Surface Modification of Fluoro-silicone Acrylate Polymers by Pulse-modulated Microwave Air Plasma Jet

Fluoro-silicone acrylate polymers are the main material for orthokeratology lenses, which are used for adolescent vision correction. Currently, the lenses are maintained by surface treatment of argon plasma jet for wearing comfort, sterilization and cleaning. In order to increase the content of reactive species and the convenience of plasma device, this paper attempts to apply air microwave air plasma jet to treat the lenses. To avoid the thermal damage to the lenses caused by air discharge, the pulse modulation technique is utilized to reduce the gas temperature. The discharge images, jet lengths, optical emission spectra and gas temperatures of the air plasma jet under different operation parameters, like microwave incident powers, gas flow rates and duty cycles are studied experimentally. The results show that the plasma jet has the best overall performances under $90 \mathrm{~W}, 9$ sIm and 0.5. The surface physical and chemical properties of the virgin and modified lenses are evaluated by the water contact angles (WCAs), the surface morphologies and the chemical compositions. The lenses show the lowest WCA under the treatment time of 60 s. The mechanism on the surface modification of lenses is discussed. The graft of polar groups is considered as the main reason for the decrease of WCA.