Green Laser-Induced Graphene from Biodegradable Almond Shell Composite for Sensors Application

Recently, the scientific community has been focusing on the creation of devices based on bioderived and biodegradable materials. In particular, the use of biowaste for green electronics applications has an impressive number of advantages, such as low cost, low density, non-toxicity, biocompatibility and biodegradability. In this study, almond shell powder (ASP) was used as the main component to create a composite, in addition to chitosan as a strong and biodegradable matrix, which resulted in a flexible and biodegradable composite, as confirmed by the results of mechanical tests (Young's modulus = 14 MPa) and biodegradability tests in soil: the almond shell composite showed that 60% of the composite's mass was lost in the soil during a 90-day biodegradation test. In addition, the high concentration of lignin in ASP (30.6%) improves the thermal stability of the material, which also makes it an ideal precursor for the creation of laser-induced graphene (LIG).
LIG is a three-dimensional porous and conductive carbon structure, obtained by irradiation with a CO₂ Infrared laser (IR) or Ultraviolet (UV) laser. LIG synthesis and patterning is a cost-effective one-step process that allows avoiding the use of chemicals and the need for long-term use of high temperatures.
Direct and fast laser patterning of LIG on almond shell composite allows to create sensors on the surface of the material, as well as to use the material in electronic textiles and transition electronics, to manufacture various flexible electrical components and devices with the desired geometry.
As a result, the obtained biodegradable material shows high potential for use as flexible, sensors: tests have already been carried out using this material as a humidity sensor to sense moisture in the surrounding environment, and as for creating electrical circuits.