Categoría publications

User-friendly Love wave flow cell for biosensors

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Authors: M.I. Rocha-Gaso, J.V. García, L. El Fissi, L. Francis,  A. Arnau, Y. Jiménez, C. March, A. Montoya

Event: Biosensors 2012, 22 World Congress on Biosensors. Cancún, México (2012)

 

Love wave (LW) sensors have attracted a great deal of attention in the scientific community during the last decade, due to its high sensitivity in liquid media compared to traditional quartz crystal microbalance (QCM)-based sensors. However, one of the main issues when dealing with LW-based biosensors is the fluidic aspect, since the surface on top of the Interdigital transducers (IDTs) has to be isolated from liquids. A user-friendly flow cell for LW biosensors was fabricated and tested. The fabricated cell allows a fast and easy installation and replacement of the sensor. Friendly-usability and robustness are two central features of the fabricated LW flow cell. Mechanical, thermal, electrical and chemical requirements are considered. In order to test the cell, a LW immunosensor for the detection of pesticides, using carbaryl insecticide as a model analyte, was implemented. An AT-cut quartz Z propagating /SiO2 LW sensor with λ = 40 μm and 120 MHz center frequency was specifically designed and fabricated for the flow cell. The sensor does not need to be wire bonded, which is a great advantage over previous reported LW sensor setups. The sensitivity, specificity and reusability achieved with this LW immunosensor is discussed and compared to the same immunosensor carried out on a QCM-based technique.

 

Optimization of lateral field excited platform for liquid sensing applications

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

Journal: Sensors and actuators B: Chemical (2012)

 

Investigating the electrical sensitivity of lateral field excited resonators (LFE) we observed two characteristics to highly impact sensitivity. First, an increase of the piezoelectric coupling factor k enhances the viscosity measurement range. Higher coupling factors are provided by the use of new materials, namely lithium tantalite (LiTaO3) and lithium niobate (LiNbO3) with coupling factors of 0.43 and 0.91 respectively. Since the sensitivity to electrical load parameters is governed by relative permittivity of the resonator material itself, the sensitivity to electrical parameters is found to decrease for new materials. Second, an electrode pattern that reveals higher energy trapping in the center of crystal was investigated. Compared to common LFE pattern, a third electrode was introduced in center between bite wing electrodes. Finite element modeling in ANSYS© shows enhanced sensitivity to low relative permittivity in range from 1 to 8. We performed experiments to verify the simulation results. Although an increased frequency shift compared to common LFE resonators was not observed, significantly higher conductance amplitudes occurred, which enhances the measurement range to high viscosity liquids, too.

Development of a Mass Sensitive Quartz Crystal Microbalance (QCM)-Based DNA biosensor using a 50 MHz electronic oscillator circuit

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Authors: G. García-Martínez, E. Bustabad, H. Perrot, C. Gabrielli, B. Bucur, M. Lazerges, D. Rose. L. Rodríguez-Pardo, J. Fariña, C. Compère, A. Arnau

Journal: Sensors (2011)

This work deals with the design of a high sensitivity DNA sequence detector using a 50 MHz quartz crystal microbalance (QCM) electronic oscillator circuit. The oscillator circuitry is based on Miller topology, which is able to work in damping media. Calibration and experimental study of frequency noise are carried out, finding that the designed sensor has a resolution of 7.1 ng/cm2 in dynamic conditions (with circulation of liquid). Then the oscillator is proved as DNA biosensor. Results show that the system is able to detect the presence of complementary target DNAs in a solution with high selectivity and sensitivity. DNA target concentrations higher of 50 ng/mL can be detected.

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Frequency-shift vs phase-shift characterization of in-liquid quartz crystal microbalance applications

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

Journal: Review of Scientific Instruments (2011)

 

The improvement of sensitivity in quartz crystal microbalance (QCM) applications has been addressed in the last decades by increasing the sensor fundamental frequency, following the increment of the frequency/mass sensitivity with the square of frequency predicted by Sauerbrey. However, this sensitivity improvement has not been completely transferred in terms of resolution. The decrease of frequency stability due to the increase of the phase noise, particularly in oscillators, made impossible to reach the expected resolution. A new concept of sensor characterization at constant frequency has been recently proposed. The validation of the new concept is presented in this work. An immunosensor application for the detection of a low molecular weight contaminant, the insecticide carbaryl, has been chosen for the validation. An, in principle, improved version of a balanced-bridge oscillator is validated for its use in liquids, and applied for the frequency shift characterization of the QCM immunosensor application. The classical frequency shift characterization is compared with the new phase-shift characterization concept and system proposed.

Validation of a phase-mass characterization concept and interface for acoustic biosensors

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

Journal: Sensors (2011)

Acoustic wave resonator techniques are widely used in in-liquid biochemical applications. The main challenges remaining are the improvement of sensitivity and limit of detection, as well as multianalysis capabilities and reliability. The sensitivity improvement issue has been addressed by increasing the sensor frequency, using different techniques such as high fundamental frequency quartz crystal microbalances (QCMs), surface generated acoustic waves (SGAWs) and film bulk acoustic resonators (FBARs). However, this sensitivity improvement has not been completely matched in terms of limit of detection. The decrease on frequency stability due to the increase of the phase noise, particularly in oscillators, has made it impossible to increase the resolution. A new concept of sensor characterization at constant frequency has been recently proposed based on the phase/mass sensitivity equation: Δφ/Δm ≈ −1/mL, where mL is the liquid mass perturbed by the resonator. The validation of the new concept is presented in this article. An immunosensor application for the detection of a low molecular weight pollutant, the insecticide carbaryl, has been chosen as a validation model.

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Hearing What You Cannot See and Visualizing What You Hear: Interpreting Quartz Crystal Microbalance Data from Solvated Interfaces

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Authors: Ilya Reviakine, Diethelm Johannsmann and Ralf P. Richter

Journal: Analytical Chemistry, 2011

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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.