Transducers

Abstmct-Experimental and theoretical studies have revealed several effects in surface-acoustic-wave chirp filters that arise from electrode reflections. One effect is that down-chirp filters have lower loss than up-chirp filters, which is shown to be caused by ...

In this paper, we present preliminary results showing the response of glucose-sensitive hydrogels, confined in micro-pressure sensors, to the changes in environmental glucose concentration. The glucose concentrations were incrementally varied between 20 and 0mM in 0.15M PBS solution at 7.4 pH and bovine serum at 7.4 pH at room temperature and response of the sensor was recorded. The micro sensors demonstrate a response time of 10 minutes in both PBS and serum. Tissue response after 55 days of subcutaneous implantation of a EtO sterilized sensor in mice is presented. The preliminary analysis of the surrounding tissue shows inflammation which is believed not to interfere with the sensor performance.

Deep-seated tumors can be treated by minimally invasive interstitial ultrasound thermal therapy. A miniature transducer emitting high-intensity acoustic waves is placed in contact with the targeted area to induce local thermal necrosis. Accurate positioning of the probe and treatment monitoring must be achieved for the technique to be effective. A piezocomposite technology was used for obtaining both high-quality imaging and effective treatment with the same transducer. Prototypes were designed and built to be compatible with an endoscopic approach for treating cholangiocarcinomas in the biliary ducts. The transducer had dimensions of 2.5 x 7.5 mm(2), it was cylindrically focused at 10 mm and it was operated at a center frequency of 11 MHz. Transducer efficiency was measured at 71%, and the impulse response corresponded to an axial resolution of 0.2 mm. In-vitro tests were conducted on samples of pig liver in which lesions up to 10 mm in depth were induced. B-mode images were obtain...

Microscopic objects including living cells on a planar substrate are investigated in bio-medical applications of scanning acoustic microscopy. Beside of the observation of lateral structures, the determination of sample properties such as density, sound velocity, and attenuation is desired, from which elastic properties can be derived. This can be achieved with the aid of the acoustic phase and magnitude contrast represented in a polar plot. For homogeneous and sufficiently planar objects the contrast in magnitude and phase is a function of the properties of the substrate and the coupling fluid, which both can easily be determined, and of the mechanical properties of the sample under observation. For observation in reflection and variable thickness of the sample the signal will depend on the actual thickness. This signature of the object can be fitted based on a conventional ray model for the sound propagating in the coupling medium and the sample. The model includes also the refraction and reflection at all interfaces between transducer, lens material, coupling fluid, object, and substrate. The method is demonstrated for a chitosan film deposited on a glass substrate. The scheme presented here is capable to reach a resolution of about and even below 1% for relevant quantities in applications involving imaging at 1.2 GHz in aqueous coupling fluids.

A digital seismic measuring chain is an electromechanical system able to record the lowest natural ground motions observable on Earth but also to measure signals from largest earthquakes. Its cornerstones are an inertial seismometer and a digitizer. As equipments available on the market don't answer to all seismological applications CEA/DASE (Commissariat a l'Energie Atomique/Departement analyse, surveillance, environnement) is interested in, it has developed the adequate digital seismic measuring chains. Today, the technologies used have reached their maturity. New sensing techniques need to be developed. Optical sensors are now widely used in vibrometry and displacement measurements. Such devices generally use interferometry to achieve subnanometric resolution with a large dynamic range. We have developed a prototype digital motion transducer from a Michelson interferometer in order to evaluate the potential of this technology for seismological applications. Tests were carried out to validate the operation of this transducer and to estimate its main characteristics for seismological applications. We focused on transducer motion range and intrinsic noise. Results are promising. Prototype intrinsic noise reaches levels as small as 100 fm/√Hz around 8 Hz and is better than that of present transducers all over the bandwidth of interest, motion range also. Interesting seismological applications can be considered leading to more accurate seismic measuring chains, easier to manufacture, deploy and operate.

This study was designed to evaluate the feasibility of using cylindrical ultrasound transducers mounted on a catheter for the ablation of cardiac tissues. In addition, the effects of ultrasound frequency and power was evaluated both using computer simulations and in vitro experiments. Frequencies of 4.5, 6, and 10 MHz were selected based on the simulation studies and manufacturing feasibility. These transducers were mounted on the tip of 7-French catheters and applied in vitro to fresh ventricular canine endocardium, submerged in flowing degassed saline at 37 degree C. When the power was regulated to maintain transducer interface temperature at 90-100 degree C, the 10-, 6-, and 4.5-MHz transducers generated a lesion depth of 5.9 +/- 0.2 mm, 4.6 +/- 1.0 mm, and 5.3 +/- 0.9 mm, respectively. The 10-MHz transducer was chosen for the in vivo tests since the maximum lesion depth was achieved with the lowest power. Two dogs were anesthetized and sonications were performed in both the left and right ventricles. The 10-MHz cylindrical transducers caused an average lesion depth of 6.4 +/- 2.5 mm. In conclusion, the results show that cylindrical ultrasound transducers can be used for cardiac tissue ablation and that they may be able to produce deeper tissue necrosis than other methods currently in use.

Undoubtedly voltage and current measurements under distorted conditions have recently gained more and more importance in the actual electric market; the deregulation acting in this field with the consequential liberalization and the augmented request of monitoring capabilities on the power quality from the power suppliers, is at the origin of an increased demand of measurement instruments of the various electric

This paper aims at exploring the potential of visible and near infrared (vis-NIR) spectroscopy for on-line measurement of soil pH, with the intention to produce variable rate lime recommendation maps. An on-line vis-NIR soil sensor set up to a frame was used in this study. Lime application maps, based on pH predicted by vis-NIR techniques, were compared with maps based on traditional lab-measured pH. The validation of the calibration model using off-line spectra provided excellent prediction accuracy of pH (R2 = 0.85, RMSEP = 0.18 and RPD = 2.52), as compared to very good accuracy obtained with the on-line measured spectra (R2 = 0.81, RMSEP = 0.20 and RPD = 2.14). On-line predicted pH of all points (e.g., 2,160) resulted in the largest overall field virtual lime requirement (1.404 t), as compared to those obtained with 16 validation points off-line prediction (0.28 t), on-line prediction (0.14 t) and laboratory reference measurement (0.48 t). The conclusion is that the vis-NIR spect...

A composite self-excited PZT-glass cantilever (4 mm in length and 2 mm wide) was fabricated and used to measure the binding and unbinding of model proteins. A key feature of the cantilever is that its resonant frequency is dependent on its mass. The fabricated cantilever has mass change sensitivity in liquid of 7.2 × 10−11 g/Hz. Resonant frequency change was measured as protein reacted or bound with the sensing glass cantilever surface. Protein concentrations, 0.1 and 1.0 mg/mL, which resulted in nanogram mass change were successfully detected. The mass change sensitivity gave a total mass change of 54 ± 0.45 ng for the binding of anti-rabbit IgG (biotin conjugated) to rabbit IgG immobilized cantilever and the subsequent binding of captavidin. The unbinding of anti-rabbit IgG and captavidin gave a total mass change of 54 ± 1.70 ng. Fluorescence based assays showed the combined mass of both proteins in the released samples was 54 ± 2.24 ng. The binding kinetics of the model proteins is modeled as first order. The initial binding rate constant of anti-rabbit IgG to rabbit IgG was 1.36 ± 0.02 (min (mg/mL))−1. The initial binding rate constant of captavidin to biotinylated anti-rabbit IgG was (2.57 × 10−1) ± 0.003 (min (mg/mL))−1. The significance of the results we report here is that millimeter-sized PZT-actuated glass cantilevers have the sensitivity to measure in real-time protein–protein binding, and the binding rate constant.