Turduev, M.; Giden, I.; ; Babayigit, C.; Bor, E.; Boztug, Ç.; Kurt, H. Sensors and actuators B. Chemical Vol. 245, p. 765-773 DOI: 10.1016/j.snb.2017.02.016 Data de publicació: 2017-06-01 Article en revista
In this paper, we propose and design a new type of an integrated optical sensor that performs sensing in a wide wavelength range corresponding to mid-infrared (mid-IR) spectrum. By engineering the structural parameters of square-lattice photonic crystal (PC) slab incorporated with a T-shaped air-slot, strong light confinement and interaction with the analytes are assured. Numerical analyses in the time and frequency domain are conducted to determine the structural parameters of the design. The direct interaction between the slot waveguide mode and the analyte infiltrated into the slot gives rise to highly sensitive refractive index sensors. The highest sensitivity of the proposed T-slotted PC sensor is 1040 nm/RIU within the range of analytes’ refractive indices n = 1.05-1.10, and the overall sensitivity corresponding to the higher refractive index range of n = 1.10-1.30 is around 500 nm/RIU. Moreover, for a realistic PC slab structure, we determined an average refractive index sensitivity of 530 nm/RIU within the range of n = 1.10-1.25 and an average sensitivity of 390 nm/RIU within the range of n = 1.00-1.30. Furthermore, we speculate on the possible approach for the fabrication and the optical characterization of the device. The assets of the device include being compact, having a feasible measurement and fabrication technique, and possessing label-free sensing characteristic. We expect that the presented work may lead to the further development of the mid-IR label-free biochemical sensor devices for detection of various materials and gases in the near future.
The objective of this paper is to show the first results obtained with a gas sensor made of Au-functionalized WO3 nanoneedles working under a closed-loop control designed to reduce its time response. The average temperature applied to the sensor is modulated to keep constant the average surface potential of the sensing nanostructures. This is done by periodically monitoring the resistivity of the sensing layer and generating temperature waveforms that enforce the condition: constant resistivity of the sensing layer at a reference temperature. Changes induced by the target gases must be compensated by changes in the average temperature being applied to the sensing layer. This signal, the average temperature applied to the sensor, is the new sensor output.
Fonollosa, J.; Fernandez, L.; Gutiérrez-Gálvez, A.; Huerta, R.; Marco, S. Sensors and actuators B. Chemical Vol. 236, p. 1044-1053 DOI: 10.1016/j.snb.2016.05.089 Data de publicació: 2016-05-18 Article en revista
Inherent variability of chemical sensors makes it necessary to calibrate chemical detection systems individually. This shortcoming has traditionally limited usability of systems based on metal oxide gas sensor arrays and prevented mass-production for some applications. Here, aiming at exploring calibration transfer between chemical sensor arrays, we exposed five twin 8-sensor detection units to different concentration levels of ethanol, ethylene, carbon monoxide, or methane. First, we built calibration models using data acquired with a master unit. Second, to explore the transferability of the calibration models, we used Direct Standardization to map the signals of a slave unit to the space of the master unit in calibration. In particular, we evaluated the transferability of the calibration models to other detection units, and within the same unit measuring days apart. Our results show that signals acquired with one unit can be successfully mapped to the space of a reference unit. Hence, calibration models trained with a master unit can be extended to slave units using a reduced number of transfer samples, diminishing thereby calibration costs. Similarly, signals of a sensing unit can be transformed to match sensor behavior in the past to mitigate drift effects. Therefore, the proposed methodology can reduce calibration costs in mass-production and delay recalibrations due to sensor aging. Acquired dataset is made publicly available
Almar, L.; Tarancón, A.; Andreu, T.; Torrell, M.; Hu, Y.; Dezanneau, G.; Morata, A. Sensors and actuators B. Chemical Vol. 216, p. 41-48 DOI: 10.1016/j.snb.2015.04.018 Data de publicació: 2015-09-01 Article en revista
Mesoporous materials have been studied as high performance sensing materials due to their singular microstructure and extremely high surface-to-volume ratio. However, the lack of stability of these nanostructures is assumed as one of the major drawbacks toward their application in real devices. In this work, this limitation is overcome by the synthesis of thermally stable mesoporous gadolinium doped ceria. Humidity sensors were fabricated and tested under different (i.e. humidity and temperature) conditions. The mesoporous layers were attached to the substrate at 900 °C preserving mesoporous structure intact. This process at high temperature provides the layer with a mechanical strength and allows self-cleaning cycles at high temperatures if required. The humidity sensing mechanism is presented and discussed in detail by means of impedance spectroscopy. An ionic type of conduction mechanism is corroborated. Fast response and recovery, as well as very low hysteresis and no drift are observed.
It was also shown that the response of the devices can be straightforwardly tuned by changing layer thickness or pore size, allowing to fulfill sensing needs of different applications. All the mentioned properties joined to the simplicity of the fabrication and the flexibility of the used fabrication route for synthesizing any other metal oxide make this kind of devices a potential group for developing high performance and fast gas sensors.
Metal oxide (MOX) gas sensors arrays are a predominant technological choice to perform fundamental tasks of chemical detection. Yet, their use has been mainly limited to relatively controlled instrument configurations where the sensor array is placed within a closed measurement chamber. Usually, the experimental protocol is defined beforehand and it includes three stages: the array is first exposed to a gas reference, then to the gas sample, and finally to the reference again to recover the initial state. Such sampling procedure requires signal acquisition during the complete experimental protocol and usually delays the output prediction until the predefined measurement duration is complete. Due to the slow time response of chemical sensors, the completion of the measurement typically requires minutes. In this paper we propose the use of reservoir computing (RC) algorithms to overcome the slow temporal dynamics of chemical sensor arrays, allowing identification and quantification of chemicals of interest continuously and reducing measurement delays. We generated two datasets to test the ability of RC algorithms to provide accurate and continuous prediction to fast varying gas concentrations in real time. Both datasets – one generated with synthetic data and the other acquired from actual gas sensors – provide time series of MOX sensors exposed to binary gas mixtures where concentration levels change randomly over time. Our results show that our approach improves the time response of the sensory system and provides accurate predictions in real time, making the system specifically suitable for online monitoring applications. Finally, the collected dataset and developed code are made publicly available to the research community for further studies.
Zadorozhnaya , O.; Kirsanov , D.; Buzhinsky , I.; Tsarev , F.; Abramova , N.; Andrey, B.; Muñoz, F.; Ribó, J.; Bori, J.; Riva, M.; Legin, A. Sensors and actuators B. Chemical Vol. 207, p. 1069-1075 DOI: 10.1016/j.snb.2014.08.056 Data de publicació: 2015-02 Article en revista
This report describes the application of potentiometric multisensory system for estimation of water samples toxicity in terms of Microtox ® analyzer—a widespread instrument for toxicity evaluation. The working principle of Microtox ® analyser is based on a registration of luminescence from Vibrio fischeri bacteria. This luminescence depends on metabolism conditions and toxicity of the environment. Due to the fact that metabolism is influenced by multiple parameters the method is associated with certain limitations. Unlike this bioassay procedure the employment of multisensory system does not require the use of living organisms and can provide for faster toxicity evaluation. Fifty-five real and model polluted water samples, for which the toxicity was established by bioassay, were studied. The response of multisensory array processed with machine learning techniques allows for prediction of toxicity in terms of EC50 with relative errors of 20–25%. Taking into account the complexity of the task (simulation of complex biological reactions with inanimate instrument) this can be considered as a good promise for further research in this direction in order to develop instrumental alternative for toxicity assessment
Ziyatdinov, A.; Fonollosa, J.; Valentin-Fernandez, L.; Gutierrez, A.; Marco, S.; Perera, A. Sensors and actuators B. Chemical Vol. 206, p. 538-547 DOI: 10.1016/j.snb.2014.09.001 Data de publicació: 2015-01-01 Article en revista
The design of bioinspired systems for chemical sensing is an engaging line of research in machine olfaction. Developments in this line could increase the lifetime and sensitivity of artificial chemo-sensory systems. Such approach is based on the sensory systems known in live organisms, and the resulting developed artificial systems are targeted to reproduce the biological mechanisms to some extent. Sniffing behaviour, sampling odours actively, has been studied recently in neuroscience, and it has been suggested that the respiration frequency is an important parameter of the olfactory system, since the odour perception, especially in complex scenarios such as novel odourants exploration, depends on both the stimulus identity and the sampling method. In this work we propose a chemical sensing system based on an array of 16 metal-oxide gas sensors that we combined with an external mechanical ventilator to simulate the biological respiration cycle. The tested gas classes formed a relatively broad combination of two analytes, acetone and ethanol, in binary mixtures. Two sets of low-frequency and high-frequency features were extracted from the acquired signals to show that the high-frequency features contain information related to the gas class. In addition, such information is available at early stages of the measurement, which could make the technique suitable in early detection scenarios. The full data set is made publicly available to the community. (C) 2014 Elsevier B.V. All rights reserved.
Sánchez, B.; Vega, D.; Rodriguez, A.; Bragos, R.; Marco, M.P.; Valera, E. Sensors and actuators B. Chemical Vol. 203, p. 444-451 DOI: 10.1016/j.snb.2014.06.139 Data de publicació: 2014-11-01 Article en revista
A magnetic interdigitated microelectrode (m-ID mu E) has been developed, characterized and evaluated. In order to demonstrate the potential use of these electrodes in the biosensors field, impedimetric measurements of bovine serum albumin (BSA) biofunctionalized magnetic mu-particles (BSAMP) were performed. Thanks to their magnetic capabilities and to the use of magnetic mu-particles, the developed electrodes were successfully regenerated and could be reused several times. The classical stepped-sine impedance spectroscopy (IS) technique and the state-of-art frequency response analyzer (FRA) multisine IS method based on the local polynomial method (LPM) were used as measurement techniques. The significant reduction of measuring time and accuracy of the multisine IS LPM-based technique reveals a promising performance for fast and accurate real-time on-line screening applications. (C) 2014 Elsevier B.V. All rights reserved.
Fonollosa, J.; Rodriguez-Lujan, I.; Shevade, A.; Homer, M.; Ryan, M.; Huerta, R. Sensors and actuators B. Chemical Vol. 199, p. 398-402 DOI: 10.1016/j.snb.2014.03.102 Data de publicació: 2014-04-03 Article en revista
A chemical detection system made of a gas sensor array and algorithms intended to monitor human activity was tested in a NASA spacecraft cabin simulator. Such a chemical-based monitoring system, if extended to home settings, would allow the autonomous detection of emergency situations, thereby postponing the moving of elderly people to assisted living facilities and improving their quality of life. Moreover, in contrast to other monitoring systems based on wearable sensors or video cameras, a monitoring system based on measuring changes in air composition induced by human activities would be non-invasive and would not raise privacy concerns when installed in homes. The third generation of the JPL sensor array was adapted in a small, compact and portable system and deployed in a spacecraft-like room for four weeks while volunteers were performing daily routines. The system was able to predict the total number of people and the level of activity performed in the room, while detecting unexpectedly high concentrations of volatiles
Ziyatdinov, A.; Fernandez, E.; Chaudry, A.; Marco, S.; Persaud, K.C.; Perera, A. Sensors and actuators B. Chemical Vol. 177, p. 596-604 DOI: 10.1016/j.snb.2012.09.093 Data de publicació: 2013-02-01 Article en revista
Vergara, A.; Fonollosa, J.; Mahiques, J.; Trincavelli, M.; Rulkov, N.; Huerta, R. Sensors and actuators B. Chemical Vol. 185, p. 462-477 DOI: 10.1016/j.snb.2013.05.027 Data de publicació: 2013 Article en revista
Chemo-resistive transduction presents practical advantages for capturing the spatio-temporal and structural organization of chemical compounds dispersed in different human habitats. In an open sampling system, however, where the chemo-sensory elements are directly exposed to the environment being monitored, the identification and monitoring of chemical substances present a more difficult challenge due to the dispersion mechanisms of gaseous chemical analytes, namely diffusion, turbulence, and advection. The success of such actively changeable practice is influenced by the adequate implementation of algorithmically driven formalisms combined with the appropriate design of experimental protocols. On the basis of this functional joint-formulation, in this study we examine an innovative methodology based on the inhibitory processing mechanisms encountered in the structural assembly of the insect's brain, namely Inhibitory Support Vector Machine (ISVM) applied to training a sensor array platform and evaluate its capabilities relevant to odor detection and identification under complex environmental conditions. We generated — and made publicly available — an extensive and unique dataset with a chemical detection platform consisting of 72 conductometric metal-oxide based chemical sensors in a custom-designed wind tunnel test-bed facility to test our methodology. Our findings suggest that the aforementioned methodology can be a valuable tool to guide the decision of choosing the training conditions for a cost-efficient system calibration as well as an important step toward the understanding of the degradation level of the sensory system when the environmental conditions change.
Fonollosa, J.; Fernandez, L.; Huerta, R.; Gutiérrez-Gálvez, A.; Marco, S. Sensors and actuators B. Chemical Vol. 187, p. 331-339 DOI: 10.1016/j.snb.2012.12.026 Data de publicació: 2013 Article en revista
Stoycheva, T.; Vallejos, S.; Blackman, C.; Moniz, S.; Calderer, J. Sensors and actuators B. Chemical Vol. 161, num. 1, p. 406-413 DOI: 10.1016/j.snb.2011.10.052 Data de publicació: 2012-01-03 Article en revista
Urbiztondo, M.; Pellejero, I.; Rodriguez, A.; Pina, M.; Santamaría Ramiro, J. Sensors and actuators B. Chemical Vol. 157, num. 2, p. 450-459 DOI: 10.1016/j.snb.2011.04.089 Data de publicació: 2011-05-06 Article en revista
Inter-digital capacitors (IDCs) with electrode gaps of 10 or 50 microns have been coated with zeolite films consisting of different zeolites with Si/Al ratios ranging from 1.5 (zeolite A) to infinite (silicalite). The performance of the sensor in the measurement of humidity has been related to the electrical properties of the zeolites (relative permittivity, ɛr), which in turn is a function of their Si/Al ratio. With zeolites of a high Al content the limit of detection was under 0.5 ppmV.
Perera, A.; Pardo, A.; Barretino, D.; Hierlemann, A.; Marco, S. Sensors and actuators B. Chemical Vol. 146, num. 2, p. 477-482 DOI: 10.1016/j.snb.2009.11.037 Data de publicació: 2010-04-29 Article en revista
Ziyatdinov, A.; Marco, S.; Chaudry, A.; Persaud, K.C.; Caminal, P.; Perera, A. Sensors and actuators B. Chemical Vol. 146, num. 2, p. 460-465 DOI: 10.1016/j.snb.2009.11.034 Data de publicació: 2010-04-29 Article en revista
Fonollosa, J.; Halford, B.; Fonseca, L.; Santander, J.; Udina, S.; Moreno-Sereno, M.; Hildenbrand, J.; Wöllnestein, J.; Marco, S. Sensors and actuators B. Chemical Vol. 136, num. 2, p. 546-554 DOI: 10.1016/j.snb.2008.12.015 Data de publicació: 2009 Article en revista
Valera, E.; Ramón, J.; Sánchez, F.; Marco, M.P.; Rodriguez, A. Sensors and actuators B. Chemical Vol. 134, num. 1, p. 95-103 DOI: 10.1016/j.snb.2008.04.023 Data de publicació: 2008-09-28 Article en revista
A novel conductimetric immunosensor for atrazine detection has been designed and developed. This immunosensor is mainly based on antibodies labelled with gold nanoparticles. Additionally, the immunosensor consists of an array of two coplanar non-passivated interdigitated metallic µ-electrodes (IDµE) and immunoreagents specifically developed to detect this pesticide. The chemical recognition layer was covalent immobilized on the interdigital space. Immunochemical detection of the concentration of atrazine is achieved by a competitive reaction that occurs before the inclusion of the labelled antibodies. It is shown that the gold nanoparticles provide an amplification of the conductive signal and hence makes possible to detect atrazine by means of simple DC measurements.
The conductimetric immunosensor and its biofunctionalization steps have been characterized by chemical affinity methods and impedance spectroscopy.
This work describes the immunosensor structure, fabrication, physico-chemical and analytical characterization, and the immunosensor response using conductivity measurements. The immunosensor developed detects atrazine with limits of detection in the order of 0.1–1 µg L-1, far below the maximum residue level (MRL) (100 µg L-1) established by European Union (EU) for residues of this herbicide in the wine.
Although in this paper the competitive reaction occurs in buffer, an initial study of the wine matrix effect is also described.
Ricart, J.; Pons, J.; Dominguez, M.; Rodriguez, A.; Figueras, E.; Horrillo, M.; Gutiérrez, J.; Sayago, I. Sensors and actuators B. Chemical Vol. 134, num. 2, p. 773-779 DOI: 10.1016/j.snb.2008.06.031 Data de publicació: 2008-09-25 Article en revista
Pulsed digital oscillators (PDO) are sampled nonlinear structures that include a resonator device, a one-bit quantifier and a feedback loop with n-delays. PDOs can be used in a wide range of frequency-based sensing applications. This paper describes for the first time the application of PDOs as self-sustained oscillators in gravimetric sensors for volatile organic compounds (VOC) detection and measurement. For this application, the device is a MEMS cantilever with a polymer layer deposited on top of it. The deposited layer is mass-sensitive to the concentration of VOC, so that the concentration of VOC changes the oscillation frequency of the PDO. Two different polymeric materials have been tested: poly-epichlorohydrin (PECH) and poly-dimethylsiloxane (PDMS). Our results show that low concentrations of toluene and octane can be detected successfully. The practical influence of parameters, such as the MEMS damping losses on the sensor performance are also analyzed and experimentally tested. These are the first experimental results showing how PDOs can successfully track changes in the resonant frequency of MEMS resonators. (C) 2008 Elsevier B.V. All rights reserved.
Rodriguez, A.; Valera, E.; Ramón-Azcón, J.; Sanchez, J.; Marco, M.P.; Castañer, L. Sensors and actuators B. Chemical Vol. 129, num. 2, p. 921-928 DOI: 10.1016/j.snb.2007.10.003 Data de publicació: 2008-02-22 Article en revista
A novel impedimetric immunosensor for the detection of a wide variety of compounds, based on a two coplanar non-passivated interdigitated metallic µ-electrodes and non-labeled immunoreactives, has been designed and developed. A very useful detection method is the impedance spectroscopy sweeping a wide frequency range. This is a powerful, but cumbersome tool to study the sensor performance providing trustworthy results. In this work, it is shown that the exploitation of the changes observed of the impedance at a single frequency provide very good correlation with antibody concentration and hence greatly reduces the signal acquisition and processing complexity. It has thereby a great potential for low cost, low power, fast response and simple use for the in-field or at-line applications. In this work, the application of the method to atrazine detection is described. The results show that the immunosensor signal is a function of the pesticide concentration following a competitive binding relationship, with limits of detection lower than the maximum residue level required by EC for atrazine in wine grapes and other foodstuff products.
Fonollosa, J.; Rubio, R.; Hartwig, S.; Marco, S.; Santander, J.; Fonseca, L.; Wöllnestein, J.; Moreno-Sereno, M. Sensors and actuators B. Chemical Vol. 132, num. 2, p. 498-507 DOI: 10.1016/j.snb.2007.11.014 Data de publicació: 2008 Article en revista
Vallejos, S.; Khatko, V.; Aguir, K.; Ngo, K.; Calderer, J.; Gracia, I.; Cane, C.; Llobet, E.; Correig, X. Sensors and actuators B. Chemical Vol. 126, num. 2, p. 573-578 Data de publicació: 2007-10 Article en revista
Valera, E.; Ramón, J.; Rodriguez, A.; Castañer, L.; Sánchez, F.; Marco, M.P. Sensors and actuators B. Chemical Vol. 125, num. 2, p. 526-537 DOI: 10.1016/j.snb.2007.02.048 Data de publicació: 2007-08-08 Article en revista
A novel impedimetric immunosensor for atrazine detection, a widely used pesticide, is described. It is based on a two coplanar non-passivated interdigitated metallic µ-electrodes (IDµE) and the differential measurement of the impedance frequency spectrum. No redox electrodes have been included in the sensor. The chemical recognition layer was deposited on top of the interdigitated µ-electrodes area (fingers and inter-digits space). Immunochemical detection of the atrazine concentration is achieved by a competitive reaction without using any label. Furthermore immunoreagents specifically developed to detect this pesticide have been used.
The immunosensor and its functionalization steps have been characterized by means of chemical affinity methods and impedance spectroscopy. This work describes immunosensor development and its physico-chemical and analytical characterization. The immunosensor shows a limit of detection of 8.34 ± 1.37 µg L-1, which is lower than the Maximum Residue Level (MRL) (100 µg L-1) established by EU (European Union) for residues of atrazine as herbicide in the wine grapes and other foodstuff products.
González-Bellavista, A.; Macanás, J.; Muñoz, M.; Fàbregas, E. Sensors and actuators B. Chemical Vol. 125, num. 1, p. 100-105 DOI: 10.1016/j.snb.2007.01.051 Data de publicació: 2007-07-16 Article en revista
A novel arrangement for polymeric membranes used in anion-selective electrodes is presented. Sulfonated poly(ether ether ketone) (SPEEK), an ion conducting polymer has been used as a polymeric matrix to build an anion-selective electrode (ISE). A NO3--ISE has been chosen as a model electrode to study the efficiency of the polymeric membrane. The effect of membrane composition and polymer compatibility with the electro-active components was investigated. The polymer matrix showed good mechanical properties and can be solvent cast in complete analogy to traditional ISE membranes. SPEEK matrix was studied in order to optimize both the potentiometric response and the selectivity of the electrode. The electrode exhibited a linear response with a slope of -51mV per decade within the concentration range from 8.0×10-5 to 2.5×10-2 Mnitrate ion. The detection limit was found to be 5.0×10-5 M, and electrodes could be used over a wide pH range of 4–8. Finally, the sensor showed improved selectivity in comparison to some of the previously reported nitrate-selective electrodes
Muraviev, D.; Macanás, J.; Farre, M.; Muñoz, M.; Alegret, S. Sensors and actuators B. Chemical Vol. 118, num. 1-2, p. 408-417 DOI: 10.1016/j.snb.2006.04.047 Data de publicació: 2006-10-25 Article en revista
This paper reports the results obtained by development of novel approaches for inter-matrix synthesis and characterization of polymer stabilized metal nanoparticle (PSMNP), which can be applied in molecular recognition devices (MRD) such as, sensors and biosensors. The proposed approaches are based on the use of functionalized polymeric membranes as a nanoreactor for both synthesis and characterization of PSMNP. The desired functionalization is achieved by either chemical grafting of functional groups to the polymeric matrix or by using physical immobilization of the metal-selective extractants inside the polymer by using solid-phase-incorporated-reagents (SPHINER) technique. In both cases the functional groups of either extractant or functional polymer are able to chemically fix metal ions or complexes inside the parent polymeric matrix prior to their reduction and formation of PSMNP. The results obtained by the inter-matrix synthesis and characterization of Pt- and Cu-PSMNP in polymeric membranes and on the use of these polymer-metal nanocomposite membranes as sensing elements in modified graphite-epoxy composite electrodes are reported and discussed.
Perera, A.; Yamanaka, T.; Gutiérrez-Gálvez, A.; Gutierrez-Osuna, R.; Raman, B. Sensors and actuators B. Chemical Vol. 116, num. 1-2, p. 17-22 DOI: 10.1016/j.snb.2005.11.082 Data de publicació: 2006-07 Article en revista
Pardo, A.; Cámara, L.; Cabré, J.; Perera, A.; Cano, X.; Marco, S.; Bosch, J. Sensors and actuators B. Chemical Vol. 116, num. 1-2, p. 11-16 DOI: 10.1016/j.snb.2006.03.012 Data de publicació: 2006-07 Article en revista
González-Bellavista, A.; Macanás, J.; Muñoz, M.; Fábregas, E. Sensors and actuators B. Chemical Vol. 115, num. 2, p. 691-696 DOI: 10.1016/j.snb.2005.10.040 Data de publicació: 2006-06-26 Article en revista
Polysulfone (PS), a non-conductive polymer, is employed as an alternative material to polyvinyl chloride (PVC), the most used polymer in the design of ion-selective electrode (ISE) membranes to date.
A nitrate-ISE is chosen as a model electrode to study the efficiency of PS as a polymer matrix of the membrane. Tetra-octyl ammonium nitrate is used as ionophore and 2-nitrophenyl octyl ether as plasticizer. The polymer/plasticizer/ionophore ratio is optimized and the analytical performance parameters of the prepared electrodes are evaluated. The electrodes show a slope between 45 and 60 mV/decade (depending on the calibration medium and membrane composition). A linear range response between 1.0 × 10-4 and 3.0 × 10-2 M, and a lifetime of at least 1 month are obtained. The electrodes exhibit good selectivity for nitrate in respect to other anions.
Rubio, R.; Santander, J.; Fonollosa, J.; Fonseca, L.; Gràcia, I.; Cané, C.; Moreno-Sereno, M.; Marco, S. Sensors and actuators B. Chemical Vol. 116, num. 1-2, p. 183-191 DOI: 10.1016/j.snb.2006.03.018 Data de publicació: 2006 Article en revista
Amírola, J.; Rodriguez, A.; Castañer, L.; Santos, J.; Gutiérrez, J.; Horrillo, M. Sensors and actuators B. Chemical Vol. 11, num. 112, p. 247-253 DOI: 10.1016/j.snb.2005.07.053 Data de publicació: 2005-08 Article en revista
The design and fabrication of a simple and low-cost micromachined silicon capacitive device is reported. Application to the detection of volatile organic compounds (VOCs) based on capacitive variations due to induced differential surface stress is presented. Good results in terms of sensitivity, reproducibility and response and recuperation times have been obtained with this type of devices. Limits of detection (LoDs) for the measured gases are below 50 ppm for toluene and 10 ppm for octane. The responses to the tested gases are different thus we would be able to discriminate a mixture of them.
Rodriguez, A.; Molinero, D.; Valera, E.; Trifonov, T.; Marsal, L.; Pallarès, J.; Alcubilla, R. Sensors and actuators B. Chemical Vol. 109, num. 1, p. 135-140 DOI: 10.1016/j.snb.2005.03.015 Data de publicació: 2005-04 Article en revista
This paper presents a novel technique for silicon dioxide (SiO2) microneedle fabrication. Microneedles are hollow microcapillaries with tip diameters in the range of micrometers. They can be used in the fabrication of microsyringes. These structures can be of high interest in medical and biological applications, such as DNA injection, antibody manipulation and drug delivery, and cell manipulation. Fabrication process is based on electrochemical etching of n-type silicon in hydrofluoric acid (HF) solutions. Basic process flow and etching conditions that ensure a stable pore growth are described. These conditions also determine the geometry of the resulting microneedle structure. Microneedle arrays of different dimensions can be fabricated in a single run on the same wafer. In this work, microneedle arrays with pore diameters ranging from 2 to 5 µm, pore lengths from 30 to 140 µm and wall thicknesses in the range of 70–110 nm are reported.
Bittencours, C.; Llobet, E.; Ivanov, P.; Correig, X.; Vilanova, X.; Brezmes, J.; Hubalek, J.; Malysz, K.; Calderer, J. Sensors and actuators B. Chemical num. 97, p. 67-73 Data de publicació: 2004-01 Article en revista
Jiménez, C.; Moreno, L.; Haro, C.; Muñoz, X.; Florido, A.; Rivas, P.; Fernández, A.; Martín, P.; Bratov, A.; Domínguez, C. Sensors and actuators B. Chemical Vol. 91, num. 1-3, p. 103-108 Data de publicació: 2003-06 Article en revista
Arturo, O.; Marco, S.; Perera, A.; Teodor, S.; Pardo, A.; Samitier, J. Sensors and actuators B. Chemical Vol. 78, num. 1-3, p. 32-39 DOI: 10.1016/S0925-4005(01)00788-2 Data de publicació: 2001-08 Article en revista
An intelligent detector based on a hot-plate gas sensor and a digital signal processor (DSP) is presented. The work comprises sensor measurements and gas identification with a pattern recognition (PARC) system along with a systematic verification of both stages, thanks to clustering validity methods and performance tests. Commercial silicon micromachined tin-oxide sensors have been used to capture dynamic measurements modulating the sensor heater at different temperatures, waveforms and frequencies. Feature extraction is based on the spectral and transient analysis of the sensor output signals. The PARC systems are based on self-organizing maps (SOM) and recent variations of these well-known neural networks. The proposed hardware is in charge of the whole system: the sensor temperature modulation and signal processing.
Cané, C.; Götz, A.; Merlos, A.; Gràcia, I.; Errachid, A.; Losantos, P.; Lora-Tamayo, E. Sensors and actuators B. Chemical Vol. 1-3, num. 136-140, p. 35-36 DOI: 10.1016/S0925-4005(97)80043-3 Data de publicació: 1996-09-01 Article en revista
The fabrication of microsystems in which chemical measurements play a role make the on-chip combination of chemical sensors and signal processing circuitry highly desirable. Chemical sensors use sensitive layers which are not a part of MOS devices and in this sense, the determination of the best sensors and technological processes to achieve good integrated smart sensors is very important. In this paper a study of compatibility of ISFET chemical sensors and CMOS circuitry is presented for application to biomedical microsystems.