Dual-network Hydrogel Research Articles

Novel high-strength, recyclable, microbial-resistant, and freeze-thaw dual topological network hydrogel cooling media

The demand for multifunctional hydrogels, offering high mechanical strength, efficient cooling, and antimicrobial properties, is growing in food preservation. Here, a dual-network (DN) hydrogel PM@Cur, which includes curcumin, is fabricated through chemical crosslinking and hydrogen bonding interactions. The resulting hydrogels can withstand more than five freeze-thaw cycles at −80 °C, and resist brittleness after liquid nitrogen treatment. PM@Cur also exhibits surface hydrophobicity (contact angle >90°) for both water and organic solvents. These properties meet the mechanical, anti-fouling, and recyclable demands for hydrogel coolants. The antimicrobial assays in vitro confirmed that the inclusion of curcumin provided the PM@Cur with photodynamic antimicrobial capacity. Finally, the prepared PM@Cur hydrogel ice cubes have been confirmed to exhibit better anti-melting properties than traditional ice cubes, thus enabling the preservation of strawberries and shrimp. This study presents an innovative solution for producing advanced functional integrated hydrogels, offering a promising and safer option for food coolants.\\.

An antifouling electrochemical biosensor based on chitosan and DNA dual-network hydrogel for ATP quantification in complex biofluids

An antifouling electrochemical biosensor based on chitosan and DNA dual-network hydrogel for ATP quantification in complex biofluids

Self-Powered Machine-Learning-Assisted Material Identification Enabled by a Thermogalvanic Dual-Network Hydrogel with a High Thermopower.

Wearable devices equipped with high-performance flexible sensors that can identify diverse physical information free from batteries are playing an indispensable role in various fields. However, previous studies on flexible sensors have primarily focused on their elasticity and temperature-sensing capability, with few reports on material identification. In this paper, a thermogalvanic dual-network hydrogel is fabricated with [Fe(CN)6]3-/4- as a redox couple and lithium magnesium silicate, Gdm+ and lithium bromideas key electrolytes to optimize the interconnected porous structure of the gel, which shows excellent mechanical and thermoelectric properties with a thermopower as high as 4.01mV K-1. A self-powered material identification ring is developed based on the temperature-triggered thermoelectric response of the gel in conjunction with machine learning, which can actively infer materials without an external power connection by analyzing the voltage signals correlated with interfacial heat transfer produced upon contact with different materials. The proposed gel ring has important applications for future areas such as human-computer interaction and haptic-associated artificial intelligence.

Construction and Performance Study of an Injectable Dual-Network Hydrogel Dressing with Inherent Drainage Function.

With the widespread utilization of moist wound dressings, the extended healing time and increased risk of wound infection caused by excessively moist environments have garnered significant attention. The development of hydrogel dressings that can effectively control the wound moisture level and promote healing is very important. Inspired by the pore-opening perspiration effect of the skin, this study constructed an injectable dual-network hydrogel, CMCS-OSA/AG/MXene, by the composition of a dynamic covalent network of carboxymethyl chitosan and oxidized sodium alginate based on the Schiff base and hydrogen bond network of the thermosensitive low-melting-point agar with the advantage of the upper critical solution temperature (UCST) effect. Under near-infrared (NIR) light stimulation, the CMCS-OSA/AG/MXene hydrogel shows characteristics conducive to rapid removal of wound exudate while maintaining an appropriate moist environment for the wound and excellent antibacterial effects with its photothermal responses. The excellent conductivity of the hydrogel can also promote cell proliferation under external electrical stimulation (ES). Further validation through animal experiments on a full-thickness skin defect model demonstrates the excellent capability of CMCS-OSA/AG/MXene in accelerating wound healing. This work provides an innovative approach to the development of injectable hydrogel dressing materials with inherent drainage functionality and shows a new avenue to wound moisture control and wound healing promotion.

Preparation and characterization of functional dual network hydrogel for motion monitoring in smart bra

The smart bra is a kind of sports underwear with providing health monitoring and comfort protection for women breast in sports. Developing smart sensing materials that combine comfort and functionality for sensing breast condition remains a challenge. Here, natural polysaccharide sodium alginate (SA), acrylamide (AM) monomer and chitosan (CS) and polypyrrole (PPy) in-situ polymerized from pyrole (Py) monomer were used as raw materials to successfully synthesize double network conductive hydrogel by two-step method. The results show that in the hydrogels, the entanglement and interpenetration of macromolecules produce toughness (tensile/compressive strength is ∼0.248 MPa/∼2.836 MPa), elasticity (tensile/compression elastic recovery rate is∼94.06 %/∼98.41 %) and durability (after 30 tensile/compression cycles conducting at 25 %, 50 % and 100 % constant strain keep at high recovery rate). The rich moisture content provides its adhesion (adhesion strength ∼4.7557 kPa) and flexibility (bending stiffness 1.0843 cN cm∼), presenting sufficient adhesion reliability and robustness to different substrates. The addition of PPy enables the hydrogel to have conductivity (6.77 × 10−2 S cm−1) and sensing performance (tensile/compression sensitivity is ∼1.94/∼1.43). The conductive hydrogel, as a flexible strain sensor, shows good adhesion, flexibility, elasticity and sensitivity in application of sports smart bra, can detect both the tensile behavior of skin and the compression state of tissue through its mechano-electricity, and accurately sense the changes of physiological parameters during movement. The conductive hydrogel with high elasticity and strength has broad application prospects in smart bra.

In situ photocrosslinkable hydrogel treats radiation-induced skin injury by ROS elimination and inflammation regulation

The clinical management of radiation-induced skin injury (RSI) poses a significant challenge, primarily due to the acute damage caused by an overabundance of reactive oxygen species (ROS) and the ongoing inflammatory microenvironment. Here, we designed a dual-network hydrogel composed of 5 % (w/v) Pluronic F127 diacrylate and 2 % (w/v) hyaluronic acid methacryloyl, termed the FH hydrogel. To confer antioxidant and anti-inflammation properties to the hydrogel, we incorporated PVP-modified Prussian blue nanoparticles (PPBs) and resveratrol (Res) to form PHF@Res hydrogels. PHF@Res hydrogels not only exhibited multiple free radical scavenging activities (DPPH, ABTS), but also displayed multiple enzyme-like activities (POD-, catalase). Meanwhile, PHF@Res-2 hydrogels significantly suppressed intracellular ROS and promoted the migration of fibroblasts in a high-oxidative stress environment. Moreover, in the RSI mouse model, the PHF@Res-2 hydrogel regulated inflammatory factors and collagen deposition, significantly reduced epithelial hyperplasia, promoted limb regeneration and neovascularization, and accelerated wound healing, outperforming the commercial antiradiation formulation, Kangfuxin. The PHF@Res-2 hydrogel dressing shows great potential in accelerating wound healing in RSI, offering tremendous promise for clinical wound management and regeneration.

Preparation of a chitosan/polyvinyl alcohol-based dual-network hydrogel for use as a potential wound-healing material for the sustainable release of drugs

Treating chronic wounds poses significant challenges in clinical medicine due to bacterial infection, reactive oxygen species (ROS) accumulation, and excessive inflammation. This study aimed to address these issues by developing a wound dressing with antibacterial, antioxidant, and anti-inflammatory properties. Chitosan was functionally modified with acrolein to covalently bind to epigallocatechin gallate (EGCG), enabling a high EGCG load. Subsequently, polyvinyl alcohol (PVA) and EGCG-modified chitosan were crosslinked to prepare a new double-network hydrogel with added cysteine (CSAEC/P50). CSAEC/P50 demonstrated optimal mechanical properties (low swelling rate, high water retention, and optimal flexibility), low hemolysis, high coagulation properties, and antibacterial and antioxidant activities. Cell scratch tests indicated that CSAEC/P50 can promote NIH3T3 cell migration. Immunofluorescence results showed that CSAEC/P50 promoted the transformation of proinflammatory M1 macrophages to anti-inflammatory M2 macrophages. These findings suggest that CSAEC/P50 has significant potential for use in wound dressing applications.

Sustainable and high performance MXene hydrogel with interlocked structure for machine learning-facilitated human-interactive sensing

Wearable epidermal electronics fabricated from MXene-based conductive hydrogels have attracted considerable interest because of their promising prospects in real-time health monitoring and human–computer interaction sensing. However, the development of a sustainable hydrogel with exceptional mechanical toughness, high conductivity, and self-adhesion is crucial to reliably capture signals through polymer network designs that establish robust interactions between MXene nanosheets and network substrates while minimizing electronic waste generated by discarded sensors. This study presents the fabrication of a sustainable conductive MXene-based dual-network hydrogel through skillful assembly of MXene nanosheets, β-cyclodextrin with azobenzene-modified polyacrylic acid chains, and poly (vinyl alcohol) polymer networks. The hydrogel demonstrates exceptional mechanical properties (strength at breaking ∼ 625 kPa, elongation at break ∼ 630 %) attributed to the presence of numerous hydrogen bonds and host–guest interactions, along with superior electrical conductivity (23.65 S/cm) and self-adhesion. The hydrogel demonstrates exceptional sensitivity across a wide range of strains, enabling the detection of various human movements and achieving successful applications in handwriting recognition and sign language translation. Under acidic condition and UV irradiation, the disassembly of AZO and β-CD as well as the untangling of PVA chains entanglement facilitate the release and recycling of MXene. This study presents a technological platform that holds promise for developing conductive hydrogels with enhanced sensing capabilities, catering to the requirements of stretchable electronic skin and intelligent robotic systems.

Air-Writing Recognition Enabled by a Flexible Dual-Network Hydrogel-Based Sensor and Machine Learning.

Accurate air-writing recognition is pivotal for advancing state-of-the-art text recognizers, encryption tools, and biometric technologies. However, most existing air-writing recognition systems rely on image-based sensors to track hand and finger motion trajectories. Additionally, users' writing is often guided by delimiters and imaginary axes which restrict natural writing movements. Consequently, recognition accuracy falls short of optimal levels, hindering performance and usability for practical applications. Herein, we have developed an approach utilizing a one-dimensional convolutional neural network (1D-CNN) algorithm coupled with an ionic conductive flexible strain sensor based on a sodium chloride/sodium alginate/polyacrylamide (NaCl/SA/PAM) dual-network hydrogel for intelligent and accurate air-writing recognition. Taking advantage of the excellent characteristics of the hydrogel sensor, such as high stretchability, good tensile strength, high conductivity, strong adhesion, and high strain sensitivity, alongside the enhanced analytical ability of the 1D-CNN machine learning (ML) algorithm, we achieved a recognition accuracy of ∼96.3% for in-air handwritten characters of the English alphabets. Furthermore, comparative analysis against state-of-the-art methods, such as the widely used residual neural network (ResNet) algorithm, demonstrates the competitive performance of our integrated air-writing recognition system. The developed air-writing recognition system shows significant potential in advancing innovative systems for air-writing recognition and paving the way for exciting developments in human-machine interface (HMI) applications.

Enhanced Low-Temperature Durability of Flexible Zinc–Air Batteries Using NaCl-Doped Dual-Network Hydrogel Electrolytes

Enhanced Low-Temperature Durability of Flexible Zinc–Air Batteries Using NaCl-Doped Dual-Network Hydrogel Electrolytes

Janus-structured evaporator with multiple optimization strategies for sustainable solar desalination

Solar-driven interfacial evaporation (SIE) is an environmentally-friendly and sustainable approach to seawater desalination and offers a promising solution for addressing water scarcity challenge. However, the intricate nature of SIE technology as a complex three-phase system calls for more holistic design strategies. Therefore, we present a comprehensive optimization strategy that integrates various design concepts spanning from optical characteristics and thermal localization enhancement to thermal convection intensification. The enhancement of the localized surface plasmon resonance (LSPR) effect is initially demonstrated by uniformly introducing TiN-NH2 nanoparticles onto the SWCNTs-COOH surface, showcasing remarkable absorbance properties (95.49%). Subsequently, the integration of a dual-network hydrogel is utilized to create a Janus architecture, which can enhance the thermal localization effect with an impressive evaporative efficiency of 92.25%. Finally, perforations are introduced to further improve heat convection, resulting in an exceptional evaporation rate of TiN@CNT/GOF-H1 (3.33 kg m−2 h−1, when calculated according to the real area, the evaporation rate value is 3.75 kg m−2 h−1). Both experimental findings and numerical simulations underscores the efficacy of this multiple-optimization engineered design. Experiment conducted within a customized device has substantiated the enduring cyclic stability and pH resistance to variations, potentially facilitating the spread of practical applications. The integration of multiple optimization strategies is expected to provide valuable insights for the holistic performance enhancement of the SIE evaporators.

Triboelectric Nanogenerator Made with Stretchable, Antibacterial Hydrogel Electrodes for Biomechanical Sensing.

Triboelectric nanogenerators (TENGs) have attracted widespread attention as a promising candidate for energy harvesting due to their flexibility and high power density. To meet diverse application scenarios, a highly stretchable (349%), conductive (1.87 S m-1), and antibacterial electrode composed of carbon quantum dots/LiCl/agar-polyacrylamide (CQDs/LiCl/agar-PAAm) dual-network (DN) hydrogel is developed for wearable TENGs. Notably, the concentration of agar alters the pore spacing and pore size of the DN hydrogel, thereby impacting the network cross-linking density and the migration of conductive ions (Li+ and Cl-). This variation further affects the mechanical strength and conductivity of the hydrogel electrode, thus modulating the mechanical stability and electrical output performance of the TENGs. With the optimal agar content, the tensile strength and conductivity of the hydrogel electrode increase by 211 and 719%, respectively. This enhancement ensures the stable output of TENGs during continuous operation (6000 cycles), with open-circuit voltage, short-circuit current, and transferred charge increasing by 200, 530, and 155%, respectively. Additionally, doping with CQDs enables the hydrogel electrode to effectively inhibit the Gram-negative bacterium Escherichia coli. Finally, the TENGs are utilized as a self-power smart ring for efficient and concise information transmission via Morse code. Consequently, this study introduces a creative approach for designing and implementing multifunctional, flexible wearable devices.

Enhancing the performance of hydrogel strain/pressure sensors via gradient-entanglement-induced surface wrinkling patterns

Due to the advantages of high mechanical compliance and good biocompatibility, conductive hydrogels exhibit great application potential in flexible electronics. As the requirements in high sensitivity and high mechanical performance are increasing, the construction of patterned surfaces has been proven an effective approach, yet most of the common methods are complex and high-cost. Herein, we proposed a facile strategy to construct gradient entanglement dual network (GEDN) hydrogel with spontaneously patterned surface and consequent high surface area, which greatly enhances the sensitivity of hydrogel sensors. The strategy of high entanglement as well as the dual network in hydrogel achieved greatly improved mechanical performance. The prepared polyvinyl alcohol (PVA)/gradient entangled polyacrylamide (PAAm) DN and surface-patterned hydrogel possesses the advantages of excellent stretchability (681 %), high tensile strength (1.01 MPa), toughness (4.23 MJ/m3), and relatively low mechanical hysteresis. Meanwhile, it showed high sensitivity, wide detection range, and rapid response both as strain sensor (GFmax = 10.96, detection range = 681 %, an average response time of 170 ms) and pressure sensor (Smax = 0.17 kPa−1, detection range = 225 kPa, an average response time of 230 ms). In summary, it provides a new strategy for design of the multifunctional high-performance flexible devices, exhibiting great application prospects.

Wearable photonic crystal double network hydrogel sensor based on structural color analysis

Abstract This paper introduces a high-toughness photonic crystal (PhCs) dual-network hydrogel sensor designed for mechanical sensing, which enables quantitative analysis of structural color using the HSB color space. The hydrogel achieves a maximum tensile strain of 250% under a tensile stress of 3.5 MPa, thanks to its dual-network structure comprising a covalently cross-linked polyacrylamide (PAM) network and an ionically cross-linked sodium alginate (SA) network. At an 80% tensile strain, the PAM-SA photonic crystal hydrogel displays a blue shift in the bandgap wavelength of over 130 nm and demonstrates a sensitivity of 1.69 nm/%. The analysis of the force-induced color change in the PAM-SA photonic crystal hydrogel utilized both RGB and HSB color spaces. In the HSB color space, the hue component (H) exhibited a strong linear correlation with strain (R2>0.95), indicating the feasibility of quantitative structural color analysis using HSB. As a wearable sensor, the PAM-SA photonic crystal hydrogel precisely detects human motion via bandgap displacement (R2=0.989) and structural color change (R2=0.978). The PAM-SA PhCs hydrogel, featuring easily accessible color information and high sensitivity, has broad potential applications in wearable devices and mechanical sensors.

Rapid preparation of injectable dual-network hydrogels for biomedical applications using UV-triggered sulfhydryl click reactions

The use of hydrogels to mimic natural cartilage implantation can effectively solve the current problems of insufficient cartilage donors and low rate of injury healing. In particular, injectable hydrogels are less invasive in clinical applications and better able to fill uneven injury surfaces. Here, we prepared NorCS and CS-SH by modifying chitosan with 5-norbornene-2-carboxylic acid and N-Acetyl-L-cysteine, respectively. Dual-network hydrogels were prepared by using UV-triggered thiol-ene click reaction between NorCS and CS-SH and the metal coordination between SA and Ca2+. The prepared hydrogels can be cross-linked quickly and exhibit excellent degradability, self-healing and injectable properties. At the same time, the hydrogel also showed good cytocompatibility and could significantly restore the motor function of mice. This study provides an effective strategy for preparing injectable hydrogels capable of rapid cross-linking.

Binary solvent-reinforced poly (vinyl alcohol)/sodium alginate double network hydrogel as a highly ion-conducting, resilient, and self-healing gel polymer electrolyte for flexible supercapacitors

We present a reliable approach for producing high-performance ion-conducting gel polymer electrolytes (GPEs) based on the sodium chloride (NaCl)-integrated dual network hydrogel of poly (vinyl alcohol)/sodium alginate (PVA/SA) using a binary solvent system of ethylene glycol (EG) and water, providing exceptional ionic conductivity, mechanical strength, and self-healing properties. Different GPEs were produced via the freezing-thawing method using different v/v% of EG and water (named PVA/SA/EG). The best PVA/SA/EG GPE provided a maximum ionic conductivity of 25 mS cm−1, astonishing mechanical strength of 0.42 MPa, exceptional stretchability of 462 %, and remarkable self-healing properties. The binary solvent system- and water-based GPEs were utilized in the construction of symmetric supercapacitors (SSCs) using carbon cloth electrodes and their electrochemical performance were compared. At a current density of 0.5 mA cm−2, the SSC prepared using the best PVA/SA/EG GPE demonstrated a high specific capacity of 577.21 mF cm−2, maintained 94.5 % capacitance after 5000 cycles at 1 mA cm−2, and provided an energy density of 80.14 mWh cm−2 while operating at a power density of 293.3 mW cm−2. The flexible SSC prepared based on this GPE demonstrated outstanding flexibility, while no significant decline in capacitive performance and ionic conductivity was detected when it was bent.

Advanced hydrogel electrolyte with enhanced interfacial adhesion and low-temperature resistant for flexible zinc-ion batteries

Flexible zinc-ion batteries (ZIBs) have great potential in wearable devices due to their excellent mechanical properties, safety and high energy density. However, the poor adhesion of the electrodes in bending, folding and low-temperature environments remains a challenge. In this study, we developed a dual-network hydrogel electrolyte (C-PAM@TA) by incorporating tannic acid (TA) into a cross-linked polyacrylamide (PAM) network. The C-PAM@TA hydrogel electrolyte exhibits strong interfacial adhesion, high ion conductivity, and low-temperature frost resistance. Through experimental and theoretical analyses, we demonstrate that TA helps regulate anion/cation transport channels, weakens the solvation of zinc ions and enables stable and uniform plating/stripping behavior of the zinc metal anode. As a result, the Zn//Zn symmetric cell employing the C-PAM@TA hydrogel electrolyte exhibits outstanding cycling stability (2000 h) at 0.5 mA cm−2. Furthermore, the assembled Zn//C-PAM@TA//fcc@PANI flexible ZIBs can undergo 7000 cycle stability tests, withstand 4500 bending tests and operate normally in a low-temperature environment of −18 ℃. This study successfully develops high-performance, low-temperature resistant flexible ZIBs, providing valuable insights for the design of multifunctional flexible energy storage and wearable electronic devices.

Double-network polyphenol chitosan hydrogels with instant aldehyde-β-cyclodextrin-based structure as potential for treating bacterially infected wounds

Treatment of multiple bacterial infected wounds by eliminating bacteria and promoting tissue regeneration remains a clinical challenge. Herein, dual-network hydrogels (CS-GA/A-β-CD) with snap-structure were designed to achieve curcumin immobilization, using gallic acid-grafted chitosan (CS-GA) and aldehyde-β-cyclodextrin (A-β-CD) crosslinked. A-β-CD were able to achieve rapid dissolution (≥222.35 mg/mL H2O), and helped CS-GA/A-β-CD achieve rapid gelation (≤66.23 s). By adjusting the ratio of aldehyde groups of A-β-CD, mechanical properties and drug release can be controlled. CS-GA/A-β-CD/Cur exhibited excellent antimicrobial properties against S. aureus, E. coli, and P. aeruginosa. In vivo experiments demonstrated that CS-GA/A-β-CD/Cur achieved acute bacterial infection wound healing after 20th days, proving its great potential for wound dressing.

Dual-network hydrogel capsules for controlled molecular transport via pH and temperature responsiveness

We have developed innovative core–shell hydrogel capsules with a dual-network shell structure designed for precise control of molecular transport in response to external stimuli such as pH and temperature. The capsules were fabricated using a combination of microfluidic electrospray techniques and water-in-water (w/w) core–shell droplets templating. The primary network of the shell, calcium alginate (Ca-Alg), with a pKa around 3.4, exhibits sensitivity to pH. The secondary network of the shell, poly(ethylene glycol) methyl ether methacrylate (PEGMA), undergoes a volume phase transition near 60 °C. These properties enable precise molecular transport control in/out of the capsules by modulating the surface charges through varying pH and modifying pore size through temperature changes. Moreover, the dual-network shell structure not only significantly enhances the mechanical strength of the capsules but also improves their stability under external stimulus, ensuring structural integrity during the transport of molecules. This research lays the groundwork for further investigations into the multimodal stimuli-responsive hydrogel systems to control molecular transport, important in applications such as sensors and reactors for chemical cascade reactions.

Withdrawal: Conductive Hydrogel Dressing With High Mechanical Strength for Joint Wound Healing.

Hydrogel wound dressing can accelerate angiogenesis to achieve rapid wound healing, but traditional hydrogel dressings are difficult to meet the repair of joint sites due to their low mechanical strength. Therefore, we constructed the gel system by designing the chemical-physical interpenetrating network structure to achieve high strength and high toughness of the hydrogel. The high-strength double-network hydrogels were synthesized by simple free radical polymerization and low-temperature physicochemical cross-linking in our experiments. The suspension was obtained by green reduction of graphene oxide with carboxymethyl chitosan, followed by the introduction of acrylamide (AM) to form a covalent cross-linked network, which was immersed in ferric chloride solution to form metal ligand bonds, and finally the chemical-physical dual cross-linked network hydrogel wound dressing was prepared. Here, reduced graphene oxide can enhance electrical conductivity and excellent near-infrared photothermal effect to the hydrogel. The cell viability of this novel wound dressing was above 90.0%, its hemolysis rate was below 2.0%, and the electrical conductivity could reach (6.89 ± 0.07 (mS/cm)). In addition, the stress-strain curve demonstrated that the double cross-linked network hydrogel could reach a stress of more than 0.8MPa at 82.0% strain, and the cyclic compression experiment shows that it can still recover its original shape after five times of repeated compression. This work can provide a reference for the exploitation of high mechanical strength hydrogel wound dressings with good electrical conductivity and near-infrared photothermal effect. This article is protected by copyright. All rights reserved.