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[show abstract]
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ABSTRACT: In this paper, we present an array of biosensors for vapour phase detection of odorant molecules based on surface acoustic wave (SAW) resonators coated with odorant-binding proteins (OBPs). For the first time, the sensing capabilities of three different OBPs, as sensitive layers for SAW devices, are studied and compared. The SAW biosensor array is composed of three SAW devices coated by the droplet method with the wild-type OBP from cow (wtbOBP), a double mutant of the OBP from cow (dmbOBP) and the wild-type OBP from pig (wtpOBP). An uncoated device is used to compensate the variations of the environmental parameters. The SAW devices consist of two-port resonators fabricated on quartz (ST-cut, x propagation) with electrodes made of aluminium covered with a thin gold film (2nm thick). The obtained surface densities of OBP layers are between 1.18×10(-6)kg/m(2) and 2.31×10(-6)kg/m(2) and were calculated measuring the resonant frequency shift of the SAW devices after the coating. The SAW biosensor array was tested in nitrogen upon exposure to vapours of R-(-)-1-octen-3-ol (octenol), in the range of concentration between 13 and 61ppm, and R-(-)-carvone (carvone), in the range between 9 and 80ppm. The highest sensitivity for detection of octenol (25.9Hz/ppm) was obtained using the wtpOBP-based SAW biosensor, while the highest sensitivity for detection of carvone (9.2Hz/ppm) was obtained using the dmbOBP-based SAW biosensor.
Biosensors & bioelectronics 08/2012; · 5.43 Impact Factor
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ABSTRACT: This paper presents a comparative study of polymer pixel on sensors obtained by Laser Induced Forward Transfer (LIFT) assisted
by a triazene polymer as Dynamic Release Layer (DRL). Polyisobutylene (PIB) was selected as model for chemoselective polymers
which could be used as hydrogen-bond acidic polymer for vapor sensors.
PIB films deposited on fused silica, respectively, on triazene polymer coated fused silica substrates were used as targets.
Both targets were prepared by Matrix Assisted Pulsed Laser Evaporation (MAPLE). The parameters related to a regular, well-defined
transfer were analyzed and compared for the substrates with and without the DRL. The morphological characterization of the
transferred PIB was performed by Atomic Force Microscopy (AFM), Optical Microscopy, and Scanning Electron Microscopy (SEM).
It was found that a minimal thickness of the dynamic release layer, i.e. 100 nm is required to protect the sensitive PIB polymer
in a clean laser transfer process.
Applied Physics A 04/2012; 101(2):429-434. · 1.63 Impact Factor
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ABSTRACT: This paper presents polymer pixel printing for applications in chemoselective sensors where nanosecond laser direct transfer
methods, with a triazene polymer (TP) acting as a Dynamic Release Layer (DRL), are used. A systematic study of laser fluence,
donor film morphology and both single- and multiple-pixel deposition were optimized with the final goal to obtain continuous
pixels of sensitive polymers, polyethylenimine (PEI) and polyisobutylene (PIB), on SAW surfaces. Morphology characterization
after the laser transfer has been performed by Optical Microscopy and Scanning Electron Microscopy (SEM). The responses of
the coated transducers were measured after deposition with different laser fluences and it was found that a fluence under
625 mJ/cm2 was required in order to prevent damage of the interdigital transducers (IDT) of the sensor devices. The sensitivity of the
polymer coated devices to acetone concentrations gives an indication that LIFT can be used for printing sensitive polymer
pixels onto transducer devices.
Applied Physics A 04/2012; 101(3):559-565. · 1.63 Impact Factor
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ABSTRACT: An electroacoustic micro-device based on the propagation of guided acoustic Lamb waves in AlN/Al plate is described. The AlN thin film is deposited by sputtering technique, optimized to achieve a high degree of orientation (rocking curve full-width at half-maximum ¿ 3.5°) of the c-axis perpendicular to the plate surface. The AlN plate is micromachined using anisotropic reactive ion etching (RIE), followed by isotropic RIE to remove the silicon underlayer. Simulation results for the dispersion phase velocity curves and the electromechanical coupling coefficient (K<sup>2</sup>) are obtained by the matrix method and by the finite element method and compared with experimental data. A delay line is implemented on the structure and tested for the propagation of the first symmetrical Lamb mode (s<sub>0</sub>) at the frequency of 1.22 GHz. Measurements have shown that the structure is suitable for implementation of arrays of electroacoustic devices on a single chip for application to both sensing devices and signal processing systems.
IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control 06/2010; · 1.69 Impact Factor
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ABSTRACT: Laser-induced forward transfer (LIFT) using a triazene polymer as dynamic release layer was used for the transfer of polyethyleneimine (PEI) pixels for microsensors applications. A XeCl laser was used to transfer the PEI pixels from a thin film coated onto the triazene layer. The PEI films were either in direct contact with the receiver or a gap was maintained between the donor film and the receiver. An optimization of the process was carried out by changing the laser fluences, the ratio between the thickness of the PEI and of the triazene layer, and the transfer distance. Well-defined, regular PEI pixels were obtained on the receiver. The morphology of the patterns was characterized using optical microscopy and scanning electron microscopy (SEM). The transfer onto surface acoustic wave (SAW) devices suggests that LIFT is a promising technique for the fabrication of microsensors with polymers as active layer.
Sensor Letters 05/2010; 8(3):436-440. · 0.82 Impact Factor
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[show abstract]
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ABSTRACT: Abstract This paper presents polymer pixel printing for applications in chemoselective sensors where nanosecond laser direct transfer methods, with a triazene polymer (TP) acting as a Dynamic Release Layer (DRL), are used. A systematic study of laser fluence, donor film morphology and both single- and multiple-pixel deposition were optimized with the final goal to obtain continuous pixels of sensitive polymers, polyethylenimine (PEI) and polyisobutylene (PIB), on SAW surfaces. Morphology characterization after the laser transfer has been performed by Optical Microscopy and Scanning Electron Microscopy (SEM). The responses of the coated transducers were measured after deposition with different laser fluences and it was found that a fluence under 625 mJ/cm2 was required in order to prevent damage of the interdigital transducers (IDT) of the sensor devices. The sensitivity of the polymer coated devices to acetone concentrations gives an indication that LIFT can be used for printing sensitive polymer pixels onto transducer devices.
Applied Physics A: Materials Science & Processing. 01/2010; 101(3):559-565.
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ABSTRACT: In this work we present a Surface Acoustic Wave (SAW) biosensor system based on a recombinant bovine odorant-binding protein
(bOBP) suitable to detect boletus odorant.
To optimize the bOBP’s deposition method on the interdigital transducers (IDTs), the protein was deposited by means of droplet
method on the surface of a 155 MHz 2-port SAW resonator on ST-cut quartz. In order to promote the protein adhesion, IDTs were
made of thin gold film. The frequency shift of the resonator, after deposition, shows the presence of the protein on the IDT’s
surface. By using two identical 2-ports SAW resonators, operating at 392 MHz and exploiting gold/aluminum multilayered interdigital
electrodes, a differential configuration was implemented. In this way, common mode parasitic effects, such as temperature
variations have been reduced. The SAW resonators were used as frequency control element in a Pierce oscillator. The differential
frequency shift, due to the SAW velocity changes as consequence of odorant concentration, was measured, showing a resolution
of 44 ppb and a sensitivity of 314 Hz/ppm.
12/2009: pages 201-205;
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ABSTRACT: It was demonstrated in, that the use of compound matrices in the matrix formalism makes it possible to calculate acoustic mode velocities in a layered structure with thick film layers and is an useful tool to derive the analytic expressions for the acoustic mode propagation. The advantages, as well as the weak points related to the use of compound matrices in matrix methods of solutions of acoustic equations in comparison to their initial matrices are discussed, when applied to calculations of SAW and PSAW propagation in layered structures, exploiting thick films. Using an ldquoimaginablerdquo layered structure consisting of a thick isotropic diamond film on the isotropic diamond substrate, we illustrate and compare an ldquoexponentialrdquo unstable algorithm resulting by the use of initial matrices and the stable one calculated using their compound matrices. We report a number of compound matrix properties that are required for their implementation for acoustic wave analysis. Results of the calculations performed exploiting the initial matrices and their compound ones are discussed and compared for the of SAW and PSAW propagation along a layered structure: an AlN piezoelectric film deposited on a thick isotropic diamond layer, grown, in turn, on an isotropic polycrystal Si. Calculated results obtained for this structure and the layered structure with crystal Si substrate are discussed.
Ultrasonics Symposium, 2008. IUS 2008. IEEE; 12/2008
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ABSTRACT: In this paper we present recent results on fabrication of SAW devices on AlN/single-crystal diamond. The AlN thin film was deposited by sputtering technique, optimized to achieve an high degree of orientation value of the c-axis perpendicular to the plate surface (rocking curve FWHM ap 3.5deg), while the single-crystal diamond was grown by Microwave Plasma Chemical Vapor Deposition (MWPECVD) on High Pressure High Temperature (HPHT) diamond substrate. SAW propagation on the structure has been theoretically investigated and experimentally verified by implementing both delay-lines and 1-port resonators at different normalized AlN thickness (h/lambda). Very good accordance is obtained between evaluated phase velocity dispersion curves and measured values. Frequency responses show low insertion losses and rather high Q factors, respectively, for delay-lines and resonators. Pseudo-SAW modes are also observed and reported.
Ultrasonics Symposium, 2008. IUS 2008. IEEE; 12/2008
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ABSTRACT: In this work we present a pressure sensor based on surface acoustic waves (SAWs) resonators and operating in the pressure range from 0 bar to 3 bar. The achieved high resolution values (3.5 Pa), are obtained making use of 2-ports SAW resonators working at approximately 393 MHz on a quartz membrane. The membrane deformations under the hydrostatic pressure, have been studied by finite element methods (FEM), using the elastic constants of the anisotropic ST-cut quartz and considering vacuum as reference pressure on the other side of the membrane. The implemented sensor is an hybrid structure where the quartz membrane is placed between two glass ceramic elements; the first to implement an hermetically closed cavity, the other to define the diaphragm. A differential configuration has been designed to reduce parasitic phenomena due to temperature variations. The response curve of the sensor is reported.
Sensors, 2008 IEEE; 11/2008
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ABSTRACT: A thin-film bulk acoustic resonator (TFBAR) based on a vibrating membrane of AlN/Si<sub>3</sub>N<sub>4</sub> has been fabricated onto a silicon substrate and functionally characterized as gas sensor at a resonating frequency of 1.045 GHz. This novel TFBAR-based gas sensor has been functionalized by a sensing nanocomposite layer, prepared by a Langmuir-Blodgett (LB) technique, of single-walled carbon nanotubes (SWCNTs) embedded in a host matrix of organic material of cadmium arachidate. High-performance gas detection at room temperature of a SWCNT-coated TFBAR sensor has been reported. The sensing device exhibits high sensitivity (e.g., acetone: 12 kHz/ppm; ethylacetate: 17.3 kHz/ppm), fast response (within 2-3 min), slow reversibility (within 1 h), and good repeatability (les 5% variation) of response toward tested organic vapors of acetone, ethylacetate, and toluene.
IEEE Transactions on Electron Devices 06/2008; · 2.32 Impact Factor
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ABSTRACT: An electro-acoustic micro-device based on the propagation of guided acoustic Lamb-waves in aluminum nitride (AlN) free strip is described. The AlN thin film was deposited by sputtering technique, optimized to achieve an high degree of orientation (rocking curve FWHM ~ 3.5deg) of the c-axis perpendicular to the plate surface. The AlN beam was micro- machined using anisotropic reactive ion etching (RIE) technique, followed by an isotropic RIE process to remove the silicon underlayer. Simulation results obtained for the dispersion phase velocity curves and the electromechanical coupling coefficient (K<sup>-2</sup>), are reported. Finally, delay-lines were implemented on the structure and tested for the propagation of the first symmetrical Lamb mode (SO) at the frequency of 1.23 GHz. Measurements are in good accordance with theoretical predictions and show how the structure is suitable for arrays integration of electro- acoustic devices on a single chip for applications to sensing devices and signal processing systems.
Ultrasonics Symposium, 2007. IEEE; 12/2007
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ABSTRACT: We demonstrate the successful operation of a chemical microsensor based on thin film bulk acoustic resonator (TFBAR) for organic vapor detection at room temperature. The TFBAR consists of a vibrating membrane of AlN/Si<sub>3</sub>N<sub>4</sub> fabricated on silicon substrate and resonating at the frequency of 1.045 GHz. Using a nanocomposite layer based on Single-Walled Carbon Nanotubes (SWCNTs) and prepared by the Langmuir-Blodgett technique onto the TFBAR device as highly-sensitive nanomaterial, the sensing performance of TFBAR sensor has been evaluated both as a passive device by a network analyzer with phase and insertion loss responses, and as oscillator with frequency response. The vapor sensing characteristics of SWCNTs-based TFBAR sensor are presented illustrating interesting results.
Sensors, 2007 IEEE; 11/2007
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ABSTRACT: An electroacoustic chemical sensor based on thin-film bulk acoustic wave resonators (TFBAR) is presented. It operates on the same principle of the well-known quartz crystal micro-balance, at an operation frequency extended up to several GHz. The larger output signal, associated to the higher operation frequency, is a condition to improve the device sensitivity. TFBARs have been implemented on (001) Si wafers, using Si <sub>3</sub> N <sub>4</sub>/ Al N membranes, obtained by anisotropic etching of Si. Time response and calibration curves have been tested on TFBAR sensors exploiting two different chemically interactive membranes: Pd and Co-tetra-phenyl-porphyrin, both deposited in the form of thin-films by thermal evaporation. Measurements performed upon exposure to H <sub>2</sub> , CO, and ethanol have shown the ability of the device to detect low concentrations of the analyte with a fast and repeatable response.
Applied Physics Letters 11/2005; · 3.84 Impact Factor
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Ultrasonics Symposium, 2005 IEEE; 10/2005
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ABSTRACT: Diamond and AlN are, respectively, the nonpiezoelectric and the piezoelectric materials showing the highest acoustic velocities. Consequently, pseudo-surface-acoustic waves (PSAWs) in AlN / diamond structures exhibit the highest surface wave velocities among all known layered structures. Phase velocity dispersion curves and attenuation for PSAW propagating along this structure have been calculated for different electrical boundary conditions. An experimental delay line, designed to operate at low PSAW attenuation conditions, as predicted by theoretical results, has been implemented and tested. A good accordance between experimental results and theoretical predictions was found. It is expected that devices based on PSAW propagation in AlN / diamond structures are suitable to operate at frequencies several times higher than those of available devices, at a given linewidth resolution limit in the transducers technology.
Applied Physics Letters 08/2005; · 3.84 Impact Factor
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ABSTRACT: In this work we present preliminary results on surface acoustic waves (SAW) chemical sensors based on a new AlN/diamond/Si multilayered structure. The high SAW velocity in diamond allows it to operate at higher frequencies at moderate interdigital transducer (IDT) line-width resolution in order to increase the sensor output signals, with the aim to increase the sensor sensitivity. Aluminium nitride has been chosen as piezoelectric layer because of its high SAW velocity together with excellent electrical, mechanical and chemical properties. The SAW phase velocity in the experimented structure is 10716 m/s for the Sezawa mode, more than three times that in ST-cut quartz. Both SAW delay line and 1-port resonator have been implemented and tested, under the following propagation conditions: acoustic wavelength λ=8 μm, normalized AlN film thickness h/λ=0.225, operation frequency f≅1.35 GHz. The thickness of the diamond layer (22 μm) is such that it can be considered as a semi-infinite substrate. The two test structures have been coated by thermal evaporation with a sensible thin (10 nm) layer of Co-tetra-phenyl-porphyrin which allowed us to detect small concentrations of ethanol and CO.
Sensors, 2004. Proceedings of IEEE; 11/2004
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ABSTRACT: A novel electro-acoustic chemical sensor, based on a TFBAR, is presented. The principle of operation is the same as the well known quartz crystal micro-balance, where the frequency of operation is extended from the limit of a few tens of MHz to several GHz. The larger sensor output signals, associated with higher frequency operation, is a condition used to develop devices with improved sensitivity. TFBARs have been implemented on [001] Si wafers, using Si<sub>3</sub>N<sub>4</sub>/AlN membranes, obtained by anisotropic chemical etching from the back side of the Si substrate. The performance of the TFBAR sensor has been tested using a thin Pd chemical interactive membrane deposited on the etched side of the membrane and exposed to different concentrations of hydrogen in nitrogen. Time response upon different cycles of H<sub>2</sub> adsorption and desorption are reported together with the sensor calibration curve. The operation frequency of the device, in the GHz range, allows it to obtain large responses. The device is robust in construction and miniaturized in size. Time stability, repeatability and sensitivity have been tested and reported.
Ultrasonics Symposium, 2004 IEEE; 09/2004
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[show abstract]
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ABSTRACT: Diamond-like-carbon (DLC) films are very attractive for SAW devices applications because of their high SAW velocity, which can allow high frequency operation at moderate line-width resolution. Use of AlN as piezoelectric layer on DLC is also attractive because of its high SAW velocity: the highest among all piezoelectric materials, together with its excellent electrical, mechanical and chemical properties. The problem arising in the growth of AlN films on DLC have prevented, up to now, the use of this materials combination. In this paper we report our recent results on the growth of highly oriented, low stressed AlN films on DLC. SAWs propagation on AIN/DLC has been theoretically investigated together with the electromechanical coupling for both the Rayleigh and Sezawa modes. The theoretical calculations show how high SAW velocities are achievable with good coupling efficiencies. Under proper conditions very large piezoelectric couplings are predicted k<sup>2</sup> = 2.2 and 4 for the Rayleigh and Sezawa wave, respectively, comparable to those observed in strongly piezoelectric single crystal such as LiNbO<sub>3</sub>, but with SAW velocities approximately twice. Experiments performed on AIN/DLC/Si SAW test devices have shown a good agreement between experimental results and theoretical predictions and demonstrate the feasibility of SAW devices based on this technology.
Ultrasonics, 2003 IEEE Symposium on; 11/2003
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[show abstract]
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ABSTRACT: The relative changes in the phase velocity (Δv<sub>n</sub>/v<sub>n</sub>) of Lamb and SH modes, propagating in ST-cut quartz plates, along and perpendicular to the x direction respectively, to changes in the density, elastic moduli: temperature and thickness of the plate as well as mass, elastic, electric loading of the surface have been investigated for the different modes. It is shown how some of these changes do not affect the modes at all, others affect the modes of equal amounts, and finally some of them modify the velocity of the modes of amounts that depend on the mode family (SH or Lamb) and order n. This dependence on the order mode is smooth for the SH-one and non-smooth for the Lamb counterpart. On the basis of these properties a novel single channel sensor for multi-component analysis has been developed and tested using humid air as an example. Using different modes of one or of the two families, the sensor consists of one or two pairs of interdigital transducers (IDTs) and operates as an array of sensors with different response and calibration curves at the different frequencies.
Ultrasonics Symposium, 2002. Proceedings. 2002 IEEE; 11/2002
