Tannic Acid–Silver Dual Catalysis Induced Rapid Polymerization of Conductive Hydrogel Sensors with Excellent Stretchability, Self-Adhesion, and Strain-Sensitivity Properties

Abstract

The application of conductive hydrogels in intelligent biomimetic electronics is a hot topic in recent years, but it is still a great challenge to develop the conductive hydrogels through a rapid fabrication process at ambient temperature. In this work, a versatile poly(acrylamide) @cellulose nanocrystal/tannic acid−silver nanocomposite (NC) hydrogel integrated with excellent stretchability, repeatable self-adhesion, high strain sensitivity, and antibacterial property, was synthesized via radical polymerization within 30 s at ambient temperature. Notably, this rapid polymerization was realized through a tannic acid−silver (TA-Ag) mediated dynamic catalysis system that was capable of activating ammonium persulfate and then initiated the free-radical polymerization of the acrylamide monomer. Benefiting from the incorporation of TA-Ag metal ion nanocomplexes and cellulose nanocrystals, which acted as dynamic connecting bridges by hydrogen bonds to efficiently dissipate energy, the obtained NC hydrogels exhibited prominent tensile strain (up to 4000%), flexibility, self-recovery, and antifatigue properties. In addition, the hydrogels showed repeatable adhesiveness to different substrates (e.g., glass, wood, bone, metal, and skin) and significant antibacterial properties, which were merits for the hydrogels to be assembled into a flexible epidermal sensor for long-term human− machine interfacial contact without concerns about the use of external adhesive tapes and bacterial breeding. Moreover, the remarkable conductivity (σ ∼ 5.6 ms cm −1 ) and strain sensitivity (gauge factor = 1.02) allowed the flexible epidermal sensors to monitor various human motions in real time, including huge movement of deformations (e.g., wrist, elbow, neck, shoulder) and subtle motions. It is envisioned that this work would provide a promising strategy for the rapid preparation of conductive hydrogels in the application of flexible electronic skin, biomedical devices, and soft robotics.

Multifunctional Ionic Skin with Sensing, UV‐Filtering, Water‐Retaining, and Anti‐Freezing Capabilities

“…As a result, some ions are lost with water, resulting in an increase in electrical resistance. [ 37 ] Although there is a certain resistance deviation, the resistance curve is always similar, indicating that our hydrogel sensor has high durability in practical applications. Figure displays relative resistance change rate‐ strain curve of TA@HAP NWs‐PVA(EG/W) hydrogel‐based strain sensor under stepped cyclic stretched strain.…”

Triggering Drug Release and Thermal-Disrupting Interface Induced Mitigation of Composite Photothermal Hydrogel Treating Infectious Wounds

“…Its good mechanical properties are characterized by strong stress and flexibility, so it is often possible to construct hydrogels with good properties without chemical modification ( Chen et al, 2018 ; Fang et al, 2019 ). The electrostatic, hydrogen bonding, and hydrophobic interactions of the groups in hydrogel make it have the characteristics of strong viscosity, which can enhance the skin adhesion ability of the hydrogel ( Xue et al, 2019 ; Hao et al, 2020 ). In addition, with the increase of water, the adhesion decreases, making the hydrogel easy to peel off ( Ning et al, 2014 ).…”

Hydrogel Preparation Methods and Biomaterials for Wound Dressing

“…A versatile poly(acrylamide) cellulose nanocrystal/tannic acid–silver nanocomposite (NC) hydrogel integrated with excellent stretchability, repeatable self-adhesion, high strain sensitivity, and antibacterial property, was synthesized via radical polymerization at an ambient temperature. These were merited for the hydrogels to be assembled into a flexible epidermal sensor for long-term human–machine interfacial contact without concerns about the use of external adhesive tapes and bacterial breeding [ 64 ]. In situ, PAM/SA/Ag hydrogels were prepared by using silver ions in the presence of ammonium persulfate to catalyze free radical polymerization.…”