▎ 摘　　要

Malfunctions in printed circuit boards (PCBs) are often caused by damaged copper traces. Printing materials such as metal nanoparticles, conductive polymers, and graphene along with novel printing methods are being actively explored for repairing the conductive connections in PCBs. Because of its high-resolution capability, direct writing of conductive traces gets significant attention, especially with the widespread use of flexible PCBs. Graphene is an ideal material for such applications due to its excellent electrical and mechanical properties. However, there have been limited reports on graphene-based methods for the facile fabrication of conductive traces. A novel method of femtosecond laser direct writing of graphene traces by the photoreduction of graphene oxide (GO) to conductive reduced GO (rGO) for repair and modification of legacy PCBs is reported. A trace-width resolution of 28.4 mu m is achieved over a large patterning area of 100 mm x 100 mm. The rGO thickness is found to be tunable from 0.6 to 4.4 mu m, while the sheet resistance is minimized to 100 omega sq(-1). The system capability is demonstrated by printing conductive traces on top of a flexible substrate to form a closed path for turning on a light-emitting diode, as well as, by repairing a commercial PCB.