Faculty Profiles - ZHANG, Hedong

PubMed

Interfacial slip quantification in nanogaps using squeeze flow velocimetry Reviewed

Ozeki H., Azuma N., Fukuzawa K., Itoh S., Zhang H., Song Y.

Physics of Fluids Vol. 37 ( 5 ) 2025.5

Language：English Publishing type：Research paper (scientific journal) Publisher：Physics of Fluids

Understanding interfacial slip in nanogaps is crucial for modeling fluid flow in mechanical and analytical systems. To quantify slip length and shear stress at the liquid-solid interface, we measured the velocity of squeeze flow as fluid was pressed between solid surfaces. Our results showed that slip length varied with lateral positions and gap heights, while shear stress had a noticeable threshold beyond which slip begins, indicating the limiting shear stress model for interfacial slip in nanogaps. These insights enhance our understanding of interfacial slip phenomena in nanogaps and provide a foundation for modeling their influence on fluid flow.

DOI： 10.1063/5.0271999

Detection and Behaviors of TEMPO Derivatives in Seven Mass Spectrometry Ionization Methods Reviewed Open Access

Oyama, KI; Hor, S; Tsukamoto, M; Zhang, HD

JOURNAL OF MASS SPECTROMETRY Vol. 60 ( 4 ) page： e5122 2025.4

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Mass Spectrometry

Four 2,2,6,6-tetramethylpiperidinyloxyl (TEMPO) derivatives with molecular weights of 339–1131 Da were synthesized to investigate their ionization behaviors in fast atom bombardment (FAB), electron ionization (EI), direct analysis in real time (DART), electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), atmospheric pressure photoionization (APPI), and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). These include 4-dodecanoylamino-2,2,6,6-tetramethyl-1-piperidinyloxy (1), 4-dodecylamino-2,2,6,6-tetramethyl-1-piperidinyloxy (2), N,N′-bis(2,2,6,6-tetramethyl-1-oxyl-4-piperidinyl)dodecanediamide (3), and bis-cholesterol TEMPO derivative 4. For TEMPO derivatives 1 and 2 (molecular weights: 353 Da and 339 Da), [M]+, [M+H]+•, and [M+2H]+ peaks were detected. TEMPO derivative 3, containing two TEMPO moieties, showed [M]+•, [M+H]+, [M+2H]+•, and [M+3H]+ peaks. EI was optimal for smaller derivatives, as molecular ion peaks were predominant. For larger analytes, molecular ion intensities weakened, favoring hydrogen adduct peaks. EI and DART-MS failed to detect bis-cholesterol TEMPO derivative 4. Under APCI and APPI-MS, N–O bond cleavage was observed. MALDI-MS detected only hydrogen adduct peaks. FAB, ESI, APCI, and APPI-MS detections varied with scan numbers, unlike EI, DART, and MALDI-MS.

DOI： 10.1002/jms.5122

Bulk conformation and shear-induced transitions in bottlebrush poly(alkyl methacrylate): The role of side chain length and polymer flexibility Reviewed Open Access

Himanshu Shekhar, Yuma Chikazawa, Yuxi Song, Hedong Zhang

Tribology International Vol. 204 page： 110476 - 110476 2025.4

Wearable PZT Piezoelectric Sensor Device for Accurate Arterial Pressure Pulse Waveform Measurement Reviewed Open Access

Li, MY; Aoyama, J; Inayoshi, K; Zhang, HD

ADVANCED ELECTRONIC MATERIALS 2025.1

Stretching and immobilizing a single DNA molecule on a glass surface using pressure flow in a microchannel for super-resolution imaging Reviewed Open Access

Naoki Azuma, Ryotaro Suzuki, Kenji Fukuzawa, Shintaro Itoh, Hedong Zhang

AIP Advances Vol. 15 ( 1 ) 2025.1

Language：English Publishing type：Research paper (scientific journal) Publisher：AIP Publishing

Single-DNA analysis combines fluorescence microscopy with a method of stretching a single DNA molecule from its random coil shape to a linear shape. Although super-resolution imaging methods can be used for analyzing the DNA with a higher lateral resolution, these methods require several seconds to minutes to obtain a super-resolution image of the entire DNA molecule. Therefore, immobilizing the stretched DNA molecules on the substrate surface is essential for preventing the decrease in the lateral resolution caused by thermal fluctuations of the molecule. Previous studies utilized a method to use super-resolution imaging methods, in which a DNA molecule can be stretched by the surface tension of the air–liquid interface and immobilized on a glass surface treated with a silane coupling agent. However, achieving control over the stretch ratio of the DNA molecule poses challenges because of the difficulty in accurately adjusting the surface tension. In this study, we used the combination of stretching DNA molecules using pressure flow in a microchannel and immobilizing them on a glass surface treated with a silane coupling agent. Our results indicated that this method enabled the control of the stretch ratio of the molecule by adjusting the flow velocity and the super-resolution imaging while reducing thermal fluctuation by immobilizing the molecule on the surface. Combining the method with the super-resolution imaging method enables the analysis of single DNA molecules with higher accuracy.

DOI： 10.1063/5.0223375

Mechanism of Hydrogen Generation by Decomposition of Lubricating Oils: Effect of Lubricating Oils on Hydrogen Brittle Flaking Reviewed Open Access

Ito Motohiro, Kawamura Takayuki, Sakaguchi Tomoya, Suzuki Yuichi, Zhang Hedong, Nagaoka Masataka

Tribology Online Vol. 19 ( 6 ) page： 517 - 524 2024.11

Language：English Publishing type：Research paper (scientific journal) Publisher：Japanese Society of Tribologists

In the rolling bearings used in automotive electrical instruments and auxiliary devices such as alternators, it is well-known that brittle flaking occurs earlier than expected due to hydrogen embrittlement. Despite this, in the flaking mechanism, the generation process of hydrogen atoms in lubricating oils has not been clarified microscopically. In this study, we theoretically elucidated the reaction processes of poly-α-olefin (PAO) and alkyl diphenyl ether (ADE) molecules using quantum mechanical (QM) calculations. The basic and important mechanism for the generation of hydrogen molecules was clarified for the first time at the atomic level. Upon considering the generation mechanism on ceramics and nascent steel surfaces, it was found that the reason why the amount of hydrogen generation is similar regardless of the type of lubricant is because the energy required for hydrogen generation is almost the same. Furthermore, it was suggested that the suppression of hydrogen brittle flaking by ADE was due to the low exposure frequency of the nascent steel surface.

DOI： 10.2474/trol.19.517

Temperature Dependence of Viscoelasticity of Lubricating Oil with Adsorptive Polymer Additives Sheared in Nanogaps Reviewed Open Access

Takumi Nozue, Shintaro Itoh, Naoya Okubo, Kenji Fukuzawa, Hedong Zhang, Naoki Azuma

Tribology Letters Vol. 72 ( 3 ) 2024.9

Language：English Publishing type：Research paper (scientific journal) Publisher：Springer Science and Business Media LLC

Abstract

Adsorptive polymer additives have been reported to improve the retention capacity of oil films under hydrodynamic lubrication and to reduce friction under boundary lubrication. These effects are believed to result from the formation of a polymer adsorption film on the surface that acts as a lubricious coating. Polymer adsorption films have become dominant in nanometer-order microscopic gaps. However, their mechanical properties are difficult to quantify. This hinders the development of polymer additives. In our previous study, we successfully measured the shear viscoelasticity of lubricants (base oils) sheared in nanogaps using an originally developed measurement method called the fiber wobbling method (FWM). In this study, we measured the shear viscoelasticity of polymer-added lubricants in nanogaps by using FWM. In addition, we developed a heating stage in the FWM to quantify the temperature dependence of shear viscoelasticity in nanogaps. As a result, the viscosity index improved and elasticity was observed in the nanogap, where the polymer adsorption film was dominant. Furthermore, our results indicated that the elasticity of the adsorbed polymer film originated from entropic elasticity.

Graphical Abstract

DOI： 10.1007/s11249-024-01884-y

Other Link： https://link.springer.com/article/10.1007/s11249-024-01884-y/fulltext.html

Ionic liquid lubricity enhancement with bio-oil derived from microwave pyrolysis of bamboo Reviewed International coauthorship

Ariffin, NAAM; Foong, SY; Chong, WWF; Lam, SS; Ng, JH; Zhang, HD

INDUSTRIAL CROPS AND PRODUCTS Vol. 214 2024.8

Molecular dynamics study of confined liquid film viscosity in Constant-Pressure and Constant-Distance systems Reviewed International coauthorship Open Access

Chen, XY; Zhang, HD; Yokoyama, H; Chong, WWF; Fukuzawa, K; Itoh, S

JOURNAL OF MOLECULAR LIQUIDS Vol. 404 page： 124955 - 124955 2024.6

Numerical modelling of macro lubricity in conjunctions with nanometer-thick films Reviewed International coauthorship

Chong, WWF; Zhang, HD; Li, YR

TRIBOLOGY INTERNATIONAL Vol. 193 2024.5

Correlation between viscoelastic response and frictional properties of hydrated zwitterionic polymer brush film in narrowing shear gap Reviewed Open Access

Fengchang Lin, Shintaro Itoh, Kenji Fukuzawa, Hedong Zhang, Naoki Azuma

Journal of Colloid and Interface Science Vol. 655 page： 253 - 261 2024.2

Coarse-Grained Molecular Dynamics Simulations of Organic Friction Modifier Adsorption on Rough Surfaces under Shear Reviewed International coauthorship Open Access

J. Tang, W.W.F. Chong, H. Zhang

Lubricants Vol. 12 ( 2 ) page： 30 2024.1

Enhancing boundary friction and wear reduction through adsorption control in protic ionic liquid and carbon mixtures Reviewed International coauthorship

Ariffin, NAAM; Lee, CT; Lee, MB; Halid, I; Hamdan, SH; Ismail, MI; Chong, WWF; Zhang, HD

JOURNAL OF MATERIALS SCIENCE Vol. 59 ( 3 ) page： 794 - 809 2024.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Materials Science

This study addresses the challenge of enhancing lubrication performance by exploring the potential of a protic ionic liquid (IL), [Oley][Oleic], in conjunction with carbon nanotube (CNT) mixtures. The primary objective is to determine the optimal CNT concentration that achieves effective lubrication for the IL-based lubricant. Through experimental investigation, notable reductions of 19.8 % in friction and 67.2% in wear are demonstrated when [Oley][Oleic] is blended with the optimum CNT concentration at 0.10 wt%. This study employs a friction-derived adsorption model to elucidate the underlying mechanisms of friction. The results indicate that the addition of CNTs leads to a larger adsorption surface coverage area of the lubricant molecules, resulting in decreased friction and wear. Synergistic attractive cooperative interactions among the IL molecules in the presence of CNTs are identified as a key factor in enhancing adsorption efficiency. These findings provide insights into the interaction between [Oley][Oleic] and CNTs when sheared, offering a predictive framework for understanding friction and wear behaviour specific to IL-based lubricants. By presenting a solution for reducing friction and wear, this study contributes to the development of energy-efficient and environmentally-friendly lubrication practices, opening avenues for further advancements in the field of lubrication and promoting sustainable tribological solutions for diverse applications.

DOI： 10.1007/s10853-023-09257-x

Effect of Water on Mechano-Chemical Reactions of Perfluoropolyether Lubricant Films in Heat-Assisted Magnetic Recording: A Reactive Molecular Dynamics Study Reviewed

Hydration–lubrication performance improvement via synergistic effects of free polymers and polymer brushes Reviewed International journal

Fengchang Lin, Shintaro Itoh, Tomoko Hirayama, Chizuru Hirooka, Yuxi Song, Kenji Fukuzawa, Hedong Zhang, Naoki Azuma

Tribology International Vol. 191 page： 109189 2023.12

Quantitative Measurement of Squeeze Flow Distribution in Nanogaps by Particle Image Velocimetry Using Quantum Dots Reviewed

Naoki Azuma, Hidetaka Ozeki, Katsuki Miki, Kenji Fukuzawa, Shintaro Itoh, Hedong Zhang

Tribology Letters Vol. 71 page： 112 2023.9

Xingyu Chen, Koya Inayoshi, Hedong Zhang, Nobuaki Koga, Kenji Fukuzawa, Shintaro Itoh, Naoki Azuma

Tribology International Vol. 187 page： 108674 - 108674 2023.9

Revealing the Dependence of Lubricant Viscosity on Molecular Structure by Measuring the Temperature Dependence of Dielectric Relaxation and Viscosity Reviewed

Uchida Kyosuke, Itoh Shintaro, Fukuzawa Kenji, Azuma Naoki, Zhang Hedong

Tribology Online Vol. 18 ( 3 ) page： 91 - 96 2023.7

Language：English Publishing type：Research paper (scientific journal) Publisher：Japanese Society of Tribologists

Reducing the viscosity of the lubricant is an effective way to improve the energy efficiency of automobiles. However, designing a lubricant with the desired properties requires elucidating the relationship between viscosity and molecular structure. In this study, we measured the temperature dependence of the dielectric relaxation of model lubricants with different molecular structures. Dielectric relaxation measurements were used to evaluate the influence of ambient viscosity on the motility of single molecules. In addition, we measured the temperature dependence of the lubricant viscosity using a rotational viscometer. By comparing the flow viscosity and dielectric relaxation measurement results, we showed that the activation volume and energy of the luburicant, which determine viscosity, can be resolved. As a result, we succeeded in quantitatively evaluating the contribution of molecular structure to changes in the activation energy, and elucidated the effect of the density of polar groups per molecule on changes in the activation volume.

DOI： 10.2474/trol.18.91

High temporal resolution measurement of the curing process of nanometer-thick photocurable liquid films using the fiber wobbling method Reviewed Open Access

Shintaro Itoh, Kohei Aratani, Fengchang Lin, Kenji Fukuzawa, Naoki Azuma, Hedong Zhang

Applied Physics Express Vol. 16 ( 7 ) page： 076501 2023.7

Effects of Polarity of Polymers on Conformation and Lubricating Film Formation of Adsorbed Films Reviewed Open Access

Song, YX; Fukuzawa, K; Hirayama, T; Yamashita, N; Yamada, NL; Itoh, S; Azuma, N; Zhang, HD

MACROMOLECULES Vol. 56 ( 5 ) page： 1954 - 1964 2023.3

Language：English Publishing type：Research paper (scientific journal) Publisher：Macromolecules

The conformations and lubricating film formation ability of adsorbed films on metal surfaces formed by poly(alkyl methacrylate) (PAMA) homopolymers with different polarities from nonpolar lubricant oil were investigated. It was found that as the polarity of the polymers became higher, the chains in the adsorbed films adsorbed more loosely to the surfaces (i.e., they formed more loops and tails). The loosely adsorbed chains temporarily trapped free polymer chains flowing into the gap between sliding surfaces, resulting in a much thicker lubricating film. Thus, the sliding surfaces were better protected from wear caused by direct contact. On the other hand, flattened chains occupying in the adsorbed film formed by low polarity-polymers could not trap free polymer chains, resulting in a thinner lubricating film.

DOI： 10.1021/acs.macromol.2c02238

Molecules with a TEMPO-based head group as high-performance organic friction modifiers Reviewed Open Access

Jinchi Hou, Masaki Tsukamoto, Seanghai Hor, Xingyu Chen, Juntao Yang, Hedong Zhang, Nobuaki Koga, Koji Yasuda, Kenji Fukuzawa, Shintaro Itoh, Naoki Azuma

Friction Vol. 11 ( 2 ) page： 316 - 332 2023.2

Language：English Publishing type：Research paper (scientific journal) Publisher：Springer Science and Business Media LLC

Abstract

High-performance organic friction modifiers (OFMs) added to lubricating oils are crucial for reducing energy loss and carbon footprint. To establish a new class of OFMs, we measured the friction and wear properties of N-(2,2,6,6-tetramethyl-1-oxyl-4-piperidinyl)dodecaneamide referred to as C12Amide-TEMPO. The effect of its head group chemistry, which is characterized by a rigid six-membered ring sandwiched by an amide group and a terminal free oxygen radical, was also investigated with both experiments and quantum mechanical (QM) calculations. The measurement results show that C12Amide-TEMPO outperforms the conventional OFMs of glyceryl monooleate (GMO) and stearic acid, particularly for load-carrying capacity, wear reduction, and stability of friction over time. The friction and wear reduction effect of C12Amide-TEMPO is also greatly superior to those of C12Ester-TEMPO and C12Amino-TEMPO, in which ester and amino groups replace the amide group, highlighting the critical role of the amide group. The QM calculation results suggest that, in contrast to C12Ester-TEMPO, C12Amino-TEMPO, and the conventional OFMs of GMO and stearic acid, C12Amide-TEMPO can form effective boundary films on iron oxide surfaces with a unique double-layer structure: a strong surface adsorption layer owing to the chemical interactions of the amide oxygen and free radical with iron oxide surfaces, and an upper layer owing to the interlayer hydrogen-bonding between the amide hydrogen and free radical or between the amide hydrogen and oxygen. Moreover, the intralayer hydrogen-bonding in each of the two layers is also possible. We suggest that in addition to strong surface adsorption, the interlayer and intralayer hydrogen-bonding also increases the strength of the boundary films by enhancing the cohesion strength, thereby resulting in the high tribological performance of C12Amide-TEMPO. The findings in this study are expected to provide new hints for the optimal molecular design of OFMs.

DOI： 10.1007/s40544-022-0610-0

Characterization of organic friction modifiers using lateral force microscopy and Eyring activation energy model Reviewed

Other Link： https://link.springer.com/article/10.1007/s40544-022-0610-0/fulltext.html

Jinchi Hou, Masaki Tsukamoto, Hedong Zhang, Kenji Fukuzawa, Shintaro Itoh, Naoki Azuma

Tribology International Vol. 178 2023.2

Language：English Publishing type：Research paper (scientific journal)

High-performance organic friction modifiers (OFMs) added to lubricating oils are crucial for reducing friction and wear under boundary lubrication. To guide the development of higher-performance OFMs, the boundary lubrication characteristics and working mechanisms of existing OFMs should be elucidated. In this study, the nanoscale frictional properties of conventional and recently developed TEMPO-based OFMs were measured using lateral force microscopy and interpreted using the Eyring activation energy model. We found that the parameters in this model provided insights into the characteristics of OFMs during loaded sliding, including the load-carrying capacity, adsorption speed, and shear-motion location. Therefore, analysis using the Eyring activation energy model effectively complements the LFM measurements and provides a new perspective for evaluating the boundary lubrication characteristics of OFMs beneficial for the development of high-performance OFMs.

DOI： 10.1016/j.triboint.2022.108052

Enhancing pressure consistency and transferability of structure-based coarse-graining Reviewed

Tang, JH; Kobayashi, T; Zhang, HD; Fukuzawa, K; Itoh, S

PHYSICAL CHEMISTRY CHEMICAL PHYSICS Vol. 25 ( 3 ) page： 2256 - 2264 2023.1

Language：English Publisher：Physical Chemistry Chemical Physics

Coarse-graining, which models molecules with coarse-grained (CG) beads, allows molecular dynamics simulations to be applied to systems with large length and time scales while preserving the essential molecular structure. However, CG models generally have insufficient representability and transferability. A commonly used method to resolve this problem is multi-state iterative Boltzmann inversion (MS-IBI) with pressure correction, which matches both the structural properties and pressures at different thermodynamic states between CG and all-atom (AA) simulations. Nevertheless, this method is usually effective only in a narrow pressure range. In this paper, we propose a modified CG scheme to overcome this limitation. We find that the fundamental reason for this limitation is that CG beads at close distances are ellipsoids rather than isotropically compressed spheres, as described in conventional CG models. Hence, we propose a method to compensate for such differences by slightly modifying the radial distribution functions (RDFs) derived from AA simulations and using the modified RDFs as references for pressure-corrected MS-IBI. We also propose a method to determine the initial non-bonded potential using both the target RDF and pressure. Using n-dodecane as a case study, we demonstrate that the CG model developed using our scheme reproduces the RDFs and pressures over a wide range of pressure states, including three reference low-pressure states and two test high-pressure states. The proposed scheme allows for accurate CG simulations of systems in which pressure or density varies with time and/or position.

DOI： 10.1039/d2cp04849c

Effect of Water on Mechanochemical Reactions of PFPE Lubricant Films: A Reactive Molecular Dynamics Study

PubMed

CHEN Xingyu, INAYOSHI Koya, ZHANG Hedong, FUKUZAWA Kenji, ITOH Shintaro, AZUMA Naoki

The Proceedings of the Conference on Information, Intelligence and Precision Equipment : IIP Vol. 2023 ( 0 ) page： IIPA-1-10 2023

Language：Japanese Publisher：The Japan Society of Mechanical Engineers

Using molecular dynamics with our developed reactive force field, we investigated the effect of water on the mechanochemical reaction of nanometer-thick perfluoropolyether D-4OH films at the head–disk interface of heat-assisted magnetic recording. Three types of reactions were observed: hydrolysis, end group–end group association (EEA) reaction, and end group–main chain association (EMA) reaction. The simulation results showed that water molecules accelerate the decomposition of D-4OH and such effect is more noticeable at low pressures than at high pressures. The presence of water induces hydrolysis and accelerates the EEA reaction, whereas the EMA reaction is greatly accelerated by pressure rather than water.

DOI： 10.1299/jsmeiip.2023.iipa-1-10

Elucidation of Correlation between Molecular Structure and Viscosity by Measuring Temperature Dependence of Dielectric Relaxation Spectra and Shear Viscosity

UCHIDA Kyosuke, ITOH Shintaro, FUKUZAWA Kenji, AZUMA Naoki, ZHANG Hedong

The Proceedings of the Conference on Information, Intelligence and Precision Equipment : IIP Vol. 2023 ( 0 ) page： IIPA-6-16 2023

Language：Japanese Publisher：The Japan Society of Mechanical Engineers

Reducing lubricant viscosity is one effective way to improve the energy efficiency of automobiles. Designing a lubricant with the desired properties requires elucidating the relation between viscosity and molecule structure. In this study, we measured the temperature dependence of dielectric relaxation for lubricants with different molecular structures. The dielectric relaxation measurements can evaluate the motility of single molecules influenced by the ambient viscosity. Additionally, we measured the temperature dependence of lubricant viscosity with a rotational viscometer. By comparing the results of both flow viscosity and dielectric relaxation measurements, we find a correlation between flow activation energy and single-molecule mobility when viscosity is dependent on molecular weight, while there is no correlation between them when polarity dominantly affects viscosity.

DOI： 10.1299/jsmeiip.2023.iipa-6-16

Estimation of surface slippage in nanogap based on flow velocity distributions obtained by nanoparticle image velocimetry

OZEKI Hidetaka, AZUMA Naoki, FUKUZAWA Kenji, ITOH Shintaro, ZHANG Hedong

The Proceedings of the Conference on Information, Intelligence and Precision Equipment : IIP Vol. 2023 ( 0 ) page： IIPA-6-5 2023

Language：Japanese Publisher：The Japan Society of Mechanical Engineers

With the development of microfabrication and surface treatment technologies, the gaps between elements in mechanical and electronic components have narrowed from the micrometer to the nanometer-sized. Fluid slippage at the solid/liquid interface is one of the phenomena that are considered to occur in micro/nanometer-sized gaps, and frictional properties there are expected to be different from those in macro gaps. For proper lubrication design in nanometer-sized gap, it is necessary to quantify the slippage at the interface. In this study, we used the fluorescence tracking of quantum dots with diameters of a few nanometers to measure the squeezed flow in nanometer-sized gap. Quantitative lateral velocity distributions were measured, and we estimated the slippage based on our proposed analysis of the number distribution of measured velocity values that depends on the flow profile in the depth direction. Our obtained results suggested that interfacial slippage occurred in the gap about less than 200 nm.

DOI： 10.1299/jsmeiip.2023.iipa-6-5

Development of a Temperature Control Stage for Nano Rheology Measurement Suppressing Positional Fluctuations Caused by Environmental Temperature Changes

NOZUE Takumi, ITOH Shintaro, FUKUZAWA Kenji, AZUMA Naoki, ZHANG Hedong

The Proceedings of the Conference on Information, Intelligence and Precision Equipment : IIP Vol. 2023 ( 0 ) page： IIPA-6-11 2023

Language：Japanese Publisher：The Japan Society of Mechanical Engineers

Polymer additives in lubrication oils are known to play a role as viscosity index improvers that change the temperature dependence of viscosity. On the other hand, it is assumed that polymers adsorbed on surfaces contribute to low friction, and clarification of their mechanical properties and temperature dependence is essential for lubrication design. In our previous research, we have successfully measured the gap dependence of mechanical properties (shear viscoelasticity) of base oils by applying the fiber wobbling method (FWM), a nano-rheological measurement method that we originally developed. In this study, we developed a temperature-control stage for FWM to measure the temperature dependence of shear viscoelasticity in nano-gaps of polymer-added lubricants.

DOI： 10.1299/jsmeiip.2023.iipa-6-11

Quantifying Shear Properties of Nano-Confined Liquids Using Vertical Objective Ellipsometric Microscopy

KATO Tsuyohi, FUKUZAWA Keji, AZUMA Noaki, Itoh Shintaro, ZHANG Hedong, NAKAGAWA Masaru, NAWATA Ryo, SEKI Junichi, ASANO Toshiya

The Proceedings of the Conference on Information, Intelligence and Precision Equipment : IIP Vol. 2023 ( 0 ) page： IIPA-6-15 2023

Language：Japanese Publisher：The Japan Society of Mechanical Engineers

To elucidate the cause of increase in shear resistance in alignment process for nano imprint lithography (NIL), by using vertical-objective-type ellipsometric microscopy (VEM) combined with a micro-cylinder structure and gap feedback-control, shear response of nano-confined liquid film mimicking a NIL resist film were measured. The three kinds of samples were prepared; monomer, monomer with release agent, and monomer with polymerization initiator. The increase in the shear resistance force was not detected with the monomer alone, but with the addition of additives. The shear response waveforms indicated that the resist solidifies at nanometer gaps and may melt above the yield shear force. These results suggest that the additive is unevenly distributed near the sliding solid surfaces and changes the physical properties of the monomer near the solid surfaces, resulting in a significant increase in shear resistance force at the nano gaps. This mechanism is thought to be responsible for the increased shear resistance force in the NIL alignment process as well.

DOI： 10.1299/jsmeiip.2023.iipa-6-15

Trimethylolpropane trioleate as eco-friendly lubricant additive Reviewed International coauthorship Open Access

Lee, CT; Lee, MB; Hamdan, SH; Chong, WWF; Chong, CT; Zhang, H; Chen, AWL

ENGINEERING SCIENCE AND TECHNOLOGY-AN INTERNATIONAL JOURNAL-JESTECH Vol. 35 page： 101068 2022.11

Language：English Publisher：Engineering Science and Technology, an International Journal

Approximately 17.9% of fuel energy is used to overcome engine friction in passenger cars with engine frictional losses further broken down into losses along hydrodynamic (40%), elastohydrodynamic – due to pure sliding motion (40%), mixed (10%) and boundary (10%) lubrication regimes. Therefore, to assess the tribological influence of TMP trioleate as an eco-friendly additive to a low viscosity Polyalphaolefin (PAO) at different lubrication regimes, the present study adopted a Stribeck-type analysis. Through this study, the viscosity index of PAO was found to increase significantly when blended with 5-vol% TMP trioleate. Tribologically, across the tested conditions at different sliding velocities and applied normal loads, it was determined that this blend could potentially reduce friction power and wear scar diameter by up to 6.09% and 39.65%, respectively, when compared with the neat PAO. Such an improvement was demonstrated to also synergistically enhance the friction modifier effect of this blend at the mixed lubrication regime, delaying the onset of boundary lubrication regime when the contact is lubricated by this mixture.

DOI： 10.1016/j.jestch.2021.09.014

Adsorption Behavior of TEMPO-Based Organic Friction Modifiers during Sliding between Iron Oxide Surfaces: A Molecular Dynamics Study Reviewed

水和ポリマーブラシ膜のせん断すき間に依存した動的ずり粘弾性

林楓昌，伊藤伸太郎，福澤健二，東直輝，張賀東

トライボロジー会議2022 春東京　予稿集 2022.5

ポリアルキルメタクリレート添加潤滑油のナノすき間におけるずり粘弾性の温度依存性

野末拓海，伊藤伸太郎，大久保尚哉，福澤健二，東直輝，張賀東

トライボロジー会議2022 春東京　予稿集 2022.5

Effects of polarity of polyalkylmethacrylate (PAMA) polymer additives on adsorbed film’s thickness and durability

Song Yuxi, Kenji Fukuzawa, Tomoko Hirayama, Shintaro Itoh, Hedong Zhang, Naoki Azuma

トライボロジー会議2022 春東京　予稿集 2022.5

フラーレン添加潤滑油の境界潤滑特性における基材性状依存性の解明

伊藤伸太郎，エン子昂，福澤健二，東直輝，張賀東

トライボロジー会議2022 春東京　予稿集 2022.5

TEMPO系有機摩擦調整剤の酸化鉄表面への吸着挙動に関する分子動力学解析

陳星宇，楊俊韜，安田耕二，古賀伸明，張賀東

トライボロジー会議2022 春東京　予稿集 2022.5

Xingyu Chen, Juntao Yang, Koji Yasuda, Nobuaki Koga, Hedong Zhang

Langmuir Vol. 38 ( 10 ) page： 3170 - 3179 2022.3

In-situ measurement of temporal changes in thickness of polymer adsorbed films from lubricant oil by vertical-objective-based ellipsometric microscopy Reviewed

Yuxi Song, Kenji Fukuzawa, Shintaro Itoh, Hedong Zhang, Naoki Azuma

Tribology International Vol. 165 page： 107341 - 107341 2022.1

Observing squeeze flow in nanometer-sized gap using fluorescent images of quantum dots

AZUMA Naoki, MIKI Katsuki, FUKUZAWA Kenji, ITOH Shintaro, ZHANG Hedong

The Proceedings of the Conference on Information, Intelligence and Precision Equipment : IIP Vol. 2022 ( 0 ) page： IIP2R3-H12 2022

Language：Japanese Publisher：The Japan Society of Mechanical Engineers

With the development of microfabrication and surface processing technologies, gap between two solid surfaces in Micro electro mechanical systems (MEMS) and Micro total analysis system (μTAS) becomes microgap to nanogap. For designing the devices and verifying the principle of MEMS and μTAS, experimental method to measure flow distribution of fluid confined in nanogap is required. In this study, we aim to realize the measurement of the flow distribution of squeezed flow in the nanogap using fluorescence images of nanoparticles. We evaluated the validity of our experimental method by comparing our experimental results with the theoretical results and clarified the size of nanogap that can be measured using our method.

DOI： 10.1299/jsmeiip.2022.iip2r3-h12

Simultaneous Measurement of Shear Viscoelasticity and Dielectric Relaxation of Lubricant Oil Sheared in Nanometer-sized Gaps

KATSUNO Shotaro, ITOH Shintaro, FUKUZAWA Kenji, AZUMA Naoki, ZHANG Hedong

The Proceedings of the Conference on Information, Intelligence and Precision Equipment : IIP Vol. 2022 ( 0 ) page： IIP2R3-H11 2022

Thickness control method of liquid films with nanometer resolution using molecular interaction between solid and liquid

Saitoh Yuki, Fukuzawa Kenji, Itoh Shintaro, Azuma Naoki, Zhang Hedong

The Proceedings of the Conference on Information, Intelligence and Precision Equipment : IIP Vol. 2022 ( 0 ) page： IIP2R3-H05 2022

Language：Japanese Publisher：The Japan Society of Mechanical Engineers

Thickness control of thin liquid films is useful in various fields for the control of physical properties of solid surfaces such as wettability and multilayer fabrication using light-curing resin liquid films. In this report, we propose a precise thickness control method with nanometer-order resolution using intermolecular interaction between solid and liquid, and report its experimental verification.

DOI： 10.1299/jsmeiip.2022.iip2r3-h05

Molecular Dynamics Study of Mechanochemical Reactions of PFPE Lubricant Films in the Presence of Water and Oxygen

INAYOSHI Koya, AOTO Takumi, CHEN Xingyu, ZHANG Hedong, FUKUZAWA Kenji, ITOH Shintaro, AZUMA Naoki

The Proceedings of the Conference on Information, Intelligence and Precision Equipment : IIP Vol. 2022 ( 0 ) page： IIP2R1-A06 2022

Language：Japanese Publisher：The Japan Society of Mechanical Engineers

Using molecular dynamics with our developed reactive force field, we investigated the effect of water and/or oxygen on the mechanochemical reaction of nanometer-thick perfluoropolyether D-4OH films at the head–disk interface of heat-assisted magnetic recording. The simulation results showed that the presence of oxygen, water, or both accelerated the mechanochemical reaction of D-4OH. For oxygen only, no decomposition reaction occurred, and oxidation reactions were observed in which an oxygen molecule was inserted between the C–C bond in the end group of D-4OH. In contrast, in the presence of water, hydrolysis decomposition reactions at the C–O bond in the end group of D-4OH occurred frequently, and polymerization reactions were also observed.

DOI： 10.1299/jsmeiip.2022.iip2r1-a06

Coarse-Grained Molecular Dynamics Study of Lubrication Properties of Nanometer-Thick Liquid Films Invited Reviewed

ZHANG Hedong, KOBAYASHI Takayuki

JOURNAL OF JAPANESE SOCIETY OF TRIBOLOGISTS Vol. 66 ( 4 ) page： 294 - 299 2021.4

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japanese Society of Tribologists

The establishment of effective lubrication with nanometer-thick liquid films is crucial for the development of advanced miniaturized mechanical systems. Complementary to experiments, molecular dynamics (MD) simulations provide atomic-level insights into the structure and movement of nanometer-thick liquid films. However, conventional all-atom MD simulations are computationally expensive for studying systems over extended length and time scales. Coarse graining, which eliminates some degrees of freedom by grouping several atoms to one bead, is one effective method to reduce computational cost. In this review, the procedure of coarse graining and some points to note for accurate modeling of lubrication phenomena are presented through a concrete example of coarse-grained MD simulations of confined shear of nanometer-thick polar liquid lubricant films at the head-disk interface of magnetic disk drives.

DOI： 10.18914/tribologist.66.04_294

Measurement of squeeze flow in micrometer-sized gap using single molecule tracking of quantum dot

MIKI Katsuki, AZUMA Naoki, FUKUZAWA Kenji, ITOH Shintaro, ZHANG Hedong

The Proceedings of the Conference on Information, Intelligence and Precision Equipment : IIP Vol. 2021 ( 0 ) page： IIP1B1-3 2021

Language：Japanese Publisher：The Japan Society of Mechanical Engineers

The lubrication phenomena of lubricants confined in a nanometer-sized gap are different from those in the bulk state. Clarifying the mechanism of them requires the method to measure the lubricant flow in the nanometer-sized gap. Therefore, we proposed the method to measure the lubricant flow using single molecule tracking of quantum dots with the fluorescence microscope. A single quantum dot has the diameter of several tens of nm and can be applied to measure the lubricant flow in nanometer-sized gap. In this study, we tried to measure the squeeze flow of lubricants in micrometer-sized gap to verify the validity of our proposed method. Our obtained velocities of the squeeze flow were good agreement with those of theoretical model, that indicated the validity of our method.

DOI： 10.1299/jsmeiip.2021.iip1b1-3

Simultaneous Measurement of Viscoelasticity and Film Thickness during Shearing of Patterned Hydrated Polymer Brush Film

LIN Fengchang, ITOH Shintaro, FUKUZAWA Kenji, ZHANG Hedong, AZUMA Naoki

The Proceedings of the Conference on Information, Intelligence and Precision Equipment : IIP Vol. 2021 ( 0 ) page： IIP1B1-4 2021

Language：Japanese Publisher：The Japan Society of Mechanical Engineers

2-methacryloyloxyethyl phosphorylcholine (MPC) polymer is a promising coating material for extending the useful life of artificial joints due to its biocompatibility and lubricity. Especially, the hydrated brush-like MPC polymer film showed a low coefficient of friction. However, the mechanism of the lubricity is not fully understood. Friction coefficients of the MPC polymer films showed dependency on the shear gap, which must be caused by the thickness dependence of the film's mechanical properties (viscoelasticity). However, due to the thin film thickness (around 100 nm), it was difficult to measure the viscoelasticity. Thus, this research aimed to measure the hydrated MPC polymer brush film's viscoelasticity and elucidate its gap dependency. We established a measurement method that realizes simultaneous measurement of shear viscoelasticity and film thickness.

DOI： 10.1299/jsmeiip.2021.iip1b1-4

Measurement of Surface Adsorption Characteristics to Elucidate the Action Mechanism of Organic Friction Modifiers in Lubricating Oil

KUZUYA Kohei, ZHANG Hedong, FUKUZAWA Kenji, ITOH Shintaro, AZUMA Naoki, HOR Seanghai, TSUKAMOTO Masaki

The Proceedings of the Conference on Information, Intelligence and Precision Equipment : IIP Vol. 2021 ( 0 ) page： IIP1B1-2 2021

Language：Japanese Publisher：The Japan Society of Mechanical Engineers

High performance environment-friendly organic friction modifier (OFM) additives are crucial for reducing energy loss and greenhouse gases due to friction and wear. In this study, we designed and synthesized a new type of TEMPO-based OFMs which contain a cyclic structure and free radical. In addition to friction and wear measurements, surface adsorption characteristics of the OFMs were measured with quartz crystal microbalance (QCM). We confirmed that Amide-TEMPO exhibits better friction and wear reduction effect than the conventional glyceryl monooleate. The friction coefficient correlated negatively with the adsorption equilibrium constant, but it showed no correlation with the adsorption density. The anti-wear performance showed no correlation with both adsorption equilibrium constant and adsorption density, suggesting that it is difficult to interpret the wear characteristics simply from the static adsorption characteristics measured by QCM.

DOI： 10.1299/jsmeiip.2021.iip1b1-2

Reactive Molecular Dynamics Study of Effect of Water and Oxygen Molecules on Decomposition of PFPE Lubricant Films in Heat-Assisted Magnetic Recording

AOTO Takumi, CHEN Xingyu, ZHANG Hedong, FUKUZAWA Kenji, ITOH Shintaro, AZUMA Naoki

The Proceedings of the Conference on Information, Intelligence and Precision Equipment : IIP Vol. 2021 ( 0 ) page： IIP2A3-3 2021

Language：Japanese Publisher：The Japan Society of Mechanical Engineers

To realize heat-assisted magnetic recording (HAMR), which can largely increase the recording density of hard disk drives, it is crucial to ensure the reliability and durability of the head disk interface (HDI) that involves high temperature and high-speed shear. In this study, we performed reactive molecular dynamics simulations to clarify the effects of water and oxygen molecules on the decomposition of nanometer-thick perfluoropolyether D-4OH films that lubricate the HDI of HAMR. From the simulation results, we found that water molecules accelerate the decomposition of D-4OH and this effect is suppressed by the presence of oxygen molecules. We also found that high normal pressures and concentrations of water and oxygen molecules lead to fast decomposition of D-4OH molecules.

DOI： 10.1299/jsmeiip.2021.iip2a3-3

ReaxFF Reactive Molecular Dynamics Simulations of Mechano-chemical Decomposition of Perfluoropolyether Lubricants in Heat-assisted Magnetic Recording Reviewed Open Access

X. Chen, K. Kawai, H. Zhang, K. Fukuzawa, N. Koga, S. Itoh, N. Azuma

Journal of Physical Chemistry C Vol. 124 page： 22496–22505 2020.9

Effect of Transverse Dissipative Particle Dynamics on Dynamic Properties of Nanometer-thick Liquid Films on Solid Surfaces Reviewed Open Access

T. Kobayashi, H. Zhang, K. Fukuzawa, S. Itoh

Molecular Simulation Vol. 146 page： 1281–1290 2020.9

Experimental Study of Application of Molecules with a Cyclic Head Group Containing a Free Radical as Organic Friction Modifiers Reviewed Open Access

X. Zhang, M. Tsukamoto, H. Zhang, Y. Mitsuya, S. Itoh, K. Fukuzawa

Journal of Advanced Mechanical Design, Systems, and Manufacturing Vol. 14 page： JAMDSM0044 2020.4

Extension of Measurement Range of Lubrication Gap Shape using Vertical-Objective-Type Ellipsometric Microscopy with Two Compensator Angles Reviewed

K. Namba, K. Fukuzawa, S. Itoh, H. Zhang, N. Azuma

Tribology International Vol. 142 page： 105980 2020.2

Frictional Behaviour of Trimethylolpropane (TMP) Oleate at Different Regimes of Lubrication Reviewed

A.F. Maarof, S.H. Hamdan, C.T. Lee, W.W.F. Chong, C.T. Chong, H. Zhang

Journal of Mechanical Engineering Vol. 8 page： 1-9 2019.12

Validation of Correction Method for Gap Shape Measurement by Vertical-Objective-Type Ellipsometric Microscopy with Rotating-Compensator Ellipsometry Reviewed Open Access

K. Namba, Y. Sasao, K. Fukuzawa, S. Itoh, H. Zhang

Journal of Advanced Mechanical Design, Systems, and Manufacturing Vol. 13 ( 2 ) page： 18-00434 2019.4

Nano-tribological Characterisation of Palm Oil-based Trimethylolpropane Ester for Application as Boundary Lubricant Reviewed

S.H. Hamdan, W.W.F. Chong, J.-H. Ng, C.T. Chong, H. Zhang

Tribology International Vol. 127 page： 1-9 2018.11

Simultaneous in situ Measurements of Contact Behavior and Friction to Understand the Mechanism of Lubrication with Nanometer-thick Liquid Lubricant Films Reviewed

H. Zhang, Y. Takeuchi, W.W.F. Chong, Y. Mitsuya, K. Fukuzawa, S. Itoh

Tribology International Vol. 127 page： 138-146 2018.11

Measurement of Nanometer-thick Lubricating Films using Ellipsometric Microscopy Reviewed Open Access

K. Fukuzawa, Y. Sasao, K. Namba, C. Yamashita, S. Itoh, H. Zhang

Tribology International Vol. 122 page： 8-14 2018.6

Enhanced Viscoelasticity of Polyalphaolefins Confined and Sheared in Submicron-to-nanometer-sized Gap Range and Its Dependence on Shear Rate and Temperature Reviewed

S. Itoh, Y. Ohta, K. Fukuzawa, H. Zhang

Tribology International Vol. 120 page： 210-217 2018.4

Is the Trend of Stribeck Curves Followed by Nano-Lubrication with Molecularly Thin Liquid Lubricant Films? Reviewed

Hedong Zhang, Takahiro Yoshimi, Kenji Fukuzawa, Shintaro Itoh

Tribology International Vol. 119 page： 82-87 2018.3

Separation of Large DNA Molecules by Applying Pulsed Electric Field to Size Exclusion Chromatography-based Microchip Reviewed

Naoki Azuma, Shintaro Itoh, Kenji Fukuzawa, Hedong Zhang

Japanese Journal of Applied Physics Vol. 27 ( 027002 ) 2018.1

Real-time Observation of Molecularly Thin Lubricant Films on Head Sliders Using Rotating-Compensator-Based Ellipsometric Microscopy Reviewed Open Access

Kenji Fukuzawa, Ken Miyata, Chihiro Yamashita, Shintaro Itoh, Hedong Zhang

IEEE Transactions on Magnetics Vol. 53 ( 11 ) page： 1-4 2017.11

Optimization of Applied Voltages for On-chip Concentration of DNA Using Nanoslit Reviewed

Naoki Azuma, Shintaro Itoh, Kenji Fukuzawa, Hedong Zhang

Japanese Journal of Applied Physics Vol. 56 ( 127001 ) 2017.11

Measurement of Viscoelasticity of UV photoresist used for nanoimprint lithography under confinement in nanometer-sized gaps Reviewed

Shintaro Itoh, Kazuhiro Takahashi, Kenji Fukuzawa, Hedong Zhang

Japanese Journal of Applied Physics page： 56, 06GL02 2017.5

Measurement of Thickness Distribution of Molecularly Thin Lubricant Films on Head Sliders Using Ellipsometric Microscopy Reviewed

Kenji Fukuzawa, Chihiro Yamashita, Hiorya Ishikawa, Shintaro Itoh, Hedong Zhang

IEEE Transactions on Magnetics 2016.7

Molecular Dynamics Simulations of Diffusion of Submonolayer Polar Liquid Lubricant Films on Solid Surfaces Reviewed

Takayuki Kobayashi, Hedong Zhang, Kenji Fukuzawa, Shintaro Itoh

Microsystem Technologies Vol. 22 ( 6 ) page： 1285-1290 2016.6

Atmospheric Vapor Phase Deposition of Nanometer-thick Anti-stiction Fluoropolymer Coatings for Silicon Surfaces Reviewed

Shintaro Itoh, Kazuhiro Takahashi, Hiroyuki Morita, Kenji Fukuzawa, Hedong Zhang

Japanese Journal of Applied Physics Vol. 55 ( 06GP10 ) page： 5 pages 2016.5

Design Principle of Micro-Mechanical Probe for Lateral-Deflection-Controlled Friction Force Microscopy Reviewed

Kenji Fukuzawa, Satoshi Hamaoka, Mitsuhiro Shikida, Shintaro Itoh, Hedong Zhang

Microsystem Technologies Vol. 22 page： 1181-1188 2016.5

Separation of Large DNA Molecules by Size Exclusion Chromatography-based Microchip with On-chip Concentration Structure Reviewed

Naoki Azuma, Shintaro Itoh, Kenji Fukuzawa, Hedong Zhang

Japanese Journal of Applied Physics Vol. 55 ( 06GN01 ) page： 8 pages 2016.4

Shear Thinning Behavior of Nanometer-thick Perfluoropolyether Films Confined between Corrugated Solid Surfaces: A Coarse-grained Molecular Dynamics Study Reviewed

Hedong Zhang, Motoo Fukuda, Hitoshi Washizu, Tomoyuki Kinjo, Hiroaki Yoshida, Kenji Fukuzawa, Shintaro Itoh

Tribology International Vol. 93 page： 163-171 2016.1

Effect of Bonded Molecules on Replenishment of Lubricant-Depleted Area Created by Sliding on Molecularly Thin Lubricant Film Reviewed

Kenji Fukuzawa, Ryota Watanabe, Shintaro Itoh, Hedong Zhang

IEEE Transactions on Magnetics Vol. 51 ( 11 ) page： 1-4 2015.11

Coarse-Grained Molecular Dynamics Simulation of Nanometer-Thick Polar Lubricant Films Sheared Between Solid Surfaces with Random Roughness Reviewed

Takayuki Kobayashi, Hedong Zhang, Kenji Fukuzawa, Shintaro Itoh

IEEE Transactions on Magnetics Vol. 51 ( 11 ) page： 3300704 (4 pages) 2015.11

Anisotropic shear viscosity of photoaligned liquid crystal confined in sub-micron-to-nanometer-scale gap widths revealed with simultaneously measured molecular orientation Reviewed

Shintaro Itoh, Yuuichi Imura, Kenji Fukuzawa, Hedong Zhang

Langmuir 2015.9

Effect of Chemically Adsorbed Molecules on the Viscous Friction of Nanometer-Thick Liquid Lubricant Films Coated on a Diamond-Like Carbon Surface Reviewed

Shintaro Itoh, Yusuke Norizuki, Kenji Fukuzawa, Hedong Zhang

Tribology Letters Vol. 60 2015.9

ボールオンディスク試験用の高速しゅう動子アセンブリの開発と分子潤滑膜の速度依存摩擦特性の測定 Reviewed Open Access

三矢保永，張賀東，難波克也，福澤健二，伊藤伸太郎

トライボロジスト Vol. 60 ( 2 ) page： 144-152 2015.2

粗視化分子動力学シミュレーションを用いたナノ厚さ液体潤滑膜の凝着特性解析 Reviewed Open Access

張　賀東

分子シミュレーション研究会会誌　アンサンブル Vol. 17 ( 1 ) page： 24-29 2015.1

ナノ厚さ液体潤滑膜の微細テクスチャリングによる新規なトライボ表面の創成 Reviewed

張　賀東

潤滑経済 Vol. 595 page： 2-7 2014.12

Development of a Ball-Suspension Assembly for Measuring Speed-Dependent Friction Characteristics of Thin Lubricant Films Coated on Magnetic Disks Reviewed

Yasunaga Mitsuya, Hedong Zhang, Katsuya Namba, Kenji Fukuzawa, Shintaro Itoh

IEEE Transactions on Magnetics Vol. 50 ( 11 ) page： 3302704 (4 pages) 2014.11

Surface Functionalization by Fine Ultraviolet-Patterning of Nanometer-Thick Liquid Lubricant Films Reviewed

Renguo Lu, Hedong Zhang, Suguru Komada, Yasunaga Mitsuya, Kenji Fukuzawa, Shintaro Itoh

Applied Surface Science Vol. 320 page： 102-111 2014.11

Influence of Surface Roughness and Coating on the Friction Properties of Nanometer-thick Liquid Lubricant Films Reviewed

Renguo Lu, Hedong Zhang, Yasunaga Mitsuya, Kenji Fukuzawa, Shintaro Itoh

Vol. 139 ( 1-2 ) page： 56-61 2014.11

Lateral-Deflection-Controlled Friction Force Microscopy Reviewed

Kenji Fukuzawa, Satoshi Hamaoka, Mitsuhiro Shikida, Shintaro Itoh, Hedong Zhang

Journal of Applied Physics Vol. 116 page： 084311(6pages) 2014.8

Shear thinning of nanometer-thick liquid lubricant films measured at high shear rates Reviewed

Shintaro Itoh, Koki Ishii, Kenji Fukuzawa, Hedong Zhang

Tribology Letters Vol. 53 page： 555-567 2014.1

Contributions of Mobile and Bonded Molecules to Dynamic Friction of Nanometer-Thick Perfluoropolyether Films Coated on Magnetic Disk Surfaces Reviewed

Renguo Lu, Hedong Zhang, Yasunaga Mitsuya, Kenji Fukuzawa, Shintaro Itoh

Tribology Letters 2013.10

Adhesion Properties of Nanometer-thick Perfluoropolyether Films Confined between Solid Surfaces: A Coarse-grained Molecular Dynamics Study Reviewed

Motoo Fukuda, Hedong Zhang, Takahiro Ishiguro, Kenji Fukuzawa, Shintaro Itoh

Tribology Letters Vol. 51 ( 3 ) page： 479-487 2013.9

Design Principle of Micromechanical Probe with an Electrostatic Actuator for Friction Force Microscopy Reviewed

Kenji Fukuzawa, Hiroaki Tsuji, Satoshi Hamaoka, Mitsuhiro Shikida, Shintaro Itoh, Hedong Zhang

Microsystems Technologies Vol. 19 ( 9-10 ) page： 1567-1572 2013.9

Ultraviolet Bonding of Perfluoropolyethers to Carbon Surfaces Investigated using Quantum Chemical Methods Reviewed

Md. Khorshed Alam, Hedong Zhang, Nobuaki Koga, Satoru Iuchi

Microsystems Technologies Vol. 19 ( 9-10 ) page： 1383-1391 2013.9

Friction Measurements of Nanometer-thick Lubricant Films Using Ultra-smooth Sliding Pins Treated with Gas Cluster Ion Beam Reviewed

Renguo Lu, Hedong Zhang, Yasunaga Mitsuya, Kenji Fukuzawa, Shintaro Itoh

Applied Surface Science Vol. 280 page： 619-625 2013.9

Structure-based Coarse-graining for Inhomogeneous Liquid Polymer Systems Reviewed

Motoo Fukuda, Hedong Zhang, Takahiro Ishiguro, Kenji Fukuzawa, Shintaro Itoh

Journal of Chemical Physics Vol. 139 ( 5 ) page： 054901-1-11 2013.8

Theoretical and Experimental Study on Two-stage-imaging Microscopy Using Ellipsometric Contrast for Real-time Visualization of Molecularly Thin Films Reviewed

Yosuke Kajihara, Kenji Fukuzawa,Shintaro Itoh, Ryouta Watanabe, Hedong Zhang

Review of Scientific Instruments Vol. 84 page： 053704-1-9 2013.5

Detection of Asperity Contact for Precise Gap Determination in Thin-Film Nanorheometry Reviewed

Shintaro Itoh, Yuya Hamamoto, Koki Ishii, Kenji Fukuzawa, and Hedong Zhang

Tribology Letters Vol. 49 page： 1-10 2013.1

Measured Viscous and Dry Friction Forces in Nanometer-Thick Lubricant Film by Friction Force Microscopy with Micromechanical Probe Reviewed

Kenji Fukuzawa, Hiroaki Tsuji, Satoshi Hamaoka, Mitsuhiro Shikida, Shintaro Itoh, and Hedong Zhang

Tribology Letters ( 48 ) page： 201-208 2012.9

ナノ厚さ液体膜のパターニングによる機能性潤滑表面の創成 Reviewed

張　賀東

トライボロジスト Vol. 57 ( 8 ) page： 522-527 2012.8

An electrostatic actuator for dual-axis micro-mechanical probe on friction force microscope Reviewed

Hiroaki Amakawa, Kenji Fukuzawa, Mitsuhiro Shikida, Hiroaki Tsuji, Hedong Zhang, Shintaro Itoh

Sensors & Actuators: A. Physical Vol. 175 page： 94-100 2012.3

ガスクラスタイオンビーム加工によるガラス面の表面粗さおよび表面エネルギーの変化 Invited Reviewed

張賀東，三矢保永，難波克也，榊原寛幸，福澤健二，伊藤伸太郎

トライボロジスト Vol. 57 ( 2 ) page： 116-122 2012.2

Real-time Visualization of a Shearing Nanometer-thick Lubricant Film by Two-stage Imaging Ellipsometric Microscopy Reviewed

Y. Kajihara, K. Fukuzawa, S. Itoh, H. Zhang

IEEE Transactions on Magnetics Vol. 47 ( 10 ) page： 3441-3444 2011.10

A New Method for Measuring Normal Forces with Accurate Gap Control Using a Microfabricated Quartz Resonator for Lubrication at Nanometer Gaps Reviewed

K. Fukuzawa, Y. Yamauchi, Y Naito, S. Itoh, H. Zhang

Tribology Letters 2011.6

Effect of Ultraviolet Irradiation on Adhesion of Nanometer-Thick Lubricant Films Coated on Magnetic Disk Surfaces Reviewed

Hedong Zhang, Taiki Takimoto, Kenji Fukuzawa, Shintaro Itoh

IEEE Transactions on Magnetics Vol. 47 ( 1 ) page： 94-99 2011.1

Shear thinning behavior of monolayer liquid lubricant films measured by fiber wobbling method Reviewed Open Access

Y. Hamamoto, S. Itoh, K. Fukuzawa, H. Zhang

Journal of Physics: Conference Series Vol. 258 ( 012010 ) page： 1-10 2010.12

光ファイバープローブを用いた単分子厚さの液体潤滑薄膜の動的粘弾性計測 Reviewed Open Access

浜本祐也，伊藤伸太郎，福澤健二，張賀東

日本機械学会論文集(C編) Vol. 76 ( 767 ) page： 1716-1727 2010.7

Quantification of Friction Force on Dual-Axis Micro-Mechanical Probe for Friction Force Microscopy Reviewed

H. Amakawa, K. Fukuzawa, M. Shikida, H. Zhang, S. Itoh

Tribology Online Vol. 5 ( 3 ) page： 144-149 2010.7

紫外線照射によるナノ液体潤滑膜のパターニングに関する粗視化分子動力学シミュレーション Reviewed Open Access

張賀東，小松新始，福澤健二，伊藤伸太郎

日本機械学会論文集(C編) Vol. 76 ( 767 ) page： 1819-1826 2010.7

Simultaneously Measuring Lateral And Vertical Forces with Accurate Gap Control for Clarifying Lubrication Phenomena at Nanometer Gap Reviewed

K. Fukuzawa, K. Hayakawa, N. Matsumura, S. Itoh, H. Zhang

Tribology Letters Vol. 37 ( 3 ) page： 497-505 2010.3

ナノすきま潤滑現象解明のための高精度すきま制御型垂直力・剪断力同時計測法 Reviewed Open Access

福澤健二，早川康精，松村憲樹，伊藤伸太郎，張賀東

日本機械学会論文集(C編) Vol. 76 ( 763 ) page： 717-726 2010.3

Displacement measurement for high speed tribological measurement using oscillating optical fiber probe Reviewed Open Access

S. Itoh, K. Imai, K. Fukuzawa, Y. Hamamoto, H. Zhang

Journal of Advanced Mechanical Design, Systems, and Manufacturing Vol. 4 ( 1 ) page： 2-14 2010.2

Speading Properties of Monolayer Lubricant Films: Effect of Bonded Molecules Reviewed

S. Itoh, K. Takahashi, K. Fukuzawa, H. Amakawa, H. Zhang

IEEE Transactions on Magnetics Vol. 45 ( 11 ) page： 5055-5060 2009.11

Solvent Effects on Friction Properties of Monolayer Perfluoropolyether Films Coated on Magnetic Disk Surfaces Reviewed Open Access

H. Zhang, Y. Mitsuya, Y. Fujikawa, A. Fuwa, K. Fukuzawa

IEEE Transactions on Magnetics Vol. 45 ( 10 ) page： 3632-3635 2009.10

磁気ディスク表面における単分子層潤滑膜の摩擦特性に及ぼす溶媒の効果 Reviewed

張賀東，三矢保永，藤川陽介，不破暁，福澤健二

トライボロジスト Vol. 54 ( 9 ) page： 616-623 2009.9

紫外線照射を利用したナノ潤滑膜の特性制御 Reviewed

三矢　保永，張　賀東

トライボロジスト Vol. 54 ( 3 ) page： 154-159 2009.3

磁気ディスク表面単分子層潤滑膜における流動分子と固定分子の摩擦特性 Reviewed Open Access

張賀東，三矢保永，不破暁，藤川陽介，福澤健二

日本機械学会論文集(C編) Vol. 75 ( 749 ) page： 178-183 2009.1

Improved Sensitivity of Dual-Axis Micro-Mechanical Probe for Friction Force Microscope Reviewed

H. Amakawa, K. Fukuzawa, M. Shikida, H. Zhang, S. Itoh

Tribology Online Vol. 3 ( 7 ) page： 356-360 2008.12

Nonuniform Distribution of Molecularly Thin Lubricant Caused by Inhomogeneous Buried Layers of Discrete Track Media Reviewed Open Access

K. Fukuzawa, T. Muramatsu, H. Amakawa, S. Itoh, H. Zhang

IEEE Transactions on Magnetics Vol. 44 ( 11 ) page： 3663-3666 2008.11

Experimental Comparisons of Spreading and Replenishment Flows of Molecularly Thin Lubricant Films Coated on Magnetic Disks Reviewed

Y. Mitsuya, H. Zhang, J. Ohgi, K. Fukuzawa

IEEE Transactions on Magnetics Vol. 44 ( 11 ) page： 3641-3644 2008.11

*Effect of Thermal Bonding on Frictional Properties of Monolayer Lubricant Films Coated on Magnetic Disk Surfaces Reviewed

H. Zhang, Y. Mitsuya, A. Fuwa, Y. Fujikawa, K. Fukuzawa

IEEE Transactions on Magnetics Vol. 44 ( 11 ) page： 3637-3640 2008.11

Motion Picture Imaging of a Nanometer-thick Liquid Film Dewetting by Ellipsometric Microscopy with a Sub-μm Lateral Resolution Reviewed

K. Fukuzawa, T. Yoshida, S. Itoh, H. Zhang

Langmuir Vol. 24 ( 20 ) page： 11645-11650 2008.9

Fiber wobbling method for dynamic viscoelastic measurement of liquid lubricant confined in molecularly narrow gaps Reviewed

S. Itoh, K. Fukuzawa, Y. Hamamoto, H. Zhang, Y. Mitsuya

Tribology Letters Vol. 30 page： 177-189 2008.6

ナノ閉じ込めされた液体潤滑剤の粘弾性特性の周波数依存性 Reviewed Open Access

伊藤伸太郎，福澤健二，浜本祐也，張賀東

日本機械学会論文集（C編） Vol. 74 ( 740 ) page： 961-969 2008.4

*Quantification of the Surface Morphology of Lubricant Films With Polar End Groups Using Molecular Dynamics Simulation: Periodic Changes in Morphology Depending on Film Thickness Reviewed

S. Ogata, H. Zhang, K. Fukuzawa, Y. Mitsuya

ASME Journal of Tribology Vol. 130 page： 022301-1-9 2008.4

磁気ディスク表面における分子潤滑膜に及ぼす紫外線照射の効果（分子末端基の影響） Reviewed Open Access

張賀東，三矢保永，工藤由貴，福澤健二

日本機械学会論文集（C編） Vol. 74 ( 740 ) page： 970-977 2008.4

Control of Wettability of Molecularly Thin Liquid Films by Nanostructures Reviewed

K. Fukuzawa, T. Deguchi, Y. Yamawaki, S. Itoh, T. Muramatsu, H. Zhang

Langmuir Vol. 24 page： 2921-2928 2008.2

Fly Height Measurement Based on Phase Comparison Michelson Interferometry Using Low-Coherence Light Source Reviewed

Y. He, H. Zhang, K. Fukuzawa, Y. Mitsuya

IEEE Transaction on Magnectics Vol. 44 ( 2 ) page： 309-314 2008.2

磁気ディスク表面における潤滑剤分子の配列構造の形成に伴う摩擦特性の変化 Reviewed Open Access

張賀東，三矢保永，藤川陽介，不破暁，賀銀波，福澤健二

日本機械学会論文集(C編) Vol. 74 ( 737 ) page： 162-168 2008.1

表面ナノ構造による液体潤滑薄膜のぬれ性の制御 Reviewed

福澤健二，村松拓郎，出口貴則，山脇靖広，張賀東，伊藤伸太郎

トライボロジスト Vol. 53 ( 1 ) page： 50-57 2008.1

Changes in Friction Properties of Monolayer Lubricant Films Induced by Development of Molecules' Bonding Reviewed

H. Zhang, Y. Mitsuya, Y. Fujikawa, A. Fuwa, Y. He, K. Fukuzawa

Tribology Letters Vol. 28 ( 2 ) page： 163-170 2007.11

Stiffness and Damping of Thin PFPE Lubricant Bridging Between Magnetic Disk and Diamond Probe Tip Reviewed

Y. Mitsuya, Y. Ohshima, H. Zhang, K. Aoyama, T. Kawai, K. Fukuzawa

ASME Journal of Tribology Vol. 129 ( 4 ) page： 720-728 2007.10

*Direct visualization of molecularly thin lubricant films using low-coherence phase-shifting interferometry Invited Reviewed

H. Zhang, T. Banno, Y. Mitsuya, K. Fukuzawa

IEEE Transaction on Magnectics Vol. 43 ( 9 ) page： 3699-3704 2007.9

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

We have developed a method utilizing low-coherence phase-shifting interferometry (LCPSI) to directly visualize molecularly thin lubricant films coated on diamond-like carbon (DLC) surfaces. The measurement accuracy is guaranteed by the use of a low-coherence light source, a feedback-controlled phase-shifting system, and an image subtraction method. By measuring nanometer-thick perfluoropolyether films coated on DLC surfaces, we demonstrated that the LCPSI is capable of providing real-time three-dimensional measurements at a sub-nanometer thickness resolution and a spatial resolution of several micrometers.

DOI： 10.1109/TMAG.2007.902973

Evaluations of tribological characteristics of PFPE lubricants on DLC surfaces of magnetic disks Reviewed

Yinbo He, Yosuke Fujikawa, Hedong Zhang, Kenji Fukuzawa, Yasunaga Mitsuya

Tribology Letters Vol. 27 ( 1 ) page： 1-11 2007.7

低コヒーレンス位相シフト干渉法を用いたナノ潤滑膜の三次元画像計測 Reviewed Open Access

張賀東，三矢保永，坂野貴裕，福澤健二

日本機械学会論文集(C編) Vol. 73 ( 730 ) page： 1862-1868 2007.6

Evaluation of spreading characteristics of monolayer lubricant films on magnetic disks using molecular dynamics simulation Reviewed

Y. Tagaya, K. Fukuzawa, H. Zhang, Y. Mitsuya

IEEE Transaction on Magnectics Vol. 43 ( 6 ) page： 2229-2231 2007.6

Head-disk spacing measurement based on Michelson interferometry using white light illumination Reviewed

Yinbo He, Hedong Zhang, Yasunaga Mitsuya, Kenji Fukuzawa

Microsystem Technologies Vol. 13 ( 7 ) page： 647-655 2007.4

回折シミュレーションに基づく溝状テクスチャ付き表面における分子潤滑膜の表面流動特性の測定 Reviewed Open Access

張賀東，三矢保永，山田麻衣子，福澤健二

日本機械学会論文集(C編) Vol. 73 ( 727 ) page： 863-870 2007.3

*Self-organized patterning of molecularly thin liquid polymer films utilizing molecular flow induced by ultraviolet irradiation Reviewed Open Access

Hedong Zhang, Yasunaga Mitsuya, Natsuko Fukuoka, Masashi Imamura, Kenji Fukuzawa

Applied Physics Letters Vol. 90 page： 123119(1-3) 2007.3

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

A self-organized patterning method for molecularly thin liquid polymer films on solid surfaces has been demonstrated. In contrast to conventional methods that prepattern solid surfaces and then use the patterns as templates for polymer films, this method utilizes self-organization of polymers induced by ultraviolet (UV) radiation through a mask, thereby directly patterning the polymer films and omitting the prepatterning process. Such UV irradiation locally modified the interaction between polymer films and solid surfaces. As a result, molecular flow occurred at the boundary between the irradiated and nonirradiated areas, leading to three-dimensional surface structures.

DOI： 10.1063/1.2716358