研究者詳細 - 荒井　規允

論文 - 荒井　規允

分割表示 120 件中 21 - 40 件目／全件表示 >>

Molecular insight into toughening induced by core-shell structure formation in starch-blended bioplastic composites

Yamaguchi Akihiro, Arai Satoshi, Arai Noriyoshi

CARBOHYDRATE POLYMERS （Carbohydrate Polymers） 315 120974 2023年09月

研究論文（学術雑誌）, 査読有り, ISSN 0144-8617

Binary and ternary blends with poly(lactic acid) (PLA), poly(butylene succinate) (PBS), and thermoplastic starch (TPS) were prepared by a melt process to produce biodegradable biomass plastics with both economical and good mechanical properties. The mechanical and structural properties of each blend were evaluated. Molecular dynamics (MD) simulations were also conducted to examine the mechanisms underlying the mechanical and structural properties. PLA/PBS/TPS blends showed improved mechanical properties compared with PLA/TPS blends. The PLA/PBS/TPS blends with a TPS ratio of 25–40 wt% showed higher impact strength than PLA/PBS blends. Morphology observations showed that in the PLA/PBS/TPS blends, a structure similar to that of core-shell particles with TPS as the embedding phase and PBS as the coating phase was formed, and that the trends in morphology and impact strength changes were consistent. The MD simulations suggested that PBS and TPS tightly adhered to each other in a stable structure at a specific intermolecular distance. From these results, it is clear that PLA/PBS/TPS blends are toughened by the formation of a core-shell structure in which the TPS core and the PBS shell adhered well together and stress concentration and energy absorption occurred in the vicinity of the core-shell structure.

Access to Document (DOI)

Aggregation of amphiphilic nanocubes in equilibrium and under shear

Yokoyama Takahiro, Kobayashi Yusei, Arai Noriyoshi, Nikoubashman Arash

SOFT MATTER （Soft Matter） 19 （ 34 ） 6480 - 6489 2023年08月

研究論文（学術雑誌）, 査読有り, ISSN 1744-683X

We investigate the self-assembly of amphiphilic nanocubes into finite-sized aggregates in equilibrium and under shear, using molecular dynamics (MD) simulations and kinetic Monte Carlo (KMC) calculations. These patchy nanoparticles combine both interaction and shape anisotropy, making them valuable models for studying folded proteins and DNA-functionalized nanoparticles. The nanocubes can self-assemble into various finite-sized aggregates ranging from rods to self-avoiding random walks, depending on the number and placement of the hydrophobic faces. Our study focuses on suspensions containing multi- and one-patch cubes, with their ratio systematically varied. When the binding energy is comparable to the thermal energy, the aggregates consist of only few cubes that spontaneously associate/dissociate. However, highly stable aggregates emerge when the binding energy exceeds the thermal energy. Generally, the mean aggregation number of the self-assembled clusters increases with the number of hydrophobic faces and decreases with increasing fraction of one-patch cubes. In sheared suspensions, the more frequent collisions between nanocube clusters lead to faster aggregation dynamics but also to smaller terminal steady-state mean cluster sizes. The results from the MD and KMC simulations are in excellent agreement for all investigated two-patch cases, whereas the three-patch cubes form systematically smaller clusters in the MD simulations compared to the KMC calculations due to finite-size effects and slow aggregation kinetics. By analyzing the rate kernels, we are able to identify the primary mechanisms responsible for (shear-induced) cluster growth and breakup. This understanding allows us to tune nanoparticle and process parameters to achieve desired cluster sizes and shapes.

Access to Document (DOI)

Reproduction of super-multicomponent self-assembled structures and their functionality using coarse-grained molecular simulation - the example of cleansing agents

Yokoyama Takahiro, Miwake Hideki, Hamaguchi Masugu, Nakatake Ryoichi, Arai Noriyoshi

MOLECULAR SYSTEMS DESIGN & ENGINEERING （Molecular Systems Design and Engineering） 8 （ 4 ） 538 - 550 2023年04月

研究論文（学術雑誌）, 査読有り, ISSN 2058-9689

Self-assembly of multi-component systems can provide a large variety of functions, which is impossible for a single-component system, and those multi-component derived functional materials attract attention in various fields such as biomedical, engineering, and materials science. This gives multi-component systems importance, but molecular elucidation of such systems is a major challenge, since this type of complex system has large degrees of freedom. In this study, we focused on cleansing agents as multi-component systems, which are cosmetics products mainly used to remove oily compounds such as makeup, and are multi-component aqueous solutions consisting of many surfactants, moisturizers, and pH regulators. Our aim is to link the macroscopic properties of multi-component systems with the mesoscale structures to elucidate the molecular evidence of functions. We have studied the self-assembled morphologies of cleansing agents using coarse-grained molecular simulations as mesoscale structures and compared them to cleansing performance as a macroscopic property. From the simulation results of morphologies and the experimental results of performance, the key features which explain their functionalities were examined. As a result, it was quantitatively shown that the distribution of specific particles or molecules such as hydrophobic particles both in the bulk state and when they are applied on dirty surfaces is one of the clues to explain the performance. Through molecular designing based on this result, it will be much easier to reach the desired property or performance in the field of multi-component functional materials. Thus, this molecular simulation method will push the field of materials science and materials informatics forward.

Access to Document (DOI)

Wetting hysteresis induces effective unidirectional water transport through a fluctuating nanochannel

Arai Noriyoshi, Yamamoto Eiji, Koishi Takahiro, Hirano Yoshinori, Yasuoka Kenji, Ebisuzaki Toshikazu

NANOSCALE HORIZONS （Nanoscale Horizons） 8 （ 5 ） 652 - 661 2023年02月

研究論文（学術雑誌）, 査読有り, ISSN 2055-6756

We propose a water pump that actively transports water molecules through nanochannels. Spatially asymmetric noise fluctuations imposed on the channel radius cause unidirectional water flow without osmotic pressure, which can be attributed to hysteresis in the cyclic transition between the wetting/drying states. We show that the water transport depends on fluctuations, such as white, Brownian, and pink noises. Because of the high-frequency components in white noise, fast switching of open and closed states inhibits channel wetting. Conversely, pink and Brownian noises generate high-pass filtered net flow. Brownian fluctuation leads to a faster water transport rate, whereas pink noise has a higher capability to overcome pressure differences in the opposite direction. A trade-off relationship exists between the resonant frequency of the fluctuation and the flow amplification. The proposed pump can be considered as an analogy for the reversed Carnot cycle, which is the upper limit of the energy conversion efficiency.

Access to Document (DOI)

Combining Molecular Dynamics and Machine Learning to Analyze Shear Thinning for Alkane and Globular Lubricants in the Low Shear Regime

Yasuda I., Kobayashi Y., Endo K., Hayakawa Y., Fujiwara K., Yajima K., Arai N., Yasuoka K.

ACS Applied Materials and Interfaces （ACS Applied Materials and Interfaces） 15 （ 6 ） 8567 - 8578 2023年02月

研究論文（学術雑誌）, 査読有り, ISSN 19448244

Lubricants with desirable frictional properties are important in achieving an energy-saving society. Lubricants at the interfaces of mechanical components are confined under high shear rates and pressures and behave quite differently from the bulk material. Computational approaches such as nonequilibrium molecular dynamics (NEMD) simulations have been performed to probe the molecular behavior of lubricants. However, the low-shear-velocity regions of the materials have rarely been simulated owing to the expensive calculations necessary to do so, and the molecular dynamics under shear velocities comparable with that in the experiments are not clearly understood. In this study, we performed NEMD simulations of extremely confined lubricants, i.e., two molecular layers for four types of lubricants confined in mica walls, under shear velocities from 0.001 to 1 m/s. While we confirmed shear thinning, the velocity profiles could not show the flow behavior when the shear velocity was much slower than thermal fluctuations. Therefore, we used an unsupervised machine learning approach to detect molecular movements that contribute to shear thinning. First, we extracted the simple features of molecular movements from large amounts of MD data, which were found to correlate with the effective viscosity. Subsequently, the extracted features were interpreted by examining the trajectories contributing to these features. The magnitude of diffusion corresponded to the viscosity, and the location of slips that varied depending on the spherical and chain lubricants was irrelevant. Finally, we attempted to apply a modified Stokes-Einstein relation at equilibrium to the nonequilibrium and confined systems. While systems with low shear rates obeyed the relation sufficiently, large deviations were observed under large shear rates.

Access to Document (DOI)

Effect of temperature on the structure and drug-release behaviour of inclusion complex of beta-cyclodextrin with cyclophosphamide: a molecular dynamics study

Sakai Seiga, Hirano Yoshinori, Kobayashi Yusei, Arai Noriyoshi

SOFT MATTER （Soft Matter） 19 （ 16 ） 2902 - 2907 2023年

研究論文（学術雑誌）, 査読有り, ISSN 1744-683X

Cyclodextrins (CDs) are suitable drug carriers because of their doughnut-shaped cavities with hydrophilic outer and hydrophobic inner surfaces. Temperature-responsive CD-based drug carriers are expected to be one of the most promising candidates for drug delivery systems. In this study, we performed molecular dynamics simulations of the inclusion complex of β-CD with cyclophosphamide (CP) at temperatures from 300 K to 400 K to investigate the temperature dependency of the release behaviour of CP and structural changes of β-CD in an aqueous solution. We analysed the distance between the centres of mass of β-CD and CP and the radius of gyration of β-CD. The CP molecule was released from the β-CD cavity at 400 K, whereas two different inclusion complexes, partially and completely, were observed at T < 400 K. β-CD encapsulating a CP molecule had a more spherical shape and rigidity than β-CD without a CP, and the rigidity of their inclusion complex decreased with increasing temperature. Our findings provide fundamental insights into the behaviours of the β-CD/CP complex and drug release at the molecular level and can facilitate the development of new temperature-responsive drug delivery systems with CD nanocarriers triggered by localised temperature increases using focused ultrasound.

Access to Document (DOI)

Unsupervised deep learning for molecular dynamics simulations: a novel analysis of protein-ligand interactions in SARS-CoV-2 Mpro

Mustali, J; Yasuda, I; Hirano, Y; Yasuoka, K; Gautieri, A; Arai, N

RSC ADVANCES （RSC Advances） 13 （ 48 ） 34249 - 34261 2023年

研究論文（学術雑誌）, 査読有り

Molecular dynamics (MD) simulations, which are central to drug discovery, offer detailed insights into protein-ligand interactions. However, analyzing large MD datasets remains a challenge. Current machine-learning solutions are predominantly supervised and have data labelling and standardisation issues. In this study, we adopted an unsupervised deep-learning framework, previously benchmarked for rigid proteins, to study the more flexible SARS-CoV-2 main protease (Mpro). We ran MD simulations of Mpro with various ligands and refined the data by focusing on binding-site residues and time frames in stable protein conformations. The optimal descriptor chosen was the distance between the residues and the center of the binding pocket. Using this approach, a local dynamic ensemble was generated and fed into our neural network to compute Wasserstein distances across system pairs, revealing ligand-induced conformational differences in Mpro. Dimensionality reduction yielded an embedding map that correlated ligand-induced dynamics and binding affinity. Notably, the high-affinity compounds showed pronounced effects on the protein's conformations. We also identified the key residues that contributed to these differences. Our findings emphasize the potential of combining unsupervised deep learning with MD simulations to extract valuable information and accelerate drug discovery.

Access to Document (DOI)

Correlation between ordering and shear thinning in confined OMCTS liquids

Kobayashi Yusei, Arai Noriyoshi, Yasuoka Kenji

JOURNAL OF CHEMICAL PHYSICS （Journal of Chemical Physics） 157 （ 11 ） 114506 2022年09月

研究論文（学術雑誌）, 査読有り, ISSN 0021-9606

Despite decades of extensive research, the behavior of confined liquids, particularly in the mixed/boundary lubrication regime, remains unelucidated. This can be attributed to several factors, including the difficulty to make direct experimental observations of the behavior of lubricant molecules under nonequilibrium conditions, the high computational cost of molecular simulations to reach steady state, and the low signal-to-noise ratio at extremely low shear rates corresponding to actual operating conditions. In this regard, we studied the correlation between the structure formation and shear viscosity of octamethylcyclotetrasiloxane confined between two mica surfaces in a mixed/boundary lubrication regime. Three different surface separations - corresponding to two-, three-, and five-layered structures - were considered to analyze the effect of confinement. The orientational distributions with one specific peak for n = 2 and two distributions, including a parallel orientation with the surface normal for n > 2, were observed at rest. The confined liquids exhibited a distinct shear-thinning behavior independent of surface separations for a relatively low shear rate, γ˙≲108s-1. However, the shear viscosities at γ˙≲108s-1 depended on the number of layered structures. Newtonian behavior was observed with further increase in the shear rate. Furthermore, we found a strong correlation between the degree of molecular orientation and the shear viscosity of the confined liquids. The magnitude of the shear viscosity of the confined liquids can primarily be determined by the degree of molecular orientation, and shear thinning originates from the vanishing of specific orientational distributions with increasing shear rate.

Access to Document (DOI)

A stochastic Hamiltonian formulation applied to dissipative particle dynamics

Peng L., Arai N., Yasuoka K.

Applied Mathematics and Computation （Applied Mathematics and Computation） 426 127126 - 127126 2022年08月

研究論文（学術雑誌）, 査読有り, ISSN 00963003

In this paper, a stochastic Hamiltonian formulation (SHF) is proposed and applied to dissipative particle dynamics (DPD) simulations. As an extension of Hamiltonian dynamics to stochastic dissipative systems, the SHF provides necessary foundations and great convenience for constructing efficient numerical integrators. As a first attempt, we develop the Störmer–Verlet type of schemes based on the SHF, which are structure-preserving for deterministic Hamiltonian systems without external forces, the dissipative forces in DPD. Long-time behaviour of the schemes is shown numerically by studying the damped Kubo oscillator. In particular, the proposed schemes include the conventional Groot–Warren's modified velocity-Verlet method and a modified version of Gibson–Chen–Chynoweth as special cases. The schemes are applied to DPD simulations and analysed numerically.

Access to Document (DOI)

Theoretical Design of a Janus-Nanoparticle-Based Sandwich Assay for Nucleic Acids

Sato Takumi, Esashika Keiko, Yamamoto Eiji, Saiki Toshiharu, Arai Noriyoshi

INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES （International Journal of Molecular Sciences） 23 （ 15 ） 2022年08月

研究論文（学術雑誌）, 査読有り, ISSN 16616596

Nanoparticles exhibit diverse self-assembly attributes and are expected to be applicable under unique settings. For instance, biomolecules can be sandwiched between dimer nanoparticles and detected by surface-enhanced Raman scattering. Controlling the gap between extremely close dimers and stably capturing the target molecule in the gap are crucial aspects of this strategy. Therefore, polymer-tethered nanoparticles (PTNPs), which show promise as high-performance materials that exhibit the attractive features of both NPs and polymers, were targeted in this study to achieve stable biomolecule sensing. Using coarse-grained molecular dynamics simulations, the dependence of the PTNP interactions on the length of the grafted polymer, graft density, and coverage ratio of a hydrophobic tether were examined. The results indicated that the smaller the tether length and graft density, the smaller was the distance between the PTNP surfaces ((Formula presented.)). In contrast, (Formula presented.) decreased as the coverage ratio of the hydrophobic surface ((Formula presented.)) increased. The sandwiching probability of the sensing target increased in proportion to the coverage ratio. At high (Formula presented.) values, the PTNPs aggregated into three or more particles, which hindered their sensing attributes. These results provide fundamental insight into the sensing applications of NPs and demonstrate the usefulness of PTNPs in sensing biomolecules.

Access to Document (DOI)

ソフトマターの粗視化分子シミュレーション

荒井規允

色材協会誌（一般社団法人色材協会） 95 （ 4 ） 92 - 97 2022年04月

研究論文（研究会，シンポジウム資料等）, 査読有り, ISSN 0010-180X

ソフトマターは与えられた外力に対して特異な応答を示す。この性質を利用し，洗剤や化粧品，ゴムタイヤ，液晶ディスプレイなどさまざまな機能性材料として用いられている。これらの材料の性質は分子構造だけでなく，それらが集まって形成される自己集合構造にも強く影響することが知られている。ゆえに所望の機能をもつ材料の設計には，ソフトマターの自己集合構造を予測・制御することが重要となる。われわれは粗視化分子シミュレーションを用い，さまざまなソフトマターの自己集合挙動，さらには自己集合構造と物性の関係性について研究してきた。ここではこれまで取り組んできた研究の中からいくつかについて紹介する。

散逸粒子動力学法を用いたナノ空間内における高分子グラフトナノ粒子の自己組織化に関する研究

佐藤碧海, 小林祐生, 荒井規允

日本機械学会関東支部総会講演会講演論文集（一般社団法人日本機械学会） 2022.28 （ 0 ） 15F17 2022年

研究論文（研究会，シンポジウム資料等）, 査読有り

In this study, we investigate the morphology and phase diagram of self-assembled polymeric nanoparticles (NPs) confined within nanotubes (NTs) by dissipative particle dynamics simulations. There is a clear relationship between the self-assembling architecture of nanoparticles (NPs) and their physical properties, and Polymer-tethered NPs, which are created by grafting polymers onto NPs to control the self-assembly of NPs, have attracted considerable attention. However, self-assembled structures have not been systematically classified because of the large number of tuning parameters such as the polymer length and graft density. In this study, we investigated the confinement of NPs grafted with three types of polymers: hydrophilic, hydrophobic and Janus surface, hydrophilic and hydrophobic walls. First, we derived the qualitative phase diagram of the axial pressure Pz and the ratio L of NT radius to NP radius. As a result, in polymer-grafted NPs with Janus amphiphilic surface, hydrophobic and hydrophilic polymer tether NPs were found to assemble axially to form an ordered structure, and in hydrophobic NTs, a double helical structure was formed at L=3.0. These simulation results show that the self-assembled structure of polymer tether NPs can be qualitatively predicted based on the chemical properties of NT walls and the surface design of polymer tether NPs.

雲母表面間に閉じ込められた OMCTS の構造とせん断粘度に関する分子動力学シミュレーション

小林祐生, 荒井規允, 泰岡顕治

日本機械学会関東支部総会講演会講演論文集（一般社団法人日本機械学会） 2022.28 （ 0 ） 15F20 2022年

研究論文（研究会，シンポジウム資料等）, 査読有り

Fluids confined in nanochannel exhibit distinct phases and flow properties not shown in the bulk. These confined systems are involved in many industrial and engineering applications such as nanofluidic devices, biological membranes and therefore understanding and controlling the molecular behavior of confined liquids is important. Octamethylcyclotetrasiloxane (OMCTS) is a small macrocycle made of four covalently linked Si(Me)2O units which have been used as a model liquid in the experimental studies. However, much less is known about the mechanisms related to external stimuli such as shear and how those molecular behaviors in a confined system impact the flow properties of the whole liquid. In this study, we have investigated the structure and shear viscosity of OMCTS confined between two mica walls under shear, using molecular dynamics simulation. The results showed layering of OMCTS molecules, depending on the distance between two mica surfaces. In addition to this, the structural changes were observed accompanied by shear-thinning behavior when we applied shear to the system.

Simulation study on the effects of the self-assembly of nanoparticles on thermal conductivity of nanofluids

Tanaka Shogo, Arai Noriyoshi, Kobayashi Yusei

CHEMICAL PHYSICS LETTERS （Chemical Physics Letters） 785 （ 139129 ） 2021年12月

研究論文（学術雑誌）, 査読有り, ISSN 0009-2614

The mechanisms underlying the thermal conductivity behavior of nanofluids have not been completely clarified thus far. This is due to the various competing factors and the lack of a molecular-level understanding of the heat transfer enhancement of nanofluids. In this study, energy-conserving dissipative particle dynamics simulations were conducted to investigate the effects of the self-assembly of nanoparticles (NPs) on the nanoscale heat transfer properties. We demonstrated that considering the balance between the effects of the distance between the NPs and the solvent and the enhancement in thermal conductivity on adding NPs is important for controlling the thermal conductivity of nanofluids.

Access to Document (DOI)

慶應義塾大学理工学部機械工学科荒井研究室

荒井規允

アンサンブル（分子シミュレーション学会） 23 （ 4 ） 290 - 293 2021年10月

研究論文（研究会，シンポジウム資料等）, 査読有り, ISSN 18846750

Effect of chemical design of grafted polymers on the self-assembled morphology of polymer-tethered nanoparticles in nanotubes

Sato Takumi, Kobayashi Yusei, Arai Noriyoshi

JOURNAL OF PHYSICS-CONDENSED MATTER （Journal of Physics Condensed Matter） 33 （ 36 ） 2021年09月

研究論文（学術雑誌）, 査読有り, ISSN 0953-8984

There is a clear relationship between the self-assembling architecture of nanoparticles (NPs) and their physical properties, and they are currently used in a variety of applications, including optical sensors. Polymer-tethered NPs, which are created by grafting polymers onto NPs to control the self-assembly of NPs, have attracted considerable attention. Recent synthetic techniques have made it possible to synthesize a wide variety of polymers and thereby create NPs with many types of surfaces. However, self-assembled structures have not been systematically classified because of the large number of tuning parameters such as the polymer length and graft density. In this study, by using coarse-grained molecular simulation, we investigated the changes in the self-assembled structure of polymer-tethered NP solutions confined in nanotubes due to the chemical properties of polymers. Three types of tethered polymer NP models were examined: homo hydrophilic, diblock hydrophilic-hydrophobic (HI-HO), and diblock hydrophobic-hydrophilic. Under strong confinement, the NPs were dispersed in single file at low axial pressure. As the pressure increased, multilayered lamellar was observed in the HI-HO model. In contrast, under weak confinement, the difference in the pressure at which the phases emerge, depending on the model, was significant. By changing the chemical properties of the grafted polymer, the thermodynamic conditions (the axial pressure in this study) under which the phases appear is altered, although the coordination of NPs remains almost unchanged. Our simulation offers a theoretical guide for controlling the morphologies of self-assembled polymer-tethered NPs, a novel system that may find applications in nanooptical devices or for nanopatterning.

Access to Document (DOI)

Molecular Insight into the Possible Mechanism of Drag Reduction of Surfactant Aqueous Solution in Pipe Flow

Kobayashi Yusei, Gomyo Hirotaka, Arai Noriyoshi

INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES （International Journal of Molecular Sciences） 22 （ 14 ） 7573 - 7573 2021年07月

研究論文（学術雑誌）, 査読有り, ISSN 16616596

The phenomenon of drag reduction (known as the “Toms effect”) has many industrial and engineering applications, but a definitive molecular-level theory has not yet been constructed. This is due both to the multiscale nature of complex fluids and to the difficulty of directly observing self-assembled structures in nonequilibrium states. On the basis of a large-scale coarse-grained molecular simulation that we conducted, we propose a possible mechanism of turbulence suppression in surfactant aqueous solution. We demonstrate that maintaining sufficiently large micellar structures and a homogeneous radial distribution of surfactant molecules is necessary to obtain the drag-reduction effect. This is the first molecular-simulation evidence that a micellar structure is responsible for drag reduction in pipe flow, and should help in understanding the mechanisms underlying drag reduction by surfactant molecules under nonequilibrium conditions.

Access to Document (DOI)

Self-assembly of polymer-tethered nanoparticles with uniform and Janus surfaces in nanotubes

Sato Takumi, Kobayashi Yusei, Michioka Takenobu, Arai Noriyoshi

SOFT MATTER （Soft Matter） 17 （ 15 ） 4047 - 4058 2021年04月

研究論文（学術雑誌）, 査読有り, ISSN 1744-683X

In this study, a coarse-grained molecular simulation was performed to investigate the morphologies and phase diagrams of self-assembled polymer-tethered nanoparticles (NPs) confined in nanotubes (NTs). Unlike ordinary NPs, polymer-tethered NPs have two distinct characteristic lengths, which are key factors that determine their self-assembly. Herein, two distinct types of NT walls and three types of polymer-tethered NPs were considered: hydrophilic and hydrophobic walls, and hydrophilic, hydrophobic, and Janus surfaces. First, the qualitative phase diagrams of the axial pressure,Pz,versusthe ratio of the NT radius to the NP radius,L, were derived. The results revealed that diverse self-assembled morphologies, which are not formed in non-tethered NPs, were observed in the polymer-tethered NPs. For example, three types of ordered structures with different structural characteristic lengths, depending onPz, were obtained. In addition, the effect of the chemical nature of the polymer-tethered NP surface on the self-assembled morphology confined in NTs was investigated. Clusters of water molecules were formed, particularly in the hydrophobic polymer-tethered NPs, and these clusters caused the structural distortion of the NP. Moreover, in the polymer-tethered NPs with the Janus amphiphilic surface, the hydrophobic and hydrophilic polymer tethered NPs assembled in the axial direction to form an ordered structure, and a double-helix structure was formed atL= 3.0 in the hydrophobic NT. The results of these simulations indicate that the self-assembly behaviours of polymer-tethered NPs can be qualitatively predicted based on the chemical nature of the NT walls and the surface design of the polymer-tethered NP.

Access to Document (DOI)

Nanotube Active Water Pump Driven by Alternating Hydrophobicity

Arai Noriyoshi, Koishi Takahiro, Ebisuzaki Toshikazu

ACS NANO （ACS Nano） 15 （ 2 ） 2481 - 2489 2021年02月

研究論文（学術雑誌）, 査読有り, ISSN 1936-0851

Water transport must be efficiency controlled for the future sustainability of life. Various water transport systems using carbon nanotubes have been proposed in recent years. Although these systems are more permeable than aquaporins, their water transport is passive. In this study, we successfully demonstrate an active water pump driven by simple hydrophobic interaction through computer simulation. Even in the absence of a pressure- or density-gradient, the proposed pump can actively transport water molecules by alternately switching the hydrophobicity of the pump surface. The water transport rate can be easily controlled by varying the time interval of switching. The pump with optimized switching time exhibits prominent water permeance. The results obtained herein can be applied in various water transport technologies because of the simple mechanics. The proposed water pump has the potential to realize an effective device such as a low-energy artificial purification system.

Access to Document (DOI)

粗視化分子シミュレーションを用いたコロイド-ポリマー混合溶液の自己集合と粘性挙動に関する研究

小林祐生, 荒井規允, Arash Nikoubashman

日本機械学会関東支部総会講演会講演論文集（一般社団法人日本機械学会） 2021.27 （ 0 ） 10C12 2021年

研究論文（研究会，シンポジウム資料等）, 査読有り

We investigate the structure and rheological properties of dilute colloid-polymer mixtures at rest and under shear via molecular simulations that take into account hydrodynamic interactions. Mixtures of amphiphilic Janus colloids (JCs) and hydrophobic/amphiphilic polymers are considered for various solvent qualities and polymer concentrations. Free polymers, small colloidal micelles, and small hybrid aggregates coexist in mixtures with slightly hydrophobic homopolymers. As the solvent quality worsens, all polymers aggregate into small droplets, covered and stabilized by the JCs. In mixtures with amphiphilic polymers, we observe the coexistence of free polymers, purely polymeric micelles, and hybrid aggregates. At small shear rates, all mixtures exhibit a Newtonian-like response with intrinsic shear viscosities that are up to two times as large as of pure suspensions of non-adsorbing colloids at the same concentration. Further, the mean aggregation number increases slightly due to the flow-enhanced collision of aggregates. At larger shear rates, however, the aggregates break up, the polymers align in the flow direction, and the mixtures become shear-thinning. This shear-induced breakup occurs at stronger shear compared to pure JC suspensions, indicating that the adsorbed polymers reinforce the hybrid aggregates.

　前のページ - 次のページ　

荒井 規允

論文 - 荒井 規允

荒井　規允

論文 - 荒井　規允