Tunable thick polymer coatings for on-chip electrophoretic protein and peptide separation

► We developed a robust thick wall coating for CE and CEC on chip and capillary. ► Deformation of a monolith resulted in surface coatings with tunable thickness. ► The coating eliminates non-specific protein adsorption and allows control of EOF. ► The coating can be used under acidic and alkaline pH conditions for protein separation. We report a variety of procedures for fabricating confinement-induced polymer coatings, used to eliminate non-specific protein adsorption and to control electroosmotic flow for microchip capillary electrophoresis. The coating strategy generates relatively thick polymer wall coatings (100–700nm) and can easily be tuned by adjusting the monomer concentration. 2-hydroxyethyl methacrylate (HEMA) polymer coating, photopatterned in microfluidic channels, effectively reduced protein non-specific adsorption and rendered high efficiency (N/m=∼3×106) for protein separation. The coating strategy provides rapid and effective means to create robust wall coatings, with the ability to photograft various surface chemistries onto the coating. [2-(methacryloyloxy) ethyl] trimethylammonium chloride grafted HEMA coated channels showed high durability and reproducibility for generating EOF (RSD=2.6%, n=64) over a period of 15 days. Sulfobetaine methacrylate grafted HEMA coated channels allowed separation of BSA digest, 15 peaks resolved in 25s, with an average N/m of 4×105.