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

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.