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. / Fine particulate matters (PM) have a real impact on the quality of life and health of millions of people in large urban areas, especially in Asia. In order to detect them and quantify their concentration, optical PM sensors are the most widely studied, but remain relatively expensive and bulky. MEMS microcantilever transducers are widely used for gravimetric applications, for PM or gas detection, which requires high mass sensitivities (Sm) and low limits of detection (LOD). A solution is to focus on microcantilevers with high resonance frequencies (f0) and quality factors (Q), low measurement noise and low masses. Silicon microcantilevers are commonly used as gravimetric sensors and are serious candidates to meet the desired characteristics. However, screen printing has the potential for cheaper, faster and large scale manufacturing. Such microcantilevers can be actuated and f0 read-out using the piezoelectric effect. Although promising lead-free inorganic solutions exist, titanium lead zirconate (PZT) ceramics still have the best properties among piezoelectric materials. Screen-printed microcantilevers manufactured in hybrid thick-film technology, with integrated piezoelectric actuation and read-out, released using a polyester sacrificial layer and with co-firing of all the layers are presented here. Different geometries were tested from 1 mm to 2 mm wide and from 1 mm to 8 mm long, for a thickness of about 100 μm. A density ρ PZT = 7200 kg/m³ (≈ 93%ρ PZT bulk) was obtained. With a 1×2×0.1 mm³ microcantilever, a sensitivity Sm ≈ 85 Hz/μm and a LOD of 70 ng were found, compatible with applications in PM mass detection.

The fields of health care and environment control have an increasing demand for sensors able to detect low concentrations of specific molecules in gaseous or liquid samples. The recent introduction of microfabricated devices in these fields gave rise to sensors with attractive properties. A cutting edge technology is based on guided acoustic waves, which are perturbed by events occurring at the nanometer scale. A first part of the thesis investigates the Love mode waveguide, a versatile structure in which a thin film is guiding the acoustic wave generated in a piezoelectric substrate. A systematic analysis of its sensitivity was obtained using a transmission line model generalized to discriminate the rigid or viscous nature of the probed layers. We developed a novel integrated combination of the Love mode device with a Surface Plasmon Resonance optical sensor to quantify the thickness and the composition of soft layers. The electromagnetic interferences in the recorded signal were modeled to determine the phase velocity in the sensing area and to provide new mechanisms for an enhanced sensitivity. The experimental aspects of this work deal with the fabrication, the important issue of the packaging and the sensitivity calibration of the Love mode biosensor. A second part of the thesis investigates nanocrystalline diamond under the form of a thin film membrane suspended to a rigid silicon frame. The high mechanical and chemical resistance of nanocrystalline diamond, close to single-crystal diamond, open ways to membrane based acoustic sensors such as Flexural Plate Wave and thin Film Bulk Acoustic Resonators (FBAR). A novel dynamic characterization of the thin film is reported and the properties of composite FBAR devices including a diamond thin film membrane and a piezoelectric aluminum nitride layer are assessed using the perturbation theory. This study is applied to evaluate the high sensing potential of the first prototype of an actual diamond-based composite FBAR.

The fields of health care and environment control have an increasing demand for sensors able to detect low concentrations of specific molecules in gaseous or liquid samples. The recent introduction of microfabricated devices in these fields gave rise to sensors with attractive properties. A cutting edge technology is based on guided acoustic waves, which are perturbed by events occurring at the nanometer scale. A first part of the thesis investigates the Love mode waveguide, a versatile structure in which a thin film is guiding the acoustic wave generated in a piezoelectric substrate. A systematic analysis of its sensitivity was obtained using a transmission line model generalized to discriminate the rigid or viscous nature of the probed layers. We developed a novel integrated combination of the Love mode device with a Surface Plasmon Resonance optical sensor to quantify the thickness and the composition of soft layers. The electromagnetic interferences in the recorded signal were modeled to determine the phase velocity in the sensing area and to provide new mechanisms for an enhanced sensitivity. The experimental aspects of this work deal with the fabrication, the important issue of the packaging and the sensitivity calibration of the Love mode biosensor. A second part of the thesis investigates nanocrystalline diamond under the form of a thin film membrane suspended to a rigid silicon frame. The high mechanical and chemical resistance of nanocrystalline diamond, close to single-crystal diamond, open ways to membrane based acoustic sensors such as Flexural Plate Wave and thin Film Bulk Acoustic Resonators (FBAR). A novel dynamic characterization of the thin film is reported and the properties of composite FBAR devices including a diamond thin film membrane and a piezoelectric aluminum nitride layer are assessed using the perturbation theory. This study is applied to evaluate the high sensing potential of the first prototype of an actual diamond-based composite FBAR.