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Article ; Online: Flexible nanomechanical bit based on few-layer graphene.

Zhang, Bin / Xue, Yixuan / Park, Harold S / Jiang, Jin-Wu

Physical chemistry chemical physics : PCCP

2024 Volume 26, Issue 2, Page(s) 822–829

Abstract: Mechanical computers have gained intense research interest at size scales ranging from nano to macro as they may complement electronic computers operating in extreme environments. While nanoscale mechanical computers may be easier to integrate with ... ...

Abstract	Mechanical computers have gained intense research interest at size scales ranging from nano to macro as they may complement electronic computers operating in extreme environments. While nanoscale mechanical computers may be easier to integrate with traditional electronic components, most current nanomechanical computers are based on volatile resonator systems that require continuous energy input. In this study, we propose a non-volatile nanomechanical bit based on the quasi-stable configurations of few-layer graphene with void defects, and demonstrate its multiple quasi-stable states by deriving an analytic relationship for the void configuration based on a competition between the bending energy and the cohesive energy. Using this nanomechanical bit, typical logic gates are constructed to perform Boolean calculations, including NOT, AND, OR, NAND and NOR gates, and demonstrate reprogrammability between these logic gates. We also study the accuracy and the stability of the nanomechanical bits based on the few-layer graphene. These findings provide a novel approach to realize the nanomechanical computing process.
Language	English
Publishing date	2024-01-03
Publishing country	England
Document type	Journal Article
ZDB-ID	1476244-4
ISSN	1463-9084 ; 1463-9076
ISSN (online)	1463-9084
ISSN	1463-9076
DOI	10.1039/d3cp03241h
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article ; Online: Surface Adatom Diffusion-Assisted Dislocation Nucleation in Metal Nanowires.

He, Lijie / Cheng, Guangming / Zhu, Yong / Park, Harold S

Nano letters

2023 Volume 23, Issue 12, Page(s) 5779–5784

Abstract: We employ a hybrid diffusion- and nucleation-based kinetic Monte Carlo model to elucidate the significant impact of adatom diffusion on incipient surface dislocation nucleation in metal nanowires. We reveal a stress-regulated diffusion mechanism that ... ...

Abstract	We employ a hybrid diffusion- and nucleation-based kinetic Monte Carlo model to elucidate the significant impact of adatom diffusion on incipient surface dislocation nucleation in metal nanowires. We reveal a stress-regulated diffusion mechanism that promotes preferential accumulation of diffusing adatoms near nucleation sites, which explains the experimental observations of strong temperature but weak strain-rate dependence as well as temperature-dependent scatter of the nucleation strength. Furthermore, the model demonstrates that a decreasing rate of adatom diffusion with an increasing strain rate will lead to stress-controlled nucleation being the dominant nucleation mechanism at higher strain rates. Overall, our model offers new mechanistic insights into how surface adatom diffusion directly impacts the incipient defect nucleation process and resulting mechanical properties of metal nanowires.
Language	English
Publishing date	2023-06-14
Publishing country	United States
Document type	Journal Article
ISSN	1530-6992
ISSN (online)	1530-6992
DOI	10.1021/acs.nanolett.3c01660
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article ; Online: Elastic Instabilities Govern the Morphogenesis of the Optic Cup.

Lee, Jeong-Ho / Park, Harold S / Holmes, Douglas P

Physical review letters

2021 Volume 127, Issue 13, Page(s) 138102

Abstract: Because the normal operation of the eye depends on sensitive morphogenetic processes for its eventual shape, developmental flaws can lead to wide-ranging ocular defects. However, the physical processes and mechanisms governing ocular morphogenesis are ... ...

Abstract	Because the normal operation of the eye depends on sensitive morphogenetic processes for its eventual shape, developmental flaws can lead to wide-ranging ocular defects. However, the physical processes and mechanisms governing ocular morphogenesis are not well understood. Here, using analytical theory and nonlinear shell finite-element simulations, we show, for optic vesicles experiencing matrix-constrained growth, that elastic instabilities govern the optic cup morphogenesis. By capturing the stress amplification owing to mass increase during growth, we show that the morphogenesis is driven by two elastic instabilities analogous to the snap through in spherical shells, where the second instability is sensitive to the optic cup geometry. In particular, if the optic vesicle is too slender, it will buckle and break axisymmetry, thus, preventing normal development. Our results shed light on the morphogenetic mechanisms governing the formation of a functional biological system and the role of elastic instabilities in the shape selection of soft biological structures.
MeSH term(s)	Biophysical Phenomena ; Eye/growth & development ; Models, Biological ; Morphogenesis ; Optic Disk/growth & development
Language	English
Publishing date	2021-10-09
Publishing country	United States
Document type	Journal Article
ZDB-ID	208853-8
ISSN	1079-7114 ; 0031-9007
ISSN (online)	1079-7114
ISSN	0031-9007
DOI	10.1103/PhysRevLett.127.138102
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Book ; Online: Towards out of distribution generalization for problems in mechanics

Yuan, Lingxiao / Park, Harold S. / Lejeune, Emma

2022

Abstract: There has been a massive increase in research interest towards applying data driven methods to problems in mechanics. While traditional machine learning (ML) methods have enabled many breakthroughs, they rely on the assumption that the training (observed) ...

Abstract	There has been a massive increase in research interest towards applying data driven methods to problems in mechanics. While traditional machine learning (ML) methods have enabled many breakthroughs, they rely on the assumption that the training (observed) data and testing (unseen) data are independent and identically distributed (i.i.d). Thus, traditional ML approaches often break down when applied to real world mechanics problems with unknown test environments and data distribution shifts. In contrast, out-of-distribution (OOD) generalization assumes that the test data may shift (i.e., violate the i.i.d. assumption). To date, multiple methods have been proposed to improve the OOD generalization of ML methods. However, because of the lack of benchmark datasets for OOD regression problems, the efficiency of these OOD methods on regression problems, which dominate the mechanics field, remains unknown. To address this, we investigate the performance of OOD generalization methods for regression problems in mechanics. Specifically, we identify three OOD problems: covariate shift, mechanism shift, and sampling bias. For each problem, we create two benchmark examples that extend the Mechanical MNIST dataset collection, and we investigate the performance of popular OOD generalization methods on these mechanics-specific regression problems. Our numerical experiments show that in most cases, while the OOD generalization algorithms perform better compared to traditional ML methods on these OOD problems, there is a compelling need to develop more robust OOD generalization methods that are effective across multiple OOD scenarios. Overall, we expect that this study, as well as the associated open access benchmark datasets, will enable further development of OOD generalization methods for mechanics specific regression problems.
Keywords	Statistics - Machine Learning ; Computer Science - Computational Engineering ; Finance ; and Science ; Computer Science - Machine Learning ; Physics - Data Analysis ; Statistics and Probability
Subject code	006
Publishing date	2022-06-29
Publishing country	us
Document type	Book ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article: A perspective on auxetic nanomaterials.

Park, Harold S / Kim, Sung Youb

Nano convergence

2017 Volume 4, Issue 1, Page(s) 10

Abstract: Nanomaterials have recently been found to exhibit auxetic behavior, or a negative Poisson's ratio ...

Abstract	Nanomaterials have recently been found to exhibit auxetic behavior, or a negative Poisson's ratio, whereby the lateral dimensions of the material expand, rather than shrink, in response to applied tensile loading. In this brief review, we use the form of question-answer to highlight key points and outstanding issues related to the field of auxetic nanomaterials.
Language	English
Publishing date	2017-04-16
Publishing country	England
Document type	Journal Article ; Review
ZDB-ID	2760386-6
ISSN	2196-5404
ISSN	2196-5404
DOI	10.1186/s40580-017-0104-3
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article ; Online: Electro-elastocapillary Rayleigh-plateau instability in dielectric elastomer films.

Seifi, Saman / Park, Harold S

Soft matter

2017 Volume 13, Issue 23, Page(s) 4305–4310

Abstract: We demonstrate, using both finite element simulations and a linear stability analysis, the emergence of an electro-elastocapillary Rayleigh-plateau instability in dielectric elastomer (DE) films under 2D, plane strain conditions. When subject to an ... ...

Abstract	We demonstrate, using both finite element simulations and a linear stability analysis, the emergence of an electro-elastocapillary Rayleigh-plateau instability in dielectric elastomer (DE) films under 2D, plane strain conditions. When subject to an electric field, the DEs exhibit a buckling instability for small elastocapillary numbers. For larger elastocapillary numbers, the DEs instead exhibit the Rayleigh-plateau instability. The stability analysis demonstrates the critical effect of the electric field in causing the Rayleigh-plateau instability, which cannot be induced solely by surface tension in DE films. Overall, this work demonstrates the effects of geometry, boundary conditions, and multi-physical coupling on a new example of Rayleigh-plateau instability in soft solids.
Language	English
Publishing date	2017-06-14
Publishing country	England
Document type	Journal Article
ZDB-ID	2191476-X
ISSN	1744-6848 ; 1744-683X
ISSN (online)	1744-6848
ISSN	1744-683X
DOI	10.1039/c7sm00917h
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article: Interventional Techniques to Support Enteral Nutrition

Long, Simon / Fernando, Dayantha / Boyd, Christina / Katrivesis, James / Park, Harold

Digestive Disease Interventions

(Latest Technologies GI Interventions: Imaging, Techniques, Materials)

2022 Volume 06, Issue 01, Page(s) 52–60

Abstract: ... with medical imaging and knowledge of anatomy, Interventional Radiologists can support a patient's caloric ...

Series title	Latest Technologies GI Interventions: Imaging, Techniques, Materials
Abstract	In patients requiring nutritional support, enteral nutrition has been shown to have many benefits, including improved long-term outcomes, when compared to parenteral alternatives. Given our baseline comfort with medical imaging and knowledge of anatomy, Interventional Radiologists can support a patient's caloric needs and circumvent more invasive surgical methods for placing feeding tubes.
Keywords	Enteral ; parenteral ; nutrition ; feeding
Language	English
Publishing date	2022-01-20
Publisher	Thieme Medical Publishers, Inc.
Publishing place	Stuttgart ; New York
Document type	Article
ISSN	2472-873X ; 2472-8721
ISSN (online)	2472-873X
ISSN	2472-8721
DOI	10.1055/s-0042-1742295
Database	Thieme publisher's database

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Article ; Online: Graphene Origami with Highly Tunable Coefficient of Thermal Expansion.

Ho, Duc Tam / Park, Harold S / Kim, Sung Youb / Schwingenschlögl, Udo

ACS nano

2020 Volume 14, Issue 7, Page(s) 8969–8974

Abstract: The coefficient of thermal expansion, which measures the change in length, area, or volume of a material upon heating, is a fundamental parameter with great relevance for many applications. Although there are various routes to design materials with ... ...

Abstract	The coefficient of thermal expansion, which measures the change in length, area, or volume of a material upon heating, is a fundamental parameter with great relevance for many applications. Although there are various routes to design materials with targeted coefficient of thermal expansion at the macroscale, no approaches exist to achieve a wide range of values in graphene-based structures. Here, we use molecular dynamics simulations to show that graphene origami structures obtained through pattern-based surface functionalization provide tunable coefficients of thermal expansion from large negative to large positive. We show that the mechanisms giving rise to this property are exclusive to graphene origami structures, emerging from a combination of surface functionalization, large out-of-plane thermal fluctuations, and the three-dimensional geometry of origami structures.
Language	English
Publishing date	2020-06-15
Publishing country	United States
Document type	Journal Article
ISSN	1936-086X
ISSN (online)	1936-086X
DOI	10.1021/acsnano.0c03791
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article ; Online: Exploiting elastic buckling of high-strength gold nanowire toward stable electrical probing.

Seo, Jong-Hyun / Kang, Sung-Gyu / Cho, Yigil / Park, Harold S / Yoo, Youngdong / Kim, Bongsoo / Choi, In-Suk / Ahn, Jae-Pyoung

iScience

2022 Volume 25, Issue 10, Page(s) 105199

Abstract: ... in shape has been considered to be avoided. In this study, we utilize the Au nanowire's buckling ...

Abstract	Buckling is a loss of structural stability. It occurs in long slender structures or thin plate structures which is subjected to compressive forces. For the structural materials, such a sudden change in shape has been considered to be avoided. In this study, we utilize the Au nanowire's buckling instability for the electrical measurement. We confirmed that the high-strength single crystalline Au nanowire with an aspect ratio of 150 and 230-nm-diameter shows classical Euler buckling under constant compressive force without failure. The buckling instability enables stable contact between the Au nanowire and the substrate without any damage. Clearly, the
Language	English
Publishing date	2022-09-23
Publishing country	United States
Document type	Journal Article
ISSN	2589-0042
ISSN (online)	2589-0042
DOI	10.1016/j.isci.2022.105199
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Book ; Online: Intrinsic bending flexoelectric constants in two-dimensional materials

Zhuang, Xiaoying / He, Bo / Javvaji, Brahmanandam / Park, Harold S.

2022

Abstract: Flexoelectricity is a form of electromechanical coupling that has recently emerged because, unlike piezoelectricity, it is theoretically possible in any dielectric material. Two-dimensional (2D) materials have also garnered significant interest because ... ...

Abstract	Flexoelectricity is a form of electromechanical coupling that has recently emerged because, unlike piezoelectricity, it is theoretically possible in any dielectric material. Two-dimensional (2D) materials have also garnered significant interest because of their unusual electromechanical properties and high flexibility, but the intrinsic flexoelectric properties of these materials remain unresolved. In this work, using atomistic modeling accounting for charge-dipole interactions, we report the intrinsic flexoelectric constants for a range of two-dimensional materials, including graphene allotropes, nitrides, graphene analogs of group-IV elements, and the transition metal dichalcogenides (TMDCs). We accomplish this through a proposed mechanical bending scheme that eliminates the piezoelectric contribution to the total polarization, which enables us to directly measure the flexoelectric constants. While flat 2D materials like graphene have low flexoelectric constants due to weak $\pi-\sigma$ interactions, buckling is found to increase the flexoelectric constants in monolayer group-IV elements. Finally, due to significantly enhanced charge transfer coupled with structural asymmetry due to bending, the TMDCs are found to have the largest flexoelectric constants, including MoS$_{2}$ having a flexoelectric constant ten times larger than graphene.
Keywords	Condensed Matter - Materials Science
Publishing date	2022-08-20
Publishing country	us
Document type	Book ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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