Showing papers by "Ignacio R. Matias published in 2013"

Lossy mode resonance optical fiber sensor to detect organic vapors

Abstract: A transmission sensor able to detect Volatile Organic Compounds (VOCs) has been developed using optical fiber with Plastic Cladding (PCS) Specifically, 15 cm of the cladding was removed in order to deposit an organometallic compound whose chemical structure is [Au 2 Ag 2 (C 6 F 5 ) 4 (C 6 H 5 C CC 6 H 5 ) 2 ] n along this section This complex reacts reversely in presence of organic vapors such as alcohols, therefore, it is used as sensing material The compound was altered to show a negative charge, so it can be deposited combined with a positive charged polymer by means of the Layer-by-Layer (LbL) method In this manner, as the nanolayers were deposited, Lossy Mode Resonances (LMRs) were induced and shifted The polymer nanolayers doped with the organometallic material accelerated the LMRs appearance with respect to the nanolayers without additive and so, it enhanced the spectral shift Once the construction process was completed, two LMRs were observed, choosing the second one to study the sensor behavior when it was placed at 66357 nm The sensor was exposed to different concentrations of ethanol, methanol and isopropanol vapors, showing sensitivities of 0417, 0520 and 263 nm ppm −1 , respectively In the case of methanol, the second LMR peak shows a remarkable blue shift of 100 nm The interference with water vapors is minor to 1 nm below 60%, whereas the effect of temperature is insignificant between 20 °C and 60 °C

A Lossy Mode Resonance optical sensor using silver nanoparticles-loaded films for monitoring human breathing

Abstract: This work is focused on the fabrication of a human breathing sensor based on the in situ synthesis of silver nanoparticles (Ag-NPs) inside a polymeric coating previously deposited on an optical fiber core by means of the Layer-by-Layer self-assembly. The Ag-NPs were created using a synthesis protocol consisting of a loading step of the Ag+ cations into the polymeric film and a further reduction step using dimethylamine borane (DMAB). The morphology and distribution of the Ag-NPs inside the polymeric coating have been studied using atomic force microscopy (AFM). Furthermore, UV–VIS spectroscopy and energy dispersive X-ray (EDX) were also used to confirm the synthesis of the Ag-NPs within the resultant coating. The amount of Ag-NPs increases when the number of loading/reduction cycles is higher. Therefore the incorporation of the Ag-NPs affects the refractive index of the overlay promoting the observation of a resonant attenuation band in the infrared region (NIR), known as Lossy Mode Resonance (LMR), which can be used as a sensing signal to monitor the human breathing. The quality of the device has been experimentally tested with good sensitivity (0.455 nm per RH%) and fast response time (692 ms and 839 ms for rise/fall).

Electrospun nanofiber mats for evanescent optical fiber sensors

Abstract: 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).

Comparative study of layer-by-layer deposition techniques for poly(sodium phosphate) and poly(allylamine hydrochloride)

Abstract: An inorganic short chain polymer, poly(sodium phosphate), PSP, together with poly(allylamine hydrochloride), PAH, is used to fabricate layer-by-layer (LbL) films. The thickness, roughness, contact angle, and optical transmittance of these films are studied depending on three parameters: the precursor solution concentrations (10-3 and 10-4 M), the number of bilayers deposited (20, 40, 60, 80, and 100 bilayers), and the specific technique used for the LbL fabrication (dipping or spraying). In most cases of this experimental study, the roughness of the nanofilms increases with the number of bilayers. This contradicts the basic observations made in standard LbL assemblies where the roughness decreases for thicker coatings. In fact, a wide range of thickness and roughness was achieved by means of adjusting the three parameters mentioned above. For instance, a roughness of 1.23 or 205 nm root mean square was measured for 100 bilayer coatings. Contact angles close to 0 were observed. Moreover, high optical transmittance is also reported, above 90%, for 80 bilayer films fabricated with the 10-4 M solutions. Therefore, these multilayer structures can be used to obtain transparent superhydrophilic surfaces.

Experimental demonstration of lossy mode resonance generation for transverse-magnetic and transverse-electric polarizations

Abstract: This Letter, presents the fabrication of lossy mode resonance (LMR) devices based on titanium dioxide (TiO2)/ poly(sodium 4-styrenesulfonate) (PSS) coatings deposited on side-polished D-shaped optical fibers. TiO2 thin films have been obtained by means of the layer-by-layer (LbL) self-assembly technique. LbL enables us to produce smooth and homogeneous coatings on the polished side of the fiber. This permits us to couple light from the waveguide to the TiO2-coating/external medium region at specific wavelength ranges. The generation of LMRs depends on the coating thickness, so that thicker coatings can produce more resonances. LMRs are sensitive to the external medium refractive index, which allows its utilization as refractometers. The characteristic D-shaped architecture of the devices employed in this Letter enables us to distinguish TE and TM polarizations, which had not been possible before with regular optical fibers due to their cylindrical symmetry. The results presented here show for the first time the experimental demonstration of the generation of LMRs produced by both TM and TE polarizations. More specifically, for these TiO2/PSS thin films, the TM and TM modes of the LMRs show a wavelength shift of 226 nm for the first-order LMR and 56 nm for the second-order LMR.

Mode transition in complex refractive index coated single-mode–multimode–single-mode structure

Abstract: By coating a single-mode-multimode-single-mode (SMS) structure with a high refractive index thin-film it is possible to obtain a transition of modes for specific combinations of thin-film thickness, thin-film refractive index and surrounding medium refractive index, which permits to develop devices with a high sensitivity to specific parameters. In order to gain a better knowledge of the phenomenon the experimental results are corroborated numerically with the Transfer-Matrix-Method. The influence of losses in the thin-film has also been studied. The results obtained prove that a thin-film coated SMS structure is a simple and cost-effective platform for development of sensors and optical filters.

Multicolor Layer-by-Layer films using weak polyelectrolyte assisted synthesis of silver nanoparticles

Abstract: In the present study, we show that silver nanoparticles (AgNPs) with different shape, aggregation state and color (violet, green, orange) have been successfully incorporated into polyelectrolyte multilayer thin films using the layer-by-layer (LbL) assembly. In order to obtain colored thin films based on AgNPs is necessary to maintain the aggregation state of the nanoparticles, a non-trivial aspect in which this work is focused on. The use of Poly(acrylic acid, sodium salt) (PAA) as a protective agent of the AgNPs is the key element to preserve the aggregation state and makes possible the presence of similar aggregates (shape and size) within the LbLcolored films. This approach based on electrostatic interactions of the polymeric chains and the immobilization of AgNPs with different shape and size into the thin films opens up a new interesting perspective to fabricate multicolornanocomposites based on AgNPs.

Optimization of Sensors Based on Multimode Interference in Single-Mode–Multimode–Single-Mode Structure

Abstract: By coating a single-mode-multimode-single-mode (SMS) structure with a complex refractive index thin-film the central wavelength of the transmission and attenuation bands of the optical spectrum can be shifted. By adequate selection of multimode segment length and diameter, the thin-film thickness and the thin-film refractive index, the sensitivity of the device to the surrounding medium refractive index, the thickness of the thin-film or the refractive index of the thin-film can be optimized. Experimental results are corroborated numerically with the transfer matrix method.

Tunable electro-optic wavelength filter based on lossy-guided mode resonances

Abstract: In this work an optical fiber tunable filter based on lossy guided-mode resonances (LGMR) is proposed. It consists of a multilayer structure deposited onto the surface of a plastic cladding removed multimode fiber. The first layer is used to generate the LGMR and to work as the first electrode as well; the second one to tune the filter and the outer layer forms the other electrode. The fabricated filter has demonstrated a good sensitivity to the applied voltage showing a change of the LGMR wavelength of 0.4 nm/V. Among other applications, this filter is intended to be used as electro-optic wavelength filter or modulator.

Considerations for Lossy-Mode Resonance-Based Optical Fiber Sensor

Abstract: This paper presents the fabrication of optical fiber relative humidity (RH) sensors by means of polymeric thin-films as lossy-mode resonance (LMR) supporting coatings. In particular, LMRs are observed because of the fabrication of polyallylamine hydrochloride (PAH) and polyacrylic acid (PAA) polymeric coatings onto cladding-removed multimode optical fibers on applying the layer-by-layer self-assembly method. More than one LMR can be generated as a function of the coating thickness. The generation of multiple LMRs produces notch band filter with a rejection band in the visible region. To compare the parameters of different LMRs, two devices with PAH/PAA coating thicknesses of 140 and 470 nm, respectively, are fabricated. The thickness and the refractive index of the PAH/PAA film can be modified as a function of the surrounding medium refractive index. Thus, surrounding medium relative humidity can be easily determined through the wavelength shift of the resonance (~ 34 nm between 20% and 80% RH).

Development of a Low Mobility IEEE 802.15.4 Compliant VANET System for Urban Environments

Abstract: The use of Vehicular Ad-Hoc Networks (VANETs) is growing nowadays and it includes both roadside-to-vehicle communication (RVC) and inter-vehicle communication (IVC). The purpose of VANETs is to exchange useful information between vehicles and the roadside infrastructures for making an intelligent use of them. There are several possible applications for this technology like: emergency warning system for vehicles, cooperative adaptive cruise control or collision avoidance, among others. The objective of this work is to develop a VANET prototype system for urban environments using IEEE 802.15.4 compliant devices. Simulation-based values of the estimated signal strength and radio link quality values are obtained and compared with measurements in outdoor conditions to validate an implemented VANET system. The results confirm the possibility of implementing low cost vehicular communication networks operating at moderate vehicular speeds.

Accessing KNX Devices using USB/KNX Interfaces for Remote Monitoring and Storing Sensor Data

Abstract: Nowadays is very common for homes or buildings in general to have some kind of automation system for the efficient use of energy and for common comfort matters like illumination and blinds & shutters controlling, among others. It can easily add to these systems different kind of sensors for different uses like: monitoring building structure health, monitoring elder people behavior, etc… In this work we have developed a system that access data from connected KNX sensor devices and sends it remotely to a MySQL server using IP packets.

Energy Management System proposal for efficient smart homes

Abstract: In this paper we propose an Energy Management System for the efficient use of the power generated by a Smart Home and the power consumed by the building's electric appliances. An overall system description, from software protocol to employed hardware is presented. Simulation results are presented in order to show the viability in the application of the proposed Energy Management System.

C-reactive protein aptasensor for early sepsis diagnosis by means of an optical fiber device

Abstract: This work presents the development of a fast response, low cost and real time monitoring biosensor for sepsis diagnosis by means of the detection of C-reactive protein (CRP) as a sepsis biomarker. The developed sensor has two main features. The first one consists of the utilization of high sensitive optical fiber refractometers based on Lossy Mode Resonances (LMRs). The second is the utilization of CRP-selective and high sensitive aptamer chains as the sensing element (bio-receptor). Thin polymer/aptamer films were fabricated using the Layer-by-Layer (LbL) technique onto the optical fiber device in order to facilitate the detection of the aptamer refractive index changes in presence of CRP. Obtained devices were able to discriminate between a non-pathological concentration (2mg/L) and a pathological concentration (20mg/L) of CRP in less than 15 min. In addition, these sensors could be reused after a proper decontamination process which enhances their lifetime.

Humidity sensor fabricated by deposition of SnO2 layers onto optical fibers

Abstract: In this work, the fabrication and characterization of novel humidity sensors based on Lossy Mode Resonances (LMR) is presented. Tin oxide (SnO 2 ) coatings fabricated onto optical fibers are used as LMR supporting coatings. The SnO 2 based refractometers showed an average sensitivity of 6715 nm/refractive index unit (RIU) in the range 1.333–1.420 RIU. The behavior of this optical fiber device as relative humidity (RH) sensor was also tested, monitoring its response to different surrounding humidity levels. The results show a sensitivity of 0.1 nm/RH% in the range from 20% to 80% RH.

Optical Fiber Sensors Based on Lossy Mode Resonances

Abstract: In the last decades, optical fiber sensors have played an important role in niche applications because of their advantages over electronic sensors. First of all, optical fiber makes possible the multiplexing of a large amount of sensor data over long distances. This feature allows placing the sensing devices at kilometers from the electronic systems used to process the information. In addition, optical fiber is made of dielectric materials. Consequently, optical fiber sensors are not affected by electromagnetic fields, what makes them suitable to be used in situations under high electromagnetic fields or radiation doses [1]. Furthermore, this technology can be also used in medical applications due to its biocompatibility and has acquired a great importance in the development of biomedical instrumentation. Other interesting advantages of optical fiber sensors are their small size or their wide temperature working range [2-5].

Engineering outreach programs at the Public University of Navarre: A holistic approach

Abstract: A set of outreach initiatives implemented at the School of Industrial and Telecommunications Engineering of the Public University of Navarre is described. During the six academic years where these initiatives have been carried out, a 10% increase in the intake of engineering students has been observed, which is even more valuable considering the global decrease of new students in the region during this period. Feedback from students evidences that the activities carried out improve knowledge about the degrees offered and motivation towards engineering studies, specially the onsite workshops programmed at high schools and the open-door day.

Sensitivity enhancement of a humidity sensor based on poly(sodium phosphate) and poly(allylamine hydrochloride)

Abstract: The particular behavior of poly(sodium phosphate) (PSP) when it is deposited by means of the spraying layer-by-layer (LbL) technique has been used here to enhance the response of optical fiber humidity sensors. The roughness of the PSP films varies depending on the concentration of the polymeric solutions. In this work, it is demonstrated that this special feature of PSP allows the fabrication of optical fiber humidity sensors with different responses. Particularly, multilayer thin-films made of 10-3 and 10-4 M PSP and poly(allylamine hydrochloride) (PAH) solutions have been studied and used for the fabrication of optical fiber interferometers sensitive to humidity. To our knowledge this is the first time that the spray-assisted LbL technique has been used for the fabrication of optical fiber sensors.

City & technology: An analysis matrix to serve citizens

Abstract: The history of cities is that of it citizens: they have decided their location, configuration, development and growth. This has been possible along the years from several evolving technologies put at disposal by the inhabitants themselves. Now we are facing a new digital revolution, an evolution of communications grids and new schemes of productive systems. The traditional technological scenario is reset. Thus we see the need for a tool to approaching the different technologies based on its usefulness and consequences, considering the impact of each application. With it, the information and communication technologies that manage and transform the twenty-first century cities can be reviewed, analyzing their impact on new social behaviours that shapes the spaces and means of communication or distribution channels, as well as the integrated management between the cities and territories, considering the final impact on the citizen: principle and ultimate goal of all urban performance.

High sensitivity optical fiber pH sensor using poly(acrylic acid) nanofibers

Abstract: In this work a new optical fiber pH sensor based on the deposition of poly(acrylic acid) (PAA) using the electrospinning technique is presented. The optical fiber structure consists of a 4 cm segment of hollow core fiber (50/150μm) spliced between two standard multimode fibers onto which the nanoweb is deposited. The sensitive layer is a membrane composed by PAA nanofibers deposited onto the surface of an optical fiber. The sensor has a repetitive behavior and low hysteresis in the pH range 4-7, with an average sensitivity of 0,53 dB/pH.

Impact of Wireless Sensor Networks in the advancement of Ambient Intelligence and Smart Cities

Abstract: In this work, the performance of Wireless Sensor Networks (WSN) based on IEEE 802.15 standard in complex indoor environments is analyzed. By employing an in house developed determistic 3D Ray Launching code, estimation of diverse operational parameters of Bluetooth as well as ZigBee networks for specific Ambient Intelligence applications is shown. The adequate consideration of the topology and morphology of these networks leads to minimizing energy consumption while optimizing their operational performance. This approach can be employed in the massive deployment of WSN in future Smart Cities.