A simple method to generate solution gradients through microfluidic confinement is described. The solution gradient inside a microchannel was formed by varying the relative infusion rates of two solutions that differed in compositions. The establishment and maintenance of a stable solution gradient in a microchannel was confirmed using the Raman spectroscopy. The stable solution gradient was explored to synthesize a surface-grafted statistical copolymer brush gradient of n-butyl methacrylate (BMA) and 2-(dimethylamino)ethyl methacrylate (DMAEMA) via surface-initiated atom transfer radical polymerization (ATRP). The resulting gradient exhibits a surface energy change from the homopolymer brush of BMA to that of DMAEMA, as indicated by water contact angle measurement. Further evidence from near-edge absorption fine structure (NEXAFS) spectroscopy confirmed the gradual transition of surface composition from one end of the substrate to the other.
Citation: Advanced Materials
Pub Type: Journals
ATRP, copolymer brushes, gradient thin films, microfluid