Solution and surface composition gradients via microfluidic confinement: Fabrication of a statistical-copolymer-brush composition gradient

A stable solution composition gradient is generated inside a microchannel by varying the relative flow rates of two solutions that differ in composition. This solution gradient is used to synthesize a surface-grafted statistical-copolymer-brush composition gradient via surface-initiated atom transfer radical polymerization (ATRP; see schematic). Near-edge absorption fine structure spectroscopy confirms the continuous transition of surface composition from one end of the substrate to the other.