Development of stretchable conductive fabric through different metals coating approach for e-textile applications

Abstract

This study aims to manufacture and characterize various types of conductive (cotton knitted and polyester knitted) fabrics. The fabrics were prepared through the electro-less copper metal coating approach. The effect of copper electroleess plating on different types of fabric structures and on different crossections of yarns was also observed. The main response of prepared fabric was electrical conductivity, EMI shielding and their durability against washing and rubbing. The current research activity has multiple benefits considering extensive comparison with other studies. Previously electroless plating has been performed by different salts and reducing agents' combinations over different fibres. However, there were no study available to metallize the fabric structures having different GSM and different cross section of fibres. Secondly, we have also studied the effect of different fibrous cross-section (round, hollow round, W shape and octolobel) against copper electroless plating. At first, nine-combed cotton knitted fabric samples with different yarn fineness and elastane percentage were selected in order to see effect of these parameters on electrical conductivity and physical properties of samples such as an increase in weight and thickness, impact of washing cycles and abrasion resistance on the electrical conductivity of the fabric sample. The surface morphology of all the knitted cotton fabric samples were also explored before and after the coating method via scanning electron microscope (SEM) and it showed a remarkably uniform deposition of copper on the fabric surface. the energy dispersive spectroscopy (SEM-EDX) was performed to determine the coated material content on the surface of the fabric after the metal coating process. The utility of conductive fabrics was analyzed for electromagnetic shielding ability over frequency range of 30 MHz to 1.5 GHz. The electrical conductivity and amount of metal deposition was found to be higher for the fabric samples having less GSM and higher cotton percentages in their structures. The results revealed that knitted cotton fabric of 5% elastane with the finer yarn count (Ne=40/1) showed lowest resistivity (3.24 Ω.cm) as compared to the other knitted cotton fabric of 10% elastane with a finer count (Ne=40/1) or 5% elastane with coarser (Ne=30/1). The increase in elastane content into fabric structure also influences the fabric stretchability. The objectives of second part of the study were, to carry out research with the best performing three samples obtained from the first part of the study and three single jersey knitted cotton fabric samples were selected. The selected fabric samples with GSM (136, 154 and 176 GSM) out of nine fabric samples were used in this part. These fabric samples provided the lowest value of electrical resistivity coupled with high EMI shielding and more contents of metal particles. Thereafter, the selected samples were pre-treated with laser to enhance the surface roughness, then electroless plating was performed in order to see the impact of roughness on copper deposition. This section of the research work addresses the development and characterization of conductive cotton fabrics treated with lasers in context of copper (Cu) metallization methodologies. The abrasion resistance, thickness, and durability of the laser-treated knitted cotton fabric samples were investigated. Additionally, samples exhibited exceptionally consistent deposition of Cu nanoparticles on the surface of cotton fabric when the surface morphology of the laser-treated surfaces was examined by employing the scanning electron microscope (SEM) both before and after the coating procedure. To assess the elemental analysis on the surface of the treated samples following the electroless metallization process, an energy dispersing spectroscopy (SEM-EDX) examination was performed. This section of the study indicated that fabric samples that had been laser-treated outperformed untreated fabric samples in terms of wear resistance. Abrasion resistance being one of the significant features in electric textile applications, laser-treated samples might thereby be the best options. The third part of the study was the development and characterization of conductive textured and non-textured polyester fabrics with different cross-sections. The electroless copper plating method was selected to impart conductivity on fabric structures. The deposition of copper nanoparticles on textured and non-textured polyester fabrics was characterized by electrical conductivity, electron scanning microscopy (SEM), microscopic morphology, and energy dispersive X-ray spectroscopy (EDX). SEM images revealed a uniform copper nanoparticle coating of a thin film on textured and non-textured polyester fabrics. The properties of conductive textured polyester fabrics were compared in terms of electrical conductivity, wear resistance, thickness and durability with non-textured conductive polyester fabrics. Structural studies showed that the crystalline surface of the textured and non-textured polyester fabric structure is not affected by electroless metallization. Conductivity studies have shown that textured (lowest resistivity 2.18 Ω.cm) and non-textured (lowest resistivity 76.39 Ω.cm) polyester fabrics have good electrical conductivity. When the durability of conductive textured and non-textured polyester fabrics was examined against washing and rubbing fastness, the textured polyester fabrics showed good retention of copper nanoparticles by maintaining their electrical conductivity level after 250 abrasion cycles. Furthermore, resistivity analysis was also carried to study the effect of copper metallization and conductivity against different morphological structures of fibres. It was observed that there are lower values of electrical resistivity for each coated sample. The resistivity was found to be lowest for hollow round coated fibres (either textured or non-textured). The behaviour of metal deposition for hollow round fibers and electrical conductivity was further justified from the SEM analysis. The W shape fibers showed less amount of metal deposition and higher electrical resistivity values as compared to all. The final applications of developed copper plated fabrics are in the field of smart textiles, sensors, stretchable actuators, EMI shielded panels and stretchable electrodes. Keywords: Conductive textiles, Electroless plating, Copper coating, Electromagnetic interference shielding, sensors and actuators, Stretchable conductive fabrics, Smart textiles, metal coatings, textured polyester fabrics, Metal coated, Cross-sectional fiber.