Layer-by-layer assembly of chitosan and carbon nanotube on cotton fabric for strain and temperature sensing

Layer-by-layer (LBL) assembly shows great potential in fabrication of flexible conductive cotton fabrics (FCCF) with carbon nanotubes (CNT) as conductive components but is limited because complicated chemical modification of CNT is usually required. Herein, we reported a facile and eco-friendly LBL approach to fabricating FCCF by dipping in chitosan (CS) aqueous solution and poly(sodium 4-styrenesulfonate) (PSS) wrapped CNT aqueous dispersion alternately. The FCCF with electrical conductivity higher than 30 S/m was achieved when 4 layers of CNT were coated on the cotton fabric (CF). The obtained FCCF possessed outstanding mechanical stability with electrical resistivity almost unchanged after exposure to 500 times mechanical abrasion and 500 circles of tape peeling. The FCCF showed excellent strain sensing performance with high sensitivity (with a gauge factor up to 35.1) and a fast response time (70 ms). It can be used as a strain sensor to accurately detect various human deformations such as finger bending and joint movements. The FCCF could be used as a temperature sensor in that it exhibited stable and reproducible negative temperature sensing behavior in the temperature range of 30–100 °C.