Evaluation of adhesive-free crossed-electrode poly(vinylidene fluoride) copolymer array transducers for high frequency imaging

Abstract

High frequency crossed-electrode transducers have been investigated, both as single and dual layer transducers. Prototypes of these transducers were developed for 4 crossed lines (yielding 16 square elements) on a polymer substrate, using a layer-by-layer deposition method for poly(vinylidene fluoride–trifluoroethylene) [P(VDF–TrFE)] with intermediate sputtered electrodes. The transducer was characterized using various methods [LCR analyzer, a pulse–echo experimental setup, and a numerical Finite element method (FEM) model] and evaluated in terms of uniformity of bandwidth and acoustical energy output. All 16 transducer elements produced broad-banded ultrasonic spectra with small variation in central frequency and −6 dB bandwidth. The frequency responses obtained experimentally were verified using a numerical model.

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

“…Here, most of the studies showed λ/4 resonance mode with the heavy backing material. Our previous studies of unfocused transducer on polyethyleneimine (PEI) substrate showed a resonance frequency at ∼λ/2 which is higher than λ/4 resonance mode [18]. Ferroelectric PVDF and its copolymer PVDF trifluoroethylene P(VDF-TrFE) are widely used to make ultrasonic sensors and transducers [16][17][18][19][20][21][22][23][24][25][26][27][28][29].…”

Numerical and Experimental Evaluation of High-Frequency Unfocused Polymer Transducer Arrays

“…The application of P(VDF-TrFE) copolymer transducers has also been broadened from hydrophone fabrication to ultrasonic imaging of the microstructures of tissue, in, for example, dermatology, ophthalmology, and bio-microscopy [ 13 , 14 , 15 , 16 , 17 ]. At the same time, these piezoelectric polymers are very suitable materials for achieving high frequencies with a large bandwidth for ultrasonic sensors and transducers [ 18 , 19 , 20 , 21 , 22 , 23 ]. The flexible piezoelectric film of PVDF and its copolymer are fabricated by techniques such as spin coating, hot pressing, stamping, and spraying on a flat substrate [ 11 , 24 , 25 , 26 , 27 , 28 , 29 ].…”

Chirp coded ultrasonic pulses used for scanning acoustic microscopy

“…In order to overcome the bandwidth issue related in chirp imaging, we here propose using a polymer based transducer for the acoustic imaging. Polymer based piezoelectric materials like PVDF and P(VDF-TrFE) are very suitable for achieving high frequencies and large bandwidths for ultrasonic sensors and transducers as shown in several applications [19][20][21][22][23][24][25][26]. The aim of this work has therefore been to investigate experimentally how longer chirped pulses can be used to improve the image quality in SAM systems.…”