The smart fire alarm fire-resistant wallpaper has an excellent fire-resistant performance, and automatically sends out the alarms (alarm light and alarm sound) to people for taking immediate emergency actions in a fire disaster, and exhibits a low responsive temperature (126.9 degrees centigrade), fast response (in 2 s), and sustained working time in the flame (longer than 5 min). Reprinted from ACS Nano (2018), DOI: 10.1021/acsnano.8b00047.
(a, b) The as-prepared fire-resistant inorganic paper based on ultralong hydroxyapatite nanowires and glass fibers has a high flexibility, and can be folded into complex shapes such as the paper airplane (a) and paper crane (b); (c) the fire-resistant paper sheets can be dyed with different colors; (d–f) various colorful patterns and images can be printed on the fire-resistant paper using a commercial printer. Reprinted from ACS Nano (2018), DOI: 10.1021/acsnano.8b00047.Researchers have fabricated fire-resistant wallpaper based on inorganic nanowires and graphene oxide (GO) thermal sensors that sound an alarm in the event of fire [Chen et al., ACS Nano (2018), https://pubs.acs.org/doi/10.1021/acsnano.8b00047].
The wallpaper is constructed from glass fiber-reinforced hydroxyapatite nanowires and GO thermosensitive sensors. At normal room temperature, the GO sensors are insulating but at elevated temperatures, in the event of a fire in the vicinity, the sensors become conducting and automatically trigger connected sound and light alarms.
“Commercial wallpaper made of plant cellulose fibers is flammable, which promotes the spread of fire,” points out Ying-Jie Zhu of Shanghai Institute of Ceramics, Chinese Academy of Sciences, and the University of Chinese Academy of Sciences. “We believe there is an urgent need to develop fire-resistant and high-safety fire alarm wallpaper.”
The fire-resistant paper is made by simply feeding a solution containing ultralong hydroxyapatite nanowires and glass fibers into a conventional, commercial papermaking machine. Tiny thermo-sensitive sensors are then fabricated onto the backside of the paper using a simple drop casting process with ink containing polydopamine-modified GO. Finally, external copper electrodes are connected to the edges of the thermo-sensitive sensor. The sensors are invisible when the paper is mounted on a wall.
“The ultralong hydroxyapatite nanowires interweave with each other during the fabrication process to form a highly flexible fireresistant inorganic paper,” explains Zhu.
If the local environmental temperature exceeds a certain level, oxygen-containing groups in the GO are driven off and the material becomes highly conducting. The sensors respond rapidly (within a couple of seconds) to temperatures above 126.9 ?C and remain operational for at least 5 min (Fig. 1), enabling a warning alarm to be sounded.
“To the best of our knowledge, this is the first report of smart fireresistant fire alarm wallpaper based on ultralong hydroxyapatite nanowires and GO thermosensitive sensors,” says Zhu. “We believe our smart fire-resistant fire alarm wallpaper, if widely used, could benefit public safety by saving lives and reducing the loss of property in a fire disaster.”
All the materials used in the fire-resistant fire alarm wallpaper are environmentally friendly and can be processed into various textures, or be dyed or printed with designs just like normal cellulose-based wallpaper (Fig. 2). To date, the wallpaper has only been produced in the lab and the cost of hydroxyapatite nanowires would have to drop substantially for the concept to become commercially viable. But the researchers do not foresee any insurmountable technical obstacles ahead.
“We have achieved scaled-up production of ultralong hydroxyapatite nanowires at a level of 100 liters in our laboratory,” says Zhu. “We are now striving to find a low-cost, environmentally friendly large-scale production technology.”
Giulio Malucelli, professor of Materials Science and Technology at the Politecnico di Torino in Italy, agrees that the system would be very interesting for the industrial manufacture of fire alarms if scalability can be realized.
“The system designed is quite novel and maybe the first example of a potential fire alarm wallpaper based on fire-resistant hydroxyapatite ultralong nanowires wrapped around glass fibers,” he comments. “The presence of GO, acting as a thermosensitive sensor, allows the paper to ‘inform’ people about the occurrence of a fire, providing a reasonable time to escape.”
This article was first published in Nano Today 20 (2018) 1-6.