organic electronics, photonics, information, and energy devices. Seeking the metallic or metallic-like, even superconducting properties beyond semiconductivity in CPs is always one of the ultimate goals in polymer science and condensed matter. Only two metallic and semi-metallic transport cases—aniline-derived polyaniline and thiophene-derived poly(3,4-ethylenedioxythiophene)—have been reported since the development of CPs for four decades. Controllable synthesis is a key challenge in discovering more cases. Here we report the metallic-like transport behavior of another CP, polypyrrole (PPy). We observe that the transport behavior of PPy changes from semiconductor to insulator-metal transition, and gradually realizes metallic-like performance when the crystalline degree increases. Using a generalized Einstein relation model, we rationalized the mechanism behind the observation. The metallic-like transport in PPy demonstrates electron strong correlation and phonon–electron interaction in soft condensation matter, and may find practical applications of CPs in electrics and spintronics.

Metallic glasses (MGs) or amorphous alloys are an important engineering material that has a history of research of about 80–90 years. While different fast cooling methods were developed for multi-component MGs between 1960s and 1980s, 1990s witnessed a surge of research interest in the development of bulk metallic glasses (BGMs). Since then, one central theme of research in the metallic-glass community has been compositional design that aims to search for MGs with a better glass forming ability, a larger size and/or more interesting properties, which can hence meet the demands from more important applications. In this review article, we focus on the recent development of chemically complex MGs, such as high entropy MGs, with new tools that were not available or mature yet until recently, such as the state-of-the-art additive manufacturing technologies, high throughput materials design techniques and the methods for big data analyses (e.g. machine learning and artificial intelligence). We also discuss the recent use of MGs in a variety of novel and important applications, from personal healthcare, electric energy transfer to nuclear energy that plays a pivotal role in the battle against global warming.

In the crucial area of sustainable energy storage, solid-state batteries (SSBs) with nonflammable solid electrolytes stand out due to their potential benefits of enhanced safety, energy density, and cycle life. However, the complexity within the composite cathode determines that fabricating an ideal electrode needs to link chemistry (atomic scale), materials (microscopic/mesoscopic scale), and electrode system (macroscopic scale). Therefore, understanding solid-state composite cathodes covering multiple scales is of vital importance for the development of practical SSBs. In this review, the challenges and basic knowledge of composite cathodes from the atomic scale to the macroscopic scale in SSBs are outlined with a special focus on the interfacial structure, charge transport, and mechanical degradation. Based on these dilemmas, emerging strategies to design a high-performance composite cathode and advanced characterization techniques are summarized. Moreover, future perspectives toward composite cathodes are discussed, aiming to facilitate the develop energy-dense SSBs.

Since being rediscovered as an emerging 2D material, black phosphorus (BP), with an extraordinary energy structure and unusually strong interlayer interactions, offers new opportunities for optoelectronics and photonics. However, due to the thin atomic body and the ease of degradation with water and oxides, BP is highly sensitive to the surrounding environment. Therefore, high-quality engineering of interfaces and surfaces plays an essential role in BP-based applications. In this review, begun with a review of properties of BP, different strategies of interface and surfaces engineering for high ON-OFF ratio, enhanced optical absorption, and fast optical response are reviewed and highlighted, and recent state-of-the-art advances on optoelectronic and photonic devices are demonstrated. Finally, the opportunities and challenges for future BP-related research are considered.

Micro/nanomaterial-based drug and cell delivery systems play an important role in biomedical fields for their injectability and targeting. Microfluidics is a rapidly developing technology and has become a robust tool for preparing biomaterial micro/nanocarriers with precise structural control and high reproducibility. By flexibly designing microfluidic channels and manipulating fluid behavior, various forms of biomaterial carriers can be fabricated using microfluidics, including microspheres, nanoparticles and microfibers. In this review, recent advances in biomaterials for designing functional microfluidic vehicles are summarized. We introduce the application of natural materials such as polysaccharides and proteins as well as synthetic polymers in the production of microfluidic carriers. How the material properties determine the manufacture of carriers and the type of cargoes to be encapsulated is highlighted. Furthermore, the current limitations of microfluidic biomaterial carriers and perspectives on its future developments are presented.

This vision summarizes the recent advancement of nanostructured steels for advanced structural applications, foresees possible challenges and pinpoints future directions as well as opportunities in this new era of industrial revolution 4.0.

3D printing is nowadays used for many applications far beyond pure rapid prototyping. As tools to prepare custom-made objects which may be highly complex, different 3D printing techniques have emerged into areas of application where the mechanical, thermal, optical and other properties have to meet high requirements. Amongst them, applications for space, e.g. for microsatellites, make extreme demands regarding the stability under high temperatures. Nevertheless, polymeric 3D printed materials have several advantages for space application in comparison with metal objects. Here we thus investigate the impact of temperatures up to 85 °C and 185 °C, respectively, on typical 3D printing materials for fused deposition modeling or stereolithography (SLA) with inexpensive 3D printers. The materials are found to differ strongly in terms of mechanical properties and dimensional stability after the treatment at a higher temperature, with SLA resins and co-polyester showing the best dimensional stability, while acrylonitrile–butadiene–styrene and SLA resin after long UV post-treatment has the best mechanical properties.

High-capacity and high-rate anode materials are desperately desired for applications in the next generation lithium-ion batteries. Here, we report preparation of an anode showing a structure of Si nanoparticles wrapped inside Sn nanowires. This anode inherits the advantages of both Si and Sn, endowing lithiation/delithiation of Si nanoparticles inside the conducting networks of Sn nanowires. It demonstrates a high and reversible capacity of ~1500 mAh g^-1 over 300 cycles at 0.2℃ and a good rate capability (0.2℃-5℃) equivalent to Sn. The excellent cycling performance is attributed to the novel structure of the anode as well as the strong mechanical strength of the nanowires which is directly confirmed by in-situ lithiation and bending experiments.

Solid-state batteries (SSBs) are a promising next step in electrochemical energy storage but are plagued by a number of problems. In this study, we demonstrate the recurring issue of mechanical degradation because of volume changes in layered Ni-rich oxide cathode materials in thiophosphate-based SSBs. Specifically, we explore superionic solid electrolytes of different crystallinity, namely glassy 1.5Li₂S-0.5P₂S₅-LiI and argyrodite Li₆PS₅Cl, with emphasis on how they affect the cyclability of slurry-cast cathodes with NCM622 (60% Ni) or NCM851005 (85% Ni). The application of a combination of ex situ and in situ analytical techniques helped to reveal the benefits of using a solid electrolyte with a low Young's modulus. Through a synergistic interplay of (electro)chemical and (chemo)mechanical effects, the glassy solid electrolyte employed in this work was able to achieve robust and stable interfaces, enabling intimate contact with the cathode material while at the same time mitigating volume changes. Our results emphasize the importance of considering chemical, electrochemical, and mechanical properties to realize long-term cycling performance in high-loading SSBs.

Perovskite quantum dots (PeQDs) are considered potential display materials due to their high color purity, high photoluminescence quantum yield (PLQY), low cost and easy film casting. In this work, a novel electroluminescence (EL) device consisting of the interface layer of long alkyl-based oleylammonium bromide (OAmBr), which passivates the surface defects of PeQDs and adjusts the carrier transport properties, was designed. The PLQY of the OAmBr/PeQD bilayer was significantly improved. A high-performance EL device with the structure of indium tin oxide/poly(3,4-ethylenedioxythiophene) polystyrene sulfonate/poly(bis(4-phenyl)(2,4,6-trimethylphenyl)amine)/OAmBr/PeQDs/2,2^′,2^′′-(1,3,5-benzinetriyl)-tris(1-phenyl-1H benzimidazole)/LiF/Al was constructed using a spin-coating method. A peak external quantum efficiency (EQE) of 16.5% at the emission wavelength of 646 nm was obtained. Furthermore, an efficient matrix EL device was fabricated using an inkjet printing method. A high-quality PeQD matrix film was obtained by introducing small amounts of polybutene into the PeQDs to improve the printing process. The EQE reached 9.6% for the matrix device with 120 pixels per inch and the same device structure as that of the spin-coating one.

Biomimetic scaffolds with extracellular matrix (ECM)-mimicking structure have been widely investigated in wound healing applications, while insufficient mechanical strength and limited biological activity remain major challenges. Here, we present a microfluidic 3D printing biomimetic polyhydroxyalkanoates-based scaffold with excellent mechanical properties and hierarchical porous structures for enhanced wound healing. This scaffold is composed of poly(3-hydroxybutyrate-4-hydroxybutyrate) and polycaprolactone, endowing it with excellent tensile strength (2.99 MPa) and degradability (80% of weight loss within 7 d). The ECM-mimicking hierarchical porous structure allows bone marrow mesenchymal stem cells (BMSCs) and human umbilical vein endothelial cells (HUVECs) to proliferate and adhere on the scaffolds. Besides, anisotropic composite scaffolds loaded with BMSCs and HUVECs can significantly promote re-epithelization, collagen deposition and capillary formation in rat wound defects, indicating their satisfactory in vivo tissue regenerative activity. These results indicate the feasibility of polyhydroxyalkanoates-based biomimetic scaffolds for skin repair and regeneration, which also provide a promising therapeutic strategy in diverse tissue engineering applications.