LEGO®-inspired assembly strategy for fabricating BN-CNT-BN multilayer Kevlar-based composites as high-performance temperature sensors and fire alarms†

A new generation of artificial intelligence devices is being developed that require miniaturization and higher working power which result in higher heat flux densities, thus presenting a potential fire hazard. Current fire alarm sensors normally utilize electrically conductive materials that are not compatible with the surface insulation required to work in short circuit-triggered fire disasters. Here, we propose a novel concept and fabrication methods to manufacture durable and fast-response fire alarms with an electrically insulative surface layer. We initially separate the sensing and fireproof function of the fire alarm by creating a multilayer structure, where the conductive, thermally sensitive layer is sandwiched by two fireproof layers. The sensor is fabricated via a unique LEGO®-inspired assembly strategy that creates a nanobridge to coat the fireproof layer on the thermally sensitive layer. The sensor exhibits ultrafast response and recovery times of only 113.54 ms and 111.96 ms, respectively, along with great stability and durability over several cycles. Moreover, the surface BN-ANF layer provides protection for the internal thermally sensitive layer, which insulates it from oxygen and suppress the decomposition of the carbon nanotubes, thus enabling the sensor to be applied as a fire alarm. Upon exposure to fire, the sensor exhibits a fast response speed of 3 s and a long duration of over 1200 s. The fireproofing mechanism is also applied to improve the fire safety of a Joule heating film exposed to simulated short-circuit conditions. This new design concept and fabrication strategy improve the fire safety of a composite film and offer new inspiration for developing high-performance flexible sensors.