Recent developments in additive manufacturing (AM) process have led us to fabricate many mechanical and electrical components or devices into complex geometries. Within existing AM processes, laser is widely used as an energy source to selectively sinter particles with a powder bed fusion (PBF) process or cure photopolymers with a vat photopolymerization (VPP) process. This study investigated the applicability of the SLS process for silver nanoparticles (Ag NPs)-photopolymer inks to fabricate micro-scale conductive patterns. With Ag NPs-photopolymer inks prepared with different mixture ratios and pasted on a polyethylene terephthalate (PET) substrate, a pulse width modulation (PWM) signal-controlled 405 nm laser was applied to these inks to selectively sinter and cure the Ag NPs and the photopolymer simultaneously. The final conductive patterns were obtained after a rinse in ethanol to remove un-sintered and un-cured regions of the inks. Microstructures, thickness profiles, pattern width, electrical resistance, and resistivity of the fabricated patterns were investigated by varying the PWM duty and the laser exposure time. Effects of different numbers of scan lines in the pattern and nanoparticle mixture ratios were also investigated. The proposed method is cost effective and easy with fast patterning capabilities. It will leverage practical advances in AM industries.

Nanoparticle laser sintering is one of the vital technologies in additive manufacturing. Numerous processes such as freeform surfaces or seamless parts have been proposed for the fabrication of complex components, however, the resolution and quality of the processes do not meet the standard necessary for practical applications. Therefore, selective laser sintering is used to fabricate electrode patterns in high-precision manufacturing field. Despite the various advantages, laser sintering process generates defects on the pattern with one of the major contributing factors being the Marangoni flow. In this study, the laser sintering process was used to determine the relationship between the nanoparticle blending conditions and the microstructure of the fabricated electrode pattern through the control of the nanoparticles density and laser characteristics such as power, pulse duration, and scan speed. As a result, the conditions for Marangoni flow were analyzed in relation to the concentration of the nanoparticle solution and laser irradiation parameters. More severe Marangoni flow was produced with the solution having a low weight percent of nanoparticles, while the width of the pattern was uniform when the pulsed laser was applied using a high peak power to achieve the same total amount of energy.