Abstract
We developed and investigated a particular geometry of transducers, emulating the shape of bats’ cochlea, to transmit and receive ultrasounds in the air. Their design involved the use of polyvinylidene fluoride (PVDF) as a piezoelectric material, thanks to its excellent conformability and flexibility. This material offers the primary requirements for sensing devices in applications such as sonar system or energy harvesting technology. The piezo film was folded according to both the Archimedean and Fibonacci spirals, and their performances were investigated in the frequency range from 20 kHz up to more than 80 kHz. The finite element analysis (FEA) of the proposed transducers highlighted the presence of multiple resonance vibrations, proved by the experimental measurements of the equivalent electric impedance and frequency response. Far-field radiation patterns demonstrated, horizontally and vertically, omnidirectional properties both as transmitters and receivers. All was enough to establish the best validity of the spiral shaped transducers for applications based on the bio sonar principle.
Highlights
Distance ranging evaluations using sonar systems are performed, in air or underwater, in a myriad of applications, in biomedical, civil, and military areas [1,2,3]
The shape of the cochlea has been associated with the Archimedean and Fibonacci spirals [19,20], and this prompted us to design transducers folded according to these geometries for in-air transmission and reception at low-frequency (20–80 kHz) US
polyvinylidene fluoride (PVDF) thin films were folded according to two peculiar geometries: those of the Archimedean cochlea
Summary
Distance ranging evaluations using sonar systems are performed, in air or underwater, in a myriad of applications, in biomedical, civil, and military areas [1,2,3]. Previous investigations were directed towards reproducing US at certain fixed frequencies for specific applications; because the most dominant technologies allowed the manufacture of piezoelectric transducers only in the frequency range of 40–50 kHz. Direct piezoelectric effect involves the conversion from mechanical into electrical energy. The supremacy of polyvinylidene fluoride (PVDF) has been widely demonstrated for the design and manufacturing of short-range US transducers in the air from 30 kHz up to 100 kHz, which is the same frequency range used by bats [8,9,10,11,12]. The PVDF film was arranged according to various geometries [14,15,16], widening the operating frequency band to no more than 11 kHz
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