Polydopamine functionalized stellate mesoporous silica using mussel inspired chemistry for ultrastretchable, conductive and self-healing hydrogel on wearable strain sensors

Conductive hydrogels hold great promise in wearable strain sensor for human motion detection. Nevertheless, the poor mechanical properties, inferior sensitivity and the deficiency of multifunctionalities of conventional hydrogels tremendously constrain their applications. Herein, inspired by mussel chemistry, polydopamine (PDA) and Au nanoparticles (Au NPs) were used to modify stellate mesoporous silica (STMS), which could provide conductivity and multiple non-covalent interactions. The synthesized STMS@PDA-Au NPs were further used to prepare composite polyacrylic acid (PAA) hydrogel (STMS@PDA-Au NPs/PAA) by a one-pot strategy for the application of motion sensors. The resulting hydrogel exhibited satisfactory stretchability (663%), remarkable tensile strength (2.18 MPa), high sensitivity (Gauge Factor = 2.86) and distinguished self-healing properties (90.8%), which are believed to be contributed by the existence of coordination complexations and multiple hydrogen-bonding interactions in the hydrogel network. Additionally, with a rapid dynamic response time (180 ms) and fatigue resistance, this work provides useful insights as a wearable sensor for epidermal sensing applications.