Hedong Zhang 교수

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 performing reactive molecular dynamics simulations with our new ReaxFF force field. By quantifying the decomposition time constants under the operation co

Spreading characteristics of molecularly thin lubricant on a grooved surface have been studied numerically by Monte Carlo simulations and compared with measurements obtained by perfluoropolyether (PFPE) thin film spreading on a solid surface with minute grooves. In the simulations, by incorporating the interactions between molecules and the side surfaces of a groove, the Monte Carlo method based on the Ising model was extended to the case of a surface with grooves and applied to simulate the spr

Organic friction modifiers (OFMs) added to lubricating oils to reduce friction and wear are crucial for reducing energy loss and CO₂ emissions. In our previous studies, we have developed <i>N</i>-(2,2,6,6-tetramethyl-1-oxyl-4-piperidinyl)dodecaneamide, referred to as C₁₂TEMPO, as a new type of OFM and experimentally demonstrated its superior performance to conventional OFMs of stearic acid and glycerol monooleate. However, the behavior of C₁₂TEMPO adsorbing onto

Effects of molecular weight and end-group functionality on spreading of molecularly thin perfluoropolyether (PFPE) film over solid surfaces with groove-shaped textures have been studied by experiments and Monte Carlo simulations. In the experiments, lubricant spreading on a surface with groove-shaped textures was measured by making use of the phenomenon in which diffracted light weakens in the lubricant-covered region. It is found that grooves serve to accelerate spreading and this effect increa

In this paper, we investigate the effect of lube textures from the viewpoint of lubricant spreading. Lube textures, designating a patterned distribution of bonding strength between lubricant molecules and disk surface, were formed by irradiating ultraviolet rays through a stripe-patterned mask onto a magnetic disk surface which was partially coated with one-monolayer film of perfluoropolyether. Surface characteristics of the lube textures were evaluated by surface energies ascertained from conta

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 polym

By measuring force-distance curves with an environmental scanning probe microscope (SPM), we quantitatively evaluated the effect of ultraviolet (UV) irradiation on the adhesive properties of nanometer-thick perfluoropolyether (PFPE) Z03 films coated on magnetic disks. The experimental results indicated that UV irradiation shows negligible influence on the adhesion of the disk surface and on the adhesion of the mobile fraction contained in the UV-irradiated Z03 films. The effect of UV irradiation

Abstract Accurate, non‐invasive, and wearable measurement of arterial pressure pulse waveforms is crucial for cardiovascular healthcare, yet remains challenging due to the lack of effective sensors and mounting methods. This study introduces highly sensitive, flexible PZT piezoelectric sensors and an optimized mounting method for accurate radial pulse waveform measurement in natural wrist positions. The sensors incorporate a PZT thin film directly fabricated on a flexible substrate with easily p