A novel biocompatible wearable sensors based on poly (vinyl alcohol)/graphene oxide hydrogel with superior self-adhesion, flexibility and sensitivity

Polymer hydrogels as wearable sensor attract wide attention, while high adhesion to target surface is essential to reduce interface resistance and maximize signal detection sensitivity. Inspired by mussel-adhesive mechanism, we innovatively fabricated biocompatible carboxylated poly (vinyl alcohol) (CPVA)-based hydrogel by preparing graphene oxide-polydopamine (GO-PDA) hybrid as crosslinker through forming multiple covalent/hydrogen bonding. GO-PDA hybrid with brick-and-mortar structure was embedded and homogeneously distributed in PVA matrix, while forming dense network structure with high crosslinking density and small pore size (0.26 μm) contributed to enhancing mechanical strength/toughness of CPVA/GO-PDA hydrogel. Meanwhile, the hydrogel exhibited extremely high adhesiveness with adhesion strength of 201.95 kPa/188.49 kPa/35.06 kPa to metal/rubber/pigskin, respectively. Moreover, the hydrogel presented excellent strain sensitivity with high gauge factor (GF = 10.07) and low response time (120 ms), which steadily and repeatedly distinguished tensile/compression and small/large strain signals. The sensing applications, like subtle muscle deformation, flexible touch keyboard, tactile signals recognition, successfully demonstrated high sensitivity of hydrogel.