Designing Vibrotactile Widgets with Printed Actuators and Sensors

Physical controls are fabricated through complicated assembly of parts requiring expensive machinery and are prone to mechanical wear. One solution is to embed controls directly in interactive surfaces, but the proprioceptive part of gestural interaction that makes physical controls discoverable and usable solely by hand gestures is lost and has to be compensated, by vibrotactile feedback for instance. Vibrotactile actuators face the same aforementioned issues as for physical controls. We propose printed vibrotactile actuators and sensors. They are printed on plastic sheets, with piezoelectric ink for actuation, and with silver ink for conductive elements, such as wires and capacitive sensors. These printed actuators and sensors make it possible to design vibrotactile widgets on curved surfaces, without complicated mechanical assembly

Silicon on Nothing Mems Electromechanical Resonator

The very significant growth of the wireless communication industry has spawned tremendous interest in the development of high performances radio frequencies (RF) components. Micro Electro Mechanical Systems (MEMS) are good candidates to allow reconfigurable RF functions such as filters, oscillators or antennas. This paper will focus on the MEMS electromechanical resonators which show interesting performances to replace SAW filters or quartz reference oscillators, allowing smaller integrated functions with lower power consumption. The resonant frequency depends on the material properties, such as Young's modulus and density, and on the movable mechanical structure dimensions (beam length defined by photolithography). Thus, it is possible to obtain multi frequencies resonators on a wafer. The resonator performance (frequency, quality factor) strongly depends on the environment, like moisture or pressure, which imply the need for a vacuum package. This paper will present first resonator mechanisms and mechanical behaviors followed by state of the art descriptions with applications and specifications overview. Then MEMS resonator developments at STMicroelectronics including FEM analysis, technological developments and characterization are detailed.Comment: Submitted on behalf of EDA Publishing Association (http://irevues.inist.fr/EDA-Publishing

Development and Characterization of a Piezoelectrically Actuated MEMS Digital Loudspeaker

International audienceThe MEMS digital loudspeaker consists of a set of acoustic transducers, called speaklets, arranged in a matrix and which operate in a binary manner by emitting short pulses of sound pressure. Using the principle of additivity of pressures in the air, it is possible to reconstruct an audible sound. MEMS technology is particularly well suited to produce the large number of speaklets needed for sound reconstruction quality while maintaining a reasonable size. This paper presents for the first time the modeling, realization and characterizations of a piezoelectric digital loudspeaker based on MEMS technology. Static, dynamic and acoustic measurements are performed and match closely with theoretical results

Caractérisation par acoustique picoseconde des propriétés mécaniques du PZT déposé en couches minces pour des applications MEMS

Thèse de doctorat en Micro et Nanotechnologies, Acoustique et Télécommunications, Université de Lille 1, 16 juinLes MEMS sont aujourd'hui une réalité économique et sont d'ores et déjà utilisés dans un grand nombre d'objets de notre quotidien. Ces composants peuvent utiliser un actionnement piézoélectrique, notamment à base de PZT déposé en couches minces, du fait de son fort coefficient piézoélectrique. Pour dimensionner au mieux et de manière prédictive ces MEMS à base de PZT, il est important de connaitre les propriétés mécaniques du PZT, matériau complexe. Nous avons utilisé l'acoustique picoseconde, technique qui permet de sonder la matière avec des ondes acoustiques générées par des impulsions laser ultra-courtes. Elle permet de transposer à l'échelle nanométrique le principe du sonar. Lors de cette thèse nous avons étudié le PZT en couches minces par acoustique picoseconde. Nous avons pu extraire le module d'Young et le coefficient de Poisson sans faire l'approximation de l'un ou de l'autre. Nous avons également étudié la relaxation des parois de domaines, en mettant en oeuvre des mesures d'acoustique picoseconde en fréquence. A l'aide des propriétés mécaniques du PZT, issues des mesures d'acoustique picoseconde, nous avons pu extraire le coefficient piézoélectrique par la comparaison de modèles et de mesures sur une poutre encastrée-libre avec un actionneur à base de PZT. Enfin, nous avons appliqué ces données d'entrée au dimensionnement de dalles haptiques utilisant des actionneurs PZT. Le très bon accord entre la caractérisation de ces dispositifs et les modèles mis en place prouve l'apport de l'acoustique picoseconde pour le dimensionnement de MEMS

Mechanical properties characterization of thin-film PZT for MEMS applications using picosecond ultrasonics

Les MEMS sont aujourd’hui une réalité économique et sont d’ores et déjà utilisés dans un grand nombre d’objets de notre quotidien. Ces composants peuvent utiliser un actionnement piézoélectrique, notamment à base de PZT déposé en couches minces, du fait de son fort coefficient piézoélectrique. Pour dimensionner au mieux et de manière prédictive ces MEMS à base de PZT, il est important de connaitre les propriétés mécaniques du PZT, matériau complexe. Nous avons utilisé l’acoustique picoseconde, technique qui permet de sonder la matière avec des ondes acoustiques générées par des impulsions laser ultra-courtes. Elle permet de transposer à l’échelle nanométrique le principe du sonar. Lors de cette thèse nous avons étudié le PZT en couches minces par acoustique picoseconde. Nous avons pu extraire le module d’Young et le coefficient de Poisson sans faire l’approximation de l’un ou de l’autre. Nous avons également étudié la relaxation des parois de domaines, en mettant en œuvre des mesures d’acoustique picoseconde en fréquence. A l’aide des propriétés mécaniques du PZT, issues des mesures d’acoustique picoseconde, nous avons pu extraire le coefficient piézoélectrique par la comparaison de modèles et de mesures sur une poutre encastrée-libre avec un actionneur à base de PZT. Enfin, nous avons appliqué ces données d’entrée au dimensionnement de dalles haptiques utilisant des actionneurs PZT. Le très bon accord entre la caractérisation de ces dispositifs et les modèles mis en place prouve l’apport de l’acoustique picoseconde pour le dimensionnement de MEMS.MEMS components are today an economic reality and are already used in many mass market applications. These devices can use a piezoelectric actuation, in particular based on thin-film PZT due to its high piezoelectric coefficient. To perform predictive design of high performances components based on PZT actuators, mechanical properties of the PZT are required. We used the picosecond ultrasonic technique which probes thin layers with high frequency acoustics waves generated by ultra-short laser pulses. It allows the transposition of the sonar principle at nanometric scale. During this PhD, we studied thin-film PZT using picosecond ultrasonics. We extracted both Young’s modulus and Poisson ratio without an approximation of one or the other. We also studied wall domain relaxation using picosecond ultrasonic measurement at various frequencies. Using PZT mechanical properties obtained from picosecond ultrasonics, we extracted the PZT piezoelectric coefficient, from the comparison between PZT-based cantilever measurement and numerical modeling. Finally, we applied these data for the design of haptic plates using thin-film PZT actuators. The good agreement between haptic plate measurements and modelization proves all the benefit of picosecond ultrasonics for MEMS design

Haut-parleur MEMS à grand déplacement hors plan

Contexte Le haut-parleur est un des derniers élément d’un smartphone n’ayant pas été adapté aux techniques de micro-fabrication. Poussé par la réduction de l’épaisseur des appareils portables, des dizaines de haut-parleurs micro- fabriqués ont été développés ces dernières années. Lorsque la taille d’un haut-parleur est réduite, le déplacement nécessaire à la génération d’une pression acoustique suffisante est significativement plus grand que dans le cas de haut-parleurs classiques. Il est donc nécessaire d’atteindre des déplacements hors plan importants pour le développement de micro haut- parleurs dont les performances permettent de rivaliser avec celles des haut- parleurs classiques. Analyse Ce papier décrit le design et le procédé de fabrication innovant d'un haut- parleur MEMS. Ce haut-parleur est construit à partir de deux wafers, l’un comportant la partie moteur, composée d’actionneurs piézoélectriques, et l’autre comportant la partie acoustique, composée d’un plaque rigide mobile. Les modèles non linéaires prenant en compte les divers aspects du haut- parleur, les spécificités du procédé de fabrication et les mesures préliminaires des performances de la partie moteur sont également présentées. Conclusion La simulation montre que ce design permet de dépasser les performances acoustiques des haut-parleurs MEMS de l'état de l'art, tout en gardant une bonne linéarité, nécessaire pour une reproduction fidèle du signal audio. Les démonstrateurs réalisés vont être caractérisés, et les résultats expérimentaux vont être comparés aux modèles

Piezoelectric Actuated Glass Plate for Liquid Density and Viscosity Measurement

This paper reports on a new system for liquid density and viscosity measurement based on a freely suspended rectangular vibrating plate actuated by piezoelectric ceramic (PZT) actuators. The Lamb mode used for these measurements allows us to infer both the density and viscosity in a larger range as compared to the existing gold-standard techniques of MEMS resonators. The combination of the measured resonance frequency and quality factor enables extraction of density and viscosity of the surrounding liquid. The system is calibrated while performing measurements in water glycerol solutions with a density range from 997 to 1264 kg/m3 and viscosity from 1.22 to 985 mPa·s, which is a larger dynamic range compared to existing mechanical resonators showing an upper limit of 700 mPa·s. The out-of-plane vibrating mode exhibits quality factor of 169, obtained in deionized water (1.22 mPa·s viscosity), and 93 for pure glycerol with a viscosity of 985 mPa·s. This Lamb wave resonating sensor can achieve measurement in fairly large viscosity media while keeping a quality factor superior to 90. Measurements performed on oil validate the use of the Lamb system. Oil density is evaluated at 939 kg/m3 and dynamic viscosity at 43 mPa·s which corresponds to our expected values. This shows the possibility of using the sensor outside of the calibration range

In-ear measurement of innovative piezoelectric MEMS loudspeaker

International audienceA growing interest for MEMS loudspeaker for in-ear applications has been observed in recent years, with encouraging results in terms of sound pressure level, distortion and form factor. MEMS loudspeakers based on thin film PZT are promising to replace advantageously the bulky loudspeakers that are currently used in small wearable devices. Reducing the size of loudspeakers and adapt them to micro-fabrication processes could allow to reduce further the power consumption and to integrate them in smaller devices, such as smart-watches and true wireless earbuds. In this paper we present the measurement result of the loudspeaker presented in an other paper and the comparison of the results with the simulation carried with a lumped element model and a finite element model presented in [5]. In the simulations performed with both lumped parameters and finite elements models, the loudspeaker produces a sound pressure level of more than 120 dBSPL down to 100 Hz. The response of the loudspeaker is measured using a G.R.A.S RA0045 ear-occluded coupler, following the International 60318-4 (IEC) standard. The back cavity of the loudspeaker is unloaded and the setup is placed inside an anechoic G.R.A.S chamber. An adapter is designed and 3D printed in order to adapt the moving plate of the loudspeaker to the input of the ear-occluded coupler. The Total Harmonic Distortion (THD), due to the complex nonlinear behavior of the thin film piezoelectric material used in the loudspeaker, is evaluated as well and is compared with the one simulated with the model described in [6]. The differences observed between the experimental results and the models are then explained, and ways of improving the models and the performance of the loudspeaker are discussed

High performance piezoelectric MEMS loudspeaker based on an innovative wafer bonding process

International audienceDespite a significant number of new structures in the past few years, MEMS loudspeaker still are not competitive in terms of performance compared to non-MEMS loudspeakers for free field applications. For industrial perspectives, a high sound pressure level on a wide frequency band is required, as well as a low total harmonic distortion. To widen the frequency range of MEMS loudspeakers, we propose to separate the actuating element from the radiating one, in order to separate design constraints to reach an optimal structure. In this paper, the lumped element model of the loudspeaker in presented, as well as the innovative manufacturing process. Finally, the computed frequency response is compared to the measured one. At the resonance, pressures as high as 110 $dBSPL$ at 1 kHz and at 10 mm are reported for an active surface of 36 mm$^2$, which is above the known state of the art for a loudspeaker with similar dimensions. Also, the flatness of the radiated sound pressure in a wide frequency range is closer to the ideal frequency response of loudspeakers than other MEMS loudspeakers, due to the piston mode of the moving rigid plate of the loudspeaker. The total harmonic distortion, mainly due to the nonlinearity of the piezoelectric transduction, is below 5% for reasonable sound pressure levels in the usable frequency band. The use of digital signal processing and of a dedicated packaging will allow our loudspeaker to advantageously replace the main or secondary one in smartphones

FEM modelling of Piezo-actuated Microswitches

International audienceThis article presents a study of microswitches with piezoelectric actuation. With the help of analysis modelling and FEM commercial software (ANSYS), we investigated the potentiality of AlN as piezoelectric actuator. Firstly, we compared AlN with PZT to actuate simple structures by bimorph effect as cantilever or clamped-clamped membrane. After this investigation, we focused on means to improve the deflection and the contact force of structures, by mechanical considerations, in case of an AlN actuation. This resulted in several designs of microswitches, with two different actuation mechanisms: bending or buckling. To go further, we evaluated some technological aspects as the influence of residual stresses and the shape of membrane on an AlN piezo-actuated structure