High electrical functionalities with maintaining inherent properties of textiles have remained unsolved even though electronic textiles (e-textiles) are crucial platforms to realize wearable electronics. As a post-process technique, printing technologies can reduce production cost and increase manufacturing throughput of e-textiles. This can be achieved by creating versatile patterns, minimizing materials waste and eliminating incorporation of electronic materials in fiber and yarn production. Currently, limitations in printed e-textiles for wearable electronics exist in poorly incorporated coatings with thick layer deposition of high viscosity inks. Low viscosity inks (&lt;25cP) with a uniform distribution of nanomaterials as solutes are the fundamental requirements in the inkjet process. Dynamic light scattering (DLS) and rheometer were used to characterize particle size (&lt;300nm) and viscosity of each ink. We have developed chemical processes in conductive inks, high dielectric constant inks (high-k inks) and semiconducting inks with different strategies in colloidal science and nanomaterials. In order to overcome challenges in heavy-metal nanoparticle inks, particle-free reactive silver inks based on silver carboxylates (Ag+−O2C−R1) and aqueous ammonia ligand (−NH2/−NR2H) are processed in inkjet system to fabricate e-textiles on knit, woven and nonwoven structures. The low sheet resistance of 0.09 Ω/sq was achieved by controlling the number of print passes, an annealing process, and textile structures. The silver layers coated on fibers ranged from 250 nm to 2.5 µm, maintaining the size of interstices and flexibility of fibers. Moreover, high capacitance textiles (~31 pF/cm2) were fabricated through inkjet printing high-k inks formulated by UV curable acrylate monomers and barium titanate nanoparticles. P-type semiconducting layer with high resistance (&gt;1GΩ/sq) was created by deposition of poly(3-hexylthiophene-2,5-diyl) (P3HT) inks for high-performance device applications. The inkjet printed materials on textiles were characterized by Fourier-transform infrared spectroscopy (FTIR), confocal Raman microscopy and X-ray diffraction (XRD) to verify successful deposition of each material on textile substrates. Our study highlights the inkjet process of various electronic inks to fabricate textile-based electrodes, strain sensors, capacitors, pressure sensors and organic thin film transistors (OTFT) in a wearable electronics system.

Inkjet printing electronic materials on textile platforms and processing strategies for wearable electronics

2019 Fall National Meeting

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