Search Results (227)

Conductive hydrogels are attractive for flexible electronics, but their practical use is often limited by resistance drift during repeated deformation and performance degradation at low temperatures. Here, core–shell polyaniline-coated polyacrylonitrile (PANi@PAN) electrospun nanofibers were incorporated into a polyacrylamide/hydroxypropyl cellulose (PAM/HPC) hydrogel matrix to construct a hybrid conductive network. The PANi shell serves as an electronic pathway alongside ionic conduction in the hydrated polymer network, leading to markedly improved electromechanical stability. The resistance drift is about 11% after 2000 stretching–relaxation cycles at 0–100% strain, about 12 times lower than that of the nanofiber-free hydrogel. Stable electrical responses are maintained under large deformation, with a resistance drift as low as 3.3% over a strain range of 0–400%. The hydrogels show a conductivity of 0.32 S m⁻¹ while retaining high stretchability (>600%). An ethylene glycol/water binary solvent is used to suppress ice formation and improve moisture retention, allowing stable electromechanical performance at −15 °C over 500 cycles. The hydrogel also adheres reliably to human skin (about 10.25 kPa) and functions as a conformal strain sensor without extra fixation. Full article

Flexible conductive hydrogels hold great promise in wearable electronics and biomonitoring applications, yet their practical use is constrained by issues such as poor low-temperature tolerance, susceptibility to dehydration, and limited multifunctional sensing capabilities. This study successfully synthesized a dual-conductive lithium-ion and calcium-ion hydrogel based on acrylamide/gelatin via a simplified low-temperature one-pot polymerization method. At 60 °C, mixing acrylamide, gelatin, lithium chloride, and calcium chloride within 40 min constructed a network structure featuring covalent bonds, ionic bonds, and hydrogen bonds. The resulting material exhibited exceptional extensibility with a break elongation of 1408.5% and tensile strength of 134.2 kPa while maintaining strong adhesion to nine different substrates. It retained flexibility at −20 °C and demonstrated minimal mass loss (3% of initial value) after 10 days of aging. As a sensor, this hydrogel reliably responds to pressure, temperature, large-amplitude body movements, and subtle physiological signals like pulse and vocal cord vibrations. In animal simulation monitoring, its electrical resistance signals increased linearly with model body weight and remained stable between −20 °C and 20 °C. These results demonstrate the hydrogel’s broad application potential in wearable sensing, ecological monitoring, and smart agriculture. Full article

Background/Objectives: Wound management presents a substantial clinical challenge due to the rising incidence of chronic wounds, infections, and the limitations of conventional dressings in creating an ideal healing microenvironment. This review aims to provide a comprehensive overview of advanced smart hydrogel platforms designed to improve wound healing outcomes, focusing on their capacity to respond adaptively to physiological and external stimuli. Methods: This article analyzes the core characteristics of smart hydrogels, specifically examining stimuli-responsive systems (pH, temperature, enzyme, light, and electricity). The review evaluates advanced configurations—including injectable, self-healing, and 3D-printable systems—and functionalized hydrogels integrated with antimicrobials, drugs, and nanocomposites. Additionally, essential characterization methodologies, biological assessments, and regulatory considerations for clinical translation are synthesized. Results: The literature, which is predominantly preclinical in nature, indicates that functionalized hydrogels significantly enhance tissue regeneration, angiogenesis, and infection control compared to traditional methods. Conductive hydrogels utilizing bioelectrical signals show particular promise in accelerating the healing process. While current clinical applications and commercial products demonstrate efficacy, significant barriers remain regarding large-scale manufacturing and regulatory approval. Conclusions: Smart hydrogels represent a transformative approach to precision wound management, offering superior adaptability and therapeutic delivery. To achieve widespread clinical adoption, future research must address manufacturing scalability and focus on emerging trends, such as the integration of biosensors and AI-powered monitoring systems, to create fully intelligent wound care solutions. Full article

Transcutaneous electrical nerve stimulation (TENS) is constrained by high skin impedance and unstable electrode contact. This study proposes a novel composite electrode system comprising a polyvinyl alcohol/silver (PVA/Ag) microneedle array and a highly conductive polyacrylamide/lithium chloride (PAAm/LiCl) hydrogel. The PVA/Ag microneedles (~365 µm in height, ~48 µm tip diameter) possess sufficient mechanical strength to penetrate the stratum corneum, establishing a low-resistance pathway. The complementary PAAm/LiCl hydrogel exhibits high conductivity (10.28 S/m) and mechanical flexibility, further optimizing the interface contact. The experimental results demonstrate that this composite system achieves low electrochemical impedance and induces stable, clear electromyographic responses in vivo. It effectively addresses the common issues of electrode detachment and signal attenuation associated with conventional electrodes, offering a promising hardware solution for efficient and comfortable wearable rehabilitation devices. Full article

Neural regeneration requires an optimal environment, including structural, chemical, mechanical, and electrical properties. Alginate (Alg) and graphene oxide (GO) are promising biomaterials for nerve tissue engineering, as Alg provides biocompatibility and hydrogel formation, while GO enhances mechanical strength and conductivity. For this study, GO was synthesized using the modified Hummer’s method, and Alg–GO scaffolds with varying GO concentrations were developed. FTIR spectroscopy confirmed the successful incorporation of GO into the Alg matrix, while UV–Vis and photoluminescence analyses demonstrated GO-induced modifications of the optical properties. Thermal analysis revealed improved stability with increasing GO content, whereas swelling tests showed enhanced water uptake and retention. Conductivity measurements indicated a clear improvement in electrical conductivity, particularly at moderate GO concentrations. SEM imaging confirmed a homogeneous distribution of GO within the Alg matrix, with structural uniformity across all samples. Cytocompatibility was assessed using SH–SY5Y neuroblastoma cells through MTT, LDH, and LIVE/DEAD assays. All composites supported cell attachment, viability, and proliferation, with GO concentrations up to 6% promoting optimal cell growth without inducing cytotoxicity. In contrast, excessive GO content (9%) resulted in reduced proliferation, although biocompatibility was maintained. These results highlight the potential of Alg–GO scaffolds as promising candidates for neural tissue engineering. The findings demonstrate the potential of Alg–GO scaffolds as advanced biomaterials for regenerative medicine. Future research should focus on in vivo evaluations to confirm their therapeutic applicability. Full article

Deep eutectic solvent (DES), when used as the continuous phase of eutectogels, can significantly improve their electrical and mechanical properties due to its excellent conductivity, freeze resistance and chemical stability. The development of eutectogels effectively solves the key limitations of traditional hydrogels and organogels, such as low-temperature freezing, high-temperature volatilization, and organic solvent leakage. It also realizes the collaborative optimization of environmental friendliness and comprehensive performance, which makes it show broad application prospects in the field of flexible sensing. This review summarizes the design principles, material selection, sensing mechanisms, and flexible sensing applications of eutectogels. By examining the design of eutectogels, the selection of DES, and the synthesis of the gel network, it provides a theoretical basis for the development of eutectogel-based sensor devices. A detailed description of the sensing mechanism is provided to elucidate the signal generation and transition in eutectogels toward the purpose of the practical applications. Finally, the application prospects of eutectogels for high-performance sensors and detection devices are discussed. Additionally, we provide a theoretical support for their structural design, performance optimization, and practical application. Full article

The application of MXene–polymer composites to wearable and implantable medical devices requires the development of hydrophilic and biocompatible MXene–polymer hydrogel composites with high electromechanical response, flexibility, and durability. Here, we formulate low weight percentage MXene–hydrogel copolymer inks enabling the direct light processing (DLP) of Ti₃C₂T_x MXene–polyvinyl alcohol (PVA)–polyacrylic acid (PAA)–hydrogel composites. The low wt% MXene–PVA–PAA composites demonstrate high biocompatibility, mechanical flexibility, high sensitivity and high precision for sensing acute bending angles. The sub-millidegree angle resolution of these electromechanical sensors demonstrates their suitability for applications such as the highly precise tracking of joint movements. In addition, the synthesized MXene membranes show promise for applications in osmotic energy conversion, with a harvested electric power density of 6.79 Wm⁻². Full article

Developing functional agricultural materials that synchronize nutrient release, water retention, and soil amendment is crucial to advancing resource-efficient, sustainable farming systems. However, integrating these multifunctional properties within a single material remains a significant challenge. In this work, we fabricated a multifunctional hydrogel (CPAUH) via a one-pot synthesis strategy, which was composed of carboxylated cellulose nanofibers as a rigid network combined with poly(AA-co-KAA), forming a semi-interpenetrating network (semi-IPN) for loading urea and humic acid. The structure and properties of hydrogels were characterized by FTIR, TGA, SEM, and XPS. The CPAUH exhibited outstanding mechanical strength (0.169 MPa), water absorption capacity (121.65 g g⁻¹), and retained 118 g g⁻¹ after three absorption–desorption cycles, demonstrating remarkable structural stability. Nutrient release kinetics revealed sustained-release behavior, with cumulative elution of only 66.91% for urea and 92.45% for humic acid over 15 days. Under salt stress, the 1.5% CPAUH amendment (P2) markedly enhanced wheat growth compared with the non-amended control (P0), as reflected by significant increases in plant height, chlorophyll content, fresh weight, dry weight, and nitrogen uptake. Concurrently, CPAUH application effectively improved soil conditions by reducing electrical conductivity by 39.16% (to 4.38 mS·cm⁻¹). These collective findings of CPAUH hydrogel offer substantial potential as a multifunctional soil amendment for enhancing water-fertilizer efficiency, reclaiming saline–alkali soils, and improving crop productivity under resource-limited conditions. Full article

With the rapid development of artificial intelligence and wearable electronics, there is an increasing demand for skin-like, flexible, and self-powered sensors capable of continuously perceiving mechanical stimuli and human motions. Triboelectric nanogenerator (TENG)-based sensors incorporating stretchable conductive gels represent a promising approach to meet these requirements by combining soft mechanical compliance with efficient electromechanical signal transduction. However, conventional metallic or composite electrodes often suffer from mechanical mismatch with soft skin-like systems, motivating the exploration of intrinsically soft and stretchable conductive gels. In this review, we present a comprehensive and structured overview with comparative perspectives of stretchable skin-like conductive gel-based triboelectric devices. First, different classes of conductive gels, including hydrogels, organogels, ionogels, and other emerging gel systems, are systematically summarized and compared in terms of their composition, crosslinking strategies, conductivity, and mechanical characteristics. Next, the pivotal role of conductive gels in bridging skin-like sensing functions and triboelectric applications is elucidated, highlighting how their intrinsic softness, stretchability, self-healing capability, and interfacial conformability enable intimate skin contact and reliable electromechanical coupling. The key performance attributes of gel-based skin-like triboelectric sensors, including stretchability, self-healing behavior, optical and thermal tolerance, electrical durability, and environmental stability, are critically discussed with representative examples and comparative analysis. Typical device configurations, such as thin-film, fiber-shaped, and textile-based architectures, are further reviewed to illustrate structure–function relationships and application-oriented design strategies. Finally, current challenges, limitations, and future research directions for stretchable conductive gel-based triboelectric systems are outlined, aiming to provide practical guidelines and insights for the rational design of high-performance skin-like triboelectric sensors based on conductive gels. Full article

Metallogels constitute a rapidly expanding class of hybrid soft materials in which metal ions, metal complexes, or metal-containing nanoparticles play a decisive structural and functional role within a three-dimensional gel network. Their unique combination of supramolecular assembly, metal-ligand coordination, and dynamic network behaviour provides tunable mechanical, optical, electrical, redox, and catalytic properties that are not accessible in conventional hydrogels or organogels. This review systematically summarises current knowledge on metallogels, beginning with a classification based on matrix type, dominant metal interaction and functional output, spanning metallohydrogels, metal-organic gels, metal-phenolic gels, nanoparticle-based gels, polymer-based metallogels and low-molecular-weight metallogels. Key synthesis pathways are discussed, including coordination-chemistry-driven formation, metal-ligand self-assembly, in situ reduction, diffusion-mediated strategies, sol-gel-like polymerisation, enzyme-assisted routes, and bio-derived fabrication. Particular emphasis is placed on structure-function relationships that enable the development of catalytic, conductive, luminescent, antimicrobial, and biomedical metallogels. The examples compiled here highlight the versatility and transformative potential of metallogels in next-generation soft technologies, including sensing, energy conversion, wound healing, drug delivery, and emerging applications such as soft electronics and on-skin catalytic or bioactive patches. By mapping current progress and emerging design principles, this review aims to support the rational engineering of metallogels for advanced technological and biomedical applications Full article

Diabetic wounds are a major clinical challenge, driven by hyperglycemia, oxidative stress, persistent inflammation, and bacterial infection. Conventional dressings offer limited benefit, creating demand for advanced therapeutic strategies. This review analyzes hydrogel-based wound dressings and flexible electronic devices. Hydrogels are categorized by angiogenesis promotion, antioxidant activity, anti-inflammatory regulation, antibacterial action, and electrical conductivity. Flexible electronics are examined for adaptability, sensitivity, and real-time monitoring potential. Hydrogels maintain moist environments, support tissue regeneration, and deliver multifunctional bioactivity. Growth factor-loaded and electroactive hydrogels promote angiogenesis. Reactive oxygen species (ROS)-responsive systems restore redox balance. Anti-inflammatory and antibacterial hydrogels regulate macrophages and reduce infection risk. Conductive hydrogels accelerate healing through electrical stimulation. Flexible electronics provide continuous monitoring, intelligent feedback, and remote management, enhancing treatment precision. Their integration with hydrogels represents a paradigm shift from passive dressings to active diagnostic and therapeutic systems. Challenges remain in material design, interfacial stability, and long-term biocompatibility. These issues guide future innovation and clinical translation, offering a foundation for smart diabetic wound management. Full article

Background: Chronic diabetic wounds, particularly diabetic foot ulcers (DFUs), are prone to recurrent infection and delayed healing, resulting in substantial morbidity, mortality, and economic burden. Multifunctional wound dressings that combine antibacterial, antioxidant, conductive, and self-healing properties may help to address the complex microenvironment of chronic diabetic wounds. Methods: In this study, ε-poly-L-lysine and amino-terminated polyethylene glycol were grafted onto carboxylated single-walled carbon nanotubes (SWCNTs) via amide coupling to obtain ε-PL-CNT-PEG. Aminated chondroitin sulfate (CS-ADH) and a catechol–metal coordination complex of protocatechualdehyde and Fe³⁺ (PA@Fe) were then used to construct a dynamic covalently cross-linked hydrogel network through Schiff-base chemistry. The obtained hydrogels (Gel0–3, Gel4) were characterized for photothermal performance, rheological behavior, microstructure, swelling/degradation, adhesiveness, antioxidant capacity, electrical conductivity, cytocompatibility, hemocompatibility, and antibacterial activity in the presence and absence of near-infrared (NIR, 808 nm) irradiation. Results: ε-PL-CNT-PEG showed good aqueous dispersibility, NIR-induced photothermal conversion, and improved cytocompatibility after surface modification. Incorporation of ε-PL-CNT-PEG into the PA@Fe/CS-ADH network yielded conductive hydrogels with porous microstructures and storage modulus (G′) higher than loss modulus (G′′) over the tested frequency range, indicating stable gel-like behavior. The hydrogels exhibited self-healing under alternating strain and macroscopic rejoining after cutting. Swelling and degradation studies demonstrated pH-dependent degradation, with faster degradation in mildly acidic conditions (pH 5.0), mimicking infected chronic diabetic wounds. The hydrogels adhered to diverse substrates and tolerated joint movements. Gel4 showed notable DPPH• and H₂O₂ scavenging (≈65% and ≈60%, respectively, within several hours). The electrical conductivity was 0.19 ± 0.0X mS/cm for Gel0–3 and 0.21 ± 0.0Y mS/cm for Gel4 (mean ± SD, n = 3), falling within the range reported for human skin. In vitro, NIH3T3 cells maintained >90% viability in the presence of hydrogel extracts, and hemolysis ratios remained below 5%. Hydrogels containing ε-PL-CNT-PEG displayed enhanced antibacterial effects against Escherichia coli and Staphylococcus aureus, and NIR irradiation further reduced bacterial survival, with some formulations achieving near-complete inhibition under low-power (0.2–0.3 W/cm²) 808 nm irradiation. Conclusions: A dynamic, conductive hydrogel based on PA@Fe, CS-ADH, and ε-PL-CNT-PEG was successfully developed. The hydrogel combines photothermal antibacterial activity, antioxidant capacity, electrical conductivity, self-healing behavior, adhesiveness, cytocompatibility, and hemocompatibility. These properties suggest potential for application as a wound dressing for chronic diabetic wounds, including diabetic foot ulcers, although further in vivo studies are required to validate therapeutic efficacy. Full article

Conductive hydrogels that simultaneously exhibit high mechanical robustness, reliable electrical conductivity, and interfacial adhesion are highly desirable for flexible sensing applications; however, achieving these properties in a single system remains challenging due to intrinsic structure–property trade-offs. Herein, a multifunctional conductive hydrogel (ASP hydrogel) is developed based on a polyacrylamide (PAM)/sodium alginate (SA) double-network architecture using a gallic acid (GA)–Fe³⁺–pyrrole (Py) coupling strategy. In this design, GA provides metal-coordination sites for Fe³⁺, while Fe³⁺ simultaneously serves as an oxidant to trigger the in situ polymerization of pyrrole, enabling the homogeneous integration of polypyrrole (PPy) conductive networks within the hydrogel matrix. The resulting ASP hydrogel exhibits a markedly enhanced fracture strength of 2.95 MPa compared with PAM (0.26 MPa) and PAM–SA (0.22 MPa) hydrogels, together with stable electrical conductivity and reproducible strain-dependent electrical responses. Moreover, the introduction of dynamic metal–phenolic coordination and hydrogen-bonding interactions endows the hydrogel with intrinsic self-healing capability and strong adhesion to diverse substrates. Rather than relying on simple filler incorporation, this work demonstrates an integrated network design that balances mechanical strength, conductivity, and adhesion, providing a versatile material platform for flexible strain sensors and wearable electronics. Full article

Conductive hydrogels have gained considerable interest in the biomedical field because they provide a soft, hydrated, and electrically active microenvironment that closely resembles native tissue. Their unique combination of electrical conductivity and biocompatibility enables monitoring and modulation of biological activities. With the rapid development of conductive hydrogel technologies in recent years, a comprehensive overview is needed to clarify their biological functions and the latest biomedical applications. This review first summarizes the fundamental design strategies, fabrication methods, and conductive mechanisms of conductive hydrogels. We then highlight their applications in wearable device, implanted bioelectronics, wound healing, neural regeneration and cell regulation, accompanied by discussions of the underlying biological and electroactive mechanisms. Potential challenges and future directions, including strategies to optimize fabrication methods, balance key material properties, and tailor conductive hydrogels for diverse biomedical applications, are also highlighted. Finally, we discuss the existing limitations and future perspectives of the biomedical applications of conductive hydrogels. We hope that this article may provide some useful insights to support their further development and potential biomedical applications. Full article

Tissue engineering is entering a new era, one defined not by passive scaffolds but by smart, adaptive biomaterials that can sense, think, and respond to their surroundings. These next-generation materials go beyond simply providing structure; they interact with cells and tissues in real time. Recent advances in mechanically responsive hydrogels and dynamic crosslinking have demonstrated how materials can adjust their stiffness, repair themselves, and transmit mechanical cues that directly influence cell behavior and tissue growth. Meanwhile, in vivo studies are demonstrating how engineered materials can harness the body’s own mechanical forces to activate natural repair programs without relying on growth factors or additional ligands, paving the way for minimally invasive, force-based therapies. The emergence of electroactive and conductive biomaterials has further expanded these capabilities, enabling two-way electrical communication with excitable tissues such as the heart and nerves, supporting more coordinated and mature tissue growth. Meanwhile, programmable bioinks and advanced bioprinting technologies now allow for precise spatial patterning of multiple materials and living cells. These printed constructs can adapt and regenerate after implantation, combining architectural stability with flexibility to respond to biological changes. This review brings together these cross-cutting advances, dynamic chemical design, mechanobiology-guided engineering, bioelectronic integration, and precision bio-fabrication to provide a comprehensive view of the path forward in this field. We discuss key challenges, including scalability, safety compliance, and real-time sensing validation, alongside emerging opportunities such as in situ stimulation, personalized electromechanical sites, and closed loop “living” implants. Taken together, these adaptive biomaterials represent a transformative step toward information-rich, self-aware scaffolds capable of guiding regeneration in patient-specific pathways, blurring the boundary between living tissue and engineered material. Full article