Laser-induced graphene fibers

In our previous research, we found that the laser induction process on commercially available polyimide sheets is a cost-effective method for the formation of porous graphene that can be subsequently fabricated into mechanically flexible devices. Here we study the parameters required for the formation of varied laser-induced graphene (LIG) morphologies by tuning the laser radiation energy. It was found that a critical fluence point of ∼5 J/cm2 is needed to initiate the carbonization process regardless of the laser power. When increasing the radiation energy, the physical formation of LIG follows a fluid dynamics process in that the morphology of the LIG progressively changes from sheets to fibers and finally to droplets. We then demonstrate that a morphology of LIG nanomaterial, LIG fibers (LIGF), can be generated by this one-step laser photothermolysis process at a radiation energy >40 J/cm2. The LIGF are hollow with a LIG wall and form vertically aligned fibers up to 1 mm in height. Microsupercapacitor (MSC) devices fabricated from LIGF and LIGF-LIG hybrids show 2× the specific areal capacitance over MSCs made entirely from LIG, thereby underscoring the potential for LIGF in flexible device applications.