Laser Sintering Direct Ink Write Silver Nanoflake Ink for On-Demand Manufacturing of Electronics in Space

Developing manufacturing methods for flexible electronics will enable and improve the large-scale production of flexible, spatially efficient, and lightweight devices. Laser sintering is a promising postprocessing method to produce consolidated films for flexible electronic devices while reducing power consumption compared to standard thermal sintering. This work further explores laser sintering of direct ink write (nScrypt) printed silver as a continuation of previous studies on nScrypt-printed silver and aerosol jet-printed gold, platinum, and titanium dioxide for manufacturing printed electronics (PEs) on the International Space Station (ISS). Four different laser wavelengths are studied for laser sintering nScrypt silver nanoflake ink on flexible polyimide and rigid glass substrates. The laser systems investigated are continuous wave (CW) 808 nm, CW 445 nm, CW 1064 nm, and pulsed femtosecond (fs) 1040-nm lasers. The laser power and scanning speed are varied to compare the laser systems and optimize laser sintering parameters for the silver ink. The resistivity of the laser-sintered silver NPs is compared to the resistivity of the unsintered silver to demonstrate the effectiveness of laser sintering. An optimal resistivity of
$5.81\times 10^{-8}\,\,\Omega \cdot \text{m}$
is achieved for the nScrypt silver laser sintered using a fs 1040-nm laser.