Highly Stretchable Nanocomposite Hydrogels with Outstanding Antifatigue Fracture Based on Robust Noncovalent Interactions for Wound Healing

Abstract

Stable mechanical properties under cyclic mechanical loads are critical for the applications of hydrogels in flexible electronics and tissue engineering. However, most existing tough hydrogels still face obvious notch sensitivity and suffer from fatigue fracture under continuous load. Designing hydrogels with multifunctional properties, such as high stretchability, toughness, and excellent antifatigue fracture, through a facile strategy is on demand. In this work, the nanocomposite hydrogels with comprehensive mechanical properties were prepared by one-pot polymerization of acrylamide (AM), isocyanoethyl methacrylate-glutamine (IEM-Gln), and Laponite XLG nanosheets. Owing to the potent hydrogen bonds formed by urea groups in IEM-Gln and hydrogen-bonding interaction between the polymer chain and nanoclays, the presented nanocomposite hydrogels displayed excellent mechanical properties (tensile strength of 160 kPa, stretchability of 2600%, compressive strength of 2.3 MPa, and toughness of 3300 J/m2). It was noteworthy that the hydrogels exhibited excellent notch insensitivity and fatigue fracture resistance, and even after 50 cycles, there was no measurable crack propagation observed. In addition, the introduction of clay nanosheets into the gelation system endowed the composite hydrogels with outstanding hemostatic activity and tissue adhesiveness. The nanocomposite hydrogels could not only reduce the skin tension of the wound tissue by their high tensile properties but also accelerate hemostasis in the first stage of wound healing, both of which led to the fast healing of skin wound in mice.

Ultrafast Fabrication of Lignin-Encapsulated Silica Nanoparticles Reinforced Conductive Hydrogels with High Elasticity and Self-Adhesion for Strain Sensors

“…Flexible wearable sensors have found widespread applications in realizing human movement detection, artificial intelligence, and smart/soft robotics, where the conductive hydrogels have become one of the most promising candidate owing to the unique physiochemical properties that mimic human skin to accurately sense human physiological activity (such as vocal cords vibration, joint and muscle movement). − However, the conventional conductive hydrogels suffer from a complex and time-consuming manufacturing process that usually requires the assistance of external stimuli including long-time UV irradiation, heating, and toxic initiators. − Moreover, the accuracy and stability of sensing may be seriously compromised by the mechanical challenges (such as large stretching, bending, or twisting multiple times) during the daily use of conductive hydrogels. , Over time, the structural integrity of the hydrogels is gradually damaged, which in turn leads to the overall performance deterioration. A number of attempts have been witnessed toward employing different approaches to develop hydrogels with excellent mechanical properties, such as double network (DN) hydrogels, nanocomposite (NC) hydrogels, and topological hydrogels. − However, these tough hydrogels are usually limited to poor self-adhesiveness and thereby can only adhere to substrates with the assistance of external adhesives (e.g., scotch tapes, bandages, or 3 M adhesives) to ensure robust interface connection with underlying substrates, which often leads to high interfacial impedance and low sensitivity as well as stability in the detection of human physiological signals. ,− For example, Hu et al developed a transparent and highly conductive hydrogel through addition of tannic acid-coated hydroxyapatite nanowires (TA@HAP NWs), which was used as a strain sensor to achieve the purpose of human motion detection. Nevertheless, the preparation process of this transparent hydrogel via three freeze–thaw cycles was complicated; meanwhile, the precise detection of the signal was dependent on the fixation via the adhesive tapes, which may invariably lead to interfacial delamination under stretching–releasing cycles and uneasy to peel-off, causing poor contact and difficulty for long-term application.…”

Ultra‐stretchable, self‐healable, and reprocessable ionic conductive hydrogels enabled by dual dynamic networks

“…However, conventional fabrications of these stretchable conductors are complicated and tedious, making them difficult to be manufactured on a large scale 3 . Meanwhile, the stretchability of these stretchable conductors is mainly determined by the tensile limits of elastic polymer matrices, and irreversible damages of rigid conductive components under large strains severely limit their application in adapting to complex deformations for wearable skin‐inspired strain sensors 4 . Therefore, multifunctional stretchable conductors with the integrated features of easy fabrication, structural stability and high stretchability are largely demanded in developing the next‐generation skin‐inspired strain sensors.…”

Injectable and self‐healing hydrogels with tissue adhesiveness and antibacterial activity as wound dressings for infected wound healing

“…In our previous work, we reported a hydrogen bonding reinforced factor, IEM-Gln, and obtained nanocomposite hydrogels with excellent mechanical strength by free-radical copolymerization with acrylamide (AM) with Laponite XLG nanosheets. 26 The presence of urea bond in IEM-Gln enabled the formation of strong hydrogen bonds as stable crosslinking points to promote gelation. However, the water solubility of IEM-Gln was poor, and the homopolymerization did not afford the formation of hydrogel network.…”