Showing papers by "Ignacio R. Matias published in 2022"

Ultrahigh Sensitive Detection of Tau Protein as Alzheimer's Biomarker via Microfluidics and Nanofunctionalized Optical Fiber Sensors

Abstract: Alzheimer's disease (AD) is one of the most common neurodegenerative illnesses displaying the highest death rate in the elderly. However, the existing AD diagnostic system remains elusive due to lack of a technology that may ensure enough sensitivity and reproducibility, detection accuracy, and specificity. Herein, a straightforward approach is reported to realize lab‐on‐fiber (LoF) technology for AD biomarker detection based on a D‐shaped single‐mode fiber combined with nanometer‐scale metal‐oxide film. The proposed sensing system, which permits the generation of lossy‐mode resonance (LMR), remarkably increases the evanescent field of light guided through the fiber, and hence the fiber‐surrounding medium interaction. Moreover, such optical sensors are highly repeatable in results and can safely be embedded into a compact and stable microfluidic system. Herein, the specific detection of Tau protein (as one of the classical AD biomarkers that is highly correlated with AD progression) in a complex biofluid with a detection limit of 10−12 m and over a wide concentration range (10−3–10 μg mL−1) is successfully demonstrated. The proposed LoF biosensor is an appealing solution for rapid, sub‐microliter dose and highly sensitive detection of analytes at low concentrations, hereby having the potential toward early screening and personalized medicine in AD.

Optical fiber thermo-refractometer.

Abstract: This work presents the implementation of a thermo-refractometer, which integrates the measurement of both refractive index and temperature in a single optical fiber structure. To this purpose, a lossy mode resonance (LMR)-based refractometer is obtained by means of the deposition of a titanium dioxide (TiO2) thin film onto a side-polished (D-shaped) single mode fiber. Measurement and subsequent temperature compensation are achieved by means of a fiber Bragg grating (FBG) inscribed in the core of the D-shaped region. The LMR wavelength shift is monitored in transmission while the FBG (FBG peak at 1533 nm) displacement is observed in reflection. The LMR is sensitive to both the surrounding refractive index (SRI), with a sensitivity of 3725.2 nm/RIU in the 1.3324-1.3479 range, and the temperature (- 0.186 nm/°C); while the FBG is only affected by the temperature (32.6 pm/°C in the 25°C - 45°C range). With these values, it is possible to recover the SRI and temperature variations from the wavelength shifts of the LMR and the FBG, constituting a thermo-refractometer, where it is suppressed the effect of the temperature over the refractometer operation, which could cause errors in the fourth or even third decimal of the measured SRI value.

Design and On-Field Validation of an Embedded System for Monitoring Second-Life Electric Vehicle Lithium-Ion Batteries

Abstract: In the last few years, the growing demand for electric vehicles (EVs) in the transportation sector has contributed to the increased use of electric rechargeable batteries. At present, lithium-ion (Li-ion) batteries are the most commonly used in electric vehicles. Although once their storage capacity has dropped to below 80–70% it is no longer possible to use these batteries in EVs, it is feasible to use them in second-life applications as stationary energy storage systems. The purpose of this study is to present an embedded system that allows a Nissan® LEAF Li-ion battery to communicate with an Ingecon® Sun Storage 1Play inverter, for control and monitoring purposes. The prototype was developed using an Arduino® microcontroller and a graphical user interface (GUI) on LabVIEW®. The experimental tests have allowed us to determine the feasibility of using Li-ion battery packs (BPs) coming from the automotive sector with an inverter with no need for a prior disassembly and rebuilding process. Furthermore, this research presents a programming and hardware methodology for the development of the embedded systems focused on second-life electric vehicle Li-ion batteries. One second-life battery pack coming from a Nissan® Leaf and aged under real driving conditions was integrated into a residential microgrid serving as an energy storage system (ESS).

Simultaneous Generation of Surface Plasmon and Lossy Mode Resonances in the Same Planar Platform

Abstract: A planar waveguide consisting of a coverslip for a microscope glass slide was deposited in one of its two faces with two materials: silver and indium tin oxide (ITO). The incidence of light by the edge of the coverslip permitted the generation of both surface plasmon and lossy mode resonances (SPRs and LMRs) in the same transmission spectrum with a single optical source and detector. This proves the ability of this optical platform to be used as a benchmark for comparing different optical phenomena generated by both metal and dielectric materials, which can be used to progress in the assessment of different sensing technologies. Here the SPR and the LMR were compared in terms of sensitivity to refractive index and figure of merit (FoM), at the same time it was demonstrated that both resonances can operate independently when silver and ITO coated regions are surrounded by different refractive index liquids. The results were supported with numerical results that confirm the experimental ones.

Multichannel Refractometer Based on Lossy Mode Resonances

Abstract: In this work a new multiparameter sensor platform based on lossy mode resonances is presented. The structure consists of a soda-lime optical slab waveguide butt-coupled to multimode optical fibers. A variable thickness thin-film is deposited to generate multiple independent resonances on the same waveguide, which can be monitored using a single spectrometer. In order to show the potentiality of the structure, a broad resonance was selectively narrowed by etching sections of the LMR producer thin film. The spectral width is progressively reduced, allowing to selectively isolate independent resonances, which opens the path for multiple LMR generation in the same spectra in a multiparameter sensing platform. The experimental results were corroborated with a theoretical analysis based on the finite difference method (FDM). As a proof of concept, two refractometers on the same waveguide were fabricated and tested using PDMS cells. This platform can be easily miniaturized in order to integrate multiple sensors at low cost, what can be of interest for the development of multi-analyte biosensors probes.

Bloch surface wave resonances generated with dielectric stack of high refractive index contrast deposited on a D-shaped optical fiber for sensing applications

Abstract: A 5-layer stack composed of TiO2 and Al2O3, two materials with a high refractive index contrast, was deposited on a D-shaped fiber to generate Bloch surface wave resonances with an improved figure of merit.

Spectral measurements with hybrid LMR and SAW platform for dual parameter sensing.

Abstract: Lossy mode resonance (LMR)-based optical sensors change their wavelength upon contact with substances or gases. This allows developing applications to detect the refractive index of the surrounding medium and even the thickness of the biolayers deposited on the waveguide. In the same way, when acoustic sensors are in contact with a liquid, it is possible to determine parameters, especially mechanical ones such as shape of the particle or molecule, mass load, elastic constants and viscosity of the liquid. This work reports the development of a system that combines LMR with surface acoustic wave (SAW) technologies to characterize a liquid in terms of its refractive index and viscosity simultaneously. Conveniently prepared glucose solutions are used for sensor calibration. The refractive index of the solutions ranges from 1.33 to 1.41 and its viscosity ranges from 1.005 mPa·s to 9 mPa·s, respectively. A sensitivity of 332 nm per RIU has been achieved with the optical sensor while the acoustic sensor has shown a sensitivity of -1.5 dB/(mPa·s). This new combinational concept could be expanded to the development of more demanding applications such as chemical sensors or biosensors.

Accurate compensation and prediction of thetemperature cross-sensitivity of tilted FBG claddingmode resonances

Abstract: The temperature dependence of core mode resonance has been thoroughly studied in fiber Bragg gratings (FBGs), but it is not the case for cladding mode resonances in multi-resonance gratings such as tilted FBGs (TFBGs). In this work, the temperature sensitivity of ultraviolet written TFBGs in SMF-28 fibers is assessed, demonstrating in the first, to the best of our knowledge, place that a single gauge factor K T = 6.25 ⋅ 10 − 6 ± 0.02 ⋅ 10 − 6 ∘ C − 1 can be employed to characterize the response to temperature of the resonances over the full spectrum in the 10°–50°C range. Then, a simulation model is obtained, enabling to predict TFBG spectra in the 10°–50°C range with high accuracy. This requires a calibration of the core index and dispersion of the TFBG measured in air at 25°C, and determination of the glass refractive index thermo-optic coefficient ( d n / d T = 8.46 ⋅ 10 − 6 ± 0.1 ⋅ 10 − 6 ∘ C − 1 , common to both core and cladding glasses), leading to a mean error on the wavelength position of resonances between 1 and 3 pm. This mean error can be further reduced (less than 1 pm) by considering a linear dependence with temperature of d n / d T . Therefore, this model will enable to completely remove the temperature-induced shifts of all resonances in TFBG sensing applications and measure with great accuracy the variables of interest by using the scaled averages of groups of resonances instead of (less accurate) individual shifts.

Fault Detection of Planetary Gears Based on Signal Space Constellations

Abstract: A new method to process the vibration signal acquired by an accelerometer placed in a planetary gearbox housing is proposed, which is useful to detect potential faults. The method is based on the phenomenological model and consists of the projection of the healthy vibration signals onto an orthonormal basis. Low pass components representation and Gram–Schmidt’s method are conveniently used to obtain such a basis. Thus, the measured signals can be represented by a set of scalars that provide information on the gear state. If these scalars are within a predefined range, then the gear can be diagnosed as correct; in the opposite case, it will require further evaluation. The method is validated using measured vibration signals obtained from a laboratory test bench.

Smart Charging Station with Photovoltaic and Energy Storage for Supplying Electric Buses

Abstract: A Smart Charging Station (SCS) has been installed in the Public University of Navarre, Spain, in the framework of the H2020 Smart City Lighthouse STARDUST project. The SCS consists of a high-power electric bus charging point (300 kW), a 100 kW photovoltaic system, a 84 kWh support energy storage system based on a second-life lithiumion battery, and a monitoring and control system that allows the safe storage and convenient access to operation data. This SCS operates as a Smart Grid, being able to provide the power peaks required by the electric bus charger, reducing and smoothing the power demanded from the distribution grid and increasing the renewable energy self-consumption rate. This contribution presents a novel monitoring and control system, which is a key tool to integrate this SCS in the data infrastructure of a Smart City, as well as an energy management system able to operate the SCS to achieve the above-mentioned technical requirements. The crucial role of the monitoring and control system and the energy management system becomes evident in this work.

Mode Transition During Deposition of Nanoscale ITO Coatings on Tilted Fiber Bragg Gratings

Abstract: The mode transition phenomenon is experimentally demonstrated in tilted fiber Bragg gratings (TFBG) through the deposition of an indium tin oxide (ITO) thin film employing a DC sputtering machine.

Alfalfa quality detection by means of VIS-NIR optical fiber reflection spectroscopy

Abstract: A first approach study for the classification of alfalfa (medicago sativa) quality has been performed by means of VIS-NIR optical fiber reflection spectroscopy. Reflection spectral data has been obtained from alfalfa samples comprising six different qualities. Obtained data has been classified and organized to feed supervised self-learning algorithms. Neural networks have been used in order to differentiate the quality level of the samples. Obtained results permit to validate the proposed approach with 72% of the samples properly classified. In addition, proposed solution was implemented in a low cost automated detection prototype suitable to be used by non-qualified operators. Obtained equipment consist of a first step towards its utilization in quality monitoring and classification of many other products in the agri-food field.

Mode Transitions and Thickness Measurements During Deposition of Nanoscale TiO2 Coatings on Tilted Fiber Bragg Gratings

Abstract: The mode transition is a phenomenon observed in thin film coated long period fiber gratings (LPGs) and single-mode multimode single-mode (SMS) fibers for certain values of the coating thickness and refractive index, resulting in increased sensitivity for sensing applications. It is shown here that mode transitions occur simultaneously for a large number of mode resonances in the transmission spectra of tilted fiber Bragg gratings (TFBG) measured during the deposition of ∼350 nm thick TiO2 coatings by Atomic Layer Deposition (ALD). In TFBGs, the mode transition shows up as an acceleration of the resonance wavelength shift vs thickness, but without fading of the resonance amplitude. Furthermore, the results show that the mode transition for cladding modes with predominantly “TE” polarization at the cladding boundary is significantly sharper than that of predominantly “TM” polarized modes and that it occurs at a smaller coating thickness (<100 nm vs >200 nm). Finally, using a separately determined coating refractive index (2.14, by ellipsometry on witness flats deposited simultaneously) and simulations of the resonance shifts of the TFBG with coating thickness, it is demonstrated that a TFBG connected to a spectral interrogation system can be used to measure the growth of a coating on the surface of the fiber in real time.