Low-cost graphite coatings from pencil strokes: a review of technological applications in flexible devices

Recent developments in low-cost and customizable electronics have demonstrated the remarkable potential of graphite traces produced from ordinary pencil lines as a sustainable fabrication route for next-generation devices. This review presents a systematic study of the fabrication processes, properties, and applications of pencil-drawn graphite films for electrochemical, strain, and pressure sensors, energy storage devices, photodetectors, and wearable electronics. The intrinsic advantages of this technique include simplicity, low cost, and environmental friendliness. It enables the frictional deposition of graphite flakes directly onto porous surfaces such as paper, textiles, and wood. The resulting films exhibit good electrical conductivity, flexibility, and mechanical adhesion, without requiring high-temperature processing or toxic chemicals. The major focus is on the relationship among drawing parameters, substrate roughness, and the resulting microstructural morphology, which collectively determine device performance. Pencil-drawn electrodes have enabled self-powered wearable systems, supercapacitors, thermoelectric generators, and disposable biosensors. The potential of green electronics is further enhanced by combining renewable substrates with cellulose-based materials and recyclable carbon materials. This review concludes that pencil-on-paper technology not only democratizes device fabrication but also expands its use in educational, research, and industrial settings by offering a convenient method for prototyping and functional demonstration of electronic systems.