Zhangjian Li

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).

High frequency Self-focusing transducer fabricated by a laser engraving technique

High frequency transducers (>15 MHz) have been widely used in small animal ultrasound, ophthalmic ultrasound, skin ultrasound and intravascular ultrasound et. al. The images obtained by a plane transducer have lower resolution and sensitivity compared with a focusing one. It is usually hard to make the focusing transducer with micro size, short focal length and high frequency. For solving these problems, self-focusing transducers were developed, which pattern a Fresnel half-wave bands on the piezoelectric materials surface as the electrode. Using this method can achieve transducers with micro size (∼1–2 mm in diameter), short focal length (∼350 μm) and high frequency (>100 MHz). But this method need wire lead to contact each ring separately, so it is hard to keep every annular ring complete. And the instrument accuracy requirements are quite strict. Therefore, based on recent progress on laser cutting, a high frequency self-focusing piezoelectric transducer using laser cutting technique is developed, which engraved the piezoelectric ceramic into annular rings to form Fresnel half-wave-band sources.

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.

A High Frequency Geometric Focusing Transducer Based on 1-3 Piezocomposite for Intravascular Ultrasound Imaging

Due to the small aperture of blood vessel, a considerable disadvantage to current intravascular ultrasound (IVUS) imaging transducers is that their lateral imaging resolution is much lower than their axial resolution. To solve this problem, a single-element, 50 MHz, 0.6 mm diameter IVUS transducer with a geometric focus at 3 mm was proposed in this paper. The focusing transducer was based on a geometric-shaped 1-3 piezocomposite. The impedance/phase, pulse echo, acoustic intensity field, and imaging resolution of the focusing transducer were tested. For comparison, a flat IVUS transducer with the same diameter and 1-3 piezocomposite was made and tested too. Compared with their results, the fabricated focusing transducer exhibits broad bandwidth (107.21%), high sensitivity (404 mV), high axial imaging resolution (80 μm), and lateral imaging resolution (100 μm). The experimental results demonstrated that the high frequency geometric focusing piezocomposite transducer is capable of visualizing high axial and lateral resolution structure and improving the imaging quality of related interventional ultrasound imaging.

A study on the equivalent circuit of longitudinal vibration piezoelectric transformers with contacted heat transfer device

In this paper, the electrical equivalent circuits of the piezoelectric transformer (PT) with heat transfer system (HTS) had been studied. A heat transfer model of the longitudinal vibration PT had been built and an experiment study on the equivalent circuit model of the PT with HTS was proposed. this work provides a useful information for the application of piezoelectric transformer in high-power condition.

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.

Fabrication and performance of a micro 50-MHz IVUS Transducer based on a 1-3 composite with geometric focusing

In this paper a micro 50-MHz IVUS Transducer based on a 1-3 piezo-composite with geometric focusing was presented. The using 1-3 PZT composite material was developed in our laboratory with 12 um kerfs and 18 um pillars. The transducer was focused in the elevation direction by geometrically shaping the composite material using a PTEF ball with a 5 mm radius. After the silver conductive backing layer was cured, the transducer was divided into the size of 1.0 × 1.0 mm. The final fabricated transducer was fixed in a needle tip, and its diameter is 9F. According to the testing results with our homemade IVUS system, its lateral resolution is about 120 um, which effectively improved the lateral resolution of current IVUS system.

Design of micromachined self-focusing piezoelectric composite ultrasound transducer

Based on the Fresnel half-wave band interference, a micromachined self-focusing piezoelectric composite ultrasound transducer was proposed in this paper. The theoretical analysis was deduced based on the concept of constructive interference of acoustic waves and electromechanical response of piezoelectric composites. The calculated and simulation results showed that it combined the advantages of composite transducer and plate self-focusing transducer, and can achieve high electromechanical coupling coefficient, low acoustic impedance, high intensity, short focal length and micro size. Because it was based on the micro-electromechanical systems, the fabrication process was accurate and controllable, which made it have good potential for interventional ultrasound imaging, cellular microstructure imaging, skin cancer detection and industrial nondestructive testing applications.