Motion Detecting, Temperature Alarming, and Wireless Wearable Bioelectronics Based on Intrinsically Antibacterial Conductive Hydrogels

Biocompatible AgInS2@hydrogel microelectrode with enhanced photoelectrochemical sensitivity for real-time in vivo dopamine monitoring

In situ monitoring of neurochemical dynamics is pivotal for understanding brain function and diagnosing neurological disorders. Conventional photoelectrochemical (PEC) sensors face limitations due to poor tissue compatibility and insufficient light penetration depth in vivo. Herein, we present a transparent and conductive hydrogel-based microelectrode (AgInS2@hydrogel) that integrates a biocompatible topological hydrogel with an AgInS2 semiconductor for selective dopamine (DA) detection. The hydrogel, synthesized via copolymerization of acrylamide and PR-PEGMA crosslinker with PEDOT:PSS as a conductive filler, exhibits tissue-matching elasticity (Young's modulus ≈118 kPa) and high conductivity (177 mS m-1). The AgInS2 semiconductor, in situ grown on the hydrogel surface, generates reactive oxygen species under visible light, triggering DA polymerization into polydopamine (PDA). This process establishes a self-enhancing feedback loop between AgInS2 and PDA, enabling selective DA detection with a linear range of 0.2-4 μM and limit of detection of 64 nM. Implanted into the mouse striatum, the sensor successfully tracked dynamic DA fluctuations induced by nomifensine maleate, demonstrating its capability for real-time in vivo neurochemical analysis. This work advances the development of minimally invasive, high-sensitivity tools for brain research.

Recent advances in nanomaterials for wearable devices: classification, synthesis, and applications

Wearable devices have a wide range of applications in mobile electronics, energy storage, human movement and health monitoring due to their flexibility, comfort and portability. Nanomaterials have excellent electrical conductivity and mechanical properties due to being in the nanoscale range with small size and surface effects that alter electrical properties. This paper focuses on the progress of research on advanced nanomaterials in the wearable field, including the classification of nanomaterials, physical, chemical, microwave-assisted, and biological synthesis for nanomaterials, as well as spinning, textile coating, and three-dimensional printing of fabricating functional layers of nanodevices. In addition, its importance in thermal management devices, telemedicine and monitoring, assistance for the disabled and mental health and sleep monitoring is analyzed. Finally, the current challenges and future directions of the field are discussed. This review will be of great interest and inspiration for developing and improving novel nanomaterials and advanced wearable nanodevices.

Advances in conducting nanocomposite hydrogels for wearable biomonitoring

Recent advancements in wearable biosensors and bioelectronics have led to innovative designs for personalized health management devices, with biocompatible conducting nanocomposite hydrogels emerging as a promising building block for soft electronics engineering. In this review, we provide a comprehensive framework for advancing biosensors using these engineered nanocomposite hydrogels, highlighting their unique properties such as high electrical conductivity, flexibility, self-healing, biocompatibility, biodegradability, and tunable architecture, broadening their biomedical applications. We summarize key properties of nanocomposite hydrogels for thermal, biomechanical, electrophysiological, and biochemical sensing applications on the human body, recent progress in nanocomposite hydrogel design and synthesis, and the latest technologies in developing flexible and wearable devices. This review covers various sensor types, including strain, physiological, and electrochemical sensors, and explores their potential applications in personalized healthcare, from daily activity monitoring to versatile electronic skin applications. Furthermore, we highlight the blueprints of design, working procedures, performance, detection limits, and sensitivity of these soft devices. Finally, we address challenges, prospects, and future outlook for advanced nanocomposite hydrogels in wearable sensors, aiming to provide a comprehensive overview of their current state and future potential in healthcare applications.

Self-Healing, Electrically Conductive, Antibacterial, and Adhesive Eutectogel Containing Polymerizable Deep Eutectic Solvent for Human Motion Sensing and Wound Healing

Flexible electronic devices such as wearable sensors are essential to advance human-machine interactions. Conductive eutectogels are promising for wearable sensors, despite their challenges in self-healing and adhesion properties. This study introduces a multifunctional eutectogel based on a novel polymerizable deep eutectic solvent (PDES) prepared by the incorporation of diallyldimethylammonium chloride (DADMAC) and glycerol in the presence of polycyclodextrin (PCD)/dopamine-grafted gelatin (Gel-DOP)/oxidized sodium alginate (OSA). The synthesized eutectogel has reversible Schiff-base bonds, hydrogen bonds, and host-guest interactions, which enable rapid self-healing upon network disruption. GPDO-15 eutectogel has significant tissue adhesion, high stretchability (419%), good ionic conductivity (0.79 mS·cm-1), and favorable antibacterial and self-healing properties. These eutectogels achieve 90% antibacterial effect, show excellent biocompatibility, and can be used as sensors to monitor human activities with strong stability and durability. The in vivo studies indicate that the eutectogels can improve the wound healing process which makes them an effective option for biological dressings.

Polyvinyl alcohol /chitosan biomimetic hydrogel enhanced by MXene for excellent electromagnetic shielding and pressure sensing

Traditional electromagnetic shielding materials are difficult to realize practical applications due to excessive fillers, poor mechanical properties, and difficulty in preservation, etc. Hydrogel is a biomaterial with good biocompatibility and sustainability, which not only can overcome the aforementioned issues, but its biomimetic hierarchical porous structure also enables multifunctional applications. In this paper, a honeycomb-like unidirectional porous wall structured hydrogel is prepared by a simple freeze-thaw cycle and salting out method. Polyvinyl alcohol (PVA) and chitosan (CS) form a double cross-linked network (DN) enhanced by MXene, resulting in excellent mechanical and flexibility. Due to the synergistic effects of MXene, water, Fe3O4, abundant interfaces and micrometer porous wall structure, the electromagnetic shielding performance is enhanced. EMI SE increases by 30.7 dB as the MXene concentration increases from 0 to 1.5 wt%, and EMI SE increases from 7.9 to 66.7 dB as the water content increases from 0 to 76 %. Besides this, we encapsulate the hydrogel into a simple sensor, the signal response is rapid, the response /recovery time is 50/100 ms respectively, and it exhibits good sensitivity (0.0187 kPa-1). Different signals are generated based on variations in pressure, which holds significant importance for the development of wearable flexible sensors and information encoding.

A Review of Conductive Hydrogel-Based Wearable Temperature Sensors

Conductive hydrogel has garnered significant attention as an emergent candidate for diverse wearable sensors, owing to its remarkable and tailorable properties such as flexibility, biocompatibility, and strong electrical conductivity. These attributes make it highly suitable for various wearable sensor applications (e.g., biophysical, bioelectrical, and biochemical sensors) that can monitor human health conditions and provide timely interventions. Among these applications, conductive hydrogel-based wearable temperature sensors are especially important for healthcare and disease surveillance. This review aims to provide a comprehensive overview of conductive hydrogel-based wearable temperature sensors. First, this work summarizes different types of conductive fillers-based hydrogel, highlighting their recent developments and advantages as wearable temperature sensors. Next, this work discusses the sensing characteristics of conductive hydrogel-based wearable temperature sensors, focusing on sensitivity, dynamic stability, stretchability, and signal output. Then, state-of-the-art applications are introduced, ranging from body temperature detection and wound temperature detection to disease monitoring. Finally, this work identifies the remaining challenges and prospects facing this field. By addressing these challenges with potential solutions, this review hopes to shed some light on future research and innovations in this promising field.

Recent Advances of Stretchable Nanomaterial-Based Hydrogels for Wearable Sensors and Electrophysiological Signals Monitoring

Electrophysiological monitoring is a commonly used medical procedure designed to capture the electrical signals generated by the body and promptly identify any abnormal health conditions. Wearable sensors are of great significance in signal acquisition for electrophysiological monitoring. Traditional electrophysiological monitoring devices are often bulky and have many complex accessories and thus, are only suitable for limited application scenarios. Hydrogels optimized based on nanomaterials are lightweight with excellent stretchable and electrical properties, solving the problem of high-quality signal acquisition for wearable sensors. Therefore, the development of hydrogels based on nanomaterials brings tremendous potential for wearable physiological signal monitoring sensors. This review first introduces the latest advancement of hydrogels made from different nanomaterials, such as nanocarbon materials, nanometal materials, and two-dimensional transition metal compounds, in physiological signal monitoring sensors. Second, the versatile properties of these stretchable composite hydrogel sensors are reviewed. Then, their applications in various electrophysiological signal monitoring, such as electrocardiogram monitoring, electromyographic signal analysis, and electroencephalogram monitoring, are discussed. Finally, the current application status and future development prospects of nanomaterial-optimized hydrogels in wearable physiological signal monitoring sensors are summarized. We hope this review will inspire future development of wearable electrophysiological signal monitoring sensors using nanomaterial-based hydrogels.

Bioprinting of Stable Bionic Interfaces Using Piezoresistive Hydrogel Organoelectronics

Bionic tissues offer an exciting frontier in biomedical research by integrating biological cells with artificial electronics, such as sensors. One critical hurdle is the development of artificial electronics that can mechanically harmonize with biological tissues, ensuring a robust interface for effective strain transfer and local deformation sensing. In this study, a highly tissue-integrative, soft mechanical sensor fabricated from a composite piezoresistive hydrogel. The composite not only exhibits exceptional mechanical properties, with elongation at the point of fracture reaching up to 680%, but also maintains excellent biocompatibility across multiple cell types. Furthermore, the material exhibits bioadhesive qualities, facilitating stable cell adhesion to its surface. A unique advantage of the formulation is the compatibility with 3D bioprinting, an essential technique for fabricating stable interfaces. A multimaterial sensorized 3D bionic construct is successfully bioprinted, and it is compared to structures produced via hydrogel casting. In contrast to cast constructs, the bioprinted ones display a high (87%) cell viability, preserve differentiation ability, and structural integrity of the sensor-tissue interface throughout the tissue development duration of 10 d. With easy fabrication and effective soft tissue integration, this composite holds significant promise for various biomedical applications, including implantable electronics and organ-on-a-chip technologies.

Unzipped carbon nanotubes assisted 3D printable functionalized chitosan hydrogels for strain sensing applications

Developing multifunctional hydrogels for wearable strain sensors has received significant attention due to their diverse applications, including human motion detection, personalized healthcare, soft robotics, and human-machine interfaces. However, integrating the required characteristics into one component remains challenging. To overcome these limitations, we synthesized multifunctional hydrogels using carboxymethyl chitosan (CMCS) and unzipped carbon nanotubes (f-CNTs) as strain sensor via a one-pot strategy. The polar groups in CMCS and f-CNTs enhance the properties of the hydrogels through different interactions. The hydrogels show superior printability with a uniformity factor (U) of 0.996 ± 0.049, close to 1. The f-CNTs-assisted hydrogels showed improved storage modulus (8.8 × 105 Pa) than the pure polymer hydrogel. The hydrogels adequately adhered to different surfaces, including human skin, plastic, plastic/glass interfaces, and printed polymers. The hydrogels demonstrated rapid self-healing and good conductivity. The biocompatibility of the hydrogels was assessed using human fibroblast cells. No adverse effects were observed with hydrogels, showing their biocompatibility. Furthermore, hydrogels exhibited antibacterial potential against Escherichia coli. The developed hydrogel exhibited unidirectional motion and complex letter recognition potential with a strain sensitivity of 2.4 at 210 % strain. The developed hydrogels could explore developing wearable electronic devices for detecting human motion.

Injectable Conductive Hydrogel with Self-Healing, Motion Monitoring, and Bacteria Theranostics for Bioelectronic Wound Dressing

Wounds at joints are difficult to treat and tend to recover more slowly due to the frequent motions. When using traditional hydrogel dressings, they are easy to crack and undergo bacterial infection, difficult to match and monitor the irregular wounds. Integrating multiple functions within a hydrogel dressing to achieve intelligent wound monitoring and healing remains a significant challenge. In this research, a multifunctional hydrogel is developed based on polysaccharide biopolymer, poly(vinyl alcohol), and hydroxylated graphene through dynamic borate ester bonding and supramolecular interaction. The prepared hydrogel not only exhibits rapid self-healing (within 60 s), injectable, conductive and motion monitoring properties, but also realizes in situ bacterial sensing and killing functions. It shows excellent bacterial sensitivity (within 15 min) and killing ability via the changes of electrical signals and photothermal therapy, avoiding the emergence of drug-resistant bacteria. In vivo experiments prove that the hydrogel can promote wound healing effectively. In addition, it displays great electromechanical performance to achieve real-time monitoring and prevent re-tearing of the wound at human joints. The injectable pH-responsive hydrogel with good biocompatibility demonstrates considerable potential as multifunctional bioelectronic dressing for the detection, treatment, management, and healing of infected joint wounds.

Seamless Integration of Conducting Hydrogels in Daily Life: From Preparation to Wearable Application

Conductive hydrogels (CHs) have received significant attention for use in wearable devices because they retain their softness and flexibility while maintaining high conductivity. CHs are well suited for applications in skin-contact electronics and biomedical devices owing to their high biocompatibility and conformality. Although highly conductive hydrogels for smart wearable devices are extensively researched, a detailed summary of the outstanding results of CHs is required for a comprehensive understanding. In this review, the recent progress in the preparation and fabrication of CHs is summarized for smart wearable devices. Improvements in the mechanical, electrical, and functional properties of high-performance wearable devices are also discussed. Furthermore, recent examples of innovative and highly functional devices based on CHs that can be seamlessly integrated into daily lives are reviewed.

Multifunctional MXene/PEDOT:PSS-Based Phase Change Organohydrogels for Electromagnetic Interference Shielding and Medium-Low Temperature Infrared Stealth

Electromagnetic interference (EMI) shielding and infrared stealth technologies are essential for military and civilian applications. However, it remains a significant challenge to integrate various functions efficiently into a material efficiently. Herein, a minimalist strategy to fabricate multifunctional phase change organohydrogels (PCOHs) was proposed, which were fabricated from polyacrylamide (PAM) organohydrogels, MXene/PEDOT:PSS hybrid fillers, and sodium sulfate decahydrate (Na2SO4·10H2O, SSD) via one-step photoinitiation strategies. PCOHs with a high enthalpy value (130.7 J/g) and encapsulation rate (98%) could adjust the temperature by triggering a phase change of SSD, which can hide infrared radiation to achieve medium-low temperature infrared stealth. In addition, the PCOH-based sensor has good strain sensing ability due to the incorporation of MXene/PEDOT:PSS and can precisely monitor human movement. Remarkably, benefiting from the electron conduction of the three-dimensional conductive network and the ion conduction of the hydrogel, the EMI shielding efficiency (k) of PCOHs can reach 99.99% even the filler content as low as 1.8 wt %. Additionally, EMI shielding, infrared stealth, and sensing-integrated PCOHs can be adhered to arbitrary targets due to their excellent flexibility and adaptability. This work offers a promising pathway for fabricating multifunctional phase change materials, which show great application prospects in military and civilian fields.

Synergistic strengthening of PVA ionic conductive hydrogels using aramid nanofibers and tannic acid for mechanically robust, antifreezing, water-retaining and antibacterial flexible sensors

Ion-conductive hydrogels with multi-functionality have gained significant attraction as flexible sensors in various fields such as wearable health monitoring and human motion detection, owing to their high ion conductivity, excellent flexibility and stretchability, and easy availability. In this work, multifunctional ion-conductive hydrogel with excellent mechanical properties, antifreezing properties, water retention and antibacterial performance was fabricated by the freeze-thaw crosslinking between polyvinyl alcohol (PVA) and aramid nanofibers (ANF), and the subsequent solution immersion crosslinking in a mixture of tannic acid (TA) and CaCl2 solution (DMSO/H2O as co-solvent). The rational engineering of a multi-spatial distributed hydrogen bond and Ca2+ coordination bond networks within the hydrogel led to a significant improvement in mechanical properties. Furthermore, through the introduction of TA and binary solvents (DMSO/H2O), the hydrogel had witnessed a substantial enhancement in its antimicrobial properties and water retention capacity. The resultant PAT5/CaCl2-5% (DMSO/H2O) hydrogel exhibited outstanding elongation at break (754.73%), tensile strength (6.25 MPa), electrical conductivity (3.09 S/m), which can be employed in flexible sensors to monitor real-time functional motion for human under diverse conditions. As such, this innovation opens up a novel pathway for envisioning flexible sensor devices, particularly in the realm of human activity monitoring.

Rational Design of Conductive Pathways in Flexible Tactile Sensors via Indirect 3D-Printing of Liquid Metal for High-Precision Monitoring and Recognition

Highly sensitive and conformal sensors are essential for the implementation of human-machine interfaces, health monitoring, and rehabilitation prostheses. The proper adjustment of conductive pathways in the sensing materials is essential for their sensitive transduction of mechanical stimuli into electrical signals. However, the rational, precise, and wide-range control of electrical networks within traditional conductive composites is difficult due to the randomly distributed fillers. Herein, we adopt an indirect 3D-printing method to fabricate pressure sensors with various microchannels for liquid metal (LM) to form consistent and tunable conductive pathways. LM is highly conductive, fluidic, and incompressible at ambient conditions, which guarantees the reliable regulation and function of our pressure sensor. Additive manufacturing provides a facile way to construct complicated microchannels with different lengths, different orientations, cross-sectional sizes, depth-width ratios, and shapes, which can effectively modulate the sensitivity and the sensing range. Under the optimized structural configurations, our sensor achieves a high sensitivity of 1.139 kPa-1, a detection range of 0-68 kPa (loading process), and stability of over 5000 cycles, whose sensing performance is better than most microchannel-filled LM sensors. It can achieve high-accuracy monitoring of pulse, speaking and gestures, and exhibit a full recognition of objects under the assistance of machine learning. This work can provide new ideas on the design of conductive pathways in flexible electronics and expand the application of recyclable LM in human-machine interfaces.

High-Performing Conductive Hydrogels for Wearable Applications

Conductive hydrogels have gained significant attention for their extensive applications in healthcare monitoring, wearable sensors, electronic devices, soft robotics, energy storage, and human-machine interfaces. To address the limitations of conductive hydrogels, researchers are focused on enhancing properties such as sensitivity, mechanical strength, electrical performance at low temperatures, stability, antibacterial properties, and conductivity. Composite materials, including nanoparticles, nanowires, polymers, and ionic liquids, are incorporated to improve the conductivity and mechanical strength. Biocompatibility and biosafety are emphasized for safe integration with biological tissues. Conductive hydrogels exhibit unique properties such as stretchability, self-healing, wet adhesion, anti-freezing, transparency, UV-shielding, and adjustable mechanical properties, making them suitable for specific applications. Researchers aim to develop multifunctional hydrogels with antibacterial characteristics, self-healing capabilities, transparency, UV-shielding, gas-sensing, and strain-sensitivity.

Multifunctional conductive hyaluronic acid hydrogels for wound care and skin regeneration

Although the main function of skin is to act as a protective barrier against external factors, it is indeed an extremely vulnerable tissue. Skincare, regardless of the wound type, requires effective treatments to prevent bacterial infection and local inflammation. The complex biological roles displayed by hyaluronic acid (HA) during the wound healing process have made this multifaceted polysaccharide an alternative biomaterial to prepare wound dressings. Therefore, herein, we present the most advanced research undertaken to engineer conductive and interactive hydrogels based on HA as wound dressings that enhance skin tissue regeneration either through electrical stimulation (ES) or by displaying multifunctional performance. First, we briefly introduce to the reader the effect of ES on promoting wound healing and why HA has become a vogue as a wound healing agent. Then, a selection of systems, chosen according to their multifunctional relevance, is presented. Special care has been taken to highlight those recently reported works (mainly from the last 3 years) with enhanced scalability and biomimicry. By doing that, we have turned a critical eye on the field considering what major challenges must be overcome for these systems to have real commercial, clinical, or other translational impact.

Self-healing, antibacterial, and conductive double network hydrogel for strain sensors

Multifunctional hydrogels have great potential in smart wearable technology, flexible electronic devices, and biomedical research. However, it is highly challenging to prepare unique conductive hydrogels with combined properties such as self-healing, self-adhesive, and antibacterial activity. In this regard, herein, a conductive double network hydrogel (ACBt-PAA/CMCs) was fabricated using carboxymethyl chitosan (CMCs), acrylic acid (AA), and alkaline calcium bentonite (ACBt) via a convenient approach. Owing to the hydrogen bond interaction between PAA and CMCs, the ACBt-PAA/CMCs double network structured hydrogels exhibited excellent self-healing (the tensile strength recovered to 74.3 % after 1 h) and adjustable mechanical properties, in which the fracture stress and strain can be easily adjusted in the range of 0.039 to 0.93 MPa and 564 to 2900 %, respectively. In addition, the ACBt-PAA/CMCs hydrogels exhibited the remarkable antibacterial activities against Escherichia coli (bacterial inhibition efficiency of ~99.99 %) and Staphylococcus aureus (bacterial inhibition efficiency of ~99.98 %). Furthermore, the ACBt-PAA/CMCs hydrogel based wearable skin exhibited an excellent real-time sensing performance for monitoring various motions, signifying outstanding sensing and self-adhesion properties. Considering the unique features such as self-healing, excellent adhesion, highly active strain sensing, and antibacterial activities making the ACBt-PAA/CMCs hydrogel is an excellent multifunctional conductive hydrogel. Hence, we believe that this proposed design method for the fabrication of smart and multifunctional conductive hydrogels, and this ACBt-PAA/CMCs hydrogel could be a promising candidate for flexible wearable materials, health monitoring, and beyond.

High-Performance Zwitterionic Organohydrogel Fiber in Bioelectronics for Monitoring Bioinformation

Bioinformation plays an imperative role in day-to-day life. Wearable bioelectronics are important for sensing bioinformation in real-time and conductive hydrogel fibers are a key component in next generation wearable bioelectronics. However, current conductive hydrogel fibers have remarkable disadvantages such as insufficient conductivity, stability, and bioinformation sensing ability. Here, we report the synthesis of a zwitterionic organohydrogel (ZOH) fiber by the combination of the mold method and solvent replacement strategy. The ZOH fiber shows transparency (92.1%), stretchability (905.8%), long-term stability, anti-freezing ability (-35-60 °C), and low light transmission loss (0.17 dB/cm). Then, we integrate the ZOH fiber into fabric for use as a bioinformation sensor, the results prove its capability as a bioinformation monitor, monitoring information such as motion and bioelectric signals. In addition, the potential of the ZOH fiber in optogenetic applications is also confirmed.

Advances in Biodegradable Electronic Skin: Material Progress and Recent Applications in Sensing, Robotics, and Human-Machine Interfaces

The rapid growth of the electronics industry and proliferation of electronic materials and telecommunications technologies has led to the release of a massive amount of untreated electronic waste (e-waste) into the environment. Consequently, catastrophic environmental damage at the microbiome level and serious human health diseases threaten the natural fate of the planet. Currently, the demand for wearable electronics for applications in personalized medicine, electronic skins (e-skins), and health monitoring is substantial and growing. Therefore, "green" characteristics such as biodegradability, self-healing, and biocompatibility ensure the future application of wearable electronics and e-skins in biomedical engineering and bioanalytical sciences. Leveraging the biodegradability, sustainability, and biocompatibility of natural materials will dramatically influence the fabrication of environmentally friendly e-skins and wearable electronics. Here, the molecular and structural characteristics of biological skins and artificial e-skins are discussed. The focus then turns to the biodegradable materials, including natural and synthetic-polymer-based materials, and their recent applications in the development of biodegradable e-skin in wearable sensors, robotics, and human-machine interfaces (HMIs). Finally, the main challenges and outlook regarding the preparation and application of biodegradable e-skins are critically discussed in a near-future scenario, which is expected to lead to the next generation of biodegradable e-skins.

Self-Healing and Antibacterial Essential Oil-Loaded Mesoporous Silica/Polyacrylate Hybrid Hydrogel for High-Performance Wearable Body-Strain Sensing

Flexible electronics have aroused great interest over the past few years due to their unique advantages of being wearable and lightweight. Introducing the self-healing function into wearable electronics will contribute to the practical applications of wearable electronics by prolonging the devices' lifetime. In this study, a flexible essential oil (EO)-loaded mesoporous silica (EO@AMS)/polyacrylate hybrid hydrogel with superb self-healing and antibacterial properties was prepared. The prepared hybrid hydrogel was found to have excellent piezoresistive sensing performance, which could be particularly suitable for human vital activity monitoring. Benefiting from the strong ionic bonding and multiple hydrogen bonds between polyacrylate and EO@AMS, the hybrid hydrogel could repair its damaged areas with restored sensing and mechanical properties, which suggested excellent self-healing ability. In addition, this hybrid hydrogel, when applied in wearable devices, was found to have high antibacterial ability owing to the slow release of the lemon EO from AMS to kill bacteria. This promising self-healing and antibacterial hybrid hydrogel shows a promising application in wearable electronics for posture monitoring, human-computer interaction, and artificial intelligence.

A review of recent advances in metal ion hydrogels: mechanism, properties and their biological applications

The mechanisms, common properties and biological applications of different types of metal ion hydrogels are summarized.