Shiyou Xu

1.6 V Nanogenerator for Mechanical Energy Harvesting Using PZT Nanofibers

Energy harvesting technologies that are engineered to miniature sizes, while still increasing the power delivered to wireless electronics, (1, 2) portable devices, stretchable electronics, (3) and implantable biosensors, (4, 5) are strongly desired. Piezoelectric nanowire- and nanofiber-based generators have potential uses for powering such devices through a conversion of mechanical energy into electrical energy. (6) However, the piezoelectric voltage constant of the semiconductor piezoelectric nanowires in the recently reported piezoelectric nanogenerators (7-12) is lower than that of lead zirconate titanate (PZT) nanomaterials. Here we report a piezoelectric nanogenerator based on PZT nanofibers. The PZT nanofibers, with a diameter and length of approximately 60 nm and 500 microm, were aligned on interdigitated electrodes of platinum fine wires and packaged using a soft polymer on a silicon substrate. The measured output voltage and power under periodic stress application to the soft polymer was 1.63 V and 0.03 microW, respectively.

Flexible piezoelectric PMN-PT nanowire-based nanocomposite and device.

Piezoelectric nanocomposites represent a unique class of materials that synergize the advantageous features of polymers and piezoelectric nanostructures and have attracted extensive attention for the applications of energy harvesting and self-powered sensing recently. Currently, most of the piezoelectric nanocomposites were synthesized using piezoelectric nanostructures with relatively low piezoelectric constants, resulting in lower output currents and lower output voltages. Here, we report a synthesis of piezoelectric (1 - x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) nanowire-based nanocomposite with significantly improved performances for energy harvesting and self-powered sensing. With the high piezoelectric constant (d33) and the unique hierarchical structure of the PMN-PT nanowires, the PMN-PT nanowire-based nanocomposite demonstrated an output voltage up to 7.8 V and an output current up to 2.29 μA (current density of 4.58 μA/cm(2)); this output voltage is more than double that of other reported piezoelectric nanocomposites, and the output current is at least 6 times greater. The PMN-PT nanowire-based nanocomposite also showed a linear relationship of output voltage versus strain with a high sensitivity. The enhanced performance and the flexibility of the PMN-PT nanowire-based nanocomposite make it a promising building block for energy harvesting and self-powered sensing applications.

Fabrication and mechanical property of nano piezoelectric fibres

Aligned piezoelectric (PZT) nanofibres were fabricated by electrospinning using PZT sol?gel as precursor. A pure perovskite phase with an average grain size of 10?nm was obtained at 650??C. The average diameter of these fibres could be controlled to range from 52 to 150?nm by varying the concentration of poly(vinyl pyrrolidone) (PVP) in the precursor. Special samples of PZT nanofibres were deposited across the microfabricated trenches on a silicon wafer. Atomic force microscopy (AFM) was used to measure the mechanical properties of a single nanofibre. The elastic modulus of an individual PZT nanofibre that was obtained was 42.99?GPa, which was smaller than that of a thin-film PZT. The possible reasons for the reduction in elastic modulus of the nanofibres were discussed.

PMN-PT Nanowires with a Very High Piezoelectric Constant

A profound way to increase the output voltage (or power) of the piezoelectric nanogenerators is to utilize a material with higher piezoelectric constants. Here we report the synthesis of novel piezoelectric 0.72Pb(Mg(1/3)Nb(2/3))O(3)-0.28PbTiO(3) (PMN-PT) nanowires using a hydrothermal process. The unpoled single-crystal PMN-PT nanowires show a piezoelectric constant (d(33)) up to 381 pm/V, with an average value of 373 ± 5 pm/V. This is about 15 times higher than the maximum reported value of 1-D ZnO nanostructures and 3 times higher than the largest reported value of 1-D PZT nanostructures. These PMN-PT nanostructures are of good potential being used as the fundamental building block for higher power nanogenerators, high sensitivity nanosensors, and large strain nanoactuators.

Biotemplated Synthesis of PZT Nanowires

Piezoelectric nanowires are an important class of smart materials for next-generation applications including energy harvesting, robotic actuation, and bioMEMS. Lead zirconate titanate (PZT), in particular, has attracted significant attention, owing to its superior electromechanical conversion performance. Yet, the ability to synthesize crystalline PZT nanowires with well-controlled properties remains a challenge. Applications of common nanosynthesis methods to PZT are hampered by issues such as slow kinetics, lack of suitable catalysts, and harsh reaction conditions. Here we report a versatile biomimetic method, in which biotemplates are used to define PZT nanostructures, allowing for rational control over composition and crystallinity. Specifically, stoichiometric PZT nanowires were synthesized using both polysaccharide (alginate) and bacteriophage templates. The wires possessed measured piezoelectric constants of up to 132 pm/V after poling, among the highest reported for PZT nanomaterials. Further, integrated devices can generate up to 0.820 μW/cm(2) of power. These results suggest that biotemplated piezoelectric nanowires are attractive candidates for stimuli-responsive nanosensors, adaptive nanoactuators, and nanoscale energy harvesters.

Power generation from piezoelectric lead zirconate titanate nanotubes

PZT nanotubes were fabricated by the template-assisted method and power generation from these nanotubes was demonstrated experimentally. The PZT nanotubes obtained had high aspect ratios, and were dense, straight and continuous. A pure perovskite phase with strong [1 1 0] preferred crystallographic orientation was obtained at 650 °C. The diameters of these nanotubes ranged from 190 to 210 nm, while the length was around 58 µm, corresponding to the diameters and height of the nanopores in the anodic aluminium oxide template. The dielectric constant of the PZT nanotubes was determined to be about 470. These nanotubes could generate up to 469 mV voltage when a stainless-steel nugget was dropped on the electrode of the nanotubes. The power generation could be explained by the basic piezoelectric principles. This power generating mechanism had the potential to convert mechanical and vibration energy to electric power for nanodevices or integrated nanosytems.

Energy scavenging based on a single-crystal PMN-PT nanobelt.

Self-powered nanodevices scavenging mechanical energy require piezoelectric nanostructures with high piezoelectric coefficients. Here we report the fabrication of a single-crystal (1 − x)Pb(Mg1/3Nb2/3)O3 − xPbTiO3 (PMN-PT) nanobelt with a superior piezoelectric constant (d33 = ~550 pm/V), which is approximately ~150%, 430%, and 2100% of the largest reported values for previous PMN-PT, PZT and ZnO nanostructures, respectively. The high d33 of the single-crystalline PMN-PT nanobelt results from the precise orientation control during its fabrication. As a demonstration of its application in energy scavenging, a piezoelectric nanogenerator (PNG) is built on the single PMN-PT nanobelt, generating a maximum output voltage of ~1.2 V. This value is ~4 times higher than that of a single-CdTe PNG, ~13 times higher than that of a single-ZnSnO3 PNG, and ~26 times higher than that of a single-ZnO PNG. The profoundly increased output voltage of a lateral PNG built on a single PMN-PT nanobelt demonstrates the potential application of PMN-PT nanostructures in energy harvesting, thus enriching the material choices for PNGs.

In situ mechanical and electrical characterization of individual TiO2 nanofibers using a nanomanipulator system.

Youngs modulus and electrical resistivity of individual titanium dioxide (TiO(2)) nanofibers were characterized using a nanomanipulator system installed in a focused ion beam-scanning electron microscope (FIB-SEM) dual-beam Scanning Electron Microscope system. Youngs modulus of individual nanofibers was deduced from the analysis of their in situ resonance behavior in response to an oscillating electric field. The electrical behavior of a single nanofiber was also analyzed by a two-point method probed by a nanomanipulator. These results will contribute to the design of devices based on single TiO(2) nanofibers, as well as devices based on nanofiber networks. The methods presented here can also be applied to characterize other one-dimensional nanostructures.

Wireless biomechanical power harvesting via flexible magnetostrictive ribbons

Magnetostrictive Terfenol-D ribbons exhibiting superior magnetization values were printed onto a silicone elastomer. Deformation of the magnetostrictive ribbons alters domain orientation, which changes the magnetic flux. Interfacing the flexible magnetostrictive ribbons with a biomechanical source led to continuous sample deformations, which resulted in ‘radiating’ electromagnetic power to a remote receiver, thereby realizing wireless biomechanical power harvesting.

High sensitivity, low operational temperature ITO nano gas sensor with integrated circuits

This paper presents the gas sensing characteristics of Indium-Tin-Oxide (ITO) nanofibers. ITO nanofibers were fabricated by electrospinning process and integrated with microheater, micro temperature sensor and interdigitaded electrodes (IED). The morphology and crystal structure of ITO nanofibers were studied by SEM and XRD, respectively. The optimal working temperature and sensitivity of the ITO nanofiber gas sensors were investigated. The ITO nanofiber gas sensor exhibits a linear current-voltage relationship. The highest sensitivity of the sensor is about 34, which is obtained at a working temperature of 300°C; and this sensor can also work at room temperature, the sensitivity at room temperature is about 5.2. The detect limitation of this ITO nanofiber sensor is 10ppm. This sensor shows no response for H2. These results show that ITO nanofiber gas sensor exhibits significantly better sensitivity for NO2 at lower temperature and good selectivity for NO2 and H2.