Sodium alginate (SA) is a natural polymer suitable for the preparation of food packaging films. This review, guided by the development trends of active preservation and intelligent monitoring of SA food packaging films, summarizes the research progress of SA food packaging films from the aspects of preparation methods, functional modification and design strategies. The advantages and progress of solution casting method, electrospinning method and layer assembly method were analyzed. The research progress of active preservation formed by the synergy of barrier performances, antibacterial and antioxidant properties, as well as intelligent monitoring stimulated by pH changes to change color was analyzed and summarized. The design strategies for achieving active preservation and intelligent monitoring, as well as the implementation approaches for the system's functions, were proposed. The methods, functions and significance of conducting life cycle assessment were pointed out. This review has positive significance for the development of SA food packaging films.

Flexible strain sensors based on conductive hydrogels have attracted considerable attention for wearable electronics due to their intrinsic softness, stretchability, and biocompatibility. However, achieving a balance between mechanical robustness, high conductivity, and multifunctionality remains challenging. Herein, κ-carrageenan-based hydrogels CA-K+/P(AM-MBA)/AgNPs-K+ with a dual-network structure and ion-electron synergistic conduction were constructed using κ-carrageenan (CA), acrylamide (AM), N, N'-methylene bisacrylamide (MBA), silver nanoparticles (AgNPs), and KCl. The dual-network consists of an ion-coordinated dynamic network (CA-K+) formed via the Hofmeister effect and a covalent copolymer network (P(AM-MBA)), while embedded AgNPs and K+ establish a synergistic ion-electron conductive pathway and provide antibacterial functionality. The optimized hydrogel exhibits a tensile strength of 273 kPa, an elongation rate of 426%, and an electrical conductivity of 3.5 × 10-2 S cm-1. It has a range coefficient (GF) of 2.98 within the strain range of 0-200%, and a rapid and sensitive response/recovery time of approximately 142/135 ms. Its inhibition rates against E. coli and S. aureus are 93.2% and 95.1%, respectively. The results show that the hydrogel has better mechanical, conductive sensing and antibacterial properties than those reported in the literature, which provides a feasible strategy for the construction of advanced wearable sensing materials.

Schematic diagram illustrating the preparation process and functional applications of P (AA‑IL)/CS/PVA dual-network composite hydrogels

ABSTRACT With the rapid advancement of 5G/6G communication technologies, polymer‐based transparent wave composites urgently require synergistic optimization of low dielectric constant, ultra‐low dielectric loss, and high thermal stability. Although cyanate ester (CE) resins exhibit excellent high‐frequency dielectric properties, their inherent brittleness severely limits practical applications. This study employs bio‐based epoxidized soybean oil (ESO) to molecularly modify dicyclopentadiene‐based cyanate ester (DCPDCE) for comprehensive performance enhancement. Systematic investigations demonstrate that ESO introduction effectively regulates molecular polarization, significantly reducing both dielectric constant (ε) and loss (tanδ). To further improve dielectric performance, hollow nano‐SiO 2 with dielectric matching characteristics was incorporated as a reinforcing phase. At 7 wt% SiO 2 content, the DCPDCE‐ESO/SiO 2 composite achieved outstanding performance at 10 GHz: ε = 2.46, tan δ = 0.005, and transmittance increased to 0.971. This gradient dielectric structure offers a novel design concept for next‐generation high‐frequency transparent wave materials, highlighting bio‐based materials' application potential in high‐performance communication and providing an important technical pathway for environmentally friendly high‐frequency material development.

Chitosan (CS) is a naturally derived polysaccharide containing amino and hydroxyl groups. Due to its excellent biocompatibility, biodegradability, antibacterial activity, hydrophilicity and environmental friendliness, it has important applications in many fields. In recent years, the research and application of chitosan in hydrogel flexible sensing materials and smart food packaging materials have received extensive attention. This paper systematically reviews the preparation methods, functionalization strategies of chitosan hydrogels, and the research progress of their applications in flexible sensing materials and smart packaging materials. The design principles and implementation approaches of sensing hydrogels and stimulus-responsive chitosan hydrogels were analyzed and summarized. Meanwhile, the latest breakthroughs, main challenges and future opportunities in chitosan-based hydrogel sensing materials and the field of intelligent food packaging were emphasized. The research results are intended to provide guidance for the innovation and application development of chitosan-based sensing materials and smart packaging materials.

The development of sustainable and intelligent food packaging materials with integrated active and sensing functions is of increasing importance. In this study, a biodegradable multifunctional smart film was fabricated based on acrylate-modified starch (AS), polyethyleneimine (PEI), 4-mercaptobenzoic acid (4-MBA), and mulberry anthocyanins (MAC). Acrylate starch provided reactive backbones for synergistic crosslinking with PEI and 4-MBA, forming a dense network structure that significantly enhanced the mechanical strength and barrier properties of the film. The optimized composite film exhibited a tensile strength of 10.44 MPa and demonstrated significant antibacterial activity, with inhibition zones of 19.5 mm against Escherichia coli and 15 mm against Staphylococcus aureus. Meanwhile, MAC endowed the film with highly sensitive pH-responsive colorimetric behavior (ΔE > 50), enabling visual detection of spoilage-related alkaline volatiles. Furthermore, integration with a color sensor system allowed the color variation of the film to be converted into digital signals, achieving dual-mode (visual and digital) freshness monitoring. Application tests demonstrated that the film effectively delayed quality deterioration of strawberries and provided real-time indication of shrimp freshness during storage. This work offers a promising strategy for constructing biodegradable smart packaging materials that combine structural reinforcement, active preservation, and intelligent monitoring functions.

Dielectric elastomers have broad application prospects in soft robots, artificial muscles, flexible sensors and other fields. However, their low dielectric constant results in large deformations only at high electric fields, and there is an urgent need to improve their driving performance through material modification. To address this, this study employs aminpropyl isobutyl polyhedral oligossiloxane (POSS-NH2) to surface-modify graphene oxide (GO). Through an opening reaction between amino and epoxy groups, POSS-coated GO (POSS@GO) nanohybrid sheets were synthesized. Subsequently, POSS@rGO/PDMS composite films were successfully prepared using an in-situ polymerization process. The structure and morphology of POSS@GO were characterized using FT-IR, XPS, SEM, and TGA, confirming uniform covalent grafting of POSS onto the GO surface. The influence of different POSS@GO loadings on the mechanical behavior, dielectric performance, and actuation performance of the composite was systematically investigated. At an optimal POSS@GO content of 7 wt%, the dielectric constant increased to approximately 12 at 100 Hz while maintaining a relatively low dielectric loss (tanδ = 0.4). As a result, the electromechanical sensitivity factor and actuation performance of PDMS were effectively improved. (31.95% at 12.4 kV/mm). This work offers a feasible approach for the development of high-performance dielectric elastomer materials.

A photothermal hydrogel with sunlight internal reflective function was prepared by initiating the polymerization of acrylamide (AM) and N,N-methylenediallacrylamide (MBA) in a solution containing sodium alginate (SA), mica-based highlight flash sheets (HFS). The effects of HFS, rGO@Bi2S3, SA and MBA on photothermal hydrogel were investigated using interfacial evaporation rate and mechanical properties as evaluation indicators. The test results show that the interfacial evaporation rates of the photothermal hydrogel for fresh water and 3.5% salt water have reached 7.253 kg center dot m-2 center dot h-1 and 5.849 kg center dot m-2 center dot h-1 respectively, which was 2.295 kg center dot m-2 center dot h-1 and 2.524 kg center dot m-2 center dot h-1 higher than that of the photothermal hydrogel without HFS. This is mainly attributed to the excellent photothermal conversion ability of rGO@Bi2S3 and the outstanding sunlight internal reflection ability. The uniqueness of this study lies in the construction of a photothermal hydrogel with sunlight internal reflection function and having a greenhouse effect by incorporation of high-brightness reflective sheets. The results provide a new strategy for improving the utilization of incident light and the efficiency of photothermal conversion.

Ion-conductive hydrogels (ICHs) have emerged as a promising sensing material for smart wearable sensors due to their unique ion migration properties, exceptional flexibility, and compatibility with human tissues. However, its practical application has been hindered by deficiencies such as inadequate mechanical properties, limited functional integration, and poor environmental tolerance. To address the limitations of conventional ionic-conductive hydrogels, this study developed a novel ion-conductive hydrogel with supramolecular interactions through copolymerization of multifunctional imidazole ionic liquid, modified cellulose and acrylic acid. The research results indicated that the hydrogel exhibits excellent mechanical properties, ionic conductivity, environmental adaptability, and multifunctional integration capability due to its covalent cross-linking network and supramolecular interaction network, which effectively solves the problems existing in ionic liquid hydrogel. As a multifunctional wearable sensor, this hydrogel material exhibits a gauge factor (GF) of up to 7.47 (stress 400-500 % range). It enables precise monitoring of signals such as micro-expressions and joint flexion, while delivering multidimensional responses to waveforms, frequencies, and amplitudes in Morse code and underwater communication applications. The study offers new insights into the design and application of high-performance, multifunctional, and eco-friendly wearable electronic materials, thereby expanding their potential applications in extreme environments.

The large quantity of organic dyes produced during industrial manufacturing processes has significantly harmed both the environment and human health, necessitating effective measures to address this issue. Visible light photocatalysis technology shows considerable potential for the degradation of nitroaromatic compounds and has garnered widespread interest. In this study, a chitosan and graphene oxide (GO) bottom membrane was first prepared, followed by the synthesis of the MoS2/Ag3PO4 photocatalyst using a co-precipitation method, which was then incorporated into the CS/GO substrate membrane. Subsequently, composite photocatalytic films comprising CS/GO/Molybdenum disulfide (MoS2)/silver phosphate (Ag3PO4)/silver (CS/GO/MoS2/Ag3PO4/Ag) were fabricated through the in-situ synthesis of Ag as a novel photocatalyst for the reduction ofp-nitrophenol (p- NP). These CS/GO/MoS2/Ag3PO4/Ag composite films demonstrated excellent photocatalytic performance in effectively reducing p-NP to the less toxic p-aminophenol (p-AP). Notably, the CS/GO/MoS2/Ag3PO4/Ag2.5 composite film, with a 2.5 % photocatalyst addition, emerged as the most effective p-NP reduction photocatalyst, achieving a reduction efficiency of 96.77 % within 50 minutes. Furthermore, the composite film exhibited good photocatalytic stability, maintaining effective photoreduction properties even after four degradation cycles. The in-situ synthesis of Ag further enhanced the photodegradation of reduced p-NP within the CS/GO/MoS2/Ag3PO4/ Ag composite membrane. Therefore, the preparation of CS/GO/MoS2/Ag3PO4/Ag composite films holds significant promise for the photocatalytic reduction ofp-NP.

Carrageenan (CA) is a biopolymer commonly found in red algae. Traditionally, commercial CA has been used as an emulsifier, stabilizer, thickener, and gelling agent in food products. CA exhibits various bioactive properties that contribute to disease amelioration and microbial regulation. As a biocompatible material, CA is increasingly employed in the development of functional hydrogels with applications in biomedicine, environmental pollution control, and food packaging. This review summarizes the preparation methods and applications of CA-based hydrogels, detailing physical and chemical cross-linking approaches. It also examines recent advances in CA-based hydrogels for wound healing, drug delivery, tissue engineering, as well as in treating industrial wastewater containing dyes, pharmaceuticals, and metal ions, and in food packaging films. Finally, this review discusses the current challenges and future directions for CA-based hydrogels, providing new perspectives for developing sustainable, efficient, and advanced biomass-based hydrogel materials.

Solar-driven interfacial evaporation (SDIE) offers a promising and sustainable approach to addressing the global freshwater scarcity crisis. In this study, MXene/gelatin foam hydrogels (MGFH) featuring a three-dimensional porous architecture were successfully fabricated using a straightforward foaming, freezing, and cross-linking procedure. Gelatin served as a surface-active agent during high-speed stirring to facilitate foam formation, while freeze-drying and subsequent cross-linking stabilized the porous structure. The incorporation of MXene nanosheets markedly enhanced the photothermal conversion efficiency of the hydrogels, enabling effective solar energy absorption and utilization. Under standard solar irradiation (1.0 kW center dot m- 2), the MGFH demonstrated an impressive evaporation rate of 2.26 kg center dot m- 2 center dot h- 1. Notably, the MGFH retained a high evaporation rate of 1.42 kg center dot m- 2 center dot h- 1 even in simulated seawater with 20 wt% salinity. Furthermore, the hydrogel achieved ion removal efficiencies exceeding 99.9 % for major seawater ions (Na+, Mg2+, K+, and Ca2+) and exhibited outstanding resistance to biofouling. These results underscore the potential of MGFH for long-term desalination of hypersaline water and for wastewater treatment applications. Overall, the facile and effective fabrication strategy proposed in this work provides a promising pathway for developing high-performance, durable materials for solar interfacial evaporation.

The rapid progress in flexible electronics drives the need for multifunctional sensing materials with stretchability, self-healing, adhesion, and antimicrobial properties for wearable devices in complex environments. In this study, silver-functionalized carbon nanotubes (Ag-CNTs) were employed as antibacterial conductive fillers within the hydrogel. A dual-crosslinked composite hydrogel, OSA-g-PAA/Ag-CNTs, was successfully fabricated using oxidized sodium alginate (OSA) and acrylic acid (AA) as the hydrogel matrix, with ammonium persulfate (APS) and Ca2+ as crosslinking agents. This hydrogel demonstrated remarkable properties, including a stretchability of up to 1400 %, excellent self-healing capabilities, and strong self-adhesive performance. Additionally, the incorporation of silver nanoparticle-decorated carbon nanotubes (Ag-CNTs) endowed the material with significant antibacterial activity, achieving a 99.9 % inhibition rate against both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). In flexible sensing applications, the hydrogel exhibited outstanding strain sensitivity and durability, enabling real-time monitoring of human motion and other physiological activities. Its unique photothermal management properties and thermal stability further expanded its potential for use in temperature-controlled devices and high-temperature environments. This study provides an innovative solution for developing multifunctional, high-performance flexible sensing materials with broad application prospects, particularly in health monitoring, sports rehabilitation, and smart wearable devices.

With growing environmental concerns, dwindling fossil fuel reserves, and increasing consumption, the demand for sustainable materials is surging, making the development of bio-based materials a crucial imperative. 2,5-Furandicarboxylic acid (FDCA), a promising biomass-derived diacid, offers renewability, a low carbon footprint, and structural designability. Its versatility allows for the production of various high-performance biodegradable polymers, including polyesters, polyamides, and polyimides, positioning it as a leading bio-based alternative to the petroleum-derived terephthalic acid (TPA). This review systematically examines the progress in FDCA-based high-performance polymers. We present recent advancements in FDCA synthesis, property optimization, and applications in biodegradable packaging, flexible electronics, biomedicine, and fire protection. Finally, we discuss the challenges and future prospects of FDCA as a sustainable chemical building block, aiming to guide the design and commercialization of eco-friendly materials.

Dielectric films are critical components in the fabrication of capacitors. However, their reliance on petroleum-derived polymers presents significant environmental challenges. To address this issue, we report on a high-performance biomass-based dielectric material derived from vanillin (VA), a renewable aromatic aldehyde. Vanillin was first esterified to synthesize vanillin methacrylate (VMA), which was then copolymerized with methyl methacrylate (MMA) via free-radical polymerization to yield P(VMA-MMA). By crosslinking the aldehyde groups in VMA with the amine groups in the polyether amine D400 (PEA), we fabricated a series of P(VMA-MMA)@PEA dielectric films with precisely tunable crosslinking densities. The unique molecular structure of vanillin, featuring both a benzene ring and an ester group, facilitates strong δ-π interactions and dipolar polarization, synergistically enhancing energy storage density while minimizing dielectric loss. At an optimal P(VMA-MMA) ratio of 1:10 and 80

Ionic conductive hydrogels (ICHs) show great application prospects in flexible electronic skin and self-powered sensing systems due to their skin-like mechanical compliance and excellent ionic transport properties. However, integrating multifunctional performance while ensuring environmental adaptability and stability remains a major challenge. This study designed a multifunctional ionized cellulose (IMC) and proposed a biomass-based ICH platform. It successfully achieved high mechanical performance, high stability, good conductivity, and multifunctional properties. Firstly, IMC was synthesized by the Schiff base reaction, in which diacetyl cellulose (DMC) was functionalized using histidine-based ionic liquid (HIL) prepared from L-histidine as a modifier. Furthermore, by combining radical polymerization technology, IMC and acrylamide are cross-linked through one-step reaction to form a cellulose ICH with a double network structure. The design cleverly utilizes dynamic ionic bonds and various interactions (such as hydrogen bonds and electrostatic forces) to endow the hydrogel with strong mechanical properties (stretchability 752 +/- 12.1 %, mechanical strength 0.23 +/- 0.03 MPa), antibacterial properties, biocompatibility, adhesion, and thermal stability. In addition, the hydrogel exhibits efficient energy conversion capability (power density of 24.9 mW/m2), making it an ideal candidate material for constructing multifunctional integrated wearable sensors and triboelectric nanogenerators (TENGs).

Solar energy is an inexhaustible clean energy. Owing to the shortage of fossil fuels and the development of science and technology, increasing attention is being paid to the use of solar energy. Photothermal conversion (PC) materials are crucial for effectively acquiring and converting solar energy. At present, various PC materials have shown considerable potential, particularly PC hydrogels, a new type of PC material that has been increasingly studied by researchers in recent years. In this study, the characteristics, preparation methods, and PC efficiencies and mechanisms of PC hydrogel materials are reviewed. The main features of photothermal materials such as precious metals, semiconductors, carbon-based materials, and polymer materials are also comprehensively analyzed. In addition, the applications and research progress of PC hydrogels in the fields of seawater evaporation, wastewater purification, organic compound degradation, photocatalytic hydrogen production, and carbon dioxide conversion are examined. Finally, the development prospects and challenges associated with PC hydrogels are evaluated. This study is expected to have a positive significance for the development of new PC hydrogels for the efficient utilization of solar energy.

The separation and purification of wastewater containing Cr(VI) remains a challenging subject. The preparation of composite membranes capable of adsorbing and photocatalytically reducing Cr(VI) is a promising method for treating wastewater containing Cr(VI). In this study, a novel photocatalyst CS/GO/Bi2Ce2O5S2 was prepared through the hydrothermal reaction of (NH4)2Ce(NO3)6 with Bi(NO3)3 and (NH2)2CS. Then the photocatalyst was dispersed in chitosan (CS)/graphene oxide (GO) solution to prepare the CS/GO/Bi2Ce2O5S2 membrane, which was then immersed in AgNO3 solution and in situ reduced to produce AgNPs, resulting in a novel photocatalytic membrane (CS/GO/Bi2Ce2O5S2/Ag). The results show that the membrane can reduce 99.75% of Cr(VI) in wastewater. The adsorption capacity of the photocatalytic membrane for Cr(VI) reached 235.34 mg/g, and the absorption processes conformed to the pseudo-second-order model and Langmuir model. This photocatalyst features a narrow band gap and a very high photogenerated carrier generation rate and photocatalytic efficiency. The electrochemical test shows that CS/GO/Bi2Ce2O5S2@Ag has the maximum photocurrent density and the minimum impedance, which can be more beneficial to the generation of photogenerated charge carriers. The results of this study realize the simultaneous adsorption, photocatalytic reduction, separation, and purification of wastewater containing Cr(VI), which has high efficiency, economic, and practical significance.

The integration of high ionic conductivity and mechanical robustness in hydrogels for wearable applications remains a significant challenge. In this work, we present a simple approach for fabricating sodium alginate-based hydrogels OSA-g-P(AA-co-MBA)/Li+ using Hofmeister effect-driven dual-crosslinking strategy. This approach enables the hydrogel to achieve tunable mechanical and electrical properties, making it ideal for flexible sensors in human activity monitoring. By incorporating Li+ and optimizing the crosslinking density, The hydrogel demonstrates remarkable stretchability with up to 1596 % elongation and exhibits antibacterial properties against both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The dynamic bonds formed by aldehyde groups endow the material with self-healing capabilities. In flexible sensing applications, OSA-g-P(AA-coMBA)/Li+ shows outstanding strain sensitivity, enabling real-time monitoring of human motion and other physiological activities. Furthermore, OSA-g-P(AA-co-MBA) hydrogel demonstrates rapid temperature-responsive behavior, with its transparency changing in response to temperature variations, offering potential for applications that require dynamic material properties. With its outstanding mechanical performance, high strain sensitivity, and self-healing abilities, this hydrogel presents a promising platform for next-generation wearable sensors and flexible electronic devices.

Flexible smart sensing materials are gaining tremendous momentum in wearable and bionic smart electronics. To satisfy the growing demand for sustainability and eco-friendliness, biomass-based hydrogel sensors for green and biologically safe wearable sensors have attracted significant attention. In this work, we have prepared MCC/ PAA/AgNWs/CNTs hydrogel sensors with excellent conductive sensing properties by a simple physical blending method. The ZnCl2 solvent system was used to dissolve the MCC, followed by introducing acrylic acid to polymerize under UV illumination. Subsequently, CNTs and AgNWs were introduced into the hydrogel network to obtain hydrogel with excellent conductive sensing and antibacterial properties. Here, the physical and chemical interactions between the components significantly improved the mechanical properties of the hydrogels, exhibiting good tensile strength (0.45 MPa), elongation at break (558 %) and adhesion properties. Hydrogel presented outstanding electrical conductivity and significantly elongation sensitive (GF = 4.73 when elongated 90-120 %). Additionally, the hydrogel was also found to have significant antimicrobial activity against both Escherichia coli and Staphylococcus aureus, and the antibacterial effect was almost 100 %. With high sensitivity, stability, and reproducibility, these hydrogel strain transducers can detect various human movements, including finger flexion, wrist movement, joint motion, and heartbeat.