Superhydrophobic and flame-retardant chitosan/ammonium polyphosphate/montmorillonite aerogel-based piezoresistive pressure sensor for human motion detection

Flexible sensors have great application prospects in wearable electronics, electric skin and smart robot. However, the lack of functionalities such as superhydrophobicity and flame retardancy limits the practical applications of the sensors under complex conditions. Herein, a flame-retardant chitosan (CS)/ammonium polyphosphate (APP)/montmorillonite (MMT) aerogel was prepared through freeze-drying method, and then the superhydrophobic and flame-retardant piezoresistive pressure sensor was obtained after coating silver nanowires and spraying silica/PDMS. The sensor demonstrated superhydrophobicity even after 1500 compression cycles. APP and MMT effectively improved the flame retardancy of the aerogel, and the self-extinguishing time was only 1.3 s. The sensor showed real-time electrical response in a wide pressure range and was able to detect not only large-scale limb activities but also small-scale muscle movements. The prepared superhydrophobic and flame-retardant piezoresistive pressure sensor has great potential in wearable electronics, healthcare monitoring and smart robots even under watery or flammable conditions.