Biomedical subjects

Hiroyuki Shinto

Publications and source records attributed to Hiroyuki Shinto.

3 recordsLinked to original sources

PubMed2006

Lateral capillary forces between solid bodies on liquid surface: a lattice Boltzmann study.

When two solid bodies are placed on the surface of a dense liquid under gravitation, they deform the liquid surface to experience a lateral capillary force between themselves that can be attractive and repulsive, depending on the wettabilities and weights of the bodies. In the present study, the lateral capillary force between two square bodies at a liquid-vapor interface has been examined using numerical simulations based on a two-dimensional two-phase lattice Boltzmann (LB) method. The particular situations were simulated, where every body was vertically constrained and had the fixed triple points at its upper or lower corners. Here, the triple point indicates the place at which vapor, liquid, and solid phases meet. The interaction force between these two bodies was calculated as a function of the separation distance, the interfacial tension, and the gravitational acceleration. The simulation results agree well with the analytical expression of the lateral capillary interaction, indicating that our LB method can reproduce the interaction force between two bodies of various wettabilities at a liquid-vapor interface in mechanical equilibrium.

Journal Article↗

PubMed2006

Effects of cleaning procedures of silica wafers on their friction characteristics.

Silicon wafers with thermal silicon oxide layers were cleaned and hydrophilized by three different methods: (1) the remote chemical analysis (RCA) wet cleaning by use of ammonia and hydrogen peroxide mixture solutions, (2) water-vapor plasma cleaning, and (3) UV/ozone combined cleaning. All procedures were found to remove effectively organic contaminations on wafers and gave identical characteristics of the contact angle, the surface roughness and the normal force interactions, measured by atomic force microscopy (AFM). However, it is found that wafers cleaned by the RCA method have several times larger friction coefficients than those cleaned by the plasma and UV/ozone methods. The difference was explained by the atomic-scale topological difference induced during the RCA cleaning. This study reveals the lateral force microscopy as a very sensitive method to detect the microstructure of surfaces.

Journal Article↗

PubMed2005

Revised implicit solvent model for the simulation of surfactants in aqueous solutions.

The implicit solvent model (ISM) proposed previously for the simulation of surfactant aqueous solutions, in which no water molecules of the solvent are treated explicitly, but the effects are incorporated using the solvent-averaged interactions between the surfactant segments in water at infinite dilution, has been revised to represent the surfactant aggregates more appropriately. In the revised model (ISM-2), the interactions between the hydrophobic sites of the surfactants are varied depending on their surroundings, namely, the local hydrocarbon density. The ISM-2 has been applied to the molecular dynamics simulations of (i) the single n-hexane droplets of different sizes in water and (ii) the single micelle composed of 30 n-decyltrimethylammonium chloride (C10TAC) cationic surfactants. As a result, it was found that the ISM-2 can mimic the n-hexane/water interface and represent the fluidity of the hydrocarbon interior of the surfactant micelle that the original ISM fails to do. The results will be compared to those from experiments and atomistic model simulations.

Micelles↗