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This work aims to present a multifunctional surface acoustic wave (SAW) device that is capable of simultaneously measuring magnetic field as well as temperature. This is achieved in three parts where a multilayered approach is used to first achieve a temperature compensated Love wave structure, followed by a micro-structuration of the sensitive layer to eliminate the effects of temperature on magnetic anisotropy and finally multiple resonances observed allow a multifunctionality in our device.

Vibration surface acoustic wave (SAW) sensors can be used in multiple areas like automotive and aerospace technologies. Remote wireless interrogation of these passive sensors and their operability at high temperature allows to use them on rotating and moving objects in harsh environments. This work concentrates on peculiarities related to RF-pulse interrogation of a SAW resonator (SAWR) vibration sensor. The analysis describes the vibration-induced continuously-shifting SAWR response resonance frequency by approximating it with a sequence of static frequency responses with different central frequencies that are fixed during each consequent interrogation cycle of excitation/reception intervals. This approach is justified by a relatively small (below 2 ppm) SAWR frequency change during each cycle. The analysis realized in a PC allows to simulate both AM and FM demodulation of arbitrary signals with complicated modulation. This method also gives some insight in understanding of distortions in re-radiated signal at a relatively large vibration magnitude. Modeling of the situation when the deviation of the SAWR sensor resonance frequency exceeds the SAWR response passband explains the observed phenomenon of the re-radiated power decrease. It also gives the explanation of the nature of non-linear features experimentally observed in demodulated signals at large levels of vibration. The described approach will be used for optimization of interrogation procedure.

SummarySurface acoustic wave sensors for industrial and biomedical applications Surface acoustic wave (SAW) devices are widely used as filters, resonators or delay lines in electronic systems for a wide range of applications such as mobile communication (cell phones), TVs, radar or stable resonators for clock generation . More recently, thanks to the sensitivity of the resonance frequency and the signal transmission delay to physical environmental parameters, the use of SAW devices has been expanded to measure gas concentrations, pressures, forces, temperatures, strains or radiations. SAW-based sensors have also the advantage of being passive (batteryless) and potentially remotely interrogated (wireless) In this talk, we will address the latest advances in SAW sensors with a focus on three main topics - Surface acoustic wave sensors for harsh industrial environments, especially at high temperatures - Magnetic SAW sensors - SAW sensors for biomedical applications, including “electronic tattoos”

In this communication, we describe the direct integration of thin film SAW resonators on industrial metals. Two different structures were studied numerically and experimentally: Al/ZnO/Duralumin and Al/ZnO/Titanium. Resonators were manufactured on ZnO thin film directly deposited by RF magnetron sputtering on polished Duralumin and Titanium substrates. The presence of Rayleigh waves was demonstrated. The aim of these resonators is an application in the field of structural health monitoring.

Surface acoustic wave devices are increasingly used as sensors, especially because they can be batteryless, wireless and packageless. With these features they become particularly interesting in the field of flexible electronics for the monitoring of the human body parameters. By combining a thinned lithium niobate Z-cut substrate to ultrathin and stretchable antennas, a remote temperature measurement has been demonstrated. The addition of two protective layers to obtain a packageless structure seems promising to achieve wireless temperature measurements on the skin.

Remote interrogation of SAW ID-tags imposes a high coupling coefficient value ($\text{K}^{\mathbf {2}}$), which many of the most promising substrates for high temperature applications do not possess. In this paper, we propose and discuss an alternative configuration to the standard one. Here, we replaced the standard configuration, i.e. one interdigital transducer (IDT) and several disconnected reflectors, by a series of electrically connected IDTs. The goal is to increase the amplitude of the reflected signals, using direct transmission between IDTs instead of the reflection on passive reflectors. Numerical simulations show promising results. A test structure was also characterized experimentally. As a first step, the test structure was based on the well-known lithium niobate $128 ^{\circ}\mathrm {Y} -\mathrm {X}-$cut substrate. This concept will be extended to other substrates with lower $\text{K}^{\mathbf {2}}$ value, which should prove especially interesting for high temperature applications.

Surface acoustic wave devices including magnetic materials have been shown to be useful to build up magnetic sensors. In the resonator geometry, we take advantage of the shape of the electrodes to engineer the response of the device. We studied theoretically and experimentally the response when the field is applied in the device plane, perpendicular to the electrode length. We show that the field range of measure can be adapted, for the same material, by changing either the thickness of the electrodes or their width.

In previous studies [1,2] we have shown the possibility to realize wireless magnetic SAW sensors with a delay line configuration using layered structures. SAW devices in resonator configuration with Ni interdigital transducers (IDT) on the substrate were also investigated by Kadota et al. [3]. The physical phenomena behind sensor behavior is still unclear and the interpretation of the results is not fully in line with the proposed theoretical models. This work aims to understand the physics and the interaction between acoustic waves and magnetostrictive layers under magnetic fields. Here, we investigate multilayer (LiNbO3/(TbCo2/FeCo)) SAW structures with different geometries and configurations.

Waveguiding layer acoustic waves (WLAW) technology is considered as a packageless solution for extreme miniaturization of acoustic wave devices. WLAW solution is also original and suitable for high-temperature applications. Indeed, the achievement of a stable high-temperature packaging still constitutes a technological lock, in particular regarding sealing performance. In this context, we consider AlN/GaN/Sapphire as a promising WLAW structure for high-temperature applications. Indeed, the high-temperature stability of these three materials was previously demonstrated. However, in order to develop fully operational WLAW sensors based on this layered structure, it is necessary to have a better knowledge of the behaviour of each constitutive material with respect to the temperature. Consequently, the aim of this work is to experimentally validate GaN and AlN elastic constants sets in a large temperature range, which is a prerequisite to make the design of WLAW sensors according to the targeted performance.

International audience; This paper describes the investigation of the potential of packageless structures for body-centric acoustic wave sensor applications based on Al2O3/ZnO/Lithium Niobate structures, which are investigated numerically and experimentally.

International audience; This paper describes the investigation of the potential of packageless structures for acoustic wave sensor applications based on Al2O3/IDT/GaN/Sapphire structure. The finite elements modeling predicts the possibility of acoustically isolated waveguiding layer acoustic wave (WLAW) to propagate inside this structure with very low displacement at the top surface of the topmost Al2O3 layer. This layer serves as a protecting layer against oxidation of internal layers as well as an acoustically isolating layer, providing a mean for packageless packaging of this structure. The modeling results get confirmation in experiments with the precursor IDT/GaN/Sapphire structure thus supporting hopes on the predicted correct operation of the final Al2O3/IDT/GaN/Sapphire structure.

This paper reports a novel millimeter-wave microstrip phase shifter on quartz substrate with a key feature: the use of a reconfigurable ground plane supported by a metalized ultrasoft PDMS (Polydimethylsiloxane) membrane, associated to an EWOD (ElectroWetting On Dielectric) vertical actuator.