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The transducer is an essential part of all ultrasonic systems used for applications such as medical diagnostics, therapy, nondestructive evaluation, and cleaning because its health condition is vital to their proper operation. Defects within the active element, backing or other constitutive elements, and loss of adhesion between layers can significantly weaken the performance of a transducer. The objective of this work is to determine procedures to monitor the behavior of a single-element probe during its lifetime and detect degradations before they significantly affect the performance of the system. To achieve this, electromechanical admittance (EMA)-based method is envisaged numerically and experimentally. A simplified single-element transducer consisting of a piezoceramic disk, a bonding layer, and a backing is studied and the influence of bonding delamination on EMA is investigated. This study considers three different types of delaminations, which are named, respectively, "center" (circular delamination from the center of the disk toward the peripheric zone), "peripheric" (annular delamination from the peripheric zone toward the center), and "wedge" (wedge-shaped delamination with a given angle). For each case, a numerical model based on the finite-element (FE) method is developed: a 2-D FE analysis is implemented for the first two types of delaminations, taking advantage of their axisymmetric structure, and "wedge" delamination is modeled in 3-D. Then, transducers with different shapes of 3-D printed backings are mounted and experiments are conducted using an impedance analyzer. Finally, experimental results are found to be in good agreement with numerical solutions and it shows that changes in EMA can particularly reveal the occurrence and extent of delamination in an ultrasound probe.

Understanding the mechanisms that drive transition from acute to chronic pain is essential to identify new therapeutic targets. The importance of endogenous resolution pathways acting as a "brake" to prevent development of chronic pain has been largely ignored. We examined the role of interleukin-10 (IL-10) in resolution of neuropathic pain induced by cisplatin. In search of an underlying mechanism, we studied the effect of cisplatin and IL-10 on spontaneous activity (SA) in dorsal root ganglia neurons. Cisplatin (2 mg/kg daily for 3 days) induced mechanical hypersensitivity that resolved within 3 weeks. In both sexes, resolution of mechanical hypersensitivity was delayed in Il10 mice, in WT mice treated intrathecally with neutralizing anti-IL-10 antibody, and in mice with cell-targeted deletion of IL-10R1 on advillin-positive sensory neurons. Electrophysiologically, small- to medium-sized dorsal root ganglia neurons from cisplatin-treated mice displayed an increase in the incidence of SA. Cisplatin treatment also depolarized the resting membrane potential, and decreased action potential voltage threshold and rheobase, while increasing ongoing activity at -45 mV and the amplitude of depolarizing spontaneous fluctuations. In vitro addition of IL-10 (10 ng/mL) reversed the effect of cisplatin on SA and on the depolarizing spontaneous fluctuation amplitudes, but unexpectedly had little effect on the other electrophysiological parameters affected by cisplatin. Collectively, our findings challenge the prevailing concept that IL-10 resolves pain solely by dampening neuroinflammation and demonstrate in a model of chemotherapy-induced neuropathic pain that endogenous IL-10 prevents transition to chronic pain by binding to IL-10 receptors on sensory neurons to regulate their activity.

The transducer is an essential part of all ultrasonic systems used for applications such as medical diagnostics, therapy, nondestructive evaluation, cleaning or other purposes because its performance is crucial for that of the entire device. Its health condition is thus vital to ensure proper operation. Defects within constitutive elements or loss of adhesion between them can significantly reduce the transducer performance. The objective of this work is to determine procedures to monitor the behavior of a multi-element probe during its lifetime and detect degradations before they significantly affect the performance of the system. To achieve this, electromechanical admittance-based (EMA-based) method is investigated numerically and experimentally. A simplified multi-element transducer element consisting of a piezoceramic bar, a bonding layer and a backing is studied and the influence of bonding delamination on EMA is investigated. This study considers two different types of delamination, which are named respectively ”side” (from one side and expands towards the other) and ”center” (from the center and expands outwards). First, three dimensional numerical models based on the finite element method are developed. Secondly, transducers with and without defects are mounted using 3D-printed backings and matching layers, and finally measurements are conducted using an impedance analyzer. Experimental results are found to be in good agreement with numerical ones and it is shown that changes in EMA could allow early detection of delamination defects in an ultrasound probe.

In this paper, the superposition method is extended to obtain analytical solutions for the coupled vibration of a piezoelectric slender bar in a configuration corresponding to a typical ultrasonic linear array transducer element. The problem can be described mathematically by three partial differential equations with electrical and mechanical boundary conditions. To solve this, the vibrations in lateral and thickness directions are referred to as two building blocks. In each building block, the expressions of displacements and electric potential are assumed first based on their symmetry properties and then the induced dynamic responses, such as in-plane stress and electric displacements, are calculated. Finally, the vibration responses of the two building blocks are superimposed to satisfy the boundary conditions using Fourier series expansions. Electrical impedance and mode shapes, represented by the spatial distribution of displacements and electric potential, are calculated analytically and compared with the results of the finite element method. An excellent agreement is observed. The method can be applied to design and optimize piezoelectric array transducers for various applications.

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This paper deals with two-dimensional (2D) modeling of coupled vibrations of finite piezoelectric resonators. A general solution for all the physical quantities in Cartesian and cylindrical coordinate systems is deduced from the governing equations by expansion in series summation of trigonometric functions of thickness coordinate and trigonometric or Bessel functions of the lateral one. The essential difference between this model and the earlier ones is that instead of expressing mainly in the thickness coordinate and an integration through the thickness, the solutions are expressed in the form of double Fourier series augmented by single Fourier or Fourier-Bessel series, which contributes to better satisfy the mechanical and electrical boundary conditions. The dynamic stiffness matrix of the system is developed. Electrical impedances of a typical piezoelectric parallelepiped under stress-free and symmetrical loading conditions, and its frequency spectrum for different width-to-thickness ratios are calculated using our model as well as by the finite element method. Comparison shows an excellent agreement. Finally, theoretical and measured electrical impedances of a piezoelectric parallelepiped and a piezoelectric disk are compared and discussed. The 2D theoretical model proposed here is shown to be accurate and efficient for coupled vibration analysis of piezoelectric resonators and is applicable for any set of finite dimensions and crystal symmetry.

In this paper, an electromechanical admittance EMA-based method is proposed to monitor the behavior of the transducer and detect the degradations during its lifetime. An array element from a typical linear array transducer consisting of a piezoelectric parallelepiped, a backing, a matching layer, and kerfs fillers is studied and the influence of bonding delamination on EMA curves is investigated numerically and experimentally. Depending on the location of delaminations, two cases, i.e. delaminations between the ceramic and backing or between the ceramic and matching layer, are considered here. Numerical and experimental results show an excellent agreement, and the resonance amplitude and root mean square deviation (RMSD) are good indicators to quantify the changes in EMA. The linear variation pattern shown in these indicators can be particularly used to reveal the occurrence and severity of a delamination in ultrasonic transducers.

We prepared a stacked structure consisting of a quasi-free-standing functional oxide thin film and a ceramic piezoelectric disk and observed the effect of the piezoelectric disk deformation on the resistance of the thin film. Epitaxial V2O3 films were grown by a pulsed laser deposition method on muscovite mica substrates, peeled off using Scotch tapes, and transferred onto piezoelectric elements. In this V2O3/insulator/top electrode/piezoelectronic disk/bottom electrode structure, the resistance of the V2O3 film displayed a variation of 60% by sweeping the piezoelectronic disk bias. With support from x-ray diffraction measurements under an electric field, a huge gauge factor of 3 × 103 in the V2O3 film was inferred. The sizeable resistance change in the V2O3 layer is ascribed to the piezo-actuated evolution of c/a ratios, which drives the material towards an insulating phase. A memory effect on the resistance, related to the hysteretic displacement of the piezoelectric material, is also presented., This work was financially supported by Région Centre, France, through Project COMHET (No. 2013 00082885).

The radial and thickness extensional vibration modes in piezoelectric cylinders are always inevitably coupled due to the finite dimension, Poisson’s ratio, and piezoelectric effect. In this paper, an analytical model based on the superposition method is developed to obtain the coupled dynamic response of a piezoelectric cylinder under an applied voltage. The problem can be described mathematically by three partial differential equations with mixed boundary conditions in the cylindrical coordinates system. To solve this, the problem is decomposed first into two building block – vibrations in radial and thickness directions. In each building block, the expressions of displacements and electric potential are assumed and then the induced dynamic responses, such as in-plane stress and electric displacements, are calculated. Finally, the vibration responses of the two building blocks are superimposed to satisfy the mixed boundary conditions using Fourier and Fourier-Bessel series expansions. Electrical impedance of a typical piezoelectric disk and frequency spectrum of piezoelectric cylinders of different diameter-to-thickness ratios are calculated by the present analytical method as well as by finite element method. Comparison shows an excellent agreement. This analytical model can be applied to material characterization and the design and the optimization of the active elements of piezoelectric devices.

Neuropathic pain is a major, inadequately treated challenge for people with spinal cord injury (SCI). While SCI pain mechanisms are often assumed to be in the CNS, rodent studies have revealed mechanistic contributions from primary nociceptors. These neurons become chronically hyperexcitable after SCI, generating ongoing electrical activity that promotes ongoing pain. A major question is whether extrinsic chemical signals help to drive ongoing electrical activity after SCI. People living with SCI exhibit acute and chronic elevation of circulating levels of macrophage migration inhibitory factor (MIF), a cytokine implicated in preclinical pain models. Probable nociceptors isolated from male rats and exposed to an MIF concentration reported in human plasma (1 ng/ml) showed hyperactivity similar to that induced by SCI, although, surprisingly, a 10-fold higher concentration failed to increase excitability. Conditioned behavioral aversion to a chamber associated with peripheral MIF injection suggested that MIF stimulates affective pain. A MIF inhibitor, Iso-1, reversed SCI-induced hyperexcitability. Unlike chronic SCI-induced hyperexcitability, acute MIF-induced hyperexcitability was only partially abrogated by inhibiting ERK signaling. Unexpectedly, MIF concentrations that induced hyperactivity in nociceptors from naive animals, after SCI induced a long-lasting conversion from a highly excitable nonaccommodating type to a rapidly accommodating, hypoexcitable type, possibly as a homeostatic response to prolonged depolarization. Treatment with conditioned medium from cultures of DRG cells obtained after SCI was sufficient to induce MIF-dependent hyperactivity in neurons from naive rats. Thus, changes in systemic and DRG levels of MIF may help to maintain SCI-induced nociceptor hyperactivity that persistently promotes pain. SIGNIFICANCE STATEMENT Chronic neuropathic pain is a major challenge for people with spinal cord injury (SCI). Pain can drastically impair quality of life, and produces substantial economic and social burdens. Available treatments, including opioids, remain inadequate. This study shows that the cytokine macrophage migration inhibitory factor (MIF) can induce pain-like behavior and plays an important role in driving persistent ongoing electrical activity in injury-detecting sensory neurons (nociceptors) in a rat SCI model. The results indicate that SCI produces an increase in MIF release within sensory ganglia. Low MIF levels potently excite nociceptors, but higher levels trigger a long-lasting hypoexcitable state. These findings suggest that therapeutic targeting of MIF in neuropathic pain states may reduce pain and sensory dysfunction by curbing nociceptor hyperactivity.

International audience; The transducer is an essential part of all ultrasonic systems used for applications such as medical diagnostics, therapy, nondestructive evaluation, cleaning or other purposes because its health condition is vital to their proper operation. Defects within the active element, backing or other constitutive elements, loss of adhesion between layers can significantly weaken the performance of a transducer. The objective of this work is to determine procedures to monitor the behavior of a single-element probe during its lifetime and detect degradations before they significantly affect the performance of the system. To achieve this, electromechanical admittance-based (EMA-based) method is envisaged numerically and experimentally. A simplified single-element transducer consisting of a piezoceramic disk, a bonding layer and a backing is studied and the influence of bonding delamination on EMA is investigated. This study considers three different types of delaminations, which are named respectively ?center? (circular delamination from the center of the disc towards the peripheric zone), ?peripheric? (annular delamination from the peripheric zone towards the center) and ?wedge? (delamination from the center to the outside with a given angle). First, a numerical model based on the finite element method is developed. A two-dimensional (2D) finite element analysis is implemented for the first two types of delaminations, taking advantage of their axisymmetric structure, and ?wedge? delamination is modeled in three dimensions (3D). Secondly, transducers with different shapes of 3D printed backings are mounted and experiments are conducted using an impedance analyzer. Experimental results are found to be in good agreement with numerical solutions and it is shown that changes in EMA could allow early detection of delaminations in an ultrasound probe.