DSpace Community:http://hdl.handle.net/10261/322024-03-28T15:41:28Z2024-03-28T15:41:28ZHigh frequency venting of MEMS ultrasonic transducers and sensors: materials solutionsT.E.G. Álvarez-ArenasP. SalsoV. Genovéshttp://hdl.handle.net/10261/3474282024-02-23T13:53:49Z2024-02-19T10:15:44ZTítulo: High frequency venting of MEMS ultrasonic transducers and sensors: materials solutions
Autor: T.E.G. Álvarez-Arenas; P. Salso; V. Genovés
Resumen: . This paper introduces the concept of ultrasonic venting. Similar to acoustic vents,
ultrasonic vents refer to the aperture in air-coupled MEMS ultrasonic transducers (either PMUT
or CMUT) intended to allow the equalization of internal and external pressures, the transfer of
heat and the pass of ultrasonic waves, while impeding the penetration of fluids or particles that
can affect the transducer membrane. To that end, vents are covered with a porous membrane
whose properties are tuned to meet the afore mentioned requirements. The main difficulty in
ultrasonic venting, compared with acoustic venting, is that the required “transparency” to
ultrasonic waves is much more difficult to achieve. This involves two main problems as both
transmission loss and frequency distortion are much larger at ultrasonic frequencies than in the
audio range. The objectives of this paper are: to measure the response of acoustic venting
materials in the ultrasonic frequency range, to determine the usability of these materials in
ultrasonic vents, and to extract useful information for the design of efficient ultrasonic venting
materials. Transmission coefficient spectra of different acoustic venting materials is measured
in the frequency range 0.2 – 2.7 MHz. The origin of the ultrasonic losses and frequency distortion
are analysed as well as the role of mode conversion, internal interferences, modes interference,
etc. Results reveal that none of the acoustic venting materials analysed can be used in ultrasonic
venting applications, but the obtained knowledge about the response of these materials in the
ultrasonic frequency range permit to advance in the selection of successful candidate materials
for this application.2024-02-19T10:15:44ZTesting of battery separators: transducers and methods for air-coupled ultrasonic sensingPatricia SalsoVicente GenovésTomás Gómez Álvarez-Arenashttp://hdl.handle.net/10261/3474242024-02-23T13:53:44Z2024-02-19T10:05:36ZTítulo: Testing of battery separators: transducers and methods for air-coupled ultrasonic sensing
Autor: Patricia Salso; Vicente Genovés; Tomás Gómez Álvarez-Arenas
Resumen: Battery separator me3mbranes are thin polymeric microporous films placed between
battery electrodes. They are a key component that strongly affects both battery performance and
security and controlling its main properties is critical for the industry. In particular, the
manufacturing process demands tests that allow checking both the mechanical integrity
(porosity, thickness, pore size, etc.) of the materials and the consistency of these properties
during the construction of the batteries. The use of an air-coupled ultrasonic system is proposed
in this work. It is expected that this will make possible the non-destructive and quick testing of
these materials, in order to evaluate thickness, stiffness, pore distribution and pore size of the
separator. By means of three pairs of transducers, the modulus and phase of the transmission
coefficient was measured from 0.35 to 1.4 MHz in different materials. The measurements show
a clear modification of the film response produced by the presence of porosity. This suggests
that the transmission of ultrasonic waves in battery separators using air-coupled ultrasound may
have two contributions: one corresponds to the propagation though the solid part, the other
corresponds to propagation in the pores. The former allows to determine properties like film
thickness and elastic constants, while the latter allows to determine porosity and pore size and
pore tortuosity. This work set the basis for the development of a quality test for the in-line
inspection of these materials during their fabrication. The observed ultrasonic response in
microporous separators suggest the possibility to use low frequency air-coupled transducers with
limited sensitivity, where the use of MEM transducers at industrial scale can be advantageous2024-02-19T10:05:36ZUltrasonic Non-Linear Harmonic Generation In Air For Ultra-Wide Band Characterization Of Thin MembranesM. D. FariñasT. Gómez Álvarez-Arenashttp://hdl.handle.net/10261/3398302023-11-29T07:04:23Z2023-11-28T12:53:57ZTítulo: Ultrasonic Non-Linear Harmonic Generation In Air For Ultra-Wide Band Characterization Of Thin Membranes
Autor: M. D. Fariñas; T. Gómez Álvarez-Arenas
Resumen: The characterization and test of porous and
microporous thin layers using air-coupled ultrasound is
extremely attractive for quality control in different industries,
including air-filtration, Li-ion batteries, venting materials, etc.
This work explores the possibility of using low frequency and
narrowband transducers to generate harmonics in the air and
use them to characterize this type of materials. This can help to
avoid transducers limitations in terms of both center frequency
and frequency bandwidth. The proposed set up consist of low
frequency and narrowband excitation, harmonic generation in
the air and the use of a wide band receiver. The setup
configuration requirements are analyzed and described in
detailed in this study. A comparison of the proposed technique
results with linear conventional wideband air-coupled
measurements demonstrates the potential of the presented
method as a less demanding alternative in terms of equipment
needs and time required. This can be of special interest for the
deployment of solutions based on MEMs transducers, mainly
PMUTs, that show some limitations in the maximum frequency
and bandwidth when operating in air.2023-11-28T12:53:57ZLithium-Ion Batteries’ State-Of-Charge and Health Assessment by Non-Contact Ultrasound SpectroscopyL. FariñasM. M. SánchezT. G. Álvarez-Arenashttp://hdl.handle.net/10261/3398222023-11-29T07:04:20Z2023-11-28T12:32:52ZTítulo: Lithium-Ion Batteries’ State-Of-Charge and Health Assessment by Non-Contact Ultrasound Spectroscopy
Autor: L. Fariñas; M. M. Sánchez; T. G. Álvarez-Arenas
Resumen: Use of non-contact ultrasonic spectroscopy for
the characterization and test of Lithium-ion battery pouch cells
is investigated. Thickness resonances were excited and detected
throughout the discharge cycles. The results reveal that it is
possible to generate and measure thickness resonances in the
batteries and that these resonances are consistently sensitive to
the State-of-Charge of the cell as well as to temperature-induced
reversible alterations. Thickness and velocity were obtained
simultaneously from the measured transmission coefficients.
Results reveals that this technique is capable of detecting
mechanical changes in the batteries due to electromechanical
operation. Since this technique is completely contactless and
non-invasive, it can be applied both as quality test in production
or in operando, presenting great potential as an in-line
inspection tool for battery manufacturing applications.2023-11-28T12:32:52Z