One material for many uses: facile construction of hydrogel sensors with strong anti-damage, anti-freezing, and anti-drying properties, cancer-killing ability and biocompatibility

Conductive hydrogels promise great application prospects in future flexible sensor areas. However, great challenges remain in successfully constructing a green hydrogel sensor with efficient synergy from various advantages simultaneously using green starting chemicals via a one-step green procedure. In this work, these challenges were overcome via a superhydrogen-bond network (SHBN) strategy, by which a novel polyvinyl acetate/tannic acid/graphene oxide (PVA/TA/GO) hydrogel was readily constructed and successfully synergized robust mechanical properties (e.g., supporting an 80 kg boy) with strong anti-damage (a hydrogel with a pre-drilled hole was not fractured at 300% strain), anti-freezing (strong mechanical performance, good electrical conductivity, strain sensitivity and stable signal output capacity were retained even at extremely low temperatures when performing real-time tasks) and anti-drying ability (after exposure to air for three months, the hydrogel did not dry out and retained excellent mechanical/anti-freezing performance similar to that of the original hydrogel). The easy construction (one-step freezing) of the hydrogel and its significantly strengthened mechanical properties and excellent anti-freezing/anti-drying ability mainly result from the SHBNs between the hydroxyls on PVA and the hydroxyls on TA/GO/glycerol. Moreover, no toxic/volatile starting chemicals were used in the preparation or discharged into the surrounding environment. More attractively, the hydrogel possesses both cancer-killing ability and biocompatibility. Another impressive facet is that after being assembled into a hydrogel sensor, it can satisfactorily recognize various motion signals. Therefore, the SHBN strategy, which unites diverse outstanding advantages in a single material, opens up a new avenue for designing new high-performance hydrogels for application even in extremely low-temperature or dry environments.