Theory and operation of 2-D array piezoelectric micromachined ultrasound transducers

Abstract

Piezoelectric micromachined ultrasound transducers (pMUTs) are a new approach for the construction of 2-D arrays for forward-looking 3-D intravascular (IVUS) and intracardiac (ICE) imaging. Two-dimensional pMUT test arrays containing 25 elements (5 x 5 arrays) were bulk micromachined in silicon substrates. The devices consisted of lead zirconate titanate (PZT) thin film membranes formed by deep reactive ion etching of the silicon substrate. Element widths ranged from 50 to 200 microm with pitch from 100 to 300 mum. Acoustic transmit properties were measured in de-ionized water with a calibrated hydrophone placed at a range of 20 mm. Measured transmit frequencies for the pMUT elements ranged from 4 to 13 MHz, and mode of vibration differed for the various element sizes. Element capacitance varied from 30 to over 400 pF depending on element size and PZT thickness. Smaller element sizes generally produced higher acoustic transmit output as well as higher frequency than larger elements. Thicker PZT layers also produced higher transmit output per unit electric field applied. Due to flexure mode operation above the PZT coercive voltage, transmit output increased nonlinearly with increased drive voltage. The pMUT arrays were attached directly to the Duke University T5 Phased Array Scanner to produce real-time pulse-echo B-mode images with the 2-D pMUT arrays.

Experiment and simulation validated analytical equivalent circuit model for piezoelectric micromachined ultrasonic transducers

“…Despite achievements in pMUT research [1], [3], [4], [12]- [18], predictive modeling and optimization capabilities are limited in improving reduced effective electromechanical coupling k 2 ef f and bandwidth in fabricated devices. In the most mature recent projects, fabricated pMUT designs are based heavily on geometry specific finite element models [19] with analytical models commonly limited to resonant frequency determination [4], [16], [20], [21]. A lack of available models leading to performance shortcomings demonstrate a need for more robust, fundamental understanding of pMUT performance.…”

A Column-Row-Parallel ASIC architecture for 3D wearable / portable medical ultrasonic imaging

“…The piezoelectric micromachined ultrasonic transducers (PMUTs) also emerge as another possible 2D transducer solution for 3D imaging [47][48][49][50][51]. It combines the piezoelectric material with micromachining techniques, trying to exploit the benefits from both worlds.…”

“…The piezoelectric material tends to provide transduction with relatively high efficiency and good linearity, while the micromachining process helps 35 create fine-pitched 2D arrays with higher yield and reliability. As a technology in its early research phase, it has shown initial success of a 5x5 working array [47]. More works are being done to address problems with this technology, including how to enhance the device bandwidth to generate images with better axial resolution; and how to reduce the intrinsic device parasitic capacitance from the high permittivity of the piezoelectric material [48,49,51].…”

Effect of Annealing Process on Properties of Pb(Zr0.52Ti0.48)O3Thin Films Prepared by Sol-Gel Method

“…As a important functional materials, Pb(Zr 0.48 Ti 0.52 )O 3 (PZT) films have been widely used in micro acoustic sensor, non-volatile memory, uncooled infrared detectors for their excellent ferroelectric, piezoelectric, pyroelectric properties [1][2][3][4]. The study has shown that the properties of PZT films depend greatly on their orientation.…”