Yaoyao Cui

Temperature distribution of piezoelectric transformer with heat couple component using finite element method

The temperature field of a piezoelectric transformer with heat couple component are analyzed at steady state conditions in this paper. The contour extensional vibration mode of the transformer is determined by impedance simulation analysis and experiment result. Mechanical vibration losses, piezoelectric losses, dielectric losses are considered for a piezoelectric transformer. In order to verify the calculated temperature results, the piezoelectric transformer s temperature distributions were measured by the infrared thermometry. The experiment results show a good uniformity with the calculation results. For the piezoelectric transformer with heat couple component, friction heat were considered as another heat source of temperature distribution. The temperature distribution results show the heat couple component depresses temperature gradient of the piezoelectric transformer and improves piezoelectric material utilization rate effectively.

A muliple outputs of piezoelectric transformer based on the stress distribution

A new type of piezoelectric transformer which is based on the stress distribution of the piezoelectric transformer to change the output voltage is presented. In this paper, we verified the feasibility of the principle of the new piezoelectric transformer from the simulation and experiment. The experiment results show a good consistent with the theoretical analysis. The designed piezoelectric transformer is very capable of multiple output and the structure is simple. The proposed piezoelectric transformers can provide applications in multiple output of piezoelectric transformers of all the vibration mode.

A micro dual-frequency transducer based on contour-extensional vibration and thickness mode

This paper presents a single piezoelectric transducer with dual-frequency characters by utilizing contour-extensional mode and thickness mode. A 2.5 MHz and 8.5 MHz frequency transducer prototype is designed by Finite element method (FEM) analyses and verified by experiment. Performance of the transducer is then evaluated through the measurement of admittance curves and pulse-echo responses. It’s demonstrated experimentally that the proposed transducer has -6dB bandwidth of 39.4% @1.0 Vpp at 2.4 MHz and 34.6% @1.1 Vpp at 8.9 MHz, respectively. The proposed dual-frequency transducer has potential applications in vivo thrombolytic therapy and ultrasound-guide of pedicle screws.This paper presents a single piezoelectric transducer with dual-frequency characters by utilizing contour-extensional mode and thickness mode. A 2.5 MHz and 8.5 MHz frequency transducer prototype is designed by Finite element method (FEM) analyses and verified by experiment. Performance of the transducer is then evaluated through the measurement of admittance curves and pulse-echo responses. It’s demonstrated experimentally that the proposed transducer has -6dB bandwidth of 39.4% @1.0 Vpp at 2.4 MHz and 34.6% @1.1 Vpp at 8.9 MHz, respectively. The proposed dual-frequency transducer has potential applications in vivo thrombolytic therapy and ultrasound-guide of pedicle screws.

Acoustic particle sorting by integrated micromachined ultrasound transducers on polymer-based microchips

Ultrasonic standing waves (USWs) particle sorting has shown great potential to develop diverse applications in biotechnology and medical research due to its ability to offer non-contact, label-free particle manipulation. Currently, most reported on-chip acoustic particle sorters rely on high Q-value materials and elaborate geometry designs, which make these devices not easy to build and unsuited for mass fabrication. In this work, we propose a novel two-stage acoustic particle sorting strategy with the advantages of operating on low-cost polymer-based microchips and using integrated micro-machined piezoelectric transducers (PZTs).

An intracranial implantable ultrasound device for seizure mapping

Epilepsy is the third most commonly diagnosed neurological disorder. For drug-resistant patients, epilepsy surgery is the only option. The outcome of epilepsy surgery largely depends on an accurate mapping of epileptogenic zone. In clinic, this is done with subdural electrode array to monitor the Electrocorticography (ECoG) with a disappointing low spatial resolution of ∼ 1cm. As a result, the cure rate of neocortical epilepsy can barely reach ∼ 30%. Recent study showed that the neurovascular based CBV(Cerebral Blood Volume) increases spatially overlapped with seizure focus and functional ultrasound imaging can provide high resolution 3D maps of seizure focus in animal models. To apply ultrasound imaging techniques in clinic, we propose to develop implanted ultrasound transducers 3mm∗1.5mm∗0.8mm which can be incorporated with the electrode array to record the CBV changes during seizure onset. This device can provide high resolution 3D seizure maps to guide the epilepsy surgery.

Temperature distribution analysis of piezoelectric transformer with heat couple component

ABSTRACT The use of a heat transfer structure can effectively improve the power of a piezoelectric transformer (PT). A heat couple component (HCC) serves as the core element in the heat transfer structure and improves temperature distribution of PT. The finite element method and experimental measurement are conducted to determine the influence of HCC to the temperature distribution of PT in this study. The heat sources are mechanical vibration, piezoelectric, dielectric losses of PT, as well as the friction heat. The thermal contact conductance coefficient between HCC and PT is determined by the asymptotic waveform evaluation method.

A shear wave propagation tracking method based on Modal Assurance Criterion in acoustic radiation force impulse imaging

Changes in stiffness of soft tissue are a sign of abnormalities. Therefore, techniques capable of estimating stiffness or elasticity of tissue can contribute in the assessment of various diseases. Shear wave elasticity imaging (SWEI) is a transient method of biomedical ultrasound elastography. SWEI can be performed using a single ultrasound transducer by applying an impulsive acoustic radiation force excitation to generate shear waves, whose propagation can be monitored using ultrafast imaging with plane wave in the region of interest (ROI). In the present study, Field II was used to simulate ultrasound radiation force field generated by a linear array transducer. And the motion caused by a high intensity tone burst in a homogenous viscoelastic medium was calculated using the finite element method (FEM). Then the Modal Assurance Criterion (MAC) method was presented to track the propagation of the shear wave. To verify the simulation results, an experiment was set with a High Intensity Focused Ultrasound (HIFU) transducer and SonixTouch and DAQ system to evaluate the validity and efficiencies of the MAC method. Finally, an image of shear wave propagation can be reconstructed from the delays and amplitudes of the echoes.

A graphic processing unit based intravascular ultrasound (IVUS)

A practical intravascular ultrasound system prototype is presented. The system is designed to work in compliance with high frequency interventional ultrasound imaging catheter, which has a center frequency as high as 60MHz. Differ from former architecture, a graphic processing unit is utilized as a primary processing component to accomplish most of the crucial computations in this machine, based on which, real time algorithm verification becomes much easier. This paper explains the motivation to start the project, introduces the hardware architecture that have been adopted and specifies the processing flow cooperate with this architecture. The time budget of experimental algorithm running on this prototype is analyzed and few images obtained with it are illustrated.

Effect of temperature and wavelength on photoacoustic signal

In this paper, the effect of temperature and wavelength on photoacoustic signals was qualitatively studied.