Examinando por Autor "Toledo, Javier"

Mostrando 1 - 20 de 20

3D-Printed Liquid Cell Resonator with Piezoelectric Actuation for In-Line Density-Viscosity Measurements
(Sensors - Multidisciplinary Digital Publishing Institute (MDPI), 2021-11-18) Toledo, Javier; Ruiz-Díez, Víctor; Velasco, Jaime; Hernando-García, Jorge; Sánchez-Rojas, José Luis
The in-line monitoring of liquid properties, such as density and viscosity, is a key process in many industrial areas such as agro-food, automotive or biotechnology, requiring real-time automation, low-cost and miniaturization, while maintaining a level of accuracy and resolution comparable to benchtop instruments. In this paper, 3D-printed cuboid-shaped liquid cells featuring a rectangular vibrating plate in one of the sides, actuated by PZT piezoelectric layers, were designed, fabricated and tested. The device was resonantly excited in the 3rd-order roof tile-shaped vibration mode of the plate and validated as a density-viscosity sensor. Furthermore, conditioning circuits were designed to adapt the impedance of the resonator and to cancel parasitic effects. This allowed us to implement a phase-locked loop-based oscillator circuit whose oscillation frequency and voltage amplitude could be calibrated against density and viscosity of the liquid flowing through the cell. To demonstrate the performance, the sensor was calibrated with a set of artificial model solutions of grape must, representing stages of a wine fermentation process. Our results demonstrate the high potential of the low-cost sensor to detect the decrease in sugar and the increase in ethanol concentrations during a grape must fermentation, with a resolution of 10 µg/mL and 3 µPa·s as upper limits for the density and viscosity, respectively.
A Geometrical Study on the Roof Tile-Shaped Modes in AlN-Based Piezoelectric Microcantilevers as Viscosity–Density Sensors
(Sensors - Multidisciplinary Digital Publishing Institute (MDPI), 2019-02-06) Ruiz-Díez, Víctor; Toledo, Javier; Hernando-García, Jorge; Ababneh, Abdallah; Seidel, Helmut; Sánchez-Rojas, José Luis
Cantilever resonators based on the roof tile-shaped modes have recently demonstrated their suitability for liquid media monitoring applications. The early studies have shown that certain combinations of dimensions and order of the mode can maximize the Q-factor, what might suggest a competition between two mechanisms of losses with different geometrical dependence. To provide more insight, a comprehensive study of the Q-factor and the resonant frequency of these modes in microcantilever resonators with lengths and widths between 250 and 3000 µm and thicknesses between 10 and 60 µm is presented. These modes can be efficiently excited by a thin piezoelectric AlN film and a properly designed top electrode layout. The electrical and optical characterization of the resonators are performed in liquid media and then their performance is evaluated in terms of quality factor and resonant frequency. A quality factor as high as 140 was measured in isopropanol for a 1000 × 900 × 10 µm 3 cantilever oscillating in the 11th order roof tile-shaped mode at 4 MHz; density and viscosity resolutions of 10−6 g/mL and 10−4 mPa·s, respectively are estimated for a geometrically optimized cantilever resonating below 1 MHz.
Ammonia fuelled space electric propulsion systems using C12A7:e- electride as electron emitter
(Journal of Physics: Conference Series - Institute of Physics, 2023) Plaza, José Fabián; Toledo, Javier; Plaza, Ángel
Given the significant changes taking place in the geopolitical global situation, and the derived supply chain issues for some traditional electric propulsion propellants like xenon, alternative propellants issue is perceived as a strategic topic to tackle, and ammonia (NH3) is becoming one serious candidate. Ammonia is increasingly being investigated to extend green hydrogen use by overcoming the storage and transportation issues of hydrogen. Ammonia characteristics like its superior energy density and low temperature and/or pressure needs for storage (10 bar at 20°C for liquid ammonia), make it very valuable for simplified unexpensive energy storage and transportation, and these characteristics makes it also especially suitable for on-board spacecrafts electric propulsion purposes. Based on our research activities on ammonia generation and dissociation processes with C12A7:e- electride as catalyst, this work will describe the most relevant characteristics and properties associated to the advantages of using the cheap and abundant ammonia, and will also present and discuss the results of the first successful tests performed with ammonia as fuel for a C12A7:e- electride based neutralizer, including relevant endurance tests in operation conditions. Additionally, the dual application as propellant and on-board energy generation system of ammonia will also be discussed.
Application of quartz tuning forks and extensional microresonators for viscosity and density measurements in oil/fuel mixtures
(Springer Verlag, 2014-01-17) Toledo, Javier; Manzaneque, Tomás; Hernando-García, Jorge; Vázquez, Javier; Ababneh, Abdallah; Seidel, Helmut; Lapuerta, Magín; Sánchez-Rojas, José Luis
Real time monitoring of the physical properties of liquids is of great concern in the automotive industry. For example, tracking the viscosity of lubricating oils is of great importance because they are exposed to dilution with diesel fuel as result of late-injection processes, which are essential for regenerating diesel particulate filters. Here we describe two in-plane movement based resonators and their capability to assess oil dilution with diesel and biodiesel fuels. One of the resonators is a state-of-the-art micronsized AlN-based rectangular plate, actuated in the first extensional mode in the MHz range. The second resonator is a commercially available millimeter-sized quartz tuning fork, working at 32.7 kHz. Electrical impedance measurements were performed to characterize the performance of both resonators in various liquid media over a wide range of viscosities. These measurements were compared with the results obtained with low-cost electronic circuits also developed in this work. In order to track density and viscosity of different fluids we have measured two parameters by various techniques: the resonance frequency and the quality factor.
Bidirectional Linear Motion by Travelling Waves on Legged Piezoelectric Microfabricated Plates
(Micromachines - Multidisciplinary Digital Publishing Institute (MDPI), 2020-05-20) Ruiz-Díez, Víctor; Hernando-García, Jorge; Toledo, Javier; Ababneh, Abdallah; Seidel, Helmut; Sánchez-Rojas, José Luis
This paper reports the design, fabrication and performance of MEMS-based piezoelectric bidirectional conveyors featuring 3D printed legs, driven by linear travelling waves (TW). The structures consisted of an aluminium-nitride (AlN) piezoelectric film on top of millimetre-sized rectangular thin silicon bridges and two electrode patches. The position and size of the patches were analytically optimised for TW generation in three frequency ranges: 19, 112 and 420 kHz, by the proper combination of two contiguous flexural modes. After fabrication, the generated TW were characterized by means of Laser-Doppler vibrometry to obtain the relevant tables of merit, such as the standing wave ratio and the average amplitude. The experimental results agreed with the simulation, showing the generation of a TW with an amplitude as high as 6 nm/V and a standing wave ratio as low as 1.46 for a device working at 19.3 kHz. The applicability of the fabricated linear actuator device as a conveyor was investigated. Its kinetic performance was studied with sliders of different mass, being able to carry a 35 mg silicon slider, 18 times its weight, with 6 V of continuous sinusoidal excitation and a speed of 0.65 mm/s. A lighter slider, weighting only 3 mg, reached a mean speed of 1.7 mm/s at 6 V. In addition, by applying a burst sinusoidal excitation comprising 10 cycles, the TW generated in the bridge surface was able to move a 23 mg slider in discrete steps of 70 nm, in both directions, which is a promising result for a TW piezoelectric actuator of this size.
Calibration procedure for piezoelectric MEMS resonators to determine simultaneously density and viscosity of liquids
(Microsystem Technologies - Springer Nature, 2018-03) Toledo, Javier; Ruiz-Díez, Víctor; Pfusterschmied, Georg; Schmid, Ulrich; Sánchez-Rojas, José Luis
The main objective of this work is the assessment of a calibration method for piezoelectric MEMS resonators for simultaneous density and viscosity sensing. A device designed to resonate with the 2nd order out-of-plane modal vibration (13-mode) was immersed in several test liquids (i.e. D5, N10, N35, PAO8, olive oil, ester oil, DITA and N100). Two important parameters were estimated from the electrical impedance characterization: the quality factor and the resonant frequency. Once these two parameters are known, the viscosity and density of the liquids under test were determined following different calibration models. An advanced calibration model, based on a Taylor series of the hydrodynamic function, was established as a suitable method for determining the density and viscosity with the lowest calibration error. Our results demonstrate that the calibration coefficients, obtained in the calibration process, are valid in a temperature range between 20 and 40 °C in liquids with viscosities up to 300 mPa s. Furthermore, the estimated density and viscosity values with the MEMS resonator were compared to the values obtained with a commercial density–viscosity meter, reaching a mean calibration error in the best scenario of around 0.4% for the density and 2.8% for the viscosity
Comparison of in‑plane and out‑of‑plane piezoelectric microresonators for real‑time monitoring of engine oil contamination with diesel
(Microsystem Technologies-Micro-And Nanosystems-Information Storage And Processing Systems (Springer Verlag), 2016-01-20) Toledo, Javier; Manzaneque, Tomás; Ruiz-Díez, Víctor; Jiménez-Márquez, Francisco; Kucera, Martin; Pfusterschmied, Georg; Wistrela, Elisabeth; Schmid, Ulrich; Sánchez-Rojas, José Luis
Real-time monitoring of the physical properties of liquids, such as lubricants, is a very important issue for the automotive industry. For example, contamination of lubricating oil by diesel soot has a significant impact on engine wear. Resonant microstructures are regarded as a precise and compact solution for tracking the viscosity and density of lubricant oils. In this work, we report two different resonators for the monitoring of oil dilution with diesel fuel; one device was designed to vibrate in out of-plane modes (12-mode or 14-mode), while the other micro-plate was actuated in the first extensional in-plane mode. To determine from the measurements the resonance parameters of interest (resonance frequency and quality factor), an interface circuit was implemented and included within a closed-loop scheme. Two types of oscillator circuits were tested, a Phase-Locked Loop based on instrumentation and a more compact version based on discrete electronics, showing similar resolution. A model with fitting parameters was validated allowing for the determination of the viscosity and density of the fluids under test, for which only a small amount of test liquid, in the range of 0.5 ml, was required. Our results demonstrate the performance of the resonators in oils with viscosity up to 90 mPa s. For such viscosity, the quality factor measured at 25 °C was 7 for the 12-mode, 19 for the 14-mode and 16 for the extensional mode. The best resolution for both fluid material parameters was obtained in the 14-mode, showing 3.92 × 10−5 g/ml for the density and 1.27 × 10−1 mPa s for the viscosity, in pure lubricant oil SAE 0W30. Finally, the resonator with the best result (14-mode) was also tested in continuous-flow measurements, showing a resolution of 0.5 ppm of diesel contamination in a pure lubricant oil SAE 2.5 W.
Design and characterization of in-plane piezoelectric microactuators
(Actuators - Multidisciplinary Digital Publishing Institute (MDPI), 2017-06-03) Toledo, Javier; Ruiz-Díez, Víctor; Díaz, Alex; Ruiz, David; Donoso, Alberto; Bellido, José Carlos; Wistrela, Elisabeth; Kucera, Martin; Schmid, Ulrich; Hernando-García, Jorge; Sánchez-Rojas, José Luis
In this paper, two different piezoelectricmicroactuator designs are studied. The corresponding devices were designed for optimal in-plane displacements and different high flexibilities, proven by electrical and optical characterization. Both actuators presented two dominant vibrational modes in the frequency range below 1 MHz: an out-of-plane bending and an in-plane extensional mode. Nevertheless, the latter mode is the only one that allows the use of the device as a modal in-plane actuator. Finite ElementMethod (FEM) simulations confirmed that the displacement per applied voltage was superior for the low-stiffness actuator, which was also verified through optical measurements in a quasi-static analysis, obtaining a displacement per volt of 0.22 and 0.13 nm/V for the low-stiffness and high-stiffness actuator, respectively. In addition, electrical measurements were performed using an impedance analyzer which, in combination with the optical characterization in resonance, allowed the determination of the electromechanical and stiffness coefficients. The low-stiffness actuator exhibited a stiffness coefficient of 5 × 104 N/m, thus being more suitable as a modal actuator than the high-stiffness actuator with a stiffness of 2.5 × 105 N/m.
Flow-through sensor based on piezoelectric MEMS resonator for the in-line monitoring of wine fermentation
(Sensors and Actuators B: Chemical - Elsevier, 2017-07-17) Toledo, Javier; Ruiz-Díez, Víctor; Pfusterschmied, Georg; Schmid, Ulrich; Sánchez-Rojas, José Luis
tThe traditional procedure followed by winemakers for monitoring grape must fermentation is not auto-mated, has not enough accuracy or has only been tested in discrete must samples. In order to contributeto the automation and improvement of the wine fermentation process, we have designed an AlN-based piezoelectric microresonator, serving as a density sensor, resonantly excited in the 4th-order rooftile-shaped vibration mode. Furthermore, conditioning circuits were designed to convert the one-portimpedance of the resonator into a resonant two-port transfer function. This allowed us to design a PhaseLocked Loop-based oscillator circuit, implemented with a commercial lock-in amplifier with an oscillationfrequency determined by the resonance mode. We measured the fermentation kinetics by simultaneouslytracking the resonance frequency and the quality factor of the microresonator. The device was first cali-brated with an artificial model solution of grape must and then applied for the in-line monitoring of realgrape must fermentation. Our results demonstrate the high potential of MEMS resonators to detect thedecrease in sugar and the increase in ethanol concentrations during the grape must fermentation with aresolution of 1 mg/ml and 20 Pa s as upper limits for the density and viscosity, respectively.
Key design and operation factors for high performance of C12A7:e- based cathodes
(IOP Conference Series: Materials Science and Engineering, 2022) Post, Ángel; Plaza, José Fabián; Toledo, Javier; Zschätzsch, Daniel; Reitemeyer, Malina; Chen, Limei; Gurciullo, Antonio; Siegl, Andreas; J Klar, Peter; Lascombes, Paul
This work, based on an EU-funded project (NEMESIS), is summarising some of the results from the project activities on the research and development on electride-based cathode technology compatible with all kinds of electric propulsion (EP) systems requiring neutralization or electron emission. Further information describing in detail the performed tests and captured measurements can be found in the referenced documents of each section. Different cathode architectures and several emitter configurations with traditional and with alternative propellants are being developed and tested within the project, all of them using C12A7:e- electride material as thermionic electron source. Findings and conclusions derived from these multiple designs are allowing to figure out some of the key factors that determine the best performance of C12A7:e- electride based cathodes. In this work, a discussion of some of these key design and operation factors will be presented based both on the material characterization parameters, and on the performance tests carried out for the different cathode designs.
Measurement of the C12A7:e- thermionic emission enhancement due to photon exposure
(Journal of Physics: Conference Series - Institute of Physics, 2023) Toledo, Javier; Post, Ángel; Plaza, José Fabián
In this work, a test set-up device is designed, developed and manufactured to perform a direct measurement of the current emission enhancement that the photon absorption can bring to the thermionic emission in a Photon-Enhanced Thermionic Emission Device (PETED) where the C12A7:e- electride is used as the semiconductor due to its low work function value of 2.4 eV. Even though the measured thermionic emission starts at low operational temperatures, obtaining for example a current density emission of 5 mA/cm2 at 500 °C, there is barely an increase of 1% in the current emission when the device is exposed to a source of photons. This effect is mainly due to the presence of a dielectric layer at the material surface, which acts as a barrier, reduces the current enhancement effect from photon excitation, and drives to a limited efficiency of 27 μA/cm2/W.
Modelling and characterization of the roof tile-shaped modes of AlN-based cantilever resonators in liquid media
(Journal of Micromechanics and Microengineering, 2016-07-22) Ruiz-Díez, Víctor; Hernando-García, Jorge; Toledo, Javier; Manzaneque, Tomás; Kucera, Martin; Pfusterschmied, Georg; Schmid, Ulrich; Sánchez-Rojas, José Luis
In this work, roof tile-shaped modes of MEMS (micro electro-mechanical systems) cantilever resonators with various geometries and mode orders are analysed. These modes can be efficiently excited by a thin piezoelectric film and a properly designed top electrode. The electrical and optical characterization of the resonators are performed in liquid media and the device performance is evaluated in terms of quality factor, resonant frequency and motional conductance. A quality factor as high as 165 was measured in isopropanol for a cantilever oscillating in the seventh order roof tile-shaped mode at 2 MHz. To support the results of the experimental characterization, a 2D finite element method simulation model is presented and studied. An analytical model for the estimation of the motional conductance was also developed and validated with the experimental measurements.
Performance comparison of LaB6 and C12A7:e-emitters for space electric propulsion cathodes
(IOP Conference Series: Materials Science and Engineering, 2022) Toledo, Javier; Plaza, José Fabián; Post, Ángel; Zschätzsch, Daniel; Reitemeyer, Malina; Chen, Limei; Gurciullo, Antonio; Siegl, Andreas; J Klar, Peter; Lascombes, Paul; Seifert, Bernhard
This work, based on an EU-funded project, NEMESIS, is aiming at developing electride-based cathode technology which is compatible with all kinds of electric propulsion systems requiring neutralization. Its target is to demonstrate and validate the performance of a novel C12A7:e- electride material as electron emitter instead of traditional thermionic emitters such as lanthanum hexaboride, LaB6, or barium oxide, BaO. In this study, a fair comparison between LaB6 and C12A7:e- samples was performed both addressing pure material characterization parameters as well as comparing performance as cathodes under different architectures and operational conditions. In this case, a current/cathode power ratio around 3 mA/W was obtained when using the C12A7:e- sample in a plasma environment with Ar, which is approximately one order of magnitude higher compared to the LaB6 sample.
Piezoelectric actuators for tactile and elasticity sensing
(Actuators - Multidisciplinary Digital Publishing Institute (MDPI), 2020-03-19) Toledo, Javier; Ruiz-Díez, Víctor; Hernando-García, Jorge; Sánchez-Rojas, José Luis
Piezoelectric actuators have achieved remarkable progress in many fields, being able to generate forces or displacements to perform scanning, tuning, manipulating, tactile sensing or delivering functions. In this work, two piezoelectric PZT (lead zirconate titanate) bimorph actuators, with different tip contact materials, were applied as tactile sensors to estimate the modulus of elasticity, or Young's modulus, of low-stiffness materials. The actuators were chosen to work in resonance, taking advantage of a relatively low resonant frequency of the out-of-plane vibrational modes, associated with a convenient compliance, proven by optical and electrical characterization. Optical measurements performed with a scanning laser vibrometer confirmed that the displacement per applied voltage was around 437 nm/V for the resonator with the lower mass tip. In order to determine the modulus of elasticity of the sensed materials, the stiffness coefficient of the resonator was first calibrated against a force sensor, obtaining a value of 1565 ± 138 N/m. The actuators were mounted in a positioning stage to allow approximation and contact of the sensor tip with a set of target materials. Electrical measurements were performed using the resonator as part of an oscillator circuit, and the modulus of elasticity of the sample was derived from the contact resonant frequency curve of the cantilever-sample system. The resulting sensor is an effective, low-cost and nondestructive solution compared to atomic force microscopy (AFM) techniques. Materials with different modulus of elasticity were tested and the results compared to values reported in the literature.
Piezoelectric mems linear motor for nanopositioning applications
(Actuators - Multidisciplinary Digital Publishing Institute (MDPI), 2021-02-18) Ruiz-Díez, Víctor; Hernando-García, Jorge; Toledo, Javier; Ababneh, Abdallah; Seidel, Helmut; Sánchez-Rojas, José Luis
This paper reports the design, fabrication, and performance of piezoelectric bidirectional conveyors based on microelectromechanical systems (MEMS) and featuring 3D-printed legs in bridge resonators. The structures consisted of aluminum-nitride (AlN) piezoelectric film on top of millimeter-sized rectangular thin silicon bridges and two electrode patches. The position and size of the patches were analytically optimized for travelling or standing wave generation, while the addition of 3D-printed legs allowed for a controlled contact and amplified displacement, a further step into the manufacturing of efficient linear motors. Such hybrid devices have recently demonstrated the conveyance of sliders of several times the motor weight, with speeds of 1.7 mm/s by travelling waves generated at 6 V and 19.3 kHz. In this paper both travelling and standing wave motors are compared. By the optimization of various aspects of the device such as the vibrational modes, leg collocation and excitation signals, speeds as high as 35 mm/s, and payloads above 10 times the motor weight were demonstrated. The devices exhibited a promising positional resolution while actuated with only a few sinusoidal cycles in an open-loop configuration. Discrete steps as low as 70 nm were measured in the conveyance of 2-mg sliders.
Piezoelectric MEMS Resonators for Cigarette Particle Detection
(Micromachines - Multidisciplinary Digital Publishing Institute (MDPI), 2019-02-21) Toledo, Javier; Ruiz-Díez, Víctor; Bertke, Maik; Suryo Wasisto, Hutomo; Peiner, Erwin; Sánchez-Rojas, José Luis
In this work, we demonstrate the potential of a piezoelectric resonator for developing a low-cost sensor system to detect microscopic particles in real-time, which can be present in a wide variety of environments and workplaces. The sensor working principle is based on the resonance frequency shift caused by particles collected on the resonator surface. To test the sensor sensitivity obtained from mass-loading effects, an Aluminum Nitride-based piezoelectric resonator was exposed to cigarette particles in a sealed chamber. In order to determine the resonance parameters of interest, an interface circuit was implemented and included within both open-loop and closed-loop schemes for comparison. The system was capable of tracking the resonance frequency with a mass sensitivity of 8.8 Hz/ng. Although the tests shown here were proven by collecting particles from a cigarette, the results obtained in this application may have interest and can be extended towards other applications, such as monitoring of nanoparticles in a workplace environment.
Piezoelectric MEMS resonators for density and viscosity sensing in engine oil with diesel fuel
(IEEE 2015 Transducers - 18th International Conference on Solid-State Sensors, Actuators and Microsystems., 2015-08) Toledo, Javier; Manzaneque, Tomás; Ruiz-Díez, Víctor; Kucera, Martin; Pfusterschmied, Georg; Wistrela, Elisabeth; Steindl, Wolfgang; Schmid, Ulrich; Sánchez-Rojas, José Luis
This work demonstrates the potential of AlN-based resonators as on-line sensors for monitoring lubricant oil dilution with diesel. Two devices are compared, one actuated in the first extensional in-plane mode and the other in an out-of-plane mode (14-mode). Both devices are designed to feature high quality factor in liquid, and allow discriminating variations in density or viscosity in the medium. Sensor resolutions for these two variables are compared in lubricant oil SAE 2.5W, and the device with the best result (14-mode) was also tested in continuous-flow measurements, showing a resolution of 0.5 ppm of diesel contamination in this oil.
Piezoelectric MEMS resonators for monitoring grape must fermentation
(Journal of Physics: Conference Series - 27th Micromechanics and Microsystems Europe Workshop., 2016-11-11) Toledo, Javier; Jiménez-Márquez, Francisco; Úbeda, Juan; Ruiz-Díez, Víctor; Pfusterschmied, Georg; Schmid, Ulrich; Sánchez-Rojas, José Luis
The traditional procedure followed by winemakers for monitoring grape must fermentation is not automated, has not enough accuracy or has only been tested in discrete must samples. In order to contribute to the automation and improvement of the wine fermentation process, we have designed an AlN-based piezoelectric microresonator, serving as a density sensor and being excited in the 4th-order roof tile-shaped vibration mode. Furthermore, conditioning circuits were designed to convert the one-port impedance of the resonator into a resonant two-port transfer function. This allowed us to design a Phase Locked Loop-based oscillator circuit, implemented with a commercial lock-in amplifier with an oscillation frequency determined by the vibrating mode. We were capable of measuring the fermentation kinetics by both tracking the resonance frequency and by determining the quality factor measurements of the microresonator. Moreover, the resonator was calibrated with an artificial model solution of grape must and then applied for the monitoring of real grape must fermentation. Our results demonstrate the high potential of MEMS resonators to detect the decrease in sugar and the increase in ethanol concentrations during the grape must fermentation with a resolution of 100 μg/ml and a sensitivity of 0.16 Hz/μg/ml as upper limits.
Piezoelectric resonators and an oscillator circuit based on higher-order out-of-plane modes for density-viscosity measurements of liquids
(Journal of Micromechanics and Microengineering, 2016-07-22) Toledo, Javier; Manzaneque, Tomás; Ruiz-Díez, Víctor; Kucera, Martin; Pfusterschmied, Georg; Wistrela, Elisabeth; Schmid, Ulrich; Sánchez-Rojas, José Luis
We report the use of two AlN-based piezoelectric microresonators for the monitoring of density and viscosity of liquids and its application to detect lubricant oil dilution with diesel fuel. Two devices designed to resonate in the 4th-order roof tile-shaped vibration mode, but with two different anchor schemes, were fabricated and characterized. Interface circuits were designed to convert the one-port impedance into a resonant two-port transfer function. This allowed us to implement a phase locked loop (PLL)-based oscillator circuit based on the resonators, the interface circuit and a commercial lock-in amplifier. Our results demonstrate the performance of the resonators in fluids having viscosities up to 500 mPa·s. The performance of the sensors in terms of sensitivity and resolution are compared for both anchor configurations.
Potential of Piezoelectric MEMS Resonators for Grape Must Fermentation Monitoring
(Micromachines - Multidisciplinary Digital Publishing Institute (MDPI), 2017-06-26) Pfusterschmied, Georg; Toledo, Javier; Kucera, Martin; Steindl, Wolfgang; Zemann, Stefan; Ruiz-Díez, Víctor; Schneider, Michael; Bittner, Achim; Sánchez-Rojas, José Luis; Schmid, Ulrich
In this study grape must fermentation is monitored using a self-actuating/self-sensing piezoelectric micro-electromechanical system (MEMS) resonator. The sensor element is excited in an advanced roof tile-shaped vibration mode, which ensures high Q-factors in liquids (i.e., Q ~100 in isopropanol), precise resonance frequency analysis, and a fast measurement procedure. Two sets of artificial model solutions are prepared, representing an ordinary and a stuck/sluggish wine fermentation process. The precision and reusability of the sensor are shown using repetitive measurements (10 times), resulting in standard deviations of the measured resonance frequencies of ~0.1%, Q-factor of ~11%, and an electrical conductance peak height of ~12%, respectively. With the applied evaluation procedure, moderate standard deviations of ~1.1% with respect to density values are achieved. Based on these results, the presented sensor concept is capable to distinguish between ordinary and stuck wine fermentation, where the evolution of the wine density associated with the decrease in sugar and the increase in ethanol concentrations during fermentation processes causes a steady increase in the resonance frequency for an ordinary fermentation. Finally, the first test measurements in real grape must are presented, showing a similar trend in the resonance frequency compared to the results of an artificial solutions, thus proving that the presented sensor concept is a reliable and reusable platform for grape must fermentation monitoring.