Combustion-Assisted Photonic Sintering of Printed Liquid Metal Nanoparticle Films

Liquid metals are ideally suited for flexible and wearable electronics due to their compatibility with additive manufacturing and high electrical conductivity that is maintained following mechanical perturbation. While printing of eutectic gallium–indium (eGaIn) liquid metal nanoparticles has been demonstrated, previous techniques for activating electrical conductivity in the as-printed insulating eGaIn nanoparticles limit throughput in roll-to-roll manufacturing processes. Here, ultrafast photonic sintering of eGaIn nanoparticles is demonstrated, which is further enhanced through the use of nitrocellulose as a carrier polymer that undergoes optically triggered combustion to produce eGaIn thin films with electrical conductivities exceeding 10⁴ S cm^–1. This combustion-assisted photonic sintering (CAPS) is two orders of magnitude faster than previously demonstrated noncontact sintering techniques. By circumventing the established tradeoff between electrical conductivity and activation speed, CAPS will facilitate the use of eGaIn liquid metal nanoparticles in high-throughput additive manufacturing of flexible and wearable electronics, sensors, and related technologies.