Multifunctional hydrogels of polyvinyl alcohol/polydopamine functionalized with carbon nanomaterials as flexible sensors

The demand of multifunctional hydrogels has been significantly increased to develop wearable strain-sensing devices. However, integrating all desired properties into one component is still challenging. To address this, we developed polyvinyl alcohol (PVA)/polydopamine functionalized carbon dots (PDA@CDs) hydrogels for strain sensing application. The CDs were obtained from cucumber peels through a one-pot heat treatment process and characterized by different spectroscopic techniques. The PDA@CDs were synthesized via a pH-induced polymerization process. The addition of PDA@CDs improved the adhesiveness and conductivity of the PVA matrix. An improved mechanical, rheological, and recovery strength was observed in PDA@CDs incorporated hydrogels than the pure PVA hydrogel, demonstrating enhanced interactions among PVA and PDA@CDs. The PDA@CDs added hydrogels demonstrated superior near-infrared (NIR) responsive property, and a rapid enhancement in the temperature (31.3 °C → 123 °C) was observed in the developed hydrogels within 1 min of laser light (808 nm) irradiation at 1.5 W/cm 2 . The developed hydrogels did not exhibit any toxic effects on human dermal fibroblasts (HDFs), suggesting their cytocompatibility. Furthermore, the antibacterial activity of the developed hydrogels was monitored with Escherichia coli. No bacteria colony was found on the surface of developed hydrogels, demonstrating their antibacterial potential. The sensing ability of the developed hydrogels was monitored at different parts of the human body (finger, wrist, and knee joint). These findings indicate that PDA functionalized CDs have effectively improved PVA properties and can be explored for wearable strain sensors. • Fluorescent carbon dots (CDs) were synthesized from waste cucumber peels. • Functionalization of polydopamine (PDA) with CDs (PDA@CDs) was done through the in-situ polymerization process. • Multifunctional hydrogels of polyvinyl alcohol/polydopamine functionalized carbon dots were developed as flexible sensors. • Anhanced mechanical strength, recovery strength, and photo-thermal properties occurred in PVA/PDA@CDs hydrogels. • The hydrogels demonstrated biocompatible, antibacterial, and real-time motion sensing potentials.