Influence of lasing parameters on the morphology and electrical resistance of polyimide-based laser-induced graphene (LIG)

Laser-induced graphene (LIG) uses a CO₂ infrared laser scriber for transforming specific polymer substrates into porous graphene. This technique is simple, scalable, low-cost, free of chemicals, and produces a 3D graphene for applications across many fields. However, the resulting 3D graphene is highly sensitive to the lasing parameters used in their production. Here, we report the effects of power, raster speed, number of lasing passes (with and without spot overlapping) on the resulting LIG structure, morphology, and sheet resistance, using a polyimide (PI) substrate. We find that the number of lasing passes, laser spot overlapping and brand of PI used had a strong influence on the quality of the LIG, measured in terms of the I_G/I_D and I_2D Raman bands and sheet resistance. Increasing number of passes and overlapping of laser spots led to increased LIG pore sizes, larger graphene scales, and reduced sheet resistance. Furthermore, the over-the-counter desktop CO₂ laser engraving unit used introduced additional restrictions that limited the quality of the LIG produced, particularly due to inconsistent control of the laser scribing speed and a poor thermal management of the laser unit.