Publications
1.
Fang, Lichen; Li, Jing; Zhu, Zeyu; Orrego, Santiago; Kang, Sung Hoon
Piezoelectric polymer thin films with architected cuts Journal Article
In: Journal of Materials Research, vol. 33, no. 3, pp. 330-342, 2018, (Invited article on Focus Issue on Architected Materials).
@article{Fang2018,
title = {Piezoelectric polymer thin films with architected cuts},
author = {Lichen Fang and Jing Li and Zeyu Zhu and Santiago Orrego and Sung Hoon Kang},
editor = {Lorenzo Valdevit, Katia Bertoldi, James Guest, Christopher Spadaccini},
url = {https://www.cambridge.org/core/journals/journal-of-materials-research/article/piezoelectric-polymer-thin-films-with-architected-cuts/41109CD493CBADDE85D9446FCE3A95A7},
doi = {10.1557/jmr.2018.6},
year = {2018},
date = {2018-02-14},
journal = {Journal of Materials Research},
volume = {33},
number = {3},
pages = {330-342},
abstract = {Introducing architected cuts is an attractive and simple approach to tune mechanical behaviors of planar materials like thin films for desirable or enhanced mechanical performance. However, little has been studied on the effects of architected cuts on functional materials like piezoelectric materials. We investigated how architected cut patterns affect mechanical and piezoelectric properties of polyvinylidene fluoride thin films by numerical, experimental, and analytical studies. Our results show that thin films with architected cuts can provide desired mechanical features like enhanced compliance, stretchability, and controllable Poisson’s ratio and resonance frequency, while maintaining piezoelectric performance under static loadings. Moreover, we could observe maximum ∼30% improvement in piezoelectric conversion efficiency under dynamic loadings and harvest energy from low frequency (<100 Hz) mechanical signals or low velocity (<5 m/s) winds, which are commonly existing in ambient environment. Using architected cuts doesn't require changing the material or overall dimensions, making it attractive for applications in self-powered devices with design constraints.},
note = {Invited article on Focus Issue on Architected Materials},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Introducing architected cuts is an attractive and simple approach to tune mechanical behaviors of planar materials like thin films for desirable or enhanced mechanical performance. However, little has been studied on the effects of architected cuts on functional materials like piezoelectric materials. We investigated how architected cut patterns affect mechanical and piezoelectric properties of polyvinylidene fluoride thin films by numerical, experimental, and analytical studies. Our results show that thin films with architected cuts can provide desired mechanical features like enhanced compliance, stretchability, and controllable Poisson’s ratio and resonance frequency, while maintaining piezoelectric performance under static loadings. Moreover, we could observe maximum ∼30% improvement in piezoelectric conversion efficiency under dynamic loadings and harvest energy from low frequency (<100 Hz) mechanical signals or low velocity (<5 m/s) winds, which are commonly existing in ambient environment. Using architected cuts doesn’t require changing the material or overall dimensions, making it attractive for applications in self-powered devices with design constraints.
2.
Zárate, Yair; Babaee, Sahab; Kang, Sung H.; Neshev, Dragomir N.; Shadrivov, Ilya V.; Bertoldi, Katia; Powell, David A.
Elastic metamaterials for tuning circular polarization of electromagnetic waves Journal Article
In: Scientific Reports, vol. 6, pp. 28273, 2016.
@article{Zárate2016,
title = {Elastic metamaterials for tuning circular polarization of electromagnetic waves},
author = {Yair Zárate and Sahab Babaee and Sung H. Kang and Dragomir N. Neshev and Ilya V. Shadrivov and Katia Bertoldi and David A. Powell},
url = {http://www.nature.com/articles/srep28273},
doi = {doi:10.1038/srep28273},
year = {2016},
date = {2016-06-20},
journal = {Scientific Reports},
volume = {6},
pages = {28273},
abstract = {Electromagnetic resonators are integrated with advanced elastic material to develop a new type of tunable metamaterial. An electromagnetic-elastic metamaterial able to switch on and off its electromagnetic chiral response is experimentally demonstrated. Such tunability is attained by harnessing the unique buckling properties of auxetic elastic materials (buckliballs) with embedded electromagnetic resonators. In these structures, simple uniaxial compression results in a complex but controlled pattern of deformation, resulting in a shift of its electromagnetic resonance, and in the structure transforming to a chiral state. The concept can be extended to the tuning of three-dimensional materials constructed from the meta-molecules, since all the components twist and deform into the same chiral configuration when compressed.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Electromagnetic resonators are integrated with advanced elastic material to develop a new type of tunable metamaterial. An electromagnetic-elastic metamaterial able to switch on and off its electromagnetic chiral response is experimentally demonstrated. Such tunability is attained by harnessing the unique buckling properties of auxetic elastic materials (buckliballs) with embedded electromagnetic resonators. In these structures, simple uniaxial compression results in a complex but controlled pattern of deformation, resulting in a shift of its electromagnetic resonance, and in the structure transforming to a chiral state. The concept can be extended to the tuning of three-dimensional materials constructed from the meta-molecules, since all the components twist and deform into the same chiral configuration when compressed.
3.
Shan, Sicong; Kang, Sung H.; Zhao, Zhenhao; Fang, Lichen; Bertoldi, Katia
Design of planar isotropic negative Poisson’s ratio structures Journal Article
In: Extreme Mechanics Letters, vol. 4, pp. 96–102, 2015, ISSN: 2352-4316.
@article{Shan2015,
title = {Design of planar isotropic negative Poisson’s ratio structures},
author = {Sicong Shan and Sung H. Kang and Zhenhao Zhao and Lichen Fang and Katia Bertoldi},
url = {http://www.sciencedirect.com/science/article/pii/S2352431615000759},
doi = {10.1016/j.eml.2015.05.002},
issn = {2352-4316},
year = {2015},
date = {2015-05-21},
journal = {Extreme Mechanics Letters},
volume = {4},
pages = {96–102},
abstract = {Most of the auxetic materials that have been characterized experimentally or studied analytically are anisotropic and this limits their possible applications, as they need to be carefully oriented during operation. Here, through a combined numerical and experimental approach, we demonstrate that 2D auxetic materials with isotropic response can be easily realized by perforating a sheet with elongated cuts arranged to form a periodic pattern with either six-fold or three-fold symmetry. Moreover, we also show that the auxetic behavior can be easily tuned by varying the length of the cuts and that it is retained even under large levels of applied deformation beyond the limit of small strains. This novel, simple and scalable design can serve as an important guideline for designing and fabricating isotropic auxetic materials that can have a significant impact on a wide range of applications.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Most of the auxetic materials that have been characterized experimentally or studied analytically are anisotropic and this limits their possible applications, as they need to be carefully oriented during operation. Here, through a combined numerical and experimental approach, we demonstrate that 2D auxetic materials with isotropic response can be easily realized by perforating a sheet with elongated cuts arranged to form a periodic pattern with either six-fold or three-fold symmetry. Moreover, we also show that the auxetic behavior can be easily tuned by varying the length of the cuts and that it is retained even under large levels of applied deformation beyond the limit of small strains. This novel, simple and scalable design can serve as an important guideline for designing and fabricating isotropic auxetic materials that can have a significant impact on a wide range of applications.
4.
Shim, Jongmin; Shan, Sicong; Kosmrlj, Andrej; Kang, Sung Hoon; Chen, Elizabeth R.; Weaver, James C.; Bertoldi, Katia
Harnessing Instabilities for Design of Soft Reconfigurable Auxetic/Chiral Materials Journal Article
In: Soft Matter, vol. 9, pp. 8198-8202, 2013, (Highlighted on the Soft Matter blog.).
@article{Shim2013,
title = {Harnessing Instabilities for Design of Soft Reconfigurable Auxetic/Chiral Materials},
author = {Jongmin Shim and Sicong Shan and Andrej Kosmrlj and Sung Hoon Kang and Elizabeth R. Chen and James C. Weaver and Katia Bertoldi},
url = {http://pubs.rsc.org/en/content/articlelanding/2013/sm/c3sm51148k#!divAbstract},
year = {2013},
date = {2013-05-31},
journal = {Soft Matter},
volume = {9},
pages = {8198-8202},
abstract = {Most materials have a unique form optimized for a specific property and function. However, the ability to reconfigure material structures depending on stimuli opens exciting opportunities. Although mechanical instabilities have been traditionally viewed as a failure mode, here we exploit them to design a class of 2D soft materials whose architecture can be dramatically changed in response to an external stimulus. By considering geometric constraints on the tessellations of the 2D Euclidean plane, we have identified four possible periodic distributions of uniform circular holes where mechanical instability can be exploited to reversibly switch between expanded (i.e. with circular holes) and compact (i.e. with elongated, almost closed elliptical holes) periodic configurations. Interestingly, in all these structures buckling is found to induce large negative values of incremental Poisson's ratio and in two of them also the formation of chiral patterns. Using a combination of finite element simulations and experiments at the centimeter scale we demonstrate a proof-of-concept of the proposed materials. Since the proposed mechanism for reconfigurable materials is induced by elastic instability, it is reversible, repeatable and scale-independent.},
note = {Highlighted on the Soft Matter blog.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Most materials have a unique form optimized for a specific property and function. However, the ability to reconfigure material structures depending on stimuli opens exciting opportunities. Although mechanical instabilities have been traditionally viewed as a failure mode, here we exploit them to design a class of 2D soft materials whose architecture can be dramatically changed in response to an external stimulus. By considering geometric constraints on the tessellations of the 2D Euclidean plane, we have identified four possible periodic distributions of uniform circular holes where mechanical instability can be exploited to reversibly switch between expanded (i.e. with circular holes) and compact (i.e. with elongated, almost closed elliptical holes) periodic configurations. Interestingly, in all these structures buckling is found to induce large negative values of incremental Poisson’s ratio and in two of them also the formation of chiral patterns. Using a combination of finite element simulations and experiments at the centimeter scale we demonstrate a proof-of-concept of the proposed materials. Since the proposed mechanism for reconfigurable materials is induced by elastic instability, it is reversible, repeatable and scale-independent.
Note: Send e-mail to Prof. Kang at [email protected] if you need a pdf file of the papers below.
2018
Fang, Lichen; Li, Jing; Zhu, Zeyu; Orrego, Santiago; Kang, Sung Hoon
Piezoelectric polymer thin films with architected cuts Journal Article
In: Journal of Materials Research, vol. 33, no. 3, pp. 330-342, 2018, (Invited article on Focus Issue on Architected Materials).
Abstract | Links | BibTeX | Tags: architected materials, Auxetic, energy harvesting, kirigami, mechanical metamaterial, piezoelectric, stretchable electronics, wind energy
@article{Fang2018,
title = {Piezoelectric polymer thin films with architected cuts},
author = {Lichen Fang and Jing Li and Zeyu Zhu and Santiago Orrego and Sung Hoon Kang},
editor = {Lorenzo Valdevit, Katia Bertoldi, James Guest, Christopher Spadaccini},
url = {https://www.cambridge.org/core/journals/journal-of-materials-research/article/piezoelectric-polymer-thin-films-with-architected-cuts/41109CD493CBADDE85D9446FCE3A95A7},
doi = {10.1557/jmr.2018.6},
year = {2018},
date = {2018-02-14},
journal = {Journal of Materials Research},
volume = {33},
number = {3},
pages = {330-342},
abstract = {Introducing architected cuts is an attractive and simple approach to tune mechanical behaviors of planar materials like thin films for desirable or enhanced mechanical performance. However, little has been studied on the effects of architected cuts on functional materials like piezoelectric materials. We investigated how architected cut patterns affect mechanical and piezoelectric properties of polyvinylidene fluoride thin films by numerical, experimental, and analytical studies. Our results show that thin films with architected cuts can provide desired mechanical features like enhanced compliance, stretchability, and controllable Poisson’s ratio and resonance frequency, while maintaining piezoelectric performance under static loadings. Moreover, we could observe maximum ∼30% improvement in piezoelectric conversion efficiency under dynamic loadings and harvest energy from low frequency (<100 Hz) mechanical signals or low velocity (<5 m/s) winds, which are commonly existing in ambient environment. Using architected cuts doesn't require changing the material or overall dimensions, making it attractive for applications in self-powered devices with design constraints.},
note = {Invited article on Focus Issue on Architected Materials},
keywords = {architected materials, Auxetic, energy harvesting, kirigami, mechanical metamaterial, piezoelectric, stretchable electronics, wind energy},
pubstate = {published},
tppubtype = {article}
}
Introducing architected cuts is an attractive and simple approach to tune mechanical behaviors of planar materials like thin films for desirable or enhanced mechanical performance. However, little has been studied on the effects of architected cuts on functional materials like piezoelectric materials. We investigated how architected cut patterns affect mechanical and piezoelectric properties of polyvinylidene fluoride thin films by numerical, experimental, and analytical studies. Our results show that thin films with architected cuts can provide desired mechanical features like enhanced compliance, stretchability, and controllable Poisson’s ratio and resonance frequency, while maintaining piezoelectric performance under static loadings. Moreover, we could observe maximum ∼30% improvement in piezoelectric conversion efficiency under dynamic loadings and harvest energy from low frequency (<100 Hz) mechanical signals or low velocity (<5 m/s) winds, which are commonly existing in ambient environment. Using architected cuts doesn’t require changing the material or overall dimensions, making it attractive for applications in self-powered devices with design constraints.
2016
Zárate, Yair; Babaee, Sahab; Kang, Sung H.; Neshev, Dragomir N.; Shadrivov, Ilya V.; Bertoldi, Katia; Powell, David A.
Elastic metamaterials for tuning circular polarization of electromagnetic waves Journal Article
In: Scientific Reports, vol. 6, pp. 28273, 2016.
Abstract | Links | BibTeX | Tags: 3D printing, Auxetic, buckling, Chiral, electromagnetic, Metamaterial, Tunable
@article{Zárate2016,
title = {Elastic metamaterials for tuning circular polarization of electromagnetic waves},
author = {Yair Zárate and Sahab Babaee and Sung H. Kang and Dragomir N. Neshev and Ilya V. Shadrivov and Katia Bertoldi and David A. Powell},
url = {http://www.nature.com/articles/srep28273},
doi = {doi:10.1038/srep28273},
year = {2016},
date = {2016-06-20},
journal = {Scientific Reports},
volume = {6},
pages = {28273},
abstract = {Electromagnetic resonators are integrated with advanced elastic material to develop a new type of tunable metamaterial. An electromagnetic-elastic metamaterial able to switch on and off its electromagnetic chiral response is experimentally demonstrated. Such tunability is attained by harnessing the unique buckling properties of auxetic elastic materials (buckliballs) with embedded electromagnetic resonators. In these structures, simple uniaxial compression results in a complex but controlled pattern of deformation, resulting in a shift of its electromagnetic resonance, and in the structure transforming to a chiral state. The concept can be extended to the tuning of three-dimensional materials constructed from the meta-molecules, since all the components twist and deform into the same chiral configuration when compressed.},
keywords = {3D printing, Auxetic, buckling, Chiral, electromagnetic, Metamaterial, Tunable},
pubstate = {published},
tppubtype = {article}
}
Electromagnetic resonators are integrated with advanced elastic material to develop a new type of tunable metamaterial. An electromagnetic-elastic metamaterial able to switch on and off its electromagnetic chiral response is experimentally demonstrated. Such tunability is attained by harnessing the unique buckling properties of auxetic elastic materials (buckliballs) with embedded electromagnetic resonators. In these structures, simple uniaxial compression results in a complex but controlled pattern of deformation, resulting in a shift of its electromagnetic resonance, and in the structure transforming to a chiral state. The concept can be extended to the tuning of three-dimensional materials constructed from the meta-molecules, since all the components twist and deform into the same chiral configuration when compressed.
2015
Shan, Sicong; Kang, Sung H.; Zhao, Zhenhao; Fang, Lichen; Bertoldi, Katia
Design of planar isotropic negative Poisson’s ratio structures Journal Article
In: Extreme Mechanics Letters, vol. 4, pp. 96–102, 2015, ISSN: 2352-4316.
Abstract | Links | BibTeX | Tags: architected materials, Auxetic, Isotropic, Symmetry
@article{Shan2015,
title = {Design of planar isotropic negative Poisson’s ratio structures},
author = {Sicong Shan and Sung H. Kang and Zhenhao Zhao and Lichen Fang and Katia Bertoldi},
url = {http://www.sciencedirect.com/science/article/pii/S2352431615000759},
doi = {10.1016/j.eml.2015.05.002},
issn = {2352-4316},
year = {2015},
date = {2015-05-21},
journal = {Extreme Mechanics Letters},
volume = {4},
pages = {96–102},
abstract = {Most of the auxetic materials that have been characterized experimentally or studied analytically are anisotropic and this limits their possible applications, as they need to be carefully oriented during operation. Here, through a combined numerical and experimental approach, we demonstrate that 2D auxetic materials with isotropic response can be easily realized by perforating a sheet with elongated cuts arranged to form a periodic pattern with either six-fold or three-fold symmetry. Moreover, we also show that the auxetic behavior can be easily tuned by varying the length of the cuts and that it is retained even under large levels of applied deformation beyond the limit of small strains. This novel, simple and scalable design can serve as an important guideline for designing and fabricating isotropic auxetic materials that can have a significant impact on a wide range of applications.},
keywords = {architected materials, Auxetic, Isotropic, Symmetry},
pubstate = {published},
tppubtype = {article}
}
Most of the auxetic materials that have been characterized experimentally or studied analytically are anisotropic and this limits their possible applications, as they need to be carefully oriented during operation. Here, through a combined numerical and experimental approach, we demonstrate that 2D auxetic materials with isotropic response can be easily realized by perforating a sheet with elongated cuts arranged to form a periodic pattern with either six-fold or three-fold symmetry. Moreover, we also show that the auxetic behavior can be easily tuned by varying the length of the cuts and that it is retained even under large levels of applied deformation beyond the limit of small strains. This novel, simple and scalable design can serve as an important guideline for designing and fabricating isotropic auxetic materials that can have a significant impact on a wide range of applications.
2013
Shim, Jongmin; Shan, Sicong; Kosmrlj, Andrej; Kang, Sung Hoon; Chen, Elizabeth R.; Weaver, James C.; Bertoldi, Katia
Harnessing Instabilities for Design of Soft Reconfigurable Auxetic/Chiral Materials Journal Article
In: Soft Matter, vol. 9, pp. 8198-8202, 2013, (Highlighted on the Soft Matter blog.).
Abstract | Links | BibTeX | Tags: 3D printing, architected materials, Auxetic, Chiral, Mechanical Instability, mechanics of soft materials and structures, Metamaterial, Soft Periodic Porous Structures, Symmetry Breaking
@article{Shim2013,
title = {Harnessing Instabilities for Design of Soft Reconfigurable Auxetic/Chiral Materials},
author = {Jongmin Shim and Sicong Shan and Andrej Kosmrlj and Sung Hoon Kang and Elizabeth R. Chen and James C. Weaver and Katia Bertoldi},
url = {http://pubs.rsc.org/en/content/articlelanding/2013/sm/c3sm51148k#!divAbstract},
year = {2013},
date = {2013-05-31},
journal = {Soft Matter},
volume = {9},
pages = {8198-8202},
abstract = {Most materials have a unique form optimized for a specific property and function. However, the ability to reconfigure material structures depending on stimuli opens exciting opportunities. Although mechanical instabilities have been traditionally viewed as a failure mode, here we exploit them to design a class of 2D soft materials whose architecture can be dramatically changed in response to an external stimulus. By considering geometric constraints on the tessellations of the 2D Euclidean plane, we have identified four possible periodic distributions of uniform circular holes where mechanical instability can be exploited to reversibly switch between expanded (i.e. with circular holes) and compact (i.e. with elongated, almost closed elliptical holes) periodic configurations. Interestingly, in all these structures buckling is found to induce large negative values of incremental Poisson's ratio and in two of them also the formation of chiral patterns. Using a combination of finite element simulations and experiments at the centimeter scale we demonstrate a proof-of-concept of the proposed materials. Since the proposed mechanism for reconfigurable materials is induced by elastic instability, it is reversible, repeatable and scale-independent.},
note = {Highlighted on the Soft Matter blog.},
keywords = {3D printing, architected materials, Auxetic, Chiral, Mechanical Instability, mechanics of soft materials and structures, Metamaterial, Soft Periodic Porous Structures, Symmetry Breaking},
pubstate = {published},
tppubtype = {article}
}
Most materials have a unique form optimized for a specific property and function. However, the ability to reconfigure material structures depending on stimuli opens exciting opportunities. Although mechanical instabilities have been traditionally viewed as a failure mode, here we exploit them to design a class of 2D soft materials whose architecture can be dramatically changed in response to an external stimulus. By considering geometric constraints on the tessellations of the 2D Euclidean plane, we have identified four possible periodic distributions of uniform circular holes where mechanical instability can be exploited to reversibly switch between expanded (i.e. with circular holes) and compact (i.e. with elongated, almost closed elliptical holes) periodic configurations. Interestingly, in all these structures buckling is found to induce large negative values of incremental Poisson’s ratio and in two of them also the formation of chiral patterns. Using a combination of finite element simulations and experiments at the centimeter scale we demonstrate a proof-of-concept of the proposed materials. Since the proposed mechanism for reconfigurable materials is induced by elastic instability, it is reversible, repeatable and scale-independent.