In this thesis, the author proposed and developed nanostructured materials based Surface Acoustic Wave (SAW) and conductometric transducers for gas sensing applications. The device fabrication, nanostructured materials synthesis and characterization, as well as their gas sensing performance have been undertaken. The investigated structures are based on two structures: lithium niobate (LiNbO3) and lithium tantalate (LiTaO3). These two substrates were chosen for their high electromechanical coupling coefficient. The conductometric structure is based on langasite (LGS) substrate. LGS was selected because it does not exhibit any phase transition up to its melting point (1470°C). Four types of nanostructured materials were investigated as gas sensing layers, they are: polyaniline, polyvinylpyrrolidone (PVP), graphene and antimony oxide (Sb2O3). The developed nanostructured materials based sensors have high surface to volume ratio, resulting in high sensitivity towards di¤erent gas species. Several synthesis methods were conducted to deposit nanostructured materials on the whole area of SAW based and conductometric transducers. Electropolymerization method was used to synthesize and deposit polyaniline nanofibers on 36° YX LiTaO3 and 64° YX LiNbO3 SAW substrates. By varying several parameters during electropolymerization, the effect on gas sensing properties were investigated. The author also extended her research to successfully develop polyaniline/inorganic nanocomposites based SAW structures for room temperature gas sensing applications. Via electrospinning method, PVP fibres and its composites were successfully deposited on 36° YX LiTaO3 SAW transducers. Again in this method, the author varied several parameters of electrospinning such as distance and concentration, and investigated the effect on gas sensing performance. Graphene-like nano-sheets were synthesized on 36° YX LiTaO3 SAW devices. This material was synthesized by spin-coating graphite oxide (GO) on the substrate and then exposin g the GO to hydrazine to reduce it to graphene. X-ray photoelectron spectroscopy (XPS) and Raman characterizations showed that the reduced GO was not an ideal graphene. This information was required to understand the properties of the deposited graphene and link its properties to the gas sensing properties. Thermal evaporation method was used to grow Sb2O3 nanostructures on LGS conductometric transducers. Using this method, different nanoscale structures such as nanorods and lobe-like shapes were found on the gold interdigitated transducers (IDTs) and LGS substrate. The gas sensing performance of the deposited nanostructured Sb2O3 based LGS conductometric sensors was investigated at elevated temperatures. The gas sensing performance of the investigated nanostructured materials/SAW and conductometric structures provide a way for further investigation to future commerciallization of these types of sensors.

A highly successful architecture for the exchange of single quanta between coupled quantum systems is circuit quantum electrodynamics (QED), in which the electrical interaction between a qubit and a high-quality microwave resonator offers the possibility to reliably control, store, and read out quantum bits of information on a chip. This architecture has also been implemented with mechanical resonators, showing that a vibrational mode can in principle be manipulated via a coupled qubit. The work presented in this thesis consists of realising an acoustic version of circuit QED that we call circuit quantum acoustodynamics (QAD), in which a superconducting qubit is piezoelectrically coupled to an acoustic cavity based on surface acoustic waves (SAWs). Designing and building this novel platform involved the following main accomplishments: a systematic characterisation of SAW resonators at low temperatures; successfully developing a recipe for the fabrication of Josephson junction on quartz and diamond; measuring the coherence time of superconducting 3D transmon qubits on these substrates and demonstrating the dispersive coupling between a SAW cavity and a qubit on a planar geometry. This thesis presents evidence of the coherent interaction between a SAW cavity and a superconducting qubit in several ways. First of all, a frequency shift of the mechanical mode as a function of qubit frequency is observed. We also measure the acoustic Stark shift of the qubit due to the population of the SAW cavity. The extracted coupling is in agreement with theoretical expectations. A time delayed acoustic Stark shift serves to further demonstrate that the Stark shifts that we observe are indeed due to the acoustic field of the SAW mode. The dispersive coupling between these two quantum systems offers the possibility to perform qubit spectroscopy using the SAW resonator as readout component, indicating that these acoustic resonators can, in principle, be adopted as an alternative qubit readout scheme in quantum information processors. We finally present preliminary measurements of the direct coupling between a SAW resonator and a transmon on diamond, suggesting that strong coupling can in principle be obtained.

Cette thèse s’inscrit dans le contexte du développement des laboratoires sur puce (LOC, « Lab On a Chip », permettant de réaliser plusieurs opérations nécessaires à l’analyse d’un échantillon biologique à l'intérieur d'un seul microsystème. Dans ce type de dispositif, de nombreuses étapes sont nécessaires avant d’arriver au résultat d’une analyse donnée (introduction de l'échantillon, concentration, mélange, purification, séparation, etc.). L’équipe microsystèmes du laboratoire Ampère étudie depuis plusieurs années différentes techniques de manipulation sans contact de particules, pour le tri ou de manipulation de particules individuelles dans les laboratoires sur puce, telles que la diélectrophorèse ou la magnétophorèse. Dans cette thèse, nous nous intéressons à la manipulation acoustique de micro particules. Cette technique se révèle notamment avantageuse pour la manipulation d’objets biologiques comme des bactéries, car elle permet de s’affranchir de certaines contraintes de marquage ou de changement de milieu. Notre choix s’est porté sur l’emploi des ondes acoustiques de surface (SAW, « Surface Acoustic Waves »), compatibles avec la filière PDMS très utilisée dans la communauté des LOC. Outre la possibilité de simplifier l’intégration microfluidique de la pince acoustique, la technologie SAW offre une alternative aux dispositifs à pièges acoustiques fixes existant dans la littérature en permettant un contrôle en temps réel des particules piégées. C’est ce que nous avons réalisé expérimentalement : en jouant sur le déphasage entre les signaux d’alimentation électriques des transducteurs électromécaniques, nous pouvons modifier la position des noeuds et des ventres de l’onde acoustique résultante. Ainsi, nous avons pu contrôler en temps réel la position d’une bille en latex de 3 μm ou encore d’un faisceau de bactéries E.coli. Par ailleurs, nous avons réalisé une simulation par éléments finis de la puce acoustofluidique dans son ensemble permettant une meilleure compréhension de tous les phénomènes en jeu et l’optimisation du transfert énergétique entre la source électrique et la particule manipulée. Cette simulation nous indique notamment que l’amplitude de l’onde acoustique stationnaire sur le substrat piézoélectrique varie environ d’un facteur deux en fonction du déphasage imposé entre les deux sources électriques. Cela impacte donc dans la même proportion la force acoustique résultante. Cette variation semble être validée par nos dernières expériences. / In lab-on-a-chip (LOC) technologies, many sample preparation steps are required before achieving a biological analysis on a single chip (sample introduction, concentration, mixing, purification, separation, etc.). The microsystem team of the Ampere Lab has studied for many years different contactless particle manipulation techniques, for sorting or manipulating bioparticles in LOC platforms, such as dielectrophoresis and magnetophoresis. In this thesis, we focus on acoustic manipulation of microparticles. This technique is advantageous for the manipulation of biological objects such as bacteria, because labelling and medium exchange can be avoided. We chose to work with surface acoustic waves (SAW), because this approach is consistent with the use of PDMS, widely used in microfluidics. Besides an easier microfluidic integration of the acoustic tweezers, the SAW technology provides an alternative to the existing devices with fixed acoustic traps, allowing a real time control of the trapped particles. This was experimentally achieved by playing on the phase shift between the two electrical signals driving the IDT, thereby modifying the position of nodes and antinodes of the resulting pressure wave. As a result, we could control in real time the position of a 3 μm latex bead or an E.coli bacteria alignment. We have also developed a finite-element model of the whole acoustofluidic chip allowing a better understanding of the physics and the optimization of the energy transfer between the electrical source and the trapped particle. Among different results, this model informs us that the magnitude of the acoustic radiation force varies by a factor of two with the phase shift between the electrical sources. This result seems to be validated by our last experiments.

Phenylalanine hydroxylase (PAH, EC: 1.14.16.1) is a non-heme iron tetrahydropterin-dependent monooxygenase that maintains phenylalanine (L-Phe) homeostasis via conversion of L-Phe to L-Tyr. PAH is an allosteric enzyme that converts from an inactive T-state to an active R-state upon addition of substrate, L-Phe. Allosteric activation is correlated with physical and structural changes within the enzyme and a large activation energy. Crystal structures of PAH have not identified the location of the allosteric effector binding site. Herein, we report computational protein mapping efforts using the FTmap algorithm and experimental site-directed mutagenesis studies designed to define and screen possible L-Phe allosteric binding sites. Mass spectroscopic analysis of PAH proteolytic fragments obtained after photo-crosslinking with 2-azido-3-phenylpropanoate overlapped with one computationally derived allosteric binding pocket containing residues 110-120 and 312-317. Ligand docking studies, fluorescence measurements, binding affinity and activity assays on wild-type and mutant enzymes further characterized the shape and specificity of this pocket. Thermodynamic studies using surface acoustic wave (SAW) biosensing determined the affinity of L-Phe for the allosteric site. Two L-Phe binding sites were observed upon SAW titrations, corresponding to the active and allosteric sites respectively ( K D,app^on 113 ± 12 µM active site, K D,app^on 680 ± 20 µM allosteric site). Site-directed mutagenesis was performed to prepare mutant enzymes containing a single tryptophan (L-Trp) residue. The fluorescence signatures of each of the three native L-Trp residues in PAH were determined by titrations with L-Phe. Trp187 primarily reports L-Phe induced allosteric conformational changes, while Trp120 reports active site L-Phe binding. Trp326 reports small signals of both active and allosteric site changes. Variable temperature stopped-flow fluorescence kinetic studies elucidated a working mechanism for L-Phe allosteric activation of PAH. Fluorescent signals from wild-type, single, and double L-Trp PAH mutants have been used to build kinetic mechanisms for the L-Phe binding in each subunit and subsequent active site reorganization or allosteric conformational change. In these mechanisms, the enzyme has reduced activity (1-2% of wtPAH) until both L-Phe induced active and allosteric site conformational changes have occurred. Failure of either activation step prevents enzyme turnover and is the chemical-based cause of the metabolic condition phenylketonuria.

This thesis focuses on the theory, fabrication, and characterization of 2-port surface acoustic wave (SAW) resonators, as well as the application of their Fabry-Pérot resonance modes for strain sensing. The thesis includes three articles. In the first article, a fabrication method for high frequency SAW devices using traditional UV photolithography equipment is developed. It is well known that SAW sensors become more sensitive at higher frequencies but realizing high frequency devices requires small features which challenge existing photolithography methods. The proposed process is a modified version of a previously reported tri-layer lift-off photolithography process intended for Si or SiO2 substrates which allows for compatibility with materials that are piezoelectric and pyroelectric, often used as the substrate in SAW devices. The process uses a lithographic tri-layer consisting of layers of lift-off resist (LOR) on the bottom, back anti-reflection coating (BARC) in the middle, and photoresist (PR) on top, improving resolution by a factor of two over traditional lift-off photolithography techniques. We demonstrate the fabrication of a SAW device with an interdigital transducer (IDT) pitch of 4 μm (minimum feature size of 1 μm) on 128o Y-X cut lithium niobate, whose operating frequency is measured as 994.5 MHz. The 2-Port SAW devices that are used in subsequent chapters are fabricated using this process. The second article proposes a method of analyzing acoustic Fabry-Pérot spectra, by analogy with optical cavities, to determine key SAW parameters. In our experiment, 2-port SAW resonators, consisting of two interdigital transducers (IDTs) laterally separated by a free surface cavity length, are used to generate SAWs on 128o Y-X lithium niobate that are trapped between the two IDTs which also act as Bragg reflectors. Fabry-Pérot cavity peaks can be observed through the electrical S11 (reflection) spectrum measured on one IDT, hence a 2-Port resonator is equivalent to an acoustic Fabry-Pérot cavity/resonator. Measurements of the free spectral range and linewidths are then fitted to linear models to obtain the free surface velocity and attenuation of SAW waves, as well as the reflection of interdigital transducers (IDTs), all of which are crucial design parameters. Our method of analyzing Fabry-Pérot spectra provides a convenient method for determining key characteristics of SAW waves and cavities. In the third article, a surface acoustic wave (SAW) strain sensor based on measuring acoustic Fabry-Pérot resonance peaks from a 2-port SAW resonator is demonstrated. A theoretical analysis is proposed to estimate the frequency sensitivity to strain of IDT and cavity resonances and to predict strain distributions in both the cavity and IDT regions of a 2-port SAW resonator bonded to a tapered cantilever beam. The frequency stability of cavity resonance peaks for fabricated 2-port SAW resonators of different cavity length are measured and analyzed to determine the cavity length which exhibits maximum frequency stability. A cross-correlation analysis technique is then introduced to improve the detection of the frequency shift of SAW resonances and enable multimode frequency shift detection. The measured frequency sensitivity to strain of the cavity resonances of a resonator 10 mm in length (operating frequency = 97.7 MHz) was found to be -103.2 ± 0.2 Hz/με while demonstrating excellent linearity (R2 = 0.9999). By considering a minimum signal to noise ratio (SNR) of 3 dB, the device exhibits a minimum strain resolution of only 234 nε.

No description available.

Medicine is constantly developing and in order to (early) diagnose common diseases, such as cancer, Parkinson's or Alzheimer's, a liquid biopsy-based approach is of increasing relevance. Samples are complex body fluids, especially blood, whereby a separation of the cells, particles and molecules of interest is often necessary for a subsequent analysis. Conventional methods such as centrifugation, the gold standard of many sample preparations, are reaching their limits in terms of gentle cell separation, purity and automatability. At the same time, the volumes of biological samples required for analysis are decreasing and point-of-care solutions are becoming increasingly important. New technologies for sample preparation are therefore urgently needed to meet this demand. Surface acoustic wave (SAW)-based microfluidic systems have already shown promising results in the handling of biological samples, but there is still a lack in the ability to transfer laboratory set-ups into a real-world environment. In this work, an industrially feasible manufacturing technology for SAW-based microfluidic chips that can be used for separation of blood plasma was developed. For this purpose, polymeric microchannels were integrated directly on the piezoelectric substrate together with the interdigital transducers required for SAW excitation. This was done reproducibly on the wafer-level with established lithographic methods, but a relatively young material system, i.e. dry film resists, allowing an industrial scale-up of the acoustofluidic chips. Furthermore, the chip layout was designed robustly to ensure a stable and continuous separation process and the “lab-around-the-chip” was further developed into an easy-to-use system. Moreover, blood plasma separation at high flow rates of up to 50 μL/min for a 1:5 diluted sample and a throughput of 888,000 cells/s in the SAW-based microfluidic chip was demonstrated. In comparison to microfluidic alternatives, high cell separation purity was achieved with special focus on the use of analytical methods for the detection of low cell concentrations in blood plasma. Direct comparison to centrifugation further indicated a gentler separation method for the cells and more reproducible results. The SAW-based microfluidic system developed in this work offers great potential for future application in liquid biopsy.

Surface Acoustic Wave (SAW) devices have been under research for over half a century due to their excellent performance characteristics in the fields of signal processing and communications. In particular, it has been show that SAW devices can operate as sensors that are both wireless and passive. For a sensor that is wireless, it is important to develop a coding scheme that allows for the identification of an individual sensor in a multiple sensor environment. For SAW sensors, orthogonal frequency coding (OFC) has been demonstrated as a method to provide a large number of unique identification codes. This system relies on an array of frequency selective reflectors (chips) in the SAW propagation path. The reflectors are ordered such that no two SAW sensors contain an array of reflection gratings in the same frequency order. One way to increase the number of usable codes in an OFC sensor is to increase the number of OFC chips on the sensor. With this technique it is necessary to increase the delay between the transducer and the OFC chips while keeping the length of the device small. Multiple surface wave propagation tracks can be utilized to slightly increase the width of the die instead of the length. This research aims to investigate methods to extend delay time in a coded SAW device by utilizing two propagation tracks. It will be shown that the reflective multistrip coupler (RMSC) can accomplish this goal with low loss. The design, fabrication, and characterization of the RMSC will be given with applications shown in an OFC SAW device.

Les travaux décrits dans ce mémoire ont pour but de conduire à la réalisation de capteurs et de filtres à ondes élastiques de surface (SAW) innovants, passifs et sans fil, dédiés à une utilisation en environnement sévère. Différentes structures de composants SAW sont alors étudiées. Les caractéristiques générales, telles que les pertes d’insertion ou les bandes passantes relatives atteignables, des structures usuelles (résonateurs, lignes à retard, LCRF, filtres en échelle…) sont connues de l’homme de l’art. Cependant, pour concevoir un dispositif SAW qui respecte les critères d’un cahier des charges donné, il est impératif de définir le comportement spécifique de chaque dispositif avant son envoi en production.Pour ce faire, des modèles numériques sont développés, qui incluent à la fois la possibilité d’analyser le comportement de systèmes à la géométrie complexe (filtres en échelles, transducteurs apodisés) et qui prennent en compte la présence de phénomènes perturbateurs (modes transverses, pertes liées à la nature des matériaux). La comparaison entre les calculs numériques et les mesures a mis en avant l’adéquation des résultats expérimentaux et de calculs.La mise en place de ces outils permet le développement de capteurs et filtres SAW innovants grâce à une analyse numérique rapide et fiable de leur comportement.Ainsi, l’étude de résonateurs et capteurs dédiés à une utilisation à des températures excédant les 700°C est menée. Il est démontré qu’en dépit de son inhomogénéité, le Ba2TiSi2O8 est un matériau adapté à la réalisation de SAW soumis à des températures élevées pour des fréquences de l’ordre de 300 MHz jusqu’au GHz.Par ailleurs, une structure disposant d’un transducteur à trois doigts par longueur d’ondes est utilisée dans le but de réaliser des résonateurs insensibles aux effets de la directivité lorsque la température évolue. Cette même configuration a mis en exergue la possibilité de réaliser des capteurs n’utilisant qu’un seul résonateur (contre au moins deux jusqu’à présent). Ce dernier point permet de limiter l’encombrement des composants et résout la problématique du vieillissement différentiel des structures.Un second type de capteurs, passifs et sans fil, fondés sur l’utilisation d’un seul SAW et dédiés à la mesure d’hygrométrie, a été étudié. Dans cette nouvelle configuration, un SAW de type LCRF est utilisé comme transpondeur et la zone sensible est externalisée. La sensibilité des modes (de plus d’un MHz) à la variation d’un élément capacitif ou d’une antenne dipôle a été mise en avant numériquement. En pratique, la fabrication des dispositifs a montré une variation différentielle de plusieurs centaines de kHz des résonances selon la condition électrique appliquée à l’un des ports.Finalement, des filtres, dédiés aux applications stratégiques, agiles en fréquence sont réalisés. L’objectif de faire varier la fréquence centrale des dispositifs au cours de leur fonctionnement est atteinte en modifiant les conditions électriques appliquées aux réflecteurs. Deux types de tirage en fréquence sont observés : un glissement fin, de quelques ‰ de la fréquence centrale, cyclique, et un saut de fréquences lié au glissement et à l’ouverture de la bande de Bragg des miroirs aux hautes fréquences. La fabrication des structures et leur connexion à des interrupteurs MEMS validé la faisabilité de la structure.Ces travaux mettent en lumière les capacités de prédiction du comportement des structures SAW grâce au développement de logiciels dédiés. De plus, l’étude et la réalisation de filtres et capteurs innovants ouvre la voie à de nouvelles fonctionnalités. / This thesis aims at designing innovative, passive and wireless surface acoustic waves (SAW) sensors and filters, dedicated to harsh environments. Several types of SAW components are consequently studied. The main characteristics, such as insertion losses or relative bandwidth, of usual structures (resonators, delay lines, LCRF, ladder filters…) are known by men of the art. However, to design a SAW device that respects specific requirements, the definition of the proper behavior of each device must be established before the manufacturing.For this purpose, numerical models are developed. Not only they include the possibility to analyse he beha-vior of systems with complex geometry (ladder filters, apodised transducers) but they take into account disturbing phenomena (transverse modes, losses due to the intrinsic nature of the materials). The comparison between computations and measures points out the match between experimental results and calculations.The implementation of these tools allows the development of innovative SAW sensors and filters thanks to a fast and reliable numerical analysis of their behavior.Thus, the design of resonators and sensors dedicated to a use at temperatures exceeding 700°C is studied. It is demonstrated that despite its inhomogeneity, Ba2TiSi2O8 is suitable for the manufacturing of SAW devices subject to high temperatures and in a frequency range from 300 MHz to the GHz.Furthermore, a structure composed of a three electrodes per wavelength transducer is used to produce re-sonators that are not subject to directivity effects when the temperature changes. This configuration offers the possibility to design sensors that use a single resonator (versus at least two until now). This last point makes smaller components possible and solves the question of a differential aging of the structures.A second type of sensors, also passive and wireless, dedicated to humidity measurements, based on the use of a single SAW, is studied. In this new configuration, a LCRF is used as a transponder and the sensitive area is outsourced. The mode sensitivity (of more than a MHz) to the variation of a capacitance or a dipole antenna is numerically brought to light. In practice, the device manufacturing showed a differential variation of the resonances of about 600 kHz depending on the electric condition applied to one of the ports.Finally, filters, dedicated to strategic applications, with frequency agility are designed. The purpose is to make the frequency vary depending on the electrical conditions applied to the mirrors. Two kinds of agility are identified : a slight sliding, of a few ‰ of the initial central frequency, periodic, and a frequency jump due to the shift of the Bragg band to the high frequencies. The manufacturing of some structures and their connection to MEMS switches attest the feasibility of such a structure.This work highlights the ability to predict the behavior of SAW structures thanks to the development of dedicated software. Moreover, the analysis and the manufacturing of innovative sensors and filters pave the way to new functionalities.

Single-photon sources are essential building blocks in quantum photonic networks, where quantum-mechanical properties of photons are utilised to achieve quantum technologies such as quantum cryptography and quantum computing. In this thesis, a single-photon source driven by a surface acoustic wave (SAW) is developed and characterised. This single-photon source is based on a SAW-driven lateral n-i-p junction in a GaAs quantum-well structure. On this device, the lateral n-i-p junction is formed by gate-induced electrons and holes in two adjacent regions. The SAW potential minima create dynamic quantum dots in a 1D channel between these two regions, and are able to transport single electrons to the region of holes along the channel. Single-photon emission can therefore be generated as these electrons consecutively recombine with holes. After characterisation and optimisation in four batches of devices, clear SAW-driven charge transport and the corresponding electroluminescence (EL) can be observed on an optimised SAW-driven n-i-p junction. Time-resolved measurements have been carried out to study the dynamics of SAW-driven electrons. Time-resolved EL signals indicate that a packet of electrons is transported to the region of holes in each SAW minimum. In addition, the carrier lifetime of SAW-driven electrons in the region of holes is shown to be $\sim 100$ ps, which is much shorter than the SAW period of $860$ ps. Hence, it is promising to observe single-photon emission in the optimised device. In order to test single-photon emission, a Hanbury Brown-Twiss experimental setup has been employed to record an autocorrelation histogram of the SAW-driven EL signal at the single-electron regime. Suppression of autocorrelation coincidences at time delay $\Delta t = 0$ is evidence of photon antibunching. By fitting theoretical functions describing the SAW-driven EL signal, it is found that the second-order correlation function shows $g^{(2)}(0) = 0.39 \pm 0.05$, which is lower than the common criterion for a single-photon source $g^{(2)}(0) < 0.5$. Moreover, theoretical calculation and simulation suggest that, if a constant background signal can be filtered out, $\sim 80 \%$ of the SAW-driven EL is single-photon emission.