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Cho S, Gaponenko I, Cordero-Edwards K, Barceló-Mercader J, Arias I, Kim D, Lichtensteiger C, Yeom J, Musy L, Kim H, Han SM, Catalan G, Paruch P, Hong S. Switchable tribology of ferroelectrics. Nat Commun 2024; 15:387. [PMID: 38195614 PMCID: PMC10776724 DOI: 10.1038/s41467-023-44346-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2023] [Accepted: 12/09/2023] [Indexed: 01/11/2024] Open
Abstract
Switchable tribological properties of ferroelectrics offer an alternative route to visualize and control ferroelectric domains. Here, we observe the switchable friction and wear behavior of ferroelectrics using a nanoscale scanning probe-down domains have lower friction coefficients and show slower wear rates than up domains and can be used as smart masks. This asymmetry is enabled by flexoelectrically coupled polarization in the up and down domains under a sufficiently high contact force. Moreover, we determine that this polarization-sensitive tribological asymmetry is widely applicable across various ferroelectrics with different chemical compositions and crystalline symmetry. Finally, using this switchable tribology and multi-pass patterning with a domain-based dynamic smart mask, we demonstrate three-dimensional nanostructuring exploiting the asymmetric wear rates of up and down domains, which can, furthermore, be scaled up to technologically relevant (mm-cm) size. These findings demonstrate that ferroelectrics are electrically tunable tribological materials at the nanoscale for versatile applications.
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Affiliation(s)
- Seongwoo Cho
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea.
- Department of Quantum Matter Physics, University of Geneva, 1211, Geneva, Switzerland.
| | - Iaroslav Gaponenko
- Department of Quantum Matter Physics, University of Geneva, 1211, Geneva, Switzerland
- G.W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia, 30332, United States of America
| | | | - Jordi Barceló-Mercader
- LaCàN - Mathematical and Computational Modeling, Polytechnic University of Catalonia, Barcelona, 08034, Spain
| | - Irene Arias
- LaCàN - Mathematical and Computational Modeling, Polytechnic University of Catalonia, Barcelona, 08034, Spain
- International Centre for Numerical Methods in Engineering (CIMNE), Barcelona, 08034, Spain
| | - Daeho Kim
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea
| | - Céline Lichtensteiger
- Department of Quantum Matter Physics, University of Geneva, 1211, Geneva, Switzerland
| | - Jiwon Yeom
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea
| | - Loïc Musy
- Department of Quantum Matter Physics, University of Geneva, 1211, Geneva, Switzerland
| | - Hyunji Kim
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea
| | - Seung Min Han
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea
| | - Gustau Catalan
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), Campus Autonomous University of Barcelona, Bellaterra, 08193, Spain
- Catalan Institution for Research and Advanced Studies (ICREA), Barcelona, 08010, Catalonia
| | - Patrycja Paruch
- Department of Quantum Matter Physics, University of Geneva, 1211, Geneva, Switzerland.
| | - Seungbum Hong
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea.
- KAIST Institute for NanoCentury (KINC), Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea.
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2
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Ji J, Yu G, Xu C, Xiang HJ. Fractional quantum ferroelectricity. Nat Commun 2024; 15:135. [PMID: 38167841 PMCID: PMC10761868 DOI: 10.1038/s41467-023-44453-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Accepted: 12/14/2023] [Indexed: 01/05/2024] Open
Abstract
For an ordinary ferroelectric, the magnitude of the spontaneous electric polarization is at least one order of magnitude smaller than that resulting from the ionic displacement of the lattice vectors, and the direction of the spontaneous electric polarization is determined by the point group of the ferroelectric. Here, we introduce a new class of ferroelectricity termed Fractional Quantum Ferroelectricity. Unlike ordinary ferroelectrics, the polarization of Fractional Quantum Ferroelectricity arises from substantial atomic displacements that are comparable to lattice constants. Applying group theory analysis, we identify 28 potential point groups that can realize Fractional Quantum Ferroelectricity, including both polar and non-polar groups. The direction of polarization in Fractional Quantum Ferroelectricity is found to always contradict with the symmetry of the "polar" phase, which violates Neumann's principle, challenging conventional symmetry-based knowledge. Through the Fractional Quantum Ferroelectricity theory and density functional calculations, we not only explain the puzzling experimentally observed in-plane polarization of monolayer α-In2Se3, but also predict polarization in a cubic compound of AgBr. Our findings unveil a new realm of ferroelectric behavior, expanding the understanding and application of these materials beyond the limits of traditional ferroelectrics.
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Affiliation(s)
- Junyi Ji
- Key Laboratory of Computational Physical Sciences (Ministry of Education), Institute of Computational Physical Sciences, State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, Shanghai, 200433, China
- Shanghai Qi Zhi Institute, Shanghai, 200030, China
| | - Guoliang Yu
- Key Laboratory of Computational Physical Sciences (Ministry of Education), Institute of Computational Physical Sciences, State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, Shanghai, 200433, China
- Shanghai Qi Zhi Institute, Shanghai, 200030, China
| | - Changsong Xu
- Key Laboratory of Computational Physical Sciences (Ministry of Education), Institute of Computational Physical Sciences, State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, Shanghai, 200433, China.
- Shanghai Qi Zhi Institute, Shanghai, 200030, China.
| | - H J Xiang
- Key Laboratory of Computational Physical Sciences (Ministry of Education), Institute of Computational Physical Sciences, State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, Shanghai, 200433, China.
- Shanghai Qi Zhi Institute, Shanghai, 200030, China.
- Collaborative Innovation Center of Advanced Microstructures, Nanjing, 210093, China.
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3
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Roh CJ, Ko EK, Chang Y, Park SH, Mun J, Kim M, Noh TW. Nanoscale Enhancement of the Local Optical Conductivity near Cracks in Metallic SrRuO 3 Film. ACS NANO 2023; 17:8233-8241. [PMID: 37094108 PMCID: PMC10173690 DOI: 10.1021/acsnano.2c12333] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Cracking has been recognized as a major obstacle degrading material properties, including structural stability, electrical conductivity, and thermal conductivity. Recently, there have been several reports on the nanosized cracks (nanocracks), particularly in the insulating oxides. In this work, we comprehensively investigate how nanocracks affect the physical properties of metallic SrRuO3 (SRO) thin films. We grow SRO/SrTiO3 (STO) bilayers on KTaO3 (KTO) (001) substrates, which provide +1.7% tensile strain if the SRO layer is grown epitaxially. However, the SRO/STO bilayers suffer from the generation and propagation of nanocracks, and then, the strain becomes inhomogeneously relaxed. As the thickness increases, the nanocracks in the SRO layer become percolated, and its dc conductivity approaches zero. Notably, we observe an enhancement of the local optical conductivity near the nanocrack region using scanning-type near-field optical microscopy. This enhancement is attributed to the strain relaxation near the nanocracks. Our work indicates that nanocracks can be utilized as promising platforms for investigating local emergent phenomena related to strain effects.
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Affiliation(s)
- Chang Jae Roh
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul 08826, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea
| | - Eun Kyo Ko
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul 08826, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea
| | - Yunyeong Chang
- Department of Materials Science and Engineering and Research Institute of Advanced Materials, Seoul National University, Seoul 08826, Republic of Korea
| | - Soon Hee Park
- Pohang Accelerator Laboratory, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea
| | - Junsik Mun
- Department of Materials Science and Engineering and Research Institute of Advanced Materials, Seoul National University, Seoul 08826, Republic of Korea
| | - Miyoung Kim
- Department of Materials Science and Engineering and Research Institute of Advanced Materials, Seoul National University, Seoul 08826, Republic of Korea
| | - Tae Won Noh
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul 08826, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea
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4
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Yeo Y, Hwang SY, Yeo J, Kim J, Jang J, Park HS, Kim YJ, Le DD, Song K, Kim M, Ryu S, Choi SY, Yang CH. Configurable Crack Wall Conduction in a Complex Oxide. NANO LETTERS 2023; 23:398-406. [PMID: 36595450 DOI: 10.1021/acs.nanolett.2c02640] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Mobile defects in solid-state materials play a significant role in memristive switching and energy-efficient neuromorphic computation. Techniques for confining and manipulating point defects may have great promise for low-dimensional memories. Here, we report the spontaneous gathering of oxygen vacancies at strain-relaxed crack walls in SrTiO3 thin films grown on DyScO3 substrates as a result of flexoelectricity. We found that electronic conductance at the crack walls was enhanced compared to the crack-free region, by a factor of 104. A switchable asymmetric diode-like feature was also observed, and the mechanism is discussed, based on the electrical migration of oxygen vacancy donors in the background of Sr-deficient acceptors forming n+-n or n-n+ junctions. By tracing the temporal relaxations of surface potential and lattice expansion of a formed region, we determine the diffusivity of mobile defects in crack walls to be 1.4 × 10-16 cm2/s, which is consistent with oxygen vacancy kinetics.
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Affiliation(s)
- Youngki Yeo
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon34141, Republic of Korea
- Center for Lattice Defectronics, Korea Advanced Institute of Science and Technology, Daejeon34141, Republic of Korea
| | - Soo-Yoon Hwang
- Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang37673, Republic of Korea
| | - Jinwook Yeo
- Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Daejeon34141, Republic of Korea
| | - Jihun Kim
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon34141, Republic of Korea
- Center for Lattice Defectronics, Korea Advanced Institute of Science and Technology, Daejeon34141, Republic of Korea
| | - Jinhyuk Jang
- Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang37673, Republic of Korea
| | - Heung-Sik Park
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon34141, Republic of Korea
- Center for Lattice Defectronics, Korea Advanced Institute of Science and Technology, Daejeon34141, Republic of Korea
| | - Yong-Jin Kim
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon34141, Republic of Korea
- Center for Lattice Defectronics, Korea Advanced Institute of Science and Technology, Daejeon34141, Republic of Korea
| | - Duc Duy Le
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon34141, Republic of Korea
- Center for Lattice Defectronics, Korea Advanced Institute of Science and Technology, Daejeon34141, Republic of Korea
| | - Kyung Song
- Department of Materials Analysis and Evaluation, Korea Institute of Materials Science, Changwon51508, Republic of Korea
| | - Moonhong Kim
- Division of Mechanical Engineering, Korea Maritime & Ocean University, 727 Taejong-ro, Yeongdo-gu, Busan49112, South Korea
| | - Seunghwa Ryu
- Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Daejeon34141, Republic of Korea
| | - Si-Young Choi
- Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang37673, Republic of Korea
| | - Chan-Ho Yang
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon34141, Republic of Korea
- Center for Lattice Defectronics, Korea Advanced Institute of Science and Technology, Daejeon34141, Republic of Korea
- KAIST Institute for the NanoCentury, Korea Advanced Institute of Science and Technology, Yuseong-gu, Daejeon34141, Republic of Korea
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5
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Xu M, Tian X, Deng Q, Li Q, Shen S. Directly Observing the Evolution of Flexoelectricity at the Tip of Nanocracks. NANO LETTERS 2023; 23:66-72. [PMID: 36576300 DOI: 10.1021/acs.nanolett.2c03614] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
As an electromechanical coupling between strain gradients and polarization, flexoelectricity is largely enhanced at the nanoscale. However, directly observing the evolution of flexoelectric fields at the nanoscale usually suffers from the difficulty of producing strain gradients and probing electrical responses simultaneously. Here, we introduce nanocracks in SrTiO3, Ba0.67Sr0.33TiO3, and TiO2 samples and apply continuously varying mechanical loading to them, and as a result, huge strain gradients appear at the crack tip and result in a significant flexoelectric effect. Then, using atomic force microscopy, we successfully measure the evolution of flexoelectricity around the crack tips. For the case of SrTiO3, the maximum induced electric field reaches 11 kV/m due to the tensile load increasing. The proposed method provides a reliable way to identify the significance of the flexoelectric effect. It may also open a new avenue for the study of flexoelectricity involving multiple physics phenomena including flexoelectronics, the flexo-photovoltaic effect, and others.
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Affiliation(s)
- Mengkang Xu
- State Key Laboratory for Strength and Vibration of Mechanical Structures, School of Aerospace, Xi'an Jiaotong University, Xi'an, 710049, Shaanxi China
| | - Xinpeng Tian
- Hubei Key Laboratory of Engineering Structural Analysis and Safety Assessment, School of Aerospace Engineering, Huazhong University of Science and Technology, Wuhan, 430074, Hubei China
- Department of Engineering Mechanics, School of Aerospace Engineering, Huazhong University of Science and Technology, Wuhan, 430074, Hubei China
| | - Qian Deng
- Hubei Key Laboratory of Engineering Structural Analysis and Safety Assessment, School of Aerospace Engineering, Huazhong University of Science and Technology, Wuhan, 430074, Hubei China
- Department of Engineering Mechanics, School of Aerospace Engineering, Huazhong University of Science and Technology, Wuhan, 430074, Hubei China
| | - Qun Li
- State Key Laboratory for Strength and Vibration of Mechanical Structures, School of Aerospace, Xi'an Jiaotong University, Xi'an, 710049, Shaanxi China
| | - Shengping Shen
- State Key Laboratory for Strength and Vibration of Mechanical Structures, School of Aerospace, Xi'an Jiaotong University, Xi'an, 710049, Shaanxi China
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6
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Ruiz VM, Olmos D, González-Benito J. PVDF/MWCNT nanocomposites with complex configurations prepared by solution blow spinning and their flexoelectric responses. POLYMER 2023. [DOI: 10.1016/j.polymer.2022.125669] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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7
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Cai S, Lun Y, Ji D, Lv P, Han L, Guo C, Zang Y, Gao S, Wei Y, Gu M, Zhang C, Gu Z, Wang X, Addiego C, Fang D, Nie Y, Hong J, Wang P, Pan X. Enhanced polarization and abnormal flexural deformation in bent freestanding perovskite oxides. Nat Commun 2022; 13:5116. [PMID: 36045121 PMCID: PMC9433432 DOI: 10.1038/s41467-022-32519-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Accepted: 08/03/2022] [Indexed: 11/09/2022] Open
Abstract
Recent realizations of ultrathin freestanding perovskite oxides offer a unique platform to probe novel properties in two-dimensional oxides. Here, we observe a giant flexoelectric response in freestanding BiFeO3 and SrTiO3 in their bent state arising from strain gradients up to 3.5 × 107 m-1, suggesting a promising approach for realizing ultra-large polarizations. Additionally, a substantial change in membrane thickness is discovered in bent freestanding BiFeO3, which implies an unusual bending-expansion/shrinkage effect in the ferroelectric membrane that has never been seen before in crystalline materials. Our theoretical model reveals that this unprecedented flexural deformation within the membrane is attributable to a flexoelectricity-piezoelectricity interplay. The finding unveils intriguing nanoscale electromechanical properties and provides guidance for their practical applications in flexible nanoelectromechanical systems.
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Affiliation(s)
- Songhua Cai
- Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, Kowloon, 999077, Hong Kong.
| | - Yingzhuo Lun
- School of Aerospace Engineering, Beijing Institute of Technology, Beijing, 100081, China
| | - Dianxiang Ji
- Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, Kowloon, 999077, Hong Kong
| | - Peng Lv
- School of Aerospace Engineering, Beijing Institute of Technology, Beijing, 100081, China
| | - Lu Han
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Changqing Guo
- School of Aerospace Engineering, Beijing Institute of Technology, Beijing, 100081, China
| | - Yipeng Zang
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Si Gao
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Yifan Wei
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Min Gu
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Chunchen Zhang
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Zhengbin Gu
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Xueyun Wang
- School of Aerospace Engineering, Beijing Institute of Technology, Beijing, 100081, China
| | - Christopher Addiego
- Department of Physics and Astronomy, University of California, Irvine, CA, 92697, USA
| | - Daining Fang
- Institute of Advanced Structure Technology, Beijing Institute of Technology, Beijing, 100081, China.,State Key Laboratory for Turbulence and Complex Systems & Center for Applied Physics and Technology, College of Engineering, Peking University, Beijing, 100871, China
| | - Yuefeng Nie
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China.
| | - Jiawang Hong
- School of Aerospace Engineering, Beijing Institute of Technology, Beijing, 100081, China.
| | - Peng Wang
- Department of Physics, University of Warwick, Coventry, CV4 7AL, UK.
| | - Xiaoqing Pan
- Department of Physics and Astronomy, University of California, Irvine, CA, 92697, USA. .,Department of Materials Science and Engineering, University of California, Irvine, CA, 92697, USA. .,Irvine Materials Research Institute, University of California, Irvine, CA, 92697, USA.
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8
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Investigation of The Cellular Response to Bone Fractures: Evidence for Flexoelectricity. Sci Rep 2020; 10:254. [PMID: 31937885 PMCID: PMC6959267 DOI: 10.1038/s41598-019-57121-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Accepted: 12/20/2019] [Indexed: 01/08/2023] Open
Abstract
The recent discovery of bone flexoelectricity (strain-gradient-induced electrical polarization) suggests that flexoelectricity could have physiological effects in bones, and specifically near bone fractures, where flexoelectricity is theoretically highest. Here, we report a cytological study of the interaction between crack stress and bone cells. We have cultured MC3T3-E1 mouse osteoblastic cells in biomimetic microcracked hydroxyapatite substrates, differentiated into osteocytes and applied a strain gradient to the samples. The results show a strong apoptotic cellular response, whereby mechanical stimulation causes those cells near the crack to die, as indicated by live-dead and caspase staining. In addition, analysis two weeks post-stimulation shows increased cell attachment and mineralization around microcracks and a higher expression of osteocalcin –an osteogenic protein known to be promoted by physical exercise. The results are consistent with flexoelectricity playing at least two different roles in bone remodelling: apoptotic trigger of the repair protocol, and electro-stimulant of the bone-building activity of osteoblasts.
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9
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Wang H, Jiang X, Wang Y, Stark RW, van Aken PA, Mannhart J, Boschker H. Direct Observation of Huge Flexoelectric Polarization around Crack Tips. NANO LETTERS 2020; 20:88-94. [PMID: 31851827 DOI: 10.1021/acs.nanolett.9b03176] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Flexoelectricity is especially relevant for nanoscale structures, and it is expected to be largest at the tip of cracks. We demonstrate the presence of a huge flexoelectric polarization at crack tips in SrTiO3 by direct observation with scanning transmission electron microscopy. We observe an averaged polarization of 62 ± 16 μC cm-2 in the three unit cells adjacent to the crack tip, which is one of the largest flexoelectric polarizations ever reported. The polarization is screened by an electron density of 0.7 ± 0.1 e-/uc localized within one unit cell. These findings reveal the relevance of flexoelectricity for the science of crack formation and propagation.
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Affiliation(s)
- Hongguang Wang
- Max Planck Institute for Solid State Research , 70569 Stuttgart , Germany
| | - Xijie Jiang
- Department of Materials and Geoscience , Technische Universität Darmstadt , 64287 Darmstadt , Germany
| | - Yi Wang
- Max Planck Institute for Solid State Research , 70569 Stuttgart , Germany
| | - Robert W Stark
- Department of Materials and Geoscience , Technische Universität Darmstadt , 64287 Darmstadt , Germany
| | - Peter A van Aken
- Max Planck Institute for Solid State Research , 70569 Stuttgart , Germany
| | - Jochen Mannhart
- Max Planck Institute for Solid State Research , 70569 Stuttgart , Germany
| | - Hans Boschker
- Max Planck Institute for Solid State Research , 70569 Stuttgart , Germany
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