Open Access
Visible light activation of gold nanoparticles embedded into titanium dioxide surface in electrospun polymeric coatings
(MDPI, 2024) Sandúa Fernández, Xabier; Rivero Fuente, Pedro J.; Calvopiña, Jonathan; Rodríguez Trías, Rafael; Ingeniería; Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2
This work reports the development of a functional photocatalytic coating based on a combination of polymeric electrospun fibres and nanoparticles that is intended to be activated in the visible light range. In this sense, the resulting fibres can act as an effective matrix for the incorporation of titanium dioxide (TiO2) particles, which are covered by gold nanoparticles (AuNPs), in the outer surface of the metal oxide precursor. In the first step of the process, the optical properties of the nanoparticles were determined by UV-Vis spectroscopy. The extension of the visible absorption can be associated to the localized surface plasmon resonance (LSPR) of the metallic AuNPs. In addition, the resultant particle size distribution and average particle diameter was evaluated by dynamic light scattering (DLS) measurements. Furthermore, the phase composition and porosity of the functional particle powder were analysed by an XRD and N2 adsorption test. In the second step, these synthesized particles have been successfully immobilized into a PAA + β-CD electrospun fibre matrix by using the two different deposition methods of dip-coating and solution-casting, respectively. The morphological characterization of the samples was implemented by means of scanning electron microscopy (SEM), showing uniform and homogeneous, free-beaded fibres with a random distribution of the synthesized particles deposited onto the electrospun fibres. Then, the functional coatings were removed from the substrate, and a thermogravimetric (TGA) analysis was carried out for each sample in order to obtain the precursor mass immobilized in the coating. Once the overall mass of precursor was obtained, the percentage of TiO2 particles and AuNPs in the precursor was calculated by using inductively coupled plasma atomic emission spectrometry (ICP-AES). Finally, the photocatalytic activity of both functional solution and electrospun coatings were evaluated in terms of a gradual degradation of rhodamine B (RhB) dye after continuous exposition to a visible-light lamp.
Open Access
Electrospun nanofiber mats for evanescent optical fiber sensors
(Elsevier, 2013) Urrutia Azcona, Aitor; Goicoechea Fernández, Javier; Rivero Fuente, Pedro J.; Matías Maestro, Ignacio; Arregui San Martín, Francisco Javier; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute of Smart Cities - ISC; Ingeniería; Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
In this work, a study about the optical response of electrospun nanofiber (ENF) coatings for their use in evanescent optical fiber sensors is presented. Several types of ENF mats composed of poly(acrylic acid) (PAA) were developed with different ENF diameters and densities. These ENF mats were deposited onto an optical fiber core in order to fabricate humidity evanescent optical fiber sensors. The devices were exposed to relative humidity (RH) variations from 30% RH to 95%RH. The transfer functions of the devices (transmitted optical power versus relative humidity) presented two well-differenced behaviors depending on the ENF diameter and the ENF mat density. The devices with lower ENF diameters and higher mat density showed an increase in the transmitted optical power when RH increased. On the contrary, the devices with higher ENF diameters and lower mat density showed a decrease in the transmitted optical power when RH increased. In addition to this, sensors with thinner ENF overlays, showed a higher sensitivity. In order to study the response time of these devices, the ENFs sensors were submitted to human breathing cycles and presented a response time around 340 ms (exhalation). In spite of the high RH conditions of this experiment, the devices showed a recovery time around 210 ms and a negligible hysteresis or drift with respect to the initial condition (inhalation).
Open Access
An antibacterial submicron fiber mat with in situ synthesized silver nanoparticles
(Wiley, 2012) Rivero Fuente, Pedro J.; Urrutia Azcona, Aitor; Goicoechea Fernández, Javier; Rodríguez, Yoany; Corres Sanz, Jesús María; Arregui San Martín, Francisco Javier; Matías Maestro, Ignacio; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute of Smart Cities - ISC; Ingeniería; Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2
This work presents an alternative approachfor fabricating electrospun submicron highly hydrophilicfiber mats loaded with silver nanoparticles. These fiber matsshow a high efficient antibacterial behavior, very attractivefor applications like wound healing and skin regenerationprocesses. The fabrication method is divided in two steps.First, poly(acrylic acid) (PAA) and b-cyclodextrin (b-CD)submicron fibers were electrospun and further stabilizedusing a thermal treatment, yielding stable hydrogel-likefibers with diameters ranging from 100 nm up to severalmicrons. In the second step, silver ions were loaded into thefibers and then reduced to silver nanoparticles in-situ. Theelectrospinning parameters were adjusted to achieve thedesired properties of the fiber mat (density, size) and after-wards, the characteristics of the silver nanoparticles(amount, size, aggregation) were tuned by controlling thesilver ion loading mechanism. Highly biocide surfaces wereachieved showing more than 99.99% of killing efficiency.The two-step process improves the reproducibility and tun-ability of the fiber mats. To our knowledge, this is the firsttime that stable hydrogel fibers with a highly biocide behav-ior have been fabricated using electrospinning.
Open Access
Layer-by-layer nano-assembly: a powerful tool for optical fiber sensing applications
(MDPI, 2019) Rivero Fuente, Pedro J.; Goicoechea Fernández, Javier; Arregui San Martín, Francisco Javier; Ingeniaritza; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute for Advanced Materials and Mathematics - INAMAT2; Institute of Smart Cities - ISC; Ingeniería; Ingeniería Eléctrica, Electrónica y de Comunicación
The ability to tune the composition of nanostructured thin films is a hot topic for the design of functional coatings with advanced properties for sensing applications. The control of the structure at the nanoscale level enables an improvement of intrinsic properties (optical, chemical or physical) in comparison with the traditional bulk materials. In this sense, among all the known nanofabrication techniques, the layer-by-layer (LbL) nano-assembly method is a flexible, easily-scalable and versatile approach which makes possible precise control of the coating thickness, composition and structure. The development of sensitive nanocoatings has shown an exceptional growth in optical fiber sensing applications due to their self-assembling ability with oppositely charged components in order to obtain a multilayer structure. This nanoassembly technique is a powerful tool for the incorporation of a wide variety of species (polyelectrolytes, metal/metal oxide nanoparticles, hybrid particles, luminescent materials, dyes or biomolecules) in the resultant multilayer structure for the design of high-performance optical fiber sensors. In this work we present a review of applications related to optical fiber sensors based on advanced LbL coatings in two related research areas of great interest for the scientific community, namely chemical sensing (pH, gases and volatile organic compounds detection) as well as biological/biochemical sensing (proteins, immunoglobulins, antibodies or DNA detection).
Open Access
An antibacterial surface coating composed of PAH/SiO2 nanostructurated films by layer by layer
(Wiley, 2010) Urrutia Azcona, Aitor; Rivero Fuente, Pedro J.; Ruete Ibarrola, Leyre; Goicoechea Fernández, Javier; Fernández Valdivielso, Carlos; Arregui San Martín, Francisco Javier; Matías Maestro, Ignacio; Ingeniería; Ingeniaritza; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2; Institute of Smart Cities - ISC
In this work we propose a novel antibacterial coating composed of SiO2 and the polymer Poly(allylamine hydrochloride) (PAH). The coating was fabricated by the technique Layer-by-Layer (LbL). This technique has already been used in previous works, and it has the advantage that it allows to control the construction of nanosized and well organized multilayer films. Here, the new nanotexturized LbL SiO2 surface acts as antibacterial agent. The fabricated coatings have been tested in bacterial cultures of genus Lactobacillus to observe their antibacterial properties. It has been demonstrated these PAH/SiO2 coating films have a very good antimicrobial behaviour against this type of bacteria.
Open Access
Layer-by-layer assembly as a powerful nanofabrication technique for the design of antimicrobial surfaces in the textile industry
(Taylor & Francis, 2022) Rivero Fuente, Pedro J.; Ingeniería; Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2
In this work, the fabrication of multilayer structures has been presented by using the layer-by-layer (LbL) nanoassembly technique with the aim to prevent the bacterial adhesion, pathogen colonization, or even contact-killing bacteria. The use of this nanofabrication technique is of great interest because the resultant thickness of the films can be perfectly controlled as a function of the electrostatic attraction between positive and negative charged compounds. In addition, this technique shows a great versatility because it can be implemented to a wide variety of substrates with any shape and composition (i.e., polymers, composites, medical devices, metallic substrates) without using any expensive equipment. In some cases, the polyelectrolytes can play a dual role for preparing multilayer antimicrobial surfaces. The first one is that most of them can be used for embedding active compounds, which can be released in a further step, while the second one, controlling the pH of the dipping cationic polyelectrolyte solutions can induce the presence of higher protonated charges in the outer surface, which 256can act as a better effective antimicrobial activity. Finally, a perspective in detail of these different approaches will be deeply analyzed against different bacterial strains.
Open Access
In situ synthesis of gold nanoparticles in layer-b y-layer polymeric coatings for the fabrication of optical fiber sensors
(MDPI, 2022) Martínez Hernández, María Elena; Goicoechea Fernández, Javier; Rivero Fuente, Pedro J.; Arregui San Martín, Francisco Javier; Ingeniaritza; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Institute for Advanced Materials and Mathematics - INAMAT2; Ingeniería; Ingeniería Eléctrica, Electrónica y de Comunicación
A new method is proposed to tune the interferometric response of wavelength-based optical fiber sensors. Using the nanoparticle in situ synthesis (ISS) technique, it is possible to synthesize gold nanoparticles (AuNPs) within a pre-existing polymeric thin film deposited at the end-face of an optical fiber. This post-process technique allows us to adjust the optical response of the device. The effect of the progressive synthesis of AuNPs upon polymeric film contributed to a remarkable optical contrast enhancement and a very high tuning capability of the reflection spectra in the visible and near-infrared region. The spectral response of the sensor to relative humidity (RH) variations was studied as a proof of concept. These results suggest that the ISS technique can be a useful tool for fiber optic sensor manufacturing.
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
Corrosion of cast aluminum alloys: a review
(MDPI, 2020-10-16) Berlanga Labari, Carlos; Biezma Moraleda, María Victoria; Rivero Fuente, Pedro J.; Ingeniería; Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2
Research on corrosion resistance of cast aluminum alloys is reviewed in this article. The effect of the main microstructural features of cast aluminum alloys such as secondary dendrite arm spacing (SDAS), eutectic silicon morphology, grain size, macrosegregation, microsegregation, and intermetallic compounds is discussed. Moreover, the corrosion resistance of cast aluminum alloys obtained by modern manufacturing processes such as semi-solid and additive manufacturing are analyzed. Finally, the protective effects provided by different coatings on the aluminum cast alloys—such as anodized, plasma electrolytic oxidation (PEO), and laser—is reviewed. Some conclusions and future guidelines for future works are proposed.
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.