NIR-induced pH-reversible self-healing monitoring with smartphone by wireless hydrogel sensor

• Published in: Sensors and actuators. B, Chemical Chemical, 2019-10, Vol.297, p.126783, Article 126783
• Main Authors: Robby, Akhmad Irhas, Lee, Gibaek, Park, Sung Young
• Format: Article
• Language: English
• Subjects: Carbon dots; Electroconductive hydrogel; Fluorescence; Hydrogels; Hydrogen bonding; Infrared detectors; Irradiation; Monitoring; Nanoparticles; Near infrared radiation; Polydopamine; Pore size; Porosity; Properties (attributes); Real time; Self healing materials; Self-healing hydrogel; Smartphones; Stability; Wireless sensor; Zwitterionic fluorescent carbon dot
• ISSN: 0925-4005; 1873-3077
• DOI: 10.1016/j.snb.2019.126783

[Display omitted] •Carbon dot-embedded hydrogel exhibited NIR/pH-induced fluorescence on/off system.•NIR-induced 3D hybrid hydrogel showed pH-dependent self-healing property.•The electronic sensor was relied on the NIR/pH-dependent self-healing reversibility.•Hydrogel showed stimuli-responsive volume transition before and after NIR irradiation.•Wireless sensor can be applied to monitor real-time self-healing of hydrogel. Near infrared (NIR)-induced reversible self-healing hydrogel electronics with pH-dependent controllable properties was designed by employing the pH-driven “blooming-bridged” phenomenon between polydopamine (PDA) and the zwitterionic fluorescent carbon dot (ZFCD). This self-healing hydrogel (PDA@ZFCD-PNIPAAm) was synthesized by incorporating an NIR-responsive PDA-loaded zwitterionic fluorescent carbon dot (PDA@ZFCD) into a thermo-responsive PNIPAAm hydrogel, and further combined with wireless device to monitor self-healing and electronic property of hydrogel. The change in PDA@ZFCD-PNIPAAm hydrogel properties depended on the “blooming-bridged” effect of PDA@ZFCD, which controlled the photothermal release and intermolecular hydrogen bonding of PDA under different pH conditions. At the acidic and basic conditions (blooming-bridged state), PDA@ZFCD-PNIPAAm hydrogel displayed a self-healing behavior under NIR irradiation, which did not occur at a neutral pH (bloomless state) owing to different activation of photothermal heat under NIR irradiation with different hydrogel pore size. This hydrogel also demonstrated different thermal and electronic properties in different pH owing to the “bridged” phenomenon of PDA nanoparticles. Moreover, PDA@ZFCD-PNIPAAm hydrogel indicated reversible fluorescence on/off, self-healing, and electronic properties as the pH conditions changed. In addition, the self-healing phenomenon of hydrogel and the change of its electronic property can be easily monitored in a smartphone as a real-time information via wireless sensor. Therefore, this approach offers new insight on the development of self-healing hydrogels with simple, rapid and real-time monitoring on self-healing behavior, which can be used for future applications of hydrogels.