Inkjet Printing of Reactive Silver Ink on Textiles.

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 (E-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 the 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 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 PET fibers is improved by an order of magnitude by in-situ heat curing of the textiles 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 Ω/□ and 0.9 ± 0.02 Ω/□ on polyester woven and polyester knit fabric 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.