Examinando por Autor "Seidel, Helmut"

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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.
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.
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.