Papers by Author: Shi Heng Yin

Abstract: In order to improve the surface hydrophilicity and the resistance to protein deposition of fluorosilicone acrylate RGP (rigid gas permeable) contact lens, low temperature ammonia plasma treatment was used to modify the lens surface. The changes of surface structures and properties were characterized by contact angle analyzer, X-ray photoelectron spectroscopy (XPS) and atomic force microscope (AFM). Effects of exposure time and plasma generating power on surface properties of the RGP contact lens were investigated. The surface contact angle measurements showed a great improvement of hydrophilicity after plasma treatment. XPS analysis indicated that the oxygen content and the nitrogen content increased remarkably after ammonia plasma treatment. Furthermore, the content of the hydrophilic group O-C=O/N-C=O on the surface increased and the content of the hydrophobic group CF2 decreased after plasma treatment. AFM results showed that ammonia plasma could lead to surface etching.

Abstract: Oxygen plasma was employed to treat a fluorosilicone acrylate RGP contact lens material (Boston EO) in order to improve surface hydrophilicity. X-ray photoelectron spectroscopy (XPS) was applied to characterize the surface chemical state. The surface morphology and hydrophilicity were investigated by scanning electron microscope (SEM) and contact angle measurement respectively. The surface contact angle measurement indicated an evident improvement of surface hydrophilicity after plasma treatment. XPS results indicated that the incorporation of oxygen and the transform of -Si-CH3 into hydrophilic -Si-O after plasma treatment were the main reasons for surface hydrophilicity improvement. SEM showed some decrease of surface roughness under moderate plasma condition. But plasma with higher power would etch the material surface.

Abstract: The microstructure of scaffold was one of key factors for tissue engineering. Porous polycaprolactone (PCL) scaffolds were fabricated by combination of porogen-leaching and freeze-drying process. Ice particulates were used as porogen material, and PCL solutions in chloroform were mixed with ice particulates for 5minuture at zero temperature. Then the mixture was freezed in liquid nitrogen, and porous scaffold was prepared by freeze - drying finally. The microstructure and properties of the scaffolds were investigated. Porous structure of the scaffolds showed that good 3D microstructure and no porogen remained in the scaffold; pore size and porosity were determined by the size and mass fraction of ice particulates. The results demonstrated that the Scaffolds possessed open and interconnected pores with sizes ranging from several μm to more than 300μm and porosities of 50~80%.

Abstract: In this study, biomemitic hydroxyapatite was prepared as a nano-sized powder from calcium nitrate tetrahydrate and diammonium hydrogen phosphate salts, but using the different contents of PVP modified hydroxyapatite and synthetic body fluid (SBF) solutions as synthesis medium instead of pure water at 37.4C and pH of 7.4. SBF was prepared in accord with the chemical analysis of human body fluid, with ion concentrations nearly equal to those of the inorganic constituents of human blood plasma. Characterization and chemical analaysis of the synthesized biomemitic hydroxyapatite powders and pure hydroxyapatite were investigated by X-ray powder diffraction, scanning electron microscopy, and inductively coupled plasma atomic emission spectroscopy. Rheological properties of HAP sol which reflected the interaction of hydroxyapatite particles were measured by R/S rheometer. The results showed that PVP evidently affected the stability and rheological properties of HAP sol, and PVP were based on the different mechanism at different concentrations. PVP was operating as an interparticle bridging reagent at low concentrations(0.5%), while it acted as an dispersant at high concentrations(2.0%). The biomemitic hydroxyapatite with the sizes of 10~30nm was spherical and poor crystalline, which was synthesized in synthetic body fluid (SBF) by addition of 2.0% PVP.