Search Results (122)

Copper and lead contamination in loess areas poses a potential threat to soil environmental quality and sustainable land use, while the low permeability, high clay content, and strong buffering capacity of loess often limit the efficiency of conventional electrokinetic (EK) remediation. This study developed an enhanced EK system integrating novel hydrogel (NH) electrodes, a poly(diallyldimethylammonium chloride)-modified activated carbon/carbon fibre (MAC/CF) permeable reactive barrier (PRB), and a vertical voltage for the remediation of Cu- and Pb-contaminated loess. The effects of vertical voltage (0, 10, 20, 30, and 40 V) on EK behaviour, contaminant migration, and removal performance were investigated. The results showed that the MAC/CF PRB improved electrical stability, enhanced electroosmotic transport, and regulated pH evolution by providing conductive pathways and reactive sites for OH⁻ capture and metal adsorption. Compared with the system without a PRB, the accumulated electroosmotic flow (EOF) increased from approximately 680 to 980 mL. The vertical voltage further promoted Cu²⁺ and Pb²⁺ redistribution into the PRB and enhanced the migration–adsorption coupling process. The optimal voltage of 30 V achieved the best remediation performance, with Cu and Pb removal efficiencies of 69–80% and 32–36%, respectively, within 72 h at initial concentrations of 500 mg kg⁻¹. Mechanistic analysis revealed that the vertical voltage transformed the MAC/CF barrier from a passive adsorption layer into an electrically activated migration–capture interface. The synergistic effects of ion transport regulation, OH⁻ buffering, conductive network construction, and heavy metal adsorption effectively suppressed precipitation-induced focusing and improved remediation efficiency. This study provides a promising strategy for enhancing EK remediation of low-permeability and structurally sensitive soils. Full article

In this study, we synthesized a lignin-based superabsorbent hydrogel (LWR) to relieve severe evaporation and structural degradation in inland saline–alkali soils. The LWR was prepared via free-radical graft copolymerization of calcium lignosulfonate (CL) and acrylic acid (AA), with its swelling performance optimized systematically. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used to characterize its chemical and microscopic structure, and the soil column was exposed to three drying–wetting cycles to explore the effects of hydrogel dosage on soil evaporation and crack evolution. CL may graft into polyacrylic acid under optimal conditions (60% AA neutralization, 4% CL, 1% initiator, and 0.03% crosslinker) to form a porous hydrophilic 3D network. Consequently, the optimized LWR achieved swelling capacities of 1480 g/g and 122 g/g in deionized water and a 0.9% NaCl solution, respectively, showing high water absorbency and salt resistance. During cyclic drying and wetting, soil evaporation was first dominated by the hydrogel’s water retention capabilities; then, it was controlled physically by soil surface cracks. A moderate LWR dosage of 0.3% was used to maintain stable water retention in soil and the intact soil structure, which likely occurred due to its strong water absorption and hypothesized calcium ion bridging anti-cracking interactions. This work overturns the traditional view that a higher hydrogel dosage yields better water retention. Instead, it highlights the importance of conducting a long-term joint evaluation of the hydrogel’s water retention capacity and its resistance to soil dry–wet deformation stress, thereby offering theoretical support for eco-friendly water retention agent design and saline–alkali land remediation. Full article

In this study, alginate hydrogels (A) cross-linked with a mixture of calcium and europium ions (Ca+Eu)A were developed for the first time as potential carriers for the targeted delivery and sustained release of drugs to specific regions of the gastrointestinal tract. Comparative studies were conducted to investigate the effect of the cross-linking agent (Ca²⁺, Eu³⁺, or their mixture) on the physicochemical properties of alginate hydrogels and the release kinetics of metronidazole in media simulating different gastrointestinal environments. Rheological analysis demonstrated that (Ca+Eu)A hydrogels form mechanically robust, highly cross-linked networks. The hydrogels exhibited negligible swelling in an acidic medium (swelling ratio, SR ≈ 1–1.5 g/g); however, in PBS, calcium alginate (CaA) hydrogels swelled 7–8 times more (SR ≈ 42.5 g/g) than hydrogels cross-linked with Eu³⁺ ions or a Ca²⁺/Eu³⁺ mixture (SR = 5–8 g/g). Metronidazole was released 1.5–2 times faster from calcium-cross-linked hydrogels than from hydrogels cross-linked with Eu³⁺ ions or the mixed Ca²⁺/Eu³⁺ system, whereas (Ca+Eu)A hydrogels exhibited a more sustained and uniform release profile. These results demonstrate that the drug release kinetics can be tuned by adjusting the Ca²⁺/Eu³⁺ ratio during alginate cross-linking. Consequently, such hydrogels represent a promising platform for the targeted delivery and controlled release of therapeutic agents, particularly antibiotics, to specific regions of the gastrointestinal tract. Full article

Hydrogel-forming microneedles (HFMNs) are minimally invasive interfaces that access interstitial fluid (ISF) through skin penetration, swelling-mediated uptake, analyte diffusion, and hydrated sensor integration. This review examines HFMN architectures, skin–device interfaces, ISF transport, molecular-recognition and signal-transduction strategies, analytical performance, benchmarking, wear-associated failure modes, therapeutic monitoring, and translational priorities. The field has expanded from glucose sensing to metabolites, ions, hormones, proteins, nucleic acids, microbial and wound biomarkers, and therapeutic drugs, enabled by advances in hydrogel chemistry, conductive networks, nanostructured electrodes, catalysis, affinity recognition, molecular imprinting, optical readouts, and multiplexed wearables. Performance remains context dependent and requires physiological range, calibration stability, biofouling resistance, reliable insertion, validated ISF-reference correlations, and interpretable thresholds. Evidence is strongest in artificial matrices, ex vivo tissue, and animals, while human validation remains limited. Translation will require standardized mechanics and transport reporting, longer wear studies, sterilization-compatible chemistries, scalable manufacturing, and clinical validation. HFMNs may complement rather than replace blood-based diagnostics. Full article

Diabetic foot ulcers (DFUs) constitute a significant global health burden; however, the influence of environmental heavy metals toxicity on their pathogenesis remains insufficiently investigated, particularly within low- and middle-income countries. This systematic review, conducted in strict accordance with PRISMA 2020 guidelines, assesses the impact of heavy metals exposure on the development, progression, and wound-healing kinetics of DFUs. A comprehensive search across PubMed/MEDLINE, Embase, Scopus, and Web of Science identified 32 eligible original studies. Quality appraisal was performed using the Newcastle-Ottawa Scale and SYRCLE’s Risk of Bias tool. Synthesized epidemiological and toxicological data consistently indicate that chronic exposure to non-essential heavy metals, specifically cadmium and lead, significantly augments DFU prevalence and clinical severity, demonstrating a 64% increase in DFU prevalence for each 1 µg/L increase in blood cadmium concentration. Mechanistically, these xenobiotics induce a ‘chronic inflammatory lock’ characterized by severe oxidative stress, sustained NLRP3 inflammasome activation, and the suppression of protective Metallothionein 2A (MT2A) pathways, thereby impeding microvascular angiogenesis. Conversely, deficiencies in essential trace elements, such as zinc and selenium, actively impair extracellular matrix maintenance. Advanced therapeutic interventions, including metal-ion-releasing hydrogels, cell-free exosome therapies, and systemic EDTA chelation, demonstrate significant potential to counteract heavy-metal-induced cellular suppression and facilitate tissue repair. This review underscores the imperative of integrating environmental toxicant screening and targeted detoxification strategies into standard multidisciplinary diabetic foot management. Full article

The application of cellulose-based nanocomposite sorbents as environmentally friendly materials for water purification has emerged as an important and rapidly developing research area. In this context, cellulose nanofibrils (CNFs) and cellulose nanocrystals (CNCs) were successfully extracted from microcrystalline cellulose (MCC) derived from sunflower seed husks (SFHs) and comprehensively characterized. The obtained nanocellulosic materials were subsequently utilized to fabricate nanocomposite hydrogels, designated as HG_CNF and HG_CNC. The results revealed distinct structural and physicochemical characteristics of CNFs and CNCs, which significantly affected the morphology, swelling behavior, and stability of the resulting hydrogels. Swelling experiments conducted under various environmental conditions demonstrated that HG_CNF exhibited higher water uptake and swelling capacity than HG_CNC. Both hydrogels showed maximum swelling under near-neutral conditions (pH ≈ 6.5) and exhibited pronounced sensitivity to changes in ionic strength and solvent polarity. Furthermore, adsorption studies confirmed the effective removal of Cu²⁺ ions by both hydrogels, with HG_CNC exhibiting a slightly higher adsorption capacity than HG_CNF; the degree of sorption was 51.5%. These findings demonstrate that nanocellulose-based hydrogels possess tunable physicochemical properties and considerable potential as sustainable sorbent materials for water treatment, while also offering promising applications in environmental remediation, controlled drug delivery, and biomedical engineering. Full article

Accurate ocean wave sensing in polar and other low-temperature marine environments is of great significance for marine environmental observation, climate research, and navigation safety. However, conventional wave sensors rely on external power supplies and suffer from poor stability under low-temperature and high-salinity conditions, making long-term self-powered waves sensing a significant challenge. Herein, a highly stable composite eutectogel electrode is developed by integrating sodium lignosulfonate, Fe³⁺ crosslinking, Zn²⁺-carboxylate coordination interactions, and a choline chloride/urea deep eutectic solvent (DES). The DES effectively suppresses solvent crystallization and endows the gel with excellent low-temperature tolerance, while the synergistic effect of metal coordination and multiple non-covalent interactions constructs a robust ion-conducting network with enhanced structural stability. Furthermore, eutectogel-based composite electrode architecture is designed to improve electrical conductivity and charge collection efficiency, thereby enabling stable electrical output under harsh marine conditions. Based on the as-prepared eutectogel electrode, a self-powered solid–liquid triboelectric nanogenerator is fabricated for ocean wave-motion sensing. The device can detect the wave amplitude, with an accuracy of 0.2 cm, and sense the frequency of waves ranging from 0.2 Hz to 1.6 Hz. More importantly, the SL-TENG exhibits excellent environmental adaptability, operating reliably in 3.5 wt% simulated seawater and at 0 °C. The current retention ratio reaches approximately 91% at 0 °C, which is significantly higher than that of the hydrogel-based device (≈6%). The remarkably low-temperature and salt-tolerant performance originates from the stable ion-transport network and anti-freezing characteristics of the eutectogel electrode. This work provides an effective strategy for constructing environmentally resilient eutectogel-based triboelectric devices and offers a promising route toward self-powered wave sensing systems for long-term deployment in harsh marine environments. Full article

One of the latest and innovative areas of research in energy is the development of thermoelectric generators (TEGs). A novel family of soft, sustainable energy harvesters, hydrogel-based renewable flexible thermoelectric generators use linked ionic, electronic, and redox processes to transform heat gradients into electrical energy. According to recent research, a hydrogel-based TEG has ionic Seebeck coefficients (S) of the order 10–40 mV K⁻¹, which are tens to hundreds of times greater than those of electronic polymers. Thermal conductivities are modest (~0.3–0.6 W/m·K), ionic conductivities typically vary from 10⁻³ to 10⁻¹ S cm⁻¹, and water-rich gels are naturally soft with elastic moduli ~10³–10⁶ Pa and elongations > 100–800%. Recent developments in the concepts, properties, working mechanism, and potential applications of hydrogel-based thermoelectric generators are the focus of this review paper. We investigate the basic transport processes, such as ionic thermodiffusion, thermoelectric ion–electron coupling, and redox-mediated potential production, that allow thermoelectric conversion in hydrogels. This review identifies bottlenecks such as poor output power under minor gradients, summarize performance parameters, and assess methods to improve efficiency. Wearable and implanted power sources, low-grade waste heat collection, and environmental monitoring are examples of promising applications. Lastly, we describe the research avenues that must be pursued in order to expedite the transition of hydrogel-based thermoelectric generators from lab tests to useful, sustainable energy sources. Therefore, the review can provide fundamental knowledge on hydrogel-based TEGs along with their working principles. Full article

The development of low-cost, environmentally friendly, and electrochemically stable electrode materials remains a significant challenge for supercapacitors. In the present study, composite materials based on a montmorillonite K10 clay support were synthesized and characterized. Coconut shell-derived activated carbon, manganese dioxide (MnO₂), and/or activated carbon (YP-80F) modified with silver nanoparticles were utilized as functional additives to the clay matrix. The aim of this work is to enhance the specific capacitance and electrochemical stability of the materials through a synergistic effect between these individual components. The novelty of this study lies in the integration of montmorillonite K10-based nanocomposites with an ion-exchange hydrogel membrane and in the investigation of the synergistic effects of different functional additives on the electrochemical performance of supercapacitors. The electrodes were fabricated using a casting method, while a commercial membrane, pre-soaked in a sodium sulfate solution, was employed as both separator and electrolyte. The membrane functions as an ion-exchange hydrogel, contributing to high ionic conductivity and reduced interfacial resistance. The electrochemical results indicate that the presence of additives significantly improves electron transport within the system, while the K10 clay support acts as a stable structural framework. The obtained results demonstrate the potential of clay-based nanocomposites integrated into gel-polymer systems for the development of efficient, low-cost, and environmentally friendly next-generation supercapacitors. Full article

Composite hydrogel based on acrylic acid and acrylamide, modified with metal ions (Ni²⁺, Al³⁺, Fe²⁺, Fe³⁺) with concentration 0.3 wt%, were synthesized in water or polyethylene glycol (with a molecular weight of 400 Da) at three monomer ratios (7/3, 1/1, 3/7). Dynamic mechanical analysis shows that the equilibrium modulus of elasticity ($G_e$) of unmodified hydrogels increases with acrylamide content due to higher crosslinking density ($n_e$) and smaller cell size. ${AlCl}_3$ or ${NiCl}_2$ strengthen the structure ($G_e$ increases +53.5% in a 1/1 ratio), while iron salts cause softening (decreases to 90% when using ${FeC}_2{O}_4$). Partial replacement of polyethylene glycol reduces the elasticity but when using ${AlCl}_3$ happens synergistic increase $n_e$ 1.9 times in the ratio 3/7. The self-healing efficiency reaches ~100% for ${FeCl}_3$ in PEG gel in a ratio of 1/1 and 72.1% for ${Fe\left({NH}_4\right)}_2{\left({SO}_4\right)}_2$ hydrogel in 3/7. The electrical conductivity of hydrogels increases in the range of ${Al}^{3+}>{Ni}^{2+}>{Fe}^{3+}$, while matrix based on polyethylene glycol reduces the conductivity by an order of magnitude. For ${Ni}^{2+}$-containing samples, pinched hysteresis loops are observed in both water and polyethylene glycol. In contrast, ${Al}^{3+}$ causes rapid passivation in the water matrix, while in the matrix based on polyethylene glycol, the current–voltage characteristics follow ohmic behavior. The results demonstrate the possibility of directional regulation of the mechanical, electrical, and self-healing efficiency of hydrogels by selecting the ratio of monomers, the nature of the ion modifier, and the type of solvent. Full article

Conductive hydrogels are promising materials for fabricating flexible wearable strain sensors. However, their practical application remains limited by several challenges, including poor mechanical strength, unstable sensitivity, restricted stretchability, and poor structural durability. In this study, a zirconium-reinforced conductive hydrogel (PSPZr) with a dual chemical–physical cross-linked network was designed and developed. In the structural framework, polypyrrole-decorated silk fibroin (SF/PPy) functioned as a conductive reinforcing component, acrylamide and sulfobetaine methacrylate constituted the flexible polymer basis, and zirconium ions (Zr⁴⁺) acted as ionic cross-linkers to construct a dual cross-linked structure and improve mechanical stability. Due to the synergistic contributions of hydrogen bonding, ionic coordination interactions, and SF/PPy, the optimized PSPZr hydrogel exhibited a tensile strength of 166 kPa and a maximum strain 559%. Additionally, it achieved improved elasticity and reliable shape recovery. Furthermore, the optimized PSPZr hydrogel exhibited a broad working range, sensitivity with a gauge factor of 2.8, rapid response, recovery kinetics, and exceptional cycling stability over 1000 stretching–releasing cycles as wearable strain sensors. This performance enabled real-time and accurate monitoring of diverse human motions. Therefore, this study presents a feasible and versatile strategy for developing mechanically robust and electrically stable conductive hydrogel, providing a new pattern for advanced applications in wearable sensors. Full article

Hydrogel scaffolds have emerged as instructive microenvironments for craniofacial tissue regeneration, moving beyond passive cell carriers toward platforms that regulate cell fate, vascularization, immune remodeling, and tissue-specific architecture. This review synthesizes hydrogel-associated strategies across dental pulp, periodontal ligament, gingival, bone marrow, jawbone, endothelial, oral mucosal, induced pluripotent stem cell (iPSC), extracellular vesicle (EV), exosome, secretome, and acellular systems. The evidence indicates that craniofacial hydrogel performance is governed by reciprocal interactions among biological source, scaffold composition, matrix mechanics, spatial architecture, mineral or ionic signaling, growth factor delivery, vesicle-mediated communication, and inflammatory niche modulation. Mineralized and ion-releasing hydrogels most consistently supported osteogenesis and bone repair, whereas extracellular matrix (ECM)-mimetic, peptide, collagen, fibrin, gelatin methacryloyl (GelMA), alginate, hyaluronic acid (HA), and chitosan-based systems enabled pulp–dentin, periodontal, peri-implant, oral mucosal, and soft-tissue reconstruction. Responsive, antimicrobial, antioxidant, conductive, and immunomodulatory hydrogels further expanded the field by targeting diseased microenvironments rather than regeneration alone. Despite strong preclinical evidence, translation remains limited by heterogeneity in scaffold formulations, biological sources, analytical endpoints, defect models, and long-term functional validation. Future progress will require standardized characterization, tissue-specific design criteria, clinically relevant large-animal models, scalable cell-free technologies, and integrated assessment of regeneration, immunity, vascularization, innervation, mechanics, and safety. Full article

Recently, conductive hydrogels have gained extensive applications in flexible wearable electronics and have garnered considerable attention. However, their inherent swelling behaviour and limited mechanical strength have hindered their further development. In this study, a polyacrylamide/sodium alginate (PAM/SA, PS)-based hydrogel with high mechanical strength and anti-swelling properties was prepared by combining mechanical stretching–drying pretreatment with a bimetallic ion (Li⁺/multivalent metal ion) post-soaking strategy. Among multivalent metal ions (Ca²⁺, Al³⁺, and Zr⁴⁺), the Al³⁺-crosslinked hydrogel (PS-Al³⁺) demonstrated outstanding overall performance. It exhibited excellent mechanical properties, with tensile strength, elongation at break, and impact strength reaching 9.71 MPa, 993.53%, and 75 MJ/m³, respectively. Its dense network structure also gave it excellent anti-swelling properties (swelling ratio of 14%). As a strain sensor, the PS-Al³⁺ hydrogel displayed good conductivity (1.33 S/m), high sensitivity (GF = 2.25), fast response (response time of 403 ms), and negligible hysteresis (recovery time of 407 ms). Benefiting from its exceptional resistance to expansion, the material’s sensor response signals in underwater environments are highly consistent with those in air. Furthermore, this sensor has been successfully applied to swimming motion monitoring and data transmission in underwater environments. This study proposes a novel, low-cost, and simple approach for developing flexible sensors suitable for underwater environments. Full article

The world’s current technical developments are mostly dependent on semiconductors. Even though traditional semiconductor materials are important, they have various disadvantages, especially when evaluated against polymer-based alternatives. Hydrogel-based semiconductors provide soft, ionically linked electronic interfaces by combining hydrated, mechanically compliant matrices with electrically active conjugated polymers and composites which can be applied in bioelectronic and thermoelectric generator/cells. Volumetric capacitances are normally in the range of 1–485 F·cm⁻³, demonstrating excellent ion storage, transport capabilities, and electron mobilities for hydrogel semiconductors spanning roughly 0.25 cm²/V·s (measured for n-type P(PyV)-H hydrogel). The fabrication techniques include additive free casting and room-temperature crosslinking, which lower energy input while maintaining electronic performance; typical systems maintain >80% of their conductivity after ${10}^3$–${10}^4$ mechanical cycles. This review study mainly focuses on the design, preparation, application, and prospects of gel/hydrogel-based semiconductors. It gives readers a thorough understanding of the basic ideas that underline their structure and operation. All things considered, this work is a useful tool for engineers and researchers looking to maximize the potential of gel-based semiconductors in next-generation electrical systems. Full article

Conductive hydrogels have emerged as promising candidates for flexible strain sensors owing to their high water content, low elastic modulus, and intrinsic ionic conductivity. However, conventional hydrogel networks often suffer from an inherent trade-off among conductivity, mechanical robustness, and long-term stability, which limits their practical deployment in wearable sensing scenarios. The introduction of metal–ligand coordination bonds into hydrogel networks offers a versatile strategy to address these challenges: dynamic coordination cross-links can dissipate energy under deformation and reform upon unloading, thereby enhancing toughness, enabling self-healing, and contributing to ionic transport. This review focuses on metal-ion-coordinated conductive hydrogels designed for strain-sensing applications. Representative coordination systems based on Fe³⁺, Ca²⁺, Zn²⁺, Al³⁺, Cu²⁺, Ti⁴⁺, and Zr⁴⁺ are surveyed, with emphasis on their characteristic polymer matrices, ligand chemistries, and network-construction strategies. Key sensing-relevant properties—including ionic conductivity, mechanical stretchability, self-healing capability, interfacial adhesion, freezing resistance, and resistance to dehydration—are discussed in relation to coordination network design. Typical application demonstrations in large-deformation motion monitoring and subtle physiological signal detection are reviewed. Unlike existing reviews that survey conductive hydrogels broadly by conductive mechanism or sensor type, this review takes metal-ion coordination as the central organizing principle and systematically traces its influence across the full design chain—from ion–ligand coordination chemistry through network architecture to macroscopic sensing output. By comparatively analyzing seven representative metal-ion systems within a unified framework, this work aims to clarify how the choice of metal ion governs the interplay among conductivity, mechanical robustness, self-healing, and strain sensitivity—a perspective that has not yet been systematically addressed in prior reviews. Finally, current challenges—including the conductivity–mechanics coupling bottleneck, insufficient long-term stability, biosafety concerns for skin-contact deployment, the lack of standardized evaluation protocols, and device-integration barriers—are identified, and future directions for this field are outlined. Full article