Articoli di riviste: "Flexible mechanical metamaterials"

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Zheng, Xiaoyang, Koichiro Uto, Wei-Hsun Hu, Ta-Te Chen, Masanobu Naito e Ikumu Watanabe. "Reprogrammable flexible mechanical metamaterials". Applied Materials Today 29 (dicembre 2022): 101662. http://dx.doi.org/10.1016/j.apmt.2022.101662.

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Yasuda, Hiromi, Hang Shu, Weijian Jiao, Vincent Tournat e Jordan Raney. "Collisions of nonlinear waves in flexible mechanical metamaterials". Journal of the Acoustical Society of America 151, n. 4 (aprile 2022): A41. http://dx.doi.org/10.1121/10.0010592.

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Flexible mechanical metamaterials are compliant structures designed to achieve desired mechanical properties via large deformation or rotation of their components. While their static properties (such as Poisson’s ratio) have been studied extensively, much less work has been done on their dynamic properties, especially nonlinear dynamic properties induced by large movement of internal components. Here, we examine the nonlinear dynamic response arising from impact loading of mechanical materials that consist of 1D and 2D arrangements of rotating squares, which leads to formation of solitons. Permanent magnets are added to the squares, which causes the metamaterial to become multistable. Rotations of the squares can thereby lead to sudden rearrangements of squares into new phases. We experimentally and numerically characterize the collisions of solitons in these flexible mechanical metamaterials, which, depending on their amplitude and chirality, can induce a variety of responses, including phase transitions.

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Zhai, Zirui, Yong Wang e Hanqing Jiang. "Origami-inspired, on-demand deployable and collapsible mechanical metamaterials with tunable stiffness". Proceedings of the National Academy of Sciences 115, n. 9 (12 febbraio 2018): 2032–37. http://dx.doi.org/10.1073/pnas.1720171115.

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Origami has been employed to build deployable mechanical metamaterials through folding and unfolding along the crease lines. Deployable metamaterials are usually flexible, particularly along their deploying and collapsing directions, which unfortunately in many cases leads to an unstable deployed state, i.e., small perturbations may collapse the structure along the same deployment path. Here we create an origami-inspired mechanical metamaterial with on-demand deployability and selective collapsibility through energy analysis. This metamaterial has autonomous deployability from the collapsed state and can be selectively collapsed along two different paths, embodying low stiffness for one path and substantially high stiffness for another path. The created mechanical metamaterial yields load-bearing capability in the deployed direction while possessing great deployability and collapsibility. The principle in this work can be utilized to design and create versatile origami-inspired mechanical metamaterials that can find many applications.

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Jin, Eunji, In Seong Lee, Dongwook Kim, Hosoowi Lee, Woo-Dong Jang, Myung Soo Lah, Seung Kyu Min e Wonyoung Choe. "Metal-organic framework based on hinged cube tessellation as transformable mechanical metamaterial". Science Advances 5, n. 5 (maggio 2019): eaav4119. http://dx.doi.org/10.1126/sciadv.aav4119.

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Mechanical metamaterials exhibit unusual properties, such as negative Poisson’s ratio, which are difficult to achieve in conventional materials. Rational design of mechanical metamaterials at the microscale is becoming popular partly because of the advance in three-dimensional printing technologies. However, incorporating movable building blocks inside solids, thereby enabling us to manipulate mechanical movement at the molecular scale, has been a difficult task. Here, we report a metal-organic framework, self-assembled from a porphyrin linker and a new type of Zn-based secondary building unit, serving as a joint in a hinged cube tessellation. Detailed structural analysis and theoretical calculation show that this material is a mechanical metamaterial exhibiting auxetic behavior. This work demonstrates that the topology of the framework and flexible hinges inside the structure are intimately related to the mechanical properties of the material, providing a guideline for the rational design of mechanically responsive metal-organic frameworks.

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Zhang, Zhan, Christopher Brandt, Jean Jouve, Yue Wang, Tian Chen, Mark Pauly e Julian Panetta. "Computational Design of Flexible Planar Microstructures". ACM Transactions on Graphics 42, n. 6 (5 dicembre 2023): 1–16. http://dx.doi.org/10.1145/3618396.

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Mechanical metamaterials enable customizing the elastic properties of physical objects by altering their fine-scale structure. A broad gamut of effective material properties can be produced even from a single fabrication material by optimizing the geometry of a periodic microstructure tiling. Past work has extensively studied the capabilities of microstructures in the small-displacement regime, where periodic homogenization of linear elasticity yields computationally efficient optimal design algorithms. However, many applications involve flexible structures undergoing large deformations for which the accuracy of linear elasticity rapidly deteriorates due to geometric nonlinearities. Design of microstructures at finite strains involves a massive increase in computation and is much less explored; no computational tool yet exists to design metamaterials emulating target hyperelastic laws over finite regions of strain space. We make an initial step in this direction, developing algorithms to accelerate homogenization and metamaterial design for nonlinear elasticity and building a complete framework for the optimal design of planar metamaterials. Our nonlinear homogenization method works by efficiently constructing an accurate interpolant of a microstructure's deformation over a finite space of macroscopic strains likely to be endured by the metamaterial. From this interpolant, the homogenized energy density, stress, and tangent elasticity tensor describing the microstructure's effective properties can be inexpensively computed at any strain. Our design tool then fits the effective material properties to a target constitutive law over a region of strain space using a parametric shape optimization approach, producing a directly manufacturable geometry. We systematically test our framework by designing a catalog of materials fitting isotropic Hooke's laws as closely as possible. We demonstrate significantly improved accuracy over traditional linear metamaterial design techniques by fabricating and testing physical prototypes.

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Deng, B., J. R. Raney, K. Bertoldi e V. Tournat. "Nonlinear waves in flexible mechanical metamaterials". Journal of Applied Physics 130, n. 4 (28 luglio 2021): 040901. http://dx.doi.org/10.1063/5.0050271.

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Dykstra, David M. J., Shahram Janbaz e Corentin Coulais. "The extreme mechanics of viscoelastic metamaterials". APL Materials 10, n. 8 (1 agosto 2022): 080702. http://dx.doi.org/10.1063/5.0094224.

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Mechanical metamaterials made of flexible building blocks can exhibit a plethora of extreme mechanical responses, such as negative elastic constants, shape-changes, programmability, and memory. To date, dissipation has largely remained overlooked for such flexible metamaterials. As a matter of fact, extensive care has often been devoted in the constitutive materials’ choice to avoid strong dissipative effects. However, in an increasing number of scenarios, where metamaterials are loaded dynamically, dissipation cannot be ignored. In this Research Update, we show that the interplay between mechanical instabilities and viscoelasticity can be crucial and that they can be harnessed to obtain new functionalities. We first show that this interplay is key to understanding the dynamical behavior of flexible dissipative metamaterials that use buckling and snapping as functional mechanisms. We further discuss the new opportunities that spatial patterning of viscoelastic properties offer for the design of mechanical metamaterials with properties that depend on the loading rate.

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Rafsanjani, Ahmad, Katia Bertoldi e André R. Studart. "Programming soft robots with flexible mechanical metamaterials". Science Robotics 4, n. 29 (10 aprile 2019): eaav7874. http://dx.doi.org/10.1126/scirobotics.aav7874.

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Slobozhanyuk, Alexey P., Mikhail Lapine, David A. Powell, Ilya V. Shadrivov, Yuri S. Kivshar, Ross C. McPhedran e Pavel A. Belov. "Flexible Helices for Nonlinear Metamaterials". Advanced Materials 25, n. 25 (21 maggio 2013): 3409–12. http://dx.doi.org/10.1002/adma.201300840.

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Wu, Lingling, Bo Li e Ji Zhou. "Enhanced thermal expansion by micro-displacement amplifying mechanical metamaterial". MRS Advances 3, n. 8-9 (2018): 405–10. http://dx.doi.org/10.1557/adv.2018.217.

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ABSTRACTIt is important to achieve materials with large coefficient of thermal expansion in science and engineering applications. In this paper, we propose an experimentally-validated metamaterial approach to amplify the thermal expansion of materials based on the guiding principles of flexible hinges and displacement amplification mechanism. The thermal expansion property of the designed metamaterial is demonstrated by simulation and experiment with a temperature increase of 245 K for the two-dimensional sample. Both experimental and simulation results display amplified thermal expansion property of the metamaterial. The effective coefficient of thermal expansion of the metamaterials is demonstrated to be dependent on the size parameters of the structure, which means by appropriately tailoring these parameters, the thermal expansion of materials could be amplified with different amplification factor. This work provides an important method to control the thermal expansion coefficient of materials and could be applied in various industry domain.

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Zhou, Xiang, Shixi Zang e Zhong You. "Origami mechanical metamaterials based on the Miura-derivative fold patterns". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 472, n. 2191 (luglio 2016): 20160361. http://dx.doi.org/10.1098/rspa.2016.0361.

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This paper presents two new types of origami-inspired mechanical metamaterials based on the Miura-derivative fold patterns that consist of non-identical parallelogram facets. The analytical models to predict dimension changes and deformation kinematics of the proposed metamaterials are developed. Furthermore, by modelling the creases as revolute hinges with certain rotational spring constants, we derived analytical models for stretching and bulk moduli. The analytical models are validated through finite-element simulation results. Numerical examples reveal that the proposed metamaterials possess some intriguing properties, including negative Poisson’s ratios and bulk modulus. The work presented in this paper can provide a highly flexible framework for the design of versatile tunable mechanical metamaterials.

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Demiquel, A., V. Achilleos, G. Theocharis e V. Tournat. "Envelope vector solitons in nonlinear flexible mechanical metamaterials". Wave Motion 131 (dicembre 2024): 103394. http://dx.doi.org/10.1016/j.wavemoti.2024.103394.

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Xue, Chenhao, Nan Li, Shenggui Chen, Jiahua Liang e Wurikaixi Aiyiti. "The Laser Selective Sintering Controlled Forming of Flexible TPMS Structures". Materials 16, n. 24 (8 dicembre 2023): 7565. http://dx.doi.org/10.3390/ma16247565.

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Sports equipment crafted from flexible mechanical metamaterials offers advantages due to its lightweight, comfort, and energy absorption, enhancing athletes’ well-being and optimizing their competitive performance. The utilization of metamaterials in sports gear like insoles, protective equipment, and helmets has garnered increasing attention. In comparison to traditional truss and honeycomb metamaterials, the triply periodic minimal surface lattice structure stands out due to its parametric design capabilities, enabling controllable performance. Furthermore, the use of flexible materials empowers this structure to endure significant deformation while boasting a higher energy absorption capacity. Consequently, this study first introduces a parametric method based on the modeling equation of the triply periodic minimal surface structure and homogenization theory simulation. Experimental results demonstrate the efficacy of this method in designing triply periodic minimal surface lattice structures with a controllable and adjustable elastic modulus. Subsequently, the uniform flexible triply periodic minimal surface lattice structure is fabricated using laser selective sintering thermoplastic polyurethane technology. Compression tests and finite element simulations analyze the hyperelastic response characteristics, including the element type, deformation behavior, elastic modulus, and energy absorption performance, elucidating the stress–strain curve of the flexible lattice structure. Upon analyzing the compressive mechanical properties of the uniform flexible triply periodic minimal surface structure, it is evident that the structure’s geometric shape and volume fraction predominantly influence its mechanical properties. Consequently, we delve into the advantages of gradient and hybrid lattice structure designs concerning their elasticity, energy absorption, and shock absorption.

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Tiwari, Ashish. "Future Directions and Research Gaps in Enhancing the Optical Properties of PMMA with Metamaterials". International Journal of Multidisciplinary Research in Science, Engineering and Technology 2, n. 12 (25 novembre 2023): 2303–9. http://dx.doi.org/10.15680/ijmrset.2019.0212013.

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Polymethyl methacrylate (PMMA) is a versatile polymer extensively used for its excellent optical clarity, mechanical properties, and ease of fabrication. However, to meet the demands of advanced optical and photonic technologies, PMMA’s intrinsic properties must be further enhanced. Integrating metamaterials—artificially engineered materials with unique electromagnetic properties—into PMMA has shown significant promise in overcoming these limitations. This paper provides a comprehensive review of the current research gaps and future directions in enhancing the optical properties of PMMA with metamaterials. The review identifies key challenges such as achieving uniform nanoparticle distribution, ensuring long-term stability, and developing scalable fabrication techniques. It also explores potential solutions, including advanced fabrication methods, long-term performance studies, and the development of multifunctional composites. By addressing these challenges, PMMA-metamaterial composites can be optimized for a wide range of high-performance applications, driving innovation in various industries. The paper emphasizes the importance of interdisciplinary collaboration and technological advancements in overcoming existing challenges and advancing the field. The integration of metamaterials into PMMA represents a transformative advancement in materials science, with the potential to revolutionize applications in optoelectronics, energy harvesting, medical devices, and flexible technologies. By addressing current research gaps and leveraging new technologies, PMMA-metamaterial composites can pave the way for innovative solutions and significant advancements in various high-performance applications.

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Pagliocca, Nicholas, Kazi Zahir Uddin, Ibnaj Anamika Anni, Chen Shen, George Youssef e Behrad Koohbor. "Flexible planar metamaterials with tunable Poisson’s ratios". Materials & Design 215 (marzo 2022): 110446. http://dx.doi.org/10.1016/j.matdes.2022.110446.

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Mazur, Ekaterina, e Igor Shishkovsky. "Additively Manufactured Hierarchical Auxetic Mechanical Metamaterials". Materials 15, n. 16 (15 agosto 2022): 5600. http://dx.doi.org/10.3390/ma15165600.

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Due to the ability to create structures with complex geometry at micro- and nanoscales, modern additive technologies make it possible to produce artificial materials (metamaterials) with properties different from those of conventional materials found in nature. One of the classes with special properties is auxetic materials—materials with a negative Poisson’s ratio. In the review, we collect research results on the properties of auxetics, based on analytical, experimental and numerical methods. Special attention of this review is paid to the consideration of the results obtained in studies of hierarchical auxetic materials. The wide interest in the hierarchical subclass of auxetics is explained by the additional advantages of structures, such as more flexible adjustment of the desired mechanical characteristics (the porosity, stiffness, specific energy absorption, degree of material release, etc.). Possibilities of biomedical applications of hierarchical auxetic materials, such as coronary stents, filtration and drug delivery systems, implants and many others, where the ability for high-precision tuning is required, are underlined.

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Tiwari, Ashish. "Enhancing the Optical Properties of PMMA with Metamaterials: Applications and Performance Analysis". International Journal of Multidisciplinary Research in Science, Engineering and Technology 3, n. 12 (25 novembre 2023): 1342–49. http://dx.doi.org/10.15680/ijmrset.2020.0312019.

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Polymethyl methacrylate (PMMA) is a versatile polymer extensively used for its excellent optical clarity, mechanical properties, and ease of fabrication. However, to meet the demands of advanced optical and photonic technologies, PMMA’s intrinsic properties must be further enhanced. Integrating metamaterials—artificially engineered materials with unique electromagnetic properties—into PMMA has shown significant promise in overcoming these limitations. This paper provides a comprehensive review of the specific applications and performance analysis of PMMA enhanced with various metamaterials. The review covers recent studies, highlighting how these composites perform in optoelectronics, flexible electronics, medical devices, energy harvesting, and environmental applications. Enhanced PMMA composites demonstrate improved light absorption, scattering, refractive index modification, and UV resistance, leading to significant performance improvements. The paper also discusses current research gaps and future directions, emphasizing the need for advanced fabrication techniques, long-term performance studies, and the development of multifunctional composites. By addressing these challenges, PMMA-metamaterial composites can be optimized for a wide range of high-performance applications, driving innovation in various industries.

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Hu, Fuwen, e Tian Li. "An Origami Flexiball-Inspired Metamaterial Actuator and Its In-Pipe Robot Prototype". Actuators 10, n. 4 (26 marzo 2021): 67. http://dx.doi.org/10.3390/act10040067.

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Usually, polyhedra are viewed as the underlying constructive cells of packing or tiling in many disciplines, including crystallography, protein folding, viruses structure, building architecture, etc. Here, inspired by the flexible origami polyhedra (commonly called origami flexiballs), we initially probe into their intrinsic metamaterial properties and robotized methods from fabrication to actuation. Firstly, the topology, geometries and elastic energies of shape shifting are analyzed for the three kinds of origami flexiballs with extruded outward rhombic faces. Provably, they meet the definitions of reconfigurable and transformable metamaterials with switchable stiffness and multiple degrees of freedom. Secondly, a new type of soft actuator with rhombic deformations is successfully put forward, different from soft bionic deformations like elongating, contracting, bending, twisting, spiraling, etc. Further, we redesign and fabricate the three-dimensional (3D) printable structures of origami flexiballs considering their 3D printability and foldability, and magnetically actuated them through the attachment of magnetoactive elastomer. Lastly, a fully soft in-pipe robot prototype is presented using the origami flexiball as an applicable attempt. Experimental work clearly suggests that the presented origami flexiball robot has good adaptability to various pipe sizes, and also can be easily expanded to different scales, or reconfigured into more complex metastructures by assembly. In conclusion, this research provides a newly interesting and illuminating member for the emerging families of mechanical metamaterials, soft actuators and soft robots.

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Liang, Xudong, e Alfred J. Crosby. "Uniaxial stretching mechanics of cellular flexible metamaterials". Extreme Mechanics Letters 35 (febbraio 2020): 100637. http://dx.doi.org/10.1016/j.eml.2020.100637.

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Deng, Bolei, Siqin Yu, Antonio E. Forte, Vincent Tournat e Katia Bertoldi. "Characterization, stability, and application of domain walls in flexible mechanical metamaterials". Proceedings of the National Academy of Sciences 117, n. 49 (20 novembre 2020): 31002–9. http://dx.doi.org/10.1073/pnas.2015847117.

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Domain walls, commonly occurring at the interface of different phases in solid-state materials, have recently been harnessed at the structural scale to enable additional modes of functionality. Here, we combine experimental, numerical, and theoretical tools to investigate the domain walls emerging upon uniaxial compression in a mechanical metamaterial based on the rotating-squares mechanism. We first show that these interfaces can be generated and controlled by carefully arranging a few phase-inducing defects. We establish an analytical model to capture the evolution of the domain walls as a function of the applied deformation. We then employ this model as a guideline to realize interfaces of complex shape. Finally, we show that the engineered domain walls modify the global response of the metamaterial and can be effectively exploited to tune its stiffness as well as to guide the propagation of elastic waves.

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Zhou, Shengru, Chao Liang, Ziqi Mei, Rongbo Xie, Zhenci Sun, Ji Li, Wenqiang Zhang, Yong Ruan e Xiaoguang Zhao. "Design and Implementation of a Flexible Electromagnetic Actuator for Tunable Terahertz Metamaterials". Micromachines 15, n. 2 (31 gennaio 2024): 219. http://dx.doi.org/10.3390/mi15020219.

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Actuators play a crucial role in microelectromechanical systems (MEMS) and hold substantial potential for applications in various domains, including reconfigurable metamaterials. This research aims to design, fabricate, and characterize structures for the actuation of the EMA. The electromagnetic actuator overcomes the lack of high drive voltage required by other actuators. The proposed actuator configuration comprises supporting cantilever beams with fixed ends, an integrated coil positioned above the cantilever’s movable plate, and a permanent magnet located beneath the cantilever’s movable plate to generate a static magnetic field. Utilizing flexible polyimide, the fabrication process of the EMA is simplified, overcoming limitations associated with silicon-based micromachining techniques. Furthermore, this approach potentially enables large-scale production of EMA, with displacement reaching up to 250 μm under a 100 mA current, thereby expanding their scope of applications in manufacturing. To demonstrate the function of the EMA, we integrated it with a metamaterial structure to form a compact, tunable terahertz absorber, demonstrating a potential for reconfigurable electromagnetic space.

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Hu, Songtao, Xiaobao Cao, Tom Reddyhoff, Debashis Puhan, Sorin-Cristian Vladescu, Jing Wang, Xi Shi, Zhike Peng, Andrew J. deMello e Daniele Dini. "Liquid repellency enhancement through flexible microstructures". Science Advances 6, n. 32 (agosto 2020): eaba9721. http://dx.doi.org/10.1126/sciadv.aba9721.

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Artificial liquid-repellent surfaces have attracted substantial scientific and industrial attention with a focus on creating functional topological features; however, the role of the underlying structures has been overlooked. Recent developments in micro-nanofabrication allow us now to construct a skin-muscle type system combining interfacial liquid repellence atop a mechanically functional structure. Specifically, we design surfaces comprising bioinspired, mushroom-like repelling heads and spring-like flexible supports, which are realized by three-dimensional direct laser lithography. The flexible supports elevate liquid repellency by resisting droplet impalement and reducing contact time. This, previously unknown, use of spring-like flexible supports to enhance liquid repellency provides an excellent level of control over droplet manipulation. Moreover, this extends repellent microstructure research from statics to dynamics and is envisioned to yield functionalities and possibilities by linking functional surfaces and mechanical metamaterials.

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Sekiguchi, Ten, Hidetaka Ueno, Vivek Anand Menon, Ryo Ichige, Yuya Tanaka, Hiroshi Toshiyoshi e Takaaki Suzuki. "UV-curable Polydimethylsiloxane Photolithography and Its Application to Flexible Mechanical Metamaterials". Sensors and Materials 35, n. 6 (27 giugno 2023): 1995. http://dx.doi.org/10.18494/sam4351.

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Li, Nan, Chenhao Xue, Shenggui Chen, Wurikaixi Aiyiti, Sadaf Bashir Khan, Jiahua Liang, Jianping Zhou e Bingheng Lu. "3D Printing of Flexible Mechanical Metamaterials: Synergistic Design of Process and Geometric Parameters". Polymers 15, n. 23 (24 novembre 2023): 4523. http://dx.doi.org/10.3390/polym15234523.

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Mechanical metamaterials with ultralight and ultrastrong mechanical properties are extensively employed in various industrial sectors, with three-periodic minimal surface (TPMS) structures gaining significant research attention due to their symmetry, equation-driven characteristics, and exceptional mechanical properties. Compared to traditional lattice structures, TPMS structures exhibit superior mechanical performance. The mechanical properties of TPMS structures depend on the base material, structural porosity (volume fraction), and wall thickness. Hard rigid lattice structures such as Gyroid, diamond, and primitive exhibit outstanding performance in terms of elastic modulus, energy absorption, heat dissipation, and heat transfer. Flexible TPMS lattice structures, on the other hand, offer higher elasticity and recoverable large deformations, drawing attention for use in applications such as seat cushions and helmet impact-absorbing layers. Conventional fabrication methods often fail to guarantee the quality of TPMS structure samples, and additive manufacturing technology provides a new avenue. Selective laser sintering (SLS) has successfully been used to process various materials. However, due to the layer-by-layer manufacturing process, it cannot eliminate the anisotropy caused by interlayer bonding, which impacts the mechanical properties of 3D-printed parts. This paper introduces a process data-driven optimization design approach for TPMS structure geometry by adjusting volume fraction gradients to overcome the elastic anisotropy of 3D-printed isotropic lattice structures. Experimental validation and analysis are conducted using TPMS structures fabricated using TPU material via SLS. Furthermore, the advantages of volume fraction gradient-designed TPMS structures in functions such as energy absorption and heat dissipation are explored.

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Dunne, Jai. "Chainmail inspired metamaterials for use in protective sports equipment". Graduate Journal of Sports Science, Coaching, Management, & Rehabilitation 1, n. 3 (7 giugno 2024): 36. http://dx.doi.org/10.19164/gjsscmr.v1i3.1509.

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Contact sports and action sports require intense performance yet also include a high risk of injury. Subsequently, protective equipment for those sports usually must trade flexibility for protection and vice versa. Chainmail inspired mechanical metamaterials could be a solution to this dilemma. Chainmail is a type of body armour, consisting of a structured fabric made up of thousands of interlocking metallic rings. Chainmail inspired materials have recently been made from connected 3D shapes, rather than the typical 2D (flat) rings. This chainmail inspired material is flexible when relaxed but stiff when the chains are compressed together. This ability to control the material’s stiffness means chainmail is a type of mechanical metamaterial. Mechanical metamaterials are engineered structures which derive their properties from the structure of the material, not the material itself. In relation to protective equipment, this means that these chainmail materials or fabrics, can be flexible during normal use but stiffen when indented or impacted. The flexibility of these materials can be influenced by changing the size and shape of the connecting chains but to what extent and the effect this has on their stiffness is unknown. This type of structure could improve sporting protective equipment, where (as stated before) there are various trade-offs. The aim of this project was to develop a chainmail inspired material and test the effect of varying cell sizes has on the flexibility and indentation resistance of the material. Additive manufacturing was used to create the chainmail materials and a range of indenters were used to test them, the results of which indicate that as cell size decreases and number of cells increase; their flexibility and formability increases while also maintaining a good degree of indentation resistance, when compared to larger cell sizes. Based on this work, these structures could be tailored to different sporting protective equipment where flexibility, support, and stiffness requirements may vary between normal use and collisions or falls. These chainmail inspired materials could have various applications in contact sports such as rugby, American football and ice hockey where protection for players is key to reduce the severity of injuries. Similarly, action sports such as mountain biking, skateboarding, skiing and snowboarding also necessitate a high degree of protection. An Alternative application for these materials could be as a first aid device, where the material would be formed around the injury site as a brace and stiffened with compression, such as a vacuum pack.

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Luo, Sisi, Jianjiao Hao, Fuju Ye, Jiaxin Li, Ying Ruan, Haoyang Cui, Wenjun Liu e Lei Chen. "Evolution of the Electromagnetic Manipulation: From Tunable to Programmable and Intelligent Metasurfaces". Micromachines 12, n. 8 (20 agosto 2021): 988. http://dx.doi.org/10.3390/mi12080988.

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Looking back on the development of metamaterials in the past 20 years, metamaterials have gradually developed from three-dimensional complex electromagnetic structures to a two-dimensional metasurface with a low profile, during which a series of subversive achievements have been produced. The form of electromagnetic manipulation of the metasurface has evolved from passive to active tunable, programmable, and other dynamic and real-time controllable forms. In particular, the proposal of coding and programmable metasurfaces endows metasurfaces with new vitality. By describing metamaterials through binary code, the digital world and the physical world are connected, and the research of metasurfaces also steps into a new era of digitalization. However, the function switch of traditional programmable metamaterials cannot be achieved without human instruction and control. In order to achieve richer and more flexible function regulation and even higher level metasurface design, the intelligence of metamaterials is an important direction in its future development. In this paper, we review the development of tunable, programmable, and intelligent metasurfaces over the past 5 years, focusing on basic concepts, working principles, design methods, manufacturing, and experimental validation. Firstly, several manipulation modes of tunable metasurfaces are discussed; in particular, the metasurfaces based on temperature control, mechanical control, and electrical control are described in detail. It is demonstrated that the amplitude and phase responses can be flexibly manipulated by the tunable metasurfaces. Then, the concept, working principle, and design method of digital coding metasurfaces are briefly introduced. At the same time, we introduce the active programmable metasurfaces from the following aspects, such as structure, coding method, and three-dimensional far-field results, to show the excellent electromagnetic manipulation ability of programmable metasurfaces. Finally, the basic concepts and research status of intelligent metasurfaces are discussed in detail. Different from the previous programmable metamaterials, which must be controlled by human intervention, the new intelligent metamaterials control system will realize autonomous perception, autonomous decision-making, and even adaptive functional manipulation to a certain extent.

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Li, Jian, Yi Yuan, Jiao Wang, Ronghao Bao e Weiqiu Chen. "Propagation of nonlinear waves in graded flexible metamaterials". International Journal of Impact Engineering 156 (ottobre 2021): 103924. http://dx.doi.org/10.1016/j.ijimpeng.2021.103924.

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Bar-Sinai, Yohai, Gabriele Librandi, Katia Bertoldi e Michael Moshe. "Geometric charges and nonlinear elasticity of two-dimensional elastic metamaterials". Proceedings of the National Academy of Sciences 117, n. 19 (29 aprile 2020): 10195–202. http://dx.doi.org/10.1073/pnas.1920237117.

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Problems of flexible mechanical metamaterials, and highly deformable porous solids in general, are rich and complex due to their nonlinear mechanics and the presence of nontrivial geometrical effects. While numeric approaches are successful, analytic tools and conceptual frameworks are largely lacking. Using an analogy with electrostatics, and building on recent developments in a nonlinear geometric formulation of elasticity, we develop a formalism that maps the two-dimensional (2D) elastic problem into that of nonlinear interaction of elastic charges. This approach offers an intuitive conceptual framework, qualitatively explaining the linear response, the onset of mechanical instability, and aspects of the postinstability state. Apart from intuition, the formalism also quantitatively reproduces full numeric simulations of several prototypical 2D structures. Possible applications of the tools developed in this work for the study of ordered and disordered 2D porous elastic metamaterials are discussed.

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Chen, Xing, Li Cai e Jihong Wen. "Extreme mechanical metamaterials with independently adjustable elastic modulus and mass density". Applied Physics Express 15, n. 4 (8 marzo 2022): 047001. http://dx.doi.org/10.35848/1882-0786/ac5872.

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Abstract The mechanical properties of artificially periodic structures are closely related to the geometric dimensions of the structures. In this letter, we derive analytical expressions for the equivalent elastic parameters of a hexagonal cellular structure with additional counterweight mass blocks, and the accuracy of these analytical expressions is verified by numerical results. By analyzing the analytical expressions, we rigorously demonstrate an approximate decoupling relationship between the elastic modulus and mass density. Finally, we creatively propose a structure that can simultaneously achieve perfect decoupling of elastic modulus and mass density as well as flexible adjustment of material parameters in an ultra-wide range.

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Filipov, Evgueni T., Tomohiro Tachi e Glaucio H. Paulino. "Origami tubes assembled into stiff, yet reconfigurable structures and metamaterials". Proceedings of the National Academy of Sciences 112, n. 40 (8 settembre 2015): 12321–26. http://dx.doi.org/10.1073/pnas.1509465112.

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Thin sheets have long been known to experience an increase in stiffness when they are bent, buckled, or assembled into smaller interlocking structures. We introduce a unique orientation for coupling rigidly foldable origami tubes in a “zipper” fashion that substantially increases the system stiffness and permits only one flexible deformation mode through which the structure can deploy. The flexible deployment of the tubular structures is permitted by localized bending of the origami along prescribed fold lines. All other deformation modes, such as global bending and twisting of the structural system, are substantially stiffer because the tubular assemblages are overconstrained and the thin sheets become engaged in tension and compression. The zipper-coupled tubes yield an unusually large eigenvalue bandgap that represents the unique difference in stiffness between deformation modes. Furthermore, we couple compatible origami tubes into a variety of cellular assemblages that can enhance mechanical characteristics and geometric versatility, leading to a potential design paradigm for structures and metamaterials that can be deployed, stiffened, and tuned. The enhanced mechanical properties, versatility, and adaptivity of these thin sheet systems can provide practical solutions of varying geometric scales in science and engineering.

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Saoud, Ahmad, Diogo Queiros-Conde, Ahmad Omar e Thomas Michelitsch. "Intelligent Anti-Seismic Foundation: The Role of Fractal Geometry". Buildings 13, n. 8 (25 luglio 2023): 1891. http://dx.doi.org/10.3390/buildings13081891.

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Safe and resistant infrastructure is an essential component of public safety. However, existing structures are vulnerable to damage resulting from excessive ground movement due to seismic activity or underground explosions. The aim of this paper, which is part of an extensive study, is to develop an isolation system based on periodic materials with H-fractal geometry in order to obstruct, absorb or completely modify the pattern of seismic energy before it reaches the foundations of structures. Fractal metamaterial structures have shown promise for increasing the frequency range prohibited for seismic protection. We report the anti-seismic properties of a seismic metamaterial model based on an H-shaped quasi-fractal cell. The fractal design, also known as seismic metamaterials, has an important impact on the band structures of seismic crystals. Using the fractal as a base unit, anti-seismic phononic crystals were developed, and their band-gap characteristics were shown to display unique features due to the increasing wave propagation path and hybridization between local resonances and Bragg scattering. The seismic–mechanical duality is supposed to provide flexible solutions capable of increasing/widening the band-gaps to improve the level of seismic protection.

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Wang, Zhigang, Qi Wu, Yifei Lu, Panpan Bao, Yu Yang, Daochun Li, Xiasheng Sun e Jinwu Xiang. "Design of a Distributedly Active Morphing Wing Based on Digital Metamaterials". Aerospace 9, n. 12 (27 novembre 2022): 762. http://dx.doi.org/10.3390/aerospace9120762.

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Morphing wings are a typical application of shape-adaptive structures in aviation, which play an important role in improving the comprehensive performance of an aircraft. However, traditional morphing wings based on purely mechanical, rigid-flexible coupling, or purely flexible structures usually cannot achieve a distributed morphing ability and have limitations in weight, intelligence level, and reliability. In this paper, a distributed morphing lattice structure based on variable geometry digital metamaterials is proposed. The innovative structural concept consists of three types of fundamental cells featuring remarkably different mechanical properties and three other types of derived cells. One type of the derived cells embedded with micro-actuators, named an active cell, can autonomously extend or contract. All these cells can be reversibly assembled in a random sequence to form an active distributed morphing lattice structure with the ability to realize different target aerodynamic contours. In addition, taking a simplified variable thickness wing as a designing case, this paper develops a cell combination optimization methodology on the basis of a heuristic algorithm to determine the optimal combination sequence of the six types of basic cells and the actuator inputs of active cells collaboratively. Final results show that the optimized lattice structure can morph its outer surface into a predefined aerodynamic contour with a maximum deviation of 3 mm.

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Li, Jian, Ronghao Bao e Weiqiu Chen. "Exploring static responses, mode transitions, and feasible tunability of Kagome-based flexible mechanical metamaterials". Journal of the Mechanics and Physics of Solids 186 (maggio 2024): 105599. http://dx.doi.org/10.1016/j.jmps.2024.105599.

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Effah, Elijah, Ezekiel Edward Nettey-Oppong, Ahmed Ali, Kyung Min Byun e Seung Ho Choi. "Tunable Metasurfaces Based on Mechanically Deformable Polymeric Substrates". Photonics 10, n. 2 (23 gennaio 2023): 119. http://dx.doi.org/10.3390/photonics10020119.

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The emergence of metamaterials has presented an unprecedented platform to control the fundamental properties of light at the nanoscale. Conventional metamaterials, however, possess passive properties that cannot be modulated post-fabrication, limiting their application spectrum. Recent metasurface research has explored a plethora of active control mechanisms to modulate the optical properties of metasurfaces post-fabrication. A key active control mechanism of optical properties involves the use of mechanical deformation, aided by deformable polymeric substrates. The use of deformable polymeric substrates enables dynamic tuning of the optical properties of metasurfaces including metalenses, metaholograms, resonance, and structural colors, which are collectively relevant for biosensing and bioimaging. Deformable–stretchable metasurfaces further enable conformable and flexible optics for wearable applications. To extend deformable–stretchable metasurfaces to biocompatible metasurfaces, a fundamental and comprehensive primer is required. This review covers the underlying principles that govern the highlighted representative metasurface applications, encompassing stretchable metalenses, stretchable metaholograms, tunable structural colors, and tunable plasmonic resonances, while highlighting potential advancements for sensing, imaging, and wearable biomedical applications.

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Zhuang, Shulei, Xinyu Li, Tong Yang, Lu Sun, Olga Kosareva, Cheng Gong e Weiwei Liu. "Graphene-Based Absorption–Transmission Multi-Functional Tunable THz Metamaterials". Micromachines 13, n. 8 (1 agosto 2022): 1239. http://dx.doi.org/10.3390/mi13081239.

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The paper reports an absorption–transmission multifunctional tunable metamaterial based on graphene. Its pattern graphene layer can achieve broadband absorption, while the frequency selective layer can achieve the transmission of specific band. Furthermore, the absorption and transmission can be controlled by applying voltage to regulate the chemical potential of graphene. The analysis results show that the absorption of the metamaterial is adjustable from 22% to 99% in the 0.72 THz~1.26 THz band and the transmittance is adjustable from 80% to 95% in 2.35 THz. The metamaterial uses UV glue as the dielectric layer and PET (polyethylene terephthalate) as the flexible substrate, which has good flexibility. Moreover, the metamaterial is insensitive to incident angle and polarization angle, which is beneficial to achieve excellent conformal properties.

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Song, Yihao, e Yanfeng Shen. "Highly morphing and reconfigurable fluid–solid interactive metamaterials for tunable ultrasonic guided wave control". Applied Physics Letters 121, n. 26 (26 dicembre 2022): 264102. http://dx.doi.org/10.1063/5.0117634.

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Fluid–structural interactions enable the alternation of local resonance behaviors of elastic metamaterial unit cells. Magnetically active ferrofluids facilitate reconfiguration couplings for breaking and tunneling ultrasonic wave energy transmission. This Letter presents a magnetic fluid–solid interactive metamaterial to achieve the tunable manipulation of multimodal, dispersive ultrasonic guided waves. It is revealed that the phenomenon of the fluid–structure interaction plays an indispensable role in the achievement of bandgap formation and translation. The tunable mechanism stems from the variation of the fluid–solid coupling reconfiguration arising from liquid morphing via electromagnetic stimuli. The tunable wave control performance was explicitly validated through both numerical simulations and experimental verifications. Such an active metamaterial system may possess application potential for future highly flexible and tunable wave control, e.g., selective-tunnel waveguiding and adaptive mechanical frequency filtering.

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Feng, Xiaobin, Ke Cao, Xiege Huang, Guodong Li e Yang Lu. "Nanolayered CoCrFeNi/Graphene Composites with High Strength and Crack Resistance". Nanomaterials 12, n. 12 (20 giugno 2022): 2113. http://dx.doi.org/10.3390/nano12122113.

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Emerging high-entropy alloy (HEA) films achieve high strength but generally show ineludible brittle fractures, strongly restricting their micro/nano-mechanical and functional applications. Nanolayered (NL) CoCrFeNi/graphene composites are elaborately fabricated via magnetron sputtering and the transfer process. It is uncovered that NL CoCrFeNi/graphene composite pillars exhibit a simultaneous ultra-high strength of 4.73 GPa and considerable compressive plasticity of over 20%. Detailed electron microscope observations and simulations reveal that the monolayer graphene interface can effectively block the crack propagation and stimulate dislocations to accommodate further deformation. Our findings open avenues for the fabrication of high-performance, HEA-based composites, thereby addressing the challenges and unmet needs in flexible electronics and mechanical metamaterials.

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Kim, Jang Hwan, Su Eon Lee e Bong Hoon Kim. "Applications of flexible and stretchable three-dimensional structures for soft electronics". Soft Science 3, n. 2 (2023): 16. http://dx.doi.org/10.20517/ss.2023.07.

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The development of devices that can be mechanically deformed in geometrical layouts, such as flexible/stretchable devices, is important for various applications. Conventional flexible/stretchable devices have been demonstrated using two-dimensional (2D) geometry, resulting in dimensional constraints on device operations and functionality limitations. Accordingly, expanding the dimensions in which such devices can operate and acquiring unique functionality that is difficult to implement in 2D planar structures remain challenging. As a solution, the development of a flexible/stretchable device embedding a three-dimensional (3D) structure fabricated through the precise control of a 2D structure or direct construction has been attracting significant attention. Because of a significant amount of effort, several 3D material systems with distinctive engineering properties, including electrical, optical, thermal, and mechanical properties, which are difficult to occur in nature or to obtain in usual 2D material systems, have been demonstrated. Furthermore, 3D advanced material systems with flexibility and stretchability can provide additional options for developing devices with various form factors. In this review, novel fabrication methods and unprecedented physical properties of flexible/stretchable 3D material systems are reviewed through multiple application cases. In addition, we summarized the latest advances and trends in innovative applications implemented through the introduction of advanced 3D systems in various fields, including microelectromechanical systems, optoelectronics, energy devices, biomedical devices, sensors, actuators, metamaterials, and microfluidic systems.

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Yu, Junmin, Can Nerse, Kyoung-jin Chang e Semyung Wang. "A framework of flexible locally resonant metamaterials for attachment to curved structures". International Journal of Mechanical Sciences 204 (agosto 2021): 106533. http://dx.doi.org/10.1016/j.ijmecsci.2021.106533.

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Yu, Tianyu, Feilong Zhu, Xiongqi Peng e Zixuan Chen. "Acetylated Nanocelluloses Reinforced Shape Memory Epoxy with Enhanced Mechanical Properties and Outstanding Shape Memory Effect". Nanomaterials 12, n. 23 (22 novembre 2022): 4129. http://dx.doi.org/10.3390/nano12234129.

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Shape memory polymers (SMPs) have aroused much attention owing to their large deformation and programmability features. Nevertheless, the unsatisfactory toughness and brittleness of SMPs still restrict their practical intelligent applications, e.g., textiles, flexible electronics, and metamaterials. This study employed nature-derived nanocelluloses (NCs) as the reinforcement to fabricate shape memory epoxy-based nanocomposites (SMEPNs). An acetylation modification approach was further proposed to ameliorate the intrinsic incompatibility between NCs and epoxy matrix. The storage modulus increases, and the shape memory effect (SME) sustains after acetylated nanocelluloses (ANCs) incorporation. The SMEPNs with 0.06 wt.% ANCs loading perform the most exceptional toughness improvement over 42%, along with the enhanced fracture strain, elastic modulus, and ultimate strength. The incorporated nanoscale ANCs effectively impede crack propagation without deterioration of the macromolecular movability, resulting in excellent mechanical properties and SME.

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Hu, Jiaming, Junyi Wang, Yu Xie, Chenzhi Shi e Yun Chen. "Finite Element Analysis on Acoustic and Mechanical Performance of Flexible Perforated Honeycomb-Corrugation Hybrid Sandwich Panel". Shock and Vibration 2021 (16 maggio 2021): 1–14. http://dx.doi.org/10.1155/2021/9977644.

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Since proposed, the perforated honeycomb-corrugation sandwich panel has attracted a lot of attention due to its superior broadband sound absorption at low frequencies and excellent mechanical stiffness/strength. However, most existing studies have assumed a structure made of high-strength materials and studied its performance based on the ideal rigid-wall model with little consideration for acoustic-structure interaction, thereby neglecting the structural vibrations caused by the material’s elasticity. In this paper, we developed a more realistic model considering the solid structural dynamics using the finite element method (FEM) and by applying aluminum and rubber as the structural material. The enhancement of the low-frequency performance and inhibition of broadband absorption coexisted in low-strength rubbers, implying a compromise in the selection of Young's modulus to balance these two influences. Further analysis on thermal-viscous dissipation, mechanical energy, and average structural stress indicated that the structure should work right below the resonant frequency for optimization. Based on these findings, we designed a novel aluminum-rubber composite structure possessing enhanced low-frequency absorption, high resistance to shear load, normal compression, and thermal expansion. Our research is expected to shed some light on noise control and the design of multifunctional acoustic metamaterials.

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Tzarouchis, Dimitrios C., Maria Koutsoupidou, Ioannis Sotiriou, Konstantinos Dovelos, Dionysios Rompolas e Panagiotis Kosmas. "Electromagnetic metamaterials for biomedical applications: short review and trends". EPJ Applied Metamaterials 11 (2024): 7. http://dx.doi.org/10.1051/epjam/2024006.

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This mini-review examines the most prominent features and usages of metamaterials, such as metamaterial-based and metamaterial-inspired RF components used for biomedical applications. Emphasis is given to applications on sensing and imaging systems, wearable and implantable antennas for telemetry, and metamaterials used as flexible absorbers for protection against extreme electromagnetic (EM) radiation. A short discussion and trends on the metamaterial composition, implementation, and phantom preparation are presented. This review seeks to compile the state-of-the-art biomedical systems that utilize metamaterial concepts for enhancing their performance in some form or another. The goal is to highlight the diverse applications of metamaterials and demonstrate how different metamaterial techniques impact EM biomedical applications from RF to THz frequency range. Insights and open problems are discussed, illuminating the prototyping process.

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Jung, Junbo, Siwon Yoon, Bumjoo Kim e Joong Bae Kim. "Development of High-Performance Flexible Radiative Cooling Film Using PDMS/TiO2 Microparticles". Micromachines 14, n. 12 (10 dicembre 2023): 2223. http://dx.doi.org/10.3390/mi14122223.

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Radiative cooling, which cools an object below its surrounding temperature without any energy consumption, is one of the most promising techniques for zero-energy systems. In principle, the radiative cooling technique reflects incident solar energy and emits its thermal radiation energy into outer space. To achieve maximized cooling performance, it is crucial to attain high spectral reflectance in the solar spectrum (0.3–2.5 μm) and high spectral emittance in the atmospheric window (8–13 μm). Despite the development of various radiative cooling techniques such as photonic crystals and metamaterials, applying the cooling technology in practical applications remains challenging due to its low flexibility and complicated manufacturing processes. Here, we develop a high-performance radiative cooling film using PDMS/TiO2 microparticles. Specifically, the design parameters such as microparticle diameter, microparticle volume fraction, and film thickness are considered through optical analysis. Additionally, we propose a novel fabrication process using low viscosity silicone oil for practical fabrication. The fabricated film accomplishes 67.1 W/m2 of cooling power, and we also analyze the cooling performance difference depending on the fabrication process based on the measurement and optical calculation results.

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Huang, Xin, Wei Guo, Shaoyu Liu, Yangyang Li, Yuqi Qiu, Han Fang, Ganguang Yang et al. "Flexible Mechanical Metamaterials Enabled Electronic Skin for Real‐Time Detection of Unstable Grasping in Robotic Manipulation (Adv. Funct. Mater. 23/2022)". Advanced Functional Materials 32, n. 23 (giugno 2022): 2270131. http://dx.doi.org/10.1002/adfm.202270131.

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Hu, Zhou, Zhibo Wei, Kun Wang, Yan Chen, Rui Zhu, Guoliang Huang e Gengkai Hu. "Engineering zero modes in transformable mechanical metamaterials". Nature Communications 14, n. 1 (7 marzo 2023). http://dx.doi.org/10.1038/s41467-023-36975-2.

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AbstractIn the field of flexible metamaterial design, harnessing zero modes plays a key part in enabling reconfigurable elastic properties of the metamaterial with unconventional characteristics. However, only quantitative enhancement of certain properties succeeds in most cases rather than qualitative transformation of the metamaterials’ states or/and functionalities, due to the lack of systematic designs on the corresponding zero modes. Here, we propose a 3D metamaterial with engineered zero modes, and experimentally demonstrate its transformable static and dynamic properties. All seven types of extremal metamaterials ranging from null-mode (solid state) to hexa-mode (near-gaseous state) are reported to be reversibly transformed from one state to another, which is verified by the 3D-printed Thermoplastic Polyurethanes prototypes. Tunable wave manipulations are further investigated in 1D-, 2D- and 3D-systems. Our work sheds lights on the design of flexible mechanical metamaterials, which can be potentially extended from the mechanical to the electro-magnetite, the thermal or other types.

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Bertoldi, Katia, Vincenzo Vitelli, Johan Christensen e Martin van Hecke. "Flexible mechanical metamaterials". Nature Reviews Materials 2, n. 11 (17 ottobre 2017). http://dx.doi.org/10.1038/natrevmats.2017.66.

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Yang, Haiying, Haibao Lu, Dong-Wei Shu e Yong Qing (Richard) Fu. "Multimodal origami shape memory metamaterials undergoing compression-twist coupling". Smart Materials and Structures, 8 giugno 2023. http://dx.doi.org/10.1088/1361-665x/acdcd7.

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Abstract As origami structures display designable and predictable folding or unfolding shape changes, the origami-inspired mechanical metamaterials have recently been extensively investigated for applications in metamaterial engineering. There were many previous studies on the conventional hexagonal Kresling origami structures, however, there are many issues such as structural optimizations and designable strategies for the mechanical metamaterials, which have not been solved. To solve these issues, in this study, we studied the influences of crease direction, the number of sides, and unit arrangement on the origami structures. Effects of these parameters on mechanical properties and deformation behaviors of metamaterials were analyzed using finite element methods and experimental verifications. By adjusting the number of sides, the switching between monostability and bistability of the metamaterials was realized. The compression-twist coupling effect of these metamaterials can be adjustable and tailorable by arranging the chosen units in series. Designed foldable metamaterials are flexible, especially in their unfolding and folding directions, resulting in the achievement of an unstable compression state, i.e., the externally applied loads may cause the structure to unfold along the same compression path. Furthermore, shape memory polymer (SMP) has been printed using 3D printing technology to achieve the smart origami metamaterials, which endow the metamaterials with shape memory effect, self-adaptability and temperature-responsive mechanical behavior.

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El Helou, Charles, Philip R. Buskohl, Christopher E. Tabor e Ryan L. Harne. "Digital logic gates in soft, conductive mechanical metamaterials". Nature Communications 12, n. 1 (12 marzo 2021). http://dx.doi.org/10.1038/s41467-021-21920-y.

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AbstractIntegrated circuits utilize networked logic gates to compute Boolean logic operations that are the foundation of modern computation and electronics. With the emergence of flexible electronic materials and devices, an opportunity exists to formulate digital logic from compliant, conductive materials. Here, we introduce a general method of leveraging cellular, mechanical metamaterials composed of conductive polymers to realize all digital logic gates and gate assemblies. We establish a method for applying conductive polymer networks to metamaterial constituents and correlate mechanical buckling modes with network connectivity. With this foundation, each of the conventional logic gates is realized in an equivalent mechanical metamaterial, leading to soft, conductive matter that thinks about applied mechanical stress. These findings may advance the growing fields of soft robotics and smart mechanical matter, and may be leveraged across length scales and physics.

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Han, Donghai, Wenkang Li, Yushan Hou, Xiaoming Chen, Hongyu Shi, Fanqi Meng, Liuyang Zhang e Xuefeng Chen. "Controllable Wrinkling Inspired Multifunctional Metamaterial for Near‐Field and Holographic Displays". Laser & Photonics Reviews, 20 dicembre 2023. http://dx.doi.org/10.1002/lpor.202300879.

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AbstractTunable electromagnetic (EM) metamaterials have received significant attention due to their compelling advantages of integration and minimization compared with conventional bulky devices. Meanwhile, mechanically reconfigurable metamaterials have witnessed a striving period over recent years due to their simplified structural composition and confined modulation capabilities. Here, a controllable‐wrinkling‐based reconfiguration method is proposed to design split‐ring resonant units with dynamic transmittance spectra by switching between planar and wrinkling morphologies. For the linear polarized incidence, the geometries of planar and wrinkled units are optimized to achieve on‐demanded manipulation of the phases and amplitudes, respectively. By simultaneously implementing the amplitude design and the phase gradient, the mechanically inspired metamaterial is engineered to display a near‐field and a holographic image. For circularly polarized incidences, the spin‐decoupled phases and chiral effects demonstrated in the planar and wrinkled state assist in designing a metamaterial to possess spin‐multiplexed and strain‐modulated fourfold displays. These results demonstrate the practical feasibility of the wrinkling method in engineering tunable metamaterials, and the design flexibility, as well as the mechanical strategy, can extend the potential toward the application scenarios such as information processing, sensing, imaging, flexible meta‐devices, etc.

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Sano, Tomohiko G., Emile Hohnadel, Toshiyuki Kawata, Thibaut Métivet e Florence Bertails-Descoubes. "Randomly stacked open cylindrical shells as functional mechanical energy absorber". Communications Materials 4, n. 1 (25 agosto 2023). http://dx.doi.org/10.1038/s43246-023-00383-2.

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AbstractStructures with artificially engineered mechanical properties, often called mechanical metamaterials, are interesting for their tunable functionality. Various types of mechanical metamaterials have been proposed in the literature, designed to harness light or magnetic interactions, structural instabilities in slender or hollow structures, and contact friction. However, most of the designs are ideally engineered without any imperfections, in order to perform deterministically as programmed. Here, we study the mechanical performance of randomly stacked cylindrical shells, which act as a disordered mechanical metamaterial. Combining experiments and simulations, we demonstrate that the stacked shells can absorb and store mechanical energy upon compression by exploiting large deformation and relocation of shells, snap-fits, and friction. Although shells are oriented randomly, the system exhibits statistically robust mechanical performance controlled by friction and geometry. Our results demonstrate that the rearrangement of flexible components could yield versatile and predictive mechanical responses.

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