Performance investigation of piezoelectric PVDF-TrFE polymer for it's mechanical and electrical response and use as vibration sensor

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Date
2025-03-04
Authors
Riaz, Naeem
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Abstract

Piezoelectric polymers, such as PVDF-TrFE, are increasingly studied for their potential to replace traditional ceramic based piezoelectric materials due to their flexibility, ease of processing, and strong adhesion properties. This study focuses on PVDF-TrFE with a 75/25 molar concentration, emphasizing the enhancement of the β-phase to improve piezoelectric output. The research explores various techniques to increase the β-phase without requiring extensive stretching or polling processes. Notably, the addition of the TrFE co-polymer to PVDF negates the need for such processes, inherently boosting piezoelectric performance. The experimental study utilized PVDF-TrFE dissolved in two different solvents: MIBK (Methyl Isobutyl Ketone) and DMSO (Dimethyl Sulfoxide). In the initial phase of the experiments, piezoelectric solutions based on MIBK and a combination of MIBK and DMSO were spin-coated onto flexible KAPTON cantilevers and annealed to form thin films. The mechanical properties were then assessed using a vibration test system. It was observed that films created with MIBK alone exhibited higher vibrational amplitudes than those formed with a mixture of MIBK and DMSO. Additionally, higher concentrations of PVDF-TrFE resulted in greater vibrational amplitudes, suggesting a direct correlation between polymer concentration and mechanical responsiveness. Notably, the films made by a 1.25% MIBK+ DMSO based polymer solution produced an equivalent sensitivity to the films made by a 3% polymer solution. The equivalency is due to the presence of DMSO (polar nature) solvent and its ability to form long chains during the baking process. In contrast, the latter solution produced thicker films than the former due to the increased quantity of polymer. The performance of laboratory based vibration sensors fabricated using PVDF-TrFE was compared with existing ceramic based devices and commercial vibration sensors. The results indicated that PVDF-TrFE sensors generated comparable, if not higher, piezoelectric voltages than their ceramic counterparts. This finding underscores the potential of polymer based sensors in practical applications, offering advantages in flexibility and adhesion without sacrificing performance. Further experiments involved fabricating a 5 x 2 mm cantilever on a PCB using a laser cut process. This cantilever responded to acoustic signals ranging from 400 Hz to 1200 Hz and produced a 0.011 V output voltage during vibration tests. Another U-shaped sensor, incorporating electroplated copper, spin-coated PVDF-TrFE, and silver sputtering, was tested as a Lorentz force actuator and sensor. The sensor exhibited responsiveness to magnetic elds and sinusoidal voltages, highlighting its multifunctional capabilities. Additionally, a vibration sensor was made on a bearing surface and subjected to motor induced vibrations, demonstrating a clear output signal, driven purely by the motor's rod vibrations.

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Piezoelectric sensor, PVDF-TrFE
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