Tough, High Strength, Freezing Resistance, and Ionic Conductive <scp>PVA</scp> / <scp> CaCO ₃ </scp> ‐ <scp> Na ₂ SO ₄ </scp> Hybrid Hydrogels Enhanced With In Situ Formation of <scp> CaCO ₃ </scp> and Salt

ABSTRACT Recently, hydrogels with desirable mechanical properties and multi‐functionality have displayed great potential in the fields of biomedicine, health monitoring, and artificial intelligence. However, it remains a challenge to fabricate multifunctional hydrogels with both sufficient mechanical strength and toughness. In this work, inspired by biomineralization in nature and the Hofmeister effect, CaCO 3 whiskers enhanced PVA (PVA/CaCO 3 ‐Na 2 SO 4 ) hybrid hydrogels with excellent mechanical properties, freezing‐tolerance, high ionic conductivity, and good cyto‐compatibility were successfully developed by in situ CaCO 3 mineralization and subsequent Na 2 SO 4 solution immersion strategies. The CaCO 3 whiskers formed mechanisms, physiochemical properties, mechanical performances, freezing‐tolerance, conductivity, and in vitro cyto‐compatibility of PVA/CaCO 3 ‐Na 2 SO 4 hybrid hydrogels were investigated. The resultant PVA/CaCO 3 ‐Na 2 SO 4 hybrid hydrogels exhibited excellent tensile strength (13.01 ± 1.56 MPa with elongation at break of 306.58% ± 4.70%), compression strength (6.64 ± 0.05 MPa at 80% compressive strain), good freezing‐tolerance at −20°C, high ionic conductivity (4.18 ± 0.04 S/m), and good cyto‐compatibility. Furthermore, the resultant PVA/CaCO 3 ‐Na 2 SO 4 hybrid hydrogels exhibit sensitive and reliable responses to deformations, which demonstrate promising applications in the detection of human motions and human–machine cooperation. Therefore, this work provided a new strategy for the design and development of multi‐functionality hydrogels with tunable mechanical properties.