Yoichi Tagaya

Evaluation of Spreading Characteristics of Monolayer Lubricant Films on Magnetic Disks Using Molecular Dynamics Simulation

A coarse-grained molecular dynamics simulation of the spreading of monolayer lubricant films on magnetic disks is presented. The simulated diffusion coefficient for various coverages of the bonded molecules was in good agreement with that obtained by an experiment using the half-dip method. The simulated relation between the coverage and bonding ratio was also in good agreement with the experimental one

Effects of Molecular Conformations and Functional Endgroups on Nanoscale Mobility of Lubricant Molecules on Magnetic Disks

Coarse-grained molecular simulations were applied to polymer lubricant films on magnetic disks for the analysis of head-disk interface (HDI) of hard disk drives (HDDs). Effects of conformation and functional endgroups of the lubricant molecule on the mobility of the lubricant film were observed with the application of molecular viewer which has been developed in this research. It was found that the molecule could not be simplified to a single sphere but should be modeled as a chain of beads connected via springs because the entanglements of the molecules prevented the spreading of the polymer film. Moreover, it was found that the functional endgroups became into clusters

Molecular Dynamics Simulation for Analysis of Surface Morphology of Tri-functional Lubricant Films

Coarse-grained molecular dynamics simulations have been applied to study the effect of polymer functionality on surface morphology of lubricant films. An effective molecular-mesh scanning method was newly introduced to detect the location of film surface. For comparisons, two kinds of double-functional perfluoropolyether (PFPE) Zdol 2000 and Zdol 4000 whose molecular weight was double that of Zdol 2000, and one tri-functional PFPE whose molecular weight was nearly the same as that of Zdol 4000 were selected. We clarified that the film surface of the tri-functional lubricant was smoother than Zdol 2000 when compared at the same film thickness condition

A Simulation Method for Spreading Dynamics of Molecularly Thin Lubricant Films on Magnetic Disks Using Bead-Spring Model

An effective simulation technique for describing the spreading properties of molecularly thin lubricant films on magnetic disks has been developed. We propose a molecular precipitation method that can simulate initial molecule arrangement of the films dip-coated onto the disks. Reptation and Rouse models as the model of the molecular motion, and molecular insertion and molecular precipitation methods as the method for putting molecules in initial positions were compared. From the results of the spreading profiles and diffusion coefficients, it has been revealed that the molecular precipitation method combined with the Rouse model is effective in simulating the spreading of the lubricant films.© 2005 ASME

Numerical model for DNA size separation using nanostructured matrix

Numerical model for DNA separation using nanostructure was proposed. By the model calculation, we can predict the migration time of the molecule that passes through the molecular sieve. In the numerical model, we assumed the DNA molecule to be a sphere with radius Rg, which is a gyration radius, and modeled its Brownian motion by a random walk. Calculation results showed good agreement with those of experiments and we confirmed the validity of the proposed model.

Evaluation of Morphological Properties of Perfluoropolyether Films on Magnetic Disks Using Molecular Dynamics Simulation

Coarse-grained molecular dynamics (MD) simulations were applied to reproduce the surface morphology of lubricant films composed of perfluoropolyether (PFPE) Zdol and tri-functional PFPE, which has a functional group at the middle of a molecule as well as functional endgroups at the head and tail of the molecule. The molecular-mesh scanning method was introduced to detect the location of film surface. The effects of the number of polar groups and polymer length on a flat solid surface were studied as lubricant films with periodic boundary conditions. We clarified that the film surface of the tri-functional PFPE lubricant was smoother than Zdol 2000 when compared at the same film thickness condition.