Inkjet Printing of Reactive Silver Ink on Textiles

Abstract

Inkjet printing of functional inks on textiles to embed passive electronics devices and sensors is a novel approach in the space of wearable electronic textiles. However, achieving functionality such as conductivity by inkjet printing on textiles is challenged by the porosity and surface roughness of textiles. Nanoparticle-based conductive inks frequently cause blockage/clogging of inkjet printer nozzles, making it a less than ideal method for applying these functional materials. It is also very challenging to create a conformal conductive coating and achieve electrically conductive percolation with the inkjet printing of metal nanoparticle inks on rough and porous textile and paper substrates. Herein, a novel reliable and conformal inkjet printing process is demonstrated for printing particle-free reactive silver ink on uncoated polyester textile knit, woven, and nonwoven fabrics. The particle-free functional ink can conformally coat individual fibers to create a conductive network within the textile structure without changing the feel, texture, durability, and mechanical behavior of the textile. It was found that the conductivity and the resolution of the inkjet-printed tracks are directly related with the packing and the tightness of fabric structures and fiber sizes of the fabrics. It is noteworthy that the electrical conductivity of the inkjet-printed conductive coating on pristine polyethylene terephthalate fibers is improved by an order of magnitude by in situ heat-curing of the textile surface during printing as the in situ heat-curing process minimizes the wicking of the ink into the textile structures. A minimum sheet resistance of 0.2 ± 0.025 and 0.9 ± 0.02 Ω/□ on polyester woven and polyester knit fabrics is achieved, respectively. These findings aim to advance E-textile product design through integration of inkjet printing as a low-cost, scalable, and automated manufacturing process.

Kirigami‐Inspired Textile Electronics: K.I.T.E.

“…As seen in the scanning electron microscope (SEM) image in Figure B the loosely packed fiber bundles comprise the yarns of the pristine woven fabric. After inkjet printing, the cured silver forms uniform coatings that do not significantly change the fibers in the yarn structure allowing the textile to maintain characteristic stretchability, breathability, and fabric hand . The false colored 3D optical image (Figure C), 2D optical image (Figure S2, Supporting Information), and the false colored SEM images showing a top down (Figure D) and cross‐sectional view (Figure E) all visually confirm the cured silver after printing.…”

“…The Kirigami patterning process of the inkjet printed e‐textiles is schematically shown in Figure A. Based on Kim et al and Shahariar et al, reactive silver inks were inkjet printed onto pristine woven fabrics consisting of 100% PET fibers in both the warp and weft directions of the textile (Figure A). Most textile structures exhibit anisotropic mechanical behavior due to their respective manufacturing methods.…”

“…These silver coatings show good adhesion to the polyester woven fabrics which results in enhanced wash durability for the printed e‐textiles. Further characterization of adhesion of the silver coatings and the washability of printed polyester woven textiles using reactive silver inks can be found in Shahariar et al's work …”

“…Here, we disclose an unorthodox strategy to enhance the electromechanical environment of printed e‐textile devices by combining both material‐ and design‐ideological approaches, to develop Kirigami‐Inspired Textile Electronics (K.I.T.E.). To leverage the materials approach, our printed e‐textiles use a novel technique to inkjet print reactive silver inks onto textiles . By controlling the processing and curing conditions on polyethylene terephthalate (PET) woven fabrics we achieve uniform conductive coatings that are washable and do not interfere with the textiles innate breathability, comfort, and fabric hand .…”

“…To leverage the materials approach, our printed e‐textiles use a novel technique to inkjet print reactive silver inks onto textiles . By controlling the processing and curing conditions on polyethylene terephthalate (PET) woven fabrics we achieve uniform conductive coatings that are washable and do not interfere with the textiles innate breathability, comfort, and fabric hand . As design‐ideological approaches, we experimentally demonstrate that Kirigami patterning leads to a significantly softer mechanical response by decreasing the woven fabrics elastic modulus by three orders of magnitude, corresponding to a stretchability enhancement of over 800% strain.…”