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Discover the science and applications of piezoelectric materials
In 10 Seconds? Piezoelectric materials are receiving more and more attention these days due to their unique ability to convert a mechanical force into an electrical charge; this is known as the direct piezoelectric effect. However, what makes these materials even more incredible is that this process is reversible. Meaning, if an electric charge is placed on the material it will generate a mechanical stress; this is known as the in-direct piezoelectric effect.
Don’t believe it? Browse through the selected articles and take a look for yourself. One particular study has looked at implementing ‘smart highways’ to harvest electricity – this involves utilising the direct piezoelectric effect (mechanical force into electrical charge).
Where are they used? Piezoelectric applications are found in ever day life such as; cigarette lighters, gas hobs (the knob you press to light the gas) and computers. However, they are extensively used within the automotive industry, mostly used as sensors e.g. an airbag sensor. Additionally, piezoelectric materials are also used in the medical and military industries.
The science behind piezoelectrics
To obtain the piezoelectric effect successfully the material must initially undergo a poling process. Meaning, the dipoles within the crystal structure go from randomly orientated to aligned, this alignment is due to a high electrical charge being applied. When the charge is removed, the dipoles within the crystal structure remain near enough aligned. Alignment of the dipoles is critical; this is because if a mechanical force is applied on the material and the dipoles are randomly orientated then the piezoelectrical effect will be negligible.
Abstract: Coated microneedles have shown immense promise for use in transdermal delivery and diagnostics, due to their ability to painlessly breach the skin's outermost stratum corneum layer and interact with the epidermal layers immediately beneath. In this work, we use an off-the-shelf piezoelectric dispensing system to demonstrate the feasibility of depositing material directly on to steeply-sloping microneedle sidewalls, without the need for specific needle array positioning or material pretreatment. In the first instance, an analysis of deposition accuracy shows that over 95% of dispensed droplets land within 20 μm of the target. Through the use of sequential dispense and drying steps, 3.2 nL of a model drug formulation has been deposited onto both silicon and polymeric microneedles with highly sloped (71°) sidewalls; these are the steepest surfaces that have been coated to date. Finally, preliminary ex-vivo skin studies have been performed to show that the material may be successfully transferred from the needle to skin. Despite the smooth surfaces, ultrasharp tips and steep sidewalls of these structures, piezoelectric dispense techniques are clearly feasible for microneedle coating and may offer a promising alternative to conventional coating processes.
Pub.: 16 Feb '17, Pinned: 22 Apr '17
Abstract: Group IVA elements (Si, Ge, and Sn) are promising candidates for the anode materials of lithium-ion batteries (LIBs), owing to their large theoretical specific capacities. However, serious problems of pulverization and capacity degradation resulting from the huge volume changes during charge/discharge operations have hindered their successful applications as anode materials in LIBs. In this work, the diffusion behaviors of Li ions in Si(100) and Si(111) slabs with a piezoelectric field applied perpendicularly to the surfaces were investigated by using density functional theory. The results show that the diffusivity of Li in Si can be significantly enhanced by applying the electric field generated from the piezoelectric material. This finding can explain the recent experimental observations, in which an improved electrochemical performance was obtained by using Si/carbon nanotube/BaTiO3 as the anode of a LIB. A new generation of anode composite materials can be designed based on this idea and the piezoelectric material is used not only to accommodate the volume variation of active materials of Si, but also to enhance the charging rate of the LIBs.
Pub.: 07 Apr '17, Pinned: 22 Apr '17
Abstract: 0.8(Bi0.5Na0.5)TiO3−0.2(Bi0.5K0.5)(HfxTi1−x)O3 (abbreviated as BNT-BKHxT1−x) lead-free ceramics are prepared using a solid state reaction method and their dielectric, field-induced strain and energy storage properties have been systemically investigated. It was found that the largest strain induced by an external electric field occurs for x=0.02. For the x=0.02 sample, S33=0.41%, Smax/Emax=683 pm/V. However, the energy storage density is optimized at the x=0.03 sample, for which W1=0.51 J/cm3. Those results may originate from the field-induced transition between a relaxor-ferroelectric mixture phase and a ferroelectric phase.
Pub.: 13 Apr '17, Pinned: 22 Apr '17
Abstract: Piezoelectric technology has existed for many years as a surgical tool for precise removal of soft tissue and bone. The existing literature regarding its use specifically for otolaryngology, and head and neck surgery was reviewed.The databases Medline, the Cochrane Central Register of Controlled Trials, PubMed, Embase and Cambridge Scientific Abstracts were searched. Studies were selected and reviewed based on relevance.Sixty studies were identified and examined for evidence of benefits and disadvantages of piezoelectric surgery and its application in otolaryngology. The technique was compared with traditional surgical methods, in terms of intra-operative bleeding, histology, learning curve, operative time and post-operative pain.Piezoelectric technology has been successfully employed, particularly in otology and skull base surgery, where its specific advantages versus traditional drills include a lack of 'blunting' and tissue selectivity. Technical advantages include ease of use, a short learning curve and improved visibility. Its higher cost warrants consideration given that clinically significant improvements in operative time and morbidity have not yet been proven. Further studies may define the evolving role of piezoelectric surgery in otolaryngology, and head and neck surgery.
Pub.: 18 Apr '17, Pinned: 22 Apr '17
Abstract: Europium doped ZnO nanorods were successfully synthesized using low cost wet-chemical precipitation method. The crystalline phases and structural analysis were investigated by powder X-ray diffraction (XRD) study. XRD analysis confirmed the formation of wurtzite hexagonal crystal system for both pure and Europium doped ZnO. The crystallite size, lattice strain, stress and energy density were evaluated by line broadening analysis methods such as Scherrer and Williamson-Hall (W-H) methods. Transmission electron microscopy (TEM) confirmed that pure and Europium doped ZnO nanoparticles were grown in the shape of rods. The average diameter of pure ZnO nanorods was found to be ∼85.79 nm. The average diameter (∼78.92 nm) of the Eu-doped ZnO nanorods measured using TEM analysis was found to be in co-relation with W-H methods. Detailed analyses of frequency and temperature dependence of dielectric constant, dielectric loss and AC conductivity of pure and Europium doped ZnO were performed. Improved ferroelectric to paraelectric phase transition temperature at Tc = 230 °C was observed for Eu-ZnO sample. In ferroelectric measurement of Europium doped ZnO, remnant polarization and coercive field were found to be 0.11 μC/cm2 and 5.81 kV/cm, respectively. In addition, butterfly loop and effective piezoelectric coefficient (d33) versus applied voltage curve were traced for Europium doped ZnO nanorods. The mean value of d33 was evaluated to be 43.38 pm/V. I-V studies were carried out to measure the effect of Europium doping on DC conductivity of ZnO.
Pub.: 31 Jul '16, Pinned: 22 Apr '17
Abstract: Pure and lanthanum (La) doped ZnO nanorods were synthesized via co-precipitation method. The structure and morphology of as grown ZnO and La-ZnO nanoparticles were studied using transmission electron microscopy (TEM) and powder X-ray diffraction (XRD) methods. The values of remnant polarization and coercive field were found to be 0.027 μC/cm2 and 1.33 kV/cm, respectively, for as grown La-ZnO nanostructures. High Curie temperature (276 °C) for doped ZnO was observed in dielectric study. Piezoelectric coefficient at room temperature was found to be 101.30 pm/V. I-V characteristics were studied for both pure and doped ZnO nanoparticles. Photo-anodes of dye-sensitized solar cells (DSSCs) were made using ZnO and La-ZnO nanorods. The conversion efficiency and short circuit current density of La-ZnO nanorods based DSSC were 0.36% and 1.31 mA/cm2, respectively, which were found to be largely enhanced when compared with that of pure ZnO based DSSC (0.20% and 0.94 mA/cm2).
Pub.: 14 Apr '17, Pinned: 22 Apr '17
Abstract: This paper studies the electro-mechanical shear buckling analysis of piezoelectric nanoplate using modified couple stress theory with various boundary conditions.In order to be taken electric effects into account, an external electric voltage is applied on the piezoelectric nanoplate. The simplified first order shear deformation theory (S-FSDT) has been employed and the governing differential equations have been obtained using Hamilton's principle and nonlinear strains of Von-Karman. The modified couple stress theory has been applied to considering small scale effects. An analytical approach was developing to obtain exact results with various boundary conditions. After all, results have been presented by change in some parameters, such as; aspect ratio, effect of various boundary conditions, electric voltage and length scale parameter influences. At the end, results showed that the effect of external electric voltage on the critical shear load occurring on the piezoelectric nanoplate is insignificant.
Pub.: 05 Apr '17, Pinned: 22 Apr '17
Abstract: The purpose of this study is designing and examining impact-based piezoelectric road energy harvesters as power sources of a variety of sensors and smart highways. The impact-based piezoelectric road energy harvesters(15 × 15 × 9 cm3) developed in this research can convert the input energy efficiently into electrical power. The output power of the proposed harvester is significantly higher than that of the existing harvesters. Moreover, in previous studies, simple experiments were performed for measuring the output power of a road energy harvester, with no consideration for the practical road conditions. In this study, the output power is measured using machines that can simulate the practical road conditions. First, the output power of the harvester is measured using a universal testing machine (UTM) that can apply an axial load with a controlled loading frequency. Then, a third-scale mobile loading simulator (MMLS3) that can simulate practical traffic load on a lab scale is used. As a result, the maximum output power of the road energy harvester is 483 mW(21.47 W/m2).
Pub.: 18 Apr '17, Pinned: 22 Apr '17
Abstract: Besides the intrinsic semiconducting direct band gap in monolayer MoS2 (ML-MoS2), piezoelectricity arises in it due to the broken inversion symmetry. This underscores the need to unveil the simultaneous response of piezoelectric and semiconducting properties to different modes of strain. The present study explores a synergic coupling between these two properties in adaptive nanopiezotronic devices, using density functional theory. Out of the different strain types studied, shear strain and uniaxial tensile strain applied along the zigzag direction are found to be most effectual in fortifying the piezoelectric properties in ML-MoS2. Shear strain is found to raise both the piezoelectric stress (e11) and strain (d11) coefficients by 3 orders of magnitude, while uniaxial tensile strain increases the same by 2 orders of magnitude for an applied mechanical strain of 5%. The effect is found to be even stronger upon reaching the elastic limit, which is found to lie within 5–10% strain for different strain modes studied. At around 4–5% of shear strain and about 6–7% of uniaxial tensile strain, nanopiezotronic properties are found to be optimally exploitable in ML-MoS2, when the piezoelectric coefficients are maximized while the semiconducting properties are retained. Additionally, carrier mobilities have been computed. The drastic drop in electron and hole mobilities at 3% uniaxial compressive strain and 1% uniaxial tensile strain respectively may be utilized in designing low-power switches. Compressive strain applied along the zigzag direction is found to boost both electron and hole mobilities. Our accurate predictive studies provide useful pointers for developing efficient nanopiezotronic devices, actuators, and nanoelectromechanical systems.
Pub.: 07 Apr '17, Pinned: 22 Apr '17