Screen-Printed Liquid-Metal Inks for Multilayer Flexible Electronics

Conductive traces created from liquid-metal nanoparticle inks are screen-printed onto thermoplastic polyurethane substrates for multilayer, flexible applications. We demonstrate that screen printing is a simple and effective process to print commercially available liquid metal inks for rapid and scalable patterning. Sheet resistance measurements of the printed ink are performed for mesh counts of 110 and 230 threads per inch, resulting in averages of $0.233 \Omega/\text{sq}$. and $1.345 \Omega/\text{sq}$., respectively. Printing dimension accuracy for $450 \mu\mathrm{m}$ trace widths resulted in 7.91% deviation while 16.4% deviation was found for $250 \mu \mathrm{m}$ trace gap spacing for linear features. The screen-printing process is used to create a 3-layer flexible LED matrix with 50 unique elements to demonstrate viability of this method for complex circuit designs.