Biocompatible Parylene-C Laser-Induced Graphene Electrodes for Microsupercapacitor Applications

Abstract

Laser irradiation of polymeric materials has drawn great attention as a fast, simple, and cost-effective method for the formation of porous graphene films that can be subsequently fabricated into low-cost and flexible electronic and energy-storage devices. In this work, we report a systematic study of the formation of laser-induced graphene (LIG) with sheet resistances as low as 9.4 Ω/sq on parylene-C ultrathin membranes under a CO₂ infrared laser. Raman analysis proved the formation of the multilayered graphenic material, with I_D/I_G and I_2D/I_G peak ratios of 0.42 and 0.65, respectively. As a proof of concept, parylene-C LIG was used as the electrode material for the fabrication of ultrathin, solid-state microsupercapacitors (MSCs) via a one-step, scalable, and cost-effective approach, aiming at future flexible and wearable applications. The produced LIG-MSC on parylene-C exhibited good electrochemical behavior, with a specific capacitance of 1.66 mF/cm² and an excellent cycling stability of 96% after 10 000 cycles (0.5 mA/cm²). This work allows one to further extend the knowledge in LIG processes, widening the group of precursor materials as well as promoting future applications. Furthermore, it reinforces the potential of parylene-C as a key material for next-generation biocompatible and flexible electronic devices.

Keywords: biocompatible devices; flexible electronic devices; laser-induced graphene; microsupercapacitors; parylene-C; scalable production methods.

Figure 1

Images and corresponding heatmaps of the matrices formed by CO₂ laser irradiation on parylene-C (A, C) under nitrogen flow and (B, D) in air.

Figure 2

(A) LIG formation as a function of laser power, speed, and defocused distances in air and under nitrogen flow; (B) schematic of the defocused distances studied and corresponding sheet resistances obtained for LIG (C) in air and (D) under nitrogen flow.

Figure 3

SEM cross-sectional micrographs of the parylene-C layer (A) before and (B) after laser irradiation at 4 W @ 10.2 cm/s in air. Top-view SEM micrographs of laser-induced graphene produced under nitrogen flow (C, D, E) and in air (F, G, H, I).

Figure 4

Representative Raman spectra of the optimized LIG samples (A) under nitrogen flow and (B) in air, and (C) the corresponding XPS spectra.

Figure 5

(A) Direct laser-writing process; (B) LIG–MSC electrodes directly written on a parylene-C film; (C) schematics of the LIG–MSC assembly; (D) cyclic voltammetry, (E) charge–discharge curves, (F) capacitance at different current densities, and (G) capacitance retention and Coulombic efficiency at 0.5 mA/cm² for LIG–MSC on parylene-C.