Fabrication of stretchable PEDOT:PSS coated cotton fabric via LBL electrostatic self-assembly and its UV protection and sensing properties

The development and improvement of fabric-based stretchable strain sensors play a vital role in constructing wearable devices. In this paper, a flexible and sensitive cotton-based strain sensor for human motion monitoring was successfully developed by facile LBL-ESA (layer-by-layer electrostatic self-assembly) of chitosan (or chitosan quaternary ammonium salt) and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), abbreviated to PEDOT:PSS. Chemical structure and microscopic morphology of the cotton fabric coated with PEDOT:PSS were measured using X-ray photoelectron spectroscopy, Raman spectroscopy, Scanning electron micrographs, Fourier transform infrared spectrometer and color strength (K/S value). Electrical conductivity of the fabric changed with the “odd–even” oscillations of K/S value of the cotton fabric. Furthermore, cotton fabric alternately deposited with five cycles reached the highest electrical conductivity (0.335 mS/cm). Meanwhile, the fabric presents excellent UV protection capacity (maximum UPF value of 385.07), which was 24.4 times of pristine cotton fabric (15.76). In addition, cotton fabric strain sensor coated by PEDOT:PSS could effectively detect finger and knee movements of humans, showing a promising prospect in the field of human rehabilitation training, real-time monitoring, and gesture recognition due to its good stability and being highly responsive.