Researchers from Graz University of Technology, University of Florence, Istituto Italiano di Tecnologia and Scuola Superiore Sant'Anna have demonstrated an innovative process that enables certain common dyes - found in standard marker pens - to be converted into laser-induced graphene (LIG).
The study focused on Eosin Y, a widely used xanthene dye, which exhibited excellent stability and structural properties ideal for laser conversion. While most existing LIG production relies on polymer precursors such as polyimide, this research shows that non-polymeric materials like dyes and inks can also serve as effective precursors.
The key factors enabling this transformation are the dye’s aromatic ring structures and its ability to retain at least 20% of its weight when heated to 800°C, preventing complete decomposition before carbonization can occur.
By mixing Eosin Y with acrylic binder, the researchers created a versatile ink that can be applied to various surfaces. After laser scribing, the resulting LIG demonstrated a conductivity of 34 ± 20 S cm-1, comparable to that of polyimide-derived LIG. This approach, which the researchers call “Paint & Scribe,” allows conductive patterns to be directly formed on diverse substrates, expanding the potential for integrating electronics into unconventional materials.
The team’s discovery originated from an accidental observation: certain colors in commercially available markers could be laser-carbonized, while others were merely ablated. Further spectroscopic analysis identified Eosin Y as a particularly effective precursor. While other dyes, such as Eosin B, showed some potential for laser-induced pyrolysis, the study found that not all xanthene-based dyes behaved the same way. The research determined that a combination of optical absorption and thermal stability plays a crucial role in whether a dye can successfully form conductive graphene-like structures.
To optimize the conversion process, the scientists tested different laser power settings and defocus distances. They found that precise tuning of these parameters was necessary to balance carbonization and material loss. When applied as a thin film, the LIG formed from Eosin Y was only a few micrometers thick, which limited its conductivity. However, dispersing the dye in acrylic binder significantly improved the process, allowing for thicker LIG layers with enhanced electrical properties.
To showcase the technique’s potential, the researchers used their ink formulation to coat a ceramic mug. They then used a laser to selectively convert portions of the paint into conductive LIG, forming a resistive temperature sensor directly on the mug’s surface. When hot liquid was poured inside, the sensor’s electrical resistance changed, demonstrating its ability to function as a simple thermal indicator.
Beyond surface patterning, the team also developed a method to create freestanding graphene structures. By dissolving the unconverted acrylic binder in acetone and floating the carbonized LIG on water, they were able to lift and transfer the conductive material onto other substrates. This technique could be particularly useful for integrating LIG onto flexible polymers that might not withstand direct laser processing.
Detailed analysis of the converted material revealed an unexpected byproduct: sodium bromide (NaBr) crystals forming on the LIG surface. These microscopic structures arise from the breakdown of Eosin Y during pyrolysis and were confirmed through energy dispersive X-ray (EDX) and X-ray diffraction (XRD) analysis. While these crystals do not significantly affect conductivity, their presence offers valuable insight into the chemical transformations occurring during laser treatment.
Raman spectroscopy further confirmed the presence of graphene-like structures, showing characteristic peaks for disordered and sp2-bonded carbon. However, the researchers noted that while the resulting material exhibited strong electrical properties, it was not identical to pristine graphene. The LIG produced contained some structural irregularities, a common feature of laser-induced graphene from organic precursors.
This research extends the capabilities of LIG manufacturing by demonstrating that commercially available dyes can serve as carbonizable precursors. While traditional LIG production has focused on solid polymer sheets, this work shows that liquid inks and paints can also be used, enabling new applications in printed and flexible electronics.
The “Paint & Scribe” approach has the potential to simplify electronics prototyping. By using easily applied dye-based coatings, researchers and engineers could create conductive traces and sensors on non-traditional surfaces, from glass and ceramics to flexible polymers. The process could also be adapted for industrial applications, where automated spray or inkjet deposition of precursor materials could allow for scalable manufacturing of graphene-based electronics.
While further refinements are needed to enhance material uniformity and conductivity, this study provides a new perspective on how everyday materials can be repurposed for advanced electronic applications. By leveraging the properties of commercial dyes, this technique could lower the barrier to entry for developing functional carbon-based electronics, making graphene technologies more accessible across multiple fields.