Open Access
Integración de inteligencia artifical en un sistema embebido para medidas optoeléctricas
(2016) Vicente Gómara, Adrián; Elosúa Aguado, César; Escuela Técnica Superior de Ingenieros Industriales y de Telecomunicación; Telekomunikazio eta Industria Ingeniarien Goi Mailako Eskola Teknikoa
Este proyecto consiste en la implementación de una red neuronal en el sistema embebido PIC 16F877A de la familia Microchip para realizar medidas de absorción óptica y clasificar distintas muestras. Gracias a algoritmo de la red se puede identificar el tipo de muestra que se está analizando a partir de la medición de la absorbancia para tres longitudes de onda (rojo, verde y azul). El sistema en conjunto se ha integrado en una placa de circuito impreso (PCB), simplificando la circuitería y componentes propuestos en un diseño previo. El código se ha programado en C y se ha optimizado para utilizar los recursos de memoria disponibles en el PIC, haciendo un uso eficiente de los mismos. El tiempo de ejecución es lo suficientemente bajo como para poder realizar la medida y clasificación de la muestra en pocos segundos, por lo que se puede considerar un sistema a tiempo real. Los resultados obtenidos animan a la mejora del prototipo desarrollado para su aplicación en la práctica
Open Access
Desarrollo de recubrimientos superhidrofóbicos y anti-hielo sobre materiales metálicos para aplicaciones aeronáuticas
(2024) Vicente Gómara, Adrián; Rodríguez Trías, Rafael; Rivero Fuente, Pedro J.; Ingeniería; Ingeniaritza; Universidad Pública de Navarra / Nafarroako Univertsitate Publikoa
La formación y acumulación de hielo supone un riesgo en la seguridad de los aviones durante todas las fases de vuelo, especialmente cuando la aeronave se encuentre a media-baja altitud y su velocidad sea lenta (despegue-ascenso y aproximación-aterrizaje). Actualmente, la mayoría de las aeronaves poseen sistemas activos de deshielo y/o anti hielo. Sin embargo, las condiciones severas conducirán a que tarde o temprano se produzca hielo en este tipo de sistemas. Por lo que será necesario la combinación de estrategias pasivas y activas para prevenir la formación de hielo y su posterior eliminación. De esta forma, los sistemas pasivos como el desarrollo de recubrimiento hielofóbicos contribuirán a un menor consumo de energía en los activos. En este estudio, se han desarrollado recubrimientos hielofóbicos a través de una estrategia novedosa basada en superficies compuestas por fibras o partículas con polímeros de baja energía superficial. Tanto la distribución de fibras aleatorias como la coalescencia de partículas dan lugar a estructuras multinivel a micro y nanoescala que son propicias para la optimización de superficies superhidrofóbicas. Estas estructuras contribuirán a reducir la mojabilidad de las gotas de agua (α > 150°) y obtener una alta movilidad, claves para prevenir la formación de hielo (anti-hielo). A su vez, estas superficies actuarán como una barrera protectora frente a la corrosión en aleaciones metálicas de uso aeronáutico. Por un lado, reduciendo la interación de la superficie con el agente corrosivo y por el otro lado, encapsulando inhibidores de corrosion en las fibras, como por ejemplo óxidos metálicos (ZnO NPs). No obstante, las condiciones severas provocarán la formación hielo debido a la aparición de microgotas dentro de las cavidades de la estructura rugosa, que originarán la nucleación del hielo. Una vez formado el hielo, las superficies presentarán una alta adhesión al hielo (65 kPa), generado por el anclaje o entrelazamiento de la capa de hielo con las texturas de la superficie y que ocasionarán la delaminación de la superficie debido al fallo cohesivo de las fibras tras varios ciclos del ensayo de adhesión al hielo. Por esta razón, las superficies superhidrofóbicas en la medida en que retrasen o eviten la nucleación del hielo en las cavidades de su estructura, contribuirán a un mejor rendimiento anti-hielo y a una menor adhesión al hielo (mejorando el deshielo). Por ello, con el fin de optimizar el comportamiento hielofóbico, estas superficies fibrosas serán idales para el desarrollo de superficies porosas impregnadas de líquidos deslizantes, conocidas como SLIPS. Para ello, la capa de aire atrapada entre las texturas de la superficie y las gotas de agua, es sustituida por un lubricante a base de líquidos orgánicos y con baja energía superficial. Esta interfaz provocará una alta movilidad de las gotas (α < 10°) y que la nucleación se vea desfavorecida, lo que contribuye al retaso de la congelación y una ultra baja adhesión al hielo (4,5 kPa). Sin embargo, tras varios ciclos sin infusionar, la adhesión al hielo se verá incrementada (30 kPa) ocasionada por la pérdida de la capa lubricante y que a su vez ocasionará delaminaciones del material por la nucleación del hielo en las cavidades. Por esta razón, las propiedades hielofóbicas de estas superficies dependenrán de la capacidad de retener el lubricante, así como una buena afinidad y estabilidad química del lubricante con las fibras. Para la fabricación de las fibras se ha utilizado la técnica de electrospinning, donde se ha aplicado un diseño de experimentos (DoE) con el fin de comprender la relación entre los parámetros de entrada y salida del sistema, así como construir un modelo extrapolable a otros sistemas de polímeros que permita su optimización respecto a la morfología superficial, ángulo de contacto con el agua (WCA) y velocidad de corrosión. Ademas, se ha utilizado la técnica de electrospinning en combinación con otras técnicas (spin coating y electrospraying) para la obtención de superficies con estructuras basadas en coalescencia de partículas y que, además, doten de una buena adherencia al sustrato tras diferentes tratamientos térmicos. Por último, se han obtenido fibras compuestas por nanopartículas de polímeros no electrospineables, dando lugar a fibras de nuevos materiales. Para caracterizar el rendimiento hielofóbico de las superficies desarrolladas, se han utilizado diferentes metodologías, que han permitido analizar la adhesión al hielo, así como la cantidad de hielo acumulado en función de sus condiciones de formación y comparar su rendimiento respecto a diferentes materiales repelentes al hielo, incluyendo soluciones comerciales y tendencias actuales. Para ello, se han reproducido las condiciones reales de formación de hielo en vuelo mediante un túnel de hielo, obteniendo tanto hielo claro como granulado, así como ensayar el fenómeno de runback o hielo secundario. Finalmente, se ha realizado un estudio comparativo de la adhesión al hielo mediante hielo estático fomado en molde, utilizando diferentes intalaciones del ensayo de adhesión y suponiendo un paso hacia la estandarización de las propiedades hielofóbicas de los recubrimientos diseñados a lo largo de esta Tesis.
Open Access
Novel design of superhydrophobic and anticorrosive PTFE and PAA + B - CD composite coating deposited by electrospinning, spin coating and electrospraying techniques
(MDPI, 2022) Vicente Gómara, Adrián; Rivero Fuente, Pedro J.; Urdiroz Urricelqui, Unai; García, Paloma; Mora, Julio; Palomares, F. Javier; Rodríguez Trías, Rafael; Ingeniería; Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2
A superhydrophobic composite coating consisting of polytetrafluoroethylene (PTFE) and poly(acrylic acid)+ β-cyclodextrin (PAA + β-CD) was prepared on an aluminum alloy AA 6061T6 substrate by a three-step process of electrospinnig, spin coating, and electrospraying. The electrospinning technique is used for the fabrication of a polymeric binder layer synthesized from PAA + β-CD. The superhydrophilic characteristic of the electrospun PAA + β-CD layer makes it suitable for the absorption of an aqueous suspension with PTFE particles in a spin-coating process, obtaining a hydrophobic behavior. Then, the electrospraying of a modified PTFE dispersion forms a layer of distributed PTFE particles, in which a strong bonding of the particles with each other and with the PTFE particles fixed in the PAA + β-CD fiber matrix results in a remarkable improvement of the particles adhesion to the substrate by different heat treatments. The experimental results corroborate the important role of obtaining hierarchical micro/nano multilevel structures for the optimization of superhydrophobic surfaces, leading to water contact angles above 170°, very low contact angle of hysteresis (CAH = 2°) and roll-off angle (αroll−off < 5°). In addition, a superior corrosion resistance is obtained, generating a barrier to retain the electrolyte infiltration. This study may provide useful insights for a wide range of applications.
Open Access
Lossy mode resonance sensors based on nanocoated multimode-coreless-multimode fibre
(Elsevier, 2020) Vicente Gómara, Adrián; Santano Rivero, Desiree; Zubiate Orzanco, Pablo; Urrutia Azcona, Aitor; Del Villar, Ignacio; Ruiz Zamarreño, Carlos; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación; Gobierno de Navarra / Nafarroako Gobernua; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa, PJUPNA26
In this work it is proved the ability to obtain lossy mode resonances (LMRs) in the transmission spectrum with multimode-coreless-multimode fibre optic structure coated with tin oxide on the coreless segment. The devices were characterized as a function of the surrounding medium refractive index and sensitivities of 7346.93 nm/RIU and 708.57 nm/RIU were attained for the first and the second LMR respectively. As an application proof of this technology, one of the devices was biofunctionalized and used for detecting goat anti-mouse IgG in concentrations ranging from 1 to 40 mg/L, with a limit of detection of 0.6 mg/L. This proves the ability of this simple structure to be used for biological, chemical or environmental applications.
Open Access
Etched and nanocoated single-mode multimode single-mode (SMS) fibers for detection of wind turbine gearbox oil degradation
(IEEE, 2019) Del Villar, Ignacio; Goñi Carnicero, Jaime; Vicente Gómara, Adrián; Arregui San Martín, Francisco Javier; Matías Maestro, Ignacio; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación; Gobierno de Navarra / Nafarroako Gobernua, 2017/PI044
The application of an etching process in a single-mode multimode single-mode (SMS) fiber allows monitoring the change of refractive index of wind turbine gearbox oil due to temperature and degradation with a limitation at short temperatures, where the transmission and attenuation bands in the optical spectrum fade. The application of a black tin oxide nanocoating solves this issue and allows tuning the refractive index region where the sensitivity is maximum. The SMS was designed for operating at short wavelengths, where the setup is less expensive. The experimental results were contrasted with a theoretical analysis developed with FIMMWAVE, which allowed understanding better the phenomena involved in the experiments.
Open Access
Electrospinning technique as a powerful tool for the design of superhydrophobic surfaces
(IntechOpen, 2020) Rivero Fuente, Pedro J.; Vicente Gómara, Adrián; Rodríguez Trías, Rafael; Ingeniería; Ingeniaritza; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa, PJUPNA1929
The development of surface engineering techniques to tune-up the composition, structure, and function of materials surfaces is a permanent challenge for the scientific community. In this chapter, the electrospinning process is proposed as a versatile technique for the development of highly hydrophobic or even superhydrophobic surfaces. Electrospinning makes possible the fabrication of nanostructured ultrathin fibers, denoted as electrospun nanofibers (ENFs), from a wide range of polymeric materials that can be deposited on any type of surface with arbitrary geometry. In addition, by tuning the deposition parameters (mostly applied voltage, flow rate, and distance between collector/needle) in combination with the chemical structure of the polymeric precursor (functional groups with hydrophobic behavior) and its resultant viscosity, it is possible to obtain nanofibers with highly porous surface. As a result, functionalized surfaces with water-repellent behavior can be implemented in a wide variety of industrial applications such as in corrosion resistance, high efficient water-oil separation, surgical meshes in biomedical applications, or even in energy systems for long-term efficiency of dye-sensitized solar cells, among others.
Open Access
Setting a comprehensive strategy to face the runback icing phenomena
(Elsevier, 2023) Mora, Julio; García, Paloma; Carreño, Francisco; González, Miguel; Gutiérrez, Marcos; Montes, Laura; Rico, Victor J.; López-Santos, Carmen; Vicente Gómara, Adrián; Rivero Fuente, Pedro J.; Rodríguez Trías, Rafael; Larumbe Abuin, Silvia; Acosta, Carolina; Ibáñez-Ibáñez, Pablo; Corozzi, Alessandro.; Raimondo, Mariarosa; Kozera, Rafal; Przybyszewski, Bartlomiej; González-Elipe, Agustín R.; Borrás, Ana; Redondo, Francisco; Agüero, Alina; Ingeniería; Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2
The development of anti-icing robust surfaces is a hot topic nowadays and particularly crucial in the aeronautics or wind energy sectors as ice accretion can compromise safety and power generation efficiency. However, the current performance of most anti-icing strategies has been proven insufficient for such demanding applications, particularly in large unprotected zones, which located downstream from thermally protected areas, may undergo secondary icing. Herein, a new testing methodology is proposed to evaluate accretion mechanisms and secondary icing phenomena through, respectively, direct impact and running-wet processes and systematically applied to anti-icing materials including commercial solutions and the latest trends in the state-of-the-art. Five categories of materials (hard, elastomeric, polymeric matrix, SLIPS and superhydrophobic) with up to fifteen formulations have been tested. This Round-Robin approach provides a deeper understanding of anti-icing mechanisms revealing the strengths and weaknesses of each material. The conclusion is that there is no single passive solution for anti-ice protection. Thus, to effectively protect a given real component, different tailored materials fitted for each particular zone of the system are required. For this selection, shape analysis of such a component and the impact characteristics of water droplets under real conditions are needed as schematically illustrated for aeronautic turbines.
Open Access
Icephobic coating based on novel SLIPS made of infused PTFE fibers for aerospace application
(MDPI, 2024) Vicente Gómara, Adrián; Rivero Fuente, Pedro J.; Rehfeld, Nadine; Stake, Andreas; García, Paloma; Carreño, Francisco; Mora, Julio; Rodríguez Trías, Rafael; Ingeniería; Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa, PJUPNA1929
The development of slippery surfaces has been widely investigated due to their excellent icephobic properties. A distinct kind of an ice-repellent structure known as a slippery liquid-infused porous surface (SLIPS) has recently drawn attention due to its simplicity and efficacy as a passive ice-protection method. These surfaces are well known for exhibiting very low ice adhesion values (τice < 20 kPa). In this study, pure Polytetrafluoroethylene (PTFE) fibers were fabricated using the electrospinning process to produce superhydrophobic (SHS) porous coatings on samples of the aeronautical alloy AA6061-T6. Due to the high fluorine–carbon bond strength, PTFE shows high resistance and chemical inertness to almost all corrosive reagents as well as extreme hydrophobicity and high thermal stability. However, these unique properties make PTFE difficult to process. For this reason, to develop PTFE fibers, the electrospinning technique has been used by an PTFE nanoparticles (nP PTFE) dispersion with addition of a very small amount of polyethylene oxide (PEO) followed with a sintering process (380 °C for 10 min) to melt the nP PTFE together and form uniform fibers. Once the porous matrix of PTFE fibers is attached, lubricating oil is added into the micro/nanoscale structure in the SHS in place of air to create a SLIPS. The experimental results show a high-water contact angle (WCA) ≈ 150° and low roll-off angle (αroll-off) ≈ 22° for SHS porous coating and a decrease in the WCA ≈ 100° and a very low αroll-off ≈ 15° for SLIPS coating. On one hand, ice adhesion centrifuge tests were conducted for two types of icing conditions (glaze and rime) accreted in an ice wind tunnel (IWT), as well as static ice at different ice adhesion centrifuge test facilities in order to compare the results for SHS, SLIPs and reference materials. This is considered a preliminary step in standardization efforts where similar performance are obtained. On the other hand, the ice adhesion results show 65 kPa in the case of SHS and 4.2 kPa of SLIPS for static ice and <10 kPa for rime and glace ice. These results imply a significant improvement in this type of coatings due to the combined effect of fibers PTFE and silicon oil lubricant.
Open Access
Comparative study of electrospun polydimethylsiloxane fibers as a substitute for fluorine-based polymeric coatings for hydrophobic and icephobic applications
(MDPI, 2024-11-30) Vicente Gómara, Adrián; Rivero Fuente, Pedro J.; Santos, Cleis; Rehfeld, Nadine; Rodríguez Trías, Rafael; Ingeniería; Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2; Universidad Pública de Navarra / Nafarroako Univertsitate Publikoa, PJUPNA1929
The development of superhydrophobic, waterproof, and breathable membranes, as well as icephobic surfaces, has attracted growing interest. Fluorinated polymers like PTFE or PVDF are highly effective, and previous research by the authors has shown that combining these polymers with electrospinning-induced roughness enhances their hydro- and ice-phobicity. The infusion of these electrospun mats with lubricant oil further improves their icephobic properties, achieving a slippery liquid-infused porous surface (SLIPS). However, their environmental impact has motivated the search for fluorine-free alternatives. This study explores polydimethylsiloxane (PDMS) as an ideal candidate because of its intrinsic properties, such as low surface energy and high flexibility, even at very low temperatures. While some published results have considered this polymer for icephobic applications, in this work, the electrospinning technique has been used for the first time for the fabrication of 95% pure PDMS fibers to obtain hydrophobic porous coatings as well as breathable and waterproof membranes. Moreover, the properties of PDMS made it difficult to process, but these limitations were overcome by adding a very small amount of polyethylene oxide (PEO) followed by a heat treatment process that provides a mat of uniform fibers. The experimental results for the PDMS porous coating confirm a hydrophobic behavior with a water contact angle (WCA) ≈ 118° and roll-off angle (αroll-off) ≈ 55°. In addition, the permeability properties of the fibrous PDMS membrane show a high transmission rate (WVD) ≈ 51.58 g∙m−2∙d−1, providing breathability and waterproofing. Finally, an ice adhesion centrifuge test showed a low ice adhesion value of 46 kPa. These results highlight the potential of PDMS for effective icephobic and waterproof applications.
Open Access
Icephobic and anticorrosion coatings deposited by electrospinning on aluminum alloys for aerospace applications
(MDPI, 2021) Vicente Gómara, Adrián; Rivero Fuente, Pedro J.; García, Paloma; Mora, Julio; Carreño, Francisco; Rodríguez Trías, Rafael; Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2; Ingeniería
Anti-icing or passive strategies have undergone a remarkable growth in importance as a complement for the de-icing approaches or active methods. As a result, many efforts for developing icephobic surfaces have been mostly dedicated to apply superhydrophobic coatings. Recently, a different type of ice-repellent structure based on slippery liquid-infused porous surfaces (SLIPS) has attracted increasing attention for being a simple and effective passive ice protection in a wide range of application areas, especially for the prevention of ice formation on aircrafts. In this work, the electrospinning technique has been used for the deposition of PVDF-HFP coatings on samples of the aeronautical alloy AA7075 by using a thickness control system based on the identification of the proper combination of process parameters such as the flow rate and applied voltage. In addition, the influence of the experimental conditions on the nanofiber properties is evaluated in terms of surface morphology, wettability, corrosion resistance, and optical transmittance. The experimental results showed an improvement in the micro/nanoscale structure, which optimizes the superhydro-phobic and anticorrosive behavior due to the air trapped inside the nanotextured surface. In addi-tion, once the best coating was selected, centrifugal ice adhesion tests (CAT) were carried out for two types of icing conditions (glaze and rime) simulated in an ice wind tunnel (IWT) on both as-deposited and liquid-infused coatings (SLIPs). The liquid-infused coatings showed a low water adhesion (low contact angle hysteresis) and low ice adhesion strength, reducing the ice adhesion four times with respect to PTFE (a well-known low-ice-adhesion material used as a reference).