Evaluation of adhesive-free focused high-frequency PVDF copolymer transducers fabricated on spherical cavities

Abstract

A layer-by-layer deposition method for fabricating a focused ultrasonic transducer from piezoelectric copolymers has been developed. The fabrication process involves engraving a spherical cavity of 2 mm diameter on polyethyleneimines (PEI) polymer substrate. Surface roughness of the engraved spherical cavity is measured and compared with simulated line scan. Then, the transducer response was investigated by observing the acoustic pulse reflection from the glass plate used as reflector in a focal point. The average central frequency responses were measured to be 48.5 MHz, with a lower and upper −6 dB frequencies of approximately 25 and 76.5 MHz, yielding a bandwidth of 94.2%. A scanning hydrophone system has been employed to determine the focal zone of the transducer and compared with simulation using COMSOL Multiphysics. Two-dimensional surface scanning was performed on the test sample to provide the ultrasonic imaging of the transducer prototype and compare the image with commercial PVDF transducer with a center frequency of (48.5 ± 1) MHz.

Advances in development of Pb-free piezoelectric materials for transducer applications

“…. 108) The fabrication process provided a novel method to build HF PVDF without introducing additional adhesive layers for material bonding, and two-dimensional surface scanning also demonstrated the potential of PVDF for imaging applications. Furthermore, an acoustic image of a coin with detailed patterns also showed the great ability of the HF PVDF transducer in high resolution acoustic imaging.…”

High-Frequency Acoustic Imaging Using Adhesive-Free Polymer Transducer

“…For each transducer, both Ricker and chirp-coded pulses were used as an excitation pulse, and the recorded time series from these pulses were averaged 16 times to obtain noise reduction. The average central frequency of the transducer was measured to be (48.5 ± 1) MHz, with lower and upper −6 dB frequencies of approximately 25 and 76.5 MHz, yielding a bandwidth of 94.2% [ 33 ].…”

“…The focal point of the polymer transducer was found to be located approximately at 2.5 mm from the cavity of the transducer. In order to confirm the measurement of the focal point, a simulation was performed using COMSOL (5.2) multiphysics software in our previous paper [ 33 ]. The experimental setup is given as below.…”

SiO2 Nanoparticles Incorporated Poly(Vinylidene) Fluoride Composite for Efficient Piezoelectric Energy Harvesting and Dual‐Mode Sensing

“…Previous work on the implementation of wearable pressure and temperature sensors utilized a wide range of materials, including thin metal films, aerogels, hydrogels, conductive composites, and liquid metals. [9,11,[15][16][17][18] Among them piezoelectric polymer-based materials have attracted extensive research attention in wearable electronics, as they can enable self-powered devices. These piezoelectric sensors produce piezopotential by strain-induced polarization under the variation of applied external pressure.…”