Title: Polymer surface modification by excimer radiation

Abstract: Surface modification of polymer substrates is typically achieved by “wet- chemical” treatments that involve a number of time-consuming steps. Previously we investigated the ability to pattern polymer substrates via laser ablation under different chemical atmospheres. In this one-step process, polymers were micro-machined while simultaneously chemically modifying the surface. As an extension of this research, we have exposed various polymer substrates to narrow band excimer radiation under inert atmospheres and the resultant surface is characterized by attenuated total reflectance infrared spectroscopy, contact angle goniometry, atomic force microscopy, and scanning electron microscopy. Finally, some of the polymer substrates as characterized by electroosmotic flow. In this presentation, the modification of polydimethylsiloxane and polymethylmethacrylate will be discussed. The modification of polydimethylsiloxane (PDMS) by narrow band 254 nm excimer radiation under a nitrogen atmosphere is characterized and it is determined that the UV irradiation results in the formation of the carboxylic acids that influences the wettability of the surface. Continued exposure results in the formation of an inorganic surface (SiOx, (1 < x < 2)) which hinders the ability to continually increase the wettability. These results have implications in the fabrication and chemical modification of microfluidic or micro-electro-mechanical systems. The application in microfluidics is observed with the modification of PMMA by 222 nm excimer radiation that results in the formation of hydroxyl groups which in turn contribute to increased electroosmotic flow.