Kenji Fukuzawa

• Doctor of Engineering
• Professor at Nagoya University

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...

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 d...

To understand the phenomenon in which shear stress increases in nanogaps between mold and substrate surfaces during alignment in ultraviolet (UV) nanoimprinting, we investigate the liquid advancement of UV-curable droplets on modified silicon surfaces. The droplets are pressed with a flat modified surface of a synthetic quartz mold, and the transfo...

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 d...

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 desi...

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 struct...

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 prope...

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, an...

The development of microfabrication and surface machining techniques has made solid surfaces more precise, and the gap dimensions in mechanical systems such as Micro Electro Mechanical Systems and Micro Total Analysis Systems have decreased from the order of micrometers to the order of nanometers. Because the fluid flow properties in nanogaps are d...

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 lubricant...

We established a method for assessing the curing process of a nanometer-thick photocurable liquid film by monitoring changes in shear viscoelasticity at a high temporal resolution. The originally developed nano-rheometry method (the fiber wobbling method) was applied for the viscoelastic measurements. We succeeded in measuring the curing process of...

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 proper...

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...

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 th...

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...

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, whi...

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 probl...

Understanding the formation mechanism and conformation of the adsorbed film formed by additives is critical to clarify the boundary lubrication characteristics. In this study, using the vertical-objective-based ellipsometric microscope (VEM), which can measure nm-gaps between solid surfaces, we proposed a new method for in-situ measuring the thickn...

The growth process of nm-scale polarization domains is of great interest from a physical point of view and is also important in the design of ferroelectric recording, which is expected to be a high-density information recording method. To clarify the growth of nanoscale domains in probe-based ferroelectric recording, a simulation method based on th...

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 coef...

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 f...

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 adsorp...

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 effe...

DNA mapping is a method of stretching random-coiled DNA molecules and then analyzing them using a fluorescence microscope. This method has been used for DNA analyses. In this study, to realize more accurate DNA analyses with small amounts of samples, we aimed to stretch and immobilize λ DNA molecules and to achieve super-resolution imaging with the...

In this study, we proposed a method to measure the escape time of DNA molecules trapped in front of a nanogap by concentrating DNA molecules in front of a nanogap and observing the escape process upon their entry. We measured the escape time for λ DNA molecules entering a 25 nm deep nanogap in the semi-dilute unentangled regime to verify the validi...

To ascertain the effect of transverse dissipative particle dynamics (DPD), which includes lateral dissipative forces in addition to the central ones in the standard DPD, on dynamics of systems involving interfaces, we compare dynamic properties derived from coarse-grained (CG) molecular dynamics simulations with the standard and transverse DPD for...

A thorough understanding of the decomposition of perfluoropolyether (PFPE) lubricants is crucial to achieve heat-assisted magnetic recording (HAMR). In contrast to previous studies, which focused on thermal and catalytic decompositions, we gain insights into the mechano-chemical decomposition of PFPE films confined between the head and disk by perf...

On-chip concentration method for deoxyribonucleic acid (DNA) molecules is preconcentrating DNA molecules before analyses using nanometer-sized structures formed in a microchannel and is effective in improving the sensitivity in DNA analyses using microfluidic devices. Although accurate and predictive theoretical models of concentration profile and...

The optimal molecular design of organic friction modifier (OFM) additives allows for a reduction in the friction and wear in mechanical systems, and thus, an improvement in the energy efficiency and reduction in CO2 emissions. In this study, we synthesized N-(2,2,6,6-tetramethyl-1-oxyl-4-piperidinyl)dodecaneamide, referred to as C12TEMPO, which has...

Measurement of the viscosity of the lubricant in the minute gap is important for elucidating the boundary and mixed lubrication characteristics. It has become clear that the lubricant has a specific viscosity depending on the small gap. Since the viscosity depends on the gap, measurement at a constant (uniform) gap in the measurement region was ess...

To achieve effective lubrication of head-disk interface in heat-assisted magnetic recording (HAMR), mechano-chemical decomposition of nonpolar and polar perfluoropolyether (PFPE) lubricant films, i.e., Z, Z-tetraol, Demnum, and D-4OH, was investigated using reactive molecular dynamics. By fitting with quantum calculation results, the reactive force...

With the development of processing technology, the sliding gap between machine elements has become smaller with the miniaturization of machine elements, and precision mechanical systems down to the nanometer order have also been developed. For the operation of a machine with nano sliding gap, the surface force between machine element surfaces is mo...

Nanopore sequencer is expected as a core technology for realizing medical treatment based on genome information. In order to improve the analysis efficiency, it is necessary to be able to analyze a large molecular size genomic DNA (large molecular weight DNA) with one molecule. Large molecular weight DNA has a random coil structure in a stable stat...

In this study, we stretched and immobilized a 48.5 kbp-DNA molecule using a pressure flow and a gas-liquid interface movement in a microchannel. A chip device with a straight microchannel was fabricated by transfering Si mold created by a photolithography to PDMS. The depth and width of the microchannel were 2 μm and 100 μm, respectively. We contro...

For reading out genomic information from a single molecule of DNA, it is required to establish a DNA extension method that stretches a DNA molecule existing in a random coil state in a solution. To achieve highly stretched DNA molecules, we utilized and experimentally verified the effect of hydrodynamic drag force and electric field gradient in add...

Coarse-grained molecular dynamics simulations were performed to compare the adsorption of organic friction modifier (OFM) added in lubricating oil to flat and corrugated surfaces. Stearic acid, dodecane, and hematite were used as the OFM, lubricating oil, and solid surfaces, respectively. The simulation results showed that the increase in the surfa...

To achieve reliable heat-assisted magnetic recording (HAMR), it is crucial to understand the decomposition of perfluoropolyether (PFPE) lubricant films. In this study, we performed reactive all-atom molecular dynamics simulations to investigate the thermal decomposition of PFPE D-4OH using our original ReaxFF force field. The results showed that th...

2-Methacryloyloxyethyl phosphorylcholine (MPC) polymer is used as coating material on artificial joint for its hydrated lubricity. In order to elucidate the mechanism of the hydrated lubrication, in this research, we measure the shear viscoelasticity of hydrated MPC polymer films by using a fiber wobbling method (FWM). Simultaneously, we measure th...

We improved the performance of a microscopic observation system that has been integrated with a purpose-built pin-on-disk type friction tribotester. This allows us to quantitatively measure the radius and longitudinal depth of deformed region of the sliding pin, and improve the measurement accuracy of the vertical displacement of the sliding pin. A...

On-chip concentration is a method of concentrating biomolecules using a nanometer-sized structure created into a microchannel, which is effective for improving detection sensitivity for microfluidic devices. As an on -chip concentration method for DNA molecules, we proposed a concentration method using nanoslit, which was a gap smaller than a diame...

Using colloid probe atomic force microscopy, we realized accurate measurement of squeeze force generated when the probe approaches a sample surface in liquid. This allows us to quantitatively evaluate slip length of liquids on sample surfaces. We demonstrated that, in contrast to the quartz crystal microbalance method, slip length can be measured r...

A new type of sliding probe for clarifying nano-lubrication phenomena was proposed. In the probe, a small glass sphere was attached with a micro structure for lateral force detection, while a quartz oscillator was used for normal force detection. Although feasibility was demonstrated, repeatability and sensitivity of normal force detection were low...

A method for measuring gap shape during lubrication is presented that uses vertical-objective-type ellipsometric microscopy with two compensator angles. It extends the gap measurement range to over 200 nm and can provide measurement accuracy better than 2 nm for gaps of 0–200 nm without adding any special layer on the sliding surface. Furthermore,...

Correction method for improving the accuracy of gap shape measurement using vertical-objective-type ellipsometric microscopy (VEM) was investigated. This method can provide observation with 0.1-μm-order lateral resolution. Since VEM-based measurement uses an optical microscope with high lateral resolution, the measured ellipsometric signal includes...

Surface force measurement is important for elucidating the interaction between materials on the nano scales. In order to elucidate this, it is essential to quantify the dependency between the surface force and gap between the materials, and it is necessary to precisely control the nano-gap and measure the surface force with high sensitivity. Furthe...

When a DNA molecule passes through a nanochannel which depth is smaller than its size, the molecule is trapped in front of the nanochannel based on an entropy trap. Trapping time τ is a parameter to characterize the entropy trap and measuring trapping time τ accurately is required to design DNA separation and concentration methods based on the entr...

In order to ensure the performance and durability of highly accurate mechanical systems, it is urgent to establish lubrication technology realized in minute gaps. It has been reported that the mechanical properties of lubricating oil in minute gaps narrowed down to nanometer order are completely different from those in the bulk state, and elucidati...

We constructed coarse-grained (CG) models for hematite surfaces, dodecane lubricating oil, and stearic acid additive. Compared with all-atom models, these CG models allow for molecular dynamics (MD) simulations with comparable accuracy and 40 times faster speed. Using the CG models, we performed MD simulations for confined shear of lubricating oil...

Friction force microscopes (FFMs) are widely used for measuring lubrication properties on the nanometer scale. In measurement of lubrication in nanometer gaps, control of the gap between the sliding probe and the sample surface is essential since lubrication properties significantly depends on the size of the gap. In this report, with the aim of re...

In order to ensure the performance and durability of highly accurate mechanical systems, it is urgent to establish lubrication technology realized in minute gaps. It has been reported that the mechanical properties of lubricating oil in minute gaps narrowed down to nanometer order are completely different from those in the bulk state, and measureme...

Lubrication in nanometer-sliding gaps has attracted much interest along with the advance of processing technology. To clarify the lubrication phenomena in nanometer gaps, force measurement under accurate control of the gap between the sliding probe and sample surface is needed because the lubrication properties significantly depend on the gap size....

A thorough understanding of the dynamic behavior of friction modifier additives added to lubricating oil is crucial for improving the performance of boundary lubrication. However, such understanding is still lacking due to difficulty in measurements. In this study, we used coarse-grained (CG) molecular dynamics (MD) simulations to gain insight into...

A high-performance microscopic observation system was developed and integrated with a purpose-built pin-on-disk type tribotester. This allows for simultaneous in situ measurements of the vertical displacement and friction force of a pin sliding on disks lubricated with nanometer-thick liquid films at velocities up to 0.1 m/s, with accuracies of app...

Through electrophoresis driven by a pulsed electric field, we succeeded in separating large DNA molecules with an electrophoretic microchip based on size exclusion chromatography (SEC), which was proposed in our previous study. The conditions of the pulsed electric field required to achieve the separation were determined by numerical analyses using...

A method based on vertical-objective-based ellipsometric microscopy (VEM) is presented for measuring lubricant film thickness in nanometer sliding gaps. It provides an image of nanometer-thick lubricating films in real time at high lateral and thickness resolutions without any special layers. The ellipsometric image is directly converted into the f...

To achieve heat-assisted magnetic recording (HAMR), it is crucial to ensure the reliability and durability of the head–disk interface (HDI) which involves high temperatures, nanoscale spacings, and high shear rates. In this study, we performed all-atom molecular dynamics simulations to understand the phenomenon of lubricant transfer at the HDI of H...

It is known that a lubricant sheared at a nanometer sized gaps has unique mechanical properties (viscoelasticity) different from those in the bulk state. On the other hand, polymer additives are used for lubricating oils to control their temperature characteristics. The influence of the added polymer on the viscoelasticity of lubricating oil in the...

On-chip sample concentration is an effective pretreatment to improve the detection sensitivity of lab-on-a-chip devices for biochemical analysis. In a previous study, we successfully achieved DNA sample concentration using a nanoslit fabricated in the microchannel of a device designed for DNA size separation. The nanoslit was a channel with a depth...

The viscoelasticity of polyalphaolefins confined and sheared in a submicron-to-nanometer-sized gap range was measured. A continuous transition from bulk viscosity to confined viscoelasticity was observed in this gap range. The viscosity increased when the gap was less than around 100 nm, whereas the elasticity rapidly increased when the gap was les...

Using a lateral force microscope with our original dual-axis probe, we measured the friction of molecularly thin films of perfluoropolyether lubricants at low sliding speeds. Merging these results with those measured at high sliding speeds using a home-built pin-on-disk type friction tester, we were able to explore nano-lubrication properties over...

It has been clarified that liquid lubricants confined in nanometer-sized gaps have different mechanical properties from those in bulk state, and it is necessary to consider these effects on lubrication design. In our previous studies, authors have established high-precision nano-rheology measurement method (fiber wobbling method), clarified that un...

Nanoimprint is a technique to fabricate nanoscale patterns by pressing a mold onto a resin material. In particular, nanoimprint lithography (NIL) using UV curable photoresist is expected to improve a process of semiconductor memory manufacturing in the future. During molding, the photoresist is confined in nanometer-sized gaps (nano-gaps) between t...

A new type of sliding probe for clarifying nano-lubrication phenomena is proposed. In the probe, a small glass sphere was attached with a micro structure for force detection. This enabled us to increase the design freedom such as the curvature and material of the sliding surface. In this study, we successfully fabricated the probe and demonstrated...

A high-performance interference microscope was integrated with a previously developed pin-on-disk type friction tester. This allows us to in situ observe the contact region between the pin and disk mediated with nanometer-thick liquid lubricant films, and to measure the sliding-induced vertical displacement of the pin with subnanometer resolution....

To design head disk interface of hard disk drives (HDDs) using heat assisted magnetic recording, it is important to reveal temperature effects on shear properties of nanometer-thick liquid lubricant films. For this purpose, we conducted molecular dynamics simulations of a liquid film of perfluoropolyether which is subjected to confined shear betwee...

Size separation of large DNA molecules (10 kbp – 1000 kbp) is one of the fundamental procedures for identifying bacterium’s genotypes, which should be fast for quick defection of infectious diseases. In our conventional study, we developed an electrophoresis microchip based on size exclusion chromatography. This separation has an advantage that it...

In UV nanoimprint lithography, the viscoelasticity of a photoresist is a dominant factor that affects defect control, throughput, and alignment accuracy, all of which are important for high-volume manufacturing. During the nanoimprint process, the photoresist is confined in nanogaps and nanocavities, between the mold and the substrate. In this stud...

Lubricant transfer or pick-up from a disk to a head slider is a crucial issue in designing the head-disk interfaces of hard disk drives (HDDs). A method is presented for observing thin-lubricant film on a head slider in real time. That is based on ellipsometric microscopy. The use of rotating-compensator ellipsometry (RCE) results in one order of m...

Slip of liquid lubricants on films adsorbed on solid surfaces can largely change friction properties in the boundary or mixed lubrication regime. However, measurement of slip length is challenging owing to its small values on the order of nanometers. For this reason, relationship between slip length and surface characteristics such as surface energ...

The MPC polymer is biocompatible and is used as a coating material for medical instruments such as artificial joints and stents. And it was reported that the MPC polymer thin film of several tens of nm thick coated on the sliding surface of the artificial joint became a hydrated gel with water in the body and has high lubricity. In this study, simu...

Friction force microscopy (FFM) is widely used to clarify tribological properties on the micro and nano scale. On the other hand, lubrication at small gaps has attracted increasing attentions along with the recent progress of precision processing technology. When applying FFM to measurement of properties of lubrication at small gaps, gap control be...

On-chip concentration of samples using nanometer-sized structures fabricated in a microchannel is an effective method to improve detection sensitivity in μTAS. We proposed on-chip concentration of DNA samples using a nano-slit, which is a channel with a depth smaller than a diameter of DNA molecule. The concentration is based on an entropy trap at...

Lubricant transfer or pickup from a disk to head slider is a crucial issue in designing the head-disk interfaces with a reduced head-disk gap. Observation of lubricant on the slider is difficult with the conventional methods due to their limited lateral resolution. In this paper, nanometer-thick lubricant on a slider was observed by using vertical-...

A fundamental understanding of the diffusion phenomena of submonolayer polar liquid films is important for achieving reliable lubrication between moving mechanical parts separated by a nanometer-sized gap. To acquire this understanding, we conducted molecular dynamics (MD) simulations of diffusion phenomena of submonolayer polar perfluoropolyether...

Design principles of lateral-deflection-controlled friction force microscopy (FFM) are presented. Lateral-deflection-controlled FFM can overcome a fundamental problem of dual-axis FFM and can provide higher lateral resolution by compensating for friction force and providing effectively high rigidity to the probe. In this paper, key micro components...

The separation of DNA molecules according to their size represents a fundamental bioanalytical procedure. Here, we report the development of a chip-sized device, consisting of micrometer-sized fence structures fabricated in a microchannel, for the separation of large DNA molecules (over 10 kbp) based on the principle of size exclusion chromatograph...

Anti-stiction coatings for silicon surfaces are a key technology to prevent the failure of nanoelectromechanical systems (NEMS) during operation and improve the forming accuracy in nanoimprint technology. In this study, we propose an atmospheric vapor phase deposition method to coat a silicon surface with fluoropolymers such as the perfluoropolyeth...

Patterning of nanometer-thick liquid lubricant films coated on solid surfaces by masked UV irradiation has been proposed as a method to tailor such properties as depletion and replenishment of the films. In this study, spreading of UV-patterned nanometer-thick polar liquid lubricant films of perfluoropolyether Z DOL was investigated with coarse-gra...

Understanding diffusion flow of nanometer-thick liquid films on solid surfaces is important for many applications and devices. To gain molecular-level insight into such diffusion flow, coarse-grained molecular dynamics (MD) simulations are effective. However, influence of inhomogeneity of coarse-grained solid surfaces on diffusion flow simulations...