Energy harvesting is the most effective way to respond to the energy shortage and to produce sustainable power sources from the surrounding environment. The energy harvesting technology enables scavenging electrical energy from wasted energy sources, which always exist everywhere, such as in heat, fluids, vibrations, etc. In particular, piezoelectric energy harvesting, which uses a direct energy conversion from vibrations and mechanical deformation to the electrical energy, is a promising technique to supply power sources in unattended electronic devices, wireless sensor nodes, micro-electronic devices, etc., since it has higher energy conversion efficiency and a simple structure. Up to now, various technologies, such as advanced materials, micro- and macro-mechanics, and electric circuit design, have been investigated and emerged to improve performance and conversion efficiency of the piezoelectric energy harvesters. In this paper, we focus on recent progress of piezoelectric energy harvesting technologies based on PbZrxTi1-xO3 (PZT) materials, which have the most outstanding piezoelectric properties. The advanced piezoelectric energy harvesting technologies included materials, fabrications, unique designs, and properties are introduced to understand current technical levels and suggest the future directions of piezoelectric energy harvesting.

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Recent Progress on PZT Based Piezoelectric Energy Harvesting Technologies

Energy harvesting is one of the most promising research areas to produce sustainable power sources from the ambient environment. Which found applications to attain the extensive lifetime self-power...

Recent advances in flexible PVDF based piezoelectric polymer devices for energy harvesting applications

In this paper, piezoelectric MEMS (piezo-MEMS) sensors are designed and characterized for detecting elastic waves released by active flaws, known as acoustic emission (AE). The designed sensors operate in plate flexural mode or rigid body mode driven by the vibration of silicon diaphragm where piezoelectric layer is deposited on. The designed device contains two different frequency sensors tuned to 40 kHz and 200 kHz. The microstructural layers consist of doped silicon, aluminum nitride (AlN) and metal layer, which function as the bottom electrode, sensing layer and top electrode, respectively. The silicon layer also functions as a mass-spring system where a movable plate is connected with four partially clamped beams to the substrate. As the geometry sizes are restricted by the design rules of the manufacturing process, an additional mass is provided for the 40 kHz sensor through the substrate etching process. The sensors are numerically modeled using COMSOL Multiphysics software to obtain the frequency response and the dynamic response under excitation. Afterwards, the sensors are manufactured using Piezoelectric Multi-User MEMS Process (PiezoMUMPs) provided by MEMSCAP foundry. The performance of the designed sensors is demonstrated through electromechanical characterization experiments. A face-to-face response is obtained for each sensor, and the performance of the designed sensors is compared with the conventional piezoelectric AE sensors. The developed piezo-MEMS AE sensors have advantages of small foot-print, low cost and no need for bias voltage for operation.

Piezoelectric MEMS acoustic emission sensors

This article presents a brief review of the research progress achieved in the field of aluminium nitride (AlN) metastable cubic modifications synthesis. It covers mainly the synthetic approaches, such as carbothermal reduction nitridation (CRN), chemical vapour deposition (CVD), solvent thermal synthesis, high pressure phase transition and thin-film technology (molecular beam epitaxy, atmospheric reactive plasma nitriding, magnetron sputtering, pulsed laser deposition). A classification of synthetic approaches has been proposed, which is based on the difference between the aluminium compounds involved in synthesis. The basics of cubic aluminium nitride stabilization and possible technological conditions for the synthesis of the metastable cubic phase have been formulated.

Aluminium nitride cubic modifications synthesis methods and its features. Review

Lead-free piezoelectric nano-based generator with energy harvesting has drawn a great attention in the recent years. BaTiO3 as a lead-free material with high piezoelectric coefficient and dielectric constant has been widely examined to realize nanogenerators. In this work, high-quality BaTiO3 (BTO) nanowires were prepared by hydrothermal synthesis as the piezoelectric material and then BTO/PVDF-based nanogenerators have been fabricated. Furthermore, the CNTs were added to improve the output voltage performance of the nanogenerator. It shows high performance of a maximum output voltage density of 7.3 V/cm2 and the stable current density of 3.3 nA/cm2. This hybrid nanogenerator with enhanced performance is a potential material for the application in harvesting energy, self-powered electronics and low-frequency capacitors.

Hybrid nanogenerator of BaTiO3 nanowires and CNTs for harvesting energy

In this paper, the piezoelectric coefficient d33 of AlN thin films for MEMS applications was studied by the piezoresponse force microscopy (PFM) measurement and finite element method (FEM) simulation. Both the sample without a top electrode and another with a top electrode were measured by PFM to characterize the piezoelectric property effectively. To obtain the numerical solution, an equivalent model of the PFM measurement system was established based on theoretical analysis. The simulation results for two samples revealed the effective measurement value d33-test should be smaller than the intrinsic value d33 due to the clamping effect of the substrate and non-ideal electric field distribution. Their influences to the measurement results were studied systematically. By comparing the experimental results with the simulation results, an experimental model linking the actual piezoelectric coefficient d33 with the measurement results d33-test was given under this testing configuration. A novel and effective approach was presented to eliminate the influences of substrate clamping and non-ideal electric field distribution and extract the actual value d33 of AlN thin films.

https://www.mdpi.com/2072-666X/6/9/1236/pdf

Research on the Piezoelectric Properties of AlN Thin Films for

The invention discloses a method for preparing multi-stage steps on a substrate. The method comprises the following steps of: growing a mask layer on the substrate; spin-coating first-layer photoresist, and etching the first-layer photoresist on the mask layer to obtain a first groove; spin-coating second-layer photoresist on the mask layer in the first groove, and etching the second-layer photoresist on the mask layer to obtain a second groove; repeating the photoetching and etching steps according to the number of the needed steps to obtain a plurality of etching grooves on the mask layer in the second groove, and etching the last groove on the surface of the substrate; removing residual photoresist etched on a mask for the last time, transferring graphics on the mask layer onto the substrate by one time by adopting the multi-stage steps on the mask layer as the mask, and removing the residual mask layer by adopting a wet-process corrosion method so as to finish the preparation of the multi-stage step. The method disclosed by the invention has the advantages that the multi-stage steps are prepared on the same substrate material, so that the problem of adhesion in the heterogeneous multi-stage steps and the problem of difficult preparation of the high steps are avoided, and simultaneously the complexity of the process flow is also greatly reduced.

Method for preparing multi-stage steps on substrate

This paper reports the resonant properties of aluminum nitride (AlN) thin-film MEMS (micro-electromechanical systems) device. A T-shape structure is designed as a key sensitive component. Based on the piezoelectric effect of AIN, the whole structure can be excited to vibrate in-plane by top/bottom electrodes. In this work, a pair of paralleled top electrodes are used to excite the whole structure to vibrate in-plane (x-axis). A serpentine electrode can excite the whole structure to vibrate in-plane along the orthogonal direction (y-axis). The resonant properties were characterized by the dynamic signal analyzer. Resonant frequencies of the two modes are 25.1124 kHz and 24.5401 kHz. Quality factors of the two modes are 2130 and 2210, respectively. The effective efficiency of electromechanical transduction is 0.7848%. The resonant modes can be applied in MEMS gyroscopes or resonant accelerometers.

Resonant Properties of a T-sbape Aluminum Nitride Piezoelectric Structure for MEMS Device

The invention provides a two-degree of freedom MEMS piezoelectric beam structure, which comprises a substrate electrode, an anchor, a first piezoelectric layer, an interlayer electrode, a second piezoelectric layer, a first upper electrode, a second upper electrode and a third upper electrode, wherein the substrate electrode is rectangular; the anchor is made at one longitudinal side of the back surface of the substrate electrode; the first piezoelectric layer is made on the substrate electrode; the interlayer electrode is made on the first piezoelectric layer; the second piezoelectric layer is made on the interlayer electrode; the first upper electrode is made at one transverse side on the second piezoelectric layer and the width is smaller than half that of the second piezoelectric layer; the second upper electrode is made at the other transverse side on the second piezoelectric layer; the third upper electrode is made in the transverse middle of the second piezoelectric layer; and the first upper electrode, the second upper electrode and the third upper electrode are not contacted. The two-degree of freedom MEMS piezoelectric beam structure has the advantages of small quadrature errors and high electromechanical conversion efficiency.

Two-degree of freedom MEMS piezoelectric beam structure

The invention relates to a weak-coupling elastic beam structure applied to an MEMS device. The weak-coupling elastic beam structure comprises a coupling beam, a first support beam and a second support beam, wherein one end of the first support beam is longitudinally fixed on one side of the coupling beam; one end of the second support beam is longitudinally fixed on the other side of the coupling beam; and the first support beam and the second support beam are spaced at a predetermined distance. The weak-coupling elastic beam structure disclosed by the invention has the characteristics of small structural dimension, simple structure and high reliability.

Ning Jin

Papers

Research on the Piezoelectric Properties of AlN Thin Films for

Method for preparing multi-stage steps on substrate

Resonant Properties of a T-sbape Aluminum Nitride Piezoelectric Structure for MEMS Device

Two-degree of freedom MEMS piezoelectric beam structure

Weak-coupling elastic beam structure applied to MEMS device