Two technological options to achieve a high deposition rate, low stress plasma-enhanced chemical vapor (PECVD) silicon nitride be used in capacitive micromachined ultrasonic transducers (CMUT) fabrication are investigated and presented. Both developed implemented on standard production line PECVD equipment the framework of CMUT technology transfer from R & D production. A tradeoff between residual electrical properties is showed.

Abstract Background After stroke, patients must learn to use residual motor function correctly. Consistently, learning is crucial in stroke recovery. We assessed performance, practice-dependent on-line learning, and factors potentially affecting them patients. Methods This a cross-sectional observational study. Twenty-six with first brain leading upper limb deficit the subacute or chronic timeframe were enrolled. They performed Finger Tapping Task (FTT) both affected unaffected limbs. how...

In this paper an approximated 3-D model of cylinder shaped piezoceramics is described. the hypothesis axial symmetry, element vibration in extensional and radial directions described by two coupled differential wave equations. The obtained choosing, as solution these equations, orthogonal functions, each depending only on one axis, corresponding to propagation direction. mechanical boundary conditions are applied imposing continuity between stresses external forces surfaces integral way,...

This work describes a matrix model of the radial mode thin piezoceramic ring capable predicting dynamic behavior when two main surfaces are stress free, while lateral, inner, and outer loaded by an external medium. The is modeled as three-port system with mechanical ports one electrical port. With this approach it easy to compute resonance frequency spectrum, displacement, electric impedance ring. Good agreement between computed measured found. spectrum function inner-to-outer radius ratio...

In this paper we describe an approximate two-dimensional model of a single piezoelectric array element. Substantially, the element is structure whose vibrations can be described by two coupled differential wave equations with boundary conditions. We take as solution system orthogonal functions which depend only on one axis, corresponding to propagation direction, and satisfy conditions in integral form. This makes it necessary neglect coupling transverse direction; nevertheless approximation...

In this work a piezoelectric motor is described whose stator composed of cylindrical steel axle fitted at the center thin membrane. The rotor consists permanent magnet, pressed in contact with top surface axle, by means magnetic forces. A travelling wave, natural flexural vibration membrane, excited via effect. vertical displacement membrane geometrically amplified central obtaining wide precessional motion axle. On based transmission mechanism proposed motor. able to give relatively high...

This paper describes a new implementation of disk-type piezoelectric motor, whose stator is commercial available piezomembrane composed nickel alloy disk to which piezoceramic bonded. The two disks are concentric, and the total thickness very small. Ultrasonic motors based on concept driving rotor by mechanical vibration excited stator, via effect. in contact with force frictional between stator. To transform rotation, traveling wave must be surface. proposed motor can regarded as disk-type,...

In this work, an approximated 3-D analytical model of the Langevin transducer is proposed. The model, improving classical 1-D approach describing thickness extensional mode, allows us to predict also radial modes both piezoelectric ceramic disk and loading masses; furthermore, it able describe coupling between modes. order validate computed frequency spectrum compared with that obtained by measurements carried out on 13 manufactured samples different thicknesses diameter ratios. comparison...

Capacitive ultrasonic transducers, consisting of thin membranes scratched over a conducting backplate, offer many advantages compared to piezoelectric such as low impedance mismatch, energy density and cost. Recent developments in microfabrication technology have spurred novel design for transducers the range both air water applications. In this paper we report fabrication process using PECVD deposition technology. With it is possible change stress from compressive tensile, varying...

In this paper we describe a new approach for the design of ultrasono-therapy transducers. Usually, in kind transducer, lambda/2 front plate is inserted only order to ensure good mechanical protection active crystal from surrounding medium. However, with an accurate design, can also be used match piezoelectric element load both terms gain and bandwidth. To end apply technique normally acoustical imaging nondestructive testing, and, by means distributed matrix model, optimize thickness...

Density is a characteristic property of substance related to its mass and volume. On-line density sensors play an important role in several industrial applications, for example the monitoring liquid products. In this work resonant sensor measure liquids proposed. The active element piezoelectric bimorph, extensively used buzzers telephone receivers. border bimorph clamped into steel structure, designed realize open chamber which poured. By fixing volume chamber, also fixed; thus, variation...

In general the coupling factor is a dimensionless coefficient, defined as particular combination of dielectric, elastic, and piezoelectric coefficients that may be useful for internal energy conversion description in materials. order to extend definition quasistatic ratio energies dynamic conditions lossy materials, its current derivation are reviewed. It shown this parameter can computed also conditions, factors obtained static case simply related by proportionality coefficient. The square...

In this paper, a 3-D finite element analysis of the vibrational behaviour Langevin transducer and dependence its performances on length to diameter ratio is presented. Several transducers with total greater than, comparable to, smaller than have been simulated, frequency spectrum drawn in order identify regions where coupling between thickness radial modes exists, highlight limit classical 1-D theory. Performances any ratio, but all working at same (153 kHz), are evaluated by comparing...

Density is one of the characteristic properties a substance and on-line density sensors are interest in many industrial fields. In this paper, piezoelectric sensor proposed analyzed with FE methods experimentally. The active element cheap piezoceramic bimorph, widely used buzzers telephone receivers; bimorph clamped all around tightening its border to edge rigid open chamber which liquid poured. resonance flexural frequency membrane modified by mass, volume therefore mass can be obtained...

Ultrasonic transducers for broadband water-coupled operation in the low ultrasonic 30-100 kHz frequency range find their application different industrial and biomedical areas, such as non-destructive testing therapy. In this paper we propose design fabrication process of a multi-cell, piezoelectrically-actuated, flexural-mode transducer structure, characterized by mechanical impedance leading to wideband high sensitivity immersion flexibility definition active area shape. After investigating...

Front-face acoustic reflectivity of ultrasonic imaging transducers, due to impedance mismatch with the propagation medium, may cause reverberation phenomena during wideband pulse-echo operation. be reduced by promoting transmission echoes, received from transducer backing, and maximizing mechanical-to-electrical energy conversion dissipation tuning electrical load connected transducer. In Capacitive Micromachined Ultrasonic Transducers (CMUTs), transfer medium backing is very low large...

Liquids density measurements are highly required in both research and industrial applications, from process control petrochemical industry to product monitoring food processing. Commercial devices often expensive or unwieldy; therefore, a previous work, cheap handy resonant sensor, based on piezoelectric bimorph, was introduced. The operating principle is the variation of device electrical impedance, due liquid mass. By fixing volume, frequency can therefore be related density. maximum...

In this work, the radial symmetric vibration modes of thin piezoceramic rings have been analyzed by means a previously proposed theoretical model. Both resonance frequencies and effective electromechanical coupling factor (k(eff)), as function aspect ratio G between inner outer radii ring, were computed. The results shown that disk structure (G-->0) has only one symmetrical mode (with its harmonics), but, for ring (G-->1), two different are clearly distinguished: mode, which no harmonics,...

Typical bistouries used in cystectomy operations are designed to work second harmonic; they able produce displacements of more than 60 microns at a working frequency about 40 kHz. The needle the bistoury is inserted eye for 9 mm. Due relatively high wavelength, relevant vibration velocity present also insertion point. friction between and produces trauma due hyperthermia. In this minimize proposed, realized. proposed composed Langevin transducer two displacement amplifiers. It third harmonic...

It is well known that the performances of acoustic imaging arrays are degraded by interelement coupling. In this work effect on radiation pattern array cross-coupling due to filling material investigated. A hybrid experimental-numerical technique used. We built an with three different materials, without matching layers, and using a classical backing material. On every piezoelectric element we in probe small dimensions, order capture waveform its emitting surfaces. The waveforms were recorded...