Sensitivity of polyvinylidene fluoride films to mechanical vibration modes and impact after optimizing stretching conditions

Optimizing solvent dipole moment enables PVDF to improve piezoelectric performance

The all-trans conformation (β-phase) possesses a significant impact on the piezoelectric polymer polyvinylidene fluoride (PVDF). Inducing more molecular chain [-CH2-CF2-]nto form all-trans conformation is one of the biggest obstacles for manufacturing high-performance piezoelectric sensing devices. Herein, the continuous vacuum technology is used to modulate the polarity of binary solvents by the proportion of the lower solvent. The regulated solvent forms a high dipole moment, an interaction between the dipole ofβ-phase and the dipole moment makes the phase reversal in PVDF. Fourier transform infrared spectroscopy, piezoelectric constant test and other characterization results show that when the weakly polar acetone and the strongly polar solvent DMF reach a ratio of 4:6, the pure PVDF film possesses high piezoelectricity (d33∼ -44.8 pC N-1) and strong self-polarization. Additionally, the A4D6device exhibits high sensitivity (S1= 0.182 V/N, 0.5 N ∼ 30 N), driven capability (0.49 mW m-2), and reliability during the electrical tests as a pressure device. This work provides an effective and cost-effective route of optimizing the solvent's polarity to improve the piezoelectric characteristics of the polymer.

A Review of Acoustic Impedance Matching Techniques for Piezoelectric Sensors and Transducers

The coupling of waves between the piezoelectric generators, detectors, and propagating media is challenging due to mismatch in the acoustic properties. The mismatch leads to the reverberation of waves within the transducer, heating, low signal-to-noise ratio, and signal distortion. Acoustic impedance matching increases the coupling largely. This article presents standard methods to match the acoustic impedance of the piezoelectric sensors, actuators, and transducers with the surrounding wave propagation media. Acoustic matching methods utilizing active and passive materials have been discussed. Special materials such as nanocomposites, metamaterials, and metasurfaces as emerging materials have been presented. Emphasis is placed throughout the article to differentiate the difference between electric and acoustic impedance matching and the relation between the two. Comparison of various techniques is made with the discussion on capabilities, advantages, and disadvantages. Acoustic impedance matching for specific and uncommon applications has also been covered.

A Review of Electric Impedance Matching Techniques for Piezoelectric Sensors, Actuators and Transducers

Any electric transmission lines involving the transfer of power or electric signal requires the matching of electric parameters with the driver, source, cable, or the receiver electronics. Proceeding with the design of electric impedance matching circuit for piezoelectric sensors, actuators, and transducers require careful consideration of the frequencies of operation, transmitter or receiver impedance, power supply or driver impedance and the impedance of the receiver electronics. This paper reviews the techniques available for matching the electric impedance of piezoelectric sensors, actuators, and transducers with their accessories like amplifiers, cables, power supply, receiver electronics and power storage. The techniques related to the design of power supply, preamplifier, cable, matching circuits for electric impedance matching with sensors, actuators, and transducers have been presented. The paper begins with the common tools, models, and material properties used for the design of electric impedance matching. Common analytical and numerical methods used to develop electric impedance matching networks have been reviewed. The role and importance of electrical impedance matching on the overall performance of the transducer system have been emphasized throughout. The paper reviews the common methods and new methods reported for electrical impedance matching for specific applications. The paper concludes with special applications and future perspectives considering the recent advancements in materials and electronics.

Transient dynamic distributed strain sensing using photonic crystal waveguides

This paper presents a new type of one-dimensional photonic crystal (PC) waveguide sensor and a technique for prediction of transient strain response accurately. The PC waveguide is integrated on a silicon substrate. We investigate the effect of non-uniform strain localization on the optical signal and use that information to capture the transient strain. Wavelength shift due to distributed strain field is modeled by incorporating the mechanically deformed geometry and photo-acoustic coupling through Pockels effect in a finite element formulation. We demonstrate the advantages of using our proposed method, where multiple spectral peak shift is used instead of single peak shift in order to improve sensing output accuracy and also to estimate the sensor parameter regressively, where the signal's bandwidth is limited. The maximum sensitivity of the waveguide sensor in terms of wavelength shift is estimated to be 0.36 pm/μstrain in single-peak-based sensing, whereas the proposed adaptive multispectral estimation scheme shows an enhanced sensitivity of 4.029 pm/μstrain.