Laser induced 3D porous graphene dots: Bottom-up growth mechanism, multi-physics coupling effect and surface wettability

One-step conversion of three-dimensional (3D) porous laser-induced graphene (LIG) from carbon precursors opens a facile way to prepare graphene-related materials. Herein, a series of dots is fabricated by CO2 laser irradiation of polyimide (PI, Kapton) films to investigate the in-situ growth mechanism of LIG. Complex phase transitions combined with various physical fields lead to morphologic changes from mastoid to volcanic structure. The cross-section profile varying with laser parameters are fitted to measure the physical characteristics (e.g., top/bottom width, depth, and tilt angle) under Gauss energy distribution. With considering the highly localized heating effect and non-uniform thermal stress, a coupled physical field is established to theoretically analyze the temperature, thermal stress and deformation distribution. The micro-scale spatial effects such as nucleation, growth, escape and explosion of bubbles in the air flow field are responsible for the 3D porous structure of LIG. Inspired by the “lotus effect”, a superhydrophobic dot matrix is manufactured with static contact angle of 151.5 ± 1.3° and roll-off angle of 15.7 ± 1.2°, laying a foundation for large-scale production of LIG.