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Über dieses Buch

This book presents device design, layout design, FEM analysis, device fabrication, and packaging and testing of MEMS-based piezoelectric vibration energy harvesters. It serves as a complete guide from design, FEM, and fabrication to characterization. Each chapter of this volume illustrates key insight technologies through images. The book showcases different technologies for energy harvesting and the importance of energy harvesting in wireless sensor networks. The design, simulation, and comparison of three types of structures – single beam cantilever structure, cantilever array structure, and guided beam structure have also been reported in one of the chapters. In this volume, an elaborate characterization of two-beam and four-beam fabricated devices has been carried out. This characterization includes structural, material, morphological, topological, dynamic, and electrical characterization of the device. The volume is very concise, easy to understand, and contains colored images to understand the details of each process.

Inhaltsverzeichnis

Frontmatter

Chapter 1. Introduction

Abstract
This chapter introduces energy harvesting for wireless sensor networks. Mobile sensor nodes located at remote locations require power which can be provided through available renewable energy. State-of-the-art technologies used for energy harvesting in WSNs have been presented to understand the amount of power required by the sensor nodes and the energy source suitable to power them. Vibration energy harvesting and its transduction mechanisms, i.e., electromagnetic, capacitive and piezoelectric, used to scavenge vibration energy that can be realized in MEMS technology are discussed.
Shanky Saxena, Ritu Sharma, B. D. Pant

Chapter 2. Piezoelectric Vibration Energy Harvesters: A Review

Abstract
In this chapter, a state-of-the-art review focused on MEMS-based P-VEHs is presented. Different device designs based on single-beam structure fixed-free type, generator array type and fixed-fixed or guided beam type are presented. Key parameters like maximum power output, resonance frequency and fabrication technology used are discussed. Unimorph and bimorph piezoelectric layer-based designs operating in different modes are presented. Finally, the findings are summarized, and literature gaps based on low-frequency design and stable device operation are discussed.
Shanky Saxena, Ritu Sharma, B. D. Pant

Chapter 3. Design, Modeling and Comparison of Piezoelectric Vibration Energy Harvesters

Abstract
In this chapter, analytical design and FEM analysis for cantilever-based P-VEH have been presented. Analytical equations giving device displacement, spring constant, resonance frequency for different structures have been reported. Device performance parameters such as resonance frequency, displacement, electric potential and von Mises stress are obtained using FEM for single-beam, cantilever array and guided-beam-type P-VEH. Effect of shape of seismic mass on the potential generated by the P-VEH has been investigated. Square-shape, pyramidal-shape and triangular-shape seismic mass-based cantilever structures have been designed, and displacement, stress and electric potential are obtained using FEM. Design giving better electric potential and stable response is selected for further investigation and device fabrication.
Shanky Saxena, Ritu Sharma, B. D. Pant

Chapter 4. Design and FEM Simulation of Guided Beam Piezoelectric Energy Harvester

Abstract
In this chapter, design, FEM analysis and comparison of guided two-beam and four-beam P-VEH have been discussed. Device parameters such as resonance frequency, beam displacement, stress and electric potential have been obtained and compared for both devices. A heavy pyramidal-shape seismic mass is connected at the center for higher electric potential and lower resonance frequency. A guided four-beam device can withstand higher stress and gives reliable operation as compared to a guided two-beam device. Design optimization for the split electrodes has been done for higher output potential and low-frequency operation. The optimized design for guided two-beam and four-beam device has been selected for fabrication in MEMS technology.
Shanky Saxena, Ritu Sharma, B. D. Pant

Chapter 5. Fabrication of Guided Beam Piezoelectric Energy Harvester

Abstract
This chapter reports fabrication of guided two-beam and four-beam P-VEH in MEMS technology. A five-level mask process has been designed for device fabrication. TMAH CMOS compatible 25 wt.% wet etching has been used for the realization of pyramidal-shape seismic mass and DRIE for releasing the two-beam and four-beam structures. Corner compensation is used to obtain perfect edges at the bottom vertex for pyramidal-shaped seismic mass. A 2.5-μm-thick ZnO layer is sandwiched between the bottom and top electrodes for the generation and collection of electric potential. Beam thinning using DRIE is done from the backside of the silicon wafer to reduce the beam thickness resulting in a significant reduction in the resonance frequency of the devices. A special kind of PCB was designed having gold-plated pads suitable for wire bonding, and also, a special kind of PCB attachment was designed with a built-in connector and attached to the PCB so that the coaxial cable can be connected to the analyzer.
Shanky Saxena, Ritu Sharma, B. D. Pant

Chapter 6. Testing and Characterization of Guided Beam Piezoelectric Energy Harvester

Abstract
This chapter presents testing and characterization for guided two-beam and four-beam P-VEH. Structural characterization for the device has been done using XRD, SEM and AFM to determine the phase orientation of materials, surface morphology, topological view and surface roughness of the deposited films. A laser Doppler vibrometer has been used to determine the resonance frequency of the devices. Resonance frequency of the two-beam device comes at 466 Hz, and for the four-beam device, resonance frequency is 515 Hz. Vibration shaker test using SPEKTRA SE-10 is performed to measure the output potential generated at a given acceleration on two-beam and four-beam devices. In the low-frequency domain (10–1000 Hz), two-beam and four-beam devices exhibit net sensitivities of 2.2784 mV/m/s2 and 4.09272 mV/m/s2, respectively.   
Shanky Saxena, Ritu Sharma, B. D. Pant

Chapter 7. Design of MEMS-Based Piezoelectric Energy Harvester for Low-Frequency Applications

Abstract
This chapter presents the design and FEM analysis of a P-VEH device suitable for practical application. A cantilever-based P-VEH design has been selected because it has lower resonance frequency and high sensitivity which can harvest optimal power from the ambient vibrations. A detailed analysis has been done using FEM tool COMSOL Multiphysics®. Effect of each design parameters such as length, width and thickness of the beam on the cantilever deflection, stress and electric potential generated have been investigated. Parametric variation study has been done where each parameter is increased individually, and the effect on the device performance is investigated. This study enables to optimize the device parameters and select the dimensions which are best suitable for a specific application.
Shanky Saxena, Ritu Sharma, B. D. Pant
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