Tough, High Strength, Freezing Resistance, and Ionic Conductive PVA / CaCO 3 ‐ Na 2 SO 4 Hybrid Hydrogels Enhanced With In Situ Formation of CaCO 3 and Salt‐Out Effect for Flexible Sensors

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.