Preparation of Inkjet Printed poly(3,4-ethylene dioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) doped silver nanoparticle (SNP) on Textile

Abstract

Poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) doped with silver nanoparticle (SNP) is promising as electrodes for stimulating blood to prevent pressure ulcers (PU). The electrical conductivity obtained, however is still insufficient for the said purpose and the mechanisms responsible for the increase of conductivity is not fully understood. Therefore, this research focuses on investigating the effect of SNP colloidal suspension as a secondary dopant of the PEDOT:PSS film on its electrical conductivity. The investigation of the mechanism of the PEDOT:PSS doped SNP films for conductivity enhancement was also prioritized. The doped films with SNP colloidal suspension concentrations of 1000, 2000, 3000, 4000, 5000, and 6000 parts per million (ppm) are prepared via-drop-casting, before characterized for morphological study, functional properties, surface roughness and evaluated for electrical conductivity by using a two-point probe resistance meter. The conductivity of PEDOT:PSS doped 5000 ppm of SNP film increased by one order of magnitude from 0.89 mS/cm to 7 mS/cm. The improvement of conductivity is due to the insulated PSS chain removal by the hydrophilic interaction with water in Ag colloids and the interconnection between the conductive PEDOT chain with positively charged Ag. The XRD results proved the crystallinity of the PEDOT:PSS doped SNP film indicating the least resistance path for charge transports through the π-conjugated polymer chain, as evidenced by SEM micrographs. AFM topography demonstrated the phase separation between PEDOT and PSS induced by charge screening of the Ag nanoparticles and reducing the Coulombic attraction between them, and from these findings, their interconnection by chemical structure is proposed. The formulation with optimum content of SNP at 1.5 v/v% of 5000 ppm in 1 v/v% PEDOT:PSS was incorporated with co-solvents of deionized water (DI) and isopropyl alcohol (IPA) into solution and its effects on electrical conductivity were assessed. The conductivity of the ink solution was improved by three orders of magnitude because of the stronger Coulombic attraction and counterbalance of ions between the organic solvents and PEDOT:PSS/SNP. The addition of co-solvents however, reduced the conductivity of film by 26.5% because of weaker hydrogen bonding interaction between the PEDOT:PSS, Ag nanoparticles, DI and IPA evidenced by FTIR and Raman spectroscopy. The optimum ink formulation of PEDOT:PSS/SNP with 10 v/v% DI and 2 v/v% IPA was inkjet printed to the fabric selected by analytic hierarchy process (AHP) method. The printability properties of the formulated nanocomposite ink like viscosity (4.88 mPa.s), density (4.60 g/cm3), and surface tension (43.53 mN/m) met the requirement of the standard inkjet printer and proved to minimize the clogging issue of the printer nozzle after printing on the cotton fabric substrate. The electrical conductivity of the inkjet printed cotton fabric reduced to three orders of magnitude from 0.65 nS/cm to 0.84 µS/cm because of the conductive network of PEDOT:PSS chains and Ag nanoparticles is separated with the insulated cellulosic fibre of the fabric’s yarns. The conductivity value of the inkjet printed PEDOT:PSS/SNP on fabric was sufficient to stimulate the blood for preventing pressure ulcers (PUs) and suitable to be applied on human’s skin as it exhibits high wetting with low surface tension, and susceptible to E. coli bacteria. Overall, this research would hope to provide insight and clarity for the mechanism of conductivity enhancement in PEDOT:PSS doped SNP polymer film, and its potential to be processed as ink prior embedment on textile for serving the Ummah to achieve good health and well-being.