Tunable thick polymer coatings for on-chip electrophoretic protein and peptide 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 (100–700 nm) 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 25 s, with an average N/m of 4 × 105.