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.
Vibration energy harvesting is an attractive technique for potential powering of wireless sensors and low power devices. While the technique can be employed to harvest energy from vibrations and vibrating structures, a general requirement independent of the energy transfer mechanism is that the vibration energy harvesting device operate in resonance at the excitation frequency. Most energy harvesting devices developed to date are single resonance frequency based, and while recent efforts have been made to broaden the frequency range of energy harvesting devices, what is lacking is a robust tunable energy harvesting technique. In this paper, the design and testing of a resonance frequency tunable energy harvesting device using a magnetic force technique is presented. This technique enabled resonance tuning to ±20% of the untuned resonant frequency. In particular, this magnetic-based approach enables either an increase or decrease in the tuned resonant frequency. A piezoelectric cantilever beam with a natural frequency of 26 Hz is used as the energy harvesting cantilever, which is successfully tuned over a frequency range of 22-32 Hz to enable a continuous power output 240-280 μW over the entire frequency range tested. A theoretical model using variable damping is presented, whose results agree closely with the experimental results. The magnetic force applied for resonance frequency tuning and its effect on damping and load resistance have been experimentally determined.
Direct piezoelectric potential measurement of single lead ziroconate titanate (PZT) nanofiber under bending using a nanomanipulator inside a scanning electron microscope chamber was presented. The PZT nanofibers, with the diameter and length around 100 nm and 70–100 μm, respectively, were aligned across trenches on a silicon substrate with a thermally grown oxide diffusion barrier and evaporated gold electrodes. A potential of ∼0.4 mV was generated when a bending moment was applied to a PZT nanofiber with an effective length of 4 μm by a tungsten tip of the nanomanipulator. The experiment demonstrated the feasibility of using these PZT nanofibers for nanoscale sensing, actuation, and energy harvesting.
Supramolecular polymers are constructed based on the novel bis[alkynylplatinum(II)] terpyridine molecular tweezer/pyrene recognition motif. Successive addition of anthracene as the diene and cyano-functionalized dienophile triggers the reversible supramolecular polymerization process, thus advancing the concept of utilizing Diels-Alder chemistry to access stimuli-responsive materials in compartmentalized systems.
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.
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