Ambient Process Controlled Laser-Induced Graphene with Tunable Wettability and Electrical Performances for Multifunctional Surfaces

This work presents a facile, scalable, and ambient process to engineer the surface wettability and electrical conductivity of laser-induced graphene (LIG) through precise control of laser scanning resolution, quantified by dots per inch (DPI). The proposed DPI-based laser engineering strategy eliminates the need for inert process atmosphere, chemical functionalization, or postprocessing steps, providing a substantially low-cost, versatile, and sustainable route for tailoring LIG properties compared to the conventional methods. By systematically varying the DPI from 50 to 500, the laser energy per unit area (EPUA) is tuned to induce controlled morphological and structural evolution within the graphene framework. This DPI-driven modulation enables a remarkable transition in surface wettability from superhydrophobic (contact angle ≈134 ± 2.2°) to superhydrophilic (≈13.9 ± 2.1°) alongside a significant reduction in sheet resistance from ≈160 ± 2.3 Ω/□ to ≈10 ± 2.8 Ω/□. The optimized LIG demonstrates excellent electrothermal performance as a hydrophilic Joule heater, achieving a rapid heating rate of ≈5.65 °C/s and a recovery rate of ≈2.5 °C/s. Detailed analysis reveals that synergistic effects of surface roughness and oxygen-rich functionalization govern the wettability transition. The proposed method offers a robust platform for next-generation multifunctional surfaces, including low-power wearable electronics, industrial coatings, and microfluidic systems.