Examinando por Autor "Schmid, Ulrich"

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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.
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.
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.