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Wireless gas sensing based on a passive piezoelectric resonant sensor array through near-field induction

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Wireless gas sensing based on a passive piezoelectric resonant sensor array through near-field induction

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Abstract

We developed a wireless and passive piezoelectric resonant sensor for contimuous volatile organic compound detection. An equivalent circuit is proposed to model the sensing system, and Lamb wave resonators are adopted to demonstrate the wireless interrogation achieved by near-field inductive coupling. The wireless sensing system is employed to monitor the ethanol vapor concentration, and the sensitivity of the wireless sensor barely degrades compared to that of the wired one. Further, we simultaneously and wirelessly tracked several resonance frequencies of a monolithic sensor array, which demonstrates its potential for high-throughput and real-time point-of-care test. Published by AIP Publishing.

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... Les ondes de Lamb agissent sur toute l'épaisseur d'un matériau selon deux modes, le mode symétrique et le mode antisymétrique (Figure I.9). Les épaisseurs mises en jeu sont de l'ordre de grandeur des longueurs d'ondes voire plus petites [61,65]. Les ondes de Lamb sont notamment utilisées pour le contrôle non destructif par ultrasons [66]. ...
... Les ondes de Lamb sont notamment utilisées pour le contrôle non destructif par ultrasons [66]. Ce type d'onde se retrouve dans les MEMS de type FBAR (Film Bulk Acoustic wave Resonator) et est exploité dans des capteurs de gaz [67], d'humidité [65] et de particules [68,69] [72,75] ou électromagnétiques [72,76]. La récupération du signal de vibration peut être faite par voie piézorésistive [70,7274], piézoélectrique [68,72,77], capacitive [72,75] ou encore optique [71,72,76,78]. ...
Thesis
Les particules fines ont un impact réel sur la qualité de vie et la santé de millions de personnes dans les grandes zones urbaines, notamment en Asie. Pour les détecter et quantifier leur concentration, les capteurs de particules optiques sont les plus couramment étudiés, mais restent relativement chers et volumineux. Les transducteurs MEMS micropoutres sont largement utilisés pour des applications gravimétriques, pour la détection de particules ou de gaz, ce qui requiert des sensibilités massiques (Sm) élevées et des limites de détection (LOD) basses. Pour cela les micropoutres les plus adaptées sont celles ayant des fréquences de résonance (f0) et facteurs de qualité (Q) élevés, avec de faibles bruits de mesure et des masses faibles. Les micropoutres silicium sont couramment utilisées en tant que capteurs gravimétriques et sont de sérieux candidats pour répondre aux caractéristiques souhaitées. Cependant, la sérigraphie a le potentiel pour une fabrication moins chère, plus rapide et aussi à grande échelle. Pour ces micropoutres, l'actionnement et la lecture de f0 sont possibles par effet piézoélectrique. Bien qu'il existe des solutions inorganiques prometteuses sans plomb, les céramiques de titano-zirconate de plomb (PZT) possèdent encore les meilleures propriétés parmi les matériaux piézoélectriques. Des micropoutres fabriquées en technologie hybride couches épaisses sérigraphiées, à actionnement et lecture piézoélectriques intégrés, libérées à l'aide d'une couche sacrificielle polyester et avec co-cuisson de toutes les couches pour leurs libérations sont présentées ici. Différentes géométries ont été testées de 1 mm à 2 mm de large et de 1 mm à 8 mm de long, pour une épaisseur d'environ 100 μm. Une masse volumique ρ PZT = 7200 kg/m³ a été obtenue (≈ 93%ρ PZT massif). Enfin, avec une micropoutre 1×2×0,1 mm³, une sensibilité Sm ≈ 85 Hz/μm et une LOD de 70 ng ont été trouvées, permettant des applications en détection de particules.
... Taking the advantage of small size, long lifetime and no physical connection, the passive wireless sensor is essential to many industrial and medical applications [1] including intraocular eye pressure testing [2] in medical sensing, tire pressure monitoring [3] in automotive applications and pressure sensing at high temperature [4]. Recently, inductor-capacitor (LC) passive wireless sensors [5] have been proposed for pressure [6], strain [7], temperature [8], humidity [9], biochemical [10], gas [11] and so on. Typically, the capacitor changes in response to the parameter of interest, resulting in a shift in resonant frequency. ...
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A noteworthy challenge in actual wireless sensors is the intrinsic sensing resolution and the sensitivity associated with the response to external perturbation to be measured. To address the issue, we report the realization of enhanced sensitivity in a passive wireless sensing system, consisting of three coupled passive resonators. The input wave is exploited as an effective gain in our open system, thus the ideal parity-time (PT) symmetry can be established, rather than balancing real gain and loss. Then the third-order exceptional points are obtained in ternary PT symmetric systems. With the extrinsic perturbation imposed on any one of resonators, we demonstrate analytically and experimentally that the resonance response of the system follows the cube-root dependence on perturbation. Making use of the effective gain, our results pave a new way, to the best of our knowledge, to realize the ultra-sensitivity of a passive wireless sensing system.
... Thin film Lamb wave transducers take the advantages of compact size, good CMOS compatibility and erosion resistance [11], [12], [13], [14]. The lowest order anti-symmetry or flexural mode (A 0 ) in aluminum nitride (AlN) thin film Lamb wave transducers has been demonstrated the potentials for physical, chemical and biological detection [15], [16], [17]. A 0 mode is able to present a small attenuation in sensing once phase velocity C p of the flexural wave is lower than the sound phase velocity C L in liquid mediums [18], [19]. ...
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A two-port local resonating (TPLR) method for thin film Lamb wave sensor is proposed. Based on properties of multi-modes analyzed by numerical simulation and experimental measurement, the TPLR method is able to generate the second-order flexural mode A02 (A0i, i = 2). Density and sound velocity of liquid solutions can be decoupled based on the first-order flexural mode A01 (A0i, i = 1) and the A02 mode, and solutions with the same density such as CH3CH2OH and CH3OH can be successfully distinguished on a single Lamb wave device. When the phase velocity of A02 mode is close to the sound velocity of liquid, compared with the traditional delay-line configuration, smaller period of interdigital transducers (IDTs) and device miniaturization by the TPLR method can be realized. Generation of new modes with the TPLR method demonstrates an alternative for multi-parameters sensing of Lamb wave sensors.
... Microwave gas sensors are emerging as cheap and label-free techniques, and the lack of selectivity can be overcome by combining with highly selective materials [16][17][18][19][20]. Among different types of gas sensors, MEMS piezoelectric gas sensors, such as surface acoustic wave (SAW) resonators [21], Lamb wave resonators (LWR) [22] and film bulk acoustic resonators (FBAR) [23][24][25] have triggered a lot research interest due to their low power consumption, micrometer-scaled sizes, and relatively high sensitivities. Compared with quartz crystal microbalance (QCM), however, they suffer from relatively low Q values, which may result in poor limit of detection (LOD), large phase noise, and instability when integrating with oscillating circuits. ...
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