Publications
1.
Orrego, Santiago; Chen, Zhezhi; Krekora, Urszula; Hou, Decheng; Jeon, Seung‐Yeol; Pittman, Matthew; Montoya, Carolina; Chen, Yun; Kang, Sung Hoon
Bioinspired Materials with Self‐Adaptable Mechanical Properties Journal Article
In: Advanced Materials, 2020.
@article{Orrego2020,
title = {Bioinspired Materials with Self‐Adaptable Mechanical Properties},
author = {Santiago Orrego and Zhezhi Chen and Urszula Krekora and Decheng Hou and Seung‐Yeol Jeon and Matthew Pittman and Carolina Montoya and Yun Chen and Sung Hoon Kang},
url = {https://onlinelibrary.wiley.com/doi/full/10.1002/adma.201906970},
doi = {https://doi.org/10.1002/adma.201906970},
year = {2020},
date = {2020-04-17},
journal = {Advanced Materials},
abstract = {Natural structural materials, such as bone, can autonomously modulate their mechanical properties in response to external loading to prevent failure. These material systems smartly control the addition/removal of material in locations of high/low mechanical stress by utilizing local resources guided by biological signals. On the contrary, synthetic structural materials have unchanging mechanical properties limiting their mechanical performance and service life. Inspired by the mineralization process of bone, a material system that adapts its mechanical properties in response to external mechanical loading is reported. It is found that charges from piezoelectric scaffolds can induce mineralization from surrounding media. It is shown that the material system can adapt to external mechanical loading by inducing mineral deposition in proportion to the magnitude of the stress and the resulting piezoelectric charges. Moreover, the mineralization mechanism allows a simple one‐step route for fabricating functionally graded materials by controlling the stress distribution along the scaffold. The findings can pave the way for a new class of self‐regenerating materials that reinforce regions of high stress or induce deposition of minerals on the damaged areas from the increase in mechanical stress to prevent/mitigate failure. It is envisioned that the findings can contribute to addressing the current challenges of synthetic materials for load‐bearing applications from self‐adaptive capabilities.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Natural structural materials, such as bone, can autonomously modulate their mechanical properties in response to external loading to prevent failure. These material systems smartly control the addition/removal of material in locations of high/low mechanical stress by utilizing local resources guided by biological signals. On the contrary, synthetic structural materials have unchanging mechanical properties limiting their mechanical performance and service life. Inspired by the mineralization process of bone, a material system that adapts its mechanical properties in response to external mechanical loading is reported. It is found that charges from piezoelectric scaffolds can induce mineralization from surrounding media. It is shown that the material system can adapt to external mechanical loading by inducing mineral deposition in proportion to the magnitude of the stress and the resulting piezoelectric charges. Moreover, the mineralization mechanism allows a simple one‐step route for fabricating functionally graded materials by controlling the stress distribution along the scaffold. The findings can pave the way for a new class of self‐regenerating materials that reinforce regions of high stress or induce deposition of minerals on the damaged areas from the increase in mechanical stress to prevent/mitigate failure. It is envisioned that the findings can contribute to addressing the current challenges of synthetic materials for load‐bearing applications from self‐adaptive capabilities.
2.
Li, Jing; Zhu, Zhiren; Fang, Lichen; Guo, Shu; Erturun, Ugur; Zhu, Zeyu; West, James E; Ghosh, Somnath; Kang, Sung Hoon
Analytical, numerical, and experimental studies of viscoelastic effects on the performance of soft piezoelectric nanocomposites Journal Article
In: Nanoscale, vol. 9, pp. 14215-14228, 2017.
@article{C7NR05163H,
title = {Analytical, numerical, and experimental studies of viscoelastic effects on the performance of soft piezoelectric nanocomposites},
author = {Jing Li and Zhiren Zhu and Lichen Fang and Shu Guo and Ugur Erturun and Zeyu Zhu and James E West and Somnath Ghosh and Sung Hoon Kang},
url = {http://dx.doi.org/10.1039/C7NR05163H},
doi = {10.1039/C7NR05163H},
year = {2017},
date = {2017-09-15},
journal = {Nanoscale},
volume = {9},
pages = {14215-14228},
publisher = {The Royal Society of Chemistry},
abstract = {Piezoelectric composite (p-NC) made of a polymeric matrix and piezoelectric nanoparticles with conductive additives is an attractive material for many applications. As the matrix of p-NC is made of viscoelastic materials, both elastic and viscous characteristics of the matrix are expected to contribute to the piezoelectric response of p-NC. However, there is limited understanding of how viscoelasticity influences the piezoelectric performance of p-NC. Here we combined analytical and numerical analyses with experimental studies to investigate effects of viscoelasticity on piezoelectric performance of p-NC. The viscoelastic properties of synthesized p-NCs were controlled by changing the ratio between monomer and cross-linker of the polymer matrix. We found good agreement between our analytical models and experimental results for both quasi-static and dynamic loadings. It is found that, under quasi-static loading conditions, the piezoelectric coefficients (d33) of the specimen with the lowest Young's modulus ([similar]0.45 MPa at 5% strain) were [similar]120 pC N-1, while the one with the highest Young's modulus ([similar]1.3 MPa at 5% strain) were [similar]62 pC N-1. The results suggest that softer matrices enhance the energy harvesting performance because they can result in larger deformation for a given load. Moreover, from our theoretical analysis and experiments under dynamic loading conditions, we found the viscous modulus of a matrix is also important for piezoelectric performance. For instance, at 40 Hz and 50 Hz the storage moduli of the softest specimen were [similar]0.625 MPa and [similar]0.485 MPa, while the loss moduli were [similar]0.108 MPa and [similar]0.151 MPa, respectively. As piezocomposites with less viscous loss can transfer mechanical energy to piezoelectric particles more efficiently, the dynamic piezoelectric coefficient (d[prime or minute]33) measured at 40 Hz ([similar]53 pC N-1) was larger than that at 50 Hz ([similar]47 pC N-1) though it has a larger storage modulus. As an application of our findings, we fabricated 3D piezo-shells with different viscoelastic properties and compared the charging time. The results showed a good agreement with the predicted trend that the composition with the smallest elastic and viscous moduli showed the fastest charging rate. Our findings can open new opportunities for optimizing the performance of polymer-based multifunctional materials by harnessing viscoelasticity.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Piezoelectric composite (p-NC) made of a polymeric matrix and piezoelectric nanoparticles with conductive additives is an attractive material for many applications. As the matrix of p-NC is made of viscoelastic materials, both elastic and viscous characteristics of the matrix are expected to contribute to the piezoelectric response of p-NC. However, there is limited understanding of how viscoelasticity influences the piezoelectric performance of p-NC. Here we combined analytical and numerical analyses with experimental studies to investigate effects of viscoelasticity on piezoelectric performance of p-NC. The viscoelastic properties of synthesized p-NCs were controlled by changing the ratio between monomer and cross-linker of the polymer matrix. We found good agreement between our analytical models and experimental results for both quasi-static and dynamic loadings. It is found that, under quasi-static loading conditions, the piezoelectric coefficients (d33) of the specimen with the lowest Young’s modulus ([similar]0.45 MPa at 5% strain) were [similar]120 pC N-1, while the one with the highest Young’s modulus ([similar]1.3 MPa at 5% strain) were [similar]62 pC N-1. The results suggest that softer matrices enhance the energy harvesting performance because they can result in larger deformation for a given load. Moreover, from our theoretical analysis and experiments under dynamic loading conditions, we found the viscous modulus of a matrix is also important for piezoelectric performance. For instance, at 40 Hz and 50 Hz the storage moduli of the softest specimen were [similar]0.625 MPa and [similar]0.485 MPa, while the loss moduli were [similar]0.108 MPa and [similar]0.151 MPa, respectively. As piezocomposites with less viscous loss can transfer mechanical energy to piezoelectric particles more efficiently, the dynamic piezoelectric coefficient (d[prime or minute]33) measured at 40 Hz ([similar]53 pC N-1) was larger than that at 50 Hz ([similar]47 pC N-1) though it has a larger storage modulus. As an application of our findings, we fabricated 3D piezo-shells with different viscoelastic properties and compared the charging time. The results showed a good agreement with the predicted trend that the composition with the smallest elastic and viscous moduli showed the fastest charging rate. Our findings can open new opportunities for optimizing the performance of polymer-based multifunctional materials by harnessing viscoelasticity.
3.
Chen, Shuyang; Li, Jing; Fang, Lichen; Zhu, Zeyu; Kang, Sung Hoon
Simple Triple-State Polymer Actuators with Controllable Folding Characteristics Journal Article
In: Applied Physics Letters, vol. 110, pp. 133506, 2017.
@article{Chen2017,
title = {Simple Triple-State Polymer Actuators with Controllable Folding Characteristics},
author = {Shuyang Chen and Jing Li and Lichen Fang and Zeyu Zhu and Sung Hoon Kang},
url = {http://aip.scitation.org/doi/pdf/10.1063/1.4979560},
doi = {10.1063/1.4979560},
year = {2017},
date = {2017-03-30},
journal = {Applied Physics Letters},
volume = {110},
pages = {133506},
abstract = {Driven by the interests in self-folding, there have been studies developing artificial self-folding structures at different length scales based on various polymer actuators that can realize dual-state actuation. However, their unidirectional nature limits the applicability of the actuators for a wide range of multi-state self-folding behaviors. In addition, complex fabrication and programming procedures hinder broad applications of existing polymer actuators. Moreover, few of the exiting polymer actuators are able to show the self-folding behaviors with precise control of curvature and force. To address these issues, we report an easy-to-fabricate triple-state actuator with controllable folding behaviors based on bilayer polymer composites with different glass transition temperatures. Initially, the fabricated actuator is in flat state, and it can sequentially self-fold to angled folding states of opposite directions as it is heated up. Based on an analytical model and measured partial recovery behaviors of polymers, we can accurately control the folding characteristics (curvature and force) for rational design. To demonstrate an application of our triple-state actuator, we have developed a self-folding transformer robot which self-folds from a two-dimensional sheet into a three-dimensional boat-like configuration and transforms from the boat shape to a car shape with the increase of the temperature applied to the actuator. Our findings offer a simple approach to generate multiple configurations from a single system by harnessing behaviors of polymers with rational design.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Driven by the interests in self-folding, there have been studies developing artificial self-folding structures at different length scales based on various polymer actuators that can realize dual-state actuation. However, their unidirectional nature limits the applicability of the actuators for a wide range of multi-state self-folding behaviors. In addition, complex fabrication and programming procedures hinder broad applications of existing polymer actuators. Moreover, few of the exiting polymer actuators are able to show the self-folding behaviors with precise control of curvature and force. To address these issues, we report an easy-to-fabricate triple-state actuator with controllable folding behaviors based on bilayer polymer composites with different glass transition temperatures. Initially, the fabricated actuator is in flat state, and it can sequentially self-fold to angled folding states of opposite directions as it is heated up. Based on an analytical model and measured partial recovery behaviors of polymers, we can accurately control the folding characteristics (curvature and force) for rational design. To demonstrate an application of our triple-state actuator, we have developed a self-folding transformer robot which self-folds from a two-dimensional sheet into a three-dimensional boat-like configuration and transforms from the boat shape to a car shape with the increase of the temperature applied to the actuator. Our findings offer a simple approach to generate multiple configurations from a single system by harnessing behaviors of polymers with rational design.
4.
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.
5.
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}
}
6.
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.
7.
Kang, Sung Hoon; Shan, Sicong; Košmrlj, Andrej; Noorduin, Wim L.; Shian, Samuel; Weaver, James C.; Clarke, David R.; Bertoldi, Katia
Complex Ordered Patterns in Mechanical Instability Induced Geometrically Frustrated Triangular Cellular Structures Journal Article
In: Physical Review Letters, vol. 112, pp. 098701, 2014, (Selected as Physical Review Letters Editors’ Suggestion and Highlighted in Physics Synopsis.).
@article{Kang2014,
title = {Complex Ordered Patterns in Mechanical Instability Induced Geometrically Frustrated Triangular Cellular Structures},
author = {Sung Hoon Kang and Sicong Shan and Andrej Košmrlj and Wim L. Noorduin and Samuel Shian and James C. Weaver and David R. Clarke and Katia Bertoldi},
url = {http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.112.098701},
year = {2014},
date = {2014-03-05},
journal = {Physical Review Letters},
volume = {112},
pages = {098701},
abstract = {Geometrical frustration arises when a local order cannot propagate throughout the space because of geometrical constraints. This phenomenon plays a major role in many systems leading to disordered ground-state configurations. Here, we report a theoretical and experimental study on the behavior of buckling-induced geometrically frustrated triangular cellular structures. To our surprise, we find that buckling induces complex ordered patterns which can be tuned by controlling the porosity of the structures. Our analysis reveals that the connected geometry of the cellular structure plays a crucial role in the generation of ordered states in this frustrated system.},
note = {Selected as Physical Review Letters Editors’ Suggestion and Highlighted in Physics Synopsis.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Geometrical frustration arises when a local order cannot propagate throughout the space because of geometrical constraints. This phenomenon plays a major role in many systems leading to disordered ground-state configurations. Here, we report a theoretical and experimental study on the behavior of buckling-induced geometrically frustrated triangular cellular structures. To our surprise, we find that buckling induces complex ordered patterns which can be tuned by controlling the porosity of the structures. Our analysis reveals that the connected geometry of the cellular structure plays a crucial role in the generation of ordered states in this frustrated system.
8.
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.
9.
Kang, Sung Hoon; Shan, Sicong; Noorduin, Wim L.; Khan, Mughees; Aizenberg, Joanna; Bertoldi, Katia
Buckling-Induced Reversible Symmetry Breaking and Chiral Amplification Using Supported Cellular Structures Journal Article
In: Advanced Materials, vol. 25, pp. 3380-3385, 2013, (SHK, SS, and WLN contributed equally. Highlighted in the June 2013 issue of Nature Physics).
@article{Kang2013,
title = {Buckling-Induced Reversible Symmetry Breaking and Chiral Amplification Using Supported Cellular Structures},
author = {Sung Hoon Kang and Sicong Shan and Wim L. Noorduin and Mughees Khan and Joanna Aizenberg and Katia Bertoldi},
url = {http://onlinelibrary.wiley.com/doi/10.1002/adma.201300617/abstract},
year = {2013},
date = {2013-05-02},
journal = {Advanced Materials},
volume = {25},
pages = {3380-3385},
abstract = {Buckling-induced reversible symmetry breaking and amplification of chirality using macro- and microscale supported cellular structures is described. Guided by extensive theoretical analysis, cellular structures are rationally designed, in which buckling induces a reversible switching between achiral and chiral configurations. Additionally, it is demonstrated that the proposed mechanism can be generalized over a wide range of length scales, geometries, materials, and stimuli. },
note = {SHK, SS, and WLN contributed equally.
Highlighted in the June 2013 issue of Nature Physics},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Buckling-induced reversible symmetry breaking and amplification of chirality using macro- and microscale supported cellular structures is described. Guided by extensive theoretical analysis, cellular structures are rationally designed, in which buckling induces a reversible switching between achiral and chiral configurations. Additionally, it is demonstrated that the proposed mechanism can be generalized over a wide range of length scales, geometries, materials, and stimuli.
Note: Send e-mail to Prof. Kang at [email protected] if you need a pdf file of the papers below.
2020
Orrego, Santiago; Chen, Zhezhi; Krekora, Urszula; Hou, Decheng; Jeon, Seung‐Yeol; Pittman, Matthew; Montoya, Carolina; Chen, Yun; Kang, Sung Hoon
Bioinspired Materials with Self‐Adaptable Mechanical Properties Journal Article
In: Advanced Materials, 2020.
Abstract | Links | BibTeX | Tags: adaptive, Bio-Inspired, bio-inspired science and engineering, biomaterial, mechanics of soft materials and structures, mineral, multifunctional material, piezoelectric, porous structure, regeneration
@article{Orrego2020,
title = {Bioinspired Materials with Self‐Adaptable Mechanical Properties},
author = {Santiago Orrego and Zhezhi Chen and Urszula Krekora and Decheng Hou and Seung‐Yeol Jeon and Matthew Pittman and Carolina Montoya and Yun Chen and Sung Hoon Kang},
url = {https://onlinelibrary.wiley.com/doi/full/10.1002/adma.201906970},
doi = {https://doi.org/10.1002/adma.201906970},
year = {2020},
date = {2020-04-17},
journal = {Advanced Materials},
abstract = {Natural structural materials, such as bone, can autonomously modulate their mechanical properties in response to external loading to prevent failure. These material systems smartly control the addition/removal of material in locations of high/low mechanical stress by utilizing local resources guided by biological signals. On the contrary, synthetic structural materials have unchanging mechanical properties limiting their mechanical performance and service life. Inspired by the mineralization process of bone, a material system that adapts its mechanical properties in response to external mechanical loading is reported. It is found that charges from piezoelectric scaffolds can induce mineralization from surrounding media. It is shown that the material system can adapt to external mechanical loading by inducing mineral deposition in proportion to the magnitude of the stress and the resulting piezoelectric charges. Moreover, the mineralization mechanism allows a simple one‐step route for fabricating functionally graded materials by controlling the stress distribution along the scaffold. The findings can pave the way for a new class of self‐regenerating materials that reinforce regions of high stress or induce deposition of minerals on the damaged areas from the increase in mechanical stress to prevent/mitigate failure. It is envisioned that the findings can contribute to addressing the current challenges of synthetic materials for load‐bearing applications from self‐adaptive capabilities.},
keywords = {adaptive, Bio-Inspired, bio-inspired science and engineering, biomaterial, mechanics of soft materials and structures, mineral, multifunctional material, piezoelectric, porous structure, regeneration},
pubstate = {published},
tppubtype = {article}
}
Natural structural materials, such as bone, can autonomously modulate their mechanical properties in response to external loading to prevent failure. These material systems smartly control the addition/removal of material in locations of high/low mechanical stress by utilizing local resources guided by biological signals. On the contrary, synthetic structural materials have unchanging mechanical properties limiting their mechanical performance and service life. Inspired by the mineralization process of bone, a material system that adapts its mechanical properties in response to external mechanical loading is reported. It is found that charges from piezoelectric scaffolds can induce mineralization from surrounding media. It is shown that the material system can adapt to external mechanical loading by inducing mineral deposition in proportion to the magnitude of the stress and the resulting piezoelectric charges. Moreover, the mineralization mechanism allows a simple one‐step route for fabricating functionally graded materials by controlling the stress distribution along the scaffold. The findings can pave the way for a new class of self‐regenerating materials that reinforce regions of high stress or induce deposition of minerals on the damaged areas from the increase in mechanical stress to prevent/mitigate failure. It is envisioned that the findings can contribute to addressing the current challenges of synthetic materials for load‐bearing applications from self‐adaptive capabilities.
2017
Li, Jing; Zhu, Zhiren; Fang, Lichen; Guo, Shu; Erturun, Ugur; Zhu, Zeyu; West, James E; Ghosh, Somnath; Kang, Sung Hoon
Analytical, numerical, and experimental studies of viscoelastic effects on the performance of soft piezoelectric nanocomposites Journal Article
In: Nanoscale, vol. 9, pp. 14215-14228, 2017.
Abstract | Links | BibTeX | Tags: analytical, composite, energy harvesting, experimental, mechanics of soft materials and structures, numerical, piezoelectric, sensing, viscoelasticity
@article{C7NR05163H,
title = {Analytical, numerical, and experimental studies of viscoelastic effects on the performance of soft piezoelectric nanocomposites},
author = {Jing Li and Zhiren Zhu and Lichen Fang and Shu Guo and Ugur Erturun and Zeyu Zhu and James E West and Somnath Ghosh and Sung Hoon Kang},
url = {http://dx.doi.org/10.1039/C7NR05163H},
doi = {10.1039/C7NR05163H},
year = {2017},
date = {2017-09-15},
journal = {Nanoscale},
volume = {9},
pages = {14215-14228},
publisher = {The Royal Society of Chemistry},
abstract = {Piezoelectric composite (p-NC) made of a polymeric matrix and piezoelectric nanoparticles with conductive additives is an attractive material for many applications. As the matrix of p-NC is made of viscoelastic materials, both elastic and viscous characteristics of the matrix are expected to contribute to the piezoelectric response of p-NC. However, there is limited understanding of how viscoelasticity influences the piezoelectric performance of p-NC. Here we combined analytical and numerical analyses with experimental studies to investigate effects of viscoelasticity on piezoelectric performance of p-NC. The viscoelastic properties of synthesized p-NCs were controlled by changing the ratio between monomer and cross-linker of the polymer matrix. We found good agreement between our analytical models and experimental results for both quasi-static and dynamic loadings. It is found that, under quasi-static loading conditions, the piezoelectric coefficients (d33) of the specimen with the lowest Young's modulus ([similar]0.45 MPa at 5% strain) were [similar]120 pC N-1, while the one with the highest Young's modulus ([similar]1.3 MPa at 5% strain) were [similar]62 pC N-1. The results suggest that softer matrices enhance the energy harvesting performance because they can result in larger deformation for a given load. Moreover, from our theoretical analysis and experiments under dynamic loading conditions, we found the viscous modulus of a matrix is also important for piezoelectric performance. For instance, at 40 Hz and 50 Hz the storage moduli of the softest specimen were [similar]0.625 MPa and [similar]0.485 MPa, while the loss moduli were [similar]0.108 MPa and [similar]0.151 MPa, respectively. As piezocomposites with less viscous loss can transfer mechanical energy to piezoelectric particles more efficiently, the dynamic piezoelectric coefficient (d[prime or minute]33) measured at 40 Hz ([similar]53 pC N-1) was larger than that at 50 Hz ([similar]47 pC N-1) though it has a larger storage modulus. As an application of our findings, we fabricated 3D piezo-shells with different viscoelastic properties and compared the charging time. The results showed a good agreement with the predicted trend that the composition with the smallest elastic and viscous moduli showed the fastest charging rate. Our findings can open new opportunities for optimizing the performance of polymer-based multifunctional materials by harnessing viscoelasticity.},
keywords = {analytical, composite, energy harvesting, experimental, mechanics of soft materials and structures, numerical, piezoelectric, sensing, viscoelasticity},
pubstate = {published},
tppubtype = {article}
}
Piezoelectric composite (p-NC) made of a polymeric matrix and piezoelectric nanoparticles with conductive additives is an attractive material for many applications. As the matrix of p-NC is made of viscoelastic materials, both elastic and viscous characteristics of the matrix are expected to contribute to the piezoelectric response of p-NC. However, there is limited understanding of how viscoelasticity influences the piezoelectric performance of p-NC. Here we combined analytical and numerical analyses with experimental studies to investigate effects of viscoelasticity on piezoelectric performance of p-NC. The viscoelastic properties of synthesized p-NCs were controlled by changing the ratio between monomer and cross-linker of the polymer matrix. We found good agreement between our analytical models and experimental results for both quasi-static and dynamic loadings. It is found that, under quasi-static loading conditions, the piezoelectric coefficients (d33) of the specimen with the lowest Young’s modulus ([similar]0.45 MPa at 5% strain) were [similar]120 pC N-1, while the one with the highest Young’s modulus ([similar]1.3 MPa at 5% strain) were [similar]62 pC N-1. The results suggest that softer matrices enhance the energy harvesting performance because they can result in larger deformation for a given load. Moreover, from our theoretical analysis and experiments under dynamic loading conditions, we found the viscous modulus of a matrix is also important for piezoelectric performance. For instance, at 40 Hz and 50 Hz the storage moduli of the softest specimen were [similar]0.625 MPa and [similar]0.485 MPa, while the loss moduli were [similar]0.108 MPa and [similar]0.151 MPa, respectively. As piezocomposites with less viscous loss can transfer mechanical energy to piezoelectric particles more efficiently, the dynamic piezoelectric coefficient (d[prime or minute]33) measured at 40 Hz ([similar]53 pC N-1) was larger than that at 50 Hz ([similar]47 pC N-1) though it has a larger storage modulus. As an application of our findings, we fabricated 3D piezo-shells with different viscoelastic properties and compared the charging time. The results showed a good agreement with the predicted trend that the composition with the smallest elastic and viscous moduli showed the fastest charging rate. Our findings can open new opportunities for optimizing the performance of polymer-based multifunctional materials by harnessing viscoelasticity.
Chen, Shuyang; Li, Jing; Fang, Lichen; Zhu, Zeyu; Kang, Sung Hoon
Simple Triple-State Polymer Actuators with Controllable Folding Characteristics Journal Article
In: Applied Physics Letters, vol. 110, pp. 133506, 2017.
Abstract | Links | BibTeX | Tags: Bio-Inspired, mechanics of soft materials and structures, polymer, programmable material, Self-Folding, transformer
@article{Chen2017,
title = {Simple Triple-State Polymer Actuators with Controllable Folding Characteristics},
author = {Shuyang Chen and Jing Li and Lichen Fang and Zeyu Zhu and Sung Hoon Kang},
url = {http://aip.scitation.org/doi/pdf/10.1063/1.4979560},
doi = {10.1063/1.4979560},
year = {2017},
date = {2017-03-30},
journal = {Applied Physics Letters},
volume = {110},
pages = {133506},
abstract = {Driven by the interests in self-folding, there have been studies developing artificial self-folding structures at different length scales based on various polymer actuators that can realize dual-state actuation. However, their unidirectional nature limits the applicability of the actuators for a wide range of multi-state self-folding behaviors. In addition, complex fabrication and programming procedures hinder broad applications of existing polymer actuators. Moreover, few of the exiting polymer actuators are able to show the self-folding behaviors with precise control of curvature and force. To address these issues, we report an easy-to-fabricate triple-state actuator with controllable folding behaviors based on bilayer polymer composites with different glass transition temperatures. Initially, the fabricated actuator is in flat state, and it can sequentially self-fold to angled folding states of opposite directions as it is heated up. Based on an analytical model and measured partial recovery behaviors of polymers, we can accurately control the folding characteristics (curvature and force) for rational design. To demonstrate an application of our triple-state actuator, we have developed a self-folding transformer robot which self-folds from a two-dimensional sheet into a three-dimensional boat-like configuration and transforms from the boat shape to a car shape with the increase of the temperature applied to the actuator. Our findings offer a simple approach to generate multiple configurations from a single system by harnessing behaviors of polymers with rational design.},
keywords = {Bio-Inspired, mechanics of soft materials and structures, polymer, programmable material, Self-Folding, transformer},
pubstate = {published},
tppubtype = {article}
}
Driven by the interests in self-folding, there have been studies developing artificial self-folding structures at different length scales based on various polymer actuators that can realize dual-state actuation. However, their unidirectional nature limits the applicability of the actuators for a wide range of multi-state self-folding behaviors. In addition, complex fabrication and programming procedures hinder broad applications of existing polymer actuators. Moreover, few of the exiting polymer actuators are able to show the self-folding behaviors with precise control of curvature and force. To address these issues, we report an easy-to-fabricate triple-state actuator with controllable folding behaviors based on bilayer polymer composites with different glass transition temperatures. Initially, the fabricated actuator is in flat state, and it can sequentially self-fold to angled folding states of opposite directions as it is heated up. Based on an analytical model and measured partial recovery behaviors of polymers, we can accurately control the folding characteristics (curvature and force) for rational design. To demonstrate an application of our triple-state actuator, we have developed a self-folding transformer robot which self-folds from a two-dimensional sheet into a three-dimensional boat-like configuration and transforms from the boat shape to a car shape with the increase of the temperature applied to the actuator. Our findings offer a simple approach to generate multiple configurations from a single system by harnessing behaviors of polymers with rational design.
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}
}
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; Shan, Sicong; Košmrlj, Andrej; Noorduin, Wim L.; Shian, Samuel; Weaver, James C.; Clarke, David R.; Bertoldi, Katia
Complex Ordered Patterns in Mechanical Instability Induced Geometrically Frustrated Triangular Cellular Structures Journal Article
In: Physical Review Letters, vol. 112, pp. 098701, 2014, (Selected as Physical Review Letters Editors’ Suggestion and Highlighted in Physics Synopsis.).
Abstract | Links | BibTeX | Tags: 3D printing, Cellular Structures, Geometrical Frustration, Mechanical Instability, mechanics of soft materials and structures, Triangular Lattice
@article{Kang2014,
title = {Complex Ordered Patterns in Mechanical Instability Induced Geometrically Frustrated Triangular Cellular Structures},
author = {Sung Hoon Kang and Sicong Shan and Andrej Košmrlj and Wim L. Noorduin and Samuel Shian and James C. Weaver and David R. Clarke and Katia Bertoldi},
url = {http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.112.098701},
year = {2014},
date = {2014-03-05},
journal = {Physical Review Letters},
volume = {112},
pages = {098701},
abstract = {Geometrical frustration arises when a local order cannot propagate throughout the space because of geometrical constraints. This phenomenon plays a major role in many systems leading to disordered ground-state configurations. Here, we report a theoretical and experimental study on the behavior of buckling-induced geometrically frustrated triangular cellular structures. To our surprise, we find that buckling induces complex ordered patterns which can be tuned by controlling the porosity of the structures. Our analysis reveals that the connected geometry of the cellular structure plays a crucial role in the generation of ordered states in this frustrated system.},
note = {Selected as Physical Review Letters Editors’ Suggestion and Highlighted in Physics Synopsis.},
keywords = {3D printing, Cellular Structures, Geometrical Frustration, Mechanical Instability, mechanics of soft materials and structures, Triangular Lattice},
pubstate = {published},
tppubtype = {article}
}
Geometrical frustration arises when a local order cannot propagate throughout the space because of geometrical constraints. This phenomenon plays a major role in many systems leading to disordered ground-state configurations. Here, we report a theoretical and experimental study on the behavior of buckling-induced geometrically frustrated triangular cellular structures. To our surprise, we find that buckling induces complex ordered patterns which can be tuned by controlling the porosity of the structures. Our analysis reveals that the connected geometry of the cellular structure plays a crucial role in the generation of ordered states in this frustrated system.
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.
Kang, Sung Hoon; Shan, Sicong; Noorduin, Wim L.; Khan, Mughees; Aizenberg, Joanna; Bertoldi, Katia
Buckling-Induced Reversible Symmetry Breaking and Chiral Amplification Using Supported Cellular Structures Journal Article
In: Advanced Materials, vol. 25, pp. 3380-3385, 2013, (SHK, SS, and WLN contributed equally. Highlighted in the June 2013 issue of Nature Physics).
Abstract | Links | BibTeX | Tags: 3D printing, Amplification, Cellular Structures, Mechanical Instability, mechanics of soft materials and structures, Reversible, Symmetry Breaking
@article{Kang2013,
title = {Buckling-Induced Reversible Symmetry Breaking and Chiral Amplification Using Supported Cellular Structures},
author = {Sung Hoon Kang and Sicong Shan and Wim L. Noorduin and Mughees Khan and Joanna Aizenberg and Katia Bertoldi},
url = {http://onlinelibrary.wiley.com/doi/10.1002/adma.201300617/abstract},
year = {2013},
date = {2013-05-02},
journal = {Advanced Materials},
volume = {25},
pages = {3380-3385},
abstract = {Buckling-induced reversible symmetry breaking and amplification of chirality using macro- and microscale supported cellular structures is described. Guided by extensive theoretical analysis, cellular structures are rationally designed, in which buckling induces a reversible switching between achiral and chiral configurations. Additionally, it is demonstrated that the proposed mechanism can be generalized over a wide range of length scales, geometries, materials, and stimuli. },
note = {SHK, SS, and WLN contributed equally.
Highlighted in the June 2013 issue of Nature Physics},
keywords = {3D printing, Amplification, Cellular Structures, Mechanical Instability, mechanics of soft materials and structures, Reversible, Symmetry Breaking},
pubstate = {published},
tppubtype = {article}
}
Buckling-induced reversible symmetry breaking and amplification of chirality using macro- and microscale supported cellular structures is described. Guided by extensive theoretical analysis, cellular structures are rationally designed, in which buckling induces a reversible switching between achiral and chiral configurations. Additionally, it is demonstrated that the proposed mechanism can be generalized over a wide range of length scales, geometries, materials, and stimuli.