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In this paper, the significant electromechanical properties of the novel high-temperature piezoelectric single crystals YCa4O(BO3)3 (YCOB) were fully characterized over the temperature range from room temperature to 800 °C, including the dielectric, elastic, and piezoelectric properties, and electromechanical coupling coefficients and mechanical quality factor. More importantly, the complex coefficients were completely determined which take into account the mechanical and electrical losses of the material and, therefore, can describe the crystal behavior more accurately. The complete measurement procedures and calculation methods required to obtain all of these parameters were proposed. YCOB resonators with 23 different types of orientations were designed and measured, and all of the independent dielectric, piezoelectric, and elastic coefficients (4, 10, and 13, respectively), 6 important coupling factors, and the mechanical quality factor were determined. It was found that (1) the dielectric permittivity and loss increase dramatically and nonlinearly with the rise of temperature; (2) the elastic compliance constants basically increase linearly as the temperature rises, while the stiffness constants decrease linearly; (3) the piezoelectric charge constants d i j increase slightly with the elevated temperatures; (4) the coupling factors and mechanical quality factor decrease linearly with an increase of the temperature, and the coupling factors are in the range of 0.005–0.052, and the quality factor drops from 10 300 to 1300 with the temperature increasing from room temperature to 800 °C. [ABSTRACT FROM AUTHOR]

Aiming at the disadvantages of complex structure and high cost of multi-dimensional displacement measurement system, a single solid integrated sensor was proposed. In order to accurately describe the mechanical characteristics of the elastic element of the sensor, the quasi-static uniaxial compression test of the elastic element of the sensor was carried out under different strain rates. The hyperelastic constitutive model was sorted and simplified by using Taylor expansion to obtain the stress-strain relationship, and the stress-strain curve was fiited by using Origin. Four hyperelastic constitutive models, Mooney-Rivilin, Yeoh, Biderman and Ogden, were selected to describe the experimental curve. The results show that the Biderman model has the best fiiting effect on the curve, the Mooney-Rivilin model has the worst fiiting effect, and other models have small strain fiiting diiferences and moderate or higher deviations. The final obtained stress-strain relationship provides an important reference for the further research on the sensor. [ABSTRACT FROM AUTHOR]

To reveal the relationship between the strain at the fixed end of the polyurethane elastomer displacement sensor and the position and torsion of the moving end, based on the stress-strain relationship obtained from the uniaxial tensile experiment of rubber materials, the most suitable Ogden constitutive model and material parameters were determined by data fitting. The non-linear finite element model of the polyurethane elastomer displacement sensor was established with ABAQUS software, and the stress, strain and displacement change laws of the sensor under the displacement and torsion of the moving end were analyzed. The study shows that the strain at the fixed end increases with the loading of displacement and torsion of the moving end. When the displacement reaches 30 mm, the maximum strain appears at a distance of 4 mm from the fixed end; when the torsion reaches 15°, the maximum shear strain area is in the entire elastic body deformation part. This distribution law guides the placement of the strain gauges in the sensor design. Comparing the sensor simulation with the experimental data, the error is within 10%, which meets the requirements of the sensor. [ABSTRACT FROM AUTHOR]

In this paper, the dielectric, piezoelectric, and elastic properties of the Ca3TaGa3Si2O14 (CTGS) single crystals were fully investigated over the temperature range of \21^\circ\textC-\800\,^\circ\textC. Both the real and the complex coefficients were completely characterized. The real coefficients were determined through the measurements of the capacitance, impedance, or admittance of three kinds of plate samples (X-cut, Y-cut, and Z-cut) and four types of bar samples [XY-cut, ( XYt)\45^\circ, ( XYt)-\30^\circ, and ( XYt)-\85^\circ], according to the IEEE dynamic methods. Of utmost importance are the complex coefficients, which were obtained by taking into account the electrical and mechanical dissipations of the specimens, and therefore, they could describe the materials’ performance more accurately. In light of the characterization method developed by Du et al., three kinds of plate samples (X-cut, Y-cut, and Z-cut) and two types of bar samples [XY-cut and ( XYt)-\85^\circ] were designed for the determination of the materials’ complex coefficients. Moreover, the temperature behaviors of all the independent dielectric, piezoelectric, and elastic coefficients (2, 2, and 6, respectively) were summarized: the real parts of the complex dielectric coefficients (equal to the real dielectric coefficients) rise gradually with the increase of the temperature, while the imaginary parts increase dramatically after \400^\circC; both the real and complex piezoelectric coefficients stay relatively stable over the measurement temperature range; all the absolute values of the elastic compliance coefficients, to varying degrees, increase with the temperature, while the elastic stiffness coefficients decrease, and some of them exhibit excellent linearity. [ABSTRACT FROM AUTHOR]

Aging not only affects the whole body performance but also alters cellular biological properties, including cell proliferation and differentiation. This study was designed to determine the effect of aging on the mechanical properties of tendon stem cells (TSCs), a newly discovered stem cell type in tendons, using quartz thickness shear mode (TSM) resonators. TSCs were isolated from both old and young rats, and allowed to grow to confluency on the surface of TSM resonators. The admittance spectrums of TSM with TSC monolayer were acquired, and a series of complex shear modulus G ' + jG ″ as well as average thickness h TSC were calculated based on a two-layer-loading transmission line model (TLM) for TSM resonator sensor. The results showed an overall increase in G ', G ″ and h TSC during aging process. Specifically, the storage modulus G ' of aging TSCs was over ten times than that of young, revealing an important increase in stiffness of aging TSCs. Additionally, through phase-contrast and scanning electronic microscopy, it was shown that aging TSCs were large, flat and heterogeneous in morphologies while young TSCs were uniformly elongated. Increased cell size and irregular cell shape might be associated with the dense cytoskeleton organization, which could lead to an increase in both stiffness and viscosity. These results are in agreement with previously published data using different measurement methods, indicating TSM resonator sensor as a promising tool to measure the mechanical properties of cells.

Platelet-rich plasma (PRP) has been applied in a series of clinical treatments. PRP contains high-concentrated platelets, which, when activated, could secret a variety of growth factors and cytokines, to promote and/or enhance healing of injured tissues. Non-activated platelets suspension could be prepared by an isolation method of centrifugation and washing currently. However, it is not clear whether platelets, if any, are already activated during this process and there is no simple method to monitor their activation accordingly. Shear-Horizontal Surface Acoustic Wave sensors (SH-SAW, Love Mode) are promising in fundamental biology as well as biomedical engineering, detecting cell behaviors in liquid in a non-invasive, simple and quantitative manner. In this study, Love mode sensors are adopted for the label-free detection of protein secreted by platelets. Carbon nanotube (CNT) is reported as an advisable platform of both non-specific protein adsorption and specific protein binding. For further improvement of Love mode sensor performance, novel CNT -coated parylene-C film is prepared on its surface as both the acoustic-wave-guiding layer and bio-interface layer. The S21 loss curves of Love mode sensors were recorded and the corresponding resonance frequencies were extracted. The results showed that the CNT-enhanced sensor possessed an increased resonance frequency shift when compared to normal sensor with single parylene-C film under identical collagen concentrations. Then, the modified sensor is used for label-free detection of protein released by various concentrations of platelets. The results revealed high sensitivity and consistency, indicating the potential of CNT-enhanced Love mode sensors in cell-based applications.