Interdigitated impedimetric-based Maackia amurensis lectin biosensor for prostate cancer biomarker.

Highly specific detection of tumor-associated biomarkers remains a challenge in the diagnosis of prostate cancer. In this research, Maackia amurensis (MAA) was used as a recognition element in the functionalization of an electrochemical impedance-spectroscopy biosensor without a label to identify cancer-associated aberrant glycosylation prostate-specific antigen (PSA). The lectin was immobilized on gold-interdigitated microelectrodes. Furthermore, the biosensor's impedance response was used to assess the establishment of a complex binding between MAA and PSA-containing glycans. With a small sample volume, the functionalized interdigitated impedimetric-based (IIB) biosensor exhibited high sensitivity, rapid response, and repeatability. PSA glycoprotein detection was performed by measuring electron transfer resistance values within a concentration range 0.01-100 ng/mL, with a detection limit of 3.574 pg/mL. In this study, the ability of MAA to preferentially recognize α2,3-linked sialic acid in serum PSA was proven, suggesting a potential platform for the development of lectin-based, miniaturized, and cost effective IIB biosensors for future disease detection.

Sensing Mechanism of Surface Acoustic Wave Magnetic Field Sensors Based on Ferromagnetic Films.

Surface acoustic wave (SAW) sensors with ferromagnetic materials are used to measure magnetic fields or electric currents. The magnetic field sensitivities of SAW magnetic field sensors are essentially influenced by various factors. The sensing mechanism is complex due to the multiphysics coupling of the magnetic field, solid mechanics, and electric field. The magnetostriction effect, ∆E effect, and the third-order material constants are taken into consideration. The shape demagnetizing effect is reduced by increasing the length-to-width ratio and length-to-height ratio of a ferromagnetic film on an SAW resonator. The model is verified by experiments and accurately predicts the magnetic field sensitivities of SAW resonant magnetic field sensors. The factors affecting the sensitivities are investigated from the perspective of the sensing mechanism. A grooved sensing surface structure is explored for improved sensitivity. The results are beneficial to design reliable SAW magnetic field sensors with enhanced sensitivity.

AlN/Pt/LN-Y128 Packageless Acoustic Wave Temperature Sensor.

Batteryless, wireless, and packageless acoustic wave sensors are particularly desirable for harsh high-temperature environments. In this letter, an acoustic wave sensor based on a lithium niobate (Y + 128° cut, abbreviated LN-Y128) substrate with a buried platinum interdigital transducer (IDT) in an aluminum nitride (AlN) overlayer is investigated. Previously, it was demonstrated theoretically that due to the specific properties of LN-Y128, Rayleigh-type guided waves can propagate at the AlN/IDT(Pt)/LN-Y128 interface. Here, this structure is, for the first time, studied experimentally, including the growth and properties of the AlN layer onto irregular platinum IDTs. Both Shear Horizontal and Rayleigh-type waves have been identified after the AlN deposition and the velocities are consistent with the fitted SDA-FEM-SDA (a combination of finite element modeling with spectral domain analysis) simulations. Electrical measurements with a surface perturbation and temperature measurements show that the AlN/IDT(Pt)/LN-Y128 bilayer structure is promising as a packageless high-temperature sensor.

Epitaxial Growth of Sc0.09Al0.91N and Sc0.18Al0.82N Thin Films on Sapphire Substrates by Magnetron Sputtering for Surface Acoustic Waves Applications.

Scandium aluminum nitride (ScxAl1-xN) films are currently intensively studied for surface acoustic waves (SAW) filters and sensors applications, because of the excellent tradeoff they present between high SAW velocity, large piezoelectric properties and wide bandgap for the intermediate compositions with an Sc content between 10 and 20%. In this paper, the growth of Sc0.09Al0.91N and Sc0.18Al0.82N films on sapphire substrates by sputtering method is investigated. The plasma parameters were optimized, according to the film composition, in order to obtain highly-oriented films. X-ray diffraction rocking-curve measurements show a full width at half maximum below 1.5°. Moreover, high-resolution transmission electron microscopy investigations reveal the epitaxial nature of the growth. Electrical characterizations of the Sc0.09Al0.91N/sapphire-based SAW devices show three identified modes. Numerical investigations demonstrate that the intermediate compositions between 10 and 20% of scandium allow for the achievement of SAW devices with an electromechanical coupling coefficient up to 2%, provided the film is combined with electrodes constituted by a metal with a high density.

FEM Modeling of the Temperature Influence on the Performance of SAW Sensors Operating at GigaHertz Frequency Range and at High Temperature Up to 500 °C.

In this work, we present a two-dimensional Finite Element Method (2D-FEM) model implemented on a commercial software, COMSOL Multiphysics, that is used to predict the high temperature behavior of surface acoustic wave sensors based on layered structures. The model was validated by using a comparative study between experimental and simulated results. Here, surface acoustic wave (SAW) sensors consist in one-port synchronous resonators, based on the Pt/AlN/Sapphire structure and operating in the 2.45-GHz Industrial, scientific and medical (ISM) band. Experimental characterizations were carried out using a specific probe station that can perform calibrated measurements from room temperature to 500 °C. In our model, we consider a pre-validated set of physical constants of AlN and Sapphire and we take into account the existence of propagation losses in the studied structure. Our results show a very good agreement between the simulation and experiments in the full range of investigated temperatures, and for all key parameters of the SAW sensor such as insertion losses, resonance frequency, electromechanical factor of the structure (k2) and quality factor (Q). Our study shows that k2 increases with the temperature, while Q decreases. The resonance frequency variation with temperature shows a good linearity, which is very useful for temperature sensing applications. The measured value of the temperature coefficient of frequency (TCF) is equal to -38.6 ppm/°C, which is consistent with the numerical predictions.

A Weak Form Nonlinear Model for Thermal Sensitivity of Love Wave Mode on Layered Structures.

A precise theoretical model for the thermal sensitivity of Love wave mode is significant in the structure design, temperature compensation, and the prediction of thermal behavior. This article proposes a weak form nonlinear model to calculate the thermal sensitivity of Love waves on arbitrary layered structures. The third-order material constants, as well as the thermal stress and strain tensors between the substrate, electrodes, and wave-guiding layer, are considered in the model. The 9 ×9 effective elastic and the 3 ×9 effective piezoelectric matrixes are imported into the nonlinear constitutive equations and boundary conditions using weak form expressions. A temperature-compensated Love wave mode resonator on a layered ZnO/interdigital transducer (IDT)/quartz structure is obtained. The theoretical model is verified through the comparison of experimental and analytical results. The model is beneficial for the design of Love wave devices and sensors.

SAW RFID Devices Using Connected IDTs as an Alternative to Conventional Reflectors for Harsh Environments.

Remote interrogation of surface acoustic wave identification tag (ID-tags) imposes a high signal amplitude which is related to a high coupling coefficient value ( K2 ) and low propagation losses ( α ). In this article, we propose and discuss an alternative configuration to the standard one. Here, we replaced the conventional configuration, i.e., one interdigital transducer (IDT) and several reflectors, by a series of electrically connected IDTs. The goal is to increase the amplitude of the detected signal using direct transmission between IDTs instead of the reflection from passive reflectors. This concept can, therefore, increase the interrogation scope of ID-tags made on a conventional substrate with high K2 value. Moreover, it can also be extended to suitable substrates for harsh environments, such as high-temperature environments: the materials used exhibit limited performances (low K2 value and relatively high propagation losses) and are, therefore, rarely used for identification applications. The concept was first tested and validated using the lithium niobate 128° Y-X cut substrate, which is commonly used in ID-tags. A good agreement between experimental and numerical results was obtained for the promising concept of connected IDTs. The interesting features of the structure were also validated using a langasite substrate, which is well-known to operate at very high temperatures. Performances of both substrates (lithium niobate and langasite) were tested with an in situ RF characterization up to 600 °C. Unexpected results regarding the resilience of devices based on congruent lithium niobate were obtained.

AlN/ZnO/LiNbO3 Packageless Structure as a Low-Profile Sensor for Potential On-Body Applications.

Surface acoustic wave sensors find their application in a growing number of fields. This interest stems in particular from their passive nature and the possibility of remote interrogation. Still, the sensor package, due to its size, remains an obstacle for some applications. In this regard, packageless solutions are very promising. This paper describes the potential of the AlN/ZnO/LiNbO3 structure for packageless acoustic wave sensors. This structure, based on the waveguided acoustic wave principle, is studied numerically and experimentally. According to the COMSOL simulations, a wave, whose particle displacement is similar to a Rayleigh wave, is confined within the structure when the AlN film is thick enough. This result is confirmed by comprehensive experimental tests, thus proving the potential of this structure for packageless applications, notably temperature sensing.

Materials for bioresorbable radio frequency electronics.

Materials, device designs and manufacturing approaches are presented for classes of RF electronic components that are capable of complete dissolution in water or biofluids. All individual passive/active components as well as system-level examples such as wireless RF energy harvesting circuits exploit active materials that are biocompatible. The results provide diverse building blocks for physically transient forms of electronics, of particular potential value in bioresorbable medical implants with wireless power transmission and communication capabilities.