Laser-induced graphene (LIG) is a graphenic material synthesized from a polymeric substrate through point-by-point laser pyrolysis. It is a fast and cost-effective technique, and it is ideal for flexible electronics and energy storage devices, such as supercapacitors. However, the miniaturization of the thicknesses of the devices, which is important for these applications, has still not been fully explored. Therefore, this work presents an optimized set of laser conditions to fabricate high-quality LIG microsupercapacitors (MSC) from 60 µm thick polyimide substrates. This is achieved by correlating their structural morphology, material quality, and electrochemical performance. The fabricated devices show a high capacitance of 22.2 mF/cm² at 0.05 mA/cm², as well as energy and power densities comparable to those of similar devices that are hybridized with pseudocapacitive elements. The performed structural characterization confirms that the LIG material is composed of high-quality multilayer graphene nanoflakes with good structural continuity and an optimal porosity.

To enable the development of artificial intelligence of things, the improvement of the strain sensing mechanisms and optimization of the interconnections are needed. Direct laser writing to obtain laser-induced graphene (LIG) is being studied as a promising technique for producing wearable, lightweight, highly sensitive, and reliable strain sensors. These devices show a higher degree of flexibility and stretchability when transferred to an elastomeric substrate. In this article, we manufactured polydimethylsiloxane (PDMS)-encapsulated LIG piezoresistive strain sensors with a quasi-linear behavior and a gauge factor of 111. The produced LIG was morphologically characterized via Raman spectroscopy and scanning electron microscopy before and after the electromechanical characterization and before and after the LIG transfer to PDMS. The results from these analyses revealed that the integrity of the material after the test was not affected and that the LIG volume in contact with the substrate increased after transfer and encapsulation in PDMS, leading to the improvement of the sensor performance. The sensors' capability for measuring bend angles accurately was demonstrated experimentally, making them useable in a wide range of applications for human body movement monitoring as well as for structural health monitoring. Regarding body monitoring, a PDMS-encapsulated LIG sensor for knee bending angle detection was proposed. This device showed unaffected performance of 1500 cycles under 8% uniaxial deformation and with response times in the range of 1-2 s.

A way to obtain graphene-based materials on a large-scale level is by means of chemical methods for the oxidation of graphite to obtain graphene oxide (GO), in combination with thermal, laser, chemical and electrochemical reduction methods to produce reduced graphene oxide (rGO). Among these methods, thermal and laser-based reduction processes are attractive, due to their fast and low-cost characteristics. In this study, first a modified Hummer’s method was applied to obtain graphite oxide (GrO)/graphene oxide. Subsequently, an electrical furnace, a fusion instrument, a tubular reactor, a heating plate, and a microwave oven were used for the thermal reduction, and UV and CO₂ lasers were used for the photothermal and/or photochemical reduction. The chemical and structural characterizations of the fabricated rGO samples were performed by Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), scanning electron microscope (SEM) and Raman spectroscopy measurements. The analysis and comparison of the results revealed that the strongest feature of the thermal reduction methods is the production of high specific surface area, fundamental for volumetric energy applications such as hydrogen storage, whereas in the case of the laser reduction methods, a highly localized reduction is achieved, ideal for microsupercapacitors in flexible electronics.

There is an urgent need to fulfill future energy demands for micro and nanoelectronics. This work outlines a number of important design features for carbon-based microsupercapacitors, which enhance both their performance and integration potential and are critical for complimentary metal oxide semiconductor (CMOS) compatibility. Based on these design features, we present CMOS-compatible, graphene-based microsupercapacitors that can be integrated at the back end of the line of the integrated circuit fabrication. Electrode materials and their interfaces play a crucial role for the device characteristics. As such, different carbon-based materials are discussed and the importance of careful design of current collector/electrode interfaces is emphasized. Electrode adhesion is an important factor to improve device performance and uniformity. Additionally, doping of the electrodes can greatly improve the energy density of the devices. As microsupercapacitors are engineered for targeted applications, device scaling is critically important, and we present the first steps toward general scaling trends. Last, we outline a potential future integration scheme for a complete microsystem on a chip, containing sensors, logic, power generation, power management, and power storage. Such a system would be self-powering.

This study proposes a simple and cost-effective approach to enhance the performance of supercapacitors based on laser-induced graphene (LIG). The use of two consecutive laser passes using the same CO₂ engraver on polyimide film led to the expansion in the size of the pores, the increase in the graphitization degree, and the densification of the produced material. These changes in the morphology and chemical structure of the LIG impacted positively its electrochemical performance when it was used as an electrode for supercapacitors. The best achieved material displayed the following results: (a) an enhancement of the areal energy density from 0.77 to 2.20 μWh/cm² at 0.05 mA/cm², (b) a reduction of 60% in the equivalent series resistance, (c) high cycling stability with a capacitance retention rate of 91% after 10.000 cycles, (d) high performance stability under mechanical tests at different angles, and (e) green LED illumination under configuration in series.

Indium tin oxide (ITO) is a commonly used material for transparent conductive electrodes (TCE) in optoelectronic applications. On the other hand, graphene has superior electrical conductivity and exceptional mechanical flexibility, which makes it a promising candidate as a TCE material. This work proposes a CVD graphene/ITO hybrid electrode enhanced by doping with silver nanowires (Ag-NWs). The study aims to improve the performance of the electrode by optimizing two key parameters during the fabrication process: the thermal annealing time after the transfer of graphene on ITO and the Ag-NWs doping conditions. The annealing treatment is fundamental to reducing the residues on the surface of graphene and increasing the interface contact between graphene and ITO. The correct coverage and distribution of the dopant on graphene is obtained by controlling the concentration of the Ag-NWs and the spin coating speeds. The results indicate a substantial improvement in the optical and electrical performance of the Ag-NWs/graphene/ITO hybrid electrode. A remarkably low sheet resistance of 42.4 Ω/sq (±2 Ω/sq) has been achieved while maintaining a high optical transmittance of 87.3% (±0.5%).