Rewritable paper (RP) which takes advantages of stimuli-responsive color-changing materials/smart materials and can be used multiple times has been demonstrated to hold potential to reduce human waste of paper and alleviate the increasingly severe environmental issues. To make the RP closer to the way that people are accustomed to reading and more practical for daily life, interest and effort toward smart materials with clearly visible or naked-eye color-switching properties are particularly important. In this review, depending upon the stimulation protocol, five types of stimuli (thermo-, water-related-, light-, stress-, and electric-field-) smart chromogenic materials and systems with visible color switching applied in light absorptive display for RP are focused on. In each section, different stimulus-chromic molecules and their corresponding systems are discussed to explore the design concepts, methodologies, working mechanisms, and pros and cons of various chromogenic materials used in light absorptive RP. In addition, the challenges and prospects are sketched to provide strategies to explore more smart materials for high-performance RP and its relative techniques.

Powder-based additive manufacturing (AM) is revolutionizing the fabrication of advanced engineering metallic materials, including aluminium (Al) alloys, which are the workhorse materials in automobile and aerospace industries. However, challenges remain in the wider applications of AM to produce Al components due to the high tendency to form coarse, textured columnar grains, which causes hot-cracking and severe property anisotropy. The recent adoption of inoculation treatment in AM of Al alloys has been successful in achieving grain refinement, cracking elimination and property improvement, which is a step forward in this field. This paper surveys the emerging researches on inoculation treatment of AM-fabricated Al alloys and provides a comprehensive overview of different inoculation techniques for AM, the refining efficiencies of various inoculants and their underlying mechanisms. The uniqueness of this review includes substantive discussions on the mechanism of epitaxial grain growth during AM and a succinct comparison of the refining efficiency based on both experiment and crystallographic modelling. Critical challenges in the most recent alloy design strategy embedded with inoculation treatment are also discussed. Accordingly, outlooks for the immediate future in this area, gaps in the scientific understanding, and research needs for the expansion of AM in fabrication high-performance Al alloys are provided.

Mobility is a critical parameter influencing the overall performance of organic solar cells (OSCs). Herein, we innovatively elucidated the intricate interrelation between the photovoltaic molecular structures and the methodologies employed for the extraction of charge carrier mobility in OSCs. We proposed a simple yet effective principle to accurately extract charge carrier mobility values using the standard space-charge-limited current (SCLC) measurement, while critically assessing theoretical and experimental deficiencies through the drift-diffusion analysis. It was found that field-dependent charge transport is necessitated to describe the prominent long-range intrachain hopping carrier behavior in polymers, while short-range intermolecular hopping results in trap-involved charge transport within small molecular acceptors. Based on the above understanding, a synergetic inter/intra-molecular hopping strategy was proposed to fabricate thick-film all-polymer OSCs, and an unprecedented power conversion efficiency (PCE) of 16.61 % was achieved in the 300 nm PM6:PY-IT OSC. This work not only presents a precise and straightforward approach for measuring mobility values, but also provides a significant reference about charge carrier transport to make optimal decisions regarding photovoltaic material design and device fabrication process of high-performance OSCs.

To cater to the extensive body movements and deformations necessitated by biomedical equipment flexible piezoelectrics emerge as a promising solution for energy harvesting. This review research delves into the potential of Flexible Piezoelectric Materials (FPM) as a sustainable solution for clean and affordable energy, aligning with the United Nations' Sustainable Development Goals (SDGs). By systematically examining the secondary functions of stretchability, hybrid energy harvesting, and self-healing, the study aims to comprehensively understand these materials' mechanisms, strategies, and relationships between structural characteristics and properties. The research highlights the significance of designing piezoelectric materials that can conform to the curvilinear shape of the human body, enabling sustainable and efficient mechanical energy capture for various applications, such as biosensors and actuators. The study identifies critical areas for future investigation, including the commercialization of stretchable piezoelectric systems, prevention of unintended interference in hybrid energy harvesters, development of consistent wearability metrics, and enhancement of the elastic piezoelectric material, electrode circuit, and substrate for improved stretchability and comfort. In conclusion, this review research offers valuable insights into developing and implementing FPM as a promising and innovative approach to harnessing clean, affordable energy in line with the SDGs.

In living systems, there is emerging evidence that nature uses liquid-liquid phase separation (LLPS) to organize diverse cellular processes such as signal transduction, translation regulation, and gene expression among chemical chaos. Inspired by the naturally occurring LLPS, there is increasing interest in the deployment of LLPS in synthetic biosystems towards a wide range of applications. Although much progress has been made, there is still a limited understanding of LLPS in synthetic biosystems. Importantly, studies in LLPS in non-living systems (i.e., polymer systems) and in living systems have been progressed separately. There is an urgent need to summarize and integrate our current understanding of LLPS in different systems to inform the design of artificial LLPS in synthetic biosystems. In this review, we first summarize the development of theoretical modeling of LLPS in non-living systems and living systems. We then explore current approaches for the construction and functionalization of LLPS in synthetic biosystems. We finally review the state of the art of LLPS in synthetic biosystems towards applications in synthetic biology, cellular engineering and biotechnology.

The exploration and development of natural biopolymer-based hydrogels can be traced back to the 18th century. The rising interest in these hydrogels is largely due to their soaring demand in diverse applications such as tissue engineering, bio-separation, drug delivery, smart bioelectronics, and eco-friendly agriculture. However, one major drawback of these naturally derived biopolymer-based hydrogels is their subpar mechanical properties characterized by limited stretchability, modulus, and resilience, along with inadequate water adsorption capability. This restricts their broad-spectrum applicability. These biopolymers are typically crosslinked through different strategies to rectify these issues and functional groups present in polymer chains play crucial roles in crosslinking strategies. Consequently, the understanding of the chemical structure-function relationship in the crosslinked polymeric network is paramount for the design of an effective natural biopolymer-based hydrogel. A profound comprehension of the behavior of functional groups during crosslinking is therefore essential. This review provides a comprehensive overview of the chemistries of functional group interactions in natural biopolymers that are utilized in the development of functional hydrogels. Various categories of functional group interaction chemistries are examined and discussed in terms of crosslinking strategies (e.g., hydrogen bonding, ionic interaction, hydrophobic interaction) for hydrogel formation. Furthermore, the types, properties, and cutting-edge applications of resultant natural biopolymer-based hydrogels are outlined along with a discussion of the future prospects in this field of research.

In industries as diverse as automotive, aerospace, medical, energy, construction, electronics, and food, the engineering technology known as 3D printing or additive manufacturing facilitates the fabrication of rapid prototypes and the delivery of customized parts. This article explores recent advancements and emerging trends in 3D printing from a novel multidisciplinary perspective. It also provides a clear overview of the various 3D printing techniques used for producing parts and components in three dimensions. The application of these techniques in bioprinting and an up-to-date comprehensive review of their positive and negative aspects are covered, as well as the variety of materials used, with an emphasis on composites, hybrids, and smart materials. This article also provides an updated overview of 4D bioprinting technology, including biomaterial functions, bioprinting materials, and a targeted approach to various tissue engineering and regenerative medicine (TERM) applications. As a foundation for anticipated developments for TERM applications that could be useful for their successful usage in clinical settings, this article also examines present challenges and obstacles in 4D bioprinting technology. Finally, the article also outlines future regulations that will assist researchers in the manufacture of complex products and in the exploration of potential solutions to technological issues.

In the current era of globalization, the exponential surge in the production, consumption, and disposal of agricultural and post-consumer polymeric waste material has emerged as a pressing environmental concern of paramount importance. The current situation, wherein the presence of plastic particles and other plastic-based contaminants in the food supply chain is increasingly evident, poses a profound health risk to mankind. In this regard, the utilization of conventional waste management practices, such as, open burning, landfilling, and incineration, leads to adverse consequences, like, the emission of greenhouse gases and substantial economic losses. To encounter such problems, researchers are actively engaged in the development of innovative recycling processes aimed at closed-loop circular economy by transforming these wastes into sustainable value added products. This comprehensive review emphasizes the necessity of sustainable recycling of lignocellulosic biomass and synthetic plastic wastes, with a specific focus on their transformation into biodegradable polymers and their potential biomedical applications. Moreover, we have critically discussed the recent trends and drivers in this field, global environment threat, different recycling route of lignocellulosic biomass and synthetic polymer wastes. Furthermore, this review provides a detailed discussion on the applications of these biodegradable polymers in the field of tissue engineering, drug delivery, and antimicrobial applications. Additionally, we have also addressed the critical challenges involved in this field and possible solutions to overcome them.

As an important component of future electronic devices, photodetectors require mechanical flexibility, and stretchability to meet the demands of conformal, portable, and lightweight applications. As expected, flexible photodetectors (FPDs) were born timely and have obtained rapid development driven by the considerable progress of the optoelectronic industry. Especially, FPDs appear to serve as a bridge between electronic information systems and biological systems due to their potential functional applications including wearable devices, artificial intelligence, bionics devices, etc. However, the poor mechanical stability, narrow spectral response range, low responsivities and difficulty in miniaturization of traditional FPDs have greatly limited their commercial and industrial applications. One of the most promising routes toward addressing the inherent shortcomings of FPDs is through constructing novel micro/nano-structured integrated flexible detection systems to achieve diverse functions and enhance performance, hence facilitating flexible integration. In this review, the recent advances in performance-enhancing strategies for FPDs are outlined and discussed. First, the detection mechanism, performance enhancement mode, and key figures-of-merit of FPDs are summarized and basic design principles of the FPDs are discussed emphatically. Then, recent progress in structural engineering-based performance enhancement of FPDs is reviewed, categorized by the types of enhancement, electric field manipulation engineering, strain engineering, and optical field manipulation engineering. Moreover, this review also summarizes the integration strategies for the application of FPDs and finally puts forward the challenges and future research directions in these fields.

Ensuring the fire safety of high voltage (HV) outdoor insulators is key to maintain the reliable operation of the electrical grid. This requires the careful selection of suitable polymeric composite materials with excellent electrical tracking, erosion, and fire resistance characteristics. To improve their performance against electrical tracking and potential combustion issues, inorganic additives are commonly integrated into these materials. The focus of this review article is on describing the progress and innovations in enhancing the electrical tracking, erosion, and fire performance of polymeric materials by incorporating inorganic additives. The main objective is to explore the development of these materials and showcase their evaluation through laboratory testing. This study highlights significant state-of-the-art advancements in the field, providing valuable insights into its current progress. Additionally, the research outlines prospects, offering a peek at how upcoming studies are expected to further advance the scientific knowledge in the field. By disseminating critical information about the development, testing, and future potential of polymeric materials containing inorganic additives, this work is expected to facilitate researchers in advancing their work in HV outdoor insulation, leading to more efficient electrical insulation solutions for safer and reliable electrical grids.