Extracting energy from low vibration frequencies (<10 Hz) using piezoelectric energy harvester promises continuous self-powering for sensors and wearables The piezoelectric compliant mechanism (PCM) design provides a significantly higher efficiency by fostering a uniform strain for its 1st mode shape, and so is interesting for this application In this paper, a PCM energy harvester with bimorph Pb(Zr,Ti)O3 (PZT) films on Ni foil deposited by rf magnetron sputtering is shown to have high efficiency and large power for low frequency mechanical vibration In particular, {001} textured PZT films are deposited on both sides of polished Ni foils with (100) oriented LaNiO3 seed layers on HfO2 buffer layers The performance of PCM with an active area of 52 cm2 is explored for various excitation accelerations (002–016 g [g = 98 m s−2]) around 6 Hz The PCM device provides a power level of 39 mW cm−2 g2 and 65% mode shape efficiencies

Efficient Piezoelectric Energy Harvesters Utilizing (001) Textured Bimorph PZT Films on Flexible Metal Foils

A silicon micromirror driven by piezoelectric Pb(Zr,Ti)O3 beam actuators has been demonstrated for two-dimensional (2D) scanning mirror applications. Two devices of similar design with different dimensions have been fabricated. The Si mirror is micromachined from the device layer of an SOI wafer, while the piezoelectric beam actuator contains multilayers of Pt/Ti/PZT/Pt/Ti/SiO2/Si which is deposited and released from a SOI wafer. A 1 × 10 PZT arrayed actuator are separately arranged in parallel on a Si beam released from the SOI substrate after the micromachining process. The 10 PZT actuators are electrically connected in series. For the large micromirror device with mirror size of 5 mm × 5 mm, the first resonant frequency for bending mode was measured at 34 Hz, while the second mode, i.e., a twist mode or torsional mode, is measured at a resonant frequency of 198 Hz. For the small micromirror device with mirror size of 3 mm × 3 mm, the bending and torsional modes were observed at 122 Hz and 2.46 kHz respectively. 2D raster scanning patterns were illustrated for both micromirrors. dc superimposed bias effect was also investigated for both mirror sizes. With increased dc bias, larger deflection angles were obtained.

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Characterization of piezoelectric PZT beam actuators for driving 2D scanning micromirrors

We propose a MEMS piezoelectric energy harvester with a wide operating frequency range by incorporating a high-frequency piezoelectric cantilever and a metal base as the top and bottom stoppers with a low-frequency piezoelectric cantilever. Frequency up-conversion of the piezoelectric energy harvester is realized when the low-frequency piezoelectric cantilever impacts and scrapes through the high-frequency piezoelectric cantilever. For an input acceleration of 0.6 g, with top and bottom stopper distances of 0.75 and 1.1 mm, respectively, the operating frequency ranges from 33 to 43 Hz. The output voltage and power up to 95 mV and 94 nW can be achieved. Experimental results indicate that the frequency up-conversion mechanism significantly improves the effective power.

https://www.ece.nus.edu.sg/stfpage/elelc/Publication/2011/86.%20MST_11V17_12_A%20scrape-through%20piezoelectric%20MEMS%20energy%20harvester%20with%20frequency%20broadband%20and%20up-conversion%20behaviors.pdf

A scrape-through piezoelectric MEMS energy harvester with frequency broadband and up-conversion behaviors

The reduction of silver from an aqueous solution on BiFeO3 surfaces, activated by visible light, was investigated as a function of crystal and ferroelectric domain orientation. When excited by light with energy between 2.53 and 2.70 eV, BiFeO3 photochemically reduces silver cations from solution in patterns corresponding to the underlying ferroelectric domain structure. Silver is preferentially reduced on domains with a positive polarization directed toward the surface. The amount of reduced silver depends on whether the component of the domain polarization normal to the surface is positive or negative, but is relatively insensitive to the crystal orientation. It is concluded that the ferroelectric polarization decreases electron drift to the surface in domains with a negative polarization, causing spatially selective photochemical behavior, and that the direction of the polarization is more important than the amplitude.

Effect of Crystal and Domain Orientation on the Visible-Light Photochemical Reduction of Ag on BiFeO3

For usage of noncontact atomic force microscopy (NC-AFM) in a liquid environment, we propose a “van der Pol”-type self-excited cantilever probe whose steady state amplitude can be controlled to be sufficiently small so as not to damage the surface of the observation object. The self-exciting technique for the micro cantilever probe has become a powerful tool for obtaining atomically resolved images in environments where the cantilever has a very low quality factor Q. It is important to maintain the steady state amplitude of the cantilever to prevent damage to the surface, to reduce the contact force with the sample surface, and to avoid destruction of a soft material having an irregular surface such as biomolecules. In contrast to external excitation, the response amplitude of a self-excited oscillator is generally determined by the amount of nonlinearity of the system. The greater the nonlinearity, the smaller the steady state amplitude. We apply nonlinear feedback control in addition to linear feedback control to increase inherent nonlinearity in the system. Thereby, the cantilever probe has nonlinear characteristics that are equivalent to a van der Pol oscillator. It is shown analytically via an asymptotic perturbation approach that the self-excited oscillation has small steady state amplitude. Experiments are performed using a micro cantilever that is fabricated from a Pt/Ti/PZT/Pt/Ti/SiO2/SOI multi-layered structure. The validity and advantage of the proposed control method are confirmed to realize the stable self-excited oscillation with as small an amplitude as possible for the NC-AFM for a liquid environment.

Van der Pol type self-excited micro-cantilever probe of atomic force microscopy

Effect of multi-coating process on the orientation and microstructure of lead zirconate titanate (PZT) thin films derived by chemical solution deposition

J. Tsaur

Papers

Effect of multi-coating process on the orientation and microstructure of lead zirconate titanate (PZT) thin films derived by chemical solution deposition