Categoría publications

Optimization of the lateral field excited platform for liquid sensing applications

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Authors: C. Peters, R. Fernández, R. Lucklum, J. Fochtmann, D. McCann, J. Vetelino, A. Arnau

Journal: Procedia Engineering (2010)

 

The Lateral Field Excited (LFE) platform is sensitive to mechanical and electrical property changes occurring in adjacent media. Using the LFE sensor responses have been analyzed for the piezoelectric resonator materials alpha-quartz, lithium tantalate (LiTaO3) and lithium niobate (LiNbO3). Since the impact of the mechanical  load parameters on piezoelectric resonators is governed by the piezoelectric coupling factor, LiTaO3 and LiNbO3  are well suitable for operation in highly viscous environments. This benefit is achieved at the cost of a reduced sensitivity to the mechanical and electrical properties of the medium. A second approach proposes a new 3-electrode configuration. The response of this LFE sensor design to low electric permittivity has been modeled using a novel approach to simulate the low permittivity boundary conditions. An enhanced sensitivity of the sensor has been achieved.

High frequency mass transfer responses with polyaniline modified electrodes by using new ac-electrogravimetry device

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Authors: R. Torres, Y. Jiménez, A. Arnau, C. Gabrielli, S. Joiret, H. Perrot, T.K.L. To, X. Wang

Journal: Electrochimica Acta (2010)

For many years, polyaniline films have appeared to be one of the most studied conducting polymers. At the same time, ac-electrogravimetry has been used as a powerful technique for different polymer films but in general for slow perturbation rates. Two reasons for that: on the one hand, high frequency mass transfer responses are not expected and on the other hand, the electronic interfaces dedicated for ac-electrogravimetry are not prepared to follow, without distortion, high rate frequency shifts, faster than a few hertz. This paper shows that high ionic transfer responses can be detected by using a new ac-electrogravimetry concept. The experiments conducted with PANI tried to verify whether high frequency responses in conducting polymers are possible or not. The main interest of the new device is to reach the high frequency values directly and to demonstrate an ionic transfer contribution at 1 kHz which was not predicted with old systems.

Surface Generated Acoustic Wave Biosensors for the detection of pathogens: a review

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Authors: M.I. Rocha, C. March, A. Montoya, A. Arnau

Journal: Sensors (2009)

This review presents a deep insight into the Surface Generated Acoustic Wave (SGAW) technology for biosensing applications, based on more than 40 years of technological and scientific developments. In the last 20 years, SGAWs have been attracting the attention of the biochemical scientific community, due to the fact that some of these devices – Shear Horizontal Surface Acoustic Wave (SH-SAW), Surface Transverse Wave (STW), Love Wave (LW), Flexural Plate Wave (FPW), Shear Horizontal Acoustic Plate Mode (SH-APM) and Layered Guided Acoustic Plate Mode (LG-APM) – have demonstrated a high sensitivity in the detection of biorelevant molecules in liquid media. In addition, complementary efforts to improve the sensing films have been done during these years. All these developments have been made with the aim of achieving, in a future, a highly sensitive, low cost, small size, multi-channel, portable, reliable and commercially established SGAW biosensor. A setup with these features could significantly contribute to future developments in the health, food and environmental industries. The second purpose of this work is to describe the state-of-the-art of SGAW biosensors for the detection of pathogens, being this topic an issue of extremely importance for the human health. Finally, the review discuses the commercial availability, trends and future challenges of the SGAW biosensors for such applications.

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A different point of view on the sensitivity of quartz crystal microbalance sensors

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Authors: A. Arnau, Y. Montagut, J.V. García, Y. Jiménez

Journal: Meas. Sci. Technol. 20 (2009)

In this paper, the sensitivity of a quartz crystal microbalance (QCM) sensor is analysed and discussed in terms of the phase change versus the surface mass change, instead of the classical sensitivity in terms of the resonant frequency change derived from the well-known Sauerbrey equation. The detection sensitivity derived from the Sauerbrey equation is a theoretical detection capability in terms of the frequency change versus the mass change, which increases with the square of frequency. However, when a specific application and measuring system are considered, the detection capability of the QCM sensor must be considered from a different point of view. A new equation is obtained, which quantifies the phase shift of a fixed frequency signal corresponding to the series resonant frequency of the sensor in a reference state versus a change in the coating mass, where ηq  is the loss viscosity of the unperturbed sensor and νq is the wave propagation speed in quartz, is a parameter which only depends on the physical parameters of the unperturbed resonator and fixes the maximum sensitivity of the sensor and mL = ρLδL/ 2,  where ρL  and δL are, respectively, the liquid density and the wave penetration depth of the wave in the liquid, is the equivalent surface mass density associated with the oscillatory movement of the surface of the sensor in contact with a fluid medium. This equation is an approximate equation around the series resonance frequency of the sensor. The simulation results for 10, 50 and 150 MHz resonance frequency QCM sensors probe its validity. A new electronic system is proposed for QCM biosensor applications based on the equation introduced.

A piezoelectric immunosensor for the determination of pesticide residues and metabolites in fruit juices

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Authors: C. March, J.J. Manclús, Y. Jiménez, A. Arnau, A. Montoya

Journal: Talanta (2008)

A quartz crystal microbalance (QCM) immunosensor was developed for the determination of the insecticide carbaryl and 3,5,6-trichloro-2-pyridinol (TCP), the main metabolite of the insecticide chlorpyrifos and of the herbicide triclopyr. The detection was based on a competitive conjugate-immobilized immunoassay format using monoclonal antibodies (MAbs). Hapten conjugates were covalently immobilized, via thioctic acid self-assembled monolayer (SAM), onto the gold electrode sensitive surface of the quartz crystal. This covalent immobilization allowed the reusability of the modified electrode surface for at least one hundred and fifty assays without significant loss of sensitivity. The piezoimmunosensor showed detection limits (analyte concentrations producing 10% inhibition of the maximum signal) of 11 and 7µg l-¹ for carbaryl and TCP, respectively. The sensitivity attained (I50 value) was around 30µg l-¹ for both compounds. Linear working ranges were 15–53µg l-¹for carbaryl and 13–83µg l-¹ for TCP. Each complete assay cycle took 20 min. The good sensitivity, specificity, and reusability achieved, together with the short response time, allowed the application of this immunosensor to the determination of carbaryl and TCP in fruits and vegetables at European regulatory levels, with high precision and accuracy.

Improved electronic interfaces for AT-cut quartz crystal microbalance sensors under variable damping and parallel capacitance conditions

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Authors: A. Arnau, J.V. García, Y. Jiménez, V. Ferrari, M. Ferrari

Journal: Review of Scientific Instruments, vol. 79 (2008)

A new configuration of automatic capacitance compensation ACC technique based on an oscillatorlike working interface, which permits the tracking of the series resonant frequency and the monitoring of the motional resistance and the parallel capacitance of a thickness-shear mode quartz crystal microbalance sensor, is introduced. The new configuration permits an easier calibration of the system which, in principle, improves the accuracy. Experimental results are reported with 9 and 10 MHz crystals in liquids with different parallel capacitances which demonstrate the effectiveness of the capacitance compensation. Some frequency deviations from the exact series resonant frequency, measured by an impedance analyzer, are explained by the specific nonideal behavior of the circuit components. A tentative approach is proposed to solve this problem that is also common to previous ACC systems.

Improved frequency/voltage converters for fast quartz crystal microbalance applications

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Authors: R. Torres, J.V. García, A. Arnau, H. Perrot, L. To Thi Kim, C. Gabrielli

Journal: Review of Scientific Instruments, vol. 79, (2008)

The monitoring of frequency changes in fast quartz crystal microbalance QCM applications is a real challenge in today’s instrumentation. In these applications, such as ac electrogravimetry, small frequency shifts, in the order of tens of hertz, around the resonance of the sensor can occur up to a frequency modulation of 1 kHz. These frequency changes have to be monitored very accurately both in magnitude and phase. Phase-locked loop techniques can be used for obtaining a high performance frequency/voltage converter which can provide reliable measurements. Sensitivity higher than 10 mV/ Hz, for a frequency shift resolution of 0.1 Hz, with very low distortion in tracking both the magnitude and phase of the frequency variations around the resonance frequency of the sensor are required specifications. Moreover, the resonance frequency can vary in a broad frequency range from 5 to 10 MHz in typical QCM sensors, which introduces an additional difficulty. A new frequency-voltage conversion system based on a double tuning analog-digital phase-locked loop is proposed. The reported electronic characterization and experimental results obtained with conducting polymers prove its reliability for ac-electrogravimetry measurements and, in general, for fast QCM applications.

A review of interface electronic systems for AT-cut Quartz Crystal Microbalance Applications in Liquids

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Authors: A. Arnau

Journal: Sensors: Special Issue: Piezolectric sensors for determination of analytes in solutions, 370-411 (2008)

 

From the first applications of AT-cut quartz crystals as sensors in solutions more than 20 years ago, the so-called quartz crystal microbalance (QCM) sensor is becoming into a good alternative analytical method in a great deal of applications such as biosensors, analysis of biomolecular interactions, study of bacterial adhesion at specific interfaces, pathogen and microorganism detection, study of polymer film-biomolecule or cell-substrate interactions, immunosensors and an extensive use in fluids and polymer characterization and electrochemical applications among others. The appropriate evaluation of this analytical method requires recognizing the different steps involved and to be conscious of their importance and limitations. The first step involved in a QCM system is the accurate and appropriate characterization of the sensor in relation to the specific application. The use of the piezoelectric sensor in contact with solutions strongly affects its behavior and appropriate electronic interfaces must be used for an adequate sensor characterization. Systems based on different principles and techniques have been implemented during the last 25 years. The interface selection for the specific application is important and its limitations must be known to be conscious of its suitability, and for avoiding the possible error propagation in the interpretation of results. This article presents a comprehensive overview of the different techniques used for AT-cut quartz crystal microbalance in insolution applications, which are based on the following principles: network or impedance analyzers, decay methods, oscillators and lock-in techniques. The electronic interfaces based on oscillators and phase-locked techniques are treated in detail, with the description of different configurations, since these techniques are the most used in applications for detection of analytes in solutions, and in those where a fast sensor response is necessary.

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Piezoelectric transducers and applications, Second Edition.

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piezoelectric transducers and applicationsAuthors: Arnau A., Brett C., Bittencourt, Ch., Calvo E., Canetti, R., Coelho, W., Ferrari V., Jiménez Y., Kanazawa K., Leija L., Luckmlum R., March, C., Montoya, A., Muñoz R., Negreira, C., Ocampo, A., Otero M., Perrot., Ramos A., San Emeterio J.L., Soares D., Sogorb T., Stipek S, Vera, A.

Published by: Springer-Verlag Berlin Heidelberg (2008).

Since the publication of the first edition, the richness of the study of piezoelectric transducers has resulted in a large number of studies dealing both with new understandings underlying the principles, with new technological advances in its applications and indeed with developing new areas of utility for these transducers. The motivations driving the publication of that first edition as described in its foreword (which follows) continues with increased validity. The value of a second edition to include these new developments has been prepared. During the interim, the contributors and their students have not only continued, but increased their mutual interactions resulting in an amazing energy and synergy which is revealed in this edition.

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Advanced electronic interface for the monitoring of AT Cut Quartz Crystal Resonators used as Acoustic Sensors in Fluid Media

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Authors: A. Arnau, J.V. García, Y. Jiménez, V. Ferrari, M. Ferrari

Event: 19th International Congress on Acoustics – ICA07. Madrid, september 2-7 (2007)

 

The classical quartz crystal microbalance (QCM) is no longer only a microbalance; it has got a place as an acoustic sensor in a broad range of applications such as: fluid physical characterization, viscoelastic study of polymers, charge transfer analysis in electrochemical processes, and detection of biological components in fluid media, among other applications. In this paper, the basic operation of an AT cut quartz crystal resonator is extended to the fluid environment. In these applications the resonator is submitted to a heavy load which strongly affects the sensor response, making especially difficult the characterization of the main sensor parameters. The problem associated with the electronic interfaces for sensor characterization is introduced along with a brief reviewing and some recent improvements. After this description, an improved electronic interface is introduced in detail. The design is an interface based on a phase locked loop system which permits an accurate monitoring of the series resonant frequency and the motional resistance of the quartz crystal resonator sensor. A continuous and automatic compensation of the sensor parallel capacitance makes this possible. The report of experimental results shows the benefit of the new system, especially for heavy load QCM applications.

Read more about this work here.