Inkjet Printing Conductive Materials on Textiles

Abstract

Inkjet printing functional materials on textiles has attracted considerable attention from researchers and industries due to its promising prospects on wearable applications. Inkjet printing is cost saving and provides customisation ability of printing electronic patterns. Textile substrate is flexible, stretchable, comfort to wear and breathable. The advantages from both the printing technique and the substrate material can be displayed when the deposition of the ink in textiles is well studied. Thus, this thesis investigates fundamental interaction of conductive silver ink on textiles, and the effects of printing parameters and textile properties on the printing quality and electrical performance of the products. The complexity of textile substrates leads to three scales of ink textile interaction mechanisms, which are fibres, yarns, and fabrics. Those mechanisms were compared with existing liquid textile interaction theories, and it was found that ink/fibre and ink/yarn interactions correspond with existing theories. Capillarity confines the transport of the ink, low fibre surface energy leads to increased spreading length, small fibre spacing promotes ink columns formation on fibres but limits the ink spreading in yarns. It was also found that the inkjet printed ink transports predominantly within the warp or weft yarns of the fabric and there is little transport of ink between the yarns. Nevertheless, various yarns woven into fabric structures with different densities can result in distinct ink transporting behaviours. X-Ray tomographic reconstruction reveals that the distribution of Ag after inkjet printing and sintering a nanoparticle conducting ink on a woven polyester textile substrate is strongly controlled by the fibre surface properties and fabric architecture. Reduced drop spacing, increased printing layers and textile hydrophobicity through Scotchgard treatment increased the volume and connectivity of inkjet printed silver ink deposition. In the meantime, the sintering per layer technique further increased the volume and connectivity of inkjet printed silver ink on textiles through enhanced ink penetration mechanism perpendicular to the fibre tows. Electrical conductivity is strongly influenced by the fibre architecture in each yarn direction and, in this case, higher fibre density in warp yarns leads to higher electrical conductance values. Conductance within a yarn is shown to depend on Ag concentration via a percolation mechanism and this is confirmed by a simple model relating the volume of the largest interconnected Ag object present to the measured conductance. To improve the printing quality and electrical performance of electronic textiles through altering fabric structures without additional surface treatment, six types of polyester woven structures were compared. It was found that the increased overall capillarity in the fabric could enhance the conductive ink connectivity in textiles and thus improve the electrical performance of electronic textiles, however, on the other hand, creating unwanted ink bleeding on textiles and reducing printing quality of inkjet printed electronic textiles.

Date of Award	31 Dec 2022
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Brian Derby (Supervisor) & Stephen Yeates (Supervisor)