Aligned Porous and Anisotropic Nanocomposite Hydrogel with High Mechanical Strength and Superior Puncture Resistance by Reactive Freeze-Casting

Abstract

The construction of ultra-stretchable ionic conductive hydrogels with high mechanical strength and puncture resistance is urgently demanded while challenging because of the contradiction of simultaneously achieving high mechanical strength and super stretchability in one hydrogel. Herein, a salting-out bioriented nanocomposite hydrogel (s-BNCH) is prepared through a reactive freeze-casting procedure, during which an aligned porous polymer skeleton is formed due to the volume exclusion of the directionally grown ice crystals, and the pre-embedded montmorillonite nanosheets are simultaneously aligned within the polymer skeleton. The prepared s-BNCH exhibits anisotropic mechanical strength and ionic conductivity, namely, it possesses high mechanical strength (∼10 MPa) and superior fatigue resistance (toughness of 41 MJ m–3) parallel to the oriented direction, while demonstrating ultra-stretchability (>1000%) and strain-sensitive ion migration pathway orthogonal to the oriented direction. The s-BNCH is then demonstrated as an ultra-stretchable ionic conductor for skin-inspired sensors, showing the impressive strain-sensing performance (sensitivity of 2.49 MPa–1) and unique puncture resistance (>50 N). The reactive freeze-casting strategy is thus promising for developing ultra-stretchable and puncture-resistant ionic hydrogels for skin ionotronics against large stretchability and environmental punctures.

An Anisotropic Noncombustible Nanocomposite Based on a Fiberglass–Chitosan 3D Network for Building Insulation

“…The loss modulus ( G ″) of the CS solution was greater than the storage modulus ( G ′), indicating its presence in liquid form. Similarly, the G ″ of the CS/GF 10 solution was greater than G ′, indicating its liquid-like behavior. , Figure S6 depicts the variation in viscosity of the CS solution upon introduction of GF. Following the addition of GF, the viscosity of the CS solution decreased.…”

“…Similarly, the G″ of the CS/GF 10 solution was greater than G′, indicating its liquid-like behavior. 29,30 Figure S6 depicts the variation in viscosity of the CS solution upon introduction of GF. Following the addition of GF, the viscosity of the CS solution decreased.…”

Bimetallic-MOF Tunable Conductive Hydrogels to Unleash High Stretchability and Sensitivity for Highly Responsive Flexible Sensors and Artificial Skin Applications

“…Various types of hydrogels have been discovered to address these issues, including double-network hydrogels, hydrophobic association hydrogels, , ionically cross-linked hydrogels, , and composite hydrogels. , Among these, composite hydrogels stand out due to their exceptional elongation properties, and the incorporation of conductive nanoparticles further enhances their conductivity. In the fabrication of composite hydrogels, it is crucial that the fillers, such as clay, layered double hydroxide, and montmorillonite, exhibit high hydrophilicity. − The primary driving force behind their performance is electrostatic attraction or hydrogen bonding between the hydrogel network and the nanoparticles. However, it is worth noting that these interactions are relatively weak due to the presence of water in the hydrogel network, leading to limited mechanical strength and significant hysteresis in these composite hydrogels.…”

High-Sensitivity Conductive Copolymer Hydrogel for Multifunctional Flexible Wearable Sensors Based on Salting-Out after Freeze-Casting Assisted UV-Curing

“…This process promotes further cross-linking of the hydrogel, which will improve the toughness of the hydrogel and expand the crystalline domain of the amorphous polymer chain segment. 27 However, the majority of documented works use hydrophilic, high-degree polymerization, long-chain polymers directly as raw materials, such as poly(acrylic acid) (PAA), 28 polyacrylamide (PAM), 29 and poly(vinyl alcohol) (PVA); 27 therefore, these methods are limited in terms of polymer selection. Consequently, it is difficult to apply these strategies to copolymers with more functionality because they do not require monomer polymerization operations.…”