Wave propagation control in active acoustic metamaterials

Focus is on the design of an innovative class of tunable periodic metamaterials, conceived for the realization of high performance acoustic metafilters with settable real-time capabilities. In this framework the tunability is due to the presence of a piezoelectric phase shunted by a suitable electrical circuit with adjustable impedance/admittance. It follows that the acoustic properties of the metamaterial can be properly modified in an adaptive way, opening up new possibilities for the control of pass- and stop-bands.

Wafer-scale heterostructured piezoelectric bio-organic thin films

Piezoelectric biomaterials are intrinsically suitable for coupling mechanical and electrical energy in biological systems to achieve in vivo real-time sensing, actuation, and electricity generation. However, the inability to synthesize and align the piezoelectric phase at a large scale remains a roadblock toward practical applications. We present a wafer-scale approach to creating piezoelectric biomaterial thin films based on γ-glycine crystals. The thin film has a sandwich structure, where a crystalline glycine layer self-assembles and automatically aligns between two polyvinyl alcohol (PVA) thin films. The heterostructured glycine-PVA films exhibit piezoelectric coefficients of 5.3 picocoulombs per newton or 157.5 × 10−3 volt meters per newton and nearly an order of magnitude enhancement of the mechanical flexibility compared with pure glycine crystals. With its natural compatibility and degradability in physiological environments, glycine-PVA films may enable the development of transient implantable electromechanical devices.

Design of Piezoelectric Ultrasonic Transducer Based on Doped PDMS

The performance of the ultrasonic transducer will directly affect the accuracy of ultrasonic experimental measurement. Therefore, in order to meet the requirements of a wide band, a kind of annular 2-2-2 piezoelectric composite is proposed based on doped PDMS. In this paper, the transducer structure consisted of PZT-5A piezoelectric ceramics and PDMS doped with 3 wt.% Al2O3:SiO2 (1:6) powder, which constituted the piezoelectric composite. MATLAB and COMSOL software were used for simulation. Meanwhile, the electrode materials were selected. Then, the performance of the designed annular 2-2-2 ultrasonic transducer was tested. The simulation results show that when the polymer phase material of the piezoelectric ultrasonic transducer is doped PDMS, the piezoelectric phase and the ceramic substrate account for 70% of the total volume, the polymer phase accounts for 30% of the total volume, and the maximum frequency band width can reach 90 kHz. The experimental results show that the maximum bandwidth of −3 dB can reach 104 kHz when the frequency is 160 kHz. The results of the electrode test show that the use of Cu/Ti electrode improves the electrical conductivity of the single electrode. In this paper, the annular 2-2-2 transducer designed in the case of small volume had the characteristics of a wide frequency band, which was conducive to the miniaturization and integration of the transducer. Therefore, we believe that the annular 2-2-2 piezoelectric composite has broad application prospects.

Prototype Design of Cement/Emulsified Asphalt Based Piezoelectric Composites and its Potential Application in Vehicle Speed Sensing

Piezoelectric composites (PC) embedded in pavement have shown great potential in traffic information sensing. As the main form of transportation, the road is the source of much traffic information including vehicle load information. The research into PC can supplement the collection of traffic information used in the development of intelligent technologies and provide effective solutions to problems existing in the process of information gathering. In this study, a 2-2 cement/emulsified asphalt-based PC was prepared with the cutting-filling method. To optimize the PC preparation, the effects of the volume fraction of the piezoelectric phase and the matrix phase composition on the piezoelectric properties of the PC were investigated by employing the finite element method. The results indicated that the smaller the volume fraction of the piezoelectric phase, the higher the voltage output of the PC, and the higher the sensitivity to external load, but the greater the stress concentration at the interface between the piezoelectric phase and the matrix phase. In addition, the greater the amount of emulsified asphalt in the matrix phase, the higher the voltage output of the PC. However, a higher content of emulsified asphalt will undermine the fluidity of the matrix phase. Based on the simulation analysis, performance optimization of the cement/emulsified asphalt PC was achieved. According to the voltage output characteristic of PC under a moving load, a placement scheme of PCs in the asphalt pavement was also proposed, which enables vehicle speeds to be be sensed with high precision.

Enhancement of piezoelectric properties of lithium niobate thin films by different annealing parameters

Piezoelectric materials with useful properties find a wide range of applications including opto- and acousto- electronics. Lithium niobate in the form of a thin film is one of those promising materials and has a potential to improve ferroelectric random access memories devices, optical waveguides or acoustic delay lines by virtue of its physical characteristics, e.g. electro-optic coefficient, acoustic velocity, refractive indices etc. The key challenge to overcome is lithium nonstoichiometry as it leads to the appearance of parasite phases and thus aggravates physical and structural properties of a film. According to literature data, in order to obtain microcrystalline piezoelectric phase in previously amorphous films a set of methods is used. In our case we tried to synthesize LN films using congruent target and non-heated silicon substrate and then attain the piezoelectric phase by different annealing parameters. Afterwards LN films were compared to the ones synthesized on the silicon substrate with an additional buffer layer of platinum. Samples were studied by scanning probe microscope. Self-polarization vectors were defined. Based on domain structure images, the histograms of distribution of piezoresponse signals were built.

Optimization and simulation analysis of structure parameters of OPCM ultrasonic longitudinal wave actuating element

The force-electric coupling relationship of the mechanical and electrical properties of piezoelectric composites has been the main factor in the research and development of piezoelectric composites in practical application. A novel orthotropic piezoelectric composite material (OPCM) element is studied in this paper. The properties of the piezoelectric phase and the polymer phase and the influence of the geometrical dimensions of the OPCM on the longitudinal wave drive element are analyzed from the perspective of mechanics and electric power, respectively, and the structural design is optimized. This provides a theoretical basis for the development of OPCM and of new longitudinal ultrasonic phased array actuators.