Thin film diffusion barrier formation in PDMS microcavities

We describe a method to form glass like thin film barrier in polydimethylsiloxane (PDMS) microcavities. The reactive fragments for the surface reaction were created from O₂ and hexamethyldisiloxane (HMDS) in RF plasma environment. The reaction is based on migration of the reactive fragments into the microcavities by diffusion, to form a glass like thin film barrier to conceal the naked surface of PDMS. The barrier successfully blocked penetration of a fluorescent dye rhodamine B (RhB) into PDMS. The thickness of the barrier could be controlled by the time of reaction and the pressure inside the reaction chamber. There is a wide range of applications of such a technique in various fields, e.g. for coating the covered surfaces of microfluidic channels, tubes, capillaries, medical devices, catheters, as well as chip-integrated capillary electrophoresis and advanced electronic and opto-fluidic packaging.