Interdigitated and square laser-induced graphene (LIG) electrodes were successfully fabricated by direct laser writing of common natural cork bottle stoppers. The laser graphitization process was performed with a low-cost hobbyist visible laser in a simple, fast, and one-step process under ambient conditions. The formation of LIG material was revealed by extensive characterization using Raman, attenuated total reflection-Fourier transform infrared (ATR-FTIR), and X-ray photoelectron (XPS) spectroscopies. Electron microscopy investigation showed that the formed LIG structure maintained the hierarchical alveolar structure of the pristine cork but displayed increased surface area, disorder, and electrical conductivity, promising for electrochemical applications. Open planar and sandwich supercapacitors, assembled from fabricated electrodes using poly(vinyl alcohol) PVA/H + as an electrolyte, exhibited a maximum areal capacitance of 1.56 mF/cm 2 and 3.77 mF/cm 2 at a current density 0.1 mA/cm 2 , respectively. Upon treatment with boric acid (H 3 BO 3 ), the areal capacitance of the resulting boron-doped LIG devices increased by ca. three times, reaching 4.67 mF/cm 2 and 11.24 mF/cm 2 at 0.1 mA/cm 2 current density for planar and sandwich configurations, respectively. Supercapacitor devices showed excellent stability over time with only a 14% loss after >10 000 charge/discharge cycles. The easy, fast, scalable, and energy-efficient method of fabrication illustrated in this work, combined with the use of natural and abundant materials, opens avenues for future large-scale production of "green" supercapacitor devices.

Laser‐fabrication of graphene from cellulose‐based feedstock materials often requires extensive preprocessing. This work demonstrates laser fabrication of porous, 3D graphene from a new class of marine‐based sustainable materials–chitosan biopolymers. The biopolymer films contain only chitosan, acetic acid, glycerol, and water. Fourier transform infrared spectroscopy studies indicate that the cured chitosan films still retain a significant water content (≈30%), enabling production of flexible films. A simple 3‐step laser fabrication process is presented using low‐cost infrared (CO2, 2.1 W) and visible (405 nm, 0.5 W) hobbyist laser engravers, with measured sheet resistance values as low as 40 ohms sq.−1. Transient electrochemical detection of an inner sphere redox molecule is demonstrated using a graphene‐like carbon working electrode fabricated on a water‐soluble chitosan substrate.