Surface acoustic wave (SAW) transducers propagating shear waves are compatible with sensing chemical compounds in a liquid phase. However, if the liquid surrounding the sensor possesses a higher permittivity than the piezoelectric substrate, then the interdigitated electrodes for converting the incoming electromagnetic wave to acoustic waves are susceptible to capacitive short-circuiting, leading to excessive insertion losses. By using high-permittivity lithium tantalate oxide (LTO), we demonstrate chemical sensing in water without the need for dedicated microfluidic packaging. Nevertheless, the gravimetric sensitivity of these package-less transmission Love-mode delay lines remains comparable to that of low-permittivity quartz when appropriately tuning the guiding layer of thin film to confine energy to the surface in a Love mode. We extend the transmission line gravimetric sensitivity measurement to a reflective delay line geometry for passive transducers that can be wirelessly probed. For instance, ground-penetrating radar (GPR) can be used for subsurface sensing, here targeting water pollution detection, operating in the 100-500-MHz range. This center frequency was selected as a tradeoff between penetration depth (lower frequency) and antenna size (smaller at higher frequency). Nonspecific binding of proteins detection is shown in the context of biosensing applications.

The detection of organophosphates, a wide class of pesticides, in water-solution has a huge impact in environmental monitoring. Acoustic transducers are used to design passive wireless sensors for the direct detection of pesticides in water-solution by using tailored polymers as sensitive layers. We demonstrate by combining analytical chemistry tools that organophosphate molecules strongly alter polymer layers widely used in acoustic sensors in the presence of water. This chemical degradation can limit the use of these polymers in detection of organophosphates in water-solution.

Long-term monitoring of organic pollutants in the soil is a major environmental challenge. We propose to meet this issue by the development of a polymer dedicated to selectively react with H2S, coating surface acoustic wave transducers designed as passive cooperative targets with the compound, and probing their response using Ground Penetrating RADAR, thus providing the capability to monitor the presence of H2S in the subsurface environment. The selectivity is brought by including lead(II) cation in a reticulated polymer matrix which can be deposited as a thin layer on a surface acoustic wave sensor. We demonstrate a signal enhancement mechanism in which water absorption magnifies the signal detection, making the sensor most sensitive to H2S in an underground environment saturated with moisture.

The software defined radio (SDR) global navigation satellite system decoder gnss-sdr, based on GNU Radio, is used to prototype computationally efficient global positioning system (GPS) anti-spoofing and anti-jamming strategies using controlled radiation pattern antenna and null steering towards a unique interfering source. Experimental demonstration is achieved on GPS L1 when running gnss-sdr on a Raspberry Pi4 single board computer fetching radiofrequency datastreams from an Ettus Research B210 SDR frontend.

Passive wireless transducers are used as sensors, probed by a RADAR system. A simple way to separate the returning signal from the clutter is to delay the response, so that the clutter decays before the echoes are received. This can be achieved by introducing a fixed delay in the sensor design. Acoustic wave transducers are ideally suited as cooperative targets for passive, wireless sensing. The incoming electromagnetic pulse is converted into an acoustic wave, propagated on the sensor substrate surface, and reflected as an electromagnetic echo. According to a known law, the acoustic wave propagation velocity depends on the physical quantity under investigation, which is then measured as an echo delay. Both conversions between electromagnetic and acoustic waves are based on the piezoelectric property of the substrate of which the sensor is made. Investigating underground sensing, we address the problems of using GPR (Ground-Penetrating RADAR) for probing cooperative targets. The GPR is a good candidate for this application because it provides an electromagnetic source and receiver, as well as echo recording tools. Instead of designing dedicated electronics, we choose a commercially available, reliable and rugged instrument. The measurement range depends on parameters like antenna radiation pattern, radio spectrum matching between GPR and the target, antenna-sensor impedance matching and the transfer function of the target. We demonstrate measurements at depths ranging from centimeters to circa 1 m in a sandbox. In our application, clutter rejection requires delays between the emitted pulse and echoes to be longer than in the regular use of the GPR for geophysical measurements. This delay, and the accuracy needed for sensing, challenge the GPR internal time base. In the GPR units we used, the drift turns out to be incompatible with the targeted application. The available documentation of other models and brands suggests that this is a rather general limitation. We solved the problem by replacing the analog ramp generator defining the time base with a fully digital solution, whose time accuracy and stability relies on a quartz oscillator. The resulting stability is acceptable for sub-surface cooperative sensor measurement.

The fast and efficient detection of foodborne pathogens is a societal priority, given the large number of food-poisoning outbreaks, and a scientific and technological challenge, given the need to detect as little as 1 viable cell in 25 gr of food. Here, we present the first approach that achieves the above goal, thanks to the use of a micro/nano-technology and the detection capability of acoustic wave sensors. Starting from 1 Salmonella cell in 25 ml of milk, we employ immuno-magnetic beads to capture cells after only 3 h of pre-enrichment and subsequently demonstrate efficient DNA amplification using the Loop Mediated Isothermal Amplification method (LAMP) and acoustic detection in an integrated platform, within an additional ½ h. The demonstrated 4 h sample-to-analysis time comes as a huge improvement to the current need of few days to obtain the same result. In addition, the work presents the first reported Lab-on-Chip platform that comprises an acoustic device as the sensing element, exhibiting impressive analytical features, namely, an acoustic limit of detection of 2 cells/μl or 3 aM of the DNA target and ability to detect in a label-free manner dsDNA amplicons in impure samples. The use of food samples together with the incorporation of the necessary pre-enrichment step and ability for multiple analysis with an internal control, make the proposed methodology highly relevant to real-world applications. Moreover, the work suggests that acoustic wave devices can be used as an attractive alternative to electrochemical sensors in integrated platforms for applications in food safety and the point-of-care diagnostics.

This chapter introduces the basic principles of acoustic-based Radio-Frequency devices (RF) and the various structures usually implemented for sensors. It emphasizes the intrinsic qualities of each type of device and briefly discusses their technological implementation. The basic acoustic wave characteristics must also comply with the requirements related to the operation of the host electronic system for wired and wireless applications as well. Passive acoustoelectric devices are extensively used for quite a long time for various RF applications. Some theory is recalled to allow for understanding how these devices are designed and for describing the engineer's usual optimization process to maximize or simply tailor the sensitivity to address industrial requirements. The chapter presents the state of the art concerning accuracy, resolution and stability, interrogation distance, and long-term robustness of these systems, with a discussion on further development of such devices and their present and future applications.

The development of integrated, fast and affordable platforms for pathogen detection is an emerging area where a multidisciplinary approach is necessary for designing microsystems employing miniaturized devices; these new technologies promise a significant advancement of the current state of analytical testing leading to improved healthcare. In this work, the development of a lab-on-chip microsystem platform for the genetic analysis of Salmonella in milk samples is presented. The heart of the platform is an acoustic detection biochip, integrated with a microfluidic module. This detection platform is combined with a micro-processor, which, alongside with magnetic beads technology and a DNA micro-amplification module, are responsible for performing sample pre-treatment, bacteria lysis, nucleic acid purification and amplification. Automated, multiscale manipulation of fluids in complex microchannel networks is combined with novel sensing principles developed by some of the partners. This system is expected to have a significant impact in food-pathogen detection by providing for the first time an integrated detection test for Salmonella screening in a very short time. Finally, thanks to the low cost and compact technologies involved, the proposed set-up is expected to provide a competitive analytical platform for direct application in field settings.

This work presents a comparison between three different High-overtone Bulk Acoustic Resonators based on different materials. Furthermore, the goal of this work is to realize a High-overtone Bulk Acoustic Resonators presented a temperature coefficient of frequency less than 10 ppm over a wide range of temperature around a turnover temperature, and a Q.f product higher than 5×1013 Hz. After a discussion about the choice of materials to achieve such resonator and the description of our microfabrication, three High-overtone Bulk Acoustic Resonators based on a Lithium of Niobate, Quartz, Lithium of Tantalate, AlN and Sapphire materials are compared in term of the temperature coefficient of frequency, the Q.f product and the phase noise. The new HBAR exhibits a Q.f product around 3.7×1013 Hz, a turnover around 55°C with a parabolic shape and a temperature coefficient of frequency around +/-4 ppm/K.

Vibration sensitivity is an important specification for oscillators dedicated to space or airborne systems. Vibration sensitivity can be due to from resonator, oscillator loop or non-oscillator components as wire for example. Commonly, the main source of acceleration sensitivity is due to the resonator. Active compensation can be used to decrease this effect, but such systems are not easily miniaturized. This paper presents quality factor and temperature coefficient of frequency of three different high-overtone bulk acoustic resonator and phase noise of corresponding oscillators and the first result of oscillator vibration sensitivity based on high-overtone bulk acoustic resonator. Three resonators based on different material are tested.

Detecting chemical species in gas phase has recently received an increasing interest mainly for security control, trying to implement new systems allowing for extended dynamics and reactivity. In this work, an open-loop interrogation strategy is proposed to use radio-frequency acoustic transducers as micro-balances for that purpose. The resulting system is dedicated to the monitoring of chemical compounds in gaseous or liquid-phase state. A 16 Hz standard deviation is demonstrated at 125 MHz, with a working frequency band in the 60 to 133 MHz range, answering the requirements for using Rayleigh- and Love-wave-based delay lines operating with 40-μm acoustic wavelength transducers. Moreover, this electronic setup was used to interrogate a high-overtone bulk acoustic wave resonator (HBAR) microbalance, a new sensor class allowing for multi-mode interrogation for gravimetric measurement improvement. The noise source still limiting the system performance is due to the analog-to-digital converter of the microcontroller, thus leaving open degrees-of-freedom for improving the obtained results by optimizing the voltage reference and board layout. The operation of the system is illustrated using a calibrated galvanic deposition at the surface of Love-wave delay lines to assess theoretical predictions of their gravimetric sensitivity and to compare them with HBAR-based sensor sensitivity.

For an increasing number of applications, hydrogen represents a solution of the future as it is the most common element in the Earth. However, due to its unstable properties in gas phase, a particular care must be dedicated to control possible gaseous leaks close to tanks and facilities using this resource. In this paper, surface acoustic wave sensors are proposed for detecting gaseous hydrogen in standard environmental conditions (atmospheric pressure and room temperature). The proposed Surface Acoustic Wave sensors consists in two Rayleigh-wave delay lines built on Quartz, one equipped with a palladium overlay and the other exhibiting a free path between the two interdigited transducers. A specific gas test cell has been developed to test various sensor configurations submitted to hydrogen-composed atmospheres. A particular care was paid to avoid hydrogen leakage in the working environment and to perform the regeneration of the gas absorbing layer. The developed device allows for identifying different concentrations of hydrogen (in the 1-4 % range) diluted in nitrogen and is also able to detect hydrogen in current atmosphere. Surface Acoustic Wave devices exploiting hydrogen absorption capabilities of palladium thin films have been here used to make the detection and the identification of hydrogen concentrations in the 1-4 % range and the influence of outer parameters such as temperature and relative humidity variations on the sensor operation are also reported.

Le besoin d’appareils compacts et autonomes dedies a la detection d’especes chimiques pour des analyses de terrain est d’actualite dans un contexte international en rapide mutation (agroalimentaire, developpement durable, securite, etc.). La these presentee au sein de ce manuscrit, financee par la Delegation Generale de l’Armement, developpe de nouvelles solutions de capteurs resonants a ondes elastiques de volume a modes harmoniques eleves (HBARs) pour la detection de gaz et plus particulierement de composes explosifs. Ces resonateurs de tres haute compacite se composent d’un transducteur reporte ou depose sur une cavite resonante multimode, produisant un spectre de raies modulant sa propre reponse frequentielle. De nature dipolaire, ces resonateurs permettent toutefois la mise au point de quadripoles par couplage lateral de modes mis a profit dans nos travaux. L’etude theorique du comportement de resonateurs a base de niobate de lithium aminci et reporte sur quartz ou fondes sur un empilement de nitrure d’aluminium et de silicium a permis de determiner les proprietes gravimetriques specifiques de chaque combinaison de materiaux et des modes associes. Des methodes de calibrage en phase liquide et gazeuse sont proposees pour valider l’analyse theorique et permettre le choix de la structure la mieux adaptee a une configuration experimentale donnee. Les resultats obtenus, compares a ceux d’une microbalance a ondes guidees sur quartz, mettent en evidence les forces (compacite, cinetique chimique reduite, nature multi-physique des mesures) et faiblesses (sensibilite gravimetrique imposant des structures d’epaisseur inferieure a 100 μm) de notre solution face a cette reference. Nous avons egalement developpe une electronique de traitement en boucle ouverte des informations issues de nos dispositifs, permettant des modes de detection rapide ou de haute precision (quelques milli-degres de variation de phase). L’electronique dediee a pour vocation de fournir la flexibilite necessaire au suivi de nombreux modes a diverses frequences fixes et de s’affranchir des temps longs de balayage en frequence des analyseurs de reseaux generalistes. Une version a8 voies permet enfin la manipulation de plusieurs capteurs ou l’etude en parallele des modes de 2 HBARs, donnant ainsi lieu a un systeme multi-physique efficace associe a des capteurs capables de sonder plusieurs grandeurs dans un volume de tres petite dimension (quelques mm3). La limite de detection est determinee par le bruit de phase de l’oscillateur local. Le systeme ainsi realise est exploite pour la detection de gaz mais aussi pour le pilotage de grandeurs physiques telles que la temperature ou la viscosite (milieux aqueux) dans differents contextes experimentaux.

For an increasing number of application (energy production, car industry, space, etc.), hydrogen appears as a solution of the future as it is the most common body in the Universe (and therefore on Earth). However, due to its unstable properties, a particular care must be dedicated to control possible gaseous leaks close to facilities using this resource. Here we propose surface acoustic wave sensors for detecting gaseous hydrogen in standard environmental conditions (atmospheric pressure and room temperature). The proposed SAW sensors consists in two Rayleigh-wave delay lines built on Quartz. One equipped with a Palladium overlay and the other exhibiting a free path between the two interdigitated transducers. A dedicated hermetical gas test cell has been developed to test the efficiency of the sensor when exposed to hydrogen-composed atmospheres. A particular care was paid to avoid hydrogen leakage in the working environment and to perform the regeneration of the gas absorbing layer. The developed SAW devices exploiting hydrogen absorption capabilities of palladium layers exhibiting different thicknesses have been here used to make the detection and the identification of hydrogen concentrations (in the 0.25-2% range) diluted in nitrogen and is also able to make detection in current atmosphere. The effect of the palladium thickness variations along with the influence of an Yttrium doping of the palladium layer on the sensor behavior will be studied here.

One strategy in addressing the issue of selectivity in direct detection gas sensors - and specifically when using piezoelectric acoustic transducers - is to use multichannel measurement approaches in which each sensor is functionalized with a different chemical layer and provides different responses when exposed to a given mixture of gasses. Within this context, an 8-channel open loop embedded electronics operating as a transmission-mode radiofrequency network analyzer has been developed. The frequency ranges generated by the synthesizer is 50 to 160 MHz or 200 to 500 MHz. A low noise phase detection scheme was implemented, in addition to magnitude measurement. This instrument is used with Surface Acoustic Wave (SAW) and High-overtone Bulk Acoustic Resonator (HBAR) transducers: in the former case, the open-loop approach allows for an improved measurement dynamics, while in the latter case multiple resonances can be probed sequentially, yielding different acoustic penetration depths in the sensing layer. Demonstration of measurement in liquid phase is provided by characterizing the gravimetric sensitivity of HBARs using copper electrodeposition. Values ranging from 2.2 to 13.1 cm 2 /g are observed, emphasizing a departure from a perturbative Sauerbrey-like relationship.