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Y. Huo, S. S. Perry, A. Rygalov, A. Wang, H. A. Ketelson, D. L. Meadows; Chemical and Frictional Analysis of Silicone Hydrogel Lens Surfaces. Invest. Ophthalmol. Vis. Sci. 2010;51(13):3422.
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Chemical analysis of the outermost layers of hydrogel lenses has been conducted with X-ray photoelectron spectroscopy (XPS) in order to assess the fundamental nature of molecular interactions occurring at lens interfaces.
Lens surfaces have been prepared through a vacuum drying procedure, in which the hydrogel is taken from a fully hydrated state directly to an ultraclean, ultrahigh vacuum environment. The lenses used were Biofinity*, Acuvue* 2*, Acuvue* OASYS*, O2OPTIX*, and PureVision*.
Analysis of the photoelectron spectra of the five lenses revealed the presence of carbon, nitrogen, oxygen, and silicon in various concentrations for all lenses and small amounts of either fluorine and chlorine in two cases. For example, oxygen surface concentrations ranged from 16.5 to 26.2 atomic percent, while silicon varied from 1.2 to 11.7 atomic percent. Detailed core level analysis further permitted the assessment of the chemical state of carbon species found at the surface in terms of their local bonding environment (hydrophilic character). The compositional data have also been compared to analogous measurements of lens surfaces following exposure to a new class of diblock copolymer specifically designed to tailor the hydrophilicity of lens surfaces.
Together, these data represent the basis of interpreting differences in interfacial friction measured between the hydrogel surface and a silica colloidal probe with scanning probe microscopy.*Trademarks are the properties of their respective owners.
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