Reinforcement of Cu nanoink sintered film with extended carbon nanofibers for large deformation of printed electronics

Metallic nanoparticle inks (nanoinks) have attracted great interest in the manufacturing of printed flexible electronics. However, sintering pure nanoinks in ambient conditions results in micro-cracks and pores within the sintered film, which deteriorate the mechanical and electrical characteristics of the sintered nanoinks. To alleviate these problems, we demonstrate the use of very long carbon nanofiber (average length 200 μm) to reinforce the sintered nanoink films. In this study, different weight fractions of carbon nanofiber are dispersed into the Cu nanoink to improve the mechanical bending characteristics. Scanning electron micrographs show improved dispersion of oxidized carbon nanofiber in the nanoink compared to the as-received carbon nanofiber. The composite nanoinks are stencil printed on polyethylene terephthalate film and sintered by intense pulsed light using Xe-flash. The electrical measurements show 90%, 65%, and 66% improved electrical conductivity in the composite nanoink film (0.7% of oxidized carbon nanofiber) compared to the pure Cu nanoink under the 7.5 cm, 5.0 cm, and 2.5 cm of bending radii, respectively.