In this research, Surface Acoustic Wave (SAW) sensors are combined with a cascade impactor to perform real time PM10 and PM2.5 mass concentration measurements. The SAW sensors consist of 125 MHz delay lines based on Love waves propagating on an AT-cut quartz substrate. The Love waves are guided on the substrate’s surface using a silica layer. SAW sensors themselves are not capable to discriminate particles by their size, therefore, particle separation based on aerodynamic diameter is achieved using a 3 Lpm dedicated cascade impactor. The latter was designed to integrate the SAW sensors which are monitored using a phase shift measurement. The collected particles impact on the acoustic sensor’s surface inducing a gravimetric effect that modifies the acoustic wave propagation conditions. The resulted phase shift allows the measurement of the mass deposited on the sensitive zone. The novel cascade impactor with SAW sensors as particle collecting stages is exposed to different aerosols in the 0–150 μg/m³ concentration range and proved to be able to detect and differentiate particles based on their size in real time. The system’s response was compared to a commercial optical counter based on light scattering technology and was found to be in good agreement with it.

In this paper, we present how complementary characterization techniques, such as electrical measurements with a vector network analyzer (VNA), optical measurements with a laser Doppler vibrometer (LDV), and numerical simulations with the finite element method, coupled with spectral domain analysis (FEMSDA), allow us to independently access different properties of a SAW device and fully characterize its operation using the coupling-of-modes theory (COM). A set of chemical SAW sensors coated with parylene C layers of different thicknesses (1, 1.5, and 2 µm) and an uncoated sensor were used as test samples. The sensors represent dual-channel electroacoustic delay lines operating in the vicinity of 77 MHz. The IDTs consist of split aluminum electrodes deposited on a AT-cut quartz substrate. The thickness-dependent influence of the parylene C layer was observed on the operating frequency (SAW velocity), static capacitance, attenuation, crosstalk, and reflection coefficient. COM parameters were reported for the four cases considered; measured and simulated data show good agreement. The presented approach is suitable for the design, characterization, and validation of polymer film-coated SAW sensors.

The high risk of CO poisoning justifies the need for indoor air quality control and warning systems based on the detection of low concentrations (ppm‐ppb) of CO. Cobalt corrole complexes selectively bind CO vs. O₂, CO₂, N₂, opening new fields of applications. By combining the CO chemisorption properties of cobalt corroles with the known sorption capacity of MOFs, we hope to obtain high performance sensing materials for CO detection. In addition, the exposed metal sites of MOFs lead to CO₂ physisorption, allowing the co‐detection of CO and CO₂. In this work, PCN‐222, a stable Zr‐based MOF made from Ni(TCPP) with natural vacancies, has been used as a porous matrix for the grafting of electron‐poor metallocorroles. The materials were characterized by powder XRD, SEM and optical microscopy, BET analyses and gas adsorption measurements at 298 K. No degradation of the crystalline structure of PCN‐222 was observed. At 1 atm, the adsorbed CO_(g) volumes measured for the best materials were 12.15 cm³ g⁻¹ and 14.01 cm³ g⁻¹ for CoCorr2@PCN‐222 and CoCorr3@PCN‐222 respectively, and both materials exhibited high CO chemisorption and selectivity against O₂, N₂, and CO₂ at low pressure due to the highest energy of the chemisorption process vs physisorption.

In this work, the authors show the capabilities of Surface Acoustic Wave (SAW) devices coupled with various absorbents to probe the properties of gas sensitive materials for the manufacturing of hazardous gas sensors. The great capabilities of cobalt corroles for the trapping of carbon monoxide (CO) were exploited to produce selective sensors. These corroles were deposited on SAW delay lines surfaces and then exposed to carbon monoxide (CO) in standard conditions. Concentrations of a few hundreds of ppb were measured emphasizing the interest of such sensors for the detection of CO. Another type of sensitive layers exhibiting specific porosity adapted to the trapping of formaldehyde (CH₂O) were deposited on similar delay lines. A detection threshold of 140 ppb was shown. These encouraging results pave the way for the development of a functionalized SAW sensors network for multi-gas detection in indoor air.

This paper presents a comparative study of three types of surface acoustic waves sensors used for particulate matter detection along with a theoretical study tackling the possibility to switch to innovative materials called Piezoelectric-on-Insulator. These sensors are placed in a cascade impactor as impaction plates. Monitoring their phase variation allows us to measure the quantity of fine particles present in the air with high accuracy. Until now, the sensors used in our prototype are built on quartz substrate and present a sufficient sensitivity to fine particles. One major concern in our application is the fouling of the sensor’s surface with particles upon long periods of exposure. This shaped our drive to develop a self-cleaning sensor relying on other substrates with stronger electromechanical coupling coefficient (k²) [1] . Hence, the aim of this study is to demonstrate the possibility of using strongly coupled modes on different piezoelectric substrates for an accurate PM detection. Among these, different POI substrates are considered to assess their physical and acoustic properties, especially in terms of k² and thermal stability, for further optimization enabling their exploitation in the self-cleaning system that is being developed.