The authors explain: "After the paper-making process, hydroxyapatite nanowires and glass fibers are assembled into a well-defined multilayered structure spontaneously, which may be explained by the mechanical equilibrium between physical and chemical forces. The nacre-like multilayered structure is regarded as an effective strategy to balance the strength and toughness".
To prepare the thermosensitive sensor, the researchers prepared a graphene oxide ink, which they drop-casted onto the paper. Finally, copper wires are connected to the two edges of the graphene oxide thermosensitive sensor as external electrodes with the help of silver paste and PDMS. At room temperature, the graphene oxide thermosensitive sensor is in a state of electrical insulation; however, it becomes electrically conductive at high temperatures.
After being exposed to flames, the high temperature induces instantaneous deoxygenation of the graphene oxide thermosensitive sensor, leading to the rapid transformation from the electrical insulation state to an electrically conductive one; thus, the alarm lamp and buzzer connected to the thermosensitive sensor are able to send out the alarms immediately.
In addition, polydopamine is used as both a reductant and a capping agent to simultaneously improve the responsive sensitivity and flame retardancy of the graphene oxide thermosensitive sensor.
The polydopamine-modified graphene oxide (PGO) thermosensitive sensor exhibits a low thermal responsive temperature (126.9°C), rapid response time (2 seconds), and long alarm time in the flame (at least 5 minutes).
Other desirable features of this nanotechnology wallpaper reportedly include environmental friendliness, mechanical robustness, and high flexibility.
The smart fire alarm wallpaper reported by the Chinese team can be processed into various shapes, dyed with different colors, and printed with the commercial printer, thus it is promising for applications such as high-safety interior decoration of houses.