Fresh water is a key natural resource for food production, sanitation and industrial uses and has a high environmental value. The largest water use worldwide (~70%) corresponds to irrigation in agriculture, where use of water is becoming essential to maintain productivity. Efficient irrigation control largely depends on having access to reliable information about the actual plant water needs. Therefore, fast, portable and non-invasive sensing techniques able to measure water requirements directly on the plant are essential to face the huge challenge posed by the extensive water use in agriculture, the increasing water shortage and the impact of climate change. Non-contact resonant ultrasonic spectroscopy (NC-RUS) in the frequency range 0.1–1.2 MHz has revealed as an efficient and powerful non-destructive, non-invasive and in vivo sensing technique for leaves of different plant species. In particular, NC-RUS allows determining surface mass, thickness and elastic modulus of the leaves. Hence, valuable information can be obtained about water content and turgor pressure. This work analyzes and reviews the main requirements for sensors, electronics, signal processing and data analysis in order to develop a fast, portable, robust and non-invasive NC-RUS system to monitor variations in leaves water content or turgor pressure. A sensing prototype is proposed, described and, as application example, used to study two different species: Vitis vinifera and Coffea arabica, whose leaves present thickness resonances in two different frequency bands (400–900 kHz and 200–400 kHz, respectively), These species are representative of two different climates and are related to two high-added value agricultural products where efficient irrigation management can be critical. Moreover, the technique can also be applied to other species and similar results can be obtained.

This paper shows the applications ultrasonic through–transmission technique to determine the elastic constants of two polymer-natural fiber composite materials with potential industrial application and economic and environmental advantages. The transversely isotropic coconut-epoxy and fique-epoxy samples were analyzed using an experimental setup which allows the sample to be rotated with respect to transducers faces and measures the time-of-flight at different angles of incidence. Then, the elastic properties of the material were obtained by fitting the experimental data to the Christoffel equation. Results show a good agreement between the measured elastic constants and the values predicted by an analytical model. The velocities as a function of the incidence angle are reported and the effect of the natural fiber on the stiffness of the composite is discussed

In this work, dispersive wave propagation in plant leaves is studied using a long distance laser-based ultrasonic method. Guided waves traveling through and along the midrib, as well as in the lamina, are measured and analyzed via wave attenuation, characteristic diagram and dispersion curves. Additionally, an estimation of the leaf elastic properties using the Rayleigh–Lamb model, supported by thickness-resonance frequency constraints, is proposed. This study paves the way for the development of acoustic fingerprints for the identification of leaves and their non-invasive and fairly non-destructive mechanical characterization, which is highly related to the plant hydraulics and photosynthetic activity.

Magnetomotive ultrasound (MMUS) stands out as a promising and effective ultrasound-based method for detecting magnetic nanoparticles (MNPs) within tissues. This innovative technique relies on the precise estimation of micrometric displacements induced by the interaction of an external magnetic field with MNPs. Pulsed MMUS has emerged as a strategic alternative to address limitations associated with harmonic excitation, such as heat generation in amplifiers and coils, frequency-dependent tissue mechanical responses, and prolonged magnetic field rise times. Despite the growing interest in MMUS, the devices conventionally employed to excite the coil are not specifically tailored to generate intense magnetic fields while minimizing interference with the transient behavior of induced displacements. To bridge this gap, our work introduces the design and fabrication of two pulse generators: one based on a capacitor-discharge circuit and the other on a resonant-inverter circuit. We evaluated the performance of these pulse generators by considering parameters such as the magnetic field generated, rise and fall times, and their ability to supply sustained current for varied pulse widths across different pulse repetition frequencies. Furthermore, we carried out a practical MMUS implementation using tissue-mimicking phantoms, demonstrating the capability of both devices to achieve magnetic fields of up to 1 T and average displacements of 25 µm within the phantom. In addition, we estimated the shear wave velocity, effective shear modulus, and their temperature-dependent variations. Our findings highlight the versatility and efficacy of the proposed pulse generators and emphasize their potential as low-cost platforms for theranostic applications, enabling the assessment of targeted entities within biological tissues.

Magnetomotive ultrasound is an imaging technique that maps the distribution of magnetic nanoparticles within tissues by detecting motion induced by a time-varying magnetic field, overcoming the inherent limitations of ultrasound in nanoparticle detection. However, a major challenge in this technique is reducing the halo effect, which is the induced motion observed in tissues surrounding nanoparticles even when those regions are nanoparticle-free. This effect remains unresolved in current experimental methods, as they primarily rely on axial displacements due to the high resolution of ultrasound transducers in that direction. This study introduces a vectorial motion approach to enhance the detection of magnetic nanoparticles in magnetomotive ultrasound. Experiments were conducted on tissue-mimicking phantom, ex-vivo bovine liver, and a murine model, all labeled with iron oxide nanoparticles. A mathematical framework was established to describe the relationship between the magnetic properties of nanoparticles, the applied magnetic field, and the resulting tissue strains and displacements. Additionally, the Lucas-Kanade method is introduced as a reliable tool for analyzing the magnetically induced displacement field. Results demonstrate that vector-valued displacement analysis improves the interpretation of magnetomotive ultrasound data. However, displacement data alone proved insufficient for accurately resolving nanoparticle distribution. By incorporating external magnetic field information, the halo effect was effectively reduced, decreasing overestimation by 38% in phantom, 41% in ex-vivo tissues, and 58% in preliminary in-vivo experiment. Furthermore, this approach reduces dependence on axial symmetry between the excitation coil and transducer, offering greater flexibility in experimental setups, which is particularly beneficial for in-vivo applications.

The present study contains an experimental analysis of the vibratory response in a low-cylinder engine motorcycle at varying suspension preloads. Three different speed bumps of varying heights were used to subject the motorcycle to different vibrations. The analysis was carried out in three domains: time, frequency, and time-frequency. A triaxial accelerometer was used to measure the vibrations at the seat of the vehicle. The results indicated that the suspension system became more differentiated as the height of the bumps increased. However, for lower bumps, the action of the three spring preloads studied was quite similar. Quantitatively, only the higher bump showed a significant difference between the set preloads. The spectral distribution revealed that the frequency of interest was below 20 Hz for all the studied cases, which is in the same range of human body natural frequencies. The findings of this research can be utilized to enhance the design of low-cost motorcycles, thereby improving the safety and comfort of their drivers and passengers. This study constitutes a significant step towards developing an affordable system capable of gathering sufficient data to support the creation of evidence-based public health policies and propose new transport industry standards based on field measurements.