Tailored resistance modulation and sensing performance of conductive aramid paper via femtosecond laser direct writing

Aramid paper's exceptional thermal stability and mechanical robustness make it vital for aerospace and electronic packaging, yet its intrinsic insulation impedes its integration into flexible conductive devices. Modulating its surface resistance without exogenous conductive additives remains a prominent materials engineering challenge. This study introduces a maskless, single-step selective carbonization strategy using a 1030 nm femtosecond laser. By optimizing laser power, scanning speed, and repetition frequency, in-situ carbonized layers with customizable conductivities were fabricated. This technique enables precise sheet resistance modulation across a broad spectrum (20 to 10⁴ Ω/sq), seamlessly transitioning the aramid substrate from an insulator to a conductor. Utilizing Raman spectroscopy, SEM, and confocal microscopy, we elucidated the correlation between microstructural evolution, graphitization degree, and electrical performance. Results reveal that the sp²-hybridized carbon content can be directionally tuned via laser parameter matching to meet specific conductivity demands. Furthermore, the generated carbon patterns exhibit remarkable mechanical flexibility and strong interfacial adhesion, proving highly suitable for the direct fabrication of flexible circuits and strain sensors. Ultimately, this approach provides a novel pathway for the exact electrical functionalization of aramid substrates, significantly expanding their utility in smart wearables and flexible electronics.