論文 - 荒井　規允

Nanochannel with uniform and Janus surfaces: Shear thinning and thickening in surfactant solution

N Arai, K Yasuoka, XC Zeng

Langmuir 28 (5), 2866-2872 （Langmuir）  28 （ 5 ） 2866 - 2872 2012年

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  0743-7463

　概要を見る

On basis of molecular simulation of confined surfactant solutions, we show that by adding chemical patterns on the inner surface of nanochannels dynamical properties of the confined surfactant solutions could be modified from shear thinning to shear thickening. To this end, we select uniformly hydrophobic and hydrophilic surfaces as well as a stripe-patterned Janus surface as three prototype confining surfaces of nanochannels. In all three nanochannels, when the surfactant solution is under relatively low shear rates, it shears thin. Under moderate shear rates, a sharp decrease in the shear viscosity could occur due to surfactant morphology transition. Under relatively high shear rates, a shear-thinning-to-thickening transition can emerge due to the tendency of stratification normal to the confining surface. Our simulation study offers a guide to steering dynamic properties of surfactant fluids in nanofluidic devices through engineering surfaces of nanochannels by design. © 2012 American Chemical Society.

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Atomistic study of the morphology of graphene on Si and SiC substrates

S Seto, N Arai, K Shintani

MRS Online Proceedings Library Archive 1407 （Materials Research Society Symposium Proceedings）  1407   91 - 96 2012年

研究論文（国際会議プロシーディングス）, 共著, 査読有り

　概要を見る

The morphology of graphene on Si and SiC substrates is investigated using molecular-dynamics simulation. The effects of the size and orientation of graphene on its roughness, distance from the substrate, and periodic structure are examined. The roughness and distance show the size dependency which agrees with the size dependency of the ratio of the periphery length of graphene to its area. It is found there are some cases in which the roughness of graphene can be suppressed. © 2012 Materials Research Society.

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3PT155 フリップフロップのダイナミクスの直接的観察 (日本生物物理学会第 50 回年会 (2012 年度))

T Akimoto, N Arai, E Yamamoto, K Yasuoka, M Yasui

生物物理 52, S167 （一般社団法人 日本生物物理学会）  52 （ 0 ） S167 2012年

研究論文（研究会，シンポジウム資料等）, 共著, 査読有り,  ISSN  0582-4052

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Molecular dynamics of carbon nanobearings

Sato K., Arai N., Shintani K.

Materials Research Society Symposium Proceedings （Materials Research Society Symposium Proceedings）  1204   103 - 108 2010年08月

研究論文（国際会議プロシーディングス）, 査読有り

　概要を見る

A concept of nanoscale bearing structures utilizing nanocarbon materials is presented based on the prediction via molecular dynamics simulations. The proposed mechanism consists of a graphene layer, intercalated single walled carbon nanotubes (SWNTs), and substrate graphenes. It is found that the friction against the movement of the uppermost graphene is smallest for the 1 SWNT model. © 2010 Materials Research Society.

Asymmetric Brownian motor driven by bubble formation in a hydrophobic channel

N Arai, K Yasuoka, T Koishi, T Ebisuzaki

ACS nano 4 (10), 5905-5913 （ACS Nano）  4 （ 10 ） 5905 - 5913 2010年

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  1936-0851

　概要を見る

The "asymmetric Brownian ratchet model" is a variation of Feynman's ratchet and pawl system proposed. In this model, a system consisting of a motor and a rail has two binding states. One is the random Brownian state, and the other is the asymmetric potential state. When the system is alternatively switched between these states, the motor can be driven in one direction. This model is believed to explain nanomotor behavior in biological systems. The feasibility of the model has been demonstrated using electrical and magnetic forces; however, switching of these forces is unlikely to be found in biological systems. In this paper, we propose an original mechanism of transition between states by bubble formation in a nanosized channel surrounded by hydrophobic atoms. This amounts to a nanoscale motor system using bubble propulsion. The motor system consists of a hydrophobic motor and a rail on which hydrophobic patterns are printed. Potential asymmetry can be produced by using a left-right asymmetric pattern shape. Hydrophobic interactions are believed to play an important role in the binding of biomolecules and molecular recognition. The bubble formation is controlled by changing the width of the channel by an atomic distance (∼0.1 nm). Therefore, the motor is potentially more efficient than systems controlled by other forces, in which a much larger change in the motor position is necessary. We have simulated the bubble-powered motor using dissipative particle dynamics and found behavior in good agreement with that of motor proteins. Energy efficiency is as high as 60%. © 2010 American Chemical Society.

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Molecular simulation at solid-liquid interface

K Yasuoka, T Koishi, T Mlma, N Arai

Toraibarojisuto/Journal of Japanese Society of Tribologists 55 (4), 236-241 （Toraibarojisuto/Journal of Japanese Society of Tribologists）  55 （ 4 ） 236 - 241 2010年

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  0915-1168

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Molecular dynamics of carbon nanobearings

K Sato, N Arai, K Shintani

2009 MRS Fall Meeting, 103-108 2010年

研究論文（国際会議プロシーディングス）, 査読有り

固液界面の物理 固液界面現象の分子シミュレーション

K YASUOKA, T KOISHI, T MIMA, N ARAI

トライボロジスト 55 (4), 236-241 2010年

研究論文（研究会，シンポジウム資料等）, 査読有り

固液界面現象の分子シミュレーション

泰岡顕治， 古石貴裕， 美馬俊喜

トライボロジスト= Journal of Japanese Society of Tribologists/日本トライボロジー学会 … 55 （ 4 ） 236 - 241 2010年

散逸粒子動力学法を用いた界面活性剤水溶液の自己組織化の解明および高効率ナノモーターシステムの設計・開発

荒井　規允

2009年03月

学位論文（博士）, 単著, 筆頭著者, 責任著者, 査読有り

Molecular dynamics of carbon nanobearings

K Shintani, N Arai

MRS Online Proceedings Library Archive 1204 2009年

研究論文（国際会議プロシーディングス）, 査読有り

Self-assembly of surfactants and polymorphic transition in nanotubes

N Arai, K Yasuoka, XC Zeng

Journal of the American Chemical Society 130 (25), 7916-7920 （Journal of the American Chemical Society）  130 （ 25 ） 7916 - 7920 2008年

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  0002-7863

　概要を見る

We study self-assembly and polymorphic transitions of surfactant molecules in water within a nanotube and the effect of water-nanotube interactions on the self-assembly morphologies. We present a simulation evidence of a cornucopia of polymorphic structures of surfactant assemblies-many of which have not been observed in bulk solutions-through adjusting the water-nanotube chemical interactions which range from hydrophilic to hydroneutral and to hydrophobic. The ability to control the morphologies of surfactant assemblies within nanoscale confinement can be used for patterning the interior surface of nanochannels for application in nanofluidics and nanomedical devices. © 2008 American Chemical Society.

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Dissipative particle dynamics studies on the self-assembling dynamics of the peptide amphiphiles

T Seki, N Arai, T Ozawa, T Shimada, K Yasuoka, A Hotta

MRS Online Proceedings Library Archive 1135 （Materials Research Society Symposium Proceedings）  1135   143 - 149 2008年

研究論文（学術雑誌）, 共著, 査読有り

　概要を見る

A coarse-grained model of peptide amphiphiles (PA) dissolved in aqueous solution was presented, where the effects of PA concentration, temperature and shear stress upon the selfassembly of PA were numerically studied by dissipative particle dynamics (DPD) simulation. We technically investigate the repulsion parameter ahw which indicates the repulsion force between the hydrophilic head of PA and water molecules, hence, at the same time, indicating the change in temperature. It was found that ahw played an important role in the self-assembly dynamics and in the resulting micro-structures of PA. By imposing shear strain on the simulation system, the formation of wormlike PA micelles was accelerated. The simulation results were in good agreement with our previous experimental results and the mechanism of shear-induced transition was proposed. © 2009 Materials Research Society.

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ナノチューブ内の界面活性剤水溶液の自己組織化

荒井 規允, 泰岡 顕治, Xiao C. Zeng

理論応用力学講演会 講演論文集 （日本学術会議 「機械工学委員会・土木工学・建築学委員会合同IUTAM分科会」）  57 （ 0 ） 37 - 37 2008年

研究論文（研究会，シンポジウム資料等）, 共著, 査読有り

　概要を見る

界面活性剤水溶液はバルクで様々な形態を示す．球状ミセルや棒状ミセル，紐状ミセル，二分子膜，ベシクルなどが存在することが知られている．本研究では，ナノチューブに閉じ込められた界面活性剤水溶液の自己組織化について，散逸粒子動力学シミュレーションを行った．

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Spontaneous self-assembly process for threadlike micelles

N Arai, K Yasuoka, Y Masubuchi

The Journal of chemical physics 126 (24), 244905 （Journal of Chemical Physics）  126 （ 24 ） 244905 - 244905 2007年

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  0021-9606

　概要を見る

More than 100 μs dissipative particle dynamics simulations were carried out to investigate the spontaneous formation process of threadlike micelles from the random configuration for surfactant molecules. Stable spherical micelles were formed during the earlier stage. These spherical micelles fused to each other and grew into rodlike and threadlike micelles during the later stage. The length and radius of a micelle were estimated by tracing the backbone positions and the distance between the head group particles and the backbone of the micelles, respectively. The ratio of the largest to the smallest principal moments of inertia for each micelle was calculated as the micelle shape. © 2007 American Institute of Physics.

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D244 剪断下の散逸粒子動力学シミュレーションによる紐状ミセル水溶液のダイナミクスの解明(分子動力学2)

荒井 規允, 泰岡 顕治, 増渕 雄一

熱工学コンファレンス講演論文集 （一般社団法人 日本機械学会）  2007 （ 0 ） 319 - 320 2007年

研究論文（研究会，シンポジウム資料等）, 共著, 査読有り

　概要を見る

A micelle is the self-assembly of surfactant molecules formed in surfactant aqueous solution. The micelle has various forms such as a threadlike, spherical, discoid, and bilayer. Particularly, the threadlike micelle has the great possibility of the application in the industry, utilizing the uniqueness in its formation. However, an overall understanding of the formation dynamics of the threadlike micelle has not been accomplished, because of the so-called 'mesoscopic problem' in dynamics. In this paper to clarify the multiscale dynamics in the threadlike micelles we adopted the Dissipative Particle Dynamics (DPD) simulations. Moreover, the shear stress was put on a similar system, and it comnpared it without shear stress.)

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散逸粒子動力学シミュレーションによる紐状ミセル水溶液のダイナミクスの解明

荒井 規允, 泰岡 顕治, 増渕 雄一

理論応用力学講演会 講演論文集 （日本学術会議 「機械工学委員会・土木工学・建築学委員会合同IUTAM分科会」）  56 （ 0 ） 246 - 246 2007年

研究論文（研究会，シンポジウム資料等）, 共著, 筆頭著者, 査読有り

　概要を見る

界面活性剤の自己組織体の1つとして<B>紐状ミセル</B>がある．紐状ミセルはその組織形成ダイナミクスの特異性から工業的に様々な応用が模索され，一部実用化されている．しかしながら紐状ミセルを含む系のダイナミクスは時間と空間のスケールが広範囲に渡り，メソスケールダイナミクスの典型的な問題であるため理解が進んでいない．工業的応用の際にコスト等の面から重要だと思われる生成過程も，紐状ミセル系では明らかになっていない．したがって，本研究では紐状ミセルのダイナミクスを明らかにすることを目的として，メソスケールのシミュレーション方法である<B>散逸粒子動力学</B> (DPD:Dissipative Particle Dynamics) 法を用いた．

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散逸粒子動力学シミュレーションによる紐状ミセルの生成過程の解明

荒井　規允

2006年03月

学位論文（修士）, 単著, 筆頭著者, 責任著者, 査読有り

A221 散逸粒子動力学シミュレーションによる剪断流れ下における紐状ミセルの生成過程の解明(マイクロ・ナノスケール7)

荒井 規允, 泰岡 顕治, 増渕 雄一

熱工学コンファレンス講演論文集 （一般社団法人 日本機械学会）  2006 （ 0 ） 231 - 232 2006年

研究論文（研究会，シンポジウム資料等）, 共著, 筆頭著者, 査読有り

　概要を見る

A micelle is the self-assembly of surfactant molecules formed in surfactant aqueous solution. The micelle has various forms such as a threadlike, spherical, discoid, and bilayer. Particularly, the threadlike micelle has the great possibility of the application in the industry, utilizing the uniqueness in its formation. However, an overall understanding of the formation dynamics of the threadlike micelle has not been accomplished, because of the so-called 'mesoscopic problem' in dynamics. In this paper to clarify the multiscale dynamics in the threadlike micelles we adopted the Dissipative Particle Dynamics (DPD) simulations. Moreover, the shear stress was put on a similar system, and it comnpared it without shear stress.

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2807 Dissipative Particle Dynamics(DPD)法を用いた紐状ミセルの生成過程のシミュレーション(OS-28B,OS-28 熱流体の分子シミュレーション)

荒井 規允, 泰岡 顕治, 増渕 雄一

計算力学講演会講演論文集 （一般社団法人 日本機械学会）  2005 （ 0 ） 47 - 48 2005年

研究論文（研究会，シンポジウム資料等）, 共著, 筆頭著者, 査読有り

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