Dual-Mechanism-Driven Environmental-Friendly Fast Self-Healing Ionic Hydrogels with Excellent Sensitivity to Strain Responsiveness

Abstract

Ionic hydrogels have important value for applications in bionic skin and flexible sensor fields. However, general ionic hydrogels suffer from inevitable damage and reduction of service life after long-term use. Here, we propose a dualmechanism-driven strategy with a reversible metal coordination bond and dynamic hydrogen bond to construct a novel fast selfhealing ionic hydrogel via a facile "two-step" approach based on environmental-friendly natural resources as raw materials. The dual-mechanism-driven mode endows the hydrogel with excellent self-healing properties (3 h, 95.31%), tensile strength (479.8 kPa), compression strength (5.235 MPa), and fatigue resistance. The hydrogel also showed excellent self-adhesion performance, even underwater, as well as high and stable conductivity (σ = 17.54 mS• cm −1 ). In addition, it has an ion-responsive deformation feature so that the hydrogel can be shaped and restored in different ion solutions. As a sensor on human skin, the high sensitivity (GF = 2.363) enables it to detect and distinguish various human movements and even different letter pronunciations and pulses. These excellent performances lay a solid foundation for its application in bionic skin and flexible sensor fields.

Highly Stretchable, Fast Self-Healing, Self-Adhesive, and Strain-Sensitive Wearable Sensor Based on Ionic Conductive Hydrogels

“…This design resulted in the hydrogel acquiring impressive self-healing characteristics (within 3 h, achieving 95.31% recovery), as well as notable mechanical performances. 25 When employed as a sensor on human skin, it demonstrated the capability to detect and differentiate a range of human movements, including distinct letter pronunciations and pulse variations.…”

“…Lu and co-workers reported an innovative, rapidly self-healing ionic hydrogel sensor through a novel approach that combines a reversible coordination interaction with dynamic hydrogen bonding. This design resulted in the hydrogel acquiring impressive self-healing characteristics (within 3 h, achieving 95.31% recovery), as well as notable mechanical performances . When employed as a sensor on human skin, it demonstrated the capability to detect and differentiate a range of human movements, including distinct letter pronunciations and pulse variations.…”

“…Due to its relatively high sensitivity, the resistive sensing mode is extensively employed in strain sensors, making it one of the most commonly utilized sensing modes . A variety of resistive strain sensors have been introduced specifically for integration into wearable health monitoring devices. − Wang et al introduced an innovative hydrogel for wearable resistive strain sensors using bacterial cellulose nanowhisker, tannic acid (TA), poly­(acrylic acid) (PAA), Fe 3+ , and a mixture of glycerol and water . The incorporation of multiple hydrogen bonds and coordination interactions involving BCW-TA, PAA, and Fe 3+ is attributed to a favorable balance between mechanical characteristics (stress of 203 kPa, elongation at break of 1950%), a self-healing property with an efficiency of 91%, and notably high strain sensitivity (with a maximum Gauge factor of 5.2 within the 1200–1900% strain range).…”

Self-Healing and Degradable Polycaprolactone-Based Polyurethane Elastomer for Flexible Stretchable Strain Sensors

“…Currently, many self-healable strain sensors based on reversible noncovalent bonds (hydrogen 20−23 and metal coordination bonds 24,25 ) and reversible covalent bonds (Diels−Alder, 26−28 disulfide, 29−31 and imine bonds 32,33 ) have been reported, which significantly improved the durability and prolonged the service life of the sensor. For example, Yan et al prepared a heat-and light-responsive supramolecular elastomer consisting of poly(ethylene glycol), polycaprolactone diol (PCL), and 2ureido-4-pyrimidone.…”

“…An optimal strategy for resolving the aforementioned issue is to endow flexible sensors with self-healing properties. Currently, many self-healable strain sensors based on reversible noncovalent bonds (hydrogen − and metal coordination bonds , ) and reversible covalent bonds (Diels–Alder, − disulfide, − and imine bonds , ) have been reported, which significantly improved the durability and prolonged the service life of the sensor. For example, Yan et al.…”