Nanocomposite coatings on cotton and silk fibers for enhanced electrical conductivity

Abstract

Electrically conducting carbon nanofillers like liquid exfoliated graphite (EG), nanographite (NG), carbon nanotube (CNT) and carbon nanofiber (CNF) were dispersed in thermoplastic polyurethane (TPU) matrix. HRTEM images and SAED patterns confirmed exfoliation of graphite and good dispersion of all nanofillers. The polymer dispersions were used to develop nanocomposite coatings on cotton yarn and silk fibers. These nanocomposite coated fibers showed significant improvements in electrical conductivity. Current-voltage (IV) plots indicated linearity for most of the nanocomposite coated fibers. Among the nanofillers, CNF and CNT have strong potential to impart stable conductivity on such fibers. The electrical conductivity of 10 wt% CNF based nanocomposite coated cotton yarn was 2 S/m; while it was more than 12 S/m for silk filament. 2 wt% CNT dispersed nanocomposite coating on silk also showed very good conductivity of 11 S/m. The large void fraction in coated cotton yarn (~12 %) is attributed for such difference in electrical conductivity. Hence, staple yarns are not suitable to develop such nanocomposite coated fibers. Both the resistance and impedance tests were carried out at different test lengths up to 5 cm and resistance and impedance (at 100 Hz, 120 Hz and 1 kHz) per cm was calculated with variable test length. As variations in test results were not very high it can be concluded that the uniformity in electrical conductivity is achieved through these coatings.

Fabrication and Characterization of Conductive Conjugated Polymer‐Coated Antheraea mylitta Silk Fibroin Fibers for Biomedical Applications

“…For example, the electrical conductivity of cotton coated with carbon nanofiber (CNF) is less than 1 S cm −1 . [66] Finally, our work demonstrates the potential for the application of such coated fibers in the biomedical field. We show that the coated fibers retain excellent conductivity properties comparable to those of the corresponding conjugated polymers.…”

“…The bulk conductivities of the coated fibers indicate that coated silk filaments have comparable conductivity to that of the corresponding conjugated polymers and contrast with the low conductivity typically measured for other natural coated fibers. For example, the electrical conductivity of cotton coated with carbon nanofiber (CNF) is less than 1 S cm −1 . Finally, our work demonstrates the potential for the application of such coated fibers in the biomedical field.…”

Electrically Conductive Coatings for Fiber-Based E-Textiles

“…They have also been used to form electrically conductive composites that can be used as flexible sensors [88,97]. Nevertheless, Narayan et al used 5 and 10 wt.% of CNF in a thermoplastic polyurethane (TPU) matrix to form a coating material that was subsequently applied to cotton yarn and silk filaments via dip-coating [98]. Since cotton yarns have a more expanded structure with higher porosity than silk filaments, the coating solution penetrated deeper into the cotton yarns, whereas it remained more on the surface in the case of silk, resulting in an increase in diameter for the latter.…”

Macroscale Biomolecular Electronics and Ionics

“…The reasons for the abundance of studies on silk are mainly due to its attractive mechanical properties (silk fibers are very strong) and its importance in the textile industry—there is a ready supply of natural silks. The common strategy for increasing the conductivity across silk threads is by coating them with organic conducting polymer such as polyethylenedioxythiophene polystyrene (PEDOT:PSS) (see for example Figure b for an image of a coated silk thread), polypyrrole, and polyaniline, or coating with graphene/carbon nanotubes . These coatings have resulted in impressive measured conductivities of up to 10 −1 S cm −1 for the conductive organic polymer coatings and 10 S cm −1 for the graphene coatings .…”