Publications
1.
Fang, Lichen; Yan, Yishu; Agarwal, Ojaswi; Seppala, Jonathan E; Migler, Kalman D; Nguyen, Thao D; Kang, Sung Hoon
Estimations of the effective Young’s modulus of specimens prepared by fused filament fabrication Journal Article
In: Additive Manufacturing, vol. 42, pp. 101983, 2021.
@article{fang2021estimations,
title = {Estimations of the effective Young's modulus of specimens prepared by fused filament fabrication},
author = {Lichen Fang and Yishu Yan and Ojaswi Agarwal and Jonathan E Seppala and Kalman D Migler and Thao D Nguyen and Sung Hoon Kang},
url = {https://www.sciencedirect.com/science/article/abs/pii/S2214860421001482},
year = {2021},
date = {2021-01-01},
urldate = {2021-01-01},
journal = {Additive Manufacturing},
volume = {42},
pages = {101983},
publisher = {Elsevier},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
2.
Jeon, S. -Y.; Kang, S. H.
Electrochemical reactions drive morphing of materials Journal Article
In: Nature, vol. 573, pp. 198-199, 2019.
@article{Jeon2019,
title = {Electrochemical reactions drive morphing of materials},
author = {S.-Y. Jeon and S. H. Kang},
url = {https://www.nature.com/articles/d41586-019-02663-9},
doi = {10.1038/d41586-019-02663-9},
year = {2019},
date = {2019-09-11},
journal = {Nature},
volume = {573},
pages = {198-199},
abstract = {Silicon anodes in lithium batteries expand during discharge, causing failure. This expansion has been used constructively in a material whose architecture controllably and reversibly changes to alter its function.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Silicon anodes in lithium batteries expand during discharge, causing failure. This expansion has been used constructively in a material whose architecture controllably and reversibly changes to alter its function.
3.
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.
4.
Wang, Pai; Zheng, Yue; Fernandes, Matheus C.; Sun, Yushen; Xu, Kai; Sun, Sijie; Kang, Sung Hoon; Tournat, Vincent; Bertoldi, Katia
Harnessing Geometric Frustration to Form Band Gaps in Acoustic Channel Lattices Journal Article
In: Physical Review Letters, vol. 118, pp. 084302, 2017.
@article{Wang2017,
title = {Harnessing Geometric Frustration to Form Band Gaps in Acoustic Channel Lattices},
author = {Pai Wang and Yue Zheng and Matheus C. Fernandes and Yushen Sun and Kai Xu and Sijie Sun and Sung Hoon Kang and Vincent Tournat and Katia Bertoldi},
url = {https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.118.084302},
doi = {10.1103/PhysRevLett.118.084302},
year = {2017},
date = {2017-02-21},
journal = {Physical Review Letters},
volume = {118},
pages = {084302},
abstract = {We demonstrate both numerically and experimentally that geometric frustration in two-dimensional periodic acoustic networks consisting of arrays of narrow air channels can be harnessed to form band gaps (ranges of frequency in which the waves cannot propagate in any direction through the system). While resonant standing wave modes and interferences are ubiquitous in all the analyzed network geometries, we show that they give rise to band gaps only in the geometrically frustrated ones (i.e., those comprising of triangles and pentagons). Our results not only reveal a new mechanism based on geometric frustration to suppress the propagation of pressure waves in specific frequency ranges but also open avenues for the design of a new generation of smart systems that control and manipulate sound and vibrations.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We demonstrate both numerically and experimentally that geometric frustration in two-dimensional periodic acoustic networks consisting of arrays of narrow air channels can be harnessed to form band gaps (ranges of frequency in which the waves cannot propagate in any direction through the system). While resonant standing wave modes and interferences are ubiquitous in all the analyzed network geometries, we show that they give rise to band gaps only in the geometrically frustrated ones (i.e., those comprising of triangles and pentagons). Our results not only reveal a new mechanism based on geometric frustration to suppress the propagation of pressure waves in specific frequency ranges but also open avenues for the design of a new generation of smart systems that control and manipulate sound and vibrations.
5.
Liu, Jia; Gu, Tianyu; Shan, Sicong; Kang, Sung H.; Weaver, James C.; Bertoldi, Katia
Harnessing Buckling to Design Architected Materials that Exhibit Effective Negative Swelling Journal Article
In: Advanced Materials, vol. 28, pp. 6619–6624, 2016.
@article{Liu2016,
title = {Harnessing Buckling to Design Architected Materials that Exhibit Effective Negative Swelling},
author = {Jia Liu and Tianyu Gu and Sicong Shan and Sung H. Kang and James C. Weaver and Katia Bertoldi},
url = {http://onlinelibrary.wiley.com/doi/10.1002/adma.201600812/pdf},
doi = {10.1002/adma.201600812},
year = {2016},
date = {2016-05-17},
journal = {Advanced Materials},
volume = {28},
pages = {6619–6624},
abstract = {Inspired by the need to develop materials capable of targeted and extreme volume changes during operation, numerical simulations and experiments are combined to design a new class of soft architected materials that achieve a reduction of projected surface area coverage during swelling. },
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Inspired by the need to develop materials capable of targeted and extreme volume changes during operation, numerical simulations and experiments are combined to design a new class of soft architected materials that achieve a reduction of projected surface area coverage during swelling.
6.
Shan, Sicong; Kang, Sung H.; Raney, Jordan R.; Wang, Pai; Fang, Lichen; Candido, Francisco; Lewis, Jennifer A.; Bertoldi, Katia
Multistable Architected Materials for Trapping Elastic Strain Energy Journal Article
In: Advanced Materials, vol. 27, pp. 4296–4301, 2015, ISSN: 1521-4095, (SS, SHK, JRR: equal contribution).
@article{ADMA:ADMA201501708,
title = {Multistable Architected Materials for Trapping Elastic Strain Energy},
author = {Sicong Shan and Sung H. Kang and Jordan R. Raney and Pai Wang and Lichen Fang and Francisco Candido and Jennifer A. Lewis and Katia Bertoldi},
url = {http://dx.doi.org/10.1002/adma.201501708},
issn = {1521-4095},
year = {2015},
date = {2015-06-18},
journal = {Advanced Materials},
volume = {27},
pages = {4296–4301},
note = {SS, SHK, JRR: equal contribution},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
7.
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.
8.
Wang, Pai; Casadei, Filippo; Kang, Sung Hoon; Bertoldi, Katia
Locally resonant band gaps in periodic beam lattices by tuning connectivity Journal Article
In: Physical Review B (Rapid Communications), vol. 91, pp. 020103, 2015.
@article{Wang2015,
title = {Locally resonant band gaps in periodic beam lattices by tuning connectivity},
author = {Pai Wang and Filippo Casadei and Sung Hoon Kang and Katia Bertoldi},
url = {http://journals.aps.org/prb/pdf/10.1103/PhysRevB.91.020103},
year = {2015},
date = {2015-01-26},
journal = {Physical Review B (Rapid Communications)},
volume = {91},
pages = {020103},
abstract = {Lattice structures have long fascinated physicists and engineers not only because of their outstanding functionalities, but also for their ability to control the propagation of elastic waves. While the study of the relation between the connectivity of these systems and their static properties has a long history that goes back to Maxwell, rules that connect the dynamic response to the network topology have not been established. Here, we demonstrate that by tuning the average connectivity of a beam network (z ̄), locally resonant band gaps can be generated in the structures without embedding additional resonating units. In particular, a critical threshold for z ̄ is identified, far from which the band gap size is purely dictated by the global lattice topology. By contrast, near this critical value, the detailed local geometry of the lattice also has strong effects. Moreover, in stark contrast to the static case, we find that the nature of the joints is irrelevant to the dynamic response of the lattices. Our results not only shed new light on the rich dynamic properties of periodic lattices, but also outline a new strategy to manipulate mechanical waves in elastic systems.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Lattice structures have long fascinated physicists and engineers not only because of their outstanding functionalities, but also for their ability to control the propagation of elastic waves. While the study of the relation between the connectivity of these systems and their static properties has a long history that goes back to Maxwell, rules that connect the dynamic response to the network topology have not been established. Here, we demonstrate that by tuning the average connectivity of a beam network (z ̄), locally resonant band gaps can be generated in the structures without embedding additional resonating units. In particular, a critical threshold for z ̄ is identified, far from which the band gap size is purely dictated by the global lattice topology. By contrast, near this critical value, the detailed local geometry of the lattice also has strong effects. Moreover, in stark contrast to the static case, we find that the nature of the joints is irrelevant to the dynamic response of the lattices. Our results not only shed new light on the rich dynamic properties of periodic lattices, but also outline a new strategy to manipulate mechanical waves in elastic systems.
9.
Shan, Sicong; Kang, Sung Hoon; Wang, Pai; Qu, Cangyu; Shian, Samuel; Chen, Elizabeth R.; Weaver, James C.; Bertoldi, Katia
Harnessing Multiple Folding Mechanisms in Soft Periodic and Porous Structures to Design Highly Tunable Phononic Crystals Journal Article
In: Advanced Functional Materials, vol. 24, pp. 4935–4942, 2014.
@article{Shan2014,
title = {Harnessing Multiple Folding Mechanisms in Soft Periodic and Porous Structures to Design Highly Tunable Phononic Crystals},
author = {Sicong Shan and Sung Hoon Kang and Pai Wang and Cangyu Qu and Samuel Shian and Elizabeth R. Chen and James C. Weaver and Katia Bertoldi},
url = {http://onlinelibrary.wiley.com/doi/10.1002/adfm.201400665/abstract},
year = {2014},
date = {2014-08-20},
journal = {Advanced Functional Materials},
volume = {24},
pages = {4935–4942},
abstract = {Mechanical instabilities in periodic porous elastic structures may lead to the formation of homogeneous patterns, opening avenues for a wide range of applications that are related to the geometry of the system. This study focuses on an elastomeric porous structure comprising a triangular array of circular holes, and shows that by controlling the loading direction, multiple pattern transformations can be induced by buckling. Interestingly, these different pattern transformations can be exploited to design materials with highly tunable properties. In particular, these results indicate that they can be effectively used to tune the propagation of elastic waves in phononic crystals, enhancing the tunability of the dynamic response of the system. Using a combination of finite element simulations and experiments, a proof-of-concept of the novel material is demonstrated. Since the proposed mechanism is induced by elastic instability, it is reversible, repeatable, and scale-independent, opening avenues for the design of highly tunable materials and devices over a wide range of length scales.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Mechanical instabilities in periodic porous elastic structures may lead to the formation of homogeneous patterns, opening avenues for a wide range of applications that are related to the geometry of the system. This study focuses on an elastomeric porous structure comprising a triangular array of circular holes, and shows that by controlling the loading direction, multiple pattern transformations can be induced by buckling. Interestingly, these different pattern transformations can be exploited to design materials with highly tunable properties. In particular, these results indicate that they can be effectively used to tune the propagation of elastic waves in phononic crystals, enhancing the tunability of the dynamic response of the system. Using a combination of finite element simulations and experiments, a proof-of-concept of the novel material is demonstrated. Since the proposed mechanism is induced by elastic instability, it is reversible, repeatable, and scale-independent, opening avenues for the design of highly tunable materials and devices over a wide range of length scales.
10.
Kang, Sung Hoon; Bertoldi, Katia; Shan, Sicong
Shape Recoverable Reusable Energy Absorbing Structures, Systems and Methods for Manufacture Thereof Technical Report
2014, (United States Provisional Patent Application No. 61/983,782).
@techreport{Kang2014b,
title = {Shape Recoverable Reusable Energy Absorbing Structures, Systems and Methods for Manufacture Thereof},
author = {Sung Hoon Kang and Katia Bertoldi and Sicong Shan},
year = {2014},
date = {2014-04-24},
booktitle = {U.S. Provisional Patent Application No. 61/983,782},
note = {United States Provisional Patent Application No. 61/983,782},
keywords = {},
pubstate = {published},
tppubtype = {techreport}
}
11.
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.
2021
Fang, Lichen; Yan, Yishu; Agarwal, Ojaswi; Seppala, Jonathan E; Migler, Kalman D; Nguyen, Thao D; Kang, Sung Hoon
Estimations of the effective Young’s modulus of specimens prepared by fused filament fabrication Journal Article
In: Additive Manufacturing, vol. 42, pp. 101983, 2021.
Links | BibTeX | Tags: architected materials
@article{fang2021estimations,
title = {Estimations of the effective Young's modulus of specimens prepared by fused filament fabrication},
author = {Lichen Fang and Yishu Yan and Ojaswi Agarwal and Jonathan E Seppala and Kalman D Migler and Thao D Nguyen and Sung Hoon Kang},
url = {https://www.sciencedirect.com/science/article/abs/pii/S2214860421001482},
year = {2021},
date = {2021-01-01},
urldate = {2021-01-01},
journal = {Additive Manufacturing},
volume = {42},
pages = {101983},
publisher = {Elsevier},
keywords = {architected materials},
pubstate = {published},
tppubtype = {article}
}
2019
Jeon, S. -Y.; Kang, S. H.
Electrochemical reactions drive morphing of materials Journal Article
In: Nature, vol. 573, pp. 198-199, 2019.
Abstract | Links | BibTeX | Tags: 3D printing, architected materials, shape, Tunable
@article{Jeon2019,
title = {Electrochemical reactions drive morphing of materials},
author = {S.-Y. Jeon and S. H. Kang},
url = {https://www.nature.com/articles/d41586-019-02663-9},
doi = {10.1038/d41586-019-02663-9},
year = {2019},
date = {2019-09-11},
journal = {Nature},
volume = {573},
pages = {198-199},
abstract = {Silicon anodes in lithium batteries expand during discharge, causing failure. This expansion has been used constructively in a material whose architecture controllably and reversibly changes to alter its function.},
keywords = {3D printing, architected materials, shape, Tunable},
pubstate = {published},
tppubtype = {article}
}
Silicon anodes in lithium batteries expand during discharge, causing failure. This expansion has been used constructively in a material whose architecture controllably and reversibly changes to alter its function.
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.
2017
Wang, Pai; Zheng, Yue; Fernandes, Matheus C.; Sun, Yushen; Xu, Kai; Sun, Sijie; Kang, Sung Hoon; Tournat, Vincent; Bertoldi, Katia
Harnessing Geometric Frustration to Form Band Gaps in Acoustic Channel Lattices Journal Article
In: Physical Review Letters, vol. 118, pp. 084302, 2017.
Abstract | Links | BibTeX | Tags: Acoustic, architected materials, Band gap, Geometrical Frustration, Metamaterial
@article{Wang2017,
title = {Harnessing Geometric Frustration to Form Band Gaps in Acoustic Channel Lattices},
author = {Pai Wang and Yue Zheng and Matheus C. Fernandes and Yushen Sun and Kai Xu and Sijie Sun and Sung Hoon Kang and Vincent Tournat and Katia Bertoldi},
url = {https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.118.084302},
doi = {10.1103/PhysRevLett.118.084302},
year = {2017},
date = {2017-02-21},
journal = {Physical Review Letters},
volume = {118},
pages = {084302},
abstract = {We demonstrate both numerically and experimentally that geometric frustration in two-dimensional periodic acoustic networks consisting of arrays of narrow air channels can be harnessed to form band gaps (ranges of frequency in which the waves cannot propagate in any direction through the system). While resonant standing wave modes and interferences are ubiquitous in all the analyzed network geometries, we show that they give rise to band gaps only in the geometrically frustrated ones (i.e., those comprising of triangles and pentagons). Our results not only reveal a new mechanism based on geometric frustration to suppress the propagation of pressure waves in specific frequency ranges but also open avenues for the design of a new generation of smart systems that control and manipulate sound and vibrations.},
keywords = {Acoustic, architected materials, Band gap, Geometrical Frustration, Metamaterial},
pubstate = {published},
tppubtype = {article}
}
We demonstrate both numerically and experimentally that geometric frustration in two-dimensional periodic acoustic networks consisting of arrays of narrow air channels can be harnessed to form band gaps (ranges of frequency in which the waves cannot propagate in any direction through the system). While resonant standing wave modes and interferences are ubiquitous in all the analyzed network geometries, we show that they give rise to band gaps only in the geometrically frustrated ones (i.e., those comprising of triangles and pentagons). Our results not only reveal a new mechanism based on geometric frustration to suppress the propagation of pressure waves in specific frequency ranges but also open avenues for the design of a new generation of smart systems that control and manipulate sound and vibrations.
2016
Liu, Jia; Gu, Tianyu; Shan, Sicong; Kang, Sung H.; Weaver, James C.; Bertoldi, Katia
Harnessing Buckling to Design Architected Materials that Exhibit Effective Negative Swelling Journal Article
In: Advanced Materials, vol. 28, pp. 6619–6624, 2016.
Abstract | Links | BibTeX | Tags: architected materials, Mechanical Instability, mechanics of soft materials and structures, Reversible, Soft Periodic Porous Structures
@article{Liu2016,
title = {Harnessing Buckling to Design Architected Materials that Exhibit Effective Negative Swelling},
author = {Jia Liu and Tianyu Gu and Sicong Shan and Sung H. Kang and James C. Weaver and Katia Bertoldi},
url = {http://onlinelibrary.wiley.com/doi/10.1002/adma.201600812/pdf},
doi = {10.1002/adma.201600812},
year = {2016},
date = {2016-05-17},
journal = {Advanced Materials},
volume = {28},
pages = {6619–6624},
abstract = {Inspired by the need to develop materials capable of targeted and extreme volume changes during operation, numerical simulations and experiments are combined to design a new class of soft architected materials that achieve a reduction of projected surface area coverage during swelling. },
keywords = {architected materials, Mechanical Instability, mechanics of soft materials and structures, Reversible, Soft Periodic Porous Structures},
pubstate = {published},
tppubtype = {article}
}
Inspired by the need to develop materials capable of targeted and extreme volume changes during operation, numerical simulations and experiments are combined to design a new class of soft architected materials that achieve a reduction of projected surface area coverage during swelling.
2015
Shan, Sicong; Kang, Sung H.; Raney, Jordan R.; Wang, Pai; Fang, Lichen; Candido, Francisco; Lewis, Jennifer A.; Bertoldi, Katia
Multistable Architected Materials for Trapping Elastic Strain Energy Journal Article
In: Advanced Materials, vol. 27, pp. 4296–4301, 2015, ISSN: 1521-4095, (SS, SHK, JRR: equal contribution).
Links | BibTeX | Tags: 3D printing, architected materials, energy trapping, mechanics of soft materials and structures, multistability, reversibility
@article{ADMA:ADMA201501708,
title = {Multistable Architected Materials for Trapping Elastic Strain Energy},
author = {Sicong Shan and Sung H. Kang and Jordan R. Raney and Pai Wang and Lichen Fang and Francisco Candido and Jennifer A. Lewis and Katia Bertoldi},
url = {http://dx.doi.org/10.1002/adma.201501708},
issn = {1521-4095},
year = {2015},
date = {2015-06-18},
journal = {Advanced Materials},
volume = {27},
pages = {4296–4301},
note = {SS, SHK, JRR: equal contribution},
keywords = {3D printing, architected materials, energy trapping, mechanics of soft materials and structures, multistability, reversibility},
pubstate = {published},
tppubtype = {article}
}
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.
Wang, Pai; Casadei, Filippo; Kang, Sung Hoon; Bertoldi, Katia
Locally resonant band gaps in periodic beam lattices by tuning connectivity Journal Article
In: Physical Review B (Rapid Communications), vol. 91, pp. 020103, 2015.
Abstract | Links | BibTeX | Tags: architected materials, Band gap, Beam, Connectivity, Lattice, Local resonance, Periodic
@article{Wang2015,
title = {Locally resonant band gaps in periodic beam lattices by tuning connectivity},
author = {Pai Wang and Filippo Casadei and Sung Hoon Kang and Katia Bertoldi},
url = {http://journals.aps.org/prb/pdf/10.1103/PhysRevB.91.020103},
year = {2015},
date = {2015-01-26},
journal = {Physical Review B (Rapid Communications)},
volume = {91},
pages = {020103},
abstract = {Lattice structures have long fascinated physicists and engineers not only because of their outstanding functionalities, but also for their ability to control the propagation of elastic waves. While the study of the relation between the connectivity of these systems and their static properties has a long history that goes back to Maxwell, rules that connect the dynamic response to the network topology have not been established. Here, we demonstrate that by tuning the average connectivity of a beam network (z ̄), locally resonant band gaps can be generated in the structures without embedding additional resonating units. In particular, a critical threshold for z ̄ is identified, far from which the band gap size is purely dictated by the global lattice topology. By contrast, near this critical value, the detailed local geometry of the lattice also has strong effects. Moreover, in stark contrast to the static case, we find that the nature of the joints is irrelevant to the dynamic response of the lattices. Our results not only shed new light on the rich dynamic properties of periodic lattices, but also outline a new strategy to manipulate mechanical waves in elastic systems.},
keywords = {architected materials, Band gap, Beam, Connectivity, Lattice, Local resonance, Periodic},
pubstate = {published},
tppubtype = {article}
}
Lattice structures have long fascinated physicists and engineers not only because of their outstanding functionalities, but also for their ability to control the propagation of elastic waves. While the study of the relation between the connectivity of these systems and their static properties has a long history that goes back to Maxwell, rules that connect the dynamic response to the network topology have not been established. Here, we demonstrate that by tuning the average connectivity of a beam network (z ̄), locally resonant band gaps can be generated in the structures without embedding additional resonating units. In particular, a critical threshold for z ̄ is identified, far from which the band gap size is purely dictated by the global lattice topology. By contrast, near this critical value, the detailed local geometry of the lattice also has strong effects. Moreover, in stark contrast to the static case, we find that the nature of the joints is irrelevant to the dynamic response of the lattices. Our results not only shed new light on the rich dynamic properties of periodic lattices, but also outline a new strategy to manipulate mechanical waves in elastic systems.
2014
Shan, Sicong; Kang, Sung Hoon; Wang, Pai; Qu, Cangyu; Shian, Samuel; Chen, Elizabeth R.; Weaver, James C.; Bertoldi, Katia
Harnessing Multiple Folding Mechanisms in Soft Periodic and Porous Structures to Design Highly Tunable Phononic Crystals Journal Article
In: Advanced Functional Materials, vol. 24, pp. 4935–4942, 2014.
Abstract | Links | BibTeX | Tags: 3D printing, architected materials, Folding Mechanismsm, mechanics of soft materials and structures, Metamaterial, Phononic Crystals, Soft Periodic Porous Structures, Tunability
@article{Shan2014,
title = {Harnessing Multiple Folding Mechanisms in Soft Periodic and Porous Structures to Design Highly Tunable Phononic Crystals},
author = {Sicong Shan and Sung Hoon Kang and Pai Wang and Cangyu Qu and Samuel Shian and Elizabeth R. Chen and James C. Weaver and Katia Bertoldi},
url = {http://onlinelibrary.wiley.com/doi/10.1002/adfm.201400665/abstract},
year = {2014},
date = {2014-08-20},
journal = {Advanced Functional Materials},
volume = {24},
pages = {4935–4942},
abstract = {Mechanical instabilities in periodic porous elastic structures may lead to the formation of homogeneous patterns, opening avenues for a wide range of applications that are related to the geometry of the system. This study focuses on an elastomeric porous structure comprising a triangular array of circular holes, and shows that by controlling the loading direction, multiple pattern transformations can be induced by buckling. Interestingly, these different pattern transformations can be exploited to design materials with highly tunable properties. In particular, these results indicate that they can be effectively used to tune the propagation of elastic waves in phononic crystals, enhancing the tunability of the dynamic response of the system. Using a combination of finite element simulations and experiments, a proof-of-concept of the novel material is demonstrated. Since the proposed mechanism is induced by elastic instability, it is reversible, repeatable, and scale-independent, opening avenues for the design of highly tunable materials and devices over a wide range of length scales.},
keywords = {3D printing, architected materials, Folding Mechanismsm, mechanics of soft materials and structures, Metamaterial, Phononic Crystals, Soft Periodic Porous Structures, Tunability},
pubstate = {published},
tppubtype = {article}
}
Mechanical instabilities in periodic porous elastic structures may lead to the formation of homogeneous patterns, opening avenues for a wide range of applications that are related to the geometry of the system. This study focuses on an elastomeric porous structure comprising a triangular array of circular holes, and shows that by controlling the loading direction, multiple pattern transformations can be induced by buckling. Interestingly, these different pattern transformations can be exploited to design materials with highly tunable properties. In particular, these results indicate that they can be effectively used to tune the propagation of elastic waves in phononic crystals, enhancing the tunability of the dynamic response of the system. Using a combination of finite element simulations and experiments, a proof-of-concept of the novel material is demonstrated. Since the proposed mechanism is induced by elastic instability, it is reversible, repeatable, and scale-independent, opening avenues for the design of highly tunable materials and devices over a wide range of length scales.
Kang, Sung Hoon; Bertoldi, Katia; Shan, Sicong
Shape Recoverable Reusable Energy Absorbing Structures, Systems and Methods for Manufacture Thereof Technical Report
2014, (United States Provisional Patent Application No. 61/983,782).
BibTeX | Tags: 3D printing, architected materials, Energy-Absorption, Materials, Reversible, Structures
@techreport{Kang2014b,
title = {Shape Recoverable Reusable Energy Absorbing Structures, Systems and Methods for Manufacture Thereof},
author = {Sung Hoon Kang and Katia Bertoldi and Sicong Shan},
year = {2014},
date = {2014-04-24},
booktitle = {U.S. Provisional Patent Application No. 61/983,782},
note = {United States Provisional Patent Application No. 61/983,782},
keywords = {3D printing, architected materials, Energy-Absorption, Materials, Reversible, Structures},
pubstate = {published},
tppubtype = {techreport}
}
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.