In this paper, we present a comparative study of a cost-effective method for the mass fabrication of electrodes to be used in thin-film flexible supercapacitors. This technique is based on the laser-synthesis of graphene-based nanomaterials, specifically, laser-induced graphene and reduced graphene oxide. The synthesis of these materials was performed using two different lasers: a CO2 laser with an infrared wavelength of λ = 10.6 µm and a UV laser (λ = 405 nm). After the optimization of the parameters of both lasers for this purpose, the performance of these materials as bare electrodes for flexible supercapacitors was studied in a comparative way. The experiments showed that the electrodes synthetized with the low-cost UV laser compete well in terms of specific capacitance with those obtained with the CO2 laser, while the best performance is provided by the rGO electrodes fabricated with the CO2 laser. It has also been demonstrated that the degree of reduction achieved with the UV laser for the rGO patterns was not enough to provide a good interaction electrode-electrolyte. Finally, we proved that the specific capacitance achieved with the presented supercapacitors can be improved by modifying the in-planar structure, without compromising their performance, which, together with their compatibility with doping-techniques and surface treatments processes, shows the potential of this technology for the fabrication of future high-performance and inexpensive flexible supercapacitors.

In this work, three promising Additive Manufacturing (AM)/3D-printing technologies, able to realize conductive elements, are adopted in the realization of antennas. The selected techniques are Fused Filament Fabrication (FFF), Aerosol Jet® Printing (AJ®P), and Laser-Induced Graphene (LIG), which have been compared by measuring the performance of an ultrahigh (UHF) radiofrequency identification (RFID) tag, specifically designed, and realized for the scope. Results have also been analyzed against to data obtained by a reference sample realized in Aluminum. The FFF tag has been manufactured by extruding the Electrifi conductive filament over an ABS printed substrate, used also for the AJ®Pmade antenna. Conversely, the LIG tag has been produced by laser-burning a Kapton® polyimide sheet. All the tested technologies, each one with its pros and cons, allowed to realize working prototypes, even if, as expected, with performance lower than the comparison sample. An electroplating process has been also adopted to increase conductivity, with improvements in the FFF prototype. The obtained results are quite satisfactory. Those related to LIG technology do not yet guarantee performance comparable to the other techniques. Nevertheless, the prospect of creating "green" and cost-effective antennas pushes towards further studies, already underway, which include the study of antenna shapes more suitable for the specific technique as well as process optimizations to increase conductivity.

In this work, gas sensors using laser-reduced graphene oxide (LrGO) as sensitive layer have been fabricated and studied. The laser-synthetized material were structurally and electrically characterized by means of Scanning Electron Microscopy (SEM), Raman spectroscopy, X-ray Photoelectron Spectroscopy (XPS) and the four-point contact method. The gas-sensing properties of the samples were studied by their exposition to 10 ppm to 100 ppm of ethanol and 25 ppm to 130 ppm of ammonia. The results show that the devices present an electrical response corresponding to a purely resistive behavior up to 100 kHz. It is also demonstrated that the resistivity of the sensing layer increases as the gas concentration increases; being of 0.0402 ± 0.001 [%/ppm] for the case of ammonia and 0.0140 ± 0.001 [%/ppm] for the case of ethanol. These results outperform existing sensors and establish a better balance in terms of simplicity, sensitivity, linearity and technology sustainability. In summary, this work especially shows the potential of LrGO for low-cost and low-energy gas sensors fabrication.

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