2, Yale University, New Haven, Connecticut, United States
Liquid metal based-soft electronics have attracted attention in fields such as soft robotics, biomedical devices and wearable electronics. Methods to pattern liquid metals have been demonstrated using microchannel injection, direct writing, and microcontact printing. The above techniques are limited in scalability for mass manufacturing, resolution, and repeatability. In our previous work, we created liquid metal nanoparticle inks by sonicating bulk liquid metal in ethanol, printed these inks onto various substrates, and used mechanical sintering to coalesce the liquid metal nanoparticles into conductive paths. In this talk, we show that conductive paths are also possible using laser sintering. We characterize laser sintering of liquid metal nanoparticle films and demonstrate that this approach is compatible with soft substrates and smaller, solid-core particles, neither of which is possible using mechanical sintering. We further present the integration of the optimized laser sintering system into the scalable manufacturing of soft electronics. We investigate the laser sintering phenomenon through comparison with focused ion beam ablation and studying the effects of thermal propagation in sintered films. We study the effects of laser fluence, nanoparticle size, film thickness and substrate materials on the resistance of the sintered films. Finally, we demonstrate several representative devices to highlight the electrical stability of the fabricated circuits under flexing and the ease of manufacturing multilayer and intricately patterned circuits.