Electrochemical supercapacitors process ultra–high power density and long lifetime, but the relatively low energy density hinder the wide application. Therefore, supercapacitors with high energy density and high power density (“dual high”) have attracted great attentions. New active materials with high pseudocapacitance beyond electronic double layer capacitance and novel devices with high working voltage, are two approaches toward “dual high” supercapacitors. In this review, we briefly introduce the history, classification, basic mechanism, and device architecture of supercapacitors. Then, the key issues and design strategies for “dual high” supercapacitors will be proposed. The recent methodical advances will also be highlighted on the material with outstanding specific capacitance and the corresponding electrolyte systems with expanded operating voltage. Besides, the recent progresses of current collectors and separators for supercapacitors are also included. Finally, we will provide our insights regarding the major challenges and prospective solutions in this highly exciting field. We believe such a review will significantly expand the horizons in ever-deepening understanding toward “dual high” supercapacitors

Mechanically stretchable optoelectronic devices have provided unprecedented advantages for modern society, with the development of the Internet of Things. Stretchable organic optoelectronic devices have recently emerged as promising candidates for next-generation human-friendly wearable devices and sensors. The combination of facile and cost-effective processing accessibility has triggered the rapid development of stretchable electronic materials and devices. This review presents some recent advances and remaining challenges in the field of stretchable organic optoelectronics. Specifically, it focuses on advanced approaches, including appropriate material selection and structure engineering, to build stretchable optoelectronic devices while also preserving their photonic/electrical performances under external mechanical stresses. In addition, the potential challenges and their corresponding response strategies are discussed for further development of functional devices. We anticipate that this review will inspire more studies that assist in expanding the practical applications and potential of stretchable optoelectronic devices in wearables, primary healthcare, and medical and humanoid systems.

The study of heterostructured materials (HSMs) answered one of the most pressing questions in the metallurgical field: “is it possible to greatly increase both the strength and the strain hardening, to avoid the “inevitable” loss of ductility?”. From the synergy between the deformation modes of zones with greatly different flow stress, low stacking fault energy (SFE) alloys can reduce their typical trade-off between strength and ductility. Stainless steel (SS) is a low-SFE material, which is widely applied for structural, biomedical, biosafety, food-processing, and daily applications. The possibility to combine its corrosion resistance and biocompatibility with the outstanding mechanical behaviour of HSMs can convert SS into a promising option for low-cost and high-effective advanced material. This paper reviews all the microstructural aspects of HS SS obtained by different processing methods and their correlation with crystallographic texture and properties such as mechanical, corrosion, biological, and magnetic characteristics. The critical comparison between experimental and modelling findings is also presented in terms of the deformation mechanisms, microstructural and texture features. Thus, the processing-microstructure-properties relationship in HS SS is the focus of this publication. The multi-disciplinary perspectives of HS SS are also discussed. This review paper will serve as a reference for understanding and designing new multi-functional HS SSs.

Polymeric foams merge the intrinsic lightness of porous materials with low thermal and electrical conductivity as well as good energy adsorption capabilities and filtration abilities, depending on their morphology. Such combinations explain their widespread use in many applications, including in the domain of personal protective equipment (PPE). Indeed, foams are the materials of choice to fulfill a series of essential protective functions, including: (i) insulation, (ii) dissipation, (iii) adsorption, (iv) filtration, (v) flotation and, of course, (vi) cushioning. Historically, foams were developed by iterative formulation works aiming at nucleating and stabilizing bubbles of gas in a polymer matrix. The foaming of polyurethanes is among the earliest – and today most mature – methodologies. Indeed, polyurethanes are obtained from isocyanate precursors that have the ability to partially decompose in gaseous CO2 in the presence of water. The gas, also referred to as the blowing agent (BA), is released concomitantly with the polymerization reaction to initiate the expansion of the growing polymer. Because the BA is primarily embedded in the molecular structure of the precursors of the polymer, this system is usually labelled as self-foaming. With the growing health and environmental awareness regarding the toxicity of isocyanates, a burgeoning number of self-foaming polymers and their precursors that circumvent the use of isocyanates are reported in the literature. They combine an interesting range of assets – from the typical ease of use of one-pack systems to the relative innocuity of their blowing gas (e.g., CO2, H2O, halogen-free alkanes) – that are very well suited to the large-scale production of foams in compliance with strict safety and environmental specifications.In this context, the present review is showcasing both historical and emerging self-foaming (pre)polymers that represent opportunities for the production of the next generation of safer and environmentally benign PPE. A special attention is dedicated to the self-foaming mechanisms – i.e., the chemical transformations of the (pre)polymers that result in the release of the blowing agent – and its interplay with the physicochemical processes resulting in the hardening of the (pre)polymers (e.g., sol-gel or rubber-glass transitions). A classification of those mechanisms – (i) thermolysis and (ii) condensation – is proposed for the first time. The properties of the resulting foams are also briefly discussed in terms of densities, cell morphology and mechanical response with the intention to guide the reader in selecting the best foaming process for the targeted polymer matrix and with a special emphasize on the PPE application domains.

Thermal management has become increasingly critical in a broad range of applications, including cooling electronic devices, regulating body temperature, harvesting solar energy, and so on. To achieve effective thermal management, thermal materials are essential platform that enables various thermal functions such as conduction, insulation, radiation, and absorption. However, it remains challenging to tune these properties in thermal materials by traditional mixing strategy. Alignment engineering has emerged as a promising approach for designing and fabricating thermal structures with extraordinary performance, but hasn’t been systematically summarized yet. In this review we summarize the recent progress in the emerging field of alignment-engineered thermal materials. The state-of-the-art alignment strategies are introduced, and various thermal materials, including alignment-engineered conductive, insulative, emissive, and absorptive materials, are discussed with emphasis on the correlations between alignment approaches and thermal functionalities, and the dynamic balance between ideal structure and practical engineering. Finally, we outline some perspectives on the challenges and opportunities for alignment engineering toward advanced thermal materials and practical applications.

Compared with traditional active cooling methods, thermoelectric coolers are more accessible to be integrated with electronics as an effective thermal management solution due to their reliability, silence, compatibility, and controllability. Considering the rapid development of processors and chips in electronics, this work comprehensively reviews the progress of state-of-the-art on-chip thermoelectric coolers and summarizes the related fundamentals, materials, designs, and system logic. Particularly, we highlight on-chip thermoelectric coolers with self-cooling design and on-demand requirement. In the end, we point out current challenges and opportunities for future improvement of designs, performance, and applications of on-chip thermoelectric coolers.

Science has always been full of surprises, and organic light-emitting diodes (OLEDs) are no exception. What exasperates scientists today may entice society tomorrow. The world has witnessed a revolution in display technology in the past two decades. In this period, the displays with bulky and heavy cathode ray tubes were transformed into ultra-slim OLED display panels. Commercialization of any new technology requires a delicate balance between device efficiency and manufacturing cost. OLEDs are still costlier than the popular liquid crystal-based displays (LCDs) because of their higher production cost. However, OLEDs are gradually replacing LCDs. The current OLED-based devices mainly utilize phosphorescent emitters that exhibit some cost and environmental concerns. Therefore, developing OLEDs with only organic components has remained the primary goal in OLED research. The discovery of thermally activated delayed fluorescence (TADF) OLEDs presents a major impetus in this area. Organic TADF molecules can be feasibly realized by manipulating the intramolecular or intermolecular charge transfer between electron-donor and electron-acceptor. The current article discusses the exciplexes formed by intermolecular charge transfer and their versatile applications in OLEDs. In the past OLED research, scientists were often bothered by the red-shifted electroluminescence band along with the desired excitonic emission, which was later identified as the exciplex emission. Exciplexes are virtual emitters that exist only in the electronically excited states. They are formed when electron-rich and -deficient compounds with appropriate frontier molecular orbitals come close enough for orbital participation, one of them being in the excited state. Given the lack of sophisticated characterization technology, exciplex emission was not fully understood back then and was considered a defect in device design. However, some were also inquisitive about the possibilities. The importance of exciplexes in OLEDs was finally recognized in the early 2010s when scientists were elated about the enormous opportunities they could offer. These emitters can be easily generated in a blend of donor and acceptor molecules without the need for complicated syntheses. They also exhibit excellent TADF emission. The researchers were exuberant about the discovery, and a slew of publications have followed the original article published by Adachi and coworkers in 2012. Exciplexes can be applied as emitters and hosts in OLEDs. The efficiency of the relevant devices gradually approaches the phosphorescent OLEDs. In the present article, we have systematically reviewed this success story, reminding the OLED community of the transformation of annoyance into ecstasy, to assist this community in developing high-performing devices based on the data accumulated herewith.

Carbons with hierarchical pores in the range of few nanometers obtained via template-assisted methods offer a great control over structure and geometry of pores, keeping them uniformly distributed and better connected. Another advantage is the easy functionalization of templated porous carbons (TPCs) by various dopants, which makes them excellent materials for catalysis, energy storage and conversion, sensors and environmental applications. Herein, beyond zeolite-templated carbons, key methodologies based on the template material such as organic and metal oxides, silica, polymers, metal-organic framework (MOFs) and bio-originated materials used for the preparation of porous carbons possessing predetermined structure and composition, have been reviewed. The effects of precursor material on the textural and structural properties of TPCs have been described. In scope of applying novel methods such as evaporation induced self-assembling (EISA), the influence of different templates on the properties of resulting materials has been discussed. Further, advances on the template-induced synthesis of self-supporting metal-organic frameworks and their utilization as advanced templates have been described. Moreover, self-templates are especially emphasized, application of which in our opinion can provide a sustainable large-scale production of TPCs. The recent progress in the study of the diffusional processes, energy and biomedical applications as well as the confinement effects of different liquids and proteins within the porous matrices of template-derived carbons, have been reviewed.

By imitating natural water circulation, artificial water generation processes can produce clean water by utilizing readily available and inexhaustible solar energy. Such a process can address the current global crises related to both energy and water shortages, and expand currently available water resources from rivers, ground water and ice to seawater, brackish water and atmospheric humidity. Among the many materials used for water generation, aerogels offer a great potential due to the inherent combination of three-dimensional, monolithic structure and porous, interconnected network. In this article, we review aerogel-based water generation from brine and atmospheric water. The unique features of aerogels are elucidated from the viewpoint of photo-thermal conversion and water transport. These two components are necessary to achieve efficient solar-driven water production systems. In addition to describing the material specifications, this paper reviews a diversity of structural designs that aim to improve the evaporation performance, including the assembly strategy of light absorption and thermal insulation layers, the reduction of evaporation enthalpy, and the salt-rejection control, as well as Marangoni effect. After evaluating different types of solar-powered water utilization technologies, the paper ends with the challenges for the commercialization and widespread use of aerogel-based water production systems: their disconnect from the current aerogel industry, high production cost and weak mechanical properties, and a lack of standardized performance testing, as well as our future perspective for their application opportunities.

Shape memory polymer (SMP) is an excellent smart material, which can sense and perform active shape change as preprogrammed. So far, there are a wide variety of stimulus-responsive SMPs being developed, including thermal-, electro-, magnetic-, photo-, microwave-, ultrasound-responsive SMPs and so on. Heating and electricity are traditional stimuli for contact actuating SMPs. In recent decades, the remote actuation of SMPs through light irradiation, magnetic field, microwave field and ultrasound field have received tremendous attentions, especially applied in biological environment, aqueous environment as well as aerospace environment. Besides, the multi-stimuli control and multi-stage deformation of SMP intelligent systems can be flexibly realized by combining various actuation methods. For rapid fabrication of personalized smart structures and architectures, 4D printing using SMPs have been proposed and underwent increasing growth to meet the practical demands. This review summarizes the progress in SMP research, with the focus on remote-actuation strategies, multi-stimuli-controlled structures, and the 4D printing of intelligent integrated systems. Besides, the comprehensive exploitation of their shape memory functions in biomedical engineering, soft robots, actuators, aerospace engineering and information storage are addressed effectively. At last, the application prospects, current problems and future challenges facing research are elaborated, so as to provide appropriate guidance for interdisciplinary study and further development.

The combination of multiple-principal element materials, known as high-entropy materials (HEMs), expands the multi-dimensional compositional space to gigantic stoichiometry. It is impossible to afford a holistic approach to explore each possibility. With the advance of the materials genome initiative and characterization technology, a high-throughput (HT) approach is more reasonable, especially to identify the specified functions for the new HEMs development. There are three major components for the HT approach, which are the computational tools, experimental tools, and digital data. This article reviews both the materials informatics and experimental approaches for the HT methods. Applications of these tools on composition-varying samples can be used to obtain stoichiometry effectively and phase-structure-property relationships efficiently for the materials-property database establishment. They can also be used in conjunction with machine learning (ML) to improve the predictability of models. These ML tools will be an essential part of HT approaches to develop the new HEMs. The ML-developed HEMs together with ML-created other materials are positioned in this manuscript for future HEMs advancement. Comparing all the reviewed properties, the hierarchical microstructures together with the heterogeneous grain sizes show the highest potential to apply ML for new HEMs, which needs HT validations to accelerate the development. The promising potential and the database from the HEMs exploration would shed light on the future of humanity building from the scratch of Mars regolith.

The desire for developing ultraviolet optoelectronic devices has prompted extensive studies toward wide-bandgap semiconductor ZnO and its related alloys. Bandgap engineering as well as p-type doping is the key toward practical applications of ZnO. As yet, stable and reproducible p-type doping of ZnO remains a formidable challenge. To circumvent p-type conductivity, ZnO-based optoelectronic devices have been developed with hetero-structures of ZnO alloys. In past decades, substantial efforts have been made to engineer the band structure of ZnO via isovalent cation- or anion-substitution for obtaining desired material properties, and considerable progresses have been achieved. The purpose of this review is to summarize recent advances in the experimental and theoretical studies on bandgap engineering of ZnO by formation of multi-component alloys, and the development of related hetero-structures and optoelectronic devices. First, we briefly introduce the general properties, epitaxial growth techniques, and bandgap engineering of ZnO. Then, we focus on presenting the current status of researches on ZnO ternary and quaternary alloys for bandgap engineering. The issues about substituent solubility limit and phase separation, as well as variations of lattice parameters and bandgap with the substituent content in the alloys are discussed in detail. Further, ZnO alloys based hetero-structures including hetero-junctions, quantum wells, and superlattices are reviewed, and recent achievements in the area of optoelectronic devices based on ZnO multi-component alloys are summarized. The review closes with outlooking the likely developing trend of multi-component alloys for the bandgap engineering of ZnO and related hetero-structures, and the potential and pathway of multi-component alloys in settling the p-type doping of ZnO.

High-entropy ceramics with five or more cations have recently attracted significant attention due to their superior properties for various structural and functional applications. Although the multi-component ceramics have been of interest for several decades, the concept of high-entropy ceramics was defined in 2004 by producing the first high-entropy nitride films. Following the introduction of the entropy stabilization concept, significant efforts were started to increase the entropy, minimize the Gibbs free energy and achieve stable single-phase high-entropy ceramics. High-entropy oxides, nitrides, carbides, borides and hydrides are currently the most popular high-entropy ceramics due to their potential for various applications, while the study of other ceramics, such as silicides, sulfides, fluorides, phosphides, phosphates, oxynitrides, carbonitrides and borocarbonitrides, is also growing fast. In this paper, the progress regarding high-entropy ceramics is reviewed from both experimental and theoretical points of view. Different aspects including the history, principles, compositions, crystal structure, theoretical/empirical design (via density functional theory, molecular dynamics simulation, machine learning, CALPHAD and descriptors), production methods and properties are thoroughly reviewed. The paper specifically attempts to answer how these materials with remarkable structures and properties can be used in future applications.

This review is written to introduce infrared photon detectors based on solution-processable semiconductors. A new generation of solution-processable photon detectors have been reported in the past few decades based on colloidal quantum dots, two-dimensional materials, organics semiconductors, and perovskites. These materials offer sensitivity within the infrared spectral regions and the advantages of ease of fabrication at low temperature, tunable materials properties, mechanical flexibility, scalability to large areas, and compatibility with monolithic integration, rendering them as promising alternatives for infrared sensing when compared to vacuum-processed counterparts that require rigorous lattice matching during integration. This work focuses on infrared detection using disordered semiconductors so as to articulate how the inherent device physics and behaviors are different from conventional crystalline semiconductors. The performance of each material family is summarized in tables, and device designs unique to solution-processed materials, including narrowband photodetectors and pixel-less up-conversion imagers, are highlighted in application prototypes distinct from conventional infrared cameras. We share our perspectives in examining open challenges for the development of solution-processable infrared detectors and comment on recent research directions in our community to leverage the advantages of solution-processable materials and advance their implementation in next-generation infrared sensing and imaging applications.

The spin-orbit coupling field, an atomic magnetic field inside a Kramers’ system, or discrete symmetries can create a topological torus in the Brillouin Zone and provide protected edge or surface states, which can contain relativistic fermions, namely, Dirac and Weyl Fermions. The topology-protected helical edge or surface states and the bulk electronic energy band define different quantum or topological phases of matters, offering an excellent prospect for some unique device applications. Device applications of the quantum materials rely primarily on understanding the topological properties, their mutual conversion processes under different external stimuli, and the physical system for achieving the phase conversion. There have been tremendous efforts in finding new topological materials with exotic topological phases. However, the application of the topological properties in devices is still limited due to the slow progress in developing the physical structures for controlling the topological phase conversions. Such control systems often require extreme tuning conditions or the fabrication of complex multi-layered topological structures. This review article highlights the details of the topological phases, their conversion processes, along with their potential physical systems, and the prospective application fields. A general overview of the critical factors for topological phases and the materials properties are further discussed to provide the necessary background for the following sections.

The application of wearable sensors in domains related to healthcare systems, human motion detection, robotics, and human–machine interactions has attracted significant attention. Because these applications require stretchable, flexible, and non-invasive materials, polymer composites are now at the forefront of research aimed at preparing innovative wearable sensors. Three-dimensional (3D) printing techniques can be used to obtain highly customised and scalable polymer composites to fabricate wearable sensors, which is a challenging task for conventional fabrication techniques. This review provides insights into the prospects of commonly used conductive nanomaterials and 3D printing techniques to prepare wearable devices. Subsequently, the research progress, sensing mechanisms, and performance of 3D-printed wearable sensors, such as strain, pressure, temperature, and humidity sensors, are discussed. In addition, novel 3D-printed multifunctional sensors, such as multi-directional, multi-modal, self-healable, self-powered, in situ printed, and ultrasonic sensors, are highlighted. The challenges and future trends for further research development are clarified.

Hydrogels have been widely investigated in biomedical fields due to their similar physical and biochemical properties to the extracellular matrix (ECM). Collagen and hyaluronic acid (HA) are the main components of the ECM in many tissues. As a result, hydrogels prepared from collagen and HA hold inherent advantages in mimicking the structure and function of the native ECM. Numerous studies have focused on the development of collagen and HA hydrogels and their biomedical applications. In this extensive review, we provide a summary and analysis of the sources, features, and modifications of collagen and HA. Specifically, we highlight the fabrication, properties, and potential biomedical applications as well as promising commercialization of hydrogels based on these two natural polymers.

In this review, we cover copper-to-copper (Cu-to-Cu) direct bonding, point contact reaction between silicon (Si) nanowire and metal nanowire, and cold welding of gold (Au) and silver (Ag) nanowires. All of them occur under nanoscale interfaces at low temperatures. For a broader consideration, because Cu is known to exhibit significant anti-pathogen and anti-viral properties, the interfacial reaction in Cu nano-grain metallurgy may be used to manufacture Cu and Cu alloy products to reduce virus transmission, which can have a very large impact to our society. Furthermore, in the future semiconductor technology, because of dense packaging, Joule heating will be serious. Thus, low entropy production process will receive attention, which means low temperature joining technology such as cold welding and nano-welding will be important.

Metal-halide perovskites-based optoelectronic devices, such as solar cells and light-emitting diodes (LEDs), are transitioning from promising performers to direct competitors to well-established technologies due to the advantage of cost-effectiveness. Perovskite solar cells (PSCs) have achieved power conversion efficiency beyond 25% in less than ten years, showing great potential in low-cost photovoltaics with high efficiency and low fabrication cost. Nanostructured perovskites have yielded world-record LEDs due to their high versatility in the local management of charge carriers and the close-to-unit photoluminescence quantum yields (PLQY). However, the development of such perovskite optoelectronic devices is still restricted by their narrow light absorption band, low charge carrier mobility, energy level mismatching, and poor stability and lifespan of the devices. Lanthanides have been applied in perovskite optoelectronic devices to minimize the abovementioned shortcomings. Herein, we provide a brief review of the history of lanthanide materials in perovskite optoelectronic devices and a detailed discussion of the recent developments in this field. We will focus on the advances in lanthanide-doped downshifting downconversion, upconversion systems, perovskite light-harvesters, and charge transport layers for both PSCs and lanthanides-doped perovskite quantum dots/nanocrystals (QDs/NCs) for photoluminescent devices.

Personal protective equipment (PPE) is crucial for ensuring occupational safety when handling toxic chemicals or in close contact with biological pathogens. The increased poisoning and infection cases outside the working scenario have attracted public attention, which drove the development and application of PPE for the professionals and the public. The use of PPE can effectively lower the risk of acute and chronic diseases caused by pesticide exposures and significantly reduce the spread of infectious diseases. However, conventional PPE mostly only functions as physical blocking or electrostatic repulsion materials, which still poses potential risks caused by cross- and post-contamination from the PPE. Although sensors are not usually considered as a necessary component of PPE, the detection of health threats in the environment could benefit preparations for unprepared risks promptly, especially in non-occupational situations, thus improving the protection of human safety. In this review, we discuss the needs of novel PPE by surveying some insufficient protection cases and threats that occurred during conventional PPE applications. Then, we summarize recent progress in developing single-functional decontamination and colorimetric sensing PPE, mostly fiber-based media against agricultural toxicants and microorganisms, with intension to inspire the future design of novel PPE with the integrated “decontamination-and-sensing” property. Some recently developed conventional dual-functional materials against either pesticide or microorganism exposures are highlighted. Finally, strategies and limitations of developing decontamination and sensing material using unique interactions and reactions of targets with functionalized fibrous substrates are discussed by comparing the successful approaches and practical challenges in PPE applications.