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.
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.
3.
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.
4.
Orrego, Santiago; Shoele, Kourosh; Ruas, Andre; Doran, Kyle; Caggiano, Brett; Mittal, Rajat; Kang, Sung Hoon
Harvesting ambient wind energy with an inverted piezoelectric flag Journal Article
In: Applied Energy, vol. 194, pp. 212-222, 2017.
@article{Orrego2017,
title = {Harvesting ambient wind energy with an inverted piezoelectric flag},
author = {Santiago Orrego and Kourosh Shoele and Andre Ruas and Kyle Doran and Brett Caggiano and Rajat Mittal and Sung Hoon Kang},
url = {http://www.sciencedirect.com/science/article/pii/S0306261917302350},
doi = {10.1016/j.apenergy.2017.03.016},
year = {2017},
date = {2017-03-19},
journal = {Applied Energy},
volume = {194},
pages = {212-222},
abstract = {The paper describes an experimental study of wind energy harvesting by self-sustained oscillations (flutter) of a flexible piezoelectric membrane fixed in a novel orientation called the “inverted flag”. We conducted parametric studies to evaluate the influence of geometrical parameters of the flag on the flapping behavior and the resulting energy output. We have demonstrated the capability for inducing aero-elastic flutter in a desired wind velocity range by simply tuning the geometrical parameters of the flag. A peak electrical power of ∼5.0 mW/cm3 occurred at a wind velocity of 9 m/s. Our devices showed sustained power generation (∼0.4 mW/cm3) even in low-wind speed regimes (∼3.5 m/s) suitable for ambient wind energy harvesting. We also conducted outdoor experiments and harvested ambient wind energy to power a temperature sensor without employing a battery for energy storage. Moreover, a self-aligning mechanism to compensate for changing wind directions was incorporated and resulted in an increase in the temperature sensor data output by more than 20 times. These findings open new opportunities for self-powered devices using ambient wind energy with fluctuating conditions and low speed regimes.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The paper describes an experimental study of wind energy harvesting by self-sustained oscillations (flutter) of a flexible piezoelectric membrane fixed in a novel orientation called the “inverted flag”. We conducted parametric studies to evaluate the influence of geometrical parameters of the flag on the flapping behavior and the resulting energy output. We have demonstrated the capability for inducing aero-elastic flutter in a desired wind velocity range by simply tuning the geometrical parameters of the flag. A peak electrical power of ∼5.0 mW/cm3 occurred at a wind velocity of 9 m/s. Our devices showed sustained power generation (∼0.4 mW/cm3) even in low-wind speed regimes (∼3.5 m/s) suitable for ambient wind energy harvesting. We also conducted outdoor experiments and harvested ambient wind energy to power a temperature sensor without employing a battery for energy storage. Moreover, a self-aligning mechanism to compensate for changing wind directions was incorporated and resulted in an increase in the temperature sensor data output by more than 20 times. These findings open new opportunities for self-powered devices using ambient wind energy with fluctuating conditions and low speed regimes.
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.
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
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.
Orrego, Santiago; Shoele, Kourosh; Ruas, Andre; Doran, Kyle; Caggiano, Brett; Mittal, Rajat; Kang, Sung Hoon
Harvesting ambient wind energy with an inverted piezoelectric flag Journal Article
In: Applied Energy, vol. 194, pp. 212-222, 2017.
Abstract | Links | BibTeX | Tags: energy harvesting, inverted flag, piezoelectric, renewable energy, self-aligned, wind
@article{Orrego2017,
title = {Harvesting ambient wind energy with an inverted piezoelectric flag},
author = {Santiago Orrego and Kourosh Shoele and Andre Ruas and Kyle Doran and Brett Caggiano and Rajat Mittal and Sung Hoon Kang},
url = {http://www.sciencedirect.com/science/article/pii/S0306261917302350},
doi = {10.1016/j.apenergy.2017.03.016},
year = {2017},
date = {2017-03-19},
journal = {Applied Energy},
volume = {194},
pages = {212-222},
abstract = {The paper describes an experimental study of wind energy harvesting by self-sustained oscillations (flutter) of a flexible piezoelectric membrane fixed in a novel orientation called the “inverted flag”. We conducted parametric studies to evaluate the influence of geometrical parameters of the flag on the flapping behavior and the resulting energy output. We have demonstrated the capability for inducing aero-elastic flutter in a desired wind velocity range by simply tuning the geometrical parameters of the flag. A peak electrical power of ∼5.0 mW/cm3 occurred at a wind velocity of 9 m/s. Our devices showed sustained power generation (∼0.4 mW/cm3) even in low-wind speed regimes (∼3.5 m/s) suitable for ambient wind energy harvesting. We also conducted outdoor experiments and harvested ambient wind energy to power a temperature sensor without employing a battery for energy storage. Moreover, a self-aligning mechanism to compensate for changing wind directions was incorporated and resulted in an increase in the temperature sensor data output by more than 20 times. These findings open new opportunities for self-powered devices using ambient wind energy with fluctuating conditions and low speed regimes.},
keywords = {energy harvesting, inverted flag, piezoelectric, renewable energy, self-aligned, wind},
pubstate = {published},
tppubtype = {article}
}
The paper describes an experimental study of wind energy harvesting by self-sustained oscillations (flutter) of a flexible piezoelectric membrane fixed in a novel orientation called the “inverted flag”. We conducted parametric studies to evaluate the influence of geometrical parameters of the flag on the flapping behavior and the resulting energy output. We have demonstrated the capability for inducing aero-elastic flutter in a desired wind velocity range by simply tuning the geometrical parameters of the flag. A peak electrical power of ∼5.0 mW/cm3 occurred at a wind velocity of 9 m/s. Our devices showed sustained power generation (∼0.4 mW/cm3) even in low-wind speed regimes (∼3.5 m/s) suitable for ambient wind energy harvesting. We also conducted outdoor experiments and harvested ambient wind energy to power a temperature sensor without employing a battery for energy storage. Moreover, a self-aligning mechanism to compensate for changing wind directions was incorporated and resulted in an increase in the temperature sensor data output by more than 20 times. These findings open new opportunities for self-powered devices using ambient wind energy with fluctuating conditions and low speed regimes.