Review
Instruments & Instrumentation
Guobiao Hu, Lihua Tang, Junrui Liang, Chunbo Lan, Raj Das
Summary: Metamaterials and phononic crystals with artificially designed periodic microstructures have unique properties and applications in energy harvesting. The integration design strategy and manipulation of refractive index profile can enhance energy harvesting efficiency.
SMART MATERIALS AND STRUCTURES
(2021)
Article
Chemistry, Physical
Sangryun Lee, Wonjae Choi, Jeong Won Park, Dae-Su Kim, Sahn Nahm, Wonju Jeon, Grace X. Gu, Miso Kim, Seunghwa Ryu
Summary: In this study, we propose a gradient-index (GRIN) phononic crystal (PnC) design based on machine learning optimization, which achieves maximum elastic wave focusing and harvesting. By training a deep neural network (NN), new hole shapes with improved focusing performance are derived and the NN is updated through active learning. The optimized GRIN PnC design exhibits 3.06 times higher wave energy intensity compared to the conventional design and is validated through experiments.
Article
Engineering, Mechanical
Yuping Tian, Wei Zhang, Zhuhua Tan, Chongdu Cho
Summary: Chiral materials provide a new platform for wave manipulation, with the potential to control elastic waves and achieve robust energy harvesting. By constructing chiral phononic crystals, strong edge states can be induced, and efficient energy harvesting can be achieved at piezoelectric positions on the material edges.
EXTREME MECHANICS LETTERS
(2022)
Article
Chemistry, Multidisciplinary
Pengcheng Jiao, Yang Yang, KingJames Idala Egbe, Zhiguo He, Yingtien Lin
Summary: A study on developing mechanical metamaterial-enabled piezoelectric nanogenerators for generating electrical power in low-frequency environments, such as the ocean. Optimization efforts were made to maximize power generation through changes in geometric and material considerations. These piezoelectric nanogenerators are considered a potential green solution for energy issues in various fields.
Article
Engineering, Mechanical
Hanjie Xiao, Tianrun Li, Liang Zhang, Wei-Hsin Liao, Ting Tan, Zhimiao Yan
Summary: Piezoelectric energy harvesting technology using acoustic metamaterials improves sound energy density and conversion efficiency. A fully coupled electromechanical model is crucial for accurate prediction and optimization of sound energy harvesting based on acoustic metamaterials.
MECHANICAL SYSTEMS AND SIGNAL PROCESSING
(2023)
Article
Engineering, Mechanical
Zhuangzhuang He, Gongye Zhang, Xin Chen, Yu Cong, Shuitao Gu, Jun Hong
Summary: The localization of elastic wave at defect in phononic crystals has been studied for designing piezoelectric energy harvesting devices. A modified couple stress theory and a mixed finite element method were used to develop a new interface to capture the microstructure-dependent size effect in simulation. Numerical results show that considering size effect, the frequencies of bandgap and defect bands increase with decreasing model size compared to classical theory. Moreover, size reduction affects the stiffness ratio and thus the displacement amplitude, output voltage and power of the PEH device.
INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES
(2023)
Article
Engineering, Mechanical
Zhihui Wen, Shixuan Zeng, Dongwei Wang, Yabin Jin, Bahram Djafari-Rouhani
Summary: This paper introduces a method to achieve strong robustness in elastic wave routing at subwavelength scale through chiral edge states, which exhibit stronger resistance to defects and perturbations. The energy harvesting powers of chiral mechanical systems show higher robustness against frequency disorder and position disorder compared to C6v designs.
EXTREME MECHANICS LETTERS
(2021)
Review
Chemistry, Multidisciplinary
Mourad Oudich, Nikhil J. R. K. Gerard, Yuanchen Deng, Yun Jing
Summary: In solid state physics, a bandgap refers to a range of energies where no electronic states can exist. This concept has been extended to classical waves, giving rise to photonic and phononic crystals. In elastic waves, bandgaps are found in materials with periodic alternating mechanical properties, leading to the development of elastic metamaterials and phononic crystals. The rise of topological insulators and the advancement of additive manufacturing have further expanded the functionalities of these manmade materials.
ADVANCED FUNCTIONAL MATERIALS
(2023)
Article
Multidisciplinary Sciences
Yuzhong Hu, Kaushik Parida, Hao Zhang, Xin Wang, Yongxin Li, Xinran Zhou, Samuel Alexander Morris, Weng Heng Liew, Haomin Wang, Tao Li, Feng Jiang, Mingmin Yang, Marin Alexe, Zehui Du, Chee Lip Gan, Kui Yao, Bin Xu, Pooi See Lee, Hong Jin Fan
Summary: The authors propose a bond weakening strategy for organic-inorganic hybrid piezoelectrics to improve their performance while maintaining mechanical softness. By introducing large-size halide elements, the metal-halide bonds can be weakened, resulting in improved piezoelectric constants and reduced polarization switching barrier.
NATURE COMMUNICATIONS
(2022)
Article
Engineering, Mechanical
Yong Chang Shin, Heonjun Yoon, Soo-Ho Jo, Wonjae Choi, Choon-Su Park, Miso Kim, Byeng D. Youn
Summary: This study introduces a quarter-wave stack (QWS)-based piezoelectric energy harvesting (PEH) system for elastic waves, aiming to manipulate the standing wave pattern and optimize the placement of the piezoelectric layer to generate maximum output power. Analysis results show that increasing the number of unit cells enhances PEH performance, while the standing wave pattern and electroelastic coupling vary with excitation frequency. These findings offer guidelines for designing parameters to maximize the performance of QWS-based PEH systems under elastic waves for various applications.
INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES
(2021)
Article
Nanoscience & Nanotechnology
Xian'e Yang, Jiahui Zhong, Jiawei Xiang
Summary: The enhancement of elastic wave energy harvesting using a phononic crystal is explored in this study. By attaching a piezoelectric transducer (PZT) disk on a 2D starlike hole-type phononic crystal, piezoelectric energy harvesting is achieved. The amplification of harvestable mechanical energy is realized through waveguide and energy localization effects. The optimal diameter and thickness of the PZT disk are obtained using numerical experiments, resulting in a 26.7-fold increase in electric power amplification ratio compared to a thin plate with the same dimensions.
Article
Energy & Fuels
Binsheng Li, Hui Chen, Baizhan Xia, Lingyun Yao
Summary: Recently, topological phononic crystals have been widely used for designing acoustic energy harvesting devices, which benefit from the robustness of the topological state. However, these devices often operate at excessively high frequencies. To address this issue, this study proposes a novel acoustic energy harvesting device based on the topological edge state of a multi-resonant phononic crystal. By introducing multiple resonant cavities, the device achieves improved robustness and reduced operating frequency. The theoretical model of the device is established and the robustness of the edge states is verified through finite element method (FEM) simulations. The results demonstrate that the device effectively collects acoustic energy, with maximum output voltage observed at an incident frequency of 718 Hz and a maximum voltage amplitude of 132.5 mV. Additionally, even with point defects, the device still demonstrates good acoustic energy collection capability, with a maximum voltage of 96.5 mV at 707 Hz. In conclusion, the topological edge state of a multi-resonant phononic crystal can be designed as an excellent acoustic energy harvesting device due to its lower operating frequency and improved design robustness.
Article
Chemistry, Physical
Sangtae Kim, Jaehoon Choi, Hong Min Seung, Inki Jung, Ki Hoon Ryu, Hyun-Cheol Song, Chong-Yun Kang, Miso Kim
Summary: This study combines Helmholtz resonance and omnidirectional acoustic wave focusing to generate high power output at low frequencies in ambient sound environments. A two-degree-of-freedom model is used to design a HR integrated with a piezoelectric device, which is then combined with a circularly symmetric gradient index phononic crystal structure for omnidirectional sound focusing. The coupled acoustic system GRIN-HR-PEH demonstrates flexibility in design and achieved an output power of up to 4.1 mW under ambient sound pressure of 47 dB.
Review
Materials Science, Multidisciplinary
Christabel Choi, Shubhi Bansal, Niko Munzenrieder, Sriram Subramanian
Summary: Acoustic metamaterials and phononic crystals have the potential to revolutionize human interactions and sensory communications. Understanding the fundamental theory and design principles alone is not enough; physical realization of these structures through fabrication and assembly is equally important. The paper critically examines fabrication and assembly approaches, addressing crucial parameters for efficient structural implementation. Various assembly techniques are proposed, uncovering innovative designs and supporting a fresh paradigm for innovation.
ADVANCED ENGINEERING MATERIALS
(2021)
Article
Chemistry, Multidisciplinary
Dae-Su Kim, Wonjae Choi, Sun-Woo Kim, Eun-Ji Kim, Sahn Nahm, Miso Kim
Summary: This study presents a rational electrode configuration for a piezoelectric energy harvesting (PEH) device that maximizes the energy collection performance of a gradient-index phononic crystal (GRIN PnC) platform. Experimental results demonstrate that the patterned electrode configuration effectively alleviates strain and voltage cancellation while efficiently transferring the focused elastic wave energy. By optimizing the combination of piezoelectric ceramic composition and electrode configuration, a maximum power generation of 7.06 mW is achieved, the largest ever reported in elastic wave energy harvesting.
MATERIALS HORIZONS
(2023)
Article
Physics, Applied
Hong Woo Park, Hong Min Seung, Miso Kim, Wonjae Choi, Joo Hwan Oh
Summary: This study proposes a method to achieve a broadband low-frequency band gap using only the continuum metamaterial itself, which can be easily extended to other vibrational systems. The idea is supported by analytical investigations, numerical simulations, and experimental realization, showing its effectiveness in expanding vibration systems at the low-frequency regime.
PHYSICAL REVIEW APPLIED
(2021)
Article
Chemistry, Multidisciplinary
Sooun Lee, Dabin Kim, Sangryun Lee, Yong-Il Kim, Sihyeon Kum, Sang-Woo Kim, Yunseok Kim, Seunghwa Ryu, Miso Kim
Summary: Electrospun polymeric piezoelectric fibers have potential for shape-adaptive mechanical energy harvesting and self-powered sensing. This study presents a design strategy to enhance the piezoelectric performance by tailoring the fiber morphology and fabricating poly(vinylidene fluoride-trifluoroethylene) fibers with surface porosity. The porous fiber design broadens the application prospects of shape-adaptive energy harvesting and self-powered sensing.
Article
Multidisciplinary Sciences
Myung Hwan Bae, Wonjae Choi, Jong Moon Ha, Miso Kim, Hong Min Seung
Summary: In this study, we proposed a metamaterial that can achieve wave localization at extremely low frequencies. By imposing a normal defect and introducing a spiral cavity, the resonating frequency can be tuned and wave localization can be achieved.
SCIENTIFIC REPORTS
(2022)
Article
Chemistry, Multidisciplinary
Jeonghoon Park, Geon Lee, Dongwoo Lee, Miso Kim, Junsuk Rho
Summary: In this study, a double-focusing flexural energy harvesting platform is proposed, which utilizes periodic structures to control elastic waves and enhance harvesting performance. By using a gradient-index lens and an elastic Bragg mirror, the output voltage and power of the harvesting platform are significantly increased compared to a bare plate.
Article
Nanoscience & Nanotechnology
Yong-Il Kim, Dabin Kim, Jihun Jung, Sang-Woo Kim, Miso Kim
Summary: This study demonstrates a method to enhance the piezoelectric performance of P(VDF-TrFE) fiber mat by electrospinning with a rapidly rotating collector. The aligned fiber mat produced from the modified drum collector showed significantly increased crystalline electroactive beta-phase content, leading to improved piezoelectricity.
Article
Multidisciplinary Sciences
Hong Woo Park, Hong Min Seung, Wonjae Choi, Miso Kim, Joo Hwan Oh
Summary: The study presents a novel metamaterial cavity system that allows for controlling the cavity mode frequency and performance without redesigning the entire metamaterial. By adjusting the cavity length and the length of the side beam, highly localized vibration energy can be obtained at the desired frequency. Numerical and experimental evidence support the effectiveness of the proposed metamaterial cavity system.
SCIENTIFIC REPORTS
(2022)
Article
Nanoscience & Nanotechnology
Soo-Ho Jo, Heonjun Yoon, Yong Chang Shin, Wonjae Choi, Byeng D. Youn, Miso Kim
Summary: This study proposes an L-shaped arrangement of triple defects in a phononic crystal for broadband piezoelectric energy harvesting. The design effectively confines and harvests elastic-wave energy over a wide range of frequencies, overcoming the limitations of single and double defect designs.
Article
Physics, Multidisciplinary
Jeonghoon Park, Dongwoo Lee, Yeongtae Jang, Anna Lee, Junsuk Rho
Summary: This article presents a mechanism for achieving a low-frequency complete bandgap by overlapping the flexural bandgap with the longitudinal-torsional bandgap. A chiral trabeated metabeam is constructed in the physical model to suppress all wave modes. This work provides a route to implementing a low-frequency complete bandgap in a periodic fashion, with potential applications in elastic structures.
COMMUNICATIONS PHYSICS
(2022)
Article
Chemistry, Physical
Sangtae Kim, Jaehoon Choi, Hong Min Seung, Inki Jung, Ki Hoon Ryu, Hyun-Cheol Song, Chong-Yun Kang, Miso Kim
Summary: This study combines Helmholtz resonance and omnidirectional acoustic wave focusing to generate high power output at low frequencies in ambient sound environments. A two-degree-of-freedom model is used to design a HR integrated with a piezoelectric device, which is then combined with a circularly symmetric gradient index phononic crystal structure for omnidirectional sound focusing. The coupled acoustic system GRIN-HR-PEH demonstrates flexibility in design and achieved an output power of up to 4.1 mW under ambient sound pressure of 47 dB.
Article
Physics, Applied
Yeongtae Jang, Geon Lee, Eunho Kim, Junsuk Rho
Summary: In this study, the authors investigate stress wave mitigation in composite-based woodpile phononic crystals. The study proposes a novel method of shock attenuation by adjusting the composition ratio of the materials, which results in extreme dispersive waves for efficient impact protection.
APPLIED PHYSICS LETTERS
(2022)
Article
Acoustics
Beomseok Oh, Chayeong Kim, Dongwoo Lee, Junsuk Rho, Wonkyu Moon
Summary: This paper presents an improved analytical model for designing the polymer-composite stepped-plate transducer (PCSPT), which features lightweight and flexible properties. The modified Mindlin plate theory (MMPT) is applied to improve the accuracy in the equivalent circuit model (ECM) used for predicting high-frequency vibratory responses. Our analytical model can be used to design well-tuned SPTs for various high-power ultrasonic applications.
