Facile fabrication of superhydrophobic, flame-retardant and conductive cotton fabric for human motion detection

The inherent hydrophilicity, flammability and electrical insulation of pristine cotton fabric (CF) severely restrict their applications in many traditional fields including tents, umbrellas and outdoor jackets and some emerging fields such as wearable electronics. Herein, we report a facile approach to fabricate multifunctional CF with superhydrophobicity, flame-retardancy and electrical conductivity via layer-by-layer assembly and spray-coating. Specifically, the pristine CF was alternately covered with branched polyethyleneimine modified halloysite nanotubes (P-HNTs) and phytic acid (PA), followed by a sprayed layer of octadecylamine modified carboxylated carbon nanotube (CNT-ODA)/polydimethylsiloxane (PDMS) hybrid coating. The obtained multifunctional CF exhibited superhydrophobicity with a high water contact angle (WCA) of 162° and excellent surface stability. Owing to the physical barrier roles of the HNT layer, intumescent char layer by the N-P synergy of b-PEI and PA and the CNT/Si–C compounds after the pyrolysis of the outer CNT-ODA/PDMS layer, the SFRC-CF exhibited good thermal stability and outstanding flame-retardant performance. Furthermore, the SFRC-CF based piezoresistive pressure sensor had the advantages of stable resistance signal and good repeatability, and was successfully applied for detecting different human behavior even under wet environment. Our findings conceivably stand out as a new methodology to fabricate multifunctional cotton fabrics for practical applications in the fields of wearable devices and flexible electronics. Graphic abstract