Investigating the Potential of Starch Bioplastic as a Precursor for Laser-Induced Graphene Synthesis: A Sustainable Approach

Laser-induced graphene (LIG) has emerged as a groundbreaking technology for the conversion of carbon-rich precursors into electrically conductive materials, which exploits commercially available IR laser engravers to induce localized pyrolysis on a wide range of materials. While synthetic precursors initially caught the interest of the scientific community, the need for more sustainable options has shifted the focus to their bioderived counterparts. Among these alternatives, starch bioplastic is of particular interest, since it represents half of the commercially available bioplastics, owing to its straightforward production process and satisfying mechanical properties. In light of these considerations, our study aims to explore the potential of starch bioplastic as a promising precursor for LIG.<br/>A case study on a self-crafted starch-based bioplastic was investigated. The bare biopolymer consists of starch powder, acetic acid, deionized water and glycerol. Initial attempts at converting it into LIG were unsuccessful, resulting in mere ablation upon laser scribing. Instead, the addition of up to 5 wt.% of iron nitrate Fe(NO₃)₃9●H₂O allowed to induce the carbonization of the precursor. As shown by thermogravimetric analysis, the iron nitrate indeed improved the thermal stability at elevated temperatures (&gt; 600 °C), a crucial requirement for LIG synthesis. Raman spectroscopy confirmed that the laser-induced carbon material owns the characteristic structural features of LIG (as evidenced by the presence of the typical D, G, 2D bands and the corresponding bands' intensity ratios I_D/I_G ≈ 1 and I_2D/I_G ≈ 0.55). Moreover, the quality of LIG improved with increasing nitrate concentration, ultimately achieving comparable properties to other bioderived and synthetic precursors for LIG. The addition of iron nitrate also had a significant effect on Young's modulus of the bioplastic, modifying it from ≈ 20 MPa to ≈ 1 MPa. The degradability of the precursor was tested in the soil to assess its suitability for transient electronics applications and almost complete degradation was reported after twelve days. The addition of iron nitrate did not show a clear impact on degradability; however, there is evidence that the presence of salt contributes to increased hygroscopicity, which is typically a significant parameter in promoting degradability. These findings demonstrate the validity of our approach and open the path to further analyses and characterization in real-life applications, paving the way for sustainable and efficient methods for patterning conductive tracks.