A high-frequency linear ultrasonic array utilizing an interdigitally bonded 2-2 piezo-composite

A high frequency ultrasonic phased array is shown to be capable of trapping and translating microparticles precisely and efficiently, made possible due to the fact that the acoustic beam produced by a phased array can be both focused and steered. Acoustic manipulation of microparticles by a phased array is advantageous over a single element transducer since there is no mechanical movement required for the array. Experimental results show that 45 lm diameter polystyrene microspheres can be easily and accurately trapped and moved to desired positions by a 64-element 26 MHz phased array. Similar to the trapping mechanism of optical tweezers, 1,2 when acoustic gradient force (from refraction) exceeds scattering force (from reflection), an object can be attracted and trapped by a tightly focused ultrasound beam. 3,4 The direct exposure of cells to the optical trapping laser beam may induce photodamage, 5 however, it was demonstrated that the thermal and mechanical effects in acoustic trapping are negligible when the energy is maintained in the diagnostic range. 6 Recently, high frequency single element ultrasonic transducers have been used to carry out single beam acoustic trapping. In these approaches, in order to move a trapped microparticle, a mechanical scanning stage has to be utilized to move the transducer and its focus. [7][8][9] In this paper, we present results showing that it is possible to trap and move microparticles with a high frequency ultrasonic linear phased array without mechanical movement of the transducer.An ultrasonic linear phased array transducer (or simply called phased array) is a transducer consisting of multiple small transducer elements, which usually are rectangular in shape and arranged on a straight line. Ultrasonic phased arrays have been widely used in biomedical imaging 10 and industrial nondestructive testing. 11 The advantages of phased array transducers over conventional single element transducers are their capabilities of steering the ultrasound beam into different directions and/or changing the focus at different depths, not by mechanically moving transducers but by applying electronic phase shift/time delays on the transmitting pulses to the elements of the phased array. Eliminating the mechanical movement of the transducer increases the system reliability and the speed of the experiment.A customized lead zirconate titanate (PZT-5 H) 2-2 composite linear phased array transducer was fabricated with traditional array technology. 12 The center frequency of the phased array is 26.3 MHz. The array has 64 small elements arranged on a straight line in the azimuthal direction. The elevation length and lateral width of one element are 2 mm and 24 lm, respectively. The kerf between two adjacent elements is 6 lm. The F-number of the phased array is 2.6.A field programmable gate array (FPGA) based 64-channel transmit beamformer and a 64-channel pulser were also developed to drive the phased array. The transmit beamformer could send out 128 (64 pairs) delayed trigger signals, 13 with whic...

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“…12 The center frequency of the phased array is 26.3 MHz. The array has 64 small elements arranged on a straight line in the azimuthal direction.…”

mentioning

confidence: 99%

Acoustic trapping with a high frequency linear phased array

et al. 2012

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“…[7] Fig. 6 shows backscattered electron images of polished cross sections of a 2-2 composite manufactured from 3257HD.…”

Section: Damaged Surface Layer Modelmentioning

confidence: 99%

Piezoelectric ceramics in ultrasound

Stranford¹,

Vencill²,

Williams³

et al. 2014

2014 IEEE International Ultrasonics Symposium

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3203HD, a piezoelectric ceramic material manufactured by CTS, was developed in the 1980s to meet the requirements for medical ultrasound. This high dielectric constant, high electromechanical coupling coefficient material, which is known for its consistency and reproducibility, became the reference material for medical ultrasound imaging and is still used in many transducers today.However, material requirements for ultrasonic imaging have evolved leading to the need for new materials. In particular there has been a demand for higher dielectric constant materials and materials that offer good mechanical strength and performance at dimensions less than 50 microns. There are often property trade-offs to be considered when developing new materials. Substitution of various lanthanide ions into an existing piezoelectric material formulation shows that the dielectric constant decreases and the Curie point increases with increasing atomic number for the lanthanide ion. Dielectric properties are often less than predicted as the material cross-section decreases. Polished cross sections of a 2-2 composite structure reveal surface damage that is one grain deep on the ground and diced surfaces. An empirical model suggests that the effective dielectric constant of the damaged surface is lower than the bulk material, which causes the measured capacitance to be lower than expected.

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“…Traditionally, array transducers with center frequency less than 50 MHz have been fabricated successfully by mechanical dicing or laser-dicing technique [7][8][9][10]. In the practical application, since the diameter of the catheter in intravascular ultrasound (IVUS) system is considerably small (usually less than 1 mm), it is challenging to fabricate such miniaturized transducers with high center frequency using mechanical dicing and filling method [11][12][13][14].…”

Section: Introductionmentioning

confidence: 99%