Fabrication, Comparison, Optimization, and Applications of Conductive Graphene Patterns Induced via CO₂ and Diode Lasers

Fabrication of conductive patterns for flexible and printed electronic devices is one of the most challenging steps in the whole process. Conductive patterns in electronic devices are used as electrodes, transducers, connecting links, and sometimes, also as the active sensing elements. Since the introduction of laser induced graphene (LIG), it has been explored to print electrodes and connecting patterns for various electronic devices and systems. This work focuses on an in-house developed laser printing system and the comparison of various electrical, chemical, and morphological properties of the resulting LIG patterns using CO₂ and diode lasers. The system parameters including the laser power, relative printing speed, and the printing resolution were explored and optimized to achieve conductive patterns with varying properties suitable for various targeted applications. The fabricated patterns were characterized for their sheet resistance, surface morphology, chemical properties, and physical size and resolution. Continuous conductive patterns with sheet resistance in range of 11.5 Ω/□ to 43 Ω/□ were achieved using CO₂ laser with a minimum achievable pattern width of ~ 180 μm while patterns with sheet resistance in range of 19 Ω/□ to 105 Ω/□ were achieved using diode laser with a minimum pattern width of ~ 190 μm. The chemical and morphological properties of CO₂ laser-based patterns indicate the formation of 2D graphite sheets with high porosity and low O₂ concentration while the diode laser-based patterns have a lower porosity and higher percentage of O₂ indicating burning and formation of oxides. Various applications of both types have also been discussed based on their respective properties.