Laser‐induced graphene (LIG) can be obtained by irradiation of a polymer by a laser source. The present work demonstrates that it is possible to obtain this kind of material using an ultraviolet laser instead of the typical infrared source. Using this approach, a fourfold decrease in the penetration depth (5 µm) is achieved, while the spatial resolution is doubled. Electromechanical strain LIG sensors are patterned in polyimide substrates with different thicknesses and their performance to strain, bending, and force inputs is measured. A low‐cost arterial pulse wave monitor is built, exploring the high force sensitivity of the sensors produced on the thinner substrates.

The ability to synthesize laser-induced graphene (LIG) on cellulosic materials such as paper opens the door to a wide range of potential applications, from consumer electronics to biomonitoring. In this work, strain and bending sensors fabricated by irradiation of regular filter paper with a CO2 laser are presented. A systematic study of the influence of the different process parameters on the conversion of cellulose fibers into LIG is undertaken, by analyzing the resulting morphology, structure, conductivity, and surface chemistry. The obtained material is characterized by porous electrically conductive weblike structures with sheet resistances reaching as low as 32 Ω sq–1. The functionality of both strain (gauge factor of ≈42) and bending sensors is demonstrated for different sensing configurations, emphasizing the versatility and potential of this material for low-cost, sustainable, and environmentally friendly mechanical sensing.

The present work reports the synthesis of zinc oxide (ZnO) nanostructures produced either under microwave irradiation using low cost domestic microwave equipment or by conventional heating, both under hydrothermal conditions. X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, room/low temperature photoluminescence, and Raman spectroscopy have been used to investigate the structure, morphology, and optical properties of the produced ZnO nanorods. Identical structures with aspect ratio up to 13 have been achieved for both synthesis routes displaying similar final properties. The hexagonal wurtzite structure has been identified, and a red-orange emission has been detected in the presence of UV irradiation for all the conditions studied. Thermal stability of the as-prepared nanostructures has been evaluated through thermogravimetric measurements revealing an increase of superficial defects. The as-prepared ZnO nanorods were tested as UV sensors on paper substrate, which led to fast response (30 s) and rapid recovery (100 s) times, as well as sensitivity up to 10 indicating that these materials may have a high potential in low cost, disposable UV photodetector applications.

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The present work reports the synthesis of zinc oxide (ZnO) nanoparticles with hexagonal wurtzite structure considering a solvothermal method assisted by microwave radiation and using different solvents: water (H 2 O), 2-ethoxyethanol (ET) and ethylene glycol (EG). The structural characterization of the produced ZnO nanoparticles has been accessed by scanning electron microscopy, X-ray diffraction, room-temperature photoluminescence and Raman spectroscopies. Different morphologies have been obtained with the solvents tested. Both H 2 O and ET resulted in rods with high aspect ratio, while EG leads to flower-like structure. The UV absorption spectra showed peaks with an orange shift for synthesis with H 2 O and ET and blue shift for synthesis with EG. The different synthesized nanostructures were tested for photocatalyst applications, revealing that the ZnO nanoparticles produced with ET degrade faster the molecule used as model dye pollutant, i.e. methylene blue. Graphical AbstractIntroduction

rehabilitation as it provides objective data to aid the decision-making process by the healthcare staff. [1,2] Typically, this evaluation is done using a combination of inertial measurement units, sensorized mats, or force plates, and video inputs. [3-7] However, the use of mats limits the scope of the analysis to specific sessions and areas. While this technique provides the most detailed data available, point-of-care analysis through insoles sensitization has become an alternative. [8-13] The possibility to continuously monitor feet pressure and other gait parameters, offers valuable data not only in orthopedic rehabilitation [1,2,14] or the assessment of deformations such as the flat foot [15] but also to improve athletes' performance [7] and to mitigate diabetic neuropathy complications, [16,17] neurological disorders, [6,18-20] among others. Different pressure transduction mechanisms have been explored successfully for this application such as piezoresistivity, [9,10,21-25] capacitive sensing, [12,26] piezoelectricity, [27] triboelectricity, [28-31] optical line-of-sight sensing, [8] and fiber Bragg gratings. [11,13] To integrate such sensors into insoles, they can be added either as an extra component, printed or directly integrated using a functional material as the insole. Graphenebased materials have proven to be an interesting platform for mechanical sensing. While single-layer graphene is constrained to gauge-factors ≈2 as most bulk piezoresistive materials, [32] reduced graphene oxide (rGO) foams have demonstrated high sensitivity while being a low-cost technology. [33,34] Graphene flakes in the form of inks can also be printed directly onto materials, providing them with electrical conduction and sensing capabilities. [35] Alternatively, laser-induced graphene (LIG) can be directly synthesized on different materials, using the substrate as the carbon source. [36-38] LIG usually arises as a foamy material with electrical characteristics similar to those of good quality rGO, without requiring wet chemical processes involving dangerous chemicals like those used in the production of graphene oxide and its subsequent reduction. With the ability to be patterned in a fast and inexpensive way, LIG has attracted the interest of researchers for its use as active material in different biomedical applications. [38-41] The formation of LIG is carried out by the irradiation of a substrate with a high-power density laser source, leading to the instantaneous carbonization of the precursor material within a protective plasma created by the gaseous Monitorization of gait-related parameters is of the utmost importance to prevent complications in several diseases, ensuring affordable healthcare for the growing amount of chronic, lifestyle-related diseases and also for improving motion performance. Sensorized insoles allow to both pressure data and gait timings to be extracted non-intrusively in a point of care paradigm. Laserinduced graphene (LIG) offers a path to the integration of sensors in different kinds of materia...

ZnO microrods were grown by laser assisted flow deposition technique in order to study their luminescence behaviour in the near band edge spectral region. Transmission electron microscopy analysis put in evidence the high crystallinity degree and microrod’s compositional homogeneity. Photoluminescence revealed a dominant 3.31 eV emission. The correlation between this emission and the presence of surface states was investigated by performing plasma treatments with hydrogen and nitrogen. The significant modifications in photoluminescence spectra after the plasma treatments suggest a connexion between the 3.31 eV luminescence and the surface related electronic levels.

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