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KMID : 1159320130150020189
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Korean Journal of Vision Science
2013 Volume.15 No. 2 p.189 ~ p.200
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Effect of Surface Plasma Treatment on Physicochemical Characteristics of Rigid Gas Permeable Contact Lens
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Lee Kyoung-Nam
Shin Hyung-Sup
Jeon In-Chul
Mah Ki-Choong
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Abstract
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Purpose: To analyze the effect of plasma surface treatment on the physicochemical properties of various fluorosilicone acrylate-based rigid gas permeable (RGP) contact lenses. Methods: Plasma treatment of the RGP lens surfaces was performed at room temperature using a power of 200W. Lenses were treated for varying durations from 0~250 seconds. In order to determine wettability of the lens surface, the contact angle was measured. Surface composition was observed using X-ray photoelectron spectroscopy(XPS), and the formation of hydrophilic silica-like structures were measured. Surface morphology and roughness were observed using atomic force microscopy(AFM). Change in oxygen permeability (Dk) was compared using polarography and center thickness measurements. Results: Following plasma surface treatment, the wetting angle decreased sharply in the initial stage and decreased up to 30% compared to untreated surfaces. The carbon and fluorine contents to below 70 at. % (atomic percent); however, oxygen and silicone contents increased to above 150 at. % on the surface. The decrease in surface carbon correlates directly with the decrease in the contact angle. Plasma surface treatments caused carbon and fluorine on the surface to become volatile. Subsequently, extricated silicon and oxygen combined at the surface to form hydrophilic silicate (SiOx, x=1.5~2.0)-increasing the overall amount of silicate bonds by over 50 at. %. Circular or rectangular projections were observed on plasma-treated surface, and roughness (RMS) increased by over 40%. Conclusions: When RGP contact lenses were treated with plasma in the air, hydrophilic silicate was formed on the surface-improving wettability but without affecting oxygen permeability. It is considered that the increase in wettability was influenced more by the formation of silicate than by a change in surface morphology. Also, it is considered that the changes in oxygen permeability is not significant because silicate, which formed limitedly on the surface by plasma treatment, has an open structure.
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KEYWORD
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RGP contact lens, Wettability, Surface plasma treatment, Silicate, Oxygen permeability
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