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
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
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
Engineering, Mechanical
Hua-Yang Chen, Zhen-Hui Qin, Sheng-Nan Liang, Xin Li, Si-Yuan Yu, Yan-Feng Chen
Summary: A gradient-index seismic metamaterial based on a surface acoustic PnC is proposed to provide omnidirectional protection against ultra-broadband seismic Rayleigh waves.
EXTREME MECHANICS LETTERS
(2023)
Article
Chemistry, Physical
Liang Zhang, Ting Tan, Zhengyue Yu, Zhimiao Yan
Summary: This study proposes a method to improve the localization of elastic waves in phononic crystals by introducing topological imbalance and semi-enclosed defects. Parametric equations are used to generate lattice unit cells with topological evolution and band gap widening is achieved by increasing topological imbalance. Experimental results show that phononic crystals with semi-enclosed line defects have the best energy confinement effect.
Article
Materials Science, Multidisciplinary
Jinfeng Zhao, Xiaodong Cui, Bernard Bonello, Bahram Djafari-Rouhani, Weitao Yuan, Yongdong Pan, Jie Ren, Xiaoqing Zhang, Zheng Zhong
Summary: We demonstrate experimentally and theoretically the broadband sub-diffraction and ultra-high energy density focusing of elastic wave inside planar gradient-index (GRIN) plate lenses based on thickness variation, which can potentially be used for energy harvesting and signal sensing.
JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS
(2021)
Article
Materials Science, Multidisciplinary
Fan Yang, Zhuhua Tan, Xu Han, Chongdu Cho
Summary: A graded negative refraction index phononic crystal plate lens was designed using a method of rotating scatterers, showing significant focusing efficiency, and providing a new way for fabricating energy harvesting devices.
RESULTS IN PHYSICS
(2021)
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)
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
Nanoscience & Nanotechnology
Chae-Lin Park, Byeonghwa Goh, Shi Hyeong Kim, Joonmyung Choi
Summary: This report introduces a spherical fleece made of wool fibers and single-walled carbon nanotubes (SWCNTs), which can generate repetitive electrical currents in all directions. The fleece can change the surface area available for ions to access SWCNTs, leading to a piezoionic phenomenon. The fabricated SWCNT/wool energy harvester has the highest current per input mechanical stress among all reported underwater mechanical energy harvesters to date, and it is suitable for low-frequency environments, making it ideal for utilizing natural forces as harvesting sources.
ACS APPLIED MATERIALS & INTERFACES
(2023)
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
Physics, Applied
Fuyin Ma, Zhen Huang, Chongrui Liu, Jiu Hui Wu
Summary: This tutorial provides a comprehensive overview of the basic principles and traditional methods of acoustic focusing and imaging. It further discusses the progress in sub-wavelength focusing and super-resolution imaging achieved through artificial acoustic devices such as phononic crystals and acoustic metamaterials. The tutorial also explores the potential future trends and practical application prospects in this field.
JOURNAL OF APPLIED PHYSICS
(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
Crystallography
Xinsa Zhao, Guodong Hao, Yu Shang, Jianning Han
Summary: Conventional acoustic systems have difficulty in sensing weak acoustic fault signals in complex mechanical vibration environments. To address this issue, a three-dimensional device, coupling gradient acoustic metamaterials (GAM) with phononic crystals (GAM-PC), is proposed in this paper. The strong wave compression effect coupled with the phononic crystal equivalent medium mechanism is utilized to enhance the perception of weak acoustic signals at the target frequency. Numerical simulations and experiments verify the superior amplification capability of the GAM-PC structure for loud signal amplitudes. Additionally, the GAM-PC structure has a narrower bandwidth per slit, making it more frequency selective, and it can separate different frequency components. This work is expected to be applied in signal monitoring in environments with strong noise.
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
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
Minh Nhut Le, Kang-Jun Baeg, Kyung-Tae Kim, Seung-Han Kang, Byung Doo Choi, Chan-Yong Park, Seong-Pil Jeon, Sol Lee, Jeong-Wan Jo, Seonhyoung Kim, Jun-Gu Park, Dongil Ho, Jongin Hong, Miso Kim, Han-Ki Kim, Choongik Kim, Kwanpyo Kim, Yong-Hoon Kim, Sung Kyu Park, Myung-Gil Kim
Summary: Stress-diffusive organic-inorganic hybrid superlattice nanostructures have been developed to overcome the mechanical limitations of metal oxides in flexible electronic applications, providing high electrical conductivity and mechanical stability.
ADVANCED FUNCTIONAL MATERIALS
(2021)
Article
Thermodynamics
Jaeyub Hyun, H. Alicia Kim
Summary: The study aims to develop a level-set topology optimization method using thermal eigenvalue to optimize the overall response time of heat conduction systems. Numerical examples demonstrate the feasibility of controlling the overall heat response time through thermal eigenvalue.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2021)
Article
Multidisciplinary Sciences
Seungjin Nam, Sooun Lee, Aeran Roh, Hansol Son, Miso Kim, Hyunjoo Choi
Summary: The study demonstrated that the supersaturated Al-C phases formed in the Al/C-60 composites through heat treatment significantly enhanced their hardness and elastic modulus. By adjusting the heat treatment parameters, the content of different phases in the composites can be controlled, affecting their mechanical properties.
SCIENTIFIC REPORTS
(2021)
Article
Nanoscience & Nanotechnology
Soo-Ho Jo, Yong Chang Shin, Wonjae Choi, Heonjun Yoon, Byeng D. Youn, Miso Kim
Summary: This study investigates elastic wave localization in a phononic crystal with double defects by analyzing numerical and experimental results, revealing the mechanism of defect band splitting. Experimental results confirm that interaction between double defects leads to defect band splitting, and the degree of splitting is influenced by the inter-distance combinations of the defects.
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.
Review
Physics, Multidisciplinary
Geon Lee, Dongwoo Lee, Jeonghoon Park, Yeongtae Jang, Miso Kim, Junsuk Rho
Summary: Mechanical metamaterials and phononic crystals can localize, focus, and guide elastic or acoustic waves in various ways. These man-made structures allow for more efficient collection of energy and have a wide range of potential applications in renewable energy transformation.
COMMUNICATIONS PHYSICS
(2022)
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
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.
Proceedings Paper
Engineering, Electrical & Electronic
Miso Kim
Summary: This article summarizes a series of recent advances in using various metamaterial designs in elastic and acoustic regimes to push the boundaries and achieve a new paradigm of energy focusing and harvesting.
2021 34TH IEEE INTERNATIONAL CONFERENCE ON MICRO ELECTRO MECHANICAL SYSTEMS (MEMS 2021)
(2021)
