Recycling of Nanomaterial Ink Waste for Laser Digital Patterning Process

The laser digital patterning (LDP) process, also known as laser direct writing or laser selective patterning, offers a facile route to fabricating flexible/stretchable electronic devices from solution-processed thin films. Despite their various benefits, the deposition and washing steps associated with solution-processed thin films, specifically when using nanoinks such as nanoparticle (NP) ink and complex ink, inevitably produce nanomaterial waste. To address this issue, we propose a rapid and straightforward recycling process to reuse nanomaterial waste in the LDP process. The recycling process was demonstrated by retrieving NiO x NP ink waste generated during spin-coating and washing steps. Various solvents were utilized to retrieve and regenerate the nanoink. Remarkably, a recovery efficiency of over 90% was achieved for the NiO x NP ink even after multiple cycles. Comprehensive characterization was conducted on the recycled NP ink, comparing it with the originally synthesized NP ink using diverse analytical techniques. We also verified that the performance of the Ni electrode-based flexible heater manufactured using the recycled NiO x NP ink is nearly identical to that using the as-synthesized NP ink without any degradation. Additionally, we assessed the recyclability of Cu complex ink to determine which type of nanoink is more advantageous concerning material recycling for the LDP process. Our findings confirm that adopting NP ink presents an effective and sustainable strategy for diminishing nanomaterial waste during the LDP process.